骨性二級異常咬合合併下顎後縮患者齒顎顏面形態特徵的探討

Dentofacial Morphology of Skeletal Class II Malocclusion with Mandibular Retrusion

目的：探討成年骨性二級異常咬合合併下顎後縮患者齒顎顏面形態之特徵。方法：比較80名骨性二級異常咬合合併下顎後縮（∠ANB > 5 , ∠FNB < 86 ）的成年人與80名正常咬合成年人的側面測顱放射線圖（兩組男女人數相同）。共採35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30 項線段、29項角度、4項比值。進行測顱項目的單變項及二因子變項分析（2-way ANOVA）。結果：骨性二級異常咬合合併下顎後縮患者：（1）有較長的前顱底，但顱底角及鞍角跟正常咬合者無異。（2）有較長的上顎骨，但上顎骨相對於顱底並沒有前突現象。下顎骨長度則是呈現較短及較小的情形，下顎枝前後緣寬度則可能因代償性生長而有變寬的情形，但下顎相對於顱底而言呈現較後縮的現象。（3）上顎平面、下顎平面、下顎枝平面以及咬合平面較傾斜；前顏面高度較大（上前顏面高度及下前顏面高度都偏大）、後顏面高度偏小（下顎枝較小），顏面展開度有較大情形，下顎骨朝順時鐘方向旋轉。（4）上顎門牙的傾斜角正常，但有過度萌發情形。下顎門牙朝唇側傾斜，並有過度萌發情形。上下顎門牙長軸交角較小，門牙水平覆咬較大，垂直覆咬較深。（5）上顎第一大臼齒向近心傾斜，並有過度萌發情形。且下顎第一大臼齒有近心傾斜、較後縮及過度萌發情形。結論：骨性二級異常咬合合併下顎後縮患者的齒顎顱顏形態並非單一的表徵，可由許多骨骼牙齒因素的組成產生。

Objective: The aim of this study was to investigate the morphological characteristics of the craniofacial pattern in skeletal Class II adults with mandibular retrusion. Materials and methods: Lateral cephalograms of 80 adults with skeletal Class II malocclusion with mandibular retrusion (∠ANB > 5°, ∠FNB < 86°) compared with 80 adults with normal occlusion (equal sexes in both groups). Thirty five landmarks were identified and digitized. Cephalometric analysis utilizing 30 linear, 29 angular and 4 ratio measurements were undertaken. Statistical comparison of the two groups was performed with Student's t-test and 2 way-ANOVA. Results: (1) The skeletal Class II sample with mandibular retrusion had longer anterior cranial base length but the internal cranial base angle and the saddle angle were not different from the normal occlusion subject. (2) The sample with mandibular retrusion had longer maxillary length but the maxilla was in normal position related to the cranial base. The mandible was more retrusive and smaller but the ramus width was wider than normal occlusion subject due to compensatory growth. (3) The mandibular retrusion sample had more tilting maxillary plane, mandibular plane, ramus plane and occlusal plane. The sample had longer total anterior facial height, longer upper and lower anterior facial height and shorter posterior facial height (shorter ramus height) than normal occlusion subjects. Hyperdivergent facial pattern and the mandible rotated clockwisely were noted. (4) The mandibular retrusion sample had extrusive but normal inclined upper incisors, more inclined and extrusive lower incisors, smaller interincisal angle, larger overjet and deep overbite. (5) The mandibular retrusion group had more mesial tipping and more extrusive upper 1st molars. Besides, more mesial tipping, more retrusive, and more extrusive lower 1st molars were noted. Conclusion: Multiple variations of skeletodental features were found for skeletal Class II malocclusion with mandibular retrusion.