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.