臺灣博碩士論文加值系統

目的
此回溯性研究之目的為探討治療下顎前凸症患者之下顎後縮手術，在兩側矢向劈裂骨切開術（bilateral sagittal split osteotomy, BSSO）與口內下顎骨升枝垂直切開術（intraoral vertical ramus osteotomy, IVRO）兩種術式之間，其術後骨骼穩定性是否有所差異，並找出相關之影響因子。
病例與方法
此研究搜集了共48個在民國90年1月到95年12月之間，於台大醫院牙科部口腔顎面外科接受下顎後縮正顎手術之下顎前凸症患者。其中25人接受兩側矢向劈裂骨切開術合併剛性內固定(rigid internal fixation)，其餘23人接受口內下顎骨升枝垂直切開術合併顎間固定(intermaxillary fixation)。所有病人分別於三個時期拍攝側顱放射線影像(Lateral cephalometric radiographs )，術前一個月內(T1)、術後一週內(T2)與術後矯正完成回診時(T3)。分別描繪此三時期之側顱影像並以『best-fit』方法將其描繪影像重疊，掃描數位化後利用Winceph 8.0此矯正軟體分析其術前術後骨骼及牙齒等相關軟硬組織構造之變化。統計分析方面，利用無母數統計之Mann-Whitney test來比較兩種術式間的差異，並用線性迴歸分析來找出與術後骨骼不穩定性相關之因子。
研究結果
T2與T1兩時期影像之間，以下顎pogonion點參考點，IVRO組手術平均水平後退量為9.68公釐，而BSSO組則為6.55公釐；而在menton點上垂直方向之移動，IVRO組為向下0.12公釐，BSSO組為往上0.99公釐。而在T3與T2術後長期觀察的變化上，接受BSSO此術式的病人，下巴有往上(1.10公釐)往前(1.48公釐)移動的趨勢；接受IVRO此術式之病人，在此時期下巴則是往下(0.32公釐)往後(1.19公釐)移動。統計結果顯示：兩種術式在術後(T3-T2)骨骼的不穩定性上，在水平方向(p=.002)與垂直方向(p=.004)的變化均有顯著性的差異。
在軟硬組織變化之比例上，在BSSO組中，水平方向為1.06 (B點)、 0.88 (pogonion)、1.04 (menton)；而垂直方向為0.97 (B點)、1.00 (pogonion) 0.57 (menton)。於IVRO組中，水平方向為1.03 (B點)、0.88 (pogonion)、 1.01 (menton)；垂直方向上則是0.91 (B點)、1.00 (pogonion)、2.07 (menton)。在軟硬組織變化比例上，兩種術式間並沒有顯著性的差異。
而線性迴歸分析的結果顯示，在接受BSSO的病人上，術後在水平方向的骨骼不穩定性與年齡及關節踝的旋轉(rotation of condylar axis)有顯著性的相關；垂直方向上則與下顎平面角度(mandibular plane angle)的變化有顯著性相關。而在接受IVRO的病人上，在術後的水平方向骨骼不穩定性上具有統計顯著性的相關因子為性別、術前開咬(openbite)與下顎偏斜(jaw deviation)；垂直方向上則與年齡、下顎手術後退量、開咬及觀察期(follow-up period)長短有顯著相關。
討論
在術後骨骼不穩定性的變化模式上，BSSO與IVRO兩種術式間有顯著性的差異。根據此研究分析結果推論，最主要的關鍵原因應為關節踝的旋轉、剛性內固定和顎間固定的差異所造成的影響。
在BSSO此術式中，術中被推擠而順時鐘往後旋轉的關節踝骨塊(condylar segment)於術後觀察期間，有逆時鐘方向旋轉回來的傾向，由於下顎骨塊(tooth-bearing segment)左右均以兩支迷你骨板和兩側關節踝骨塊牢牢固定住，因此下顎會被兩側關節踝的旋轉而帶動造成手術後往前往上的移動。
但在IVRO此術式中，術後骨骼的重新塑形(remodeling)作用主要發生在顎骨切開處，由於下顎骨塊與兩側關節踝骨塊並非剛性固定，因此下巴並不會隨著關節踝的旋轉而移動。再加上顎間固定的應用對下臉部高度(lower facial height)造成增加的效果，因此，下巴在術後觀察期間有往後往下移動的趨勢。

