title: [Fracture resistance of teeth restored with one-piece computer aided design and manufacture zirconia posts and cores: an in vitro study].
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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Prosthodontics,Peking University School and Hospital of Stomatology, Beijing 100081,China; First Clinical Division,PekingUnivesity School and Hospital of Stomatology, Beijing 100034,China.
authors.forename: Tuan-feng
authors.initials: TF
authors.lastname: Zhou
authors.affiliation: Second Clinical Division,Peking University School and Hospital of Stomatology,Beijing 100101,China.
authors.forename: Xiang-fao
authors.initials: XF
authors.lastname: Zhang
authors.affiliation: Department of Prosthodontics,Peking University School and Hospital of Stomatology, Beijing 100081,China.
authors.forename: Xin-zhi
authors.initials: XZ
authors.lastname: Wang
mesh_terms: D002516:Ceramics; D017076:Computer-Aided Design; D003799:Dental Stress Analysis; D006801:Humans; D066298:In Vitro Techniques; D007180:Incisor; D011176:Post and Core Technique; D014082:Tooth Fractures; D019553:Tooth, Nonvital; D015040:Zirconium
chemical_list: D015040:Zirconium; C028541:zirconium oxide