Material and methods: Forty-nine patients (30 women/19 men) were treated from 07/2008 until 07/2009 with either metal-ceramic crowns (group A: high noble alloy + low fusing porcelain) or zirconia crowns (group B: Cercon system, DeguDent). They participated in a clinical follow-up examination and were included in the study. All zirconia crowns were veneered with a modified porcelain firing cycle including a 6 minute cooling period. 90 restorations (72 vital abutments/18 non-vital abutments) were evaluated after a mean observational period of 338 days. 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 fabrication technique (metal-ceramic vs. zirconia) using the log-rank test (P<.05).
Results: No complete failures or loss of vitality were recorded in both groups, and 96.6% remained event-free. Two events were recorded in group A (1 loss of retention/1 minor ceramic chipping < 2 mm²). The third event occurred in group B (minor ceramic chipping < 2 mm²). All ceramic defects could be polished intraorally. Log-rank tests revealed non-significant differences in success rates (P=.876) of metal-ceramic and zirconia crowns fabricated with a modified porcelain firing.
Conclusion: In the present study, the short-term success rates of metal-ceramic and zirconia molar crowns showed no significant difference. The modified firing of the zirconia porcelain seems to decrease the risk for early ceramic chipping in the molar area leading to technical complication rate comparable to metal-ceramic crowns.