Cast analysis of 37 patients treated with MBT~(TM) appliance / 北京大学学报(医学版)

ABSTRACT

Objective: To study the 3D positional changes occurring to anchor molars of 37 patients treated with MBT appliance. Methods: Thirty seven patients who needed maximum upper molar anchorage were divided into two treatment groups at random, group Ⅰ was comprised of 19 patients whose anterior teeth were retracted en masse, and group Ⅱ included 18 patients whose anterior teeth were retracted by two step. All the patients were treated with MBT appliance and headgear. Dental casts recorded before and after treatment were analyzed by YM 2115 three dimensional digitizer and related software. The changes of anchor molar tip,torque and rotation were compared between the two groups. Results: During the treatment, average anterior movement of the upper first molars was 4.53 mm, average extrusion of the upper first molars was 1.53 mm; the crown of the upper first molar tipped forward (6?4)?,torque buccally (3?6)?,and mesiolingually rotated 3.15?; In en mass group, the crown of the upper first molar tipped more mesially than the two step group, and the difference was statistically significant. Conclusion:Almost all the upper first molars showed the tendency to rotate and tip mesially and torque bucally; there was no statistically significant difference between the two treatment groups when upper molar positional changes were concerned except for the mesial tip of the crown.