Objective To study the shape and location of rootcanalorifice in maxillary first permanent molar and provide a morphological basis for locating canal orifice in endodontic therapy.
目的研究上颌第一磨牙根管口形态和位置关系，为根管治疗时寻找根管口提供解剖学依据。
2
Objective:To introduce a new prefabricated post-and -core system, a helical drilling bit and a prefabricated post-and -core consisting of a rootcanalorifice bur which was designed by the author.