Harada Y, Tomino S, Ogawa K, Wada T, Mori S, Kobayashi S, Kiyosue T, Kubo H
Shika Kiso Igakkai Zasshi. 1989 Feb;31(1):13-8. doi: 10.2330/joralbiosci1965.31.13.
The frequency of three rooted mandibular first molars was surveyed. Subjects were of 1,353 male and female students trained in radiology at Fukuoka Dental College whose average age was 24.3 years old. Dental (complete radiographic survey using 14 films) and panoramic radiographs of their mandibular first molars were taken during a period of 9 years from 1978 to 1986. The results were as follows: 1) The number of the three-rooted mandibular first molars was 440 (18.8%) of 2,331 teeth, including 240 (20.6%) of 1,163 in the right side and 200 (17.1%) of 1,168 in the left. 2) 274 (11.8%) of the three-rooted mandibular first molars were identified by radiographs of the premolar region, 42 (1.8%) by radiographs of the molar region, 124 (5.3%) by radiographs of both the premolar and the molar region. 3) Panoramic radiography identified 70 (15.9%) out of 440 three-rooted mandibular first molars. 4) 136 (12.7%) of 1,070 subjects who had bilateral mandibular first molars had three-roots on both sides 127 (11.9%) of 1,070 had them on one side.
对三根下颌第一磨牙的发生率进行了调查。研究对象为福冈牙科学院1353名接受放射学培训的男女学生，平均年龄24.3岁。在1978年至1986年的9年期间，拍摄了他们下颌第一磨牙的牙科X光片（使用14张胶片进行完整的X光检查）和全景X光片。结果如下：1）在2331颗牙齿中，三根下颌第一磨牙的数量为440颗（18.8%），其中右侧1163颗中有240颗（20.6%），左侧1168颗中有200颗（17.1%）。2）通过前磨牙区X光片识别出274颗（11.8%）三根下颌第一磨牙，通过磨牙区X光片识别出42颗（1.8%），通过前磨牙区和磨牙区X光片识别出124颗（5.3%）。3）全景X光检查在440颗三根下颌第一磨牙中识别出70颗（15.9%）。4）在1070名双侧下颌第一磨牙的受试者中，136名（12.7%）双侧有三根，1070名中有127名（11.9%）一侧有三根。
