前牙開咬之齒顎顏面形態測量學之探討

臨床上，影響開咬的因子相當多樣化，基因遺傳或者周遭環境都會在顱顏結構生長發育時產生影響，但回顧過去文獻，骨骼形態與開咬間的關係尚未明朗，而國內對此部分的研究與資料也較缺乏。本研究主要目的在於探討國內開咬異常咬合者間顱顏結構與齒列關係的特徵，進而幫助臨床上的診斷與治療方式選擇所需。研究方式是選取正常咬合男女各40名以及開咬異常咬合男女各40名，年齡在17歲到25歲間，共採用33個標記點，分別描繪其側顱片與經數位板輸入電腦計算處理，傳統測顱分析包括23項線段、24項角度項目與4項比值。進行顱底形態分析前，先計算開咬與正常咬合各對應組垂直覆咬（overbite）的確有差異，之後再進行測量項目單變項分析與2-way ANOVA，做進一步探討。結果如下述：骨性一級、二級與三級合併開咬者主要的差異存在於水平顎間關係上，垂直方向關係則彼此類似，男女間除線段差異較大外，其餘角度關係差異性不大；開咬者顱底角度與線段上與正常咬合組並無統計上的顯著差異；開咬者顏面開展度較正常咬合者大，其平均前全顏面高度較正常咬合者高，其中又以前下顏面高度增加幅度最多。前上顏面高度與後顏面高度則沒有統計上的差異；腭平面與正常咬合者相較，開咬者並無較傾斜之情況；開咬者的下顎平面角與SN、FH或者PP相比角度都顯著增加，推論為下顎產生順時針旋轉所致。同時開咬者的下顎枝顯著偏短，且角點角也顯著偏大；不論前牙或者後牙垂直高度都顯著偏大，但只有後牙的長軸均較向近心傾倒，前牙部分則無顯著差異。同時研究發現，大部分牙齒的位置皆較前位，意味開咬者的上下齒列都屬於前凸。因此，骨性一級、二級與三級合併開咬異常咬合者相較於正常咬合主，在顱顏結構與齒顎關係上的確有所差異存在。

關鍵字

開咬；異常咬合；形態測量學；測顱分析

並列摘要

Clinically, open-bite is affected by multi-etiology. Genetic factors or surrounding environment may influence the growth and the development of craniofacial structures. Reviewing the past literatures, the relationship between the skeletal morphology and open-bite is still controversial; The research data in Taiwan is too few to be contributory. Therefore the purpose of this study was to investigate the morphological characteristics of the craniofacial structures in people with open-bite malocclusion. Hopefully this study can be used as a future reference in clinical diagnosis and treatment. Lateral cephalograms of untreated 80 patients with open-bite were compared with 80 people with normal occlusion. The ages of the samples ranged from 17 years old to 25 years old. Thirty-three landmarks were traced, identified and digitized. Cephalometric analysis utilizing 23 linear, 24 angular measurements and 4 ratios were undertaken. Before the undergoing of the Student’s t-test and 2-way ANOVA of the measurement of the craniofacial structures, the amount of the overbite of open-bite patients and normal occlusion patients were compared to confirm there’s the significant differences between these two groups. The results are as follows: the main differences between the open-bite combined skeletal Class I, II or III exist almost in horizontal relation, but are similar in vertical relation. Only linear measurements differ between the male and the female. There is no significant difference in the angular or linear measurements of cranial base between the open-bite and the normal groups. The angular measurements of the facial pattern and the PFH/AFH ratio of the open-bite group are statistically significant compared with the normal. The average of ATFH of the open-bite group is more than the average of ATFH in the other group, most of the increased amount rising from the ALFH. The AUFH and PFH have no statistically significance between two groups. The palatal plane of the open-bite group, compared with the normal group, shows no excessive tilting though. The mandibular plane angle, whether compared with SN, FH and PP, is significantly increased statistically, possibly resulting from the clockwise rotation of the mandible. The shorter ramal length and obtuse gonial angle are shown in the open-bite group. The vertical heights of both anterior and posterior teeth in open-bite group are increased significantly. The long axis of posterior teeth tilts toward mesially, but there is no difference in the anteriors. In this study, almost all teeth positon more anteriorly in the open-bite group, indicating a tendency of dentoalveolor bimaxillary protrusion. Therefore, skeletal Class I, II and III combined with anterior open-bite groups do differ from the normal group in craniofacial structures and dental relation.