title: In vitro fracture resistance of copy-milled zirconia ceramic posts.
abstract: BACKGROUND
  Current copy-milling systems allow for the fabrication of 1-piece zirconia ceramic posts and cores, which can be used in combination with ceramic crowns to restore endodontically treated teeth in an esthetic manner. However, limited data are available on the fracture resistance of copy-milled zirconia ceramic posts.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to compare the fracture resistance of prefabricated posts made from zirconia ceramic and fiber-reinforced composite resin with the fracture resistance of copy-milled zirconia ceramic posts.
  
  
  METHODS
  Three groups of posts and cores were fabricated (n=10): prefabricated zirconia ceramic posts with composite resin cores (ZIR), fiber-reinforced composite resin posts with composite resin cores (FRC), and copy-milled zirconia ceramic posts and cores (CM). Following artificial aging by thermal cycling and masticatory simulation, compressive tests were performed in a universal testing machine with the posts mounted at an angle of 135 degrees to the long axis of the posts. The maximum forces needed to fracture the posts were recorded for statistical analysis (1-way ANOVA, Tukey's Honestly Significant Difference test; alpha=.05).
  
  
  RESULTS
  The mean maximum forces (SD) needed to fracture the posts and cores were 123.10 (19.38) N for FRC, 139.30 (42.70) N for CM, and 267.10 (59.11) N for ZIR. The prefabricated zirconia ceramic posts required significantly higher fracture loads as compared to FRC (P<.001) and CM (P<.001).
  
  
  CONCLUSIONS
  The fracture load of copy-milled zirconia ceramic posts is significantly lower than that of prefabricated zirconia ceramic posts of the same size.
authors.affiliation: University of Erlangen-Nuremberg, 91054 Erlangen, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Beck
authors.forename: Friedrich
authors.initials: F
authors.lastname: Graef
authors.forename: Manfred
authors.initials: M
authors.lastname: Wichmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Karl
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry; D019245:Compressive Strength; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D005898:Glass / Q000737:chemistry; D008422:Materials Testing; D011176:Post and Core Technique / Q000295:instrumentation*; D018709:Statistics, Nonparametric; D015040:Zirconium / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C009753:fiberglass; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide