• The korean journal of orthodontics
• /
• v.23 no.1 s.40
• /
• pp.47-55
• /
• 1993

This study was designed to recognize the factors which can affect the normal eruption of the lower third molar and the eruption rate of the lower third molar in the cases of non-extraction and the extraction of first premolar. The sample consisted of 214 cases of extraction of first premolar and 119 cases of non-extraction, and all of these cases were divided into erupted and impacted lower third molar groups and were analized according to the pantomogram. The results of the study were as follows : 1. The eruption rate of the touter third molar was $54.67\%$ in the group of extraction of the first premolar and $35.29\%$ in the non-extraction group. 2. The early inclination of the erupting lower third molar has significant effect in the eruption of it. 3. In the orthodontic treatment, the extraction of first premolar is one of the factors infuencing the nomal eruption of lower third molar. 4. The available space for the normal enruption of lower third molar was greater in first premolar extraction case than in non-extraction case.