关键词: 多生牙, 第四磨牙, 发病机制, 形态, 部位

Abstract: Objective To explore the clinical characteristics of the fourth molars. Method The panoramic radiographs of the patients from department of stomatology, Changsha Central Hospital, from June 30,2013 to June 30,2016, were reviewed. The patients who got supernumerary teeth at the distal of the third molar were selected, then their names, sexuality, age, attendance reason, the number of supernumerary teeth, their position, pattern and whether they were erupted, were recorded and analyzed. Result Twentytwo fourth molars in 21 cases were found, and the sexual ratio was 8∶13. Eight fourth molars of the twentytwo were at the left maxillary, eleven were at the right maxillary, three were at the left mandible and no one was at the right mandible. Five of them were erupted, and the rest were still impacted in the bone. By observing the pattern of tooth, ten teeth were conic, six were nodular, four were supplementary type and two of them were the fused teeth. The disparity between fourth molar at maxillary and mandible was remarkably divergent(P<0.01);the disparity whether the fourth molar was erupted or not was remarkably divergent (P<0.05). Conclusion The fourth molar at the maxillary is more common, and a majority of them are still embedded in the bone. We advocate the patients who have fourth molar which is embedded in the bone and dont have subjective symptoms should be observed closely.

Key words: supernumerary teeth, fourth molar, nosogenesis, pattern, position