上颌第一恒磨牙萌出早，且承担着主要的咀嚼功能，其龋病发生率仅次于下颌第一、二恒磨牙［１］，常需作牙髓治疗。而上颌第一恒磨牙根管系统较为复杂，尤其是近中颊根，近年国内外对其双管发生率的报道相差甚大：Ｈｏｗａｒｄ等的临床研究为７１２％［２］；张萃贤等的... The maxillary first permanent molar eruption early, and bear the main chewing function, the incidence of caries second only to the mandibular first and second permanent molars [1], often required for endodontic treatment. The root canal system of the maxillary first permanent molars is more complicated, especially the mesiobuccal root. In recent years, there is a big difference between the reports of its double-tube incidence in both home and abroad: the clinical research by Howard et al. Is 71.2% [2]; Zhang Cuixian Wait ...