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Purpose: To evaluate the mechanical stability of highly translucent zirconia (Zr) cantilevered fixed dental prostheses (cFDPs) and to investigate the influence of the number of implants (one versus two) supporting cFDPs with different restorative materials on their mechanical stability and load-bearing capacity. Materials and methods: Thirty-two specimens consisting of implant-supported prostheses embedded in resin blocks were fabricated. Sixteen specimens received one implant (bone-level implant, 4.1-mm diameter, 13-mm length; Straumann) to support two-unit cement-retained cFDPs with one extension unit and the other 16 received two implants (bone-level implant, 4.1-mm diameter, 13-mm length; Straumann) positioned corresponding to the missing maxillary central incisors to support three-unit cement-retained cFDPs with one extension unit. Two different prosthetic materials, chromium-cobalt (Cr-Co; Wirobond C+, Bego) and highly translucent Zr (Lava Plus, 3M ESPE) were selected to fabricate the two- and three-unit cFDPs. Standardized twoand three-unit Cr-Co frameworks (CC-I, n = 8; CC-II, n = 8) and highly translucent Zr frameworks (Zr-I, n = 8; Zr-II, n = 8) with a 6-mm cantilever extension were fabricated using CAD/CAM (EOS M 290). Following thermomechanical fatigue loading, the specimens were tested for fracture resistance under static loading. The influence of restoration material and number of supporting implants on fracture resistance were tested using two-way analysis of variance (ANOVA). The level of statistical significance was set below 5% (α < .05). Results: All specimens survived aging. The mean (± standard deviation) fracture resistance values were 416.25 (± 42.71) N for Zr-I, 548.75 (± 75.41) N for Zr-II, 601.0 (± 41.51) N for CC-I, and 664.5 (± 37.59) N for CC-II. CC and Zr group specimens showed significantly different fracture resistance results (P < .001). The number of implants significantly influenced the fracture resistance of Zr groups (P = .001), whereas the influence was not significant for CC groups (P = .089). Conclusion: Within the limitations of this in vitro study, highly translucent zirconia cFDP frameworks demonstrated the potential to withstand reported physiologic occlusal forces applied in the anterior region. The increase in the number of implants supporting zirconia cFDPs significantly contributed to achieving higher fracture resistance values. Keywords: dental implants, fixed dental prosthesis, cantilever, zirconia, highly translucent zirconia

Purpose: To digitally evaluate the volumetric wear of four different implant crown materials and their antagonists after artificial aging using an intraoral scanner (IOS) device and a laboratory desktop scanner. Materials and Methods: A total of 48 implants were restored with monolithic crowns and divided into groups according to restorative material: lithium disilicate (LDS); zirconia (ZR); polymer-infiltrated ceramic network (PICN); and porcelain fused to metal (PFM). Each specimen was scanned using a desktop scanner (LAB group; iScan D104, Imetric 3D) and an IOS device (IOS group; Trios 3, 3Shape) before and after chewing simulation (1,200,000 cycles, 49 N, steatite antagonist, 5°C to 50°C). The obtained STL files were superimposed, and the volumetric loss of substance of the crowns and their antagonists was quantified. Kruskal-Wallis, Spearman ρ, and paired t tests were used to analyze the data (α = .05). Results: The mean volume loss for each restorative material varied between 0.05 ± 0.06 mm3 (ZR/IOS) and 3.42 ± 1.65 mm3 (LDS/LAB). The wear of the antagonists was significantly lower (P < .05) for ZR than the other groups. Increased wear of the crowns was highly correlated with increased wear of their antagonists (rs = 0.859). When comparing the wear measurement using the two scanning devices, no difference in mean volume loss was found (IOS: 1.81 ± 1.81 mm3; LAB: 1.82 ± 1.78 mm3) (P = .596). Conclusion: Polished ZR was the most wear-resistant material and the least abrasive to the respective antagonist among the tested ceramics. For quantification of wear, this IOS device can be used as an alternative to desktop scanners.

