Veneer fracture in implant-supported metal-ceramic restorations. Part I: Overall success rate and impact of occlusal guidance.

PURPOSE The aims of the presented study were to define the fracture rate of implant-supported metal-ceramic restorations delivered in private practice, and to identify if a restoration's contact during eccentric mandible movements has any influence on ceramic fracture rates. MATERIAL AND METHODS Within the period from 2005 to 2008, 251 patients, namely 105 men (42%) and 146 women (58%), received 775 dental implants which later were restored with metal-ceramic restorations. Data was gathered and analyzed in the form of a specially-designed electronic questionnaire. In total, 251 patients were rehabilitated with 350 prostheses consisting of 151 single crowns, 208 fixed partial dentures of various extents and 21 full-arch restorations. The method for retention of prostheses included cement-, screw-, or hybrid cement-screw retained prosthetic devices. The patients were recalled and examined for the presence of mechanical complications, namely ceramic fractures. Fractures were distinguished as adhesive or co-adhesive. The follow-up time was registered. RESULTS The mean ceramic fracture rate was 6.7%, as fracture occurred in 24 restorations. In the single crown group, the fracture rate was 1.3%, in the fixed partial denture division it was 6.7%, and the full-arch metal-ceramic restorations experienced 38.1% chipping. The mean follow-up period of prostheses was 9.5 months, ranging from 1 to 42 months. The analysis revealed that 66 prostheses had contact in protrusive and/or lateral mandibular movements, constituting 17.4% of all restorations; while 13 restorations had ceramic fractures, composing 19.7% of all guiding prostheses. CONCLUSIONS Within the limitations of this trial, it can be noted that ceramic veneer fracture rate was 6.7% in 380 restorations, and a conclusion that a restoration's contact during eccentric excursions may significantly enlarge fracture rates can be made.