Journal of Prosthetic Dentistry

Minimally invasive lithium disilicate ceramic veneers fabricated using chairside CAD/CAM: A clinical report

M. Schmitter, B. Seydler B — 2012-02-01

This clinical report describes the use of modern CAD/CAM technology combined with a conventional impression technique to treat a malformed tooth with ceramic veneer in a single appointment. A thin veneer (0.4 mm) made of lithium disilicate ceramic was used to correct the shape of the malformed tooth with a minimally invasive preparation using a chairside CAD/CAM system. Thus the treatment can be performed during one appointment. To facilitate the CAD/CAM process and fabrication of the veneer, a scanable model fabricated on a modified gypsum definitive cast was used. The malformed tooth was corrected on the cast by use of a composite resin and an impression was then made. This trimmed impression was used intraorally during the scanning process to facilitate fabrication of the veneer.

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2012-02-01

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A three-appointment alternative treatment protocol for fabricating an implant-supported milled bar overdenture

Wei-Shao Lin, Erdem Özdemir, Dean Morton — 2012-02-01

This article describes an alternative impression technique for the fabrication of an implant-supported bar overdenture using the duplicated satisfactory interim denture as a custom tray for the implant-level impression. The primary advantage of this technique is that all the information needed for the definitive prosthesis fabrication is obtained from the interim denture and then transferred to the laboratory in a single appointment. However, this technique may be contraindicated for severely misaligned implants that require extensive reduction of the duplicated denture.

Effect of axial wall modification on the retention of cement-retained, implant-supported crowns

2012-02-01

Statement of problem: Compromised angulation of implants may result in abutment preparation that is less than ideal. Compromised abutment preparation may affect the retention of implant-retained crowns. Purpose: The purpose of this study was to investigate the effect of 5 implant abutment designs on the retention of cement-retained crowns by varying the number and position of the axial walls. Material and methods: Five prefabricated abutments were attached to an implant analog and embedded in an acrylic resin block. The first abutment was left intact without modification. Axial walls were partially removed from the remaining abutments to produce abutments with 3 walls, 2 adjacent walls, 2 opposing walls, and 1 wall. Five crowns were made for each group. The screw access channel for the first abutment was completely filled with composite resin and the rest were partially filled. The retentive surface area of each abutment was calculated. Crowns were cemented with zinc phosphate cement. Tensile force was applied to separate the castings from the abutments. Peak load to dislodgment was recorded. A 1-way ANOVA was used to test for a significant difference followed by the Tukey Honestly Significant Difference test (α=.05). Results: The abutment with 2 opposing axial walls had significantly higher retention than that of all other groups (F=149.9, df =24, P<.001). The abutment with 3 walls exhibited the second highest retention and was significantly greater than abutments with 2 adjacent walls, 1, and 4 walls. Abutments with 2 adjacent walls and 1 wall were not significantly different from each other. The unmodified abutment with 4 walls exhibited the lowest retention despite having a large retentive surface area. Conclusions: The retention of cemented crowns on implant abutments is influenced by the number and position of axial walls.

Effect of different grit sizes of diamond rotary instruments for tooth preparation on the retention and adaptation of complete coverage restorations

Ya-qing Li, Hui Wang, Ying-jie Wang, Ji-hua Chen — 2012-02-01

Statement of problem: Internal adaptation and retention are important factors for the longevity of crown restorations. However, how tooth surface roughness associated with diamond rotary cutting instruments affects the retention and internal adaptation of complete coverage restorations remains unknown. Purpose: This study evaluated the relationship between the surface roughness of prepared teeth and the internal adaptation and retention of complete coverage restorations after preparation with diamond rotary cutting instruments of different grit sizes. Material and methods: Ninety-two extracted human teeth were divided into 4 groups and assigned to different final grit sizes of the diamond rotary instruments used for preparation following a grit decreasing sequence from coarse (125 to 150 μm), to medium (106 to 125 μm), to fine (53 to 63 μm), to extra fine (20 to 30 μm). After preparation, the surface roughness of 32 teeth was measured with a profilometer. The other 60 teeth were prepared as abutments, with 28 of these teeth used to measure microleakage and cement thickness. The remaining 32 teeth were used to test the retention between teeth and nickel-chromium alloy crowns with a universal testing machine. The data were analyzed with a 1-way ANOVA and Fisher's LSD post hoc multiple comparison tests to determine significant intergroup differences in surface roughness and retention force (α=.05). Microleakage scores and cement thickness were analyzed with the Kruskal-Wallis rank sum test; these were also conducted as multiple comparison tests (α=.05). Results: The teeth prepared with the coarsest diamond rotary cutting instruments showed the highest mean surface roughness (SD) (4.8 (0.4) μm), and those prepared with the finest diamond rotary instruments had the lowest mean cement thickness (0.5 (1.2) μm; P<.001 when compared to teeth in the coarse group). The finer surfaces showed less microleakage (P =.03). However, no significant differences in retention were found (P=.19) across the groups. Conclusions: Teeth prepared with the finer grit rotary instruments have smoother tooth surfaces and crown restorations with better internal adaptation. The grit size of the diamond rotary cutting instruments does not affect the removal force between the complete coverage crown and the prepared tooth.

