Abstract: Objective：To compare the fracture resistance of endodontically-treated teeth restored with prefabricated zirconia posts or one-piece computer aided design and computer aided manufacture (CAD/CAM) zirconia posts and cores, and unrestored endodontically-treated teeth. Methods: Recently extracted human maxillary central incisors (n=36) were endodontically treated and divided into three groups (n=12 each): group 1 was restored with prefabricated zirconia posts (Comospost) and hot pressed ceramic cores; group 2 restored with one-piece CAD/CAM zirconia posts and cores; group 3 not restored. The teeth were fixed in a universal load-testing machine; a compressive load was applied at 135 degrees to the long axis of each tooth at a crosshead speed of 1 mm/min until fracture. One-way analysis of variance (Student-Newman-Keuls) was used to determine the significance of the differences in failure load between the groups.Results: The mean fracture loads were (311.75 ± 70.12) N, (423.83 ± 54.58) N and (736.33 ± 82.91) N, respectively. The unrestored teeth exhibited significantly higher fracture resistance than the two groups of restored teeth. The teeth restored with one-piece CAD/CAM zirconia posts and cores had higher fracture resistance than the teeth restored with prefabricated zirconia posts and hot pressed ceramic cores (P < 0.001). Conclusion: Within the limitations of this study, the root canal-treated teeth restored with one-piece CAD/CAM zirconia posts and cores had a significantly higher failure resistance than the teeth restored with prefabricated zirconia posts. One-piece CAD/CAM zirconia posts and cores can offer some advantages for esthetic prosthodontics.

Key words: Computer-aided design, Zirconium oxide, Dental stress analysis, Post and core technique, In vitro