title: Crack initiation modes in bilayered alumina/porcelain disks as a function of core/veneer thickness ratio and supporting substrate stiffness.
abstract: We hypothesize that the fracture resistance of alumina core/porcelain veneer disks increases and that crack initiation shifts from veneer to core as the core/veneer thickness ratio (t(C)/t(V)) increases from 0.5/1.0 to 1.3/0.2, or as the elastic modulus of the supporting substrate (E(S)) to which it is resin-bonded increases from 5.1 to 226 GPa. When supported by a low-modulus substrate, disks with low t(C)/t(V) ratios exhibited cracks in the veneer and within the core, while those with high t(C)/t(V) ratios demonstrated core cracks, but not veneer cracks. None of the disks supported by Ni-Cr alloy (E = 226 GPa) exhibited core cracks. These results support the hypothesis that the crack initiation site shifts as the t(C)/t(V) ratio increases, but the increase in E(S) did not affect the crack initiation site. This study suggests that the t(C)/t(V) ratio is the dominant factor that controls the failure initiation site in bilayered ceramic disks.
authors.affiliation: First Department of Prosthodontics, Faculty of Dentistry, Tokyo Medical and Dental University, Japan. n.waka.pro1@dent.tmd.ac.jp
authors.forename: N
authors.initials: N
authors.lastname: Wakabayashi
authors.forename: K J
authors.initials: KJ
authors.lastname: Anusavice
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D000704:Analysis of Variance; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D003776:Dental Porcelain / Q000737:chemistry*; D003801:Dental Veneers; D004548:Elasticity; D004853:Epoxy Resins / Q000737:chemistry; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D011176:Post and Core Technique; D017655:Silicon Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: C105314:AllCeram; D017554:Carbon Compounds, Inorganic; D002858:Chromium Alloys; D003722:Dental Alloys; D004853:Epoxy Resins; D017655:Silicon Compounds; D003776:Dental Porcelain; C036884:Rexillium III; D000537:Aluminum Oxide; C022088:silicon carbide