The Comparisons Of Crown-to-Implant Ratios Of Implant-Supported Restorations And Crown-to-Root Ratios Of Natural Teeth And The Initial Analyses Of Influence Of Crown-to-Implant Ratios Of Implant-Supported Restorations On Crestal Bone Loss

Objective: First, determine the crown-to-implant ratios of implant-supported restorations, then to compare the crown-to-implant ratios to the guidelines established for the crown-to-root ratios of natural teeth. Second, evaluate the influence of the crown-to-implant ratio on crestal bone loss around dental implants.Methods: 1.A total of 103 ITI dental implants were placed in the jaws of 88 partially edentulous patients. When the restorations were accomplished, the radiographs of implant-supported restorations and existing isonym natural teeth in the opposite side were taken with a standardized paralleling technique. The length of the crown,root and implant were measured by CliniView 6.1.3 software.2.One year after the implants restoration, according to the following inclusion criteria: no periodontopathy, no system diseases, don't take immunodepressant, not in pregnancy, single tooth implant-supported restoration and reaching to return visit, 47 ITI implants of 39 patients were selected. The radiographs of implant-supported restorations were taken with the standardized paralleling technique. Then measure and calculate the crestal bone loss around dental implants after one year restoration by the CliniView 6.1.3 software.Results: 1. The average crown-to-implant ratio of implant-supported restorations exceeds the average crown-to-root ratio of natural teeth (P<0.001).2. There was no statistical difference between the group of crown-to-implant ratios<1 and crown-to-implant ratios≥1 in crestal bone loss around dental implants after one year restoration (P>0.05).3. There was no correlation between crown-to-implant ratios and crestal bone loss around dental implants (P>0.05).Conclusions: 1. The crown-to-root ratio guidelines associated with natural teeth should not be applied to potential implant site or existing implant restoration.2. In the follow-up time (range from 3 to 45 months and the average follow-up time was 22 months), there was no failure of the 103 ITI dental implants in this study. The average clinical crown-to-implant ratio of implant-supported restorations is 1.26±0.22 which is so bad for natural teeth. These facts demonstrate that crown-to-implant ratio may not be a good predictor of implant survival and can make an expansion of dental implant case selection criteria.3. Crestal bone loss around dental implants is considered to be one of the major problems in the long-term success of an implant restoration. In the digital and biomechanical modality, larger crown-to-implant ratio means greater bone stress and then more bone loss. But in this study, there was no statistical difference between the group of crown-to-implant ratios<1 and crown-to-implant ratios≥1 in crestal bone loss around dental implants after one year restoration and no correlation between crown-to-implant ratios and crestal bone loss around dental implants. Large crown-to-implant ratio is not equal to more crestal bone loss, such implant restoration also can get good predictability and long-term outcome. ,...