Purpose: To evaluate biologic and esthetic outcomes, as well as the patient-reported outcome measures (PROMs), of full-mouth rehabilitations in patients suffering from generalized erosive and/or abrasive tooth wear following the 3-step technique. Materials and methods: Patients who received a minimally invasive full-mouth rehabilitation according to the 3-step technique and who were treated at the University of Geneva and/or in a private practice were considered for inclusion. The minimum service time of the restorations was 12 months. The biologic outcomes were analyzed by assessing pocket probing depth (PPD), Plaque Index (PI), and bleeding on probing (BOP). Furthermore, secondary caries, tooth vitality, and sensitivity to temperature were evaluated using the modified United States Public Health Service (USPHS) criteria. The esthetic outcomes were rated with the White Esthetic Score (WES). Finally, PROMs were evaluated using visual analog scales (VAS). Results: A total of 19 patients with 406 restorations (149 direct composite resins, 110 indirect composite resin/ceramic onlays, and 147 composite resin/ceramic veneers) were examined after a mean follow-up of 71.8 ± 28.6 months. Periodontal parameters were good (mPPD = 2.9 ± 0.4; mPI = 0.1 ± 0.2; and mBOP = 0.05 ± 0.1). No secondary caries were found, and no abutment tooth had lost vitality. A total of 36 abutment teeth had moderate sensitivity, but none presented pronounced sensitivity. The rehabilitations exhibited good esthetic outcomes (mWES = 8.4 ± 1.9). Patients reported satisfying esthetic results of their rehabilitations (mean VAS = 9.2 ± 1.6) and considered their treatment as comfortable (mean VAS = 8.2 ± 2.1), while the least favorably rated parameter was the cost of treatment (mean VAS = 4.1 ± 3.2). Conclusion: Minimally invasive full-mouth rehabilitations of patients with generalized tooth wear by means of the 3-step technique exhibit very good clinical medium-term results with respect to biologic and objective/subjective esthetic outcomes. The patient satisfaction with this treatment was high.

Purpose: To evaluate the survival rates and technical outcomes of minimally invasive full-mouth rehabilitations in patients affected by dental erosion and attrition. Materials and Methods: For this retrospective study, 28 subjects (8 women, 20 men; mean age: 45.6 years) who suffered from generalized erosions and attrition and who were treated according to the 3-step technique were invited to participate. The patient records were reviewed, and the restorations were clinically and radiographically examined. This part of the study (Part 1) evaluated restoration survival and technical outcomes using the modified United States Public Health Service criteria (mUSPHS). Survival analysis was performed using Kaplan-Meier survival statistics, and comparison between subgroups was made using log-rank test. For all other comparisons, cross tabulations of occurrence were performed, and significance was tested using Pearson chi-square test. The level of statistical significance was set at P < .05. Results: A total of 19 patients (3 women, 16 men; mean age: 45.6 years) agreed to participate. In these patients, 406 restorations (149 direct composites, 110 onlays, 147 veneers) supported by 365 teeth were examined. The mean time in service was 71.8 ± 28.6 months. Six failed restorations were identified; all were direct composites. The 6-year survival rates were 97.3% for direct composites, 98.2% for onlays, and 100% for veneers (P > .05). No differences were found among materials or locations of the restorations. Nineteen technical complications included 14 partial fractures, 3 fissures, 1 wear, and 1 decementation. The mUSPHS evaluation showed good technical outcomes. Presence or absence of a nightguard influenced restoration survival (P = .003). Conclusion: Minimally invasive rehabilitations of patients with erosions/attrition with the 3-step technique are a reliable treatment option in the medium term. Protective nightguards are recommended.

In recent years, numerous new dental materials have been introduced as alternatives to metal-ceramics for restorations on teeth and implants. This position paper presents the current evidence and respective clinical recommendations of the European Association for Osseointegration (EAO), one of the scientific partners of the International Journal of Prosthodontics, on material selection for single crowns (SCs) and multiple-unit implant-supported fixed dental prostheses (FDPs). Metal-ceramic restorations can be utilized in most clinical indications and are preferred to ceramic restorations in incidences such as long clinical implant crowns; cantilever implant restorations where one implant is supporting two crowns; implant-supported FDPs with extension units extending more than 7 to 8 mm (premolar size); implant-supported FDPs with more than two pontics; and implant-supported FDPs with small connector diameters due to limited intraocclusal space. Veneered or monolithic zirconia-ceramic and veneered or monolithic reinforced glass-ceramic implant-supported SCs are indicated for most SC cases in both the anterior and posterior areas. Today, implant-supported zirconia-ceramic FDPs that are conventionally veneered cannot be considered the material of first priority due to the pronounced risk for fracture of the framework and catastrophic fracture of the veneering material. Monolithic zirconia FDPs are a promising alternative to veneered implant-supported zirconia-ceramic FDPs. The mechanical stability of the translucent and shaded zirconia differs significantly between the grades of translucency. This must always be considered when clinical indications are recommended. As this specific area of prosthodontics is evolving fast, numerous studies evaluating different material options in implant prosthodontics are currently performed worldwide, and future consensus meetings will refine the present recommendations. The EAO will therefore regularly publish updated position papers on relevant topics.

