Risk factors for technical and biological complications with zirconia single crowns

This practice-based study evaluated the clinical performance and risk factors for biological and technical complications with conventionally luted zirconia crowns. 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. 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)). Survival and success rates were significantly influenced by the type of abutment and the location of the restoration. 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.