title: Fracture resistance of endodontically treated teeth without ferrule using a novel H-shaped short post.
abstract: OBJECTIVE
  To evaluate the fracture resistance and failure types of modified H-designed intradental short retention preparation for computer-aided design/computer-assisted manufacture (CAD/CAM) restorations, in cases where no ferrule is possible.
  
  
  METHODS
  A combined finite element analysis and in vitro testing was employed. Forty extracted single-rooted premolars were selected and prepared for the following four groups (n = 10 per group): Group A, H-post preparation restored with glass-ceramic crowns; group B, H-post preparation restored with lithium disilicate crowns; group C, endocrowns (negative control group); and group D, 2-mm ferrule preparation and restoration with fiber posts (positive control). After cementation, specimens were loaded to fracture (1 mm/min) in a universal testing machine. The data were analyzed using Kolmogorov-Smirnov, Shapiro-Wilk test, one-way ANOVA, followed by post-hoc Scheffé test and chisquare test.
  
  
  RESULTS
  The H-post group restored with lithium disilicate crowns (group B) presented higher fracture resistance compared to the H-post group with glass-ceramic crowns (group A) and the endocrowns (group C). Among the failure analysis, only specimens of group C were all repairable after fracture load test, while the specimens of remaining groups A, B, and D accounted for 90%, 70%, and 50% repairable fracture modes, respectively.
  
  
  CONCLUSIONS
  The modification of the short intracoronal restoration anchorage profile may be a valid concept to improve the retention and fracture resistance, given that the materials are adjusted for this purpose in terms of mechanical resistance and internal adaptation. Numerical evaluations and future in vitro studies may help to select the best designs and materials.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Schmidlin
authors.forename: Bogna
authors.initials: B
authors.lastname: Stawarczyk
authors.forename: Danielle
authors.initials: D
authors.lastname: DeAbreu
authors.forename: Andreas
authors.initials: A
authors.lastname: Bindl
authors.forename: Andreas
authors.initials: A
authors.lastname: Ender
authors.forename: Ionut P
authors.initials: IP
authors.lastname: Ichim
mesh_terms: D001641:Bicuspid; D002516:Ceramics; D017076:Computer-Aided Design; D003442:Crowns; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods*; D020342:Finite Element Analysis; D066298:In Vitro Techniques; D011176:Post and Core Technique; D012390:Root Canal Therapy; D014082:Tooth Fractures; D019553:Tooth, Nonvital / Q000000981:diagnostic imaging / Q000601:surgery; D055114:X-Ray Microtomography
chemical_list: C493120:lithia disilicate; D003776:Dental Porcelain; C023506:Glass ceramics