IMPROVEMENT OF BONDING BETWEEN VENEERING PORCELAIN AND ZIRCONIA SUBSTRATE WITH GLASS-CERAMIC INTERLAYER

Lithium disilicate glass-ceramic was introduced as interlayer between zirconia substructure and veneering porcelain. To simulate dental practice which involved multiple firings, the experimental samples of porcelain veneer were prepared following the veneering procedure recommended by suppliers of zirconia system and to assess the performance, mean shear bond strengths (SBS) of porcelain veneers consisted of lithium disilicate glass-ceramic and commercial glass-ceramic liners were determined in comparison. The obtained mechanical results of SBS, Vickers hardness and fracture toughness at the bonding interface are discussed in relation to physical properties, i.e. morphologies and crystal phases of the fired porcelain veneers including fracture surfaces respectively investigated by SEM, EDX, XRD and stereomicroscope. Moreover, biocompatibility and thermocycling tests were also performed on the selected specimens to assure clinical viability. It is found that the SBSs of porcelain veneers consisted of lithium disilicate glass-ceramic of which were fired at optimal conditions are significantly higher than those of porcelain veneers consisted of the current commercial leucite glass-ceramic liners and without glass-ceramic liner. In addition to good mechanical properties, biocompatibility, durability and the better CTE stability over that of leucite glass-ceramic, lithium disilicate glass-ceramic has been proved to be a potent glass-ceramic liner for porcelain veneer.