The purpose of this study is to know about the positional change of second molar when orthodontic treatment is performed. To know about it, we andlysed cephalogram pre. and post treatment for 54 adult patients who were finished orthodontic treatment by ),ending to the first molar and classify them into 4 groups : Class I extraction group 15, Class I nonextraction group 12, Class II group 13, class Class Ill group 14.
The following conclusions were obtained :
1. In the extraction group of Class I , mandibular second molar showed less extrusion and more distal inclination than first moarl. But maxillary second molar showed more or less extrusive and mesial inclination to much the same degree of first molar.
2. Inthe non-extractio group of Class I , mandibular second molar in intrusive to first molar, it showed smilar distal
inclination to first molar. But maxillary secont molar is extrusive similarly to first molar.
a In the group of Class II, mandibular second molar is less extrusive than first molar and maxillary second molar
is more extrusive than first molar.
4. In the group of Class III, mandibular second molar showed similar extrusion to first molar and more distal inclination than first molar. But maxillary second molar showed less extrusion than fast molar.
5. A comparision of the positional change of second molar among groups : The change of distance from FH plane to funcation point of msxiillary second molar is the difference between Class I extraction group and Class II group, Class I extraction group and Class III group.
The change of maxillary second molar to palatal plane and occlusai plane is the difference between Class l extraction group and Class III group. And the change of distance from mandbular plane to furcation point of mandibular second molar is difference between Class I extraction group and non-extraction group, Class 1 non-estraction group and Class II group, Class I non-extraction group and Class III group.
But the change of angle of mandibular second molar to mandibular plane and ocelusal plane is make no difference in among groups.
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