髁突形态与覆深度关系的研究

目的　探讨髁突形态与不同覆深度的关系。方法　选择正常者、开畸形患者、覆正常的错畸形患者和深覆畸形患者各 5 0人 ,均为 18至 2 6岁成人。应用曲面断层片研究左右两侧的髁突形态 ,分别测量并计算上部髁突高度 /升支高度比 (UCH/RH)和髁突高度 /宽度比 (TCH/CW )。将髁突形态分为四种类型 :直立型 (类A) ,前倾型 (类B) ,后倾型 (类C)和尖型 (类D)。结果　开组的上部髁突高度相对升支高度明显小于其他各组 (P <0 0 0 1)。正常组的髁突形态比较粗壮 ,高度宽度比明显小于其他各组 (P <0 0 0 1)。类A和类B属于正常髁突形态 ,占正常组的 99%。类C和类D属于异常髁突形态 ,且在开组中的比例明显高于正常覆组或深覆组。另外 ,只有开组中显示上部髁突高度两侧不对称 (P <0 0 5 )。结论　开组髁突形态与其他各组相比明显不同。

Condylar morphology in normal occlusion,openbite,and deep overbite malocclusions

Objective To investigate the relationship between the condylar morphology and malocclusions with different overbite depths. Methods The samples were divided into four groups: G1, normal occlusion; G2, openbite malocclusion; G3, malocclusion with normal amount of overbite, and G4, deep overbite malocclusion. To ascertain the morphology of the different condyles, 400 mandibular condyles of 200 adult cases, ranging from 18 to 26 years of age, were assessed using panoramic radiographs. The upper condylar height to the ramus height ratio (UCH/RH)and the condylar height to the width ratio (TCH/CW) were measured and calculated. The condylar morphology was classified into four types: straight (Type A), anteriorly inclined (Type B), posteriorly inclined (Type C), and spiky or finger-shaped type (Type D). The symmetry of the condyle and ramus in vertical dimension between the right and left side was calculated with the asymmetric index formula. Results The openbite group has a significantly shorter upper condyle relative to the ramus than any other group( P <0.001). The normal group showed a much stronger condylar shape( P <0 001)compared to other maloccusion groups. Type A and B are normal condylar shapes that comprised 99% of the normal group while Type C and D are abnormally contoured. The prevalence of these two abnormal types was significantly higher in the openbite group than in either the normal ovebite malocclusion or the deep overbite malocclsuion group. Fur thermore, only the openbite group showed upper condylar height asymmetry ( P <0 05). Conclusions The morphology of the condyle in openbite is different from that of other groups, and that difference may be the predisposing factor to temporomandibular joint disorders.