Retrospective analysis of porcelain failures of metal ceramic crowns and fixed partial dentures supported by 729 implants in 152 patients: patient-specific and implant-specific predictors of ceramic failure.

STATEMENT OF PROBLEM Porcelain fracture associated with an implant-supported, metal ceramic crown or fixed partial denture occurs at a higher rate than in tooth-supported restorations, according to the literature. Implant-specific and patient-specific causes of ceramic failure have not been fully evaluated. PURPOSE The purpose of this retrospective study was to evaluate the potential statistical predictors for porcelain fracture of implant-supported, metal ceramic restorations. MATERIAL AND METHODS Over a 6-month period, a consecutive series of patients having previously received implant-supported, metal ceramic fixed restorations were examined during periodic recall appointments. The number of supporting implants, number of dental units, type of restoration, date of prosthesis insertion, location in the dental arch, opposing dentition, type of occlusion, presence of parafunctional habits, use of an occlusal protective device, presence or absence of ceramic fractures, gender, and age were recorded for each patient. The generalized estimating equation (GEE) approach was used for the intrasubject correlated measurements analysis of categorical outcomes (presence or absence of ceramic fractures) to determine which patient- and implant-specific factors would predict porcelain fracture (alpha=.05). RESULTS Data were collected from 152 patients representing 998 dental units (390 single crowns and 94 fixed partial dentures) supported by 729 implants. Porcelain fractures of 94 dental units occurred in 35 patients. The fractures were significantly (P<.05) associated with opposing implant-supported metal ceramic restorations, bruxism, and not wearing a protective occlusal device. Metal ceramic prostheses (single crown or fixed partial dentures) had approximately 7 times higher odds of porcelain fracture (odds ratio (OR)=7.06; 95% confidence interval (CI): 2.57 to 19.37) and 13 times greater odds of a fracture requiring either repair or replacement (OR=13.95; 95% CI: 2.25 to 86.41) when in occlusion with another implant-supported restoration, as compared to opposing a natural tooth. In addition, patients exhibiting bruxism or not wearing an occlusal device had approximately 7 times higher odds (OR=7.23; 95% CI: 3.86 to 13.54), and 2 times higher odds (OR=1.92; 95% CI: 1.01 to 3.67) of porcelain fracture when compared to patients without bruxism and patients not wearing an occlusal device. CONCLUSIONS Implant-supported metal ceramic single crowns and fixed partial dentures were found to have a significantly higher risk of porcelain fracture in patients with bruxism habits, when a protective occlusal device was not used, and when the restoration opposed another implant-supported metal ceramic restoration.