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2012-02-01

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Effect of surface conditioning with airborne-particle abrasion on the tensile strength of polymeric CAD/CAM crowns luted with self-adhesive and conventional resin cements

2012-02-01

Statement of problem: Adhesively bonded, industrially polymerized resins have been suggested as definitive restorative materials. It is claimed that such resins present similar mechanical properties to glass ceramic. Purpose: The purpose of this study was to assess the tensile strength of polymeric crowns after conditioning with 2 different protocols: luted with self-adhesive or with conventional resin cements to dental abutments. Material and methods: Human teeth were prepared for crowns and divided into 13 groups (N=312, n=24 per group). Polymeric crowns were CAD/CAM fabricated and divided into 3 groups depending on different surface conditioning methods: A) No treatment, B) airborne-particle abrasion with 50 μm alumina, and C) airborne-particle abrasion with 110 μm alumina. Thereafter, the crowns were luted on dentin abutments with the following cements: 1) RXU (RelyX Unicem, self-adhesive), 2) GCM (G-Cem, self-adhesive), 3) ACG (artCem GI, conventional), and 4) VAR (Variolink II, conventional). Glass ceramic crowns milled and cemented with dual-polymerized resin cement (Variolink II) served as the control group. The tensile strength was measured initially (n=12) and after aging by mechanical thermocycling loading (1 200 000 cycles, 49 N, 5°C to 50°C) (n=12). The tensile strength (MPa) of all crowns was determined by the pull-off test (Zwick/Roell Z010; Ulm, Germany, 1mm/min). Subsequently, the failure types were classified. Data were analyzed with 2-way and 1-way ANOVA followed by a post hoc Scheffé test and t test (α=.05). Results: No adhesion of the tested cements was observed on unconditioned polymeric CAD/CAM crowns and those luted with VAR. Among the tested cements, GCM showed significantly higher values after airborne-particle abrasion with 110 μm (initial: 2.8 MPa; after aging: 1 MPa) than 50 μm alumina (initial: 1.4 MPa; after aging: 0 MPa). No significant effect was found between 50 and 110 μm particle size alumina in combination with the other 2 cements. After aging, the tensile strength of the crowns luted with GCM (50 μm: 0 MPa and 110 μm: 1 MPa) and ACG (50 μm: 1 MPa and 110 μm: 1.2 MPa) was significantly lower than those luted with RXU (50 μm: 1.9 MPa and 110 μm: 2 MPa). All airborne particle abraded polymeric CAD/CAM crowns (initial: 1.4-2.8; 0-2 MPa) showed significantly lower tensile strength values than the control group (initial: 7.3 MPa; after aging: 6.4 MPa). Although with all polymeric specimens, failure type was adhesive between the cement and the crowns, the control group showed exclusively cohesive failures within the ceramic. Conclusions: Airborne-particle abrasion before cementation of polymeric CAD/CAM crowns minimally improved the tensile strength. Both the failure types and the tensile strength values of adhesively luted glass ceramic crowns showed superior results to adhesively cemented polymeric ones. Although the tensile strength results were low, crowns cemented with RXU showed, after aging, the highest tensile strength of all other tested groups.

Correction

2012-02-01

The article entitled, “The effect E-Glass fibers and acrylic resin thickness on fracture load in a simulated implant-supported overdenture prosthesis” by Renato S. Fajardo, DDS, MSc, MPH, Phd, Lisa A. Pruitt, PhD, Frederick C. Finzen, DDS, Grayson W. Marshall, DDS, MPH, PhD, Sukhmani Singh DDS, and Donald A. Curtis, DMD, published in the December 2011 issue of the Journal, contained an error with respect to the spelling of the fifth author's name. The author's name, printed as Sukhmony Singh, should have appeared as Sukhmani Singh.

