title: Comparison of the fracture strengths of metal-ceramic crowns and three ceromer crowns.
abstract: BACKGROUND
  The fracture strength of a number of new ceromer systems for the fabrication of anterior fixed partial dentures is unknown.
  
  
  OBJECTIVE
  The purpose of this study was to compare the fracture strengths of metal-ceramic crowns and 3 types of ceromer crowns in a simulated anterior tooth preparation.
  
  
  METHODS
  A resin maxillary central incisor analog was prepared with a 5-degree convergence angle and a 90-degree, 1-mm shoulder. The incisal edge was reduced by 2 mm, and the axiogingival and axioincisal line angles were rounded. A mold of this tooth was made with vinyl polysiloxane impression material. Ten wax patterns were made from the mold and cast in a nickel-chromium alloy for the fabrication of metal dies, from which 10 metal-ceramic crowns were fabricated. Ten crowns for each of 3 ceromer systems (Artglass, Sculpture, and Targis) were fabricated from the same metal die. Each crown group was prepared, polymerized, air-particle abraded, and finished in accordance with the specific manufacturer's instructions. All 4 types of finished crowns were luted to the dies and embedded in polymethyl methacrylate resin blocks. Their fracture resistance was tested in a universal testing machine. The load was directed at the incisolingual line angle, at 130 degrees to the long axis of each specimen, until catastrophic failure occurred. A 7-mm-diameter rod was used to load the artificial crowns, with the center of the rod in contact with the crown surfaces. Analysis of variance and Tukey's multiple comparisons test (P<.05) were applied to the data.
  
  
  RESULTS
  Metal-ceramic crowns fractured at significantly higher values than ceromer crowns (1317 vs 602 N, respectively) (P<.05). No significant difference was found among the fracture values of Artglass, Sculpture, and Targis crowns.
  
  
  CONCLUSIONS
  Within the limitations of this study, failure load values for the 3 ceromer crowns tested, although significantly lower than the values for metal-ceramic crowns, still exceeded normal occlusal forces.
authors.affiliation: Department of Prosthodontics, College of Dentistry, Chonnam National University, Kwangju, Korea.
authors.forename: Chul-Whoi
authors.initials: CW
authors.lastname: Ku
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Park
authors.forename: Hong-So
authors.initials: HS
authors.lastname: Yang
mesh_terms: D000704:Analysis of Variance; D001732:Bite Force; D002516:Ceramics; D003188:Composite Resins; D003442:Crowns; D003735:Dental Casting Technique; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003830:Denture, Partial, Fixed; D006801:Humans; D007180:Incisor; D008422:Materials Testing; D008437:Maxilla; D016876:Metal Ceramic Alloys; D033081:Shear Strength; D018709:Statistics, Nonparametric; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D016876:Metal Ceramic Alloys; C111841:ceromer; D003776:Dental Porcelain