Influence of veneering porcelain thickness and cooling rate on residual stresses in zirconia molar crowns

AbstractObjective m of this study was to investigate the influence of increasing veneering porcelain thickness in clinically representative zirconia molar crowns on the residual stresses under fast and slow cooling protocols. s neered zirconia copings (Procera, Nobel Biocare AB, Gothenburg, Sweden) based on a mandibular molar form, were divided into 3 groups with flattened cusp heights that were 1 mm, 2 mm, or 3 mm. Half the samples were fast cooled during final glazing; the other half were slow cooled. Vickers indentation technique was used to determine surface residual stresses. Normality distribution within each sample was done using Kolmogorov–Smirnov & Shapiro–Wilk tests, and one-way ANOVA tests used to test for significance between various cusp heights within each group. Independent t-tests used to evaluate significance between each cusp height group with regards to cooling. s ssive stresses were recorded with fast cooling, while tensile stresses with slow cooling. The highest residual compressive stresses were recorded on the fast cooled 1 mm cusps which was significantly higher than the 2 and 3 mm fast cooled crowns (P < 0.05). There was a significant linear trend for residual stress to decrease as veneering porcelain thickness increased in the fast cooled group (P < 0.05). No significant differences were found between the various cusp heights during slow cooling (P ≥ 0.05). icance g rate and geometric influences in a crown anatomy have substantially different effects on residual stress profiles with increasing veneering porcelain thickness compared to the basic flat plate model.