Occlusal changes during a 10-year posttreatment period and the effect of fixed retention on anterior tooth alignment

Introduction: The objectives of this research were to evaluate changes in occlusal components in 3 subperiods during a 10-year posttreatment time span and to examine the long-term effects of fixed retention on maxillary and mandibular anterior alignment. Methods: Ninety-six patients were examined; the Peer Assessment Rating Index and Little's Irregularity Index were measured at pretreatment, posttreatment, and 3 (T3), 5 (T5), and 10 (T10) years posttreatment. Unweighted Peer Assessment Rating component scores were analyzed for differences between all subperiods. The effect of fixed retention on posttreatment changes in Little's Irregularity Index was analyzed for both jaws with regression analysis. For the maxilla, 2 groups were compared: MX0, removable retainer until T3 (n = 52) and MX10, removable retainer until T3 combined with a fixed retainer until T10 (n = 23). For the mandible, 3 groups were compared: MD3, fixed retainer until T3 (n = 19); MD5, fixed retainer until T5 (n = 19); and MD10 fixed retainer until T10 (n = 48). Results: The Peer Assessment Rating Index percentage of improvement was 79% at T10. A gradual deterioration of occlusal components was seen, with small insignificant changes in each subperiod. Corrected for pretreatment irregularity, MX10 showed 0.6 mm lower LII than MX0. MD10 had significantly better alignment than MD3 (1.1 mm) and MD5 (0.7 mm). Conclusion: Gradual occlusal changes of limited clinical importance were seen during a 10-year posttreatment period. Long-term fixed retention in the maxilla was of minor importance in patients also wearing removable retainers. In the mandible, a 10-year fixed retention protocol gave moderately lower alignment scores compared to a 3-year protocol and slightly better alignment compared to a 5-year protocol.