The effect of phosphoric acid pre-etching and thermocycling on self-etching adhesive enamel bonding

James L. Sheets, Charles W. Wilcox, Wayne W. Barkmeier, Martha E. Nunn — 2012-02-01

Statement of problem: When inserting a resin-bonded prosthesis, it is not known whether pumicing, rinsing, and using a self-etching primer (SE) on prepared surfaces is sufficient or whether the use of an additional conventional acid etchant is warranted due to the increased time and risk of contamination. Purpose: The purpose of this study was to evaluate the effects of pre-etching with phosphoric acid (PA) and thermocycling (TC) on the enamel shear bond strength (SBS) of an autopolymerizing adhesive system on ground enamel. Material and methods: Human teeth were embedded in phenolic rings with methyl methacrylate resin, and their enamel surfaces were ground flat to a 600 grit surface. The teeth were then divided into 4 subsets (n=22): 1) PSN, PA pre-etch with SE, no TC; 2) PST, PA pre-etch with self-etching primer and TC; 3) SEN, self-etching primer alone, no TC; and 4) SET, self-etching primer and TC. A multifactorial study design was used to evaluate 2 factors (pre-etching with PA and TC) at 2 levels (presence or absence) by grouping different subsets. Pre-etch consisted of teeth being etched for 30 seconds with PA, rinsed, re-etched, and rinsed. Self-etching consisted of 60 seconds with ED Primer. Rods of Rexillium III, airborne-particle abraded with 50 μm aluminum oxide, were bonded to enamel surfaces with Panavia 21 OP under a 19.6 N load. Thermocycling consisted of alternating between water baths of 5 ± 2°C and 55 ± 2°C for 5000 cycles. Shear bond strength (SBS) was determined by loading the specimens to failure at a crosshead speed of 1 mm/min. Mean values were analyzed with a 2-way ANOVA (factors were surface treatment and TC) at α=.05. Results: Pre-etching with phosphoric acid showed greater SBS to enamel (P=.028) than the self-etching primer alone. Thermocycling did not have a significant effect (P=.424). Conclusions: There was a significant difference in SBS between pre-etching enamel surfaces with phosphoric acid in addition to the self-etching primer and using the self-etching primer exclusively. Thermocycling did not significantly affect SBS.

Histologic studies on osseointegration: soft tissues response to implant surfaces and components. A review

2012-02-01

Piattelli A, Pontes AE, Degidi M, Iezzi G. Dent Mater 2011;27:53–60.

Wear of ceramic and titanium ball attachments in subjects with an implant-retained overdenture: a controlled clinical trial

Adrian E. Büttel, Heinz Lüthy, Pedram Sendi, Carlo P. Marinello — 2012-02-01

Statement of problem: Loss of retention of implant-retained overdentures due to wear of the patrix or matrix of the attachment system is a common clinical problem. Purpose: The purpose of this controlled clinical trial was to compare the wear of ceramic and titanium ball attachments and their corresponding gold matrices after 1 year of clinical function in subjects with implant-retained mandibular overdentures. Material and methods: Forty subjects who had been treated with a 2-implant-retained overdenture received either 2 ruby ball attachments (20 subjects) or 2 titanium ball attachments (20 subjects). The diameter of the ball attachments and the thickness of the matrix were measured optically before insertion and after 1 year of clinical function. Differences among groups were then compared with the Wilcoxon rank sum test (α=.05). To estimate any correlation between clinical parameters and wear, the Spearman rank test was used. Results: There was no significant difference (P=.73) in the median wear of ball attachments for the titanium group (5.3 μm; median 1.3 μm) and for the ceramic group (1.3 μm; median 1.3 μm). In the ceramic group, a fracture rate of 30% was observed. The mean wear of the matrices in the titanium group was 3.1 μm (median 6.8 μm) and in the ceramic group 2.1 μm (median 3.4 μm), P=.01. No correlation was found between ball attachment wear and matrix insert wear (Spearman rank test). Wear of matrices was weakly correlated with an increase in divergence between implant axes in the sagittal plane (P=−.28 and P=.021). Ball attachment wear was associated with an increase in divergence between matrix axes in the sagittal plane (P=−.34 and P=.047). Conclusions: Matrices on ceramic ball attachments showed less wear than those placed on titanium ball attachments. However, the use of ruby ball attachments cannot be recommended because of a high fracture rate.

Correction

2012-02-01

The article entitled “Comparative radiopacity of ceramics and metals with human and bovine dental tissues” by Gurel Pekkan, DDS, PhD, Keriman Pekkan, MSc, PhD, Mujgan Gungor Hatipoglu, DDS, PhD, and Suleyman Hakan Tuna DDS, PhD, published in the August 2011 issue of the Journal, contained an error in the second author's title. The author's title should have appeared as Keriman Pekkan, Assistant Professor, Department of Ceramic and Glass, Faculty of Fine Arts, Dumlupinar University.

