BACKGROUND:Heat Induction Typodont System (HITS) and Double-Slot Lingual Bracket System are patented products of the research group.It is very important to explore a good control of anterior tooth torque on the micro-implant-double-slot lingual bracket system.OBJECTIVE:To provide the experimental basis for force system applied for controlling the anterior tooth torque in lingual orthodontics through Typodont experiment based on the HITS.METHODS:Sixteen Class Ⅱ1 maxillary Typodont models without first premolar were made.Micro-implants were implanted in the lingual region of posterior teeth and labial region of anterior teeth.The direction of the retracting force was adjusted by changing the position of the lingual micro-implant (with a distance of 4,8 mm from the alveolar crest) and the length of the hook (4,8 mm).And lingual retracting force (150,300 g) and labial intruding force (50,100 g) were loaded.The tooth movement by HITS was simulated and the models were scanned before and after force loading.Then the three-dimensional images were reconstructed by Mimics 17.0.Factorial variance analysis was adopted to compare the anterior movement changes under different loading modes.RESULTS AND CONCLUSION:When the length of the hook was 4 mm/8 mm and the lingual micro-implant was 6 mm/10 mm from the alveolar crest,the displacement difference between the incisal edge and the root of the anterior teeth was smaller than other groups.The optimal mechanics was 150 g for the lingual retracting force and 100 g for the labial intruding force.It could provide a satisfactory control to the anterior teeth torque when retracting force and labial intruding force were loaded at the same time during the space closing phase of lingual treatment.This study based on HITS provided a scientific basis for the clinical application of micro-implant-double-slot lingual bracket system in space closing phase.