离体上颌第二磨牙髓室底形态特点及根管口的定位研究

目的观察上颌第二磨牙的髓底形态特点及根管定位。方法51颗离体的上颌第二磨牙，其中5颗牙齿拍常规的烦舌向x线片，牙齿均用金刚钻在喷水下依釉牙骨质界横断牙冠（cememo—enamel junction，简称CEJ），取根侧部分为实验样品，用放大镜观察髓室底的解剖形态和根管口的位置。髓室底沟分5型。结果根管口总是位于髓室壁和髓室的交汇处，或位于牙根发育融合线的顶点。髓室底沟呈“Y”型的牙齿28颗（占55％．28／51），呈“7”形的牙齿11颗（22％），上述根管口均与牙根发育融合线相接，远中烦舌沟的牙齿5颗（10％），近中烦舌沟的牙齿1颗（2％），2个根管口的牙齿6颗（12％）。结论由于x线片上有时很难准确显示上颌第二磨牙牙根的形态，修复性牙本质或矿化常闭塞根管口，应该仔细地进行x线片阅读和临床探查，防止根管遗漏。

Anatomical features of the pulp-chamber floor in maxillary second molars

Objective To investigate the anatomical features of the pulp-chamber floor in maxillary second molars.Methods Fifty-one extracted maxillary second molars were investigated, and the roots of 5 teeth were visualized on radiographs taken in the buccolingual direction. Then all the teeth had their crowns cut off transversely at the level of the cemento-enamel junction, so that the outline of the pulp chamber and the number and positoin of orifices on pulp-chamber floors could be observed.Results All the radiographs of 5 teeth showed anomalous appearance of only two roots. The orifices of the root canals were always located at the junction of the walls and floor, or may lay at the terminus of developmental root fusion lines. All maxillary second molars in this study had three roots, the developmental root fusion lines of 28 teeth appeared as type "Y"(55%,28/51),the lines of 11 teeth showed type "7"(22%,11/51). The lines above connected the three orifices of teeth, the lines of 5 teeth (10%,5/51) connected the orifices of the palatal and distobuccal, the lines of only 1 tooth(2%,1/51) connected the orifices of the palatal and mesiobuccal, 6 teeth had anomalous appearance of only two orifices and the lines connected the orifices of the palatal and buccal.Conclusion Unusual images of maxillary second molars might be observed by viewing radiographs, reparative dentin or calcifications often obscure orifices, carefully radiographic and clinical examinations were emphasized to avoid misinterpretations.