Efficacy of in-house clear aligner therapy mechanics on root torque: an in-vitro study

Abstract

This study aimed to evaluate the torque effectiveness of different attachment types and power ridges used in clear aligner therapy (CAT) on the upper lateral incisors. A typodont model simulating oral conditions was developed. Two hundred lateral incisor samples were divided into five groups based on attachment types and clear aligner modifications: no attachments (NA), horizontal ellipsoid attachment (HEA), vertical ellipsoid attachment (VEA), buccal power ridge (BPR), and buccal and palatal power ridge (BPPR). Subsequently, a 5° palatal torque moment was applied to the lateral incisors. In-house clear aligners were inserted, and 3D scanning was performed after each aligner step. Post-treatment 3D models were compared with pre-treatment models. The lateral incisors were assessed for torque, tipping, and rotational movements. The HEA group (41.6%) and the BPPR group (40.8%) showed significantly higher torque effectiveness than the NA group (20%) when 5° of torque was delivered. The planned movement was approximated when 1° and 2° of torque were applied in the NA group (114% and 98%, respectively). The NA and BPR groups showed the highest loss of anchorage. When more than 3° of torque was applied, HEA and BPPR were more effective than NA in achieving the CAT’s planned torque of the upper lateral incisors, although with an efficacy rate of approximately 40%. It is challenging to achieve torque movement using CAT. When less than 3° of torque was required, additional mechanics were not necessary. BPPR and HEA showed higher effectiveness when 5° of torque was applied. The efficacy of BPR was similar to that of NA.