An 18-year retrospective evaluation of glass-infiltrated alumina crowns.

OBJECTIVE: To evaluate the long-term performance of conventionally luted In-Ceram crowns with a maximum follow-up period of 18.6 years. METHOD AND MATERIALS: Eighty patients (39 females and 41 males) were treated at the University of Göttingen with a total of 272 In-Ceram restorations (163 anterior and 109 posterior). All participated in a clinical follow-up examination (mean observational period, 13.5 ± 3.6 years). Time-dependent crown survival (in situ criteria) and success rates (event-free restorations) were calculated according to Kaplan-Meier and analyzed in relation to the crown position (anterior vs posterior crowns) using a Cox regression model. RESULTS: Forty-three complete failures (overall survival, 80.5%) were recorded; 73.4% remained event-free after 15 years. Of the 163 anterior restorations, 18 crowns failed (9 fractures and 9 biologic reasons), resulting in a survival rate of 87.5% after 15 years (success rate, 82.7%). The remaining complete failures (10 fractures, 8 biologic reasons, and 7 changes of treatment plan) were recorded for posterior crowns (survival rate, 68.3%; success rate, 56.9%). Cox regression revealed a significant difference in survival (P = .00523) and success rates (P = .000297) of anterior and posterior crowns. CONCLUSION: The survival and success rates of anterior In-Ceram crowns at 15 years are comparable to those published for metal-ceramic crowns. Significantly lower survival rates and an increased rate of complications should be expected if In-Ceram crowns are placed on premolars and molars. Chipping of the veneering material was the most frequent technical complication in the posterior area.

Prospective evaluation of zirconia posterior fixed partial dentures: four-year clinical results.

PURPOSE: In this prospective clinical study, the performance of three- and four-unit fixed partial dentures (FPDs) with frameworks fabricated of yttria partially stabilized zirconia was determined after a mean observation period of 50 months. The study focused on the survival of the restoration (in situ criterion) and the success of the ceramic veneers (no defect). MATERIALS AND METHODS: Seventy-five patients with a maximum of two missing teeth and an antagonistic dentition were treated at the Department of Prosthodontics, University of Goettigen, with 99 posterior FPDs. Fifty-one specimens (experimental group) were veneered with an experimental ceramic suitable for titanium and zirconia frameworks (thermal expansion coefficient [TEC]: 8.5 microm/m*K); 48 restorations (Ceram-S group) were veneered with a commercially available low-fusing ceramic optimized for zirconia frameworks (TEC: 9.5 microm/m*K). All restorations were luted with zinc-phosphate cement. Statistical analysis was performed according to the Kaplan-Meier method; time-dependent success rates of the different types of ceramic veneers were analyzed using the log-rank test. RESULTS: Seven restorations were lost: 4 due to technical complications and 3 due to biologic complications. The overall survival rate after 48 months was 94% (Kaplan-Meier analysis). Twenty-three events required clinical intervention for restoration maintenance: 13 ceramic veneer chippings (polishing), 6 losses of retention (recementation), 3 caries lesions (filling therapy), and 1 loss of vitality (endodontic treatment). Between the two groups of veneering materials, no significant difference in the probability for success was determined (log-rank test, P=.81). CONCLUSIONS: Within a mean observation period of 4 years, sufficient survival rates for zirconia-based posterior FPDs could be verified. The main complications included fracture of the ceramic veneering material and decementation, which occurred mainly in the mandible.