PASS Technique In The Treatment Of Angle Class Ⅰ Of The Maxillary Lip-opposite Low Canine Teeth

Objective:Use the PASS technique in the treatment of Angle class I of the maxillary lip-opposite low canine teeth. To evaluate the clincal of PASS technique on preservation of molar anchorage.Materials and methods:A female case with class I malocclusion was selected from Dalian Ortho Clinic in July2013, who was 11 years old, Han nationality. Facial symmetry. The intraoral examination exhibited Class I molar relationships. Crowding in the maxillary was severe about 10 mm, whereas crowding in the mandible was mild. Maxillary canine transposition. The patient was treated by extracting 14、24、34、44and applying PASS technique.Results:The course of orthodontic treatment is 14 months. Pre-treatment and post-treatment changes showed: normal overbite and overjet were achieved; molar relationship were maintained; good occlusal relationship; no space. Pitchfork Analysis shows upper first molars was distal tipping, 2.5mm mesial movement, lower molar was 2mm mesial movement, less than the extraction space 1/4, which could meet the request of maximum anchorage. So in the treatment, the upper and lower molars anchorage control good. Comparing the changes between lateral cephalometric film showed: the vertical was in good control. The post-treatment panoramic radiograph showed that roots were no significant absorption, alveolar bone and periodontal tissue were in good health.Conclusion:For class I of the maxillary lip-opposite canine malocclusion patients, the use of PASS technique, not only preserve molar anchorage but also can avoid the natural growth induced physiological anchorage loss, so a achieve the request of maximum anchorage.Application of PASS technique could be an effective and convenient way to preserve molar anchorage without using extra affiliated anchorage enhancement appliances.