Abstract: PURPOSE: To investigate the clinical efficacy of miniscrew in controlling the roller coaster effect in long-distance space closure with clear aligner. METHODS: Sixteen adult patients with bimaxillary protrusion were selected. All cases were treated with clear aligner and their four first premolars were extracted. G6 was designed in all cases. In the experimental group, four miniscrews were inserted at the beginning of treatment to control the teeth in three dimensions; while in the control group, the miniscrews were not applied until obvious roller coaster effect appeared. Paired t test was used to analyze the data with Graphpad Prism 6.0 software package. RESULTS: All the extraction space was closed successfully and the lateral profile was improved significantly. The torque of the upper incisor was under well control and no roller coaster effect happened in the experimental group; while in the control group, the lingual inclination of the upper incisors and open bite of the posterior teeth developed(P<0.05). After the miniscrews intrusion of the upper anterior teeth, the occlusion relationship improved significantly. CONCLUSIONS: Miniscrews effectively prevents and eliminates the roller coaster effect in the process of long-distance space closure with clear aligner.

Key words: Clear aligner, Bi-maxillary protrusion, Space closure, Roller coaster effect, Miniscrew