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Adjunct Professor, The Ohio State University, College of Dentistry, Division of Restorative and Prosthetic Dentistry, Columbus, OhioSenior Lecturer, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, SwitzerlandSenior Lecturer, Department of Restorative, Preventive and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland
Research Assistant, The Ohio State University, College of Dentistry, Division of Restorative and Prosthetic Dentistry, Columbus, OhioResident, Ankara University Faculty of Dentistry Department of Prosthodontics, Ankara Turkey
Corresponding author: Dr Samir Abou-Ayash, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Freiburgstrasse 7, CH-3010 Bern, SWITZERLAND
Senior Lecturer, Section for Digital Implant- and Reconstructive Dentistry [DIRecD], Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland
This clinical report describes the rehabilitation of the maxillary arch of a partially edentulous patient with idiopathic root resorption, limited interarch distance, and a high smile line. Four implants were placed to provide a screw-retained fixed partial denture. The esthetic and functional challenges of a high smile line and limited interarch distance were addressed by using a combination of conventional and digital implant treatment technologies.
Idiopathic external cervical root resorption is a rare condition with predisposing factors that have not yet been clearly elucidated. The condition may require extensive rehabilitation,
Computer-aided design and computer-aided manufacturing (CAD-CAM) technology can be used to facilitate the treatment of patients with implant-supported prostheses,
including the fabrication of diagnostic and surgical guides, the manufacturing of implant abutments, and the fabrication of implant-supported prostheses.
Interim prostheses can also be fabricated by using CAD-CAM technologies, and CAD-CAM processed polymethyl methacrylate (PMMA) resin has been used for the fabrication of interim fixed implant-supported prostheses.
This clinical report describes the combined use of digital and conventional technologies to treat the maxillary arch of a patient with idiopathic root resorption, a high smile line, and limited interocclusal space. Treatment planning and execution were facilitated with the aid of CAD-CAM technology and contemporary restorative materials.
Clinical report
A 36-year-old woman presented to the Dental Faculty Practice at The Ohio State University College of Dentistry with the chief complaint that “I am losing my upper teeth and cannot chew well.” She reported no systemic health issues or use of medication. She stated that her mother and aunt also had the same issue and lost teeth for no apparent reason. The clinical examination revealed the presence of all mandibular and maxillary teeth except the third molars and the maxillary right second premolar, canine, lateral incisor, and left first premolar (Fig. 1A). The maxillary right first premolar had extensive cervical caries extending 3 to 4 mm apical to the free gingival margin and class 3 mobility. The maxillary right central incisor, lateral, and canine had class 2 mobility. Panoramic, periapical, and bitewing radiographs were made and revealed external root resorption on the maxillary and mandibular anterior and premolar teeth (Fig. 1B). All molar teeth were intact. She had a moderate-to-high smile line, and her vertical dimension of occlusion was within normal limits. No abnormalities were observed extraorally except for angular cheilitis that had been previously diagnosed as a dermatologic condition.
Figure 1Preoperative situation A, Intraoral view. B, Panoramic radiograph.
Maxillary and mandibular diagnostic impressions were made with an irreversible hydrocolloid material (Jeltrate; Dentsply Sirona). A centric relation record was made with a polyvinyl siloxane (PVS) material (Blu-Mousse; Parkell) and a facebow record to mount the casts on a semiadjustable articulator (Denar Mark 310; Whip Mix Corp).
The extraction of her maxillary and mandibular anterior teeth and maxillary right premolar was deemed necessary because of the root resorption. Treatment options were discussed with the patient, including the extraction of all maxillary and mandibular premolars and anterior teeth and the fabrication of removable partial dentures (RPDs), implant-retained partial overdentures, and implant-supported fixed prostheses.
Accuracy of computer-assisted template-based implant placement using two different surgical templates designed with or without metallic sleeves: a randomized controlled trial.
The patient opted for the implant-supported fixed prostheses and was referred to an oral maxillofacial surgeon (OMFS) who recommended healing for 3 months after the extraction of nonrestorable teeth, a cone beam computerized tomography (CBCT) scan and possible grafting, or simultaneous grafting and implant placement. The patient elected to initially have her maxilla treated because of financial limitations. The advantages and disadvantages of treating only one arch versus both were discussed with the patient. She accepted the risks involved in treating only one arch and was scheduled for the extractions and the delivery of a maxillary immediate interim RPD.
After removal of the teeth to be extracted from the stone cast, the casts were scanned (S600 ARTI; Zirkonzahn Worldwide) for the tooth shape and positions to be used in further steps. The planned teeth were extracted, and the immediate RPD was delivered with a soft tissue conditioner (Lynal; Dentsply Sirona) (Fig. 2A). After 12 weeks, in the intraoral examination, limited interarch space was confirmed, as the anterior segment was close to the mandibular arch. The anterior alveolar segment was visible when the patient spoke and smiled (Fig. 2B). A CBCT scan was also made.