Cytotoxicity of denture base and hard chairside reline materials: A systematic review

2012-02-01

Statement of problem: Adverse reactions to the materials used for the fabrication and reline of removable denture bases have been observed. Purpose: The purpose of this study was to systematically review the published literature on the cytotoxicity of denture base and hard reline materials. Material and methods: MEDLINE via PubMed, Google Scholar, and Scopus databases for the period January 1979 to December 2009 were searched with the following key words: (biocompatibility OR cytotoxic* OR allergy OR “burning mouth” OR “cell culture techniques”) AND (“acrylic resins” OR denture OR monomer OR relin* OR “denture liners”). The inclusion criteria included in vitro studies using either animal or human cells, in which the cytotoxicity of the denture base and hard chairside reline resins was tested. Studies of resilient lining materials and those that evaluated other parameters such as genotoxicity and mutagenicity were excluded. Articles published in the English language and in peer-reviewed journals focusing on the cytotoxicity of these materials were reviewed. Results: A total of 1443 articles were identified through the search. From these, 20 studies were judged to meet the selection criteria and were included in the review. In the majority of the studies, continuous cell lines were exposed to eluates of specimens made from the materials, and mitochondrial activity was used to estimate cell viability. The tested acrylic resins were grouped according to 5 major categories: (1) heat-polymerized; (2) microwave-polymerized; (3) autopolymerizing; (4) light-polymerized; and (5) hard chairside reliners. Conclusions: This review provided some evidence that the heat-polymerized resins showed lower cytotoxic effects than autopolymerizing denture base acrylic resins and light or dual polymerized reline resins. However, because of the large number of variables in the reviewed literature, a definitive conclusion could not be drawn.

Planning implant positions for an auricular prosthesis with digital data

2012-02-01

The esthetic result of an auricular prosthesis is influenced by the position of the prosthesis incorporating the implants. The entire surface of the patient's head is captured by means of a conventional computed tomography (CT). The digital data are used to mirror the contralateral unimpaired ear for restoration of the impaired side. The virtual ear is integrated into a template covering the auricular defect and indexed to the nasal area with computer-aided technology (CAD/CAM). This virtual template is converted into an acrylic resin template. With that the surgeon and the anaplastologist should determine the optimal implant position of the auricular prosthesis.

Use of a vinyl polysiloxane (VPS) indicator material to block out proximal undercuts during fabrication of fixed provisional restorations

Christopher A. Barwacz, Ali Fakhry — 2012-02-01

Before fabricating provisional fixed restorations, the clinician is often required to eliminate natural and/or prosthetic proximal undercuts on adjacent teeth. This approach facilitates the retrieval of the provisional restoration during its fabrication without undue discomfort to the patient and/or risk of distortion or fracture.

The effect of different adhesive materials on retention of maxillary complete dentures

2012-02-01

Figueiral MH, Fonseca PA, Pereira-Leite C, Scully C. Int J Prosthodont 2011;24:175–7.

Template to determine the position and angulation of the abutment screw channel for implant-supported, cement-retained restorations

Julia Lautensack, Volker Weber, Stefan Wolfart — 2012-02-01

Implant-supported crowns and partial fixed dental prostheses are retained on the abutment by either cement or a screw. The primary advantages of cement-retained restorations are better occlusal function and improved esthetics because of the lack of visible screw-access openings. The disadvantage is limited retrievability of the prosthesis in the event of screw loosening.

Survival rates of teeth, implants, and double crown-retained removable dental prostheses: a systematic literature review

2012-02-01

Koller B, Att W, Strub JR. Int J Prosthodont 2011;24:109–17.

An alternative direct technique for the fabrication of an implant-supported, screw-retained fixed interim restoration

Burak Yilmaz, Edwin McGlumphy, Bradley Purcell — 2012-02-01

The interim implant restoration is an essential part of implant treatment, particularly in the anterior region. Various types of interim restorations have been described, such as soft tissue and/or tooth-supported removable prostheses, tooth-supported fixed prostheses, and implant-supported fixed restorations. The purpose of fabricating an interim restoration involves the esthetic and functional replacement of the missing dentition until a definitive prosthesis is fabricated and placed. Interim restorations can also be used for shaping and preserving the subgingival emergence profile of the periimplant soft tissue.

Slow crack growth and reliability of dental ceramics

2012-02-01

Gonzaga CC, Cesar PF, Miranda WG Jr, Yoshimura HN. Dent Mater 2011;27:394–406.

News and Notes

2012-02-01

All items for this section must be in the Editor's office 10 weeks before month of issue.

Editorial Board

2012-02-01

Sponsoring Organizations and Liaisons

2012-02-01

Information for Authors

Carol A. Lefebvre — 2012-02-01

Authors must adhere to the Journal guidelines, which are provided to ensure the expeditious processing of manuscripts. Complete information on manuscript submission may be found at http://journals.elsevierhealth.com/periodicals/ympr. Failure to follow Journal guidelines may result in the rejection of manuscripts or delays in the review process and publication.

Information for Readers

2012-02-01

If you have questions or comments regarding original articles and editorial management, please contact: Dr Carol A. Lefebvre, Georgia Health Sciences University College of Dental Medicine, 1120 15th St, GC-3094, Augusta, GA 30912-1255, Telephone: (706) 721-4558; Fax: (706) 721-4571.