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Computer-aided design/ computer-aided manufacturing crown survival rates
1Department of Dentistry, Illinois Masonic Medical Center, Chicago, Illinois, USA.
Design:
A randomised controlled trial (RCT) was conducted in a dental school.
Intervention:
A total of 224 patients were randomised into two treatment groups, with 123 patients having teeth restored with KaVo Everest high-performance ceramic (HPC) crowns, fabricated by a computer-aided manufacturing procedure (KaVo Dental GmbH, Biberach an der Riss, Germany) and 101 patients receiving gold crowns. All crowns were conventionally cemented with glass-ionomer cement.
Outcome Measure:
Crowns were assessed for loss of vitality, surface roughness, fractures, marginal integrity, secondary caries at the crown margin, margin discolouration, marginal gap and crown loss at set time intervals of 6 and 12 months. The cumulative incidence of clinical complications was used as the criterion for failure. Time-to-event (failure) analysis was used for survival data. The incidence-free survival probabilities were then assessed using Kaplan-Meier analysis. A proportional hazard model (Cox) was used to test the treatment effect.
Results:
After an observation period of 6, 12 and 24 months, the prospective survival rates (Kaplan-Meier) for the KaVo Everest HPC crowns were 97.9%, 95.1% and 89.8%, and for the gold crowns were 100%, 94.8% and 92.7%, respectively. There were no significant differences between the two groups (P 0.2). The 1-year failure rates were 4.9% for the KaVo Everest HPC crowns and 5.2% for the gold crowns. The 1-year cumulative risks for loss of vitality, secondary caries, fractures, loss of crown and extraction of abutment of the analysed abutments (88) were 8.9%, 0%, 0%, 1.1% and 1.1%, respectively, for the gold crowns and 2.8%, 0%, 4.7%, 0% and 0.9%, respectively, for the ceramic crowns (107 analysed abutments). No perfect marginal fit was shown by 49.5% of the evaluated ceramic crowns and 26.1% of the gold crowns.
Conclusions:
The 12-month results indicate that Everest HPC crowns are suitable for posterior restorations, provided that an adequate tooth reduction is possible. The marginal fit shows potential for improvement.