Purpose: This in vitro study evaluated technical outcomes of monolithic zirconia implant-supported fixed dental prostheses (iFDPs) supported by different designs of titanium base abutments after aging and static load testing. Materials and methods: Sixty three-unit monolithic zirconia (yttrium oxide partially stabilized tetragonal zirconia polycrystals; Y-TZP)iFDPs were produced and divided into four groups: group A-conical titanium base abutments for the prosthesis; group B-cylindrical titanium base abutments for the crown; group C-conical titanium base abutment for the prosthesis and cylindrical titanium base abutment for the crown; group D-cylindrical titanium base abutments for the prosthesis. The samples were subjected to an aging protocol and to continuous static loading until failure and analyzed visually and with specific software. The technical outcomes comprised the occurrence of debonding, screw loosening, deformation and fracture, abutment deformation and fracture, implant deformation and fracture, zirconia chipping and fracture, and bending moments. The Pearson chi-squared test (χ2) and Fischer exact test were used to compare the outcomes. The Kolmogorov-Smirnov test was used to evaluate data distribution of the bending moments. Analysis of variance (ANOVA) was used for the analysis of parametric data distribution, and the Kruskal-Wallis test was used for nonparametric data distribution. Results: After aging, a higher percentage of debonding (P = .042) and micromovement (P = .034) was recorded in group C (P = .042). The conical titanium base abutments had a higher debonding (P = .049) and a higher macromovement rate (P = .05). The static load test showed higher bending moments in group D (P = .001) and lower bending moments in group A (P = .001). Debonding was highest in group C (P = .001) and lowest in group A (P = .002). Complete loss of retention rate was highest in group C (P = .001). The conical titanium base abutment had the highest debonding rate (P = .001) and complete loss of retention (P = .001). The micromovement rate was the highest for cylindrical titanium base abutments for the crown (P = .001). The lowest screw loosening, zirconia chipping, and fracture rate (P = .001) and the highest screw deformation (P = .004) were recorded in group A. The screw deformation rate was lowest in the cylindrical titanium base abutments for the crown (P = .008). Conclusion: The mixed titanium base abutment design comprising one conical and one cylindrical abutment in Y-TZP iFDPs led to the highest debonding rate. The cylindrical titanium base abutment for the prosthesis provided a lower percentage of debonding and the highest load resistance. Keywords: bending moments, debonding, implant-supported fixed dental prostheses, monolithic zirconia, technical complications, titanium base abutment

Purpose: To evaluate the mechanical stability and complication rates of titanium (Ti) and zirconia (Zr) abutments restored with cantilevered fixed dental prostheses (cFDPs) when supported by one or two implants.  Materials and Methods: A total of 32 specimens were fabricated. Half of the specimens received one implant, and the other half received two implants to simulate the clinical situation of two or three missing maxillary incisors, respectively. Each group was divided into two subgroups (n = 8). The Ti-1 and Ti-2 groups received Ti abutments (Anatomic Abutment, Straumann) supporting two- or three-unit metal cFDPs, respectively, while Zr-1 and Zr-2 groups received Zr abutments (IPS e.max Anatomic Abutment, Straumann). Following the cementation of cFDPs using resin cement (Multilink Automix, Ivoclar Vivadent), the specimens were subjected to thermomechanical fatigue load and then subsequently loaded until fracture in a universal testing machine. Following the static loading test, stereomicroscopic analyses (Carl Zeiss) were done to identify the weakest component of the cFDP, abutment, and implant assembly. Mann-Whitney U test was used to evaluate the effect of the number of supporting implants and abutment material on fracture strength values, and the level of statistical significance was set at 5% (α = .05). Results: All specimens survived aging, and no screw loosening or fracture was recorded. The mean fracture strength values were 226 N (± 26.45), 551.12 N (± 82.19), 601 N (± 41.51), and 664.5 N (± 37.59) for Zr-1, Zr-2, Ti-1, and Ti-2, respectively. The difference between fracture strength values of the Ti and Zr groups was significant in favor of Ti abutments (P < .001). The number of supporting implants showed a significantly positive effect on the fracture strength of Zr abutments. Conclusion: Zr abutments demonstrated lower fracture strength values than Ti abutments independent from the number of supporting implants when used under cFDPs. Two implant–supported cFDPs with zirconia abutments have the potential to withstand physiologic forces applied in the anterior region.