Ventä I, Murtomaa H, Turtola L, Meurman J, Ylipaavalniemi P
Department of Oral and Maxillofacial Surgery, University of Helsinki, Finland.
Br J Oral Maxillofac Surg. 1991 Aug;29(4):259-62. doi: 10.1016/0266-4356(91)90194-a.
To determine radiographic features by which one could estimate whether lower third molars are likely to erupt after the age of 20 years, university students with a total of 84 unerupted or partially erupted lower third molars were followed up. Five radiographic features of each third molar were measured from the panoramic tomogram taken at age 20 years, and the status of third molars was examined for a second time at age 26 years. The results showed that the lower third molars that did erupt after the age of 20 years were initially: 1) root formation complete; 2) impacted in soft tissue; 3) vertical; 4) placed at the same occlusal level as the neighbouring second molar; 5) showed sufficient space between the ramus and the second molar. In contrast, the teeth that remained impacted at the age of 26 years showed such initial features as: 1) incomplete root formation; 2) embedding in bone; 3) mesioangularity; 4) situated at the cervical level of the neighbouring second molar. It was concluded that a panoramic tomogram taken at age 20 years revealed radiographic features on which an estimation of future eruption of mandibular third molars could be based.
为了确定哪些影像学特征可用于估计下颌第三磨牙在20岁之后是否有可能萌出，对共有84颗未萌出或部分萌出下颌第三磨牙的大学生进行了随访。从20岁时拍摄的全景断层片上测量每颗第三磨牙的5项影像学特征，并在26岁时再次检查第三磨牙的状况。结果显示，20岁之后萌出的下颌第三磨牙最初具有以下特征：1）牙根形成完成；2）受软组织阻生；3）垂直位；4）与相邻第二磨牙处于同一咬合平面；5）下颌支与第二磨牙之间有足够间隙。相比之下，26岁时仍受阻生的牙齿最初具有以下特征：1）牙根形成不完全；2）埋于骨内；3）近中倾斜；4）位于相邻第二磨牙的颈部平面。得出的结论是，20岁时拍摄的全景断层片显示出一些影像学特征，据此可对下颌第三磨牙未来的萌出情况进行估计。
