安格氏第三類型咬合不正合併下顎前凸的患者，顏面特徵會隨著嚴重程度呈現直臉型至凹臉型的外觀，患者除了美觀的因素外，咀嚼功能障礙、發音問題、人際關係與心理因素都會促使這類患者尋求臨床的診治。治療嚴重的安格氏第三類型咬合不正的患者，通常須要配合正顎手術合併牙齒矯正。本研究的目的在於探討以全口矯正合併口內下頷枝垂直截骨術（Intraoral Vertical Ramus Osteotomy，簡稱IVRO）將下頜後退的第三類型咬合不正合患者，其下顏面部軟組織與下頷骨後退量的關係。
本實驗的患者的收集對象是2009年到2010年在中山醫學大學結束矯正治療的患者共21位，其中11位是男性、10位是女性，皆為台灣人，他們都屬於第三類型咬合不正(ANB : - 4° ; Wits: -14.1 mm) ，只接受傳統牙齒矯正合併口內下頷枝垂直截骨術之正顎手術來治療下頜前凸，並用顎間固定( Maxillo-mandibular Fixation，簡稱IMF) 固定六週。我們收集治療前(T0)、手術前(T1)和治療後(T2)的側頭顱x光片，測量軟組織與硬組織的變化，利用 paired t test 做分析。患者的平均年齡是22.9 ±3.9歲，平均治療時間為25.9個月。
本實驗結果顯示：
（1）ANB角度治療前平均-4.04度; 治療後平均1.33度，平均增加5.37度。
（2）鼻唇角（Nasolabial angle，簡稱NLA）治療前平均91.49度; 治療後平均102.69度，平均增加11.20度。
（3）Wits A/B 的距離治療前平均-14.14 mm ; 治療後平均-5.71 mm，平均減少8.43 mm。
（4）手術前與治療後下頷骨後退的量，是以硬組織Pog為代表，平均
後退量為10.93 mm ; 而下顏面部軟組織則分為五部份檢視：上唇最凹（sls）平均後退量為0.60 mm ; Pog / sls 退後的比例是 1: 0.05、上唇最凸點（ula）平均後退量為1.45 mm ; Pog / ula 退後的比例是 1:0.13、下唇最凸點（ils）平均後退量為8.69 mm ; Pog / ils 退後的比例是1:0.79、下唇最凹點（ila）平均後退量為7.29 mm ; Pog / ila 退後的比例是 1: 0.66 ；軟組織pog平均後退量為9.30 mm ; Pog / pog退後的比例是 1: 0.85。
藉由 ANB角度變化、 鼻唇角的增加與 Wits A/B 距離的縮短，本實驗證明手術後下頜前凸的臉型有顯著的改變。下顏面部的軟組織相對於下頷骨後退的量，其變化會因部位不同，而有不一樣比例的後退量。而未來若能收集更多病例，所獲得的資料，對臺灣人第三類型咬合不正合併下顎前凸的患者，術前預測正顎手術後顏面改變將有很大助益！
and orthognathic surgical procedures. The aims of this study were to investigate the profile changes in lower face and the correlations between soft and hard tissue changes in Angle’s Class III malocclusion cases after mandibular setback surgery with intraoral vertical ramus osteotomy (IVRO) approach.
The sample of this study included 21 Taiwanese patients (11 males, 10 females) with skeletal Class III malocclusion (ANB : - 4°; Wits: -14.1 mm). All the 21 patients have completed a combined fixed orthodontic treatment and orthognatic surgical treatment with IVRO mandibular setback and six weeks of maxillo-mandibular fixation at Chung Shan Medical University Hospital during 2009 and 2010. The pretreatment (T0), pre-surgical (T1) and post-treatment (T2) lateral cephalographs were collected. All the soft and hard tissue changes were measured and analyzed by paired t test. In this study the mean patient’s age was 22 ±3.9 years, and mean treatment time was 25.9 months.
The results of this study showed that:
(1)The mean ANB angle increased 5.37° (pretreatment ANB - 4.04°; post-treatment ANB 1.33 °).
(2)The mean Nasolabial angle increased 11.20°. (pretreatment Nasolabial angle 91.49°; posttreatment Nasolabial angle 102.69 °).
(3)The mean Wits A/B distance decreased 8.43 mm. (pretreatment Wits A/B -14.14 mm; post-treatment Wits A/B 5.71 mm) .
(4)The patients underwent mandibular surgery had an average of 10.93 mm setback at the osseous pogonion (Pog). Five parts of the soft tissue were analyzed and revealing that: (a). the mean setback at most retrusive point of upper lip (sls) was 0.60 mm , the setback ration of Pog / sls was 1:0.05 ; (b). the mean setback at most protrusive point of upper lip (ula) was 1.45 mm , the setback ration of Pog / ula was 1:0.13; (c) . the mean setback at most protrusive point of lower lip (ils) was 8.69 mm , the setback ration of Pog / ils was 1:0.79 ; (d). the mean setback at most retrusive point of lower lip (ila) was 7.29 mm , the setback ration of Pog / ila was 1:0.66 . And the last analysis showed that mean soft tissue pogonion (pog) was setback 9.30 mm, the setback ratio of hard to soft tissue pogonion Pog/pog was1:0.85.
This study showed that mandibular setback surgery was effective for improvement of adult Class III prognathic profile by significant changes seen in ANB angle , Nasolabial angle and the distances of Wits A/B. The soft tissue changes of the lower face differed at different parts (pog, sls, ula, ils, and ila as in this study), and the soft to hard tissue ratio also different in subjects with mandibular prognathism. We hope more cases can be collected to obtain more detail data that would be helpful in surgical prediction for prospective Taiwanese Class III orthognathic surgery patients
