Abstract: Objective： To evaluate the effect of computer aided design and computer aided manufacture (CAD/CAM) one-piece zirconia posts and cores for the restoration of defective teeth.  Methods: In the study,72 defective teeth of 47 patients who had proper root canal therapy were restored with CAD/CAM onepiece zirconia posts and cores. All the ceramic crowns were finally used to restore contour and function of the teeth. The defective teeth were divided into two groups on the basis of the teeth defect degree. Group A: 39 defective teeth presented with three or four coronal residual walls, and group B: 33 defective teeth presented with less than two coronal residual walls. During the clinical observation period, the stability, dislocation of posts and the occurrence of fractures in either teeth or posts and cores were assessed and analyzed with a paired t test（α=0.05）. Meanwhile shade matching was conducted between the restored teeth and normal reference teeth, the marginal fitness of the restored teeth were recorded according to the standard of United States Public Health Service (USPHS) and analyzed with descriptive statistics.  Results: The average follow up was (65.0±4.8) months. During the observation period, the restorations were examined both clinically and with periapical radiograph. No incidence of teeth fracture or posts and cores complications were observed in both groups, and all CAD/CAM onepiece zirconia posts and cores remained intact with restored teeth. There were no post and core dislodgement or fracture. There was no difference between group A and group B (P>0.05). The restorative effect of CAD/CAM onepiece zirconia posts and cores with all the ceramic crowns were assessed according to the standard of USPHS, and the number of the restored tooth shade matching with level A was 67, and 5 with level B. The rate of shade matching was 93.06%. As the marginal fitness, 64 restored teeth were level A, and 8 with level B. The rate of restorative teeth marginal fitness was 88.89%.Conclusion: CAD/CAM one-piece zirconia posts and cores were successfully used to restore defective teeth and received excellent clinical effect. So, it can be a good choice for defective teeth which need postcores and crowns restoration.

Key words: Ceramic material, Computer aided design and computer aided manufacture, Zirconia, Post and core