Evaluation of the Survival Rate of Maxillary Minis in the Inter-Radicular Position
—Retrospective Study of 163 Clinical Cases

Introduction: The contribution of bone anchorage to orthodontic practice is now a matter of course, and effectiveness no longer needs to be demonstrated. Their comfortable success rate could be further improved by a better understanding of failures. The aim of this study was to evaluate the 1-year survival rate of minivis placed in the maxilla for distalizing mechanics. Materials and Methods: Our study involved 326 screws placed in 163 patients. The parameters studied were long-term stability factors, at least one year after mini-screw insertion. This was a retrospective study of patients attending an orthodontic practice in Toulouse. The aim of the study was to analyse the 1-year survival rate of miniscrews placed in the maxilla for orthodontic treatment with molar distalization mechanics. All patients were treated by the same practitioner, an exclusive orthodontist. Patients were informed about the study, and their consent to the use of their clinical records was obtained. The treatment plan included a maxillary recession mechanism assisted by a pair of bilateral minivis. Results: The results suggest that the angulation at the time of placement is a determining factor in the stability factors linked to the placement technique. We note that a more vertical placement of 6？ on attached gingiva increases the survival rate of minivis by around 10%, bringing the loss rate below 5%. With regard to host-related factors, indicators of vertical facial typology were found to be the factors with the greatest influence on the long-term stability of minis. Conclusion. There is certainly a need for further research into bone density, which could not be assessed in this study.