title: [Fatigue and fracture resistance of the flared roots restored with computer aided design and computer aided manufacturing glass fiber posts].
abstract: OBJECTIVE
  To evaluate the fatigue and fracture resistance of the flared roots restored with computer aided design (CAD) and computer aided  manufacturing (CAM) glass fiber posts.
  
  
  METHODS
  In the study, 32 maxillary central incisors with roots longer than 13 mm were selected and their canals  were flared, and the roots were allocated into 4 groups (n=8) by a random number chart: CAD/CAM glass fiber posts, prefabricated quartz fiber posts, cast  gold alloy posts, and CAD/CAM zirconia posts. The posts were luted to the roots by resin cement and fabricate zirconia crown for every specimen. An  addition-type silicone impression material was used to simulate the periodontal ligament. All the specimens were submitted to 1.2×10(6) cycles loaded with  a 49 N force, at 45 degree to the long axis of the teeth simultaneously with 3 000 thermal cycles (5 °C-50 °C-5 °C). After that, the specimens were subjected to  a load at a crosshead speed of 1 mm/min in a servo-hydraulic testing machine applied at 45 degree to the long axis of the tooth until fracture. The data  were subjected to ANOVA test and the patterns of the failure were examined.
  
  
  RESULTS
  After the cycling loading, 4 crowns from prefabricated quartz fiber  posts groups were deboned, and  no other failure was found after the cycling loading; the fracture strengths of CAD/CAM glass fiber posts group [(441.5± 103.2) N] and cast gold alloy posts group [(462.9±170.0) N] were  higher (F=4.613, P<0.05) than those of CAD/CAM zirconia posts group [(284.1±99.0)  N] and prefabricated quartz fiber posts group [(315.4±112.3) N]; the entire specimens presented unfavorable failures.
  
  
  CONCLUSIONS
  Although further in  vitro and in vivo studies are necessary, the results of this study show that the use of CAD/CAM glass fiber posts and cast gold alloy posts may achieve  better outcomes in flared roots than that of CAD/CAM zirconia posts and prefabricated quartz fiber posts.
authors: Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing,China.
authors: Zhi
authors: Z
authors: Li
authors: Xin-zhi
authors: XZ
authors: Wang
authors: Cheng-zhi
authors: CZ
authors: Gao
authors: Krejci
authors: K
authors: Ivo
mesh_terms: D017076:Computer-Aided Design; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D005898:Glass / Q000737:chemistry*; D006801:Humans; D007180:Incisor / Q000473:pathology; D011176:Post and Core Technique / Q000295:instrumentation*; D012390:Root Canal Therapy / Q000379:methods*; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000517:prevention & control*
chemical_list: D003764:Dental Materials; C009753:fiberglass