Method: Data was collected on crowns and fixed partial dentures (FPDs) in which zirconia copings\frameworks were milled (Lava™, 3M ESPE) and layered with veneering porcelain all in one dental laboratory. Cantilever FPDs, splinted crowns, implant-supported restorations, and restorations delivered less than 4 years prior to survey were excluded. Data included tooth numbers, time from delivery, brand of veneering porcelain, and requests for remakes. Probability distributions of remakes were reported. Chi-square test was used for inter-group comparisons (P<0.05).
Result: 24392 zirconia-based crowns (21220 (87%) posterior and 3172 (13%) anterior) were delivered. 605 were layered with LavaTM Ceram and 23787 were layered with Noritake CZR. Requests for remake were made for 185 (0.75%) of 24392 zirconia-based crowns. 72 out of 185 crowns were sent for remake prior to cementation (posterior 67 (0.2%) and anterior 5 (0.02%)). Other remakes of crowns were requested after cementation within a timeframe ranging from 1 to 33 months of service (posterior 97 (0.3%) and anterior 16 (0.06%)). Total number of remakes was 164 (0.67%) for posterior and 21 (0.08%) for anterior crowns (p=0.57). Remakes were 44 (0.18%) for premolars and 120 (0.49%) for molars (p=0.05). Comparisons were statistically not significant. 1482 zirconia-based FPDs with 580 posterior, 578 anterior, and 324 mixed with both posterior and anterior abutments (n=324) were also surveyed. There were only 4 (0.2%) remakes. 2 posterior restorations were resent for remake before cementation. 2 remakes of anterior restorations were requested within a time frame of 3 and 26 months after cementation.
Conclusion: Within limitations of this retrospective survey it may be concluded that frequency of remakes of zirconia-based restorations after 4-8 years of service made by one dental laboratory was low for crowns and FPDs.
Keywords: Zirconia, Survey