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Journal of Prosthetic Dentistry

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

      Abstract

      The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2020 professional literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to this work to cover this broad topic. Specific subject areas addressed include prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders (TMDs); sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence day-to-day dental treatment decisions with a keen eye on future trends in the profession. With the tremendous volume of dentistry and related literature being published today, this review cannot possibly be comprehensive. The purpose is to update interested readers and provide important resource material for those interested in pursuing greater detail. It remains our intent to assist colleagues in navigating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the dental patients they encounter.

      Prosthodontics

      The 2020 professional literature pertinent to the clinical practice of prosthodontics was again substantial. Critically selected articles from well over 50 professional journals were included in this prosthodontics review to update readers in this increasingly broad area of restorative dentistry. For convenience, this extensive subject has been divided into 8 specific topics: general prosthodontic considerations, conventional complete dentures, conventional removable partial dentures, conventional fixed prosthodontics, general implant prosthodontic considerations, implant removable prosthodontics, implant fixed prosthodontics, and prosthodontic materials.
      There were 3 interesting and important publications that will be mentioned, but not extensively reviewed here because they lie beyond the scope of this work. However, their consideration is strongly recommended for interested readers.
      The first of these publications was the updated version of the Parameters of Care for the Specialty of Prosthodontics.
      Parameters of care for the specialty of prosthodontics.
      Authored by several key committees of the American College of Prosthodontists, this lengthy and highly referenced work is intended to help improve clinical care; establish prosthodontic consensus; and inform risk management, education, testing and the appropriateness of third-party involvement in clinical care. These parameters provide both a foundation of information and then a broad framework to guide predictable and favorable treatment outcomes.
      In the second important publication, Praveen et al
      • Praveen G.
      • Chaithanya R.
      • Alla R.K.
      • Shammas M.
      • Abdurahiman V.T.
      • Anitha A.
      The 100 most cited articles in prosthodontic journals: a bibliometric analysis of articles published between 1951 and 2019.
      reported on a bibliometric study that aimed to determine the characteristics of the 100 most cited articles in prosthodontic journals between 1951 and 2019. The top 5 most cited articles in prosthodontic journal over this time period were written by Brånemark
      • Brånemark P.I.
      Osseointegration and its experimental background.
      (2368 citations), Humphrey and Williamson
      • Humphrey S.P.
      • Williamson R.T.
      A review of saliva: normal composition, flow, and function.
      (1444 citations), Eriksson and Albrektsson
      • Eriksson A.R.
      • Albrektsson T.
      Temperature threshold levels for heat-induced bone tissue injury: a vital-microscopic study in the rabbit.
      (1297 citations), Tallgren
      • Tallgren A.
      The continuing reduction of the residual alveolar ridges in complete denture wearers: a mixed-longitudinal study covering 25 years.
      (1228 citations), and Goodacre et al
      • Goodacre C.J.
      • Bernal G.
      • Rungcharassaeng K.
      • Kan J.Y.
      Clinical complications with implants and implant prostheses.
      (1054 citations). Majority of the articles cited were originally published in the Journal of Prosthetic Dentistry (72 articles), International Journal of Prosthodontics (25 articles), Journal of Prosthodontics (2 articles), and Journal of Prosthodontic Research (1 article). The decade in which most articles were published was the 1990s (33 articles). Many of the authors of the most cited articles were from the United States (55 articles) or Sweden (12 articles), with T. Albrektsson (7 articles) and G.A. Zarb (6 articles) listed most often. The top 100 articles tended to be reviews (35 articles) or experimental studies (34 articles), most commonly addressing dental implants (27 articles) or composite resins and ceramics (21 articles).
      The authors concluded that although the article listing described is not a direct measure of quality or importance, it may shed light on a quantitative evaluation of scientific impact. Additionally, the 100 most cited articles in prosthodontics may provide insights into advances, areas of intense research, and future objectives in the field.
      While spin in pop journalism is routine, even expected, one might believe that spin should have no place in scientific and/or clinical publications. Not so says Roszhart et al
      • Roszhart J.I.
      • Kumar S.S.
      • Allareddy V.
      • Childs C.A.
      • Elangovan S.
      Spin in abstracts of randomized controlled trials in dentistry: a cross-sectional analysis.
      who assessed the prevalence of spin in abstracts from published randomized controlled trials (RCTs) and explored potential influences.
      A systematic search of 2015 publications in top 10 dental journals (based on 2016 Eigenfactor score) was conducted to select RCTs that resulted in statistically nonsignificant primary outcomes. Seventy-five articles were identified. The disciplines involved included general dentistry, dental research, implant dentistry, endodontics, oral surgery, periodontics, and oral oncology. Within the published abstracts, there were 3 different categories of spin and factors that could influence its presence. The 3 spin categories included (1) concluding clinical significance in spite of statistical nonsignificance; (2) interpreting statistically nonsignificant as indicating treatment equivalence or comparable effectiveness; and (3) emphasizing statistically significant secondary outcomes and omitting primary outcomes.
      Based on the 75 RCTs identified, the authors concluded that 48% had a statistically nonsignificant result for the primary outcome with some form of spin in at least 31% of the accompanying published abstracts. No significant associations were found between spin parameters and journal impact factor, funding type, number of treatment arms, or presence of international collaborations. The authors emphasized the importance of careful appraisal of both the abstract and full text of the publication before adoption of recommendations into clinical practice. While readers should certainly practice caution in this manner, journal editorial boards must carefully control their peer review process to prohibit misleading statistical inferences and unfounded conclusions.
      In addition to articles selected for detailed review, a sizable number of excellent general reviews, systematic reviews, meta-analyses, and helpful clinical descriptive articles were also published addressing issues important to prosthodontics. Although it is impractical to provide detailed analysis on all these publications, they are listed here, by topic area, for the reader’s convenience: anatomy and physiology,
      • Braud A.
      • Boucher Y.
      Intra-oral trigeminal-mediated sensations influencing taste perception: a systematic review.
      • Chung M.K.
      • Wang S.
      • Yang J.
      • Alshanqiti I.
      • Wei F.
      • Ro J.Y.
      Neural pathways of craniofacial muscle pain: Implications for novel treatments.
      • Lin C.S.
      • Yeung A.W.K.
      What do we learn from brain imaging?–A primer for the dentists who want to know more about the association between the brain and human stomatognathic functions.
      • Lin J.D.
      • Ryder M.
      • Kang M.
      • Ho S.P.
      Biomechanical pathways of dentoalveolar fibrous joints in health and disease.
      • Roberts W.E.
      • Goodacre C.J.
      The temporomandibular joint: a critical review of life-support functions, development, articular surfaces, biomechanics and degeneration.
      • Rosero Salazar D.H.
      • Carvajal Monroy P.L.
      • Wagener F.A.D.T.G.
      • Von den Hoff J.W.
      Orofacial muscles: embryonic development and regeneration after injury.
      bone augmentation,
      • Xu J.
      • Gou L.
      • Zhang P.
      • Li H.
      • Qiu S.
      Platelet-rich plasma and regenerative dentistry.
      bruxism,
      • Ågren M.
      • Sahin C.
      • Pettersson M.
      The effect of botulinum toxin injections on bruxism: a systematic review.
      ,
      • Duarte J.
      • Pauletto P.
      • Massignan C.
      • Bolan M.
      • Domingos F.L.
      • Hallal A.L.C.
      • et al.
      Association between sleep bruxism and quality of life: a systematic review.
      caries,
      • Eidt G.
      • Waltermann E.D.M.
      • Hilgert J.B.
      • Arthur R.A.
      Candida and dental caries in children, adolescents and adults: a systematic review and meta-analysis.
      • Hancock S.
      • Zinn C.
      • Schofield G.
      The consumption of processed sugar- and starch-containing foods, and dental caries: a systematic review.
      • Hayashi M.
      • Momoi Y.
      • Fujitani M.
      • Fukushima M.
      • Imazato S.
      • Kitasako Y.
      • et al.
      Evidence-based consensus for treating incipient enamel caries in adults by non-invasive methods: recommendations by GRADE guideline.
      • Shimada Y.
      • Yoshiyama M.
      • Tagami J.
      • Sumi Y.
      Evaluation of dental caries, tooth crack, and age-related changes in tooth structure using optical coherence tomography.
      • Söderling E.
      • Pienihäkkinen K.
      Effects of xylitol and erythritol consumption on mutans streptococci and the oral microbiota: a systematic review.
      • Zhang J.
      • Sardana D.
      • Li K.Y.
      • Leung K.C.M.
      • Lo E.C.M.
      Topical fluoride to prevent root caries: Systematic review with network meta-analysis.
      conventional complete dentures,
      • Goodacre C.J.
      • Naylor W.P.
      Evolution of the temperament theory and mental attitude in complete denture prosthodontics: from Hippocrates to M.M. House.
      ,
      • Muddugangadhar B.C.
      • Mawani D.P.
      • Das A.
      • Mukhopadhyay A.
      Bond strength of soft liners to denture base resins and the influence of different surface treatments and thermocycling: a systematic review.
      conventional fixed prosthodontics,
      • Batista V.E.S.
      • Bitencourt S.B.
      • Bastos N.A.
      • Pellizzer E.P.
      • Goiato M.C.
      • Dos Santos D.M.
      Influence of the ferrule effect on the failure of fiber-reinforced composite post-and-core restorations: a systematic review and meta-analysis.
      • Bousnaki M.
      • Chatziparaskeva M.
      • Bakopoulou A.
      • Pissiotis A.
      • Koidis P.
      Variables affecting the fit of zirconia fixed partial dentures: a systematic review.
      • Mai H.Y.
      • Lee W.K.
      • Kwon T.G.
      • Lee D.H.
      Reliability of digital measurement methods on the marginal fit of fixed prostheses: a systematic review and meta-analysis of in vitro studies.
      • Miura S.
      • Fujisawa M.
      Current status and perspective of CAD/CAM-produced resin composite crowns: a review of clinical effectiveness.
      • Sousa S.J.L.
      • Poubel D.L.D.N.
      • Rezende L.V.M.L.
      • Almeida F.T.
      • de Toledo I.P.
      • Garcia F.C.P.
      Early clinical performance of resin cements in glass-ceramic posterior restorations in adult vital teeth: a systematic review and meta-analysis.
      conventional removable partial dentures,
      • Almufleh B.
      • Emami E.
      • Alesawy A.
      • Rodan R.
      • Morris M.
      • Umebayashi M.
      • et al.
      Patient-reported outcomes of metal and acrylic resin removable partial dentures: a systematic review and meta-analysis.
      ,
      • Seo J.G.
      • Cho J.H.
      Clinical outcomes of rigid and non-rigid telescopic double-crown-retained removable dental prostheses: an analytical review.
      COVID-19,
      • Fernandes L.L.
      • Pacheco V.B.
      • Borges L.
      • Athwal H.K.
      • de Paula Eduardo F.
      • Bezinelli L.
      • et al.
      Saliva in the diagnosis of COVID-19: a review and new research directions.
      ,
      • Samaranayake L.P.
      • Fakhruddin K.S.
      • Panduwawala C.
      Sudden onset, acute loss of taste and smell in coronavirus disease 2019 (COVID-19): a systematic review.
      dental hygiene,
      • Clark-Perry D.
      • Levin L.
      Systematic review and meta-analysis of randomized controlled studies comparing oscillating-rotating and other powered toothbrushes.
      • Martins C.C.
      • Firmino R.T.
      • Riva J.J.
      • Ge L.
      • Carrasco-Labra A.
      • Brignardello-Petersen R.
      • et al.
      Desensitizing toothpastes for dentin hypersensitivity: a network meta-analysis.
      • Wang P.
      • Xu Y.
      • Zhang J.
      • Chen X.
      • Liang W.
      • Liu X.
      • et al.
      Comparison of the effectiveness between power toothbrushes and manual toothbrushes for oral health: a systematic review and meta-analysis.
      dental microbiology,
      • Balachandran M.
      • Cross K.L.
      • Podar M.
      Single-cell genomics and the oral microbiome.
      • Carpenter G.H.
      Salivary factors that maintain the normal oral commensal microflora.
      • Curtis M.A.
      • Diaz P.I.
      • Van Dyke T.E.
      The role of the microbiota in periodontal disease.
      • Diaz P.I.
      • Valm A.M.
      Microbial interactions in oral communities mediate emergent biofilm properties.
      • Kitamoto S.
      • Nagao-Kitamoto H.
      • Hein R.
      • Schmidt T.M.
      • Kamada N.
      The bacterial connection between the oral cavity and the gut diseases.
      • Sasaki J.I.
      • Imazato S.
      Autoclave sterilization of dental handpieces: a literature review.
      • Wade W.G.
      • Prosdocimi E.M.
      Profiling of oral bacterial communities.
      dental occlusion,
      • Imhoff B.
      • Ahlers M.O.
      • Hugger A.
      • Lange M.
      • Schmitter M.
      • Ottl P.
      • et al.
      Occlusal dysesthesia-A clinical guideline.
      ,
      • Mehl A.
      Digital technologies for functional diagnosis and treatment.
      dental wear,
      • Zanatta R.F.
      • Caneppele T.M.F.
      • Scaramucci T.
      • El Dib R.
      • Maia L.C.
      • Ferreira D.M.T.P.
      • et al.
      Protective effect of fluorides on erosion and erosion/abrasion in enamel: a systematic review and meta-analysis of randomized in situ trials.
      digital dentistry,
      • Kessler A.
      • Hickel R.
      • Reymus M.
      3D Printing in dentistry-State of the art.
      • Leeson D.
      The digital factory in both the modern dental lab and clinic.
      • Plaster U.
      Synchronization of patient study models in the articulator. Part 2. Occlusal plane and maxillomandibular relationship: transferring analog information to the digital world.
      • Rekow E.D.
      Digital dentistry: the new state of the art-Is it disruptive or destructive?.
      • Rungrojwittayakul O.
      • Kan J.Y.
      • Shiozaki K.
      • Swamidass R.S.
      • Goodacre B.J.
      • Goodacre C.J.
      • et al.
      Accuracy of 3D printed models created by two technologies of printers with different designs of model base.
      • Vandenberghe B.
      The crucial role of imaging in digital dentistry.
      emerging technology,
      • Chen Y.W.
      • Stanley K.
      • Att W.
      Artificial intelligence in dentistry: current applications and future perspectives.
      • Faggion Jr., C.M.
      The (in)adequacy of translational research in dentistry.
      • Grischke J.
      • Johannsmeier L.
      • Eich L.
      • Griga L.
      • Haddadin S.
      Dentronics: towards robotics and artificial intelligence in dentistry.
      • Ilhan B.
      • Lin K.
      • Guneri P.
      • Wilder-Smith P.
      Improving oral cancer outcomes with imaging and artificial intelligence.
      • Refai A.K.
      • Cochran D.L.
      Harnessing omics sciences and biotechnologies in understanding osseointegration–Personalized dental implant therapy.
      • Revilla-León M.
