RCT Questions Palatal Power Arm Benefit in In-House Aligner Canine Retraction

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Posted: June 23, 2026

RCT Questions Palatal Power Arm Benefit in In-House Aligner Canine Retraction

Edited by Orthotown staff

Adding a palatal power arm to in-house clear aligners did not improve control of canine rotation or tipping during retraction in extraction cases, according to a randomized clinical trial published June 23 in Progress in Orthodontics.

The single-center, split-mouth trial enrolled 18 adults who required extraction of both maxillary first premolars. Each patient received in-house clear aligner treatment, with a palatal power arm placed on one side and the opposite side serving as the control.

Researchers used three-dimensional model superimposition to measure six types of tooth movement: three linear and three angular. They then tested for statistical equivalence between the two sides.

Canine linear movements were equivalent, with mean differences falling within the predefined margin of plus or minus 0.5 mm. Angular movements were not. Canine rotation showed a mean difference of 5.22 degrees, and distal crown tipping a mean difference of 1.67 degrees, both outside the equivalence bounds.

Anchorage outcomes also fell short of equivalence for most angular measures. The authors reported signs of anchorage loss on both sides, including mesial crown tipping and relative intrusion, and concluded the power arm “may not significantly preserve anchorage.”

The authors cautioned that any benefit of the power arm for controlling angulation and rotation should be interpreted carefully, and that the findings may not generalize to commercially produced aligners.

The study was led by Nita Viwattanatipa and colleagues in the Department of Orthodontics at Mahidol University in Bangkok, Thailand. It was registered with the International Standard Randomized Controlled Trial registry.

Sources:
Progress in Orthodontics, “Accuracy of final canine retraction with and without a palatal power arm using in-house clear aligners: a randomized clinical trial,” June 23, 2026, DOI 10.1186/s40510-026-00630-5: progressinorthodontics.springeropen.com


RCT Questions Palatal Power Arm Benefit in In-House Aligner Canine Retraction

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