Abstract: Abstract： Objective To compare the fatigue resistance of residual crowns of molars restored with two post and core materials. Methods 20 residual crowns of first mandibular molars were collected, divided into two groups randomly and restored with fiber post-and-core crowns and cast metal latch type fission post-and-core crowns. The fatigue resistance test was implemented, and the values of fatigue resistance and modes of fracture were recorded and compared. Results Residual crowns of molars restored with cast metal latch type fission post-and-core crowns could obtain good fatigue resistance compared with the group restored with fiber post-and-core crown, and the difference had statistical significance (P﹤0.05). Conclusions Restoration of molar residual crowns with cast metal latch type fission post-and-core crown can get better mechanical properties than restoration with fiber post-and-core crown. For patients with habits of sleep bruxism together with tooth clinching, methods like decreasing cusp inclination should be adopted to reduce the vertical and lateral occlusal force.