THE STUDY OF THE ERUPTION PATTERN OF THE MANDIBULAR PREMOLARS

하악(下顎) 소구치(小臼齒) 맹출양장(萌出樣狀)에 관(關)한 연구(硏究)

The author observed the eruption pattern of the mandibular premolars. For this study the author took 406 cases of oblique cephalographs of 6 to 12 year old children. The measurement were with regard to the vertical and horizontal dimensional changes and tooth axis changes to the occlusal plane. The following results were obtained. 1. At stage V the tooth axis of 1st premolar inclined mesially to the occlusal plane, as the tooth erupt toward vertically the angulation changed that at stage X the tooth axis almost right angle to the occlusal plane. 2. The distance from the root apex of premolars to the lower border of mandible were slightly increased to the stage VII, while after stage VII rapid increasing appeared. At stage X the distance of 1st premolar was more longer than 2nd premolar. 3. The distance from the mesial surface of 1st molar to the mesial surface of premolars were decreased slightly to the stage VII, but this distances were decreased rapidly after stage VII. 4. The distance between distal surface of 1st premolar and mesial surface of 2nd premolar was almost constant before stage VIII, at stage IX this distance was little presented because the premolars were contacted.