title: Influence of relative layer height and testing method on the failure mode and origin in a bilayered dental ceramic composite.
abstract: OBJECTIVE
  The purpose of this study was to examine the influence of testing method (uniaxial and biaxial) and relative layer heights on the failure origin and failure mode of bilayered ceramic composite beams and disks composed of In-Ceram and Vitadur Alpha porcelain.
  
  
  METHODS
  Beams and disks were fabricated, with relative layer heights of 1:2, 1:1, and 2:1, respectively, for In-Ceram and Vitadur Alpha porcelain. Ninety specimens each (thirty 1:2, thirty 1:1, and thirty 2:1) were tested in 3-point, 4-point-1/4-point, and biaxial ring-on-ring testing apparatuses. Fractography was used to categorize failure origins as either surface or interfacial, and failure modes as delamination or nondelamination.
  
  
  RESULTS
  Surface and interfacial failure origins were observed in 3-point and biaxial disk test specimens, but not 4-point-1/4-point specimens where only surface failures occurred. None of the "clinically similar" specimens (1:2) failed at the interface. All testing methods resulted in delamination of Vitadur Alpha from the In-Ceram, while only 3-point and biaxial disk testing methods resulted in crack propagation through the composite interface without delamination.
  
  
  CONCLUSIONS
  Varying relative layer heights or varying testing method in laminate composite tensile specimens can affect failure mode and failure origin.
authors.affiliation: Department of Dental Biomaterials, School of Dentistry, University of Alabama at Birmingham, 1919 7th Avenue South, Birmingham, AL 35294, USA. gthompson002@sprintmail.com
authors.forename: G A
authors.initials: GA
authors.lastname: Thompson
mesh_terms: D000268:Adhesiveness; D000465:Algorithms; D000537:Aluminum Oxide / Q000737:chemistry; D000704:Analysis of Variance; D002516:Ceramics / Q000737:chemistry*; D016009:Chi-Square Distribution; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: C111324:vitadur alpha omega; D003776:Dental Porcelain; C070870:In-Ceram; D000537:Aluminum Oxide