Clinical use of alumina-toughened zirconia abutments for implant-supported restoration: prospective cohort study of survival analysis

Objectives The aim of this prospective cohort study was to compute the long-term clinical survival and complication rates of alumina-toughened zirconia abutments used for implant-supported restorations and to evaluate the effects of several clinical variables on these rates. Material and methods From May 1998 to September 2010, 213 patients aged 18years or older were recruited. The patients received 611 external hex implants and 328 implant-supported fixed restorations using alumina-toughened zirconia abutments. During the follow-up, each restoration was coded as a dental event, which included loosening or fracture of abutment screws, and abutment fracture. From the coded data, the effects of the investigated clinical variablesrestored area (anterior/posterior), number of prosthodontic units (one/two units or over), prosthesis type (single-unit/multiunit without pontic/multiunit with pontic), implant system, and patient genderon the survival of the abutments were evaluated. Survival analysis using KaplanMeier method and Cox proportional hazard model was applied. The 5-year survival and complication rates of the abutments were assessed. Results The number of prosthodontic units and the type of prosthesis had a significant association with complication rates (P<0.05). KaplanMeier survival analysis estimated that the cumulative 5-year complication rate of the abutments used in single restorations was 19.7%. Multiunit-fixed dental prostheses without and with pontics had complication rates of 3.9% and 3.8%, respectively. The 5-year survival rate of the abutments was more than 95%, regardless of the type of prosthesis. Conclusions Alumina-toughened zirconia abutments are likely to exhibit excellent long-term survival in clinical use for fixed restorations. Single tooth replacement with the abutment at the molar region may require special care and extra attention.