Effect of firings on the lithium disilicate and zirconia-reinforced lithium silicate dental ceramics for CAD-CAM procedures

PurposeThe aim of this study was to verify the effect of multiple firing cycles on lithium disilicate and zirconia reinforced lithium silicate ceramics.Materials and MethodsSixty discs measuring 12 mm x 1.2 mm made with IPS E.max CAD (n=30) or Vita Suprinity (n=30) ceramic systems were divided into 3 subgroups submitted to 2, 3 or 5 firing cycles (C2, C3, and C5, respectively). Surface roughness, gloss, biaxial flexural strength, and Vickers hardness were evaluated, as well as scanning electron microscopy (SEM) analysis. Data was submitted to two-way ANOVA and Tukey’s test with a 5% significance level.ResultsFor surface roughness, Suprinity showed a significant decrease at C5 (p<0.05). For gloss, there was no statistical interaction and C5 showed higher gloss value for both ceramics (p>0.05). For flexural strength, Suprinity showed significant increase (p<0.05) and IPS E.max CAD decreased significantly at C5 (p<0.05). For Vickers hardness, there was no statistical interaction and hardness decreased at C5 for both ceramics (p>0.05). IPS E.max CAD showed no morphological difference while Suprinity showed micro irregularities for C5 in the SEM analysis.ConclusionFiring cycles promoted better effect on roughness and biaxial flexural strength parameters for the Suprinity compared with IPS E.max CAD. Both ceramics showed negative effects on the morphological aspect of the crystalline matrix and similar gloss or hardness values.