安格氏二級異常咬合第一分類合併嚴重微笑露齦之改善

Orthodontic Correction of Severe Gummy Smile in Class II Division 1 Malocclusion: A Case Report

臨床上治療安格氏二級異常咬合第一分類合併微笑露齦的病人，經常為了改善上顎齒槽前突的外觀和笑齦，必須作到適當的上顎門齒後退和壓入；然而門齒後退過程中，需要良好的生物機械力學設計才能同時達成門齒壓入和維持良好的扭矩控制。本病例為19歲女性，因臉型外突及嚴重笑齦前來求診，診斷為安格氏二級異常咬合第一分類，微笑時牙齦露出大於 5 mm，上下顎齒列些微擁擠且門齒水平覆咬達 6 mm，測顱分析顯示為骨性二級關係異常合併下顎骨後縮，齒列則呈現代償現象，犬齒與臼齒咬合關係皆為安格氏二級異常。治療計畫為拔除上顎左右第一小臼齒，為達成有效之上顎門齒壓入和扭矩控制，在上顎顴骨下骨脊（infrazygomatic crest）及上顎正中門齒間根尖下（sub-apical）植入迷你骨釘作為骨性錨定，並請病人自行配戴第三級橡皮筋以避免下顎門齒向唇側傾斜。經過20個月的矯正治療，病人微笑露齦有明顯改善，並且達到穩定良好的咬合關係，測顱重疊分析發現上顎門齒有顯著後移及壓入，下顎骨向前上旋轉，齒顎關係的變化有利於改善顏面外觀，本病例報告顯示傳統矯正合併上顎後牙及前牙區的迷你骨釘，有助於改善二級異常咬合第一分類病人的臉型及微笑露齦。

Class II division 1 malocclusion with deepbite and gummy smile can be treated in several ways. Adequate intrusion and retraction of maxillary incisors may improve the smiling appearance as well as the facial profile. However, anterior torque control can be challenging. Herein, we report a patient with 5 mm gummy smile, where the final esthetic improvement was achieved by combined use of posterior and anterior miniscrews. The 19-year-old women presented with lip protrusion, convex profile, retrusive chin, excessive gingival display, and a Class II division 1 malocclusion with mild crowding in the upper and lower dentition (1~2 mm). Cephalometric analysis showed the dental compensation to the Class II skeletal pattern with mandibular retrusion (ANB = 7.5°, MPA = 42°, U1-SN = 99°, L1-MP = 99°). The treatment plan included single arch extraction and installation of 3 miniscrews as bony anchorage. The maxillary first premolars were extracted for anterior teeth retraction and overjet correction. Two miniscrews were placed at the infrazygomatic crest of maxilla and one at the cortical bone sub-apical to maxillary incisors for retraction, intrusion, and torque control of anterior teeth. Furthermore, Class III elastics were used to prevent labial flaring of mandibular incisors. Gummy smile was obviously improved and stable occlusal relationship were established after treatment. The total treatment duration was 20 months. The cephalometric analysis showed significant intrusion and retraction of maxillary incisors as well as a slight counterclockwise rotation of mandible. This case demonstrated that the combined use of posterior and anterior miniscrews could be an effective procedure for torque control and genius intrusion of maxillary incisors in the treatment of severe dentoalveolar protrusion and gummy smile.