Implant-supported single crowns predictably survive to five years with limited complications

An electronic MEDLINE search was conducted to identify cohort studies, prospective or retrospective, describing clinical performance of implant-supported single crowns. Manual searches of bibliographies from full-text articles and related reviews were conducted using numerous scientific journals. Studies were included if the mean follow-up time was at least 5 years, if articles were published in the English or German language, if patients were physically examined, and if study details were sufficient for data extraction. Of the initial 3601 studies identified, only 26 were selected. No randomized control trials were identified.

The 5-year survival and complications of implant-supported single crowns.

The primary outcome measure in this study was survival of endosseous implants when used to support single crowns. In addition, the clinical performance of soft tissue (peri-implantitis) and hard tissue (bone level) was documented. Clinical complications of a biomechanical nature were recorded relative to fracture of restorative materials. Poisson's regression models were used to estimate failure and complication rates at 5 years.

A systematic review of the scientific literature identified 26 studies from which data were extracted (1558 placed implants). Meta-analysis identified survival of implants used to support and retain single crowns at 96.8% (95% confidence interval [CI]: 95.9%-97.6% after 5 years). The survival rate of the single crown restorations documented in 13 studies was 94.5% (95% CI: 92.5%-95.9%) with a significantly higher survival rate when metal ceramic crowns were used in comparison with all ceramic crowns (95.4% CI: 93.6%-96.7%; 91.2% CI: 86.8%-94.2%). Soft tissue complications, including peri-implantitis, were observed in 9.7% of the single crowns, whereas bone loss exceeding 2 mm was identified on 6.3% of the implants over the 5-year study. Prosthetic or abutment screw loosening was observed in 12.7%of the restoration and screw fracture occurred in 0.35%. Although only 7 of the 26 studies reported esthetic complications, the cumulative effects of esthetic complications approached 9% at 5 years.

From the presented data it may be concluded that 5-year survival of implant-supported single crowns is high, although biologic and mechanical complications are anticipated.