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

Abstract

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.