title: In vitro fracture force and marginal adaptation of ceramic crowns fixed on natural and artificial teeth.
abstract: OBJECTIVE
  Artificial teeth made of acrylic resin or alloy are considered substitutes for rare caries-free human teeth in in vitro examinations. The purpose of this study was to compare the fracture strength and marginal adaptation of all-ceramic single crowns fixed to natural teeth with crowns fixed to artificial teeth after artificial aging.
  
  
  METHODS
  The fracture force and marginal adaptation were investigated in 28 adhesively luted all-ceramic crowns on human molars of different sizes, as well as on alloy and liquid crystal polymer (LCP) artificial teeth. The fracture force was determined using a universal testing machine, and the semiquantitative marginal adaptation was examined using a scanning electron microscope, in both instances after simulating 5 years of clinical service.
  
  
  RESULTS
  Fracture force was found to be significantly higher for crowns fixed on substitute materials (alloy = 1,838 N; LCP = 1,392 N) than for crowns on human teeth (888 N). No significant differences in marginal quality could be determined between the groups. All crowns showed marginal gaps of about 10% and perfect margins at about 90%.
  
  
  CONCLUSIONS
  The high in vitro fracture values of all-ceramic crowns on artificial materials may lead to a misinterpretation of the tested restorative materials, overvaluing the material properties in a first preclinical estimation. Human teeth or materials with a comparable modulus of elasticity are therefore preferred in in vitro fracture tests.
authors.affiliation: Department of Prosthetic Dentistry, University Clinics, Regensburg, Germany. martin.rosentritt@klinik.uni-regensburg.de
authors.forename: M
authors.initials: M
authors.lastname: Rosentritt
authors.forename: T
authors.initials: T
authors.lastname: Plein
authors.forename: C
authors.initials: C
authors.lastname: Kolbeck
authors.forename: M
authors.initials: M
authors.lastname: Behr
authors.forename: G
authors.initials: G
authors.lastname: Handel
mesh_terms: D000704:Analysis of Variance; D002858:Chromium Alloys / Q000737:chemistry; D003442:Crowns; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D004548:Elasticity; D006801:Humans; D008422:Materials Testing; D008963:Molar; D011108:Polymers / Q000737:chemistry; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013997:Time Factors; D014093:Tooth, Artificial
chemical_list: D002858:Chromium Alloys; D011108:Polymers; C422409:liquid crystal polymer; D003776:Dental Porcelain