      • Sadeghpour M.
      • Özcan M.
      A review of the applications of additive manufacturing technologies used to fabricate metals in implant dentistry.
      • Schwendicke F.
      • Samek W.
      • Krois J.
      Artificial intelligence in dentistry: chances and challenges.
      • Takeuchi Y.
      • Tanaka M.
      • Tanaka J.
      • Kamimoto A.
      • Furuchi M.
      • Imai H.
      Fabrication systems for restorations and fixed dental prostheses made of titanium and titanium alloys.
      endo-restorative dentistry,
      • Jazayeri H.E.
      • Lee S.M.
      • Kuhn L.
      • Fahimipour F.
      • Tahriri M.
      • Tayebi L.
      Polymeric scaffolds for dental pulp tissue engineering: a review.
      ,
      • Martins J.N.R.
      • Marques D.
      • Silva E.J.N.L.
      • Caramês J.
      • Mata A.
      • Versiani M.A.
      Second mesiobuccal root canal in maxillary molars – A systematic review and meta-analysis of prevalence studies using cone beam computed tomography.
      esthetics,
      • Devila A.
      • Lasta R.
      • Zanella L.
      • Agnol M.D.
      • Rodrigues-Junior S.A.
      Efficacy and adverse effects of whitening dentifrices compared with other products: a systematic review and meta-analysis.
      • Dym H.
      • Pierre 2nd, R.
      Diagnosis and treatment approaches to a “gummy smile”.
      • Finkel S.
      • Pizzi P.
      Dentist-ceramist communication: protocols for an effective esthetic team.
      • Pontes M.
      • Gomes J.
      • Lemos C.
      • Leão R.S.
      • Moraes S.
      • Vasconcelos B.
      • et al.
      Effect of bleaching gel concentration on tooth color and sensitivity: a systematic review and meta-analysis.
      • Tran Cao P.
      The use of botulinum toxin and dermal fillers to enhance patients’ perceived attractiveness: implications for the future of aesthetic dentistry.
      evidence-based dentistry,
      • Chiang H.S.
      • Tsai Y.C.
      • Huang R.Y.
      • Weng P.W.
      • Mau L.P.
      • Nguyen T.T.
      • et al.
      Citation characteristics of h-classics articles in implant dentistry: a citation analysis using h-classics method.
      • Delli K.
      • Livas C.
      • Dijkstra P.U.
      How has the dental literature evolved over time? Analyzing 20 years of journal self-citation rates and impact factors.
      • Gogos C.
      • Kodonas K.
      • Fardi A.
      • Economides N.
      Top 100 cited systematic reviews and meta-analyses in dentistry.
      • Neuppmann Feres M.F.
      • Roscoe M.G.
      • Job S.A.
      • Mamani J.B.
      • Canto G.L.
      • Flores-Mir C.
      Barriers involved in the application of evidence-based dentistry principles: a systematic review.
      • Qin D.
      • Hua F.
      • He H.
      • Liang S.
      • Worthington H.
      • Walsh T.
      Quality of split-mouth trials in dentistry: 1998, 2008, and 2018.
      • Wu X.
      • Hu Q.
      • Yan Q.
      • Zhang T.
      • Riley P.
      • Hua F.
      • et al.
      Trends in the level of evidence and impact of clinical studies published in leading oral implantology journals: 2008-2018.
      geriatric dentistry,
      • Al-Nasser L.
      • Lamster I.B.
      Prevention and management of periodontal diseases and dental caries in the older adults.
      ,
      • Chen R.
      • Irving M.
      • Clive Wright F.A.
      • Cunich M.
      An evaluation of health workforce models addressing oral health in residential aged care facilities: a systematic review of the literature.
      implant complications,
      • Berlin-Broner Y.
      • Levin L.
      Dental implant success and endodontic condition of adjacent teeth: a systematic review.
      • Bidra A.S.
      • Kejriwal S.
      • Bhuse K.
      Should healing abutments and cover screws for dental implants be reused? A systematic review.
      • Gaddale R.
      • Mishra S.K.
      • Chowdhary R.
      Complications of screw- and cement-retained implant-supported full-arch restorations: a systematic review and meta-analysis.
      • Omori Y.
      • Lang N.P.
      • Botticelli D.
      • Papageorgiou S.N.
      • Baba S.
      Biological and mechanical complications of angulated abutments connected to fixed dental prostheses: a systematic review with meta-analysis.
      implant esthetics,
      • Aizcorbe-Vicente J.
      • Peñarrocha-Oltra D.
      • Canullo L.
      • Soto-Peñaloza D.
      • Peñarrocha-Diago M.
      Influence of facial bone thickness after implant placement into the healed ridges on the remodeled facial bone and considering soft tissue recession: a systematic review.
      • Chu S.J.
      • Kan J.Y.
      • Lee E.A.
      • Lin G.H.
      • Jahangiri L.
      • Nevins M.
      • et al.
      Restorative emergence profile for single-tooth implants in healthy periodontal patients: clinical guidelines and decision-making strategies.
      • Pitta J.
      • Zarauz C.
      • Pjetursson B.
      • Sailer I.
      • Liu X.
      • Pradies G.
      A systematic review and meta-analysis of the influence of abutment material on peri-implant soft tissue color measured using spectrophotometry.
      • Zarauz C.
      • Pitta J.
      • Pradies G.
      • Sailer I.
      Clinical recommendations for implant abutment selection for single-implant reconstructions: customized vs standardized ceramic and metallic solutions.
      implant fixed prosthodontics,
      • Alsabeeha N.H.
      • Atieh M.A.
      Outcomes and complication rates of the tooth-implant-supported fixed prosthesis: a systematic review and meta-analysis.
      • Carneiro-Campos L.E.
      • Freitas-Fernandes L.B.
      • Masterson D.
      • Magno M.B.
      • Fernandes C.P.
      • Maia L.C.
      • et al.
      Does the natural maxillary dentition influence the survival rate of mandibular metal-resin implant-supported fixed complete dentures? A systematic review and meta-analysis.
      • Cheng Q.
      • Su Y.Y.
      • Wang X.
      • Chen S.
      Clinical outcomes following immediate loading of single-tooth implants in the esthetic zone: a systematic review and meta-analysis.
      • Hu M.L.
      • Lin H.
      • Zhang Y.D.
      • Han J.M.
      Comparison of technical, biological, and esthetic parameters of ceramic and metal-ceramic implant-supported fixed dental prostheses: a systematic review and meta-analysis.
      implant removable prosthodontics,
      • Gonçalves F.
      • Campestrini V.L.L.
      • Rigo-Rodrigues M.A.
      • Zanardi P.R.
      Effect of the attachment system on the biomechanical and clinical performance of overdentures: a systematic review.
      ,
      • Padmanabhan H.
      • Kumar S.M.
      • Kumar V.A.
      Single implant retained overdenture treatment protocol: a systematic review and meta-analysis.
      implant surgery,
      • Al-Moraissi E.A.
      • Oginni F.O.
      • Mahyoub Holkom M.A.
      • Mohamed A.A.S.
      • Al-Sharani H.M.
      Tissue-engineered bone using mesenchymal stem cells versus conventional bone grafts in the regeneration of maxillary alveolar bone: a systematic review and meta-analysis.
      • Ikar M.
      • Grobecker-Karl T.
      • Karl M.
      • Steiner C.
      Mechanical stress during implant surgery and its effects on marginal bone: A literature review.
      • Khehra A.
      • Levin L.
      Maxillary sinus augmentation procedures: a narrative clinical review.
      • Li X.
      • Lin X.
      • Guo J.
      • Wang Y.
      The stability and survival rate of dental implants after preparation of the site by piezosurgery vs conventional drilling: a systematic review and meta-analysis.
      • Naeini E.N.
      • Atashkadeh M.
      • De Bruyn H.
      • D'Haese J.
      Narrative review regarding the applicability, accuracy, and clinical outcome of flapless implant surgery with or without computer guidance.
      • Siqueira R.
      • Chen Z.
      • Galli M.
      • Saleh I.
      • Wang H.L.
      • Chan H.L.
      Does a fully digital workflow improve the accuracy of computer-assisted implant surgery in partially edentulous patients? A systematic review of clinical trials.
      • Stacchi C.
      • Troiano G.
      • Rapani A.
      • Berton F.
      • Lombardi T.
      • Rapani A.
      • et al.
      Piezoelectric bone surgery for implant site preparation compared with conventional drilling techniques: a systematic review, meta-analysis and trial sequential analysis.
      implant treatment planning,
      • de Oliveira Limírio JPJ
      • Lemos C.A.A.
      • de Luna Gomes J.M.
      • Minatel L.
      • Alves Rezende M.C.R.
      • Pellizzer E.P.
      A clinical comparison of 1-piece versus 2-piece implants: a systematic review and meta-analysis.
      • Heiderich C.M.C.
      • Tedesco T.K.
      • Netto S.S.
      • de Sousa R.C.
      • Allegrini Júnior S.
      • Mendes F.M.
      • et al.
      Methodological quality and risk of bias of systematic reviews about loading time of multiple dental implants in totally or partially edentulous patients: an umbrella systematic review.
      • Oh S.L.
      • Shiau H.J.
      • Reynolds M.A.
      Survival of dental implants at sites after implant failure: a systematic review.
      • Rosenstein J.
      • Dym H.
      Zygomatic implants: a solution for the atrophic maxilla.
      • Saito H.
      • Aichelmann-Reidy M.B.
      • Oates T.W.
      Advances in implant therapy in North America: improved outcomes and application in the compromised dentition.
      impressions,
      • Giachetti L.
      • Sarti C.
      • Cinelli F.
      • Russo D.S.
      Accuracy of digital impressions in fixed prosthodontics: a systematic review of clinical studies.
      • Kihara H.
      • Hatakeyama W.
      • Komine F.
      • Takafuji K.
      • Takahashi T.
      • Yokota J.
      • et al.
      Accuracy and practicality of intraoral scanner in dentistry: a literature review.
      • Papaspyridakos P.
      • Vazouras K.
      • Chen Y.W.
      • Kotina E.
      • Natto Z.
      • Kang K.
      • et al.
      Digital vs conventional implant impressions: a systematic review and meta-analysis.
      • Wulfman C.
      • Naveau A.
      • Rignon-Bret C.
      Digital scanning for complete-arch implant-supported restorations: a systematic review.
      material science,
      • Ajiboye A.S.
      • Mossey P.A.
      • Fox C.H.
      IADR Science Information Committee
      International Association for Dental Research policy and position statements on the safety of dental amalgam.
      • Althaqafi K.A.
      • Satterthwaite J.
      • Silikas N.
      A review and current state of autonomic self-healing microcapsules-based dental resin composites.
      • Bangera M.K.
      • Kotian R N.R.
      Effect of titanium dioxide nanoparticle reinforcement on flexural strength of denture base resin: a systematic review and meta-analysis.
      • Cuevas-Suárez C.E.
      • de Oliveira da Rosa W.L.
      • Vitti R.P.
      • da Silva A.F.
      • Piva E.
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      The role of inflammation and genetics in periodontal disease.
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      • Ming Y.
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      Evaluation of the efficacy of treatment modalities in burning mouth syndrome–A systematic review.
      • Wan Mohd Kamaluddin W.N.F.
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      Masticatory muscle function affects the pathological conditions of dentofacial deformities.
      pediatric-restorative dentistry,
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      Clinical management of fusion in primary mandibular incisors: a systematic literature review.
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      • et al.
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      • Silva M.C.P.M.D.
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      • Alencar Filho A.V.
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      Caries experience in children and adolescents with Down Syndrome: a systematic review and meta-analysis.
      peri-implant tissues,
      • Albrektsson T.
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      An imbalance of the immune system instead of a disease behind marginal bone loss around oral implants: position paper.
      • Askar H.
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      Effect of implant vertical position, design, and surgical characteristics on mucosal vertical dimension: a meta-analysis of animal studies.
      • Borges H.
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      Zirconia implants and marginal bone loss: a systematic review and meta-analysis of clinical studies.
      • Ephros H.
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      Peri-implantitis: evaluation and management.
      • Corvino E.
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      • Mura R.
      • Marcano E.
      • Canullo L.
      Influence of modified titanium abutment surface on peri-implant soft tissue behavior: a systematic review of in vitro studies.
      • Gracis S.
      • Llobell A.
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      • Jahangiri L.
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      The influence of implant neck features and abutment diameter on hard and soft tissues around single implants placed in healed ridges: clinical criteria for selection.
      • Iorio-Siciliano V.
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      Soft tissue stability related to mucosal recession at dental implants: a systematic review.
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      Nonsurgical and surgical management of biologic complications around dental implants: peri-implant mucositis and peri-implantitis.
      • Norton M.R.
      • Åström M.
      The influence of implant surface on maintenance of marginal bone levels for three premium implant brands: a systematic review and meta-analysis.
      periodontics-restorative dentistry,
      • Akram Z.
      • Shafqat S.S.
      • Aati S.
      • Kujan O.
      • Fawzy A.
      Clinical efficacy of probiotics in the treatment of gingivitis: a systematic review and meta-analysis.
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      Management of furcation-involved molars: recommendation for treatment and regeneration.
      • Rovai E.S.
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      • et al.
      Root coverage procedures in noncarious cervical lesions with and without restoration: a systematic review and meta-analysis.
      • Soares D.M.
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      The use of enamel matrix derivative in the treatment of class II furcation defects: systematic review and meta-analysis.
      • Trombelli L.
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      What periodontal recall interval is supported by evidence?.
      pharmacology,
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      Anesthetic and analgesic efficacy of bupivacaine in mandibular third molar surgery: a systematic review and meta-analysis.
      • Costa R.
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      Effect of analgesic drugs on tooth sensitivity induced by in-office dental bleaching: a systematic review and meta-analysis.
      • Dawson A.
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      The effect of botulinum toxin A on patients with persistent idiopathic dentoalveolar pain–A systematic review.
      • Dhadwal S.
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      Dentistry's role in assessing and managing controlled substance risk: historical overview, current barriers, and working toward best practices.
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      Opioid prescribing in dental practice: managing liability risks.
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      New approaches to pain management.
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      A review of drugs that contribute to bleeding risk in general dental practice.
      radiology,
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      Intraoral radiographs: a comparison of dose and risk reduction with collimation and thyroid shielding.
      sleep disordered breathing,
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      TMD and orofacial pain,
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      trauma and emergency,
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      and miscellaneous topics.
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      ,
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      General prosthodontic considerations

