Clinical study on physiological drift of the mandibular teeth after extraction of the first mandibular premolar

Objective:To study the physiological drift of the mandibular teeth after extraction of the first mandibular premolar.Method:20 patients with the needs of the first mandibular premolar's extraction were applying MBT appliance to the upper teeth first and no appliance on the mandibular teeth in 6 month.The diameters of the post extraction spaces and curvature of spee's curve measured at the time of 4 months after the first premolar's extraction were compared with that mea-sured at the time of 30 minutes after the first premolar's extraction.Result:There were significant differences in the diameters of the post extraction spaces and curvature of spee's curve measured at the time of 4 months and of 30 minutes after the first premolar's extraction.Conclusion:AngleⅠand AngleⅡcrowed malocclusion could be successfully treated with first premolar extraction,applying MBT appliance to the upper teeth first,by drift of the mandibular teeth.