The correlation between crown-implant ratios and marginal bone resorption: a preliminary clinical study.

PURPOSE: The crown-implant ratio is defined as the physical relationship between each individual restoration's parts located both inside and outside the bone. This relationship represents the physical concept of a type I lever, which may be of biomechanical importance in implant treatment outcomes. MATERIALS AND METHODS: Specific patient data related to fixed implant prostheses were retrieved and studied in an effort to clinically and radiographically correlate crown-implant ratios. RESULTS: Recorded marginal bone resorption around implants (2.11 +/- 1.30 mm) at the end of a defined observation period did not correlate with the measured crown-implant ratio, which yielded values between 0.43 and 1.5 mm (P > .05). CONCLUSION: The mechanical determinants of implant success or failure are still not defined. It has been postulated that an increase in both crown-tooth, and comparably crown-implant, ratios would lead to a resultant increase in the magnitude of nonaxial forces transmitted to the tooth or implant. This could then lead to an increased vulnerability of either tooth or implant abutments to supporting bone loss. However, additional factors appear to impact long-term bone maintenance behavior around either type of abutment. Within the limited scope of this study, crown-implant ratios were not associated with recorded peri-implant bone loss. Int J Prosthodont 2010;23:33-37.