骨性三級異常咬合之顏面不對稱及手術矯正治療效果 三維分析

Three-dimensional analysis on surgical-orthodontic treatment outcome of facial asymmetry in skeletal Class III malocclusion

呂紹群(Shao-Chun Lu)

指導教授 ： 陳羿貞

共同指導教授 ： 郭生興(Sang-Heng Kok)

國立臺灣大學/牙醫專業學院/臨床牙醫學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.01565

摘要

中文摘要
目的:
本院矯正科與口腔外科合作的矯正合併正顎手術病例中，大部分的患者為骨性三級咬合，此類患者常見合併顏面不對稱的特徵。本研究目的是希望利用正顎手術患者治療前後的三維影像，以分析整體的治療成效，及整體外觀的改變，幫助我們對顏面不對稱的形態有更深入的認識， 並且建立臨床上適合使用的顱顏不對稱分類方式，提供後續診斷之用。
實驗材料及方法:
本研究的對象是在台大醫院進行矯正合併正顎手術的38位患者，患者於治療前(T1)，整體治療結束並拆除矯正器後三個月內(T2)，分別拍攝CBCT影像。檢查儀器為i-CAT CBCT scanner，影像分析軟體為Dolphin imaging system。透過將患者術前影像定位(orientation)，定義Ba為原點及正中矢狀切面(通過Ba , N , S)水平基準面(通過左右側Po, Or 投影於正中矢狀切面的中點，並垂直矢狀切面)與冠狀面(與矢狀切面及水平面垂直)。分組的定義為Group 1: Menton deviation≥Ramus width difference≥0, Group 2: Ramus width difference>Menton deviation≥0, Group3: Menton deviation>0, Ramus width difference<0。為了有效分析治療前後的變化，將治療後CBCT影像與治療前影像疊合，以分析治療後顏面不對稱改變程度，為了分析proximal segment於手術後的變化。將下顎骨外緣從mandibular notch到下顎骨角之間每隔3mm記錄一個界標點，紀錄投影於冠狀面及水平面上的座標值，以瞭解proximal segment的側向移動。
結果:
全部38位患者有的平均下頦點偏斜4.07±3.13mm。Group1患者13位，特徵為具有較大的下頦點偏斜，(平均6.29±3.49 mm)。Group2患者9位，其下頦點偏斜(Me deviation)最小(平均2.08±1.49mm)。不對稱問題主要與下顎枝寬度差異有相關。Group3患者16位，下頦點歪斜平均3.38±2.47 mm。與Group1及Group2兩組相反，非偏斜側的下齒槽神經管最後上緣與正中矢狀切面距離(Mandibular foramen-Mid),非偏斜側下顎枝寬度(Ramus width)寬度大於偏斜側。並且下齒槽神經管最後上緣與通過Ba點之冠狀面距離(Mandibular foramen-Cor),頦孔最前上緣與通過Ba點之冠狀面距離(Mental foramen-Cor)具有前後向不對稱，非偏斜側較偏斜側位置前方。
治療後Group 1顏面不對稱的改善包括下頦點偏斜減小，兩側上顎第一大臼齒近心頰側咬頭與正中矢狀切面的差值(Arch width discrepancy)減小。非偏斜側的下顎上升枝外緣與水平面夾角(non-deviated side Ramus angle)往外側傾斜，非偏斜側下顎上升枝由傾斜回正1.82°。
Group 2 顏面不對稱的改善主要也是下頦點偏斜減小，偏斜側Ramus width寬度減小，非偏斜側Ramus width寬度略增加。
Group 3治療前後有顯著改善的部位僅在Me deviation。左右下顎枝的寬度及兩者差異量，在治療前後數值並無明顯變化。
結論:
本研究將顏面不對稱的患者依下頦點偏斜與下顎枝寬度的差異(Ramus width difference)的相對關係將患者分成三類，其不對稱形態及不對稱的部位各有不同。各組的患者在治療結束後，下頦點偏斜均有明顯改善，但其中二類(Group 1, Group 2)的患者其下顎枝不對稱與下頦點偏斜的情形，同時改善，另外一類(Group 3)的患者，則多數僅能改善下頦點偏斜，兩側下顎枝寬度差異在治療前後並無顯著差異。

