备洞、开髓腔等操作过程中尽可能保留健康的牙体组织对预防牙折有重要意义。现将保留边缘嵴的改良式开髓法和常规开髓法对牙髓治疗后牙齿抗折力的影响，比较如下。１材料与方法完整新鲜离体下颌磨牙４５颗，按大、中、小相同比例随机分为３组。Ⅰ组：二类洞改良开髓法。牙... Prepare the hole, open the marrow cavity and other operations as much as possible to retain healthy tooth tissue to prevent tooth decay is of great significance. The edge of the ridge will now retain the modified method of open pulp and conventional pulp medullary treatment of teeth after the impact of anti-friction, as follows. 1 Materials and Methods Complete fresh mandibular molar in vitro 45, according to the same proportion of large, medium and small were randomly divided into 3 groups. Group Ⅰ: improved second-class hole open pulp method. tooth...