Accuracy of Preliminary Maxillary Canine and Anchorage Tooth Movement in Premolar Extraction Cases Using 12 In-House Clear Aligners: A Randomised Control Trial Comparing Power Arm and Control

Abstract

Objectives: To investigate maxillary canine movement accuracy and anchorage during space closure in first premolar extraction cases (maximum anchorage) using In-House Clear Aligners (IHCAs). Materials and Methods: A randomised controlled trial with a split-mouth design recruited 16 adults in university setting. Each patient was randomly assigned by side for canine retraction using 12 IHCAs to both the experimental palatal power arm (Pa) and non-Pa control (C). Accuracy was assessed using GOM Inspect by superimposing the virtual and actual digital models between pretreatment and 12th IHCA. Paired t-test or Wilcoxon signed-rank test was used to compare virtual-power arm (VPa) versus actual-power arm (APa) and virtual-control (VC) versus actual-control (AC). Root mean square error (RMSE) was calculated. Results: Pa displayed a significant difference in preliminary canine distalisation (VPa 2.0 mm vs. APa 2.4 mm), while the control did not differ. Both Pa and control exhibited significantly greater actual distal crown tipping than virtual movement (VPa 4.4° vs. APa −6.3°/VC 4.4° vs. AC −4.3°). AC achieved more canine rotation than VC. RMSE was slightly greater in Pa than control for canine distalisation (Pa 0.6 vs. C 0.55 mm) and distal crown tipping (Pa 10.9° vs. C 8.99°). Conversely, Pa displayed better accuracy in canine rotation. For anchorage, Pa and control exhibited significantly greater actual mesialisation and mesial tipping than virtual. RMSE for anchorage mesialisation and mesial tipping were comparable between Pa and control. Conclusions: Preliminary canine retraction using Pa may result in greater error in distal crown tipping but less rotation than control. Trial Registration: ISRCTN 14020146 by the International Standard Randomised Controlled Trial Registry.