Trial Finds Limited Power Arm Benefit in In-House Aligner Canine Retraction

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Posted: June 23, 2026

Trial Finds Limited Power Arm Benefit in In-House Aligner Canine Retraction

Edited by Dentaltown staff

As more practices produce clear aligners in-house, a new randomized trial found that a palatal power arm, a common anchorage aid, offered no clear advantage for controlling canine rotation or tipping during retraction in extraction cases. The study was published June 23 in Progress in Orthodontics.

The split-mouth trial followed 18 adults who needed both maxillary first premolars removed. Each received in-house clear aligner treatment, with a palatal power arm on one side and no power arm on the other, allowing a direct within-patient comparison.

Using three-dimensional model superimposition, the researchers measured six movements of the canine and neighboring teeth and tested whether results with and without the power arm were statistically equivalent.

Straight-line canine movement was equivalent between the two sides, within a margin of plus or minus 0.5 mm. Rotational and tipping movements were not: canine rotation differed by an average of 5.22 degrees and distal crown tipping by 1.67 degrees, both beyond the equivalence threshold.

The researchers also found signs of anchorage loss on both sides, including teeth tipping toward the extraction space, and concluded the power arm “may not significantly preserve anchorage.”

They cautioned that any apparent benefit for rotation and angulation control should be viewed with care, and that results from in-house aligners may not apply to commercially manufactured systems.

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


Trial Finds Limited Power Arm Benefit in In-House Aligner Canine Retraction

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