第三大臼齒是齒列中發育變異最大的牙齒。目前許多研究結 果均顯示影響下顎第三大臼齒萌發預後因素為多因子性。
本研究的目的在利用牙科檢查時常用的測顱放射線片與環 口顎全景片，以顱顏發育已達成熟穩定的成人永久齒列為 樣本，歸納出顏面形態對下顎第三大臼齒預後的特異性，
做為研究生長發育以及牙科治療上的參考。
本研究以 116 位成年男性共 232 個下顎第三大臼齒為樣本，經 由測顱放射線片分析顏面型態與環口顎全景片分析下顎第 三大臼齒角度與位置來歸納出顏面形態對下顎第三大臼齒 萌發預後的特異性。
研究結果顯示下顎第三大臼齒角度與位置無左右側差異。下 顎第三大臼齒正常萌發與阻生者之顏面型態差異主要在上 下顎骨。正常萌發者較阻生者有較長而前突的上下顎，較 小的下顎骨體下顎枝交角與較前傾的下顎中切齒角度。
顏面型態影響下顎第三大臼齒萌發預後之相關性分 析
Prediction of 3rd molar (M3) prognosis in position and eruption are import ant clinical issues because dentists often had difficulties in making decision s as to whether mandibular M3 should be removed in orthodontic or other dental treatment. The aim of the present study was to determine radiograph ically the angulations and position of mandibular M3 in relation to facial m orphology in male adult Taiwanese.
A total of 116 university male students with a number of 232 mandibular M3 which were completely root formatted, intact lower arch, and not recei ved orthodontic treatment samples, Panoramic and cephalometric radiogra ph were taken in standardized condition. The mandibular M3 was divided i nto eruption and impaction groups to investigate the relationship between f acial morphology and the prognosis of eruption.
There was no difference on angulations and position of mandibular M3 bet ween right side and left side. Compared with the impacted group, the erupt ed group had anteriorly positioned and larger maxilla and mandible, less ra mus-corpus angle and more protrusive lower incisors.
The Influence of Facial Morphology on The Prognosis of Eruption on Lower Third Molars