Purpose
The purpose of this retrospective study was to compare post-operative changes and skeletal stability between bilateral saggital split ramus osteotomy (BSSO) and intraoral vertical ramus osteotomy (IVRO) used for mandibular setback. Factors contributing to skeletal instability were also identified.
Patients and Methods
The study included 48 patients with mandibular prognathism, who underwent mandibular setback surgery at the Department of Oral and Maxillo-facial Surgery, National Taiwan University Hospital (NTUH) from January 2001 to December 2006. Twenty-five of them recieved with rigid internal fixation, the remaining 23 underwent IVRO with intermaxillary fixation. Lateral cephalometric radiographs were taken within 1 month before surgery (T1), immediately after the operation (within 1 week, T2), and at the time of completion of post-op orthodontic treatment (T3). The T1,T2, and T3 radiographs were traced and superimposed with “best-fit” technique and the data were digitalized to analyze the changes at T2-T1 and T3-T2. Mann-Whitney test was used to verify the differences in post-operative changes and long-term skeletal stability between the two groups. And the linear regression model was established to find the contributing factors.
Results
The mean amount of horizontal setback at pogonion was 6.55 mm in BSSO group and 9.68 mm in IVRO group. The mean amount of vertical movement at menton was 0.99 mm upward in BSSO group and 0.12 mm downward in IVRO group. Long-term observation (T3-T2) showed that the chin moved upward (1.10 mm) and forward (1.48 mm) after BSSO, and moved downward (0.32 mm) and backward (1.19 mm) after IVRO. Significant differences were noted between the two procedures in horizontal skeletal instability at pogonion (T3-T2, p=.002), and vertical skeletal instability at menton (T3-T2, p=.004).
In BSSO group, the horizontal soft/hard tissue ratio was 1.06 at B point, 0.88 at pogonion, 1.04 at menton. And the vertical soft/hard tissue ratio was 0.97 at B point, 1.00 at pogonion, 0.57 at menton. In IVRO group, the horizontal soft/hard tissue ratio was 1.03 at B point, 0.88 at pogonion, 1.01 at menton. And the vertical soft/hard tissue ratio was 0.91 at B point, 1.00 at pogonion, 2.07 at menton. No significant difference was found in the soft/hard tissue ratio.
In BSSO group, the significant predictor for the horizontal skeletal instability was age and rotation of condylar axis. For vertical skeletal instability, it was significantly correlated to change of mandibular plane angle.
In IVRO group, the significant predictors for horizontal skeletal instability were gender, openbite, and jaw deviation. And vertical skeletal instability was significantly correlated to age, amount of horizontal setback, grade of openbite, and follow-up period.

Discussion
The patterns of post-operative instability are significantly different between BSSO and IVRO. The key factors contributing to this difference was considered be the change in condylar axis and the application of RIF or IMF. In BSSO, the tooth-bearing segment was rigidly fixed with the bilateral condylar segments. Therefore, the chin moves upward and forward as the condylar axis rotates counter-clockwise post-operatively. But in IVRO, osseous remodeling takes place at the osteotomy site. The chin may not move while the condylar axis rotates counter-clockwise post-operatively. Moreover, the application of IMF will lead to an increase of lower facial height. Thus, the chin moves downward and backward after the surgery.

口試委員會審定書…………………………………………………i
中文摘要……………………………………………………………………ii
Abstract……………………………………………………………v
Introduction………………………………………………………1
History of Surgical Treatment of Mandibular prognathism…1
IVRO vs. BSSO Advantages and Disadvantages…………………2
Skeletal Stability and Relapse after Ramus Surgery………5
Change of Soft Tissue Profile…………………………………9
Comparison between BSSO and IVRO……………10
Patients and Methods………………………………………………12
Results………………………………………………………………19
Intra-personal and Inter-personal Calibrations…………19
Immediate Skeletal Changes after the Surgery……………20
Long-term Skeletal and Dental Changes (T3-T2)……………23
Soft Tissue Changes (T3-T1)……………………………………25
Comparison between BSSO and IVRO……………………………26
The Effect of Skeletal Intermaxillary Fixation…………28
Factors Contributing to Skeletal Instability……………29
Discussion…………………………………………………………36
Conclusions………………………………………………………46
Tables and Figures……………………………………………47
References………………………………………………………73

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