A PATTERN OF THE FORMATION AND ERUPTION OF FIRST PERMANENT MOLARS

Among the permanent teeth, the first permanent molars play the greatest role in occlusion and function. So, early diagnosis for congenital missing, abnormal eruption and abnormal formation is very important to the first permanent molars in the course of arch development. The aim of this study is to analyse the differences between right and left first permanent molar's formation and eruption and between upper and lower one. A total of 545 children were selected am ong children who had visited our clinic, investigate eruption and calcification stage of permanent first molar, based on Gleiser and Hunt criteria for this study. 1. Gingival emergence of mandibular first molar is faster than maxillary first molar by 0.75~0.8 years, gingival emergence of maxillary first molar in girls faster than boys by 0.45 years, and that of mandibular first molar in girls faster than boys by 0.5 years. 2. There is the significant difference between right and left first molar on the eruption score and the calcification stage ; 5 year old children show the significant difference on the eruption score. 7 year old children show the significant difference on both the eruption score and calcification stage. 3. It shows the most active eruption movement of crown on the maxilla while the root is rapidly widening its furcation and completing root formation to 2/3, on the other hand, the most active crown emerging on mandible is shown when the root formation completed to 1/4 to 1/2.