A clinical study of retraction system of maxillar anterior teeth with computer-aid designed for individual lingual orthodontics

Abstract

Objective To evaluate the effects of anterior torque controlling with individual lingual en masse retraction in the maxillary anterior teeth using computer-aided designed lever-arm and miniscrew system.Methods 20 non-growing cases with treatment protocol of extraction was selected and treated with individual lingual system,employing the lever-arm and miniscrew as en masse retraction system.Based on CBCT data,Mimics 10.0 and Claytool software was used to determine the length of the lever-arm and the position of the miniscrew so as to make sure the line of action of retraction force pass through the center of resistance of 6 maxillary anterior teeth and parallel to occlusion plane.The cephalograms were analyzed for differences in skeletal,dental and soft tissue variables between pretreatment and postretraction.Results Distances from tip of upper central incisor to PTV (PTV-U1) and upper lip to E line (LS-E) was significantly decreased (P＜0.001),and no significant difference was noted for the distance from tip of upper central incisor to Palatal Plane (P＞0.05).Significant retraction of maxillary anterior teeth was achieved in all patients and improved profile was obtained.Bodily movement and slightly controlled tipping occurred during the retraction and maxillary molars did not show any statistically significant movement. Conclusions The computer-aided design and location of the lingual retraction system (lever-arm and miniscrew) produced excellent and efficient retraction with great accuracy in control of anterior torque. Key words: Lever-arm; Miniscrew; Computer-aided design; Lingual orthodontics; Anterior torque