Objective To compare the different restorations of endodontically treated premolars, and to choose the best method. Methods 10 pairs of symmetry maxillary first premolars were collected from 10 patients，and randomly divided into 2 groups. Every pair received different treatment accordingly. The test group was set up the medial－occlusal cavities model under the same standard. The 10 pairs teeth were test by instron 4302 universal test machine in speed of 1.00 mm/min until broken up and the top load was recorded. The load angle was 45 degree to the long axis of the teeth, as the load was pointed to the middle of the lingual surface on the buccal cusp. The records were analyzed by paired samples t test. Results Based on the medial-occlusal cavities, the fracture strength of the full crowned teeth was lower than the full natural teeth，and the fracture strength of the post-crowned teeth was higher than the full natural teeth. Conclusion From the point of biomechanics, the different trauma of the endodontically treated teeth fits to different restorations. The medial-occlusion cavities fit the post-crown restoration mostly.
