Long-term changes in the occlusion post-retention on Japanese

Abstract

Objective This study was designed to elucidate the changes in the occlusal condition over a long period of time post-retention in Japanese patients who had undergone extraction treatment with the standard edgewise system (SES), a method of treatment in which the intercanine width and intermolar width are kept unchanged in pre- and post-treatment. Materials and methods 21 patients were selected from the records of Niigata University Medical and Dental Hospital. These patients had undergone extraction treatment with SES, and their retainers were removed 5 or more years before. The study models were assessed pre-treatment (T1), post-treatment (T2), post-retention (T3), and more than 5 years post-retention (T4) to investigate overjet, overbite, intercanine and intermolar widths, total arch depth and the Irregularity Index (I.I.). Results and discussion The number of subjects in this study was larger than that in other long-term progress reports on Japanese patients post-retention. The interval between T3 and T4 was on average 8 years and 2 months. Both the mandibular I.I. and the maxillary I.I. became minimum values, suggesting that all the cases had been stable for a long period time post-retention. There were no significant changes in the intercanine width between T1 and T2, which means that the treatment had been performed based on a concept of minimizing any potential changes in intercanine width. Conclusion The treatment procedure of minimizing potential changes in intercanine width and aligning the teeth in consideration of individual alveolar morphology would contribute to long-term stability of occlusion after retention.