      Many factors impact the selection of treatment rendered by dentists. In fact, it is quite possible that patients with similar dental and oral conditions may receive substantially different prosthodontic therapy when treated by different practitioners. To investigate if formal training in implant dentistry was associated with treatment proposed by practitioners to edentulous patients and the rationale behind the treatment proposed, Assous et al
      • Assous R.
      • Delprat L.
      • Braud A.
      Training in implantology and decision-making practices regarding edentulism: an internet-based survey.
      reported on an internet-based survey conducted among a cohort of French dentists.
      From July to December 2018, 2000 dental practitioners were provided an internet-based survey intended to assess first-choice treatment proposed to edentulous patients. Questionnaires focused on treatment proposed and why. Demographic data were also collected to determine respondent’s personal and professional background information considered applicable to the questions at hand. Three hundred forty-nine surveys were returned (17.4% response rate), of which 39 were excluded because of missing data.
      Statistical assessment indicated that for most clinicians, the first-choice treatment for the maxilla in edentulous patients was a complete denture (CD, 59.7%), followed by an implant fixed prosthesis (IFP, 25.5%) and an implant overdenture (IO, 14.6%). The first-choice mandibular treatment for a healthy edentulous patient was an IO (45.6%) followed by an IFP (26.1) and a CD (30%). Clinical conditions were most often cited for these choices. Approximately 30% of practitioners proposed a mandibular CD as the first option. Binary logistic regression analysis indicted that the likelihood of proposing implant therapy in the maxilla was significantly greater for male dentists (OR, 2.041; 95% CI: 1.231-3.385; P<.05) and for clinicians who had greater self-perceived skills due to further training in implant dentistry (OR, 2.301; 95% CI: 1.354-3.917; P<.05). In the mandible, the likelihood of prescribing implant treatment was significantly greater for clinicians who graduated 10-19 years ago (OR, 5.312; 95% CI: 1.331-21.208; P<.05), had greater self-perceived skills due to further training in implant dentistry (OR, 2.246; 95% CI: 1.121-4.500; P<.05), had expectations of improved prosthesis comfort and stability (OR, 11.810; 95% CI: 5.289-26.372; P<.001), and proposed treatment based on published national and/or international recommendations (OR, 3.252; 95% CI: 1.208-8.755; P<.05).
      As the article title suggests, training beyond dental school in implant dentistry for the French cohort surveyed appears to be a determining factor for first-choice mandibular treatment for edentulous patients. Treatment also depends on demographic factors, postgraduation clinical experience, and compliance with published therapeutic guidelines. The authors suggested that promoting international consensus recommendations, instruction in implant dentistry, and clinical implant experience among new graduates may increase the proposal of mandibular implant therapy for edentulous patients.
      Dentistry faces significant challenges in the diagnosis and treatment of tooth structure failure in our ever-expanding geriatric patient population. While influenced by many factors, irreversible microstructural changes affecting aging dentin is certainly one important factor. The gradual filling of dentin tubule lumens, a process known as dental sclerosis, begins at the root apex, progresses coronally, and is associated with progressive reduction in the resistance of dentin to fracture. In order to characterize the dynamic mechanical behavior of root dentin with respect to donor age, pulp vitality, and histologic location, Yan et al
      • Yan W.
      • Chen H.
      • Fernandez-Arteaga J.
      • Paranjpe A.
      • Zhang H.
      • Arola D.
      Root fractures in seniors: consequences of acute embrittlement of dentin.
      tested intertubular dentin with nanoindentation-based structural analysis (nanoscopic dynamic mechanical analysis or scanning mode nanoDMA).
      Human single-rooted, noncarious, and structurally nondefective premolars were obtained. Donor age and sex were recorded. A total of 12 teeth from 8 patients were selected and divided into young (n=4; age<25 years), old (n=4; age>60 years), and old nonvital (n=4; age>60 years) groups. Teeth in the old and old nonvital groups were matched pairs from mirrored locations of the arch from the same donor that included a vital tooth and nonvital tooth with prior root canal therapy (RCT).
      The teeth were mounted and sectioned axially (mesial-distal orientation) with subsequent surface finishing soon after acquisition. NanoDMA with scanning probe microscopy (SPM) was performed on intertubular and peritubular dentin of the prepared specimens in a hydrated condition. The loss modulus (damping capacity), storage modulus (elastic behavior), and complex modulus (a combined effect), as well as the tan delta parameter (viscous deformation capacity) were evaluated in apical, middle, and coronal root thirds for teeth with no restorations and those with root canal treatment (nonvital).
      Results indicated significant changes in the dynamic moduli of intertubular dentin with age, particularly in the apical third of the root. The storage modulus (elastic resistance to deformation) was significantly greater (P<.001) for both old vital and nonvital teeth over the entire root length compared with that for young teeth. However, the tan delta parameter (relative capacity for viscous deformation) was significantly lower in these 2 groups (P<.005).
      The authors concluded that radicular dentin loses the capacity for viscous deformation with aging, subsequently becoming embrittled, particularly in the apical third. Additionally, this degradation appears to be accelerated by root canal therapy.
      The objective decrease in saliva flow rate (hyposalivation) may be associated with several adverse outcomes, for example, halitosis, mucositis, stomatitis, Candida infection, poor digestive function, dental caries (because of suboptimal buffering and remineralization), poor comfort and retention of removable dentures, inefficient food bolus formation and transport, difficulty swallowing, altered taste sensation, and problems with phonation. Additionally, saliva plays a role in controlling the composition of the oral microflora by means of antibacterial, antifungal, and antiviral properties. More specifically, hyposalivation has been associated with aging. Hyposalivation can substantially affect oral health and quality of life. Therefore, its occurrence within the population is of interest. Pina et al
      • Pina G.M.S.
      • Mota Carvalho R.
      • Silva B.S.F.
      • Almeida F.T.
      Prevalence of hyposalivation in older people: a systematic review and meta-analysis.
      systematically reviewed available literature to estimate the prevalence of hyposalivation, calculated with stimulated and unstimulated protocols, in noninstitutionalized older adults aged ≥60 years.
      Existing literature on the topic was surveyed up to February 2019. Inclusion and exclusion criteria were applied. Thirteen studies reporting on a total of 3885 (range, 28-800) individuals aged ≥60 years (range, 60-100 years) were included in the review. Methodologies were evaluated for risk of bias, and meta-analyses were performed.
      The results indicated an overall hyposalivation prevalence of 33.37% (95% CI: 23.90-43.57; P<.001; n=3447) with higher prevalence in women. The prevalence of hyposalivation for unstimulated and stimulated protocols was 33.39% (95% CI: 21.08-46.96; P<.001; n=2425) and 30.47% (95% CI: 22.53-39.04; P<.001; n=1495), respectively. Most of the studies demonstrated low risk of bias, 2 had moderate risk, and 1 high risk. Statistical association was found between low salivary flow and the intake of 4 or more prescribed drugs. Study limitations were related to the potential risk of bias in observational studies, identifying and dealing with confounding factors, and the use of different criteria to measure saliva flow rate.
      The authors concluded that the overall prevalence of hyposalivation in their older population is 33.37%. When considering stimulated methods for assessing salivary flow, the prevalence of hyposalivation was slightly lower (30.47%). The authors suggested that data were derived from noninstitutionalized elderly individuals and that the prevalence of hyposalivation in institutionalized elderly individuals may be higher.

      Conventional complete prosthodontics

      While adapting to most new dental prostheses can be a challenge, the challenge offered by conventional complete dentures (CDs) can be overwhelming and may require a substantial adaptation period. Control of the dentures during speech, mastication, deglutition, coordinated mandibular movements, excessive salivation, and routine oral animation must be mastered. It is believed that these problems may be lessened by the appropriate use of denture adhesives and perhaps compounded for patient suffering with advanced alveolar ridge atrophy. To investigate these circumstances, Silva et al
      • Silva M.D.D.D.
      • Viotto H.E.D.C.
      • Policastro V.B.
      • Leite A.R.P.
      • Cassiano A.F.B.
      • Mendoza Marin D.O.
      • et al.
      Influence of adhesives usage in complete dentures during adaptation period varying the degree of resorption of mandibular ridges.
      evaluated the influence of powder-type adhesive on masticatory performance and oral health-related quality of life (OHRQoL) in patients with normal and resorbed mandibular ridges during the adaptation period with new CDs.
      New conventional CDs were provided to 42 edentulous patients (12 men and 30 women, aged 49 to 88 years) using a standard clinical and laboratory protocol. Patient selection criteria included no debilitating systemic of TMJ conditions, normal salivary flow, no previous adhesive use, and previous experience with CDs for at least 1 year. Participants were distributed to 4 groups as follows: (1) normal mandibular ridges with adhesive, n=10; (2) normal mandibular ridges without adhesive, n=10; (3) resorbed mandibular ridges with adhesive, n=11; and (4) resorbed mandibular ridges without adhesive, n=11. Participants scheduled to use adhesive were instructed to do so throughout the observational period following manufacturer’s instructions.
      At 30, 60, and 90 days after CD placement, masticatory performance was evaluated with the sieving method, and OHRQoL was assessed by the Oral Health Impact Profile in Edentulous Adults (OHIP-EDENT) inventory. Data were analyzed with 2-way ANOVA test and generalized estimating equations, α=.05.
      For patients with normal mandibular ridges, results indicated that the use of adhesive was associated with better masticatory performance at 30 days (35.76 ±12.63% weight) and 60 days (30.06 ±10.54% weight) after CD placement but did not influence OHRQoL. By 90 days, the use of adhesive no longer improved masticatory performance relative to normal ridge/no adhesive counterparts. For patients with resorbed mandibular ridges, the use of adhesive did not appear to influence masticatory performance during adaptation period but had a negative effect on masticatory discomfort/disability subscale OHRQoL in the 30-day period (5.2; range, 3.6-6.8).
      Within the limitations of the present clinical investigation, the authors concluded that powder adhesive use may improve CD masticatory performance for normal mandibular ridge CD wearers during the adaptation period (up to 60 days) after prosthesis placement but had no influence on masticatory performance of those with resorbed mandibular ridges. Adhesive use by patient with resorbed mandibular ridges negatively influence OHRQoL (masticatory discomfort/disability subscale) very early in the adaptation period (30 days) but had no influence on normal ridge patients. The results appear to support the use of powder adhesive to ease the new CD adaptation period for patients with normal mandibular ridges, but not for those with resorbed ridges.
      With the rise in popularity of computer-based complete denture (CD) manufacturing, initiating the CAD-CAM workflow with an optical scan is thought to be advantageous. With this in mind, Hack et al
      • Hack G.
      • Liberman L.
      • Vach K.
      • Tchorz J.P.
      • Kohal R.J.
      • Patzelt S.B.M.
      Computerized optical impression making of edentulous jaws-An in vivo feasibility study.
      sought to evaluate the feasibility and accuracy of computerized optical scanning of edentulous jaws in a clinical (in vivo) setting.
      Conventional impressions (modeling plastic impression compound border molded custom trays and polyvinyl siloxane impression material) were made for 29 edentulous patients (27 maxillae and 5 mandibles) in a dental university setting. Prosthodontic faculty members and supervised dental students made all impressions. One faculty member evaluated all conventional impressions for correctness, digitized each 3 times with a laboratory scanner (D700; 3Shape A/S), and cast impressions in stone. Stone casts were then scanned 3 times with the same laboratory scanner.
      At least 1 hour after conventional impression procedures, 3 computerized optical scans (Lava COS or True Definition IS; 3M ESPE) of each edentulous arch were made after titanium oxide powder dusting. A cross-ridge, right-to-left, zig-zag scan path was used in the mandible, while maxillae were scanned with a cross-arch, right-to-left, zig-zag scan path.
      Resulting data sets (stone cast, conventional impression, and optical scans) were loaded into a 3D evaluation software program, and aligned surface scans were subjected to 3D comparisons. The obtained difference values were then statistically analyzed and visually evaluated to identify relevant deviations. Mean differences between the stone cast scans, conventional impression scans, and optical scans were 336.7 ±105.0 μm (n=32), 363.7 ±143.1 μm (n=24), and 272.1 ±168.5 μm (n=29), respectively. Visual evaluations of aligned surfaces indicated greatest deviations (≥500 μm) in the soft palate (posterior palatal seal zone), sublingual vestibular (lingual seal zone), and buccal vestibular (peripheral seal zone) areas.
      Within the limitations of the study, the authors concluded that intraoral scans of the edentulous jaw did not provide the same surface information as obtained from conventional impressions and their resulting stone casts. The intraoral scanners and/or scanning techniques investigated were not able to adequately capture mobile, vestibular, and poorly traceable tissues. Clinical, technical, and software-related improvements appear when necessary. Current scanners and/or scanning techniques appear incapable of adequately replacing conventional impressions for the fabrication of removable complete dentures.
      It is common for dentists to remind patients to remove their complete dentures at night to avoid developing denture stomatitis. Dentists go on to instruct that the dentures must be placed in water while out of the mouth, to avoid dehydration and dimensional change. However, are these routine instructions supported by valid evidence? Additionally, what effects do overnight water storage conditions have on factors know to contribute to denture stomatitis, specifically colonization of intaglio denture surfaces by Candida albicans? To address these questions, Verhaeghe et al
      • Verhaeghe T.V.
      • Wyatt C.C.
      • Mostafa N.Z.
      The effect of overnight storage conditions on complete denture colonization by Candida albicans and dimensional stability: a systematic review.
      systematically reviewed the professional literature to primarily evaluate the effect of overnight storage conditions on denture base colonization by C. albicans. A secondary question, the effect of the overnight storage conditions on denture dimensional stability, was also examined.
      A systematic search of the literature from 1960 to 2018 initially identified 162 relevant articles. Upon application of inclusion/exclusion criteria and further manual searching, 4 studies were identified to address the primary research question. An additional 3 studies were included for the secondary research question.
      Unfortunately, a meta-analysis could not be performed because of significant variation in study design, limited randomized controlled trials, poor power, risk of bias, inadequate demographic information, and varying experimental settings. Study treatments for overnight storage included dry storage, water storage, storage in water with an alkaline peroxide-based cleansing tablet, and storage in water with 0.5% sodium hypochlorite. Overnight storage time was often ill defined. The use of a standardized prestorage cleaning regimen was not established, and follow-up assessments were variable.
      The authors indicated a few general suggestions that surfaced for the articles included in this systematic review: (1) Prestorage manual cleaning is significantly important to reduce C. albicans colonization of denture surfaces; (2) if prestorage manual cleaning is not possible, the use of an alkaline peroxide–based cleaning tablet should be recommended; (3) if an alkaline peroxide–based cleaning tablet is not available, overnight dry storage should be recommended for reducing C. albicans while imparting insignificant dimensional change in the denture; and (4) if the prestorage manual cleaning is not possible, storing the denture in water alone may promote C. albicans colonization and therefore is not recommended. Proper denture hygiene is important before overnight storage of complete dentures, and appropriate patient education in this regard is important.

