THE STUDY OF THE ERUPTION PATTERN OF THE MAXILLARY FIRST PERMANENT MOLAR

상악(上顎) 제1대구치(第一大臼齒)의 맹출과정(萌出過程)에 관(關)한 연구(硏究)

To Study the eruption pattern of the maxillary first permanent molar, the author took 266 cases of true lateral cephalogram (Male; 137 cases, Female; 129 cases) from 3 to 7 years old children and observed the vertical change and axial change. The following results were obtained: 1. The angle of axial inclination of the maxillary first permanent molar to the F-H plane increased gradually from age 3 to 7, except for age 6 in both sexes. There was a slight reversal of this motion at age 6. 2. The distance from the cusp of the maxillary first permanent molar to the occlusal plane slightly decreased from age 3 to 5, and rapidly decreased from age 5 in both sexes. 3. The change of angle of the axial inclination resulted in the distance from the distobuccal cusp of the maxillary first permanent molar to the occlusal plane decreasing more than that from the mesiobuccal cusp of the maxillary first permanent molar to the occlusal plane in both sexes. 4. The eruption of the maxillary first permanent molar generally was found to be earlier in girls than boys.