二級第一分類異常咬合之
齒顎顏面形態測量學的探討

研究背景：　　二級異常咬合佔了人口的百分之二十左右，其在顏面外觀的特殊表徵包括了：上顎骨前突、下顎骨後縮或是合併以上兩種特徵。而這類患者的齒列咬合關係又以安格式二級第一分類居多。在治療上，如何提供患者一個良好的功能及美麗的外觀，都是一種極大的挑戰。　　在以往的研究中，多數的研究對象多為青少年或兒童，常伴隨生長發育而帶來的顱顏形態改變。成人與仍有生長潛能之青少年或兒童相較，其顱顏形態、矯正治療考量應有所差異。因此研究已生長完成的顱顏形態對於臨床上治療有特別的意義及價值。研究目的：本研究目的在探討國內成年人二級第一分類異常咬合之齒列顏面形態的特徵。材料與方法：比較80 名二級第一分類異常咬合成年人與80名正常咬合成年人的測顱放射線圖。共採33 個標記點，描繪後利用數位板輸入電腦。測顱形態分析共包括23 項線段、26 項角度、4 項比值。在進行測顱形態分析之前，先計算兩組之間上、下顎關係的單變項分(Student's t-test)，確認兩組間上、下顎骨於水平面方向的確有差異。之後，再進行測量項目的單變項及多變項分析(賀德臨氏 T2檢定;Hotelling's T2 test)。其中，單變項分析有額外針對性別因子以及咬合因子分別做2-way ANOVA，而多變項分析也有考量性別因子。另外做組成因子分析探討構成二級第一分類異常咬的因素。結果：二級第一分類異常咬合者並非單一的表徵，可由許多異常骨骼牙齒因素的組成產生。(1) 上下顎相對於顱底之水平關係：男性及女性在上顎骨方面，長度較長但相對於顱底的位置正常。在下顎骨方面，有較後縮及形態較小的情形。(2) 上下顎相對於顱底之垂直關係：男性上顎平面較傾斜、下前顏面高度偏大、顏面開展度有較大的趨勢；女性上顎平面傾斜度正常、總前顏面高度偏大、後顏面高度較小(下顎枝較短)、下前顏面高度偏大、顏面開展度較大、下顎骨朝順時鐘方向旋轉。(3)上下顎門牙的相對關係：男性及女性門牙水平覆咬較大、門牙垂直覆咬較深。上顎門牙的傾斜度正常、較前突及過度萌發。下顎門牙唇側傾斜、過度萌發(女性下顎門牙有前突的情況)。上下顎門牙長軸交角較小。(4)上下顎第一大臼齒相對關係：男性及女性上顎第一大臼齒有往近心傾斜的現象、相對於上顎而言有過度萌發的現象。女性在下顎方面，第一大臼齒過度萌發。結論：男性與女性成人二級第一分類異常咬合群齒列顏面形態，在我們的研究樣本中除了有大小不同的差距，另外在整體的表現上也有性別的差異，因此我們認為本研究樣本存在兩性二形(dimorphism)的情況。

關鍵字

二級第一分類異常咬合；測顱分析；組成因素

並列摘要

Background: Class II malocclusion affects about 20% of the population. This type of discrepancy brings about modification in the skeletal profile caused by maxillary protrusion,mandibular retrusion, or a combination of this malocclusion. The type of Angle Class II division 1 malocclusion is the most popular dental relation in Class II malocclusion. As to the treatment, providing a good functional occlusion and a proper esthetics is a great challenge for the orthodontists. Most results from previous researches included age as an influentialfactor. The craniofacial pattern changes as one grow. Therefore, a different study on non-growing patients is advantageous in providing better diagnosis and treatment clinically. Objective: This study investigated the morphological characteristics of the craniofacial pattern in adults with Class II division 1 malocclusion. Materials and Methods: Lateral cephalograms of 80 adults with Class II division 1 malocclusionwere compared with the data from 80 adults with normal occlusion. Thirty three landmarks were identified and digitized. Cephalometric analysis utilizing 23 distances, 26 angular and 4 ratios measurements were undertaken. Before the undergoing of the Student’s t-test and multivariable analysis (Hotelling’s T2 test) of the measurements of the cephalometric analysis, the relationships of the maxilla and mandible between Class II division 1 malocclusion and normal occlusion were compared to confirm the significant difference. Besides that we also analyzed the combinations of components of Class II division 1 malocclusion. Results: The results are as followed：Multiple variations of skeletodental features were found for Class II division 1 malocclusion. (1) Skeletal horizontal relationship：In Class II division 1 malocclusion male and female both had longer maxillary length but the maxilla is in normal position related to the cranial base. The mandible is more retrusive and he morphology is smaller than normal occlusion. (2) Skeletal vertical relationship：In Class II division 1 malocclusion male had more tilting maxillary plane, longer lower anterior facial height . And the facial pattern had hyperdivergent tendency; Class II division 1 malocclusion female had longer total anterior facial height, longer lower anterior facial height and shorter posterior facial height than normal occlusion. Otherwise hyperdivergent facial pattern was noted and the mandible was clock wisely rotated. (3) Upper and lower incisor relationship：In Class II division 1 malocclusion male and female had larger overjet, deeper overbite, more protrusive and more extrusive of upper incisors, more proclined and more extrusive lower incisors (female had more protrusive lower incisors) and larger inter-incisors angle. (4) Upper and Lower 1st molar relationship：In Class II division 1 malocclusion male and female had more mesial tipping and more extrusive upper 1st molars. Female also had more extrusive lower 1st molars. Conclusions: The dentofacial characters of Class II division 1 in our samples,there were not only the different size between sex but also the wholeappearances. Because of that we defined there was sexual dimorphism in our samples.