      Conventional removable partial prosthodontics

      Implant restoration of missing teeth in partial edentulism is a popular solution. However, for those who cannot afford extensive implant therapy, lack sufficient residual bone volume, are not interested in invasive dental surgery, or are satisfied with existing removable partial denture (RPD) solutions, the more expensive and less hygienically accessible fixed implant treatment options are simply not a consideration. While the RPD therapy may be used in the management of Kennedy class I or II partial edentulism, the biomechanical impact of tooth versus soft-tissue support against functional loading must be appreciated. Incorporation of a short dental implant near the distal extent of an RPD extension base can dramatically improve prosthesis support, retention, and stability. To investigate clinical outcomes, Bellia et al
      • Bellia E.
      • Audenino G.
      • Ceruti P.
      • Bassi F.
      Clinical assessment of short implants retaining removable partial dentures: 4-year follow-up.
      prospectively evaluated, at 1 and 4 years, the survival of short implants incorporated into RPD treatment of Kennedy class I and II partial edentulism.
      Patients treated with Kennedy class I and II RPDs between 2004 and 2011 in one clinic and fulfilling specific criteria were offered placement of a single short (5-6 mm in length and 5-6 mm in diameter) implant in the distal edentulous ridge. Twenty patients fulfilled eligibility requirements and were enrolled for treatment. These individuals received a total of 35 maxillary (n=7) and mandibular (n=28) implants between 2012 and 2014. Upon osseointegration, LOCATOR abutments (range, 1-4 mm height) were used to engage the existing prostheses. Implant survival and mobility, peri-implant bone loss evaluated with periapical radiographs, bleeding on probing (BOP), and probing depth (PD) were assessed at the time of prosthesis engagement, at 1-year follow-up, and at 4-year follow-up.
      The results indicated that at the 4-year follow-up, 12 implants showed BOP. For PD, 15 implants showed 2 mm, 16 implants showed 3 mm, and 2 implants showed 4 mm. One implant was mobile, and 2 were lost for a survival rate of 94.3% (95% CI: 80.84-99.30). The mean bone loss was 1.04 ±1.88 mm.
      Within the limitations of this preliminary clinical study, implant survival rate and the mean bone loss values recorded are comparable to those reported in current literature. RPD extension bases supported, retained, and stabilized by short, wide-platform dental implants with LOCATOR attachments can be considered a suitable treatment option for partially edentulous patients presenting reduced vertical height of the edentulous ridge. This approach serves to improve rotational prosthesis mechanics during functional loading and avoids invasive surgical interventions required for the placement of longer implants. Additional clinical trials should be pursued to demonstrate favorable longer term survival and associated patient benefits with the use of short implants as described here. Periodic standardized clinical and radiographic examinations used to assess implant survival and the occurrence, severity, and progression of bone resorption must be included.
      While Bellia et al
      • Bellia E.
      • Audenino G.
      • Ceruti P.
      • Bassi F.
      Clinical assessment of short implants retaining removable partial dentures: 4-year follow-up.
      demonstrated favorable clinical results when placing dental implants to assist with the support, retention, and stability of existing dental implants, Park et al
      • Park J.H.
      • Lee J.Y.
      • Shin S.W.
      • Kim H.J.
      Effect of conversion to implant-assisted removable partial denture in patients with mandibular Kennedy classification I: a systematic review and meta-analysis.
      systematically reviewed the literature to assess impact on treatment outcomes with this clinical approach. Specifically, this review considered outcomes assessments before and after conversion from a conventional Kennedy class I RPD to an implant-assisted RPD. Success in treatment was evaluated with patient-reported outcome measures (PROMs), objective parameters of functional performance, and the occurrence of biological and mechanical complication.
      After structured database searching and subsequent electronic and hand searches, a total of 6544 articles were initially identified. Exclusion based on selection criteria yielded 19 publications based on 13 independent studies (3 randomized controlled trials) appearing between 2008 and 2018.
      Meta-analysis of available data indicated that after conversion to Kennedy class I implant-assisted RPDs, treatment outcomes across a wide range of parameters were significantly improved. General patient satisfaction and mastication were significantly improved (P<.05). In oral health-related quality of life, the total Oral Health Impact Profile scores improved, including improvements in physical pain and psychological disability (P<.05). Masticatory performance was improved (P<.05) in terms of maximum occlusal force, active occlusal contact area, and mandibular jaw movement timing (opening, closing, and cyclic movements). The weighted mean survival rate of implants (2.0-4.7 mm in diameter; 6-14 mm in length; mean follow-up, 2.3 years; range, 0.5-10 years) was 96.60%. The authors concluded that after conversion from a conventional Kennedy class I RPD to and implant-assisted RPD, the treatment outcomes were significantly improved across a wide range of parameters associated with implant dentistry, including patient-reported outcome measures and masticatory performance.
      The widespread application of CAD-CAM technology offers significant convenience with respect to RPD frameworks design and manufacturing. Today, time-consuming and technique-sensitive conventional laboratory steps give way to straightforward and intuitive computer-based processes. However, as is so often the case, the question of accuracy of the definitive restoration remains unanswered. To shed light on this important question, Tasaka et al
      • Tasaka A.
      • Shimizu T.
      • Kato Y.
      • Okano H.
      • Ida Y.
      • Higuchi S.
      • et al.
      Accuracy of removable partial denture framework fabricated by casting with a 3D printed pattern and selective laser sintering.
      compared the accuracy of RPD frameworks produced by workflows involving casting 3D-printed additive manufacturing patterns (AM-Cast) and workflows incorporating selective laser sintering (SLS).
      A mandibular partially edentulous experimental model simulating a Kennedy class II, modification 1, clinical situation was used. Appropriate rest seats and axial abutment contours were provided. The model was digitally acquired with a dental laboratory scanner, and a CAD software program was used to design an experimental RPD framework according to the RPI concept.
      To facilitate flow of molten alloy in the AM-Cast group, accessory sprues were placed between the tips of the buccal and lingual clasp arms of each clasp assembly resin pattern. To limit pattern distortion during polymerization, 2 cross-arch bars were incorporated in the patterns. Printed resin framework patterns were additively manufactured in a 3D printer, invested, and cast in cobalt-chromium alloy.
      For SLS frameworks, the same CAD data used to produce resin patterns in the AM-Cast group were sent to a direct metal laser sintering machine. Framework orientation ensured parallelism between the occlusal surfaces of the rests and the machine base. A 1100- to 1200-mm/second sintering speed, 0.08- to 0.1-mm laser spot diameter, and 0.02-mm layer thickness were used. After sintering, frameworks were annealed (1000 °C; 30 minutes) and homogenized (1150 °C; 30 minutes). Five AM-Cast and 5 SLS frameworks were fabricated. Three-dimensional scans of all frameworks were individually superimposed on original design (CAD) data and statistically assessed for fit.
      The results indicated a range of differences in the AM-Cast frameworks (−0.185 ±0.138 to 0.352 ±0.143 mm) and in the SLS group (−0.166 ±0.009 to 0.123 ±0.009 mm). Significant differences were observed at the rests, proximal plates, connectors, and clasp arms. Regarding the rests, both lateral and medial displacements were observed for both manufacturing types relative to design data. The AM-Cast frameworks demonstrated large lateral discrepancies of the connectors joining clasp assemblies to lingual bar major connectors on the tooth-supported side. The SLS frameworks demonstrated significant discrepancies at the center of the lingual bar. Between the manufacturing techniques, fabrication accuracies appeared to differ depending on the specific RPD structural component.
      The authors concluded that overall discrepancies were smaller for SLS framework, suggesting that it may be superior to AM-Cast in terms of fabrication accuracy and reproducibility. The authors were quick to indicate that the present study had limitations. Conventional casting could not be included as an experimental condition because standardization of hand-waxed patterns is difficult. Furthermore, while only one RPD design was used in this investigation, various designs are possible and should be studied. In particular, the configuration of major connectors, for which accuracy was found to be an issue in the SLS workflow, varies dramatically depending on design concept used and dental arch involved, thus requiring further investigation.

      Conventional fixed prosthodontics

      In vitro experiments, while informative, may not provide the information needed by clinicians for the day-to-day practice of fixed prosthodontics. Long-term in vivo data are often considered more desirable. Long-term clinical data on the survival of pressed lithium disilicate glass-ceramic restorations and the effect that different technical and clinical variables have on survival are lacking. With this in mind, a series of reports emerging from one private practice
      • Malament K.A.
      • Natto Z.S.
      • Thompson V.
      • Rekow D.
      • Eckert S.
      • Weber H.P.
      Ten-year survival of pressed, acid-etched e.max lithium disilicate monolithic and bilayered complete-coverage restorations: performance and outcomes as a function of tooth position and age.

      Malament KA, Margvelashvili-Malament M, Natto ZS, Thompson V, Rekow D, Att W. 10.9-year survival of pressed acid etched monolithic e.max lithium disilicate glass-ceramic partial coverage restorations: Performance and outcomes as a function of tooth position, age, sex, and the type of partial coverage restoration (inlay or onlay). J Prosthet Dent 2020 October 2 [Epub ahead of print].

      Malament KA, Margvelashvili-Malament M, Natto ZS, Thompson V, Rekow D, Att W. Comparison of 16.9-year survival of pressed acid etched e.max lithium disilicate glass ceramic complete and partial coverage restorations in posterior teeth: Performance and outcomes as a function of tooth position, age, sex, and thickness of ceramic material. J Prosthet Dent 2020 Sep 30 [Epub ahead of print].

      involving a prospective database with controls for clinical and laboratory variables reported on recall findings of a substantial patient population. The purpose of the initial clinical report in this series
      • Malament K.A.
      • Natto Z.S.
      • Thompson V.
      • Rekow D.
      • Eckert S.
      • Weber H.P.
      Ten-year survival of pressed, acid-etched e.max lithium disilicate monolithic and bilayered complete-coverage restorations: performance and outcomes as a function of tooth position and age.
      was to examine the 10-year survival of pressed lithium disilicate glass-ceramic monolithic and bilayer restorations and the relationship between clinical parameters and outcomes.
      All participants required single complete coverage restorations in any area of the mouth, 3-unit fixed partial dentures, cantilevered anterior restorations, or foundation restorations on teeth, implant abutments, or a combination of the 2. Participants were offered gold, metal-ceramic, or lithium disilicate restorative options and informed of anticipated risks and benefits. Participants choosing lithium disilicate restorations were included in the study. Overall restoration survival was determined based on clinical criteria assessed at recall.
      Five hundred and fifty-six patients (mean age, 62 years; range, 17-97 years; 40% men) electing lithium disilicate restorations were enrolled. Many patients received more than one restoration. Of the 1960 complete coverage lithium disilicate restorations provided (1410 monolithic; 550 bilayer), 7 failures (bulk fracture or large chip, affecting only monolithic restorations) were recorded indicating a 0.14% per year risk of failure. The average time to failure was 4.2 years. The 10-year estimated cumulative survival was 99.6% (95% CI: 99.4-99.8). The estimated cumulative survival was 96.5% for monolithic and 100% for bilayer restorations, at 10.4 and 7.9 years, respectively (P<.05). The risk for monolithic restoration failure was 0.2% per year. These failures occurred primarily in molars (5 of 7 failures) and in both arches (3 maxilla, 2 mandible). No failures were recorded for the bilayer restorations.
      The authors concluded that pressed lithium disilicate restorations followed up in this single private practice were very successful over the 10.4-year observation period with an overall failure rate below 0.2% per year mainly associated with molar restorations. The risk of failure was minimal at any age for both men and women.
      In similar fashion, a carefully developed prospective database emerging from the same private practice

      Malament KA, Margvelashvili-Malament M, Natto ZS, Thompson V, Rekow D, Att W. 10.9-year survival of pressed acid etched monolithic e.max lithium disilicate glass-ceramic partial coverage restorations: Performance and outcomes as a function of tooth position, age, sex, and the type of partial coverage restoration (inlay or onlay). J Prosthet Dent 2020 October 2 [Epub ahead of print].

