高角及低角型深覆(牙合)矫治机制及稳定性研究

目的:比较高角及低角型深覆(牙合)病例正畸矫治及治疗后复发的结构特征,以探讨两者在矫治机制及复发特点的差异.方法:从北京大学口腔医学院正畸门诊挑选出治疗后2年以上的高角组深覆(牙合)病例10例,低角组深覆殆病例9例.将两组病例进行测量并统计分析.结果:治疗后高角组中齿槽座点-鼻根点-下齿槽座点(ANB)角、颌凸(NA-PA)角减小,后下面高/前下面高之比(Ar-Go/ANS-Me)增大,上下磨牙均升高;低角组仅表现为下颌磨牙升高.复查阶段高角组与低角组在覆殆稳定性方面的差异无统计学意义.高角组复查阶段覆(牙合)的变化主要与治疗中上切牙舌倾有关;低角组与治疗中磨牙的升高相关.结论:治疗后高角组下颌升支表现出较强的生长潜力,从而维持下颌平面的倾斜度.覆殆的复发主要与牙齿因素的变化相关.

Preliminary study of treatment mechanism and stability in deep overbite malocclusion with hyperdivergent and hypodivergent skeletal pattern

OBJECTIVE: Comparison of structural characteristic changes between deep overbite malocclusions with hyper- and hypodivergent skeletal pattern during treatment and follow-up stages. To discuss the difference between both in treatment mechanism and characteristic of relapse. METHODS: 59 cases out of 162 finished patients with deep overbite malocclusion followed for more than 2 years, selected from orthodontic clinic in school of stomatology Peking University, were filtered by cephalometrics (MP-SN>40 degrees or <29 degrees)and then two groups were formed. The hyperdivergent group (MP-SN>40 degrees) comprised 10 cases and the hypodivergent group (MP-SN<29 degrees) comprised 9 cases. Measurements and statistics were performed upon the two groups. RESULTS: After orthodontic treatment, the hyperdivergent group exhibited the extrusions of upper and lower molars [U6-PP increased from (10.69+/- 2.10)mm to (12.91+/-2.19)mm; L6-MP increased from (17.34+/-2.73)mm to (20.86+/-3.08)mm]. As to the skeletal change, a decrease of ANB angle from (5.86+/- 1.34) degrees to (4.62+/-1.67) degrees and NA-PA angle from (11.99+/-3.74) degrees to (8.76+/-4.45) degrees reflecting the sagittal change tendency from skeletal Class II to Class I. In vertical direction, the ratio of Ar-Go/ANS-Me increased from (0.58+/-0.03) to (0.62+/-0.05). Compared with the hyperdivergent group, the hypodivergent one only showed the extrusion of lower molars after treatment. The stability of overbite didn't show any statistically significant difference between two groups during the follow-up stage. Also in this stage the change of overbite in the hyperdivergent group was mainly due to the lingual inclination of upper incisors during the treatment stage and in the hypodivergent group it was due to the molar extrusion during treatment. CONCLUSION: The ramus showed great potential of growth in the hyperdivergent group during the treatment stage, which maintained the inclination of mandibular plane. The relapse of overbite was correlated with the changes of teeth during the treatment and follow-up stages.