Impact of reducing aligners' wear schedule from 7-days to 3-days on the predictability of tooth movement and treatment efficiency: a randomized controlled trial.

TRIAL

DESIGN

This was a two-arm, parallel-group, single-blinded, single-center prospective randomized controlled trial conducted between October 2023 and March 2025.

PARTICIPANTS

Thirty-eight adults aged 18-30 years with Class I malocclusion and moderate-to-severe mandibular anterior crowding were included, recruited from a university orthodontic clinic. Forty-five participants were initially randomized; seven were excluded due to non-compliance.

INTERVENTIONS: Participants were randomly assigned to a 3-day aligner wear protocol with reduced activation (0.11 mm/1° per tray) or a conventional 7-day protocol (0.25 mm/2° per tray).

OBJECTIVE

To evaluate the impact of reducing the aligner wear schedule from 7 days to 3 days on the predictability of linear and angular tooth movements for the mandibular incisors.

OUTCOME: The primary outcome was the deviation between predicted and achieved mandibular incisors' tooth movement following the first aligner series, assessed across three linear and three angular dimensions.

RANDOMIZATION: Participants were allocated using fixed block randomization with concealed sequentially numbered envelopes.

BLINDING: Outcome assessors were blinded to group allocation.

RESULTS

Linear deviations were comparable between groups and within the 0.5 mm ABO clinical threshold. Statistically significant angular deviations were observed for teeth 31 (p = 0.040) and 41 (p = 0.003), with additional significant buccolingual inclination for tooth 41 (p = 0.005); none exceeded the 2° clinical threshold. The 3-day group required significantly more refinement and clinical visits. No significant differences were observed in overall treatment duration or final occlusal outcomes. No adverse effects were reported.

CONCLUSIONS

While both protocols produced comparable occlusal outcomes, the 3-day protocol required more refinements and visits without improved predictability, suggesting wear duration plays a key role in aligner effectiveness.

TRIAL REGISTRATION: ClinicalTrials.gov xxxx.