      was used to assess the effect of risk factors on adhesively bonded lithium disilicate glass-ceramic partial coverage restorations. Database parameters and recall methods were adopted from the previously reviewed publication.
      • Malament K.A.
      • Natto Z.S.
      • Thompson V.
      • Rekow D.
      • Eckert S.
      • Weber H.P.
      Ten-year survival of pressed, acid-etched e.max lithium disilicate monolithic and bilayered complete-coverage restorations: performance and outcomes as a function of tooth position and age.
      The purpose of this clinical study was to report the 10.9-year survival of acid-etched, adhesively bonded, monolithic, pressed, lithium disilicate, partial coverage restorations and associated clinical parameters on outcomes.
      Patients requiring partial coverage restorations in any area of the mouth were recruited. Participants were offered direct dental amalgam, direct composite resin, partial coverage cast gold, or lithium disilicate restorative options and informed of anticipated risks and benefits. They were also offered complete coverage restorations when appropriate. Only patients choosing lithium disilicate partial coverage restorations were enrolled. The overall survival of these lithium disilicate restorations was assessed relative to specific clinical factors (age, sex, dental arch, tooth position, type of partial coverage restoration, and ceramic thickness) at 6-month recall intervals. Fractured ceramics necessitating restoration remake were considered failures.
      After 15 years of data collection, 304 participants (mean age, 62 years; range, 20-99 years; 40% men) possessing 556 pressed lithium disilicate partial coverage restorations (246 were inlays, 305 were onlays) were assessed. Six failures were recorded during the observation period (3 inlays, 3 onlays, molar regions only), with the average time to failure of 2.4 years (range, 0.8-9.2 years). The crude estimated failure risk was 0.3% per year, with the survivor function time at 10.9 years. The 10-year estimated cumulative survival was 95.6%. The estimated cumulative survival was 93.9% for inlays and 98.3% for onlays, at 9.9 and 9.8 years, respectively (P<.05). No significant difference in the survival was recorded between men and women, different age groups, or position in the dental arch, and thickness of the restoration had no significant influence on the survival (P<.05).
      The authors concluded that their data indicated that properly managed monolithic pressed lithium disilicate partial coverage restorations exhibited excellent survival, yielding only 6 failures and a 10-year cumulative survival of 95.6% (overall failure rate of 0.3% per year, failures limited to molars). The potential confounding variables of tooth position, sex, age, or type of partial coverage restoration exhibited minimal to no effect on survival. Considering the substantial patient population and observation period, the current report can be used to guide clinicians in choosing minimally invasive, partial coverage, esthetic restorations.
      A third publication originating from the same private prosthodontic practice

      Malament KA, Margvelashvili-Malament M, Natto ZS, Thompson V, Rekow D, Att W. Comparison of 16.9-year survival of pressed acid etched e.max lithium disilicate glass ceramic complete and partial coverage restorations in posterior teeth: Performance and outcomes as a function of tooth position, age, sex, and thickness of ceramic material. J Prosthet Dent 2020 Sep 30 [Epub ahead of print].

      sought to investigate the 16.9-year survival of exclusively posterior pressed lithium disilicate complete and partial coverage restorations and the effects of associated parameters on clinical outcomes. Patients requiring either single-unit posterior partial coverage restorations, complete coverage restorations, or a combination were recruited. Participants were offered direct dental amalgam, direct composite resin, cast gold, metal-ceramic, or lithium disilicate restorations. Those requiring complete coverage restorations were given the options of complete cast gold, metal-ceramic, or glass-ceramic restorative options and informed of anticipated risks and benefits. Only participants who chose lithium disilicate partial and complete coverage restorations were enrolled. The effect of various clinical parameters on success of the restorations (age, sex, dental arch, tooth position, type of restoration, and ceramic thickness) was assessed at 6-month recall intervals. Fractured ceramics necessitating restoration remake were considered failures.
      A total of 738 participants (mean age, 62 years; range, 20-99 years; 302 men) requiring 2392 lithium disilicate restorations (1782 complete coverage; 610 partial coverage) in posterior teeth were evaluated. A total of 22 failures (16 complete coverage; 6 partial coverage) were recorded with the average time to failure 3.5 years (range, 0.02-7.9 years). The overall estimated failure risk was 0.17% per year (0.16% complete coverage; 0.19% partial coverage). The overall 16.9-year estimated cumulative survival was 96.5%. The estimated cumulative survival was 96.8% for posterior complete and 95.3% for posterior partial restorations, at 10.5 and 16.9 years, respectively (P<.05). No significant difference in the survival was recorded between men and women, different age groups, or position in the dental arch, and thickness of the restoration had no significant influence on the survival. No statistically significant difference was found in the survival of posterior complete and partial coverage restorations among men and women, different age groups, or posterior tooth position (P>.05). The thickness of the restoration also had no influence on the survival (P>.05), and restorations with surfaces <1 mm and ≥1 mm performed similarly over 16.9 years.
      The authors concluded that acid-etched, adhesively bonded, monolithic, pressed, lithium disilicate, complete and partial coverage restorations exhibited excellent survival in the posterior teeth up to 16 years of clinical function, demonstrating no significant differences in performance between complete and partial coverage restorations. The covariates of tooth position, sex, age, and restoration thickness do not impact survival. The authors indicated that their study provided ample evidence to guide clinicians in treatment selection and material options.
      As reflected in these clinical reports, our appreciation for the durability of esthetic materials in the modern prosthodontics is critically important. To the end, contemporary dental laboratories generally track the clinical performance of restorations they manufacture and provide. In order to test the quality of material and restoration durability, Sulaiman et al
      • Sulaiman T.A.
      • Abdulmajeed A.A.
      • Delgado A.
      • Donovan T.E.
      Fracture rate of 188695 lithium disilicate and zirconia ceramic restorations after up to 7.5 years of clinical service: a dental laboratory survey.
      surveyed dental laboratories to determine the fracture rate of layered and monolithic lithium disilicate and zirconia single crowns and fixed partial dentures (FPDs) up to 7.5 years in clinical service.
      Two major dental laboratories were engaged, both of which offer warranty services and use database systems capable of tracking restoration remakes secondary to material fracture. Data were gathered on 188 695 restorations (51 751 lithium disilicate, 36 198 monolithic, 15 553 layered; 136 944 zirconia, 93 848 monolithic, 43 096 layered) over a period of 7.5 years from 2010 to 2017. Lithium disilicate restorations were categorized into single crowns, FPDs, veneers, or onlays. Zirconia restorations were categorized into single crowns or FPDs, and then into anterior or posterior restorations. Restoration remakes due to poor fit, inappropriate shade, or poor marginal integrity were excluded from consideration.
      The overall restoration fracture rate was 1.35%. For lithium disilicate, the fracture rate for monolithic single crowns (0.96%) was significantly lower than that for layered single crowns (1.26%; P<.05), and the single crown fracture rate was significantly less than the FPD (monolithic and layered) fracture rate (P<.001). There was no significant difference in fracture rates between monolithic (3.66%) and layered FPDs (2.82%; P=.151), or between monolithic (1.15%) and layered veneers (1.21%; P=.866).
      For zirconia, monolithic single crowns fractured at a lower rate (0.54%) than layered single crowns (2.83%) and monolithic fixed partial dentures (1.83%; P<.001), while layered single crowns (2.83%) fractured at a higher rate than layered FPDs (1.93%; P<.001). Monolithic zirconia anterior and posterior restorations fractured at a lower rate than layered anterior and posterior restorations (P<.05). Monolithic zirconia posterior restorations fractured at a lower rate than anterior restorations, while layered zirconia posterior restorations fractured at a higher rate than anterior restorations (P<.05).
      Based on these findings, the authors concluded that the routine use of monolithic and layered lithium disilicate and zirconia ceramics demonstrates low and clinically acceptable fracture rates over a period of 7.5 years of function, with layered restorations demonstrating a higher fracture rate than monolithic restorations. Zirconia FPDs displayed a lower fracture rate than lithium disilicate FPDs, confirming the preferred use of zirconia for FPDs from a structural perspective. The authors indicated that the data presented can be valuable to clinicians, researchers, and manufacturers.

      General implant prosthodontic considerations

      Significant mechanical improvements have been introduced for dental implant screw joints over the past 30 years. However, retention screw loosening and screw joint failure may still adversely impact clinical success, particularly when it comes to single-tooth implant restorations. Colpak and Gumus
      • Colpak E.D.
      • Gumus H.O.
      Effect of surface modifications of abutment screws on reverse torque values: an in vitro study.
      used an in vitro thermomechanical cycling experimental protocol to determine reverse torque values for abutment screws manufactured with various surface modifications.
      Sixty abutment screws (grade 5 titanium alloy) were divided evenly into 2 groups (with and without thermomechanical cyclic loading). Each group was then divided into 3 subgroups according to screw surface treatment, including no treatment (NT; n=10), anodic oxidation (AO; n=10), and diamond-like carbon coating (DLC; n=10). The DLC coating is generally considered to provide excellent protection against abrasion, tribo-oxidation, and adhesive wear while permitting high thread surface pressures that may cause cold welding. All abutment screws were fastened (30 Ncm) to implants through stock abutments and tightened with a digital torque meter. Half of the resulting specimens were subjected to vertical thermomechanical cyclic loading (120 N; 240 000 cycles; 5 °C-55 °C) that represented approximately 1 year of clinical loading. Abutment screw reverse torque values were then measured. Percentage deviations (PDs, before-after thermomechanical cycling) were calculated and statistically analyzed.
      The results indicated a decrease in reverse torque values for all groups after thermomechanical cycling indicating a generalized loss of screw joint preload. The loss of preload was greatest for the NT group, followed by the DLC group. The AO group demonstrated the least screw torque loss with and without thermomechanical cycling (P<.001 for each). A significant interaction was found between surface treatment and thermomechanical cycling (P<.001).
      Within the limitations of this in vitro investigation, the authors concluded that abutment screw reverse torque values were greater for screw with AO and DLC surface treatments. AO treatment screws exhibited the lowest torque loss (maintained greater preload) with and without thermomechanical cycling. The authors suggested that further study of the possible influence of AO to maintain screw joint stability should be pursued.
      For most of the modern dental implant era, titanium has been used because of its favorable biocompatibility, significant strength, resistance to corrosion, and potential for osseointegration. More recently zirconia was introduced as a possibility alternative implant material citing good biocompatibility and tissue integration with better esthetic characteristics. Improvements in reliability and strength of zirconia applications in implant dentistry are expected. The long-term success of dental implants may be influenced by microbial adhesion to implant, abutment, and restoration surfaces. To avoid adverse peri-implant soft-tissue responses, it would be helpful to know whether there are material-specific influences on microbiome development at early and late stages of biofilm formation. To better understand potential influences, Desch et al
      • Desch A.
      • Freifrau von Maltzahn N.
      • Stumpp N.
      • Dalton M.
      • Yang I.
      • Stiesch M.
      Biofilm formation on zirconia and titanium over time-An in vivo model study.
      reported on an in vivo model for biofilm formation used to evaluated biofilm volume, vitality, and diversity on zirconia and titanium (grade 4) abutment surfaces as a function of time.
      Titanium and zirconia disks (Ø3×2 mm) cut from stock bars were processed to achieve a mean surface roughness comparable to that of an implant abutment (Ra of 0.3-0.4 μm). Disks (specimens) were then incorporated into recesses within maxillary complete-arch devices at buccal gingival posterior interproximal embrasures. With the devices in place, 8 specimens per device (4 titanium; 4 zirconia) were exposed to oral conditions in 12 volunteers for wearing times of 6, 24, 72, and 120 hours. At each time point, 2 randomly located specimens of each material were carefully removed for parallel analyses by confocal laser scanning microscopy (CLSM) and PacBio single-molecule real-time sequencing (SMRT). A statistical analysis was performed, and the level of significance was set at 0.05.
      CLSM revealed significant increases in biofilm volume over time on zirconia and titanium. The material did not significantly influence the volume or live/dead ratio at the individual time points investigated, although variations between volunteers were high. The composition of the microbiome was influenced by the age of the biofilm, but not by the material. The most frequently found bacteria were Streptococcus spp., followed by Neisseria spp., Rothia spp., Haemophilus spp., Gemella spp., and Abiotrophia spp.
      Within the limitations of the study, the authors suggested that, while the quantity and diversity of the microbiome increased over time, there were no differences between zirconia and titanium in quantity and negligible differences in the abundances of adhered species. Further studies are necessary to obtain more microbiological information from hosts and evaluate other potential influencing factors. Differences between the microbiota samples may be dominated by the variability among study participants and developments correlated with biofilm age.
      Recently, cone bean computed tomography (CBCT) has been recognized as an important tool in dentistry, particularly with respect to dental implant treatment planning. Apart from oral, dental, and jaw regions within the scan of specific interest to the treatment in question, CBCT scans inevitably include other head and neck anatomical areas. Significant incidental findings (IFs) related to regional structures are frequently indicated within the scan volume. Unfortunately, many dental clinicians lack the training necessary for the interpretation of IFs. To investigate this concern, Nguyen et al
      • Nguyen P.N.
      • Kruger E.
      • Huang T.
      • Koong B.
      Incidental findings detected on cone beam computed tomography in an older population for pre-implant assessment.
      conducted a retrospective analysis of IFs in CBCT scans made for older patients during dental implant treatment assessment, and to determine whether these IFs influenced the intended dental implant therapy. The authors defined an IF as one outside of the clinical focus of the CBCT examination and otherwise not known clinically or not detected with plain film imaging (bitewing, periapical, and/or panoramic imaging).
      A retrospective review by a board-certified specialist was accomplished on 300 consecutive CBCT scans referred by a private dental practice for the purpose of implant planning on patients older than 40 years. CBCT machine, scan volume, and scan protocol remained consistent. The IFs were categorized into region (dentoalveolar, nondentoalveolar maxilla and mandible, paranasal sinuses, TMJ, nasopharyngeal/oropharyngeal airway, cervical spine, neurovascular canals) and influence on the course of treatment (no follow-up needed, significant IFs requiring follow-up but no treatment alteration, significant IFs requiring follow-up and treatment alteration).
      The results indicated that IFs were observed in all CBCT scans (555 total; mean, 1.85 IFs/scan). The highest number of IFs was seen in the sinuses (34%), followed by dentoalveolar structures (31%), nasopharyngeal/oropharyngeal airway (12%), maxilla and mandible (10%), TMJ (6%), cervical spine (4%), and neurovascular canals (3%). A total of 37% of IFs required follow-up. For 12% of the patients, the detection of the IFs resulted in amendment or cancellation of the intended implant treatment plan.
      The authors concluded that IFs in CBCT scan volumes within and beyond the region of interest are common and important to identify. The number of incidental findings per scan in an older population is likely greater than that in younger populations. The authors also emphasized the importance of interpreting CBCT volume in its entirety, regardless of the focused area of the scan based on the intended treatment plan.

