本文目的是比较离体牙的根管台阶法预备和台阶法预备加上超声波预备1或3分钟的清洁效果。取400颗离体成人下颌第一、第二磨牙贮于-7℃以备用。在颊侧位X线片测定近中根管弯曲度(要求15°～45°)。本实验仅用Ⅲ型根管形态的近中根管,随机将实验牙分为3组,每组20颗,将另20颗牙不用器械预备作为 The purpose of this article is to compare the root canal preparation of ex vivo teeth and bench preparation plus ultrasonic preparation for 1 or 3 minutes of cleaning. Take 400 adult mandibular first, second molar stored at -7 ℃ for use. In the buccal position X-ray determination of proximal root canal curvature (requires 15 ° ~ 45 °). This experiment only with type Ⅲ root canal in the proximal canal, the experimental teeth were randomly divided into three groups of 20, the other 20 teeth without equipment preparation as