Effects of 3- and 6-weekly orthodontic activation protocols on the alignment of mandibular anterior teeth: A single-center randomized clinical trial

Objective To compare the effectiveness of 3- and 6-weekly orthodontic activation protocols on the alignment of crowded lower anterior teeth. Methods This randomized clinical trial involved 63 participants (29 males and 34 females) aged 16–30 years who had Little’s Irregularity Index (LII) values of ≥ 5 to ≤ 11 mm and required treatment with a straight-wire appliance (SWA) with extraction of the lower first premolars. The patients were randomly allocated to 3- and 6-weekly activation groups and treated with a metallic SWA (0.022 × 0.028 slot size) and heat-activated nickel–titanium archwires of 0.014 to 0.020 inch diameter by a blinded orthodontist. The LII was measured using stone models, and the pain associated with orthodontic activation was assessed using a visual analog scale. Measurements were recorded at 0, 6, 12, 18, and 24 weeks after commencement of treatment. Root resorption in the lower anterior teeth was assessed using pre- and post-treatment small-field-ofview cone-beam computed tomography scans. Results The mean pretreatment LII was comparable between the 3- and 6-weekly activation groups (P = 0.865). However, at all subsequent visits, the 3-weekly activation group showed significantly lower LII values (P < 0.05). During the first six weeks, relief from crowding was greater in the 3-weekly activation group (P = 0.036). However, by the 12th week, the correction in LII was comparable between the two groups (P > 0.05). Mean pain score and root resorption showed no significant differences between the two groups. Conclusions The 3-weekly activation group showed greater and more rapid relief in mandibular anterior crowding than the 6-weekly activation group without causing more discomfort or root resorption.