      Implant removable prosthodontics

      Although ill defined, posterior mandibular alveolar bone loss in edentulous patients is thought to reflect the combined impact of multiple anatomic, physiologic, and prosthodontics factors. One unfavorable outcome of this bone loss is compromised oral functional for patients wearing conventional complete dentures (CDs). The addition of dental implants is believed to improve compromised function by enhancing prosthesis support, stability, and retention. In order to consider an optimal therapeutic approach, Oh et al
      • Oh W.S.
      • Saglik B.
      • Bak S.Y.
      Bone loss in the posterior edentulous mandible with implant-supported overdentures vs complete dentures: a systematic review and meta-analysis.
      systematically reviewed current evidence related to posterior alveolar bone loss in the posterior mandibles of edentulous patients restored with mandibular complete dentures (CDs), 2-implant overdentures (2-IODs), and 4-implant overdentures (4-IODs).
      A search of the professional dental literature was conducted in major databases to address the population, intervention, comparison, outcome (PICO) question, “Are mandibular IODs associated with greater posterior mandibular alveolar bone loss in edentulous patients than conventional mandibular CDs?” The search strategy initially identified 2806 articles. General article review identified 22 reports, of which 8 did not meet inclusion criteria and 7 were excluded for methodological reasons. Date from the remaining 7 studies were pooled, and a meta-analysis was performed to estimate mean differences in bone loss (95% CI; α=.05).
      The results indicated no significant differences in posterior mandibular bone loss between 2-IODs and CDs (mean difference, −0.25 mm; 95% CI: −0.85-0.36; P=.43). Posterior mandibular bone loss was identified to be significantly less with 4-IODs than with 2-IODs (mean difference, −0.96 mm; 95% CI: −1.86-0.06; P=.04). In general, the data were highly heterogeneous with a wide range of variables (τ2>0.44; I2>74%). The included studies were found to have either moderate or high methodologic quality (STROBE checklist).
      Within the limitation of this systematic review and meta-analysis and relative to mandibular posterior alveolar bone loss over time, the authors suggested that 4-IODs are associated with less bone loss than 2-IODs and that 2-IODs do not appear to be superior to conventional CDs. As is generally the case, the authors suggested that validation of these results is needed and should be accomplished with well-designed randomized controlled clinical investigations.
      In like manner, the same lead author with a different group of colleagues (Oh et al
      • Oh W.S.
      • Oh J.
      • Jin Q.
      Bone loss in the anterior edentulous maxilla opposing two-implant-supported overdentures vs complete dentures: a systematic review and meta-analysis.
      ) investigated anterior maxillary alveolar bone loss in edentulous patients restored with maxillary complete dentures opposing either mandibular 2-implant overdentures (2-IODs) or mandibular complete dentures (CDs). The combination of a maxillary CD opposing a mandibular 2-IOD is thought to be reminiscent of prosthodontic conditions associated with what has become to be known as combination syndrome (Kelly
      • Kelly E.
      Changes caused by a mandibular removable partial denture opposing a maxillary complete denture.
      ).
      A systematic search of the dental literature was conducted in major databases to address the PICO question, “Are mandibular IODs associated with greater anterior alveolar bone loss in edentulous patients than conventional mandibular CDs?” The search strategy initially identified 2510 articles. General article review identified 14 reports. Risk of bias was assessed. After hand searching, the application of exclusion criteria, and assessment of methodology, 6 articles remained accounting for a total of 163 patients. Data from the remaining articles were pooled, and a meta-analysis was performed to estimate mean differences in bone loss (95% CI; α=.05).
      The results indicated no statistically significant difference in bone loss in the anterior edentulous maxilla when opposed by mandibular 2-IODs as compared with mandibular CDs. The total estimate of weighted mean difference between 2-IODs and CDs was −1.40 mm (95% CI: −3.12-0.31; P=.11). The data were heterogeneous across the studies (τ2=5.53; I2=95.21%). In addition, a subgroup analysis was conducted to assess that impact of implant splinting (bar-retained IODs). No significant impact could be identified (P>.29), and data were heterogeneous across studies (τ2=6.12; I2=92.74%). None of the included studies were considered at high risk of bias.
      Within the limitations of the systematic review and meta-analysis, the authors concluded that no significant difference in estimated anterior maxillary alveolar bone loss was found for edentulous patients wearing maxillary CDs opposing either mandibular 2-IODs or mandibular CDs. Again, the authors suggested that the results of this systematic review should be validated through well-designed randomized controlled clinical trials.
      While clinical reports are not typically included in this annual publication, a recent publication involving novel, recently available, angle-correcting overdenture abutments (Novaloc; Institut Straumann AG) deserves a look. In this clinical report, Yue et al
      • Yue Q.
      • Yilmaz B.
      • Abou-Ayash S.
      • Zimmermann P.
      • Brägger U.
      • Schimmel M.
      Use of an attachment system with angulated abutments and polyetheretherketone inserts to retain a maxillary overdenture: a clinical report.
      presented the rehabilitation of a patient’s edentulous maxillary arch.
      Years after dental rehabilitation for generalized amelogenesis imperfecta, a 34-year-old man presented for additional dental therapy. The patient was in good general health, retained only mandibular anterior teeth, and desired improved social interactivity and more effective mastication. Based on diagnostic findings and patient desires, a treatment plan was developed to include surgical placement of 3 additional implants for a 5-implant maxillary overdenture supported by nonsplinted attachments. The planned mandibular restoration involved a combination of implant- and tooth-supported fixed prosthodontic restorations. Minimal bone augmentation was an objective.
      After implant placement and healing, overdenture abutments selection was considered. Upon assessing maxillary implant relative trajectories, 3 of the 5 maxillary implants demonstrated marked occlusal divergence. A means of angulation correction to achieve abutment parallelism was sought. Within the implant system (Straumann) used, an angle-correcting overdenture abutment system, recently brought to market, was selected. The Novaloc 15-degree angle-correcting abutments were fastened to the divergent implants, and straight abutments were placed on those that remained. The resulting near parallelism of abutments yielded a satisfactory path of prosthesis placement.
      Using standard clinical and laboratory procedures, a maxillary palateless overdenture was fabricated incorporating a cobalt-chromium alloy reinforcing framework. Laboratory processing of attachments followed by a routine indirect method was used to incorporate 5 titanium housings within the denture base. The system uses polyetheretherketone (PEEK) attachment inserts. When compared with nylon inserts used by other attachment systems, PEEK is thought to demonstrate reduced wear during clinical use. Light retention force (white) PEEK inserts were chosen for the patient to permit adequate prosthesis retention given expected clinical conditions.
      After prosthesis placement, the patient expressed satisfaction with the outcome, indicating favorable mastication and a natural appearance that fulfilled his objectives for pursuing treatment. Unfortunately, no clinical follow-up data were made available.
      The authors concluded that having an angulated prefabricated overdenture stud-type abutment option can help establish attachment parallelism with divergent implants in a time- and cost-efficient manner. While this report involved Straumann implants, Novaloc abutments are also available for other major implant systems. Combined implant divergence of up to 60 degrees can be accommodated with this system. A new abutment surface coating and the PEEK matrices may result in less wear under routine clinical conditions than other currently available systems. The authors suggested that in vitro and in vivo investigations should be conducted to discern long-term outcomes with the Novaloc system.

      Implant fixed prosthodontics

      A relatively recently reported and all too frequent adverse outcome associated with implant-supported fixed restorations is the propensity for interproximal contact loss (PCL). The tendency for the natural dentition to display mesial drift seems an oversimplified explanation because both mesial and distal PCL have been associated with implant restorations clinically. As the proximal gap is observed to increase over time, food impaction tends to occur placing the periodontal and peri-implant tissues at risk. Several articles appeared in the 2020 dental literature addressing this clinical phenomenon. Liang et al
      • Liang C.H.
      • Nien C.Y.
      • Chen Y.L.
      • Hsu K.W.
      The prevalence and associated factors of proximal contact loss between implant restoration and adjacent tooth after function: a retrospective study.
      evaluated the prevalence of PCL up to 18 years after implant prosthesis placement and evaluated potential associated factors.
      A total of 317 patients who had received posterior fixed implant-supported dental restorations between 1999 and 2017 were enrolled in this study (120 men, mean age, 54 years). Restoration characteristics included 349 single-implant-supported crowns, 200 splinted implant-supported FPDs, 549 mesial contacts, 301 distal contacts, 26 screw-retained, 291 cemented, and average functional time 5.2 years (range, 0.3-18.2). Surgical implant placement and definitive implant restoration were accomplished with standard procedures. The definitive restoration proximal contacts were assessed with dental floss. If the floss passed through the proximal contact area with sufficient resistance, the proximal contacts were considered closed. Dental occlusion on implant restorations was adjusted to provide 25 μm of clearance light occlusal contact and definitive contact during heavy closure.
      At follow-up, 1 examiner assessed 19 clinical factors, including proximal contact tightness, oral hygiene condition and habits, periodontal conditions, presence of plunger cusps, proximal food impaction, adjacent tooth vitality and mobility, opposing dentition, and occlusal scheme. Proximal contacts located both mesial and distal (if present) to implant restorations in question were evaluated with dental floss and qualified as tight, loose, or open. Chi-square test, univariate generalized estimating equation (GEE), and multivariate GEE were used to identify factors influencing PCL.
      The rate of mesial PCL (27%) was significantly greater than that of distal PCL (5%), and both were observed to increase over time in function. Analyses identified 6 factors to be significantly associated with mesial PCL (P<.05), including patient age, years in implant function (>5 years; P=.003), frequency of interdental brush use, splinted or single-implant design, presence of plunger cusp, and food impaction. Although limited in occurrence, 3 factors, including restoration type, adjacent tooth vitality, and food impaction, were significantly associated with distal PCL (P<.05).
      The authors concluded that mesial PCL for fixed implant restorations in partially edentulous patients was frequent and increased over time of restoration use. Patients should be made aware of the potential complication and instructed in the use of an occlusal retainer to prevent PCL. Although oral hygiene conditions were seen to contribute little to PCL, food impaction and the use of interdental brushes were significant. The authors suggest that prospective investigations addressing other possible factors, such as previous orthodontic treatment, growth factors, and parafunctional habits, should be conducted to better identify the etiologic basis for PCL. The authors cited the need for better pretreatment records (radiographs and orthodontic treatment records) and possible bias arising from a single follow-up examiner as limitations of the study design.
      To investigate durability of restored proximal contacts from a subtly different perspective, Oh et al
      • Oh W.S.
      • Oh J.
      • Valcanaia A.J.
      Open proximal contact with implant-supported fixed prostheses compared with tooth-supported fixed prostheses: a systematic review and meta-analysis.
      systematically reviewed published reports addressing the odds of developing open proximal contacts (OPCs) between natural teeth and adjacent implant- and tooth-supported fixed prostheses. Additionally, the authors sought to estimate the odds of developing OPCs with the prosthesis as a predictor variable.
      A comprehensive search of existing professional literature was conducted for clinical studies on the development of OPCs related to implant- or tooth-supported prostheses. The PICO question asked was, “Are the odds of developing OPCs greater with implant- or with tooth-supported prostheses?” Thirty-three reports emerged from the initial search. When subjected to inclusion criteria and judged on sufficiency of data, 14 studies remained for data extraction, including 9 related to tooth-supported restorations (5594 proximal contacts) and 5 reporting on implant-supported restorations (1719 proximal contacts). All studies had moderate to high methodologic quality. A meta-analysis was performed to estimate the odds of developing OPCs with implant- compared with tooth-supported prostheses (95% CI; P<.05).
      The results (reported as odds ratios, ORs) indicated that an OPC was significantly more prevalent with implant-supported prostheses than with tooth-supported prostheses (OR, 2.46; 95% CI: 1.21-5.01; P=.013), although data were highly heterogeneous (τ2=0.40; I2=95.67%). Total estimates for developing OPCs were 41% (95% CI: 30% to 54%) for implant-supported prostheses and 22% (95% CI: 18% to 26%) for tooth-supported prostheses. OPCs were more prevalent on mesial proximal surfaces of implant-supported prostheses (OR, 2.38; 95% CI: 0.94-6; P=.066) and distal proximal surfaces of tooth-supported prostheses (OR, 1.94; 95% CI: 1.09-3.45; P=.024). No significant associations for developing OPCs were found with sex, age, arch, splinting of implants/teeth, region, adjacent tooth vitality, retention type, opposing dentition, occlusal force, parafunctional activities, or follow-up time as a continuous variable. Based on 3 studies, OPCs were estimated to increase 9% per year with implant-supported prostheses (OR, 1.09; 95% CI: 0.71-1.67), increasing continuously throughout the follow-up period. The total estimate of OPC gap dimension between implant-supported prostheses and adjacent natural teeth was 245.8 μm (95% CI: 86.4-405.3 μm) based on 2 studies.
      Within the limitations of this systematic review and meta-analysis, the authors concluded that OPCs were over twice as prevalent adjacent to implant-supported prostheses compared with tooth-supported prostheses. OPCs were twice as prevalent at the mesial compared with the distal proximal surfaces of implant-supported prostheses, and the opposite was found for tooth-supported prostheses. OPC dimensions progress over time from implant-supported restorations. Unfortunately, available data qualified as highly heterogeneous, thus necessitating future well-designed randomized clinical studies to validate the finding presented here. The authors cautioned that the limitations of the study included variations of effect size with different methods of clinical assessment and patient sampling across the studies. Although the initial publication search was designed to select articles conforming to established inclusion criteria, publication bias could not be ruled out because of inaccessibility of unpublished data.
      A third publication approached the PCL issue from yet a different perspective. Saber et al
      • Saber A.
      • Chakar C.
      • Mokbel N.
      • Nohra J.
      Prevalence of interproximal contact loss between implant-supported fixed prostheses and adjacent teeth and its impact on marginal bone loss: a retrospective study.
      investigated the prevalence of PCL between implant-supported fixed prostheses and adjacent teeth and its impact on marginal bone loss. Their objective was to identify potential risk factors to this clinical problem, citing that sound and stable interproximal contacts generally provide a protective influence on associated periodontal and peri-implant supporting tissues.
      This retrospective cohort study enrolled 83 recall-compliant patients (36 men; mean age, 57 years; range, 26-80 years) who received implant-supported fixed partial prostheses (119 cemented; 64 screw-retained; 121 mesial contacts; 62 distal contacts) at one facility from 2011 to 2017 and who met established inclusion and exclusion criteria. Interproximal contacts were clinically evaluated with 70-μm-thick waxed dental floss. Visual and periapical radiographic confirmation of PCL was accomplished. PCL was considered present if the floss passed without resistance. Plaque index, bleeding on probing, and radiographic bone loss around implants (radiographic baseline at prosthesis placement) were recorded at recall.
      The results revealed the prevalence of PCL between implant-supported fixed prostheses and adjacent teeth was 32.8% (95% CI: 26.0% to 39.6%), showing high concordance with visual and radiographic confirmations (kappa=.876; P<.001). Food impaction was identified in 14.2% of the open proximal contacts. The prevalence of mesial PCL (42.1%) was significantly greater than that of distal PCL (14.5%), and anterior PCLs were greater than those identified in posterior regions. When PCLs were observed, the associated marginal bone loss (0.73 ±0.78 mm) was significantly greater (P=.017) than that in the presence of sound interproximal contacts.
      PCLs occurred more frequently during loading phase (P=.05) and were significantly associated with patient complaints of open contact (P<.001) and food impaction (P=.001), as well as bleeding on probing on adjacent teeth (P=.024). Age, sex, smoking status, periodontal status, implant sites, and restoration type were not significantly associated with PCL or marginal bone loss (P>.05). In the presence of PCL, plaque index was significantly elevated on adjacent teeth (P=.048). Logistic regression showed that sites with PCL were 2.24 times more likely to present bleeding on probing (P=.028).
      The authors concluded that PCL occurred with one-third of implant-supported fixed partial prostheses studied, and contact was lost nearly 4 times more often at mesial prosthetic surfaces than at distal surfaces. Additionally, a positive relationship exists between PCL and marginal bone loss. Therefore, periodic patient follow-up is essential in managing this complication, and retrievable implant restorations may prove beneficial from a prosthesis repair perspective once contact is lost. Future research to identify etiologic factors related to PCL is needed.
      When 3 or more dental implants are placed in an edentulous arch to support a screw-retained fixed complete denture, the prosthesis may be designed to incorporate posteriorly directed cantilevers so that a complete compliment of posterior occlusal surfaces can be included. A lever system so designed may encounter high occlusal loading forces capable of transferring adverse biological and mechanical consequences to the system. Knowing the appropriate dimensional limits of cantilever length is critical for a stable and durable prosthesis design.
      One guideline for defining cantilever length was offered by Dr Charles English in 1990.
      • English C.E.
      Critical A-P spread.
      In general, Dr English indicated that cantilevers extending from a fixed complete-arch implant restoration should be no longer than 1.5 times the linear distance between a line connecting the distal implants and the most anterior implant. This linear measurement came to be known as the anterior-posterior (AP) spread. The use of AP spread in treatment planning and design has enjoyed a great deal of popularity, in part, because of its simplicity. Interested in justifying design criteria more soundly, Walter and Greenstein
      • Walter L.
      • Greenstein G.
      Utility of measuring anterior-posterior spread to determine distal cantilever length off a fixed implant-supported full-arch prosthesis: a review of the literature.
      critically analyzed available literature to assess the relationship between AP spread and other factors that may influence cantilever length for implant-supported fixed complete-arch restorations.
      A comprehensive search of the professional literature produced 11 human clinical trials. The limited number of relevant publications permitted each report to be addressed and critiqued directly. In general, the available data seemed to indicate that the relationship between AP spread and cantilever length is not linear and that many influences (beam theory, maxillary versus mandibular cantilever location, number, and distribution of supporting implants, prosthetic materials, and framework design) should be considered when determining cantilever length.
      The authors conclude that AP spread appears to be an empirical criterion, not one based on rigorous evidence or prospective clinical evaluations. Scientifically derived data that permit calculating cantilever length based solely on AP spread are lacking. Therefore, when designing cantilevers, the following should be considered:
      • anticipate occlusal loads and load distributions when selecting the size, number, and design of implants to be placed;
      • maximize implant distribution (AP spread) to reduce load per implant;
      • incorporate a cross-arch splinting design and rigid materials when working with complete-arch restorations;
      • develop the framework to have a cross-sectional design (I-beam effect) that resists loading; and
      • minimize cantilever length whenever possible, particularly in the maxilla.
      The authors also indicate that prostheses should be regularly monitored to assess structural integrity and occlusal accuracy. Implants and peri-implant tissues should be evaluated to ensure maintenance of biomechanical support.

