Published in the Journal of Oral Implantology, a new study has examined the health of implants that had been in place for over 5 years. Through examination of the crown-to-implant ratios in these cases, the authors discovered that this factor was not critical to the success of implants as previously believed.
During the study, researchers used radiographs to examine 309 single-tooth implant-supported restorations in 194 patients. All the implants had been placed using surgical procedures between February 1997 and December 2005.
The perceived ideal crown-to-root ratio for a tooth to serve as an abutment for a partial denture is considered 1:2; twice as much root as crown. However, prior studies have given mixed results about ratios for implanted teeth. Excessive crown-to-implant ratios have been identified as being harmful to long-term survival of an implant, while disproportionate ratios have been observed in high rates of implant survival.
The current study found the average crown-to-implant ratio to be 2 to 1. Natural teeth with such ratios are often recommended for extraction and replacement. The authors found that stable implants could be produced with less of the tooth serving as the root. In addition, the study found no statistically significant relationship between increasing crown-to-implant ratios and decreasing bone-to-implant contact levels around the implant.
The current study found an average crown-to-implant ratio of 2 to 1. Natural teeth with such ratios would often be recommended for extraction and replacement. The authors found that stable implants could be produced with less of the tooth serving as root. Additionally, the study found no statistically significant relationship between raising crown-to-implant ratios and lowering bone-to-implant contact levels around the implant.