Effects of dentine bonding on mechanical strength of all ceramic restorative materials

ABSTRACTEffects of Dentin Bonding on Mechanical Strength of All Ceramic RestorativeMaterialsThe aim of this study was to evaluate the basic damage modes of differentceramic systems bonded to dentin under Hertzian indentation with the support ofstress distribution analysis.A single-cycle Hertzian contact test over a load range of 100-600 N wasapplied randomly to ceramic-dentin bilayer disc specimens of feldspathic ceramicwith 1mm, 1,5mm and 2mm thickness. A single-cycle Hertzian contact test over aload range of 200-850 N was applied to ceramic-dentin bilayer disc specimens ofof Zirconia or IPS Empress 2 with 1mm, 1,5mm thickness. Optical microscopywas employed for the identification of quasiplastic mode and radial cracks. Finiteelement analysis was also used to analyze the stress distribution under suchHertzian indentation.Owing to the microstructure of the material, the degree of damage in bothmodes evolved progressively and the origin of damage mode changed with contactload. Radial cracks were the first cracks for feldspathic porcelain with 1mmthickness at 150 N contact load, IPS Empress 2 with 1mm at 450 N and 1,5mm at700 N, and Zirconia with 1,5mm at 850 N. However, for feldspathic porcelain with1,5mm and 2mm thickness a quasiplastic mode occurred. The location and thevalue of maximum principle stresses seen in the models were consistent with themechanical test results.Microstructure and the thickness of the material have a significant effect onthe damage modes of ceramic layer systems. Dentin luting with resin cement,increases the mechsnicsl strength of all ceramic materials.Key words: Hertzian contact test, all ceramics, resin cement, dentinxiii