      Prosthodontic materials

      High-performance polymers (HPPs) are semi-crystalline thermoplastic materials consisting of aromatic benzene molecules connected by ether or ketone functional groups. Polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) are HPPs used in dentistry that may help meet the demand for a metal-free restoration alternative because of good biocompatibility, heat resistance, solvent resistance, excellent electrical insulation, and favorable wear and fatigue characteristics. Their natural radiolucency makes them apparent in CT, magnetic resonance imaging (MRI), and radiographic imaging with minimal artifact interference. These materials have been applied in the fabrication of dental implants, implant healing abutments, removable partial denture frameworks and clasps, and fixed prosthodontic restorations. HPPs can be thermoplastically formed and CAD-CAM milled or printed.
      A concern prohibiting widespread application of HPPs in dentistry is their low translucency and unfavorable esthetic quality often requiring bonded resin or ceramic veneer additions. With this in mind, Gama et al
      • Gama L.T.
      • Duque T.M.
      • Özcan M.
      • Philippi A.G.
      • Mezzomo L.A.M.
      • Gonçalves T.M.S.V.
      Adhesion to high-performance polymers applied in dentistry: a systematic review.
      systematically reviewed the impact of surface pretreatments on the bond strength of common HPPs (PEEK and PEKK) and assessed postconditioning bond durability.
      The professional literature was searched through March 2019 to address the focused question, “Does surface pretreatments and/or bonding agent application impact the bond strength between composite veneering resin and HPP?” A total of 11 articles were included in the qualitative synthesis. A quantitative analysis was performed with data extracted from 8 of the 11 selected articles, which included a total of 5066 in vitro specimens. Risk of bias was assessed, and random effects meta-analyses were applied to estimate mean differences in shear bond strength (SBS) and tensile bond strength (TBS) relative to surface pretreatments and bonding agents after 24 hours and thermocycling.
      The results revealed that a low risk of bias was observed in most studies. Compared with nontreated controls, PEEK pretreatments associated with Visio.link (bredent GmbH) increased TBS by 26.72 MPa (95% CI: 19.69-33.76; P<.001) and increased SBS by 4.86 MPa (95% CI: 2.61-7.10; P<.001). Airborne-particle abrasion with 50-μm alumina improved SBS by 4.90 MPa (95% CI: 3.90-5.90; P<.001), and airborne-particle abrasion with silica-coated CoJet (3M ESPE) improved SBS by 4.51 MPa (95% CI: 1.85-7.18; P<.001). Compared with nontreated controls, Visio.link and Signum PEEK Bond (Kulzer GmbH) increased SBS by 33.76 MPa (95% CI: 18.72-48.81; P<.001) and 33.28 MPa (95% CI: 17.48-49.07; P<.001), respectively. No differences (P>.05) were found between Visio.link and Signum PEEK Bond or Monobond Plus/Heliobond (Ivoclar Vivadent AG). Similar results were observed for PEKK specimens.
      The authors concluded that the bond strength between HPP and veneering composite resin increased significantly with surface treatment. This was particularly true when PEEK was used. For PEKK, tribochemical silica coating applied in association with 98% sulfuric acid etching seemed to be the best way to strengthen the bond with the resin veneer. Limitations of this systematic review included methodological differences in the selected reports, differing specimen aging protocols, and a general lack of clinical data. The authors suggested that well-controlled clinical investigations in HPP bonding are necessary to establish a reliable HPP adhesive protocol for long-term bond stability.
      To continue the focus on HPPs, Paratelli et al
      • Paratelli A.
      • Perrone G.
      • Ortega R.
      • Gómez-Polo M.
      Polyetheretherketone in implant prosthodontics: a scoping review.
      present a scoping review to systematically map research reported in this area, as well as to identify any existing gaps in knowledge regarding PEEK material behavior when applied to implant restorations. Specifically, the authors formulated the following research question, “What is known from the literature about the application of PEEK in implant prosthodontics?” Relevant literature on PEEK in implant prosthodontics published through August 2018 was identified. Qualitative and quantitative syntheses were carried out for 13 original research studies.
      The results indicated that PEEK has been applied in the fabrication of implant-supported fixed restorations (43%), definitive and interim implant abutments (35%), implant abutment screws (15%), and implant overdenture retentive inserts (7%). Only 38% of the identified studies were clinical in nature, 15% were observational, and 47% were in vitro. In total, in vivo data on 162 restorations and in vitro data on 106 specimens were identified. The studies included did not permit the reliable estimation of long-term restoration survival or prosthetic component success rates.
      With respect to PEEK frameworks for implant-supported FPDs and single crowns, 2 case series, 2 uncontrolled clinical trials, and 2 in vitro studies lacking controls were identified. Failure of these restorations typically occurred adhesively between framework and veneering materials. From 4 in vivo reports on implant-supported fixed complete dentures, the mean survival over 12 months was 98.87%, and the mean success was 85.05%. Of the complications encountered, 64.28% were mechanical in nature (77.8% adhesive failures; 11.1% framework fractures; 11.1% discolorations), and 35.72% were biologic (soft-tissue lesions and unpleasant taste). Five reports identified on the use of PEEK for definitive or interim restorative abutments showed excellent success and survival rates up to 2 years in function. There were only 2 in vitro studies on PEEK implant abutment screws. Only 1 randomized clinical trial addressed PEEK round bar retention clips, and results indicated 100% success and survival over a short 6-month observation period.
      The authors concluded that given the paucity of evidence on the viability of PEEK as an implant-prosthodontic material, its use cannot yet be endorsed. Additionally, the lack of high-quality evidence suggests that undertaking a rigorous systematic review is not currently appropriate or necessary. Further laboratory and clinical research is needed to better appreciate this material’s suitability in implant dentistry specifically and prosthodontics in general. If used, suggested protocols for managing PEEK should be carefully followed to reduce the incidence of prosthodontic complications, bearing in mind that long-term outcomes remain uncertain.
      The growing attractiveness of zirconia for conventional fixed prosthodontic restorations relates to favorable mechanical properties, capacity for monolithic fabrication, and relative tooth color appearance. When tooth preparation provides adequate resistance and retention form, zirconia crowns may be luted with conventional cements. However, in instances of nonretentive tooth preparation, adhesive luting must be considered. Considering currently available processes, Steiner et al
      • Steiner R.
      • Heiss-Kisielewsky I.
      • Schwarz V.
      • Schnabl D.
      • Dumfahrt H.
      • Laimer J.
      • et al.
      Zirconia primers improve the shear bond strength of dental zirconia.
      evaluated how cement type and priming protocol affect the shear bond strength on zirconia ceramics.
      A total of 170 CAD-CAM–fabricated yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) Ø3.3×3.0-mm cylinders (Vita YZ T; VITA Zahnfabrik) were bonded to flat 31.0×7.0×5.0-mm zirconia ceramic plates. The zirconia surfaces were airborne-particle abraded (Al2O3; particle size 50 μm; 0.1-MPa pressure; 10-mm distance), ultrasonically cleaned, and assigned to 17 groups of 10 specimens each. Seven commercially available resin cements and 3 surface pretreatment protocols were used to bond cylinders to plates. Ten specimens in each cement group were pretreated with a universal primer (Signum Zirconia Bond I+II; Kulzer GmbH), 10 specimens per group were bonded without pretreatment, and 10 specimens per group were pretreated with system-specific zirconia primers recommended for 3 of the cements. In total, 170 bonded specimens were stored in water, thermocycled, and submitted to shear bond load-to-failure tests.
      The results indicated that mean shear bond strengths in the unprimed group showed large variations between 2.52 ±3.01 MPa and 33.15 ±7.35 MPa. Pretreatment with a universal primer significantly (P<.05) improved shear bond strengths in all groups ranging from 21.80 ±12.51 to 57.20 ±11.40 MPa. Compared with the unprimed group, system-specific primers also improved shear bond strengths significantly (P<.01). However, only one system-specific primer achieved a shear bond strength superior to the universal primer (P<.01). A statistical correlation of medium strength between fracture type and shear bond strength was demonstrated (P<.001), with cohesively fractured specimens demonstrating higher shear bond strengths (37.24 ±19.87 MPa) than adhesively fractured specimens (23.10 ±17.65 MPa). This correlation was significant (P<.001).
      Based on these findings, the authors offered several conclusions. Airborne-particle abrasion alone, as a surface pretreatment, was insufficient to optimize the shear bond strength with zirconia. Surface pretreatments with each of the tested zirconia primers enhanced the bond strength. Cement type has a relevant influence on shear bond strength with zirconia. Finally, the authors suggested that to predictably achieve high shear bond strengths to zirconia, the use of a strong bonding resin cement together with the MDP-containing universal primer is both supported by this in vitro experimentation and recommended.

      Periodontics, alveolar bone, and peri-implant tissues

      This year’s review covered topics relating to the etiology, assessment, and prevalence of periodontal disease; the systemic health conditions affecting the periodontium; periodontal treatment therapies; the soft tissues adjacent to teeth and implants; bone biology and medication-related osteonecrosis of the jaw; alveolar ridge preservation and alveolar bone augmentation techniques; and peri-implant diseases.
      An ongoing problem in the periodontal literature is the distorted interpretation or “spin” found in many periodontal literature abstracts which makes the research findings seem more favorable. Wu et al
      • Wu X.
      • Yan Q.
      • Fang X.
      • Hua F.
      • Shi B.
      • Tu Y.K.
      Spin in the abstracts of randomized controlled trials in periodontology and oral implantology: a cross-sectional analysis.
      performed an analysis of spin in abstracts of randomized controlled trials (RCTs) in periodontology and implant dentistry and explored its associated factors and influence on the subsequent literature. PubMed was searched to identify recent RCTs in periodontology and implant dentistry, whose primary outcome was found to be not significant statistically. Spin in abstracts was assessed and categorized according to predetermined spin strategies. The associations between study characteristics and the presence or severity of spin were analyzed with multivariable logistic regressions.
      They determined that of the 196 abstracts included, 69.9% had demonstrated some type of spin. Of these, 29.1% demonstrated spin in the results section, and 64.3% had spin in the conclusion section. The main spin strategies in the results and conclusion sections were focusing on secondary outcomes and within-group comparisons. Understanding that RCTs are designed to test the null hypothesis for primary outcomes, reporting of secondary outcomes in the results and conclusion sections is not statistically supported.
      Unfortunately, abstracts with spin also had adverse scientific influence on subsequent publications. Of the 34 subsequent inappropriate citations, 18 citations (52.9%) interpreted nonsignificant results as significant, 12 citations (35.3%) described irrelevant topics, and 4 citations (11.8%) claimed efficacy or recommended treatments based on nonsignificant results.
      The presence of spin was also associated with the number of centers. Single-center studies were more likely to present spin in abstracts than multicenter reports. Studies in implant dentistry were associated with decreased severity of spin in comparison to periodontal tissue treatment.
      The authors concluded that the frequency of spin is relatively high among published RCT abstracts in periodontology and implant dentistry. Findings reported in these abstracts need to be interpreted with caution. The danger for the field of periodontics and implant dentistry is that the presence of spin weakens the importance of primary outcomes, distorts the initial aims of trials, and most importantly misleads readers in clinical decision-making. Responsibility also lies within the editorial review process. Abstract reporting should be direct, clear, and transparent. For readers, clinical decision-making should base on access and reading of full texts and not only the abstracts.