關鍵字

錐狀射束斷層掃描 ； 三級異常咬合 ； 顏面不對稱 ； 正顎手術

並列摘要

Objectives: Most of the patients receiving surgical orthodontic treatments in National Taiwan University Hospital (NTUH) exhibit Class III skeletal pattern with mandibular prognathism. It is common that skeletal Class III patients have the feature of facial asymmetry. The objective of this research is to study the CBCT (Cone beam CT) image of skeletal Class III patients before and after surgical orthodontic treatments. This would help us to have more insight into the surgical treatment for Class III patients with facial asymmetry.
Method: 38 patients underwent surgical orthodontic treatment in NTUH were included in this research. CBCT was taken before full mouth orthodontic treatment (T1) and within 3 months after debanding and debonding of brackets (T2) by using i-CAT CBCT scanner. Dolphin imaging system was utilized for image analysis. Ba was defined as the origin of the 3-dimensional coordinates and the image was oriented according to the following reference planes. The midsaggital plane was defined as the plane that passed through N, S, Ba and the horizontal reference plane was defined as the plane that was perpendicular to midsaggital plane and passed through the midpoint of bilateral Po, Or projecting to midsaggital plane. Coronal plane was defined the plane that was perpendicular to saggital and horizontal plane. After orientation of T1 image was performed, T2 image was superimposed to T1 image according to the best fit of cranial base structures. Thus, the differences of each landmark between T1 and T2 images could be measured by calculating the coordinates. To analyze the movement of proximal segments, the border of ascending ramus was projected onto coronal plane and analyzed sequentially at different levels from the level of mandibular notch to the level of gonial angle. The patients were grouped according to the relationship of Menton deviation and bilateral Ramus width difference to characterize the facial asymmetry. The criteria of grouping was as follows:
Group 1: Menton deviation≥ Ramus width difference≥0
Group 2: Ramus width difference> Menton deviation≥0
Group3: Menton deviation>0, Ramus width difference<0
Results: Average Menton deviation of the 38 patients was 4.07±3.13mm. 13 patients were classified into Group 1, and the average Menton deviation of Group 1 was 6.29±3.49 mm. Nine patients were classified into Group 2 ,and the average Menton deviation was 2.08±1.49mm. The asymmetry pattern of the Group 2 patients was associated with the differences between distances from ramus to midsaggital plane. 16 patients were classified into Group 3, and the average Menton deviation was 3.38±2.47 mm. In contrast to Group 1 and Group 2, Group 3 patients has more prominent gonial angle at non-deviated side. Besides, the position of mental foramen and mandibular foramen were more forward at the non-deviated side compared to the deviated side. For Group 1 patients, the Menton devaiton , Ramus width difference , and arch form discrepancy were improved after treatment. For Group 2 patients, Menton deviation and Ramus width difference improved after surgery. As to Group 3 patients, the treatment corrected Menton deviation, but not the Ramus width difference.
Conclusion: CBCT 3 dimensional image is helpful in the analysis of skeletal Class III patients with facial asymmetry. The parameter of Menton deviation and bilateral Ramus width difference were feasible for diagnosis and surgical-orthodontic treatment plan of skeletal Class III patients. The asymmetry patterns were different among the three groups. Menton deviation and Ramus width difference may be corrected after treatment for Group 1 and Group 2 patients. However, for Group 3 patients, the treatment only corrected Menton deviation but not the Ramus width difference.

並列關鍵字

cone beam computed tomography ； Class III malocclusion ； facial asymmetry ； orthognathic surgery

參考文獻

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