Accuracy of final canine retraction with and without a palatal power arm using in-house clear aligners: a randomized clinical trial.

objectivesTo evaluate the accuracy of maxillary canine and anchorage tooth movement in first premolar extraction cases at final canine retraction, using In-house clear aligners (IHCA), by comparing the palatal power arm (PA) to control (C). METHODS AND

designA single-center randomized controlled trial with a split-mouth design was used.

settingUniversity. PARTICIPANTS AND

interventionsEighteen adults requiring extraction of maxillary first premolars were recruited and received multi-stage IHCA treatment.

main outcome measureOutcomes include 3 linear (mesio-distal, bucco-lingual, extrusion-intrusion) and 3 angular (tipping, rotation, torque) measurements. The primary outcome was canine distalization. Sequence generation: Patients were assigned to the PA and control sides using sequence-based randomization (Research-Randomizer website). Allocation concealment and blinding were not feasible. Pretreatment and canine final aligner virtual and actual digital models were superimposed using the 3D GOM-Inspect-Suite software to assess 6 types of tooth movement. Equivalence testing with Holm-Bonferroni correction was used to compare mean differences and 90% confidence intervals (CI) between PA and control sides for maxillary canines and anchorage teeth.

resultsFor canine linear movements, the mean differences ranged from -0.19 to 0.09 mm, with corresponding 90% confidence intervals entirely within the predefined equivalence margins of ± 0.5 mm, indicating practical equivalence. In contrast, canine rotation was not equivalent, with a mean difference of 5.22° and a 90% CI of (1.48, 8.95), which exceeded the predefined equivalence bounds of ± 1.5°. Similarly, canine distal crown tipping failed to demonstrate equivalence, with a mean difference of 1.67° and a 90% CI of (- 0.44, 3.78). For anchorage movements, most linear outcomes met the equivalence criteria, except for premolar mesialization and molar buccalization, whereas angular outcomes generally did not, as their confidence intervals were not fully contained within the equivalence region. These findings suggest loss of anchorage on both sides, characterized by mesial crown tipping and relative intrusion, indicating that the PA may not significantly preserve anchorage.

conclusionsLinear movements were equivalent between the PA and control, whereas canine angular movements did not demonstrate equivalence. Potential benefit of PA in angulation and rotation control should be interpreted with caution. These findings may have limited generalizability, especially to commercial aligners. Trial Registration Current Controlled Trials ISRCTN 14020146 of the International Standard Randomized Controlled Trial.