Risk factors for technical and biological complications with zirconia single crowns.

OBJECTIVES: This practice-based study evaluated the clinical performance and risk factors for biological and technical complications with conventionally luted zirconia crowns. MATERIALS AND METHODS: Sixty-eight patients (39 female) with a total of 323 restorations placed on 219 vital teeth, 69 endodontically treated teeth (ETT), and 41 implants (incisors, 96; premolars, 89; molars, 138; observational period, 79.7 +/- 14.2 months) underwent a clinical follow-up examination and were included in the study. Time-dependent survival (in situ), success (event free), and veneering ceramic fracture (VCF) rates were calculated and analyzed relative to the following risk factors: smoking status, location of the crown, and type of abutment. RESULTS: Fifty-three complete failures were recorded. A significant influence of the abutment type on survival could be detected (p = 0.033): ETT demonstrated a significantly (p = 0.029) lower 7-year survival rate (73.8%, 95% confidence interval [95% CI] 0.600-0.876) than crowns placed on implants (90.0%, 95% CI 0.814-0.990). The success rate of the crowns was significantly influenced by the location of the restoration (p = 0.0058). A total of 75.6% (95% CI 0.648-0.864) of the anterior crowns remained event free, compared to 50.4% (95% CI 0.388-0.621) of the molar crowns. Furthermore, the location of the crowns affected the VCF rate (p = 0.018, event-free anterior teeth 95.2% (95% CI 0.880-1), event-free molars 80.9% (95% CI 0.706-0.913)). CONCLUSIONS: Survival and success rates were significantly influenced by the type of abutment and the location of the restoration. CLINICAL RELEVANCE: More complete failures should be expected for crowns placed on ETT, while crowns on molars demonstrated more biological and technical complications than anterior zirconia crowns.