The patient’s initial scan was used for a virtual tooth arrangement, and missing teeth were replaced virtually. The standard tessellation language (STL) file of the diagnostic tooth arrangement was superimposed with the CBCT scan (Blue Sky Plan; BlueSkyBio) by using the remaining molar teeth as natural markers. Four implants were virtually placed and deemed adequate for supporting a screw-retained implant-supported fixed prosthesis (Fig. 3).
Figure 3A, Virtual tooth arrangement and surgical guide. B, Frontal view of planned implant axes. C, Occlusal view.
The OMFS requested a conventional surgical guide in order to have adequate visibility of the alveolar ridge during implant placement. A surgical guide was virtually designed from the diagnostic tooth arrangement, and occlusal extensions to the molars were added for retention (Fig. 4A). Two supporting connectors were designed as vertical stops to minimize movement toward the soft tissues during the osteotomy. The surgical guide was milled (M1; Zirkonzahn Worldwide) from a PMMA block (Temp Basic; Zirkonzahn Worldwide). Planned implant locations approximating the virtual implant locations from the occlusal and sagittal view screenshots were drilled in the guide.
Figure 4A, Milled surgical guide and diagnostic tooth arrangement. B, Intraoral view. C, Evaluation of smile line with diagnostic tooth arrangement.
On the day of implant placement, the surgical guide, which also served as a diagnostic tooth arrangement was evaluated intraorally before a flap was raised (Fig. 4B). The 3D position of teeth was evaluated in detail, paying attention to the smile line (Fig. 4C). After the locations of the platforms of the implants were determined by using the surgical guide, bone reduction was deemed necessary to create space for the prosthesis. The platforms of the implants (3.7×13 mm for right premolar, 3.7×10 mm for right lateral, 4.7×10 mm for left lateral, and 3.7×13 mm for left premolar, Tapered Screw Vent; Zimmer Biomet Dental) were planned to be placed 3 mm apical to the gingival zenith of the teeth in the surgical guide for a proper emergence profile in the planned prosthesis.
The locations of the implant platforms were evaluated after the flap was raised. The bone reduction level was marked, and the osteotomy was performed with the help of the surgical guide (Fig. 5). The implants were placed, the soft tissues were sutured, and the immediate RPD was relined with a tissue conditioner (Lynal; Dentsply Sirona) and delivered.
Figure 5A, Bone level for reduction marked. B, Implants placed after bone reduction. C, Panoramic radiograph after surgery.
Tissue healing was uneventful at the 1-week follow-up appointment. After 3 months of osseointegration, the implants were uncovered by raising a minimal flap, and the healing abutments were placed. The immediate RPD was relined with the tissue conditioner. Three weeks after uncovering, the distance between the implant platform to free gingival margins was measured to determine the multiunit abutment (MUA) gingival height. A PVS impression (Reprosil; Dentsply Sirona) was made at the same appointment to determine the relationship between the implant angulation and the planned prosthesis, and an impression of the mandible was also made followed by a centric relation record. After the impression was poured and scanned with a laboratory scanner (S600 ARTI; Zirkonzahn Worldwide), it was observed that, because the divergence among the implant angulations was small and the gingival depth of the implant platforms was 3 mm, 4 straight MUAs (3 mm) (TSV; ZimmerBiomet) would be appropriate for supporting the prosthesis (Fig. 6). Because the patient wanted to wait 1 year before proceeding with the mandibular treatment, a CAD-CAM PMMA interim fixed prosthesis on the implants was agreed on. The accuracy of the definitive cast was verified by evaluating the fit of a verification jig intraorally and making radiographs. Titanium (Ti) bases (Zirkonzahn Worldwide) for MUAs were used in the design, and the interim FPD was milled from a PMMA block (Temp Basic; Zirkonzahn Worldwide).
The gingiva was layered with pink composite resin (Anaxgum Gingiva; Anaxdent) (Fig. 7A). The Ti bases were bonded (Panavia 21; Kuraray America, Inc) in the fixed prosthesis, and the prosthesis was evaluated for passivity of fit, esthetics, occlusion, and speech. The passivity of fit was confirmed by using the 1-screw test (Fig. 7B). After occlusal adjustments, the MUAs were tightened to 30 Ncm (Fig. 7C). The prosthetic screws were tightened (15 Ncm), and the screw access channels were plugged with polytetrafluoroethylene (PTFE) tape and composite resin (Telio; Ivoclar Vivadent AG).
Figure 6Digital superimposition of virtual casts before and after bone reduction. A, Lateral view. B, Palatal view.
