Objective To study the changes of maxillary arch form in the application of pendulum appliance for maxillary first molar distalization. Methods Sixteen adolescent patients with Odontogenic Angle class II malocclusion and mild or moderate maxillary dental crowding were selected as the subjects.AII the patients were corrected with pendulum appliance for maxillary first molars distalization until the upper and lower first molar in the relationship was neutral and nearly neutral.Analysis of the results of before and after treatment were measured by dental models.then the data were analyzed by paired t-test. Results①The duration of distalization was (5.1 ±1.4) months. The crowding degree reduced (8.40±2.01)mm.The overjet increased by 0.43mm, and the overbite decreased by 0.32mm on everage.②The arch width of the maxillary canine, premolars, first molars were all increased to varying degrees.Previously the largest increase in arch width between maxillary premolars,first molars,followed by addition of at least the width between canine were observed in the changes. ③The alveolar arch width and arch width of the base bone in maxillary first premolar. second premolar and first molar increased were observed.Previously the largest increase in alveolar arch width and arch width of the base bone between maxillary molars, premolars, followed by addition of at least the width between canine were observed. ④No significant changes in anterior dental arch length, increased by only 0.10mm (P>0.05). The length of afterward dental arch increased 3.12mm (P<0.001).Maxillary alveolar arch length and the length of the base bone arch were increased by 3.23mm and 3.50mm separately (P<0.01). Conclusion ①Maxillary alveolar arch width and the width of the base bone arch increased during the period of application of pendulum appliance.This change is conducive to Angle class II malocclusion and the lifting of the arch anterior crowding, and thus provide a favorable basis for non-extraction treatment. ②The pendulum appliance can distalize the upper molars effectively for the odontogenic Angle Class II malocclusion. During the distalization of maxillary molars,to a certain extent, there is small anchorage loss in the premolars and incisors in a mesial direction.We should pay attention to anchorage control in the clinical diagnosis and treatment.u0000lasu0000 II ma%目的:研究摆式矫治器远中移动上颌第一磨牙对上颌牙弓形态的影响.方法:选择混合牙列或恒牙列早期的牙源性安氏Ⅱ类错(牙合)伴发上颌牙列轻中度拥挤的病例16例,应用摆式矫治器远中移动上颌第一磨牙至上下颌第一磨牙呈中性偏近中关系,测量矫治前后模型,对其结果进行配对t检验.结果:①远中移动时间平均(5.1±1.4)月,拥挤度平均减少(8.40±2.01)mm；前牙覆盖较矫治前平均增加0.43mm;前牙覆(牙合)平均减小0.32mm②上颌尖牙、前磨牙、第一磨牙间牙弓宽度有不同程度的增加,其中以前磨牙间增加最多,第一磨牙次之,尖牙间增加最少；③上颌第一、第二前磨牙、第一磨牙间牙槽弓、基骨弓宽度均有增加,第一磨牙间增加最多,前磨牙次之,上颌尖牙间增加最少；④牙弓长度方面:牙弓前段无明显改变,仅增加0.10mm(P＞0.05),而牙弓后段长度与矫活前相比增加了3.12mm(P＜0.001),上颌的牙槽弓长度与基骨弓长度分别增加了3.23mm(P＜0.01),3.50mm(P＜0.01).结论:①应用摆式矫治器远中移动上颌第一磨牙使上颌牙槽弓及基骨有一定的扩宽趋势,有利于牙弓前段拥挤的解除及安氏Ⅱ类错(牙合)的矫治,进而为非拔牙矫治提供有利依据；②远移上颌第一磨牙同时伴随少量的支抗丧失,临床应用中应予注意.
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