      Periodontal disease prevalence, etiology, and treatment

      Periodontitis is an inflammatory disease triggered by a microbial dysbiosis that affects the supporting tissues, eventually leading to tooth loss when untreated. Viruses are also present within the oral cavity. But there is limited knowledge about their relationship to periodontal disease. Gao et al
      • Gao L.
      • Kang M.
      • Zhang M.J.
      • Reza Sailani M.
      • Kuraji R.
      • Martinez A.
      • et al.
      Polymicrobial periodontal disease triggers a wide radius of effect and unique virome.
      introduced a new mouse model of periodontal disease to examine the effects of a polymicrobial infection on periodontal ligament (PDL), changes in bone loss, the host immune response, and the microbiome or virome by using shotgun sequencing. Periodontal pathogens were used as the polymicrobial oral inoculum in BALB/cByJ mice. As expected, the polymicrobial infection triggered significant alveolar bone loss, a heightened antibody response, and an elevated cytokine immune response. Most importantly, they found a significant shift in viral diversity and virome composition along with widening of the PDL space. Changes in the PDL space were present at sites far away from the site of insult, indicating that the polymicrobial radius of effect extends beyond the bone loss areas. Associations were found between bone loss, specific viral and bacterial species, immune genes, and PDL space changes. These findings may have significant implications for the treatment of periodontal disease which has limited research into antiviral therapies.
      For effective treatment of periodontal disease, an accurate diagnosis of active disease before destruction of the periodontium occurs is required. In a systematic review, Arias-Bujanda et al
      • Arias-Bujanda N.
      • Regueira-Iglesias A.
      • Balsa-Castro C.
      • Nibali L.
      • Donos N.
      • Tomas I.
      Accuracy of single molecular biomarkers in saliva for the diagnosis of periodontitis: a systematic review and meta-analysis.
      conducted a systematic review examining the accuracy of single molecular biomarkers for the diagnosis of periodontitis in the saliva. Articles on molecular biomarkers in saliva providing a binary contingency table (or sensitivity and specificity values and group sample sizes) in individuals with clinically diagnosed periodontitis were considered eligible for inclusion. The methodological quality for each article was assessed. Meta-analyses were performed with the Hierarchical Summary Receiver Operating Characteristic model. They found that meta-analysis was possible for only 5 of the 32 biomarkers studied. The highest values of sensitivity for the diagnosis of periodontitis were obtained for IL1β (78.7%), followed by MMP8 (72.5%), IL6, and hemoglobin (72.0% for both molecules); the lowest sensitivity value was for MMP9 (70.3%). In terms of specificity estimates, MMP9 had the best result (81.5%), followed by IL1β (78.0%) and hemoglobin (75.2%); MMP8 had the lowest specificity (70.5%). This review demonstrated that MMP8, MMP9, IL1βb, IL6, and hemoglobin are salivary biomarkers with good capability to detect periodontitis in systemically healthy patients. Currently, MMP8 and IL1β are the most researched biomarkers in the field, both showing clinically fair effectiveness for the diagnosis of periodontitis.
      Azurocidin is a neutrophil-derived protein in gingival crevicular fluid (GCF) which may correlate with the presence of active periodontal disease. Nalmpantis et al
      • Nalmpantis D.
      • Gatou A.
      • Fragkioudakis I.
      • Margariti A.
      • Skoura L.
      • Sakellari D.
      Azurocidin in gingival crevicular fluid as a potential biomarker of chronic periodontitis.
      conducted a study to evaluate azurocidin as a potential biomarker for chronic periodontitis. One hundred and one patients participated in the study, divided into 2 groups. Forty-eight were included in the periodontally healthy group (HP), and 53 in the chronic periodontitis group (CP). Clinical indices included probing depth (PD), recession (REC), clinical attachment level (CAL), bleeding on probing (BOP), and plaque (PL). Pooled GCF samples were collected with paper strips, and the levels of azurocidin were analyzed with ELISA. Statistical comparisons were performed with nonparametric tests (Mann-Whitney) at the 0.05 level. They demonstrated that while demographic data were comparable between the 2 groups, clinical parameters and the levels of azurocidin were statistically significantly higher in the CP group than those in the HP group. Quantitative data from ELISA demonstrated a high diagnostic accuracy of azurocidin. Azurocidin in GCF should be considered a promising biomarker for periodontal disease.
      Being able to make an immediate chairside determination of a patient’s periodontal diagnosis would be greatly beneficial. Arweiler et al
      • Arweiler N.B.
      • Marx V.K.
      • Laugisch O.
      • Sculean A.
      • Auschill T.M.
      Clinical evaluation of a newly developed chairside test to determine periodontal pathogens.
      conducted a controlled clinical trial to determine clinical applicability of a newly developed chairside bacterial test (CST) for the most relevant periodontal pathogens. Examining 125 participants (100 with periodontitis, 25 healthy), 2 sulcus fluid samples each were collected and pooled for further analysis. Samples were analyzed with CST, and results (positive signals for every pathogen and control) were visually detected by eye. As a reference, quantitative polymerase chain reaction (qPCR) was performed. This CST was able to detect Treponema denticola (T. denticola), Tannerella forsythia (T. forsythia), Porphyromonas gingivalis (P. gingivalis), Prevotella intermedia (P. intermedia), and Aggregatibacter actinomycetemcomitans (A. a.). The sensitivities of CST to qPCR were as follows: T. denticola (91.3%); T. forsythia (86.3%); P. gingivalis (83.8%); P. intermedia (85.7%), and A. a. (100%). Regarding the clinical diagnosis, the CST assay and the qPCR method reached a sensitivity of 87.82% and 94%, respectively. The specificity for both methods was 100%. The authors concluded that this newly developed CST can detect 5 typical periodontal pathogens with a somewhat lower sensitivity toward qPCR.
      Advancements in ultrasound technologies have allowed for the measurement of periodontal structures without the use of ionizing radiation. Tattan et al
      • Tattan M.
      • Sinjab K.
      • Lee E.
      • Arnett M.
      • Oh T.J.
      • Wang H.L.
      • et al.
      Ultrasonography for chairside evaluation of periodontal structures: a pilot study.
      evaluated the correlation and accuracy of ultrasound in measuring periodontal dimensions, compared with direct clinical and CBCT methods. Using a 24-MHz ultrasound probe prototype, specifically designed for intraoral use, periodontal soft-tissue dimensions and crestal bone levels were measured at 40 teeth and 20 single missing tooth spaces from 20 patients scheduled to receive a dental implant surgery. The ultrasound images were interpreted by 2 calibrated examiners. Ultrasound readings were compared with direct clinical and CBCT readings by using ICC and Bland-Altman analysis. Four parameters were measured for teeth (interdental papilla height, mid-facial soft-tissue height, mucosal thickness, and crestal bone level), and 2 parameters for edentulous ridges (soft-tissue height and mucosal thickness). The mean difference in mucosal thickness (tooth) between the ultrasound and direct readings was −0.015 mm without statistical significance. Examiner agreement between ultrasound and CBCT ranged from 0.654 to 0.849 among the measured parameters. The mean differences between ultrasound and CBCT range from −0.213 to 0.455 mm, without statistical significance. Ultrasonic imaging can be valuable for accurate and real-time periodontal diagnosis without concerns about ionizing radiation.
      Notch signaling pathway plays an important role in osteoblast differentiation and bone remodeling. “Notch signaling” controls osteoclastogenesis indirectly, by managing the expression level of osteoclastogenic factors on osteoblasts’ surface, or directly by regulating osteoclasts’ differentiation. Recent studies have shown Notch signaling in bone remodeling that is complex and cell dependent. Mijailovic et al
      • Mijailovic I.
      • Nikolic N.
      • Djinic A.
      • Carkic J.
      • Milinkovic I.
      • Peric M.
      • et al.
      The down-regulation of Notch 1 signaling contributes to the severity of bone loss in aggressive periodontitis.
      analyzed the expression of Notch signaling molecules, bone remodeling mediators, and proinflammatory cytokines in patients with periodontitis and determined their potential correlations. This study included 130 individuals: 40 with aggressive periodontitis (AP group), 40 with CP group, and 50 periodontally healthy controls. Total RNA was extracted from gingival crevicular fluid samples, and relative gene expression of investigated molecules (Notch 1, Notch 2, Jagged 1, Hes 1, Hey 1, TNF-α, IL-17, RANKL, and OPG) was determined by reverse transcriptase real-time polymerase chain reaction (RT-qPCR). In the AP group, a significant increase of Notch 2, TNF-α, IL-17, and RANKL and a significant decrease of Notch 1 and Jagged 1 expression were observed compared with the control group. Notch 2 and RANKL were also overexpressed in the CP group compared with controls. Significant correlations were observed in the AP group between expression levels of the analyzed genes. These findings implicate Notch 2 overexpression in the pathogenesis of bone resorption in aggressive and chronic periodontitis. The downregulation of Notch 1 and Jagged 1 and loss of their osteoprotective function might cause a more excessive osteoclast formation and contribute to greater osteolysis in aggressive periodontitis.

      Periodontal diseases and systemic health relationships

      Periodontitis has been identified as a moderate but independent risk factor for cardiovascular (CV) disease and progression. Schulz et al
      • Schulz S.
      • Schlitt A.
      • Hofmann B.
      • Schaller H.G.
      • Reichert S.
      Periodontal pathogens and their role in cardiovascular outcome.
      studied the effect of subgingival colonization with selected periodontal pathogens on the occurrence of further adverse CV events in a cohort of patients with CV disease. The prevalence of severe periodontitis, including the detection of numerous periodontal pathogens, was analyzed in 1002 patients with CV disease. Periodontal pathogens detected included A. a., P. gingivalis, P. intermedia, T. forsythia, T. denticola, Peptostreptococcus micros, Fusobacterium nucleatum (F. nucleatum), Campylobacter rectus, Eubacterium nodatum, Eikenella corrodens (E. corrodens), Capnocytophaga sputigena, Capnocytophaga gingivalis, and Capnocytophaga ochracea. The prognostic impact of periodontal pathogens for combined CV endpoint (stroke/TIA, myocardial infarction, CV death, death from stroke) was evaluated after a 3-year follow-up period. Hazard ratios (HRs) were adjusted for established CV risk factors applying Cox regression. They found that the decreased occurrence of E. corrodens was shown to be an independent predictor for adverse CV events after 3 years of follow-up. This unique finding implies that control of a recurrence of E. corrodens was associated with a reduced risk of adverse CV events in patients with CV disease. The pathophysiological background underlying this association should be investigated in further studies.
      Periodontitis significantly increases the risk of diabetic complications. Impaired cardiac function has likewise been demonstrated to be a comorbidity. Wang et al
      • Wang Y.
      • Liu H.N.
      • Zhen Z.
      • Pelekos G.
      • Wu M.Z.
      • Chen Y.
      • et al.
      A randomized controlled trial of the effects of non-surgical periodontal therapy on cardiac function assessed by echocardiography in type 2 diabetic patients.
      conducted a clinical trial investigating the effects of periodontal therapy on cardiac function in patients with type 2 diabetes mellitus (T2DM) and periodontitis. Fifty-eight participants with T2DM and periodontitis were randomly allocated to a treatment group (n=29) receiving nonsurgical periodontal therapy or a control group (n=29) having only oral hygiene instructions with delayed periodontal treatment until completion of this 6-month study. The left ventricle (LV) diastolic function was assessed by echocardiography with the tissue Doppler imaging index (E/e' ratio); and LV hypertrophy was evaluated by LV mass index (LVMI). Blood samples were collected for biochemical analyses. The intention-to-treat analysis showed that periodontal treatment significantly reduced the E/e' ratio by 1.66, along with marked improvement of periodontal conditions. LVMI was not altered at the 6-month follow-up. The serum levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP), a cardiac stress biomarker, C-reactive protein, and interleukin-6 decreased numerically, but this difference did not reach statistical significance. This present study provided evidence that nonsurgical periodontal therapy may improve cardiac diastolic function in patients diagnosed with type 2 diabetes with periodontitis.
      The effect of periodontitis severity levels on acute myocardial infarction (AMI) remains unexplored. Gomes-Filho et al
      • Gomes-Filho I.S.
      • Coelho J.M.F.
      • Miranda S.S.
      • Cruz S.S.
      • Trindade S.C.
      • Cerqueira E.M.M.
      • et al.
      Severe and moderate periodontitis are associated with acute myocardial infarction.
      investigated the association between levels of periodontitis severity (exposure) and AMI (outcome). In this case-control study, of 621 participants, 207 individuals treated in the emergency department of a hospital diagnosed with a first AMI event were compared with 414 individuals without a diagnosis of AMI. Levels of periodontitis severity were determined with the American Academy of Periodontology criteria. A conditional logistic regression analysis was performed, and ORs and CIs were obtained. The adjusted association measurements showed a positive association between both severe and moderate periodontitis. It demonstrated that among those with moderate and severe periodontitis, the chance of having AMI was approximately 2 to 4 times greater than among those without periodontitis. The findings demonstrated that there is an association between the severity of the periodontal condition and AMI, suggesting a possible relationship among the levels of periodontitis severity and the cardiovascular condition.
      It is well established that diabetes can influence the incidence and severity of periodontal disease. Continuing research is also examining the effect of treatment of periodontitis upon systemic inflammation. A study conducted by Preshaw et al