The patient was seen at 3-week, 6-month, and 1-year follow-up appointments, and she expressed no concern. No clinical issues were observed and she was able to perform hygiene procedures. At the 1-year follow-up, the patient was pregnant and wanted to postpone the treatment. She was seen at 20 months, and it was stressed that her prosthesis was for interim use only; she understood the complications that might occur (Fig. 8A). The patient reported a crack 23 months after delivery and wanted to proceed with only the maxillary definitive prosthesis because of financial limitations. The crack was around the implant at the maxillary left premolar site, where the Ti base was also loose (Fig. 8B). Scans (S600 ARTI; Zirkonzahn Worldwide) of the interim prosthesis and a cast obtained from an impression of soft tissues after the interim prosthesis was removed were superimposed with the initial scan. From the superimposed images, the soft tissue and occlusal changes were monitored and applied to the definitive prosthesis design. A zirconia prosthesis was milled (ICE; Zirkonzahn Worldwide), and pink gingival porcelain and glaze porcelain were applied (MiYO Pink; Jensen Dental). The Ti bases were bonded to the prosthesis (Multilink Hybrid Abutment; Ivoclar Vivadent AG). Occlusal adjustments were made, and the clinical protocol to deliver the interim prosthesis was followed when delivering the definitive prosthesis (Fig. 9).
Figure 8A, Follow-up intraoral view at 20 months. B, Fractured interim prosthesis at 23 months.
The reduced interarch distance, the patient’s demand for a fixed restoration, and the pronounced gingival display when smiling required careful treatment planning, including the previsualization of the prosthetic outcome to determine the extent of the osteoplasty and placement of the implants in the optimal 3D position, which formed the basis for the successful treatment.
From a biological perspective, it is important to place the implants 3 to 4 mm below the prospective gingival margin to allow an appropriate emergence profile.
Thick soft tissue facilitates a convex basal shape for the prospective prosthesis without compromising esthetics. A convex shape also facilitates cleanability.
On Behalf Of The Ticare Consensus M. Consensus statements and clinical recommendations on treatment indications, surgical procedures, prosthetic protocols and complications following All-On-4 standard treatment. 9th Mozo-Grau Ticare Conference in Quintanilla, Spain.
Therefore, a digital tooth arrangement simulating the desired outcome was milled, including stops on the molars, to ensure the reproducibility of its position. The design could have been changed digitally and milled for another clinical evaluation if necessary. It was also transformed into a surgical guide. A conventional surgical guide may be an efficient alternative to 2-part surgical guides (bone reduction guide and static computer-assisted implant surgery [s-CAIS] guide) in patients requiring pronounced osteoplasty. The influence of 2-part guides on the accuracy of implant position has not yet been reported.
Virtually guided alveolar ridge reduction combined with computer-aided implant placement for a bimaxillary implant-supported rehabilitation: A clinical report.
Altering the vertical implant position during s-CAIS can be challenging because it is necessary to deviate from the predetermined osteotomy protocol. Furthermore, an s-CAIS guide might interfere with the bone when the osteotomy is done before the alveolar ridge reduction. When the osteotomy is done after osteoplasty, the free-drilling distance may lead to decreased accuracy.
Using the milled evaluation prosthesis as a surgical guide facilitated control of the implant position relative to the planned outcome, which was also a benefit compared with s-CAIS.
Clinical intermediate-term or long-term observations on interim implant-supported PMMA prostheses are scarce.
Impact of prosthetic material on mid- and long-term outcome of dental implants supporting single crowns and fixed partial dentures: A systematic review and meta-analysis.
The influence of prosthetic material on implant and prosthetic survival of implant-supported fixed complete dentures: a systematic review and meta-analysis.
reported favorable performance of CAD-CAM PMMA specimens under loading compared with conventional PMMA. The patient presented was aware of the interim nature of her prostheses and the accompanying risk of the lack of long-term performance data but wanted to keep the interim prosthesis as long as possible. The interim prosthesis survived for 2 years despite potentially high occlusal forces from her opposing natural dentition, which may have been the primary reason for the crack formation. Postponing complex treatments for patients wearing CAD-CAM PMMA interim fixed prostheses might not necessarily be alarming, but the long-term performance of these interim fixed prostheses should be studied.
Summary
A maxillary screw-retained interim CAD-CAM PMMA fixed prosthesis supported by 4 implants was delivered to a patient with idiopathic root resorption. The PMMA fixed prosthesis exhibited satisfactory esthetic and functional outcomes over 23 months and was then replaced with a zirconia fixed prosthesis. Combining digital and conventional techniques facilitated a favorable treatment outcome and took the financial limitations patient into account.
References
Bansal P.
Nikhil V.
Kapur S.
Multiple idiopathic external apical root resorption: A rare case report.
Accuracy of computer-assisted template-based implant placement using two different surgical templates designed with or without metallic sleeves: a randomized controlled trial.
On Behalf Of The Ticare Consensus M. Consensus statements and clinical recommendations on treatment indications, surgical procedures, prosthetic protocols and complications following All-On-4 standard treatment. 9th Mozo-Grau Ticare Conference in Quintanilla, Spain.
Virtually guided alveolar ridge reduction combined with computer-aided implant placement for a bimaxillary implant-supported rehabilitation: A clinical report.
Impact of prosthetic material on mid- and long-term outcome of dental implants supporting single crowns and fixed partial dentures: A systematic review and meta-analysis.
The influence of prosthetic material on implant and prosthetic survival of implant-supported fixed complete dentures: a systematic review and meta-analysis.
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