- 學位論文
安格式三級異常咬合兒童中臉部與下顎幾何形態學分析
Geometric Morphometry of the midfacial complex and mandible in children with Angle Class III malocclusion
摘要
本研究之目的，針對國人安格式三級異常咬合兒童之顏面骨骼形態，以新的形態分析法：有限元素分析、主應變張量變化及薄板仿樣分析，研究其與正常咬合者之中臉部和下顎的形態差異；並與傳統測顱分析法相互對照。採用台灣三級異常咬合兒童（未受矯正治療）(年齡為9歲5個月到11歲8個月)共70位；與性別、年齡符合之正常咬合兒童共70位做對照。在側面測顱X光片上，點選10個中臉部標記點和12個下顎標記點，由數位板將標記點位置以XY座標形式輸入點腦進行運算，並使用普氏疊合分析法分別得到各組的中臉部及下顎平均圖形，來進行形態分析；其結果顯示三級異常咬合與正常咬合者之中臉部平均形態及下顎平均形態，的確有顯著之差異。統計分析的結果，男孩三級異常咬合者的下中臉部水平長度(A-PNS及MPP- PNS)是縮短的，前齒槽骨角度(ANS-A-Pr)也變小。女孩三級異常咬合者則同樣有縮短的MPP-PNS長度，此外，前中臉部高度(Rh-Pr及Rh-A)也縮短。在下顎方面，三級異常咬合者的下顎長度(Ar-Gn及Ar-Pog)均較長。男孩有較長的下顎體長度(Go-Pog及Go-Gn)和較大的頦上角(Cd-Gn-B)；女孩則表現出下顎枝高度(Ar-Go)增大、下顎枝寬度(Ab-Pb)縮窄。圖示分析法顯示，三級異常咬合者前鼻棘均增大。此外，男孩上顎門齒齒槽有明顯前傾，女孩則有後傾現象。男女孩後下中臉部(上腭後半部)都是縮小的，而女孩前上中臉部亦有顯著縮小情形，顯示鼻尖點較為低位。三級異常咬合者的下顎枝上半部、下顎體、下顎齒槽、下顎聯合區及頦區有尺寸增加及形狀變化；髁頭區則有顯著尺寸縮小和形狀變化。此外，男孩之下顎門齒齒槽有尺寸增大及形狀變化，其下顎枝下半部(包括下顎角區)亦有縮小變化。由本研究結果可知，國人三級異常咬合兒童有縮短的後下中臉部、凹陷的下中臉部以及縮小的前中臉部(女孩)；而下顎有過度前後方向的生長、髁頭區向下壓縮和反時針(向前)旋轉的生長傾向；在下顎頦區與下顎聯合區，有相當明顯前上到後下方向的水平擴張。這些因素使國人三級異常咬合兒童呈現上顎後 縮和下顎骨前突的外觀輪廓。
並列摘要
The purpose of this study was to evaluate the morphometric differences of the midfacial complex and mandible between normal occlusion and Angle Class III malocclusion. Also, by the use of finite element morphometry, principal strain tensor, and thin-plate spline analysis, the size and shape changes of the midface and mandible in subjects with Class III malocclusion can be localized. A total of 140 lateral cephalographs of children of Taiwanese with either a normal occlusion or an Angle Class III malocclusion were compared. Each group included equal numbers of age and sex-matched samples. The cephalographs were traced and checked, and ten landmarks on the midfacial complex and twelve landmarks on the mandible were identified and digitized. The datasets were scaled to an equivalent size and subjected to statistical analyses. These tests indicated significant differences between average normal occlusion and Class III midfacial and mandibular configurations. The results of Student t-test showed that the lower midfacial horizontal length (A-PNS and MPP-PNS) and the anterior alveolar angle (ANS-A-Pr) were reduced in Class III boys. The anterior midfacial height (Rh-Pr and Rh-A) in addition with the length of MPP-PNS were significantly reduced in Class III girls. Increased mandibular length (Go-Pog and Go-Gn) and larger supramental angle (Cd-Gn-B) were noticed in Class III boys; while the Class III girls had elongated and narrowed mandibular ascending ramus. The graphical analyses showed more prominent anterior nasal spines in Class III children; positive size and shape changes in maxillary incisal alveolar process, which indicated proclination of maxillary incisors. The posterior-inferior region of the midface was compressed in Class III samples. Significant reduction within the anterior-superior portion of the midface in Class III girls, suggested downward movement of the nasal tip (rhinion). Localized shape changes and increased size changes were revealed in the superior portion of the ramus, the mandibular body, the mandibular dentoalveolar process, the symphyseal area and the mental area. Vertical compression of the Cd (condylion) and significant shape change around the condylar area were prominent features in Class III malocclusions. It is concluded that, in this study, Class III children had shortened posterior-inferior midfacial length, compressed inferior and anterior midfacial complex, overdeveloped anterior-posterior mandibular growth, downward compression of the condyle and anterior (counterclockwise) rotation of the mandible, and prominent extension between the mandibular symphyseal and the mental area, leads to the appearance of a Class III retrusive maxillary and prognathic mandibular profile.