Does aligner refinement have the same efficiency in deep bite correction?: A retrospective study

Background Refinements are very common in clear aligner treatments. The aim of this study is to assess whether the predictability of deep overbite correction is similar over several refinements using clear aligners (Invisalign, Align Technology, San Jose, Calif) and examine the accuracy of vertical movement and inclination change of individual teeth. Methods This retrospective study included 20 deep bite patients (7M and 13F; 32.63 +/- 11.88 years old; an initial overbite of 5.09 +/- 0.98 mm), consecutively treated from September 2016 and March 2023, who completed at least two sets of aligners, including refinements. The initial, predicted, and achieved models were exported from ClinCheck or OrthoCAD (Cadent Inc, Carlstadt, NJ) and superimposed via best-fit surface-based registration using SlicerCMF (version 4.9.0; cmf.slicer.org). We also examined 15 out of 20 patients who completed treatments. The overbite correction and changes in vertical movement and inclination for individual teeth were measured. Descriptive statistics and a paired t-test or Wilcoxon signed-rank test were performed. P < 0.05 was considered statistically significant. Results The mean accuracy of overbite correction was 37.63% after 1(st) set, followed by 11.19%, 6.32%, and 13.80% (2(nd)-4(th) sets), respectively. There were statistically significant differences between the predicted and achieved vertical movements and inclination changes for all teeth for the 1(st) and 2(nd) sets. For the completed cases, the mean overbite correction was 38.54% compared to the initially planned overbite correction, which is similar to one of the 1(st) set. Still, the vertical movements and inclination changes of all teeth present statistically significant differences between the initially planned and finally achieved movements except for maxillary lateral incisor torque. Conclusions The most overbite correction occurs during the 1(st) set of aligners, and refinement treatment does not significantly improve the deep bite correction.