Comparative analysis of techniques for extrinsic characterization of CAD/CAM ceramics

Abstract

The present study aims to evaluate surface roughness and color stability of lithium disilicate and leucite ceramics after conventional and a novel surface finish techniques. Ceramic blocks (n = 84) of lithium disilicate and leucite were prepared and divided into 3 groups, being group 1: polished ceramic (negative control) (NC); group 2: stained (pigmented) ceramic followed by glaze (positive control) (PC) and group 3: simultaneous application of staining and glaze (experimental technique) (ET). Changes in luminosity and surface roughness were evaluated at 4 different time-points after a simulated brushing cycling test. Multivariate test results showed that there was a triple interaction effect between applied material, finish technique and time on their average roughness (p < 0.001) and luminosity (p < 0.05). There was no statistically significant difference in the mean roughness considering NC and ET groups for the leucite and lithium disilicate ceramics, but there was an increase in roughness mean at t1 for the PC and ET groups. Considering luminosity (materials vs. time), there was a statistically significant difference in leucite PC group. The NC and ET groups did not differ statistically from each other. There was a luminosity reduction in NC lithium disilicate ceramics for PC and NC groups. Also, analysis of color variation (ΔΕ) revealed significant differences for disilicate but not for the leucite groups. In leucite-based ceramic groups, surface roughness showed intermediate values between ET and the other groups at all times. Correlation analysis between roughness and luminosity presented significant results for leucite (r = 0.331; p < 0.001) and non-significant for lithium disilicate groups (r = 0.068; p > 0.05). Results suggested the possible application of the experimental technique (ET) for reduction of clinical time compared to conventional techniques, by the use of less ceramic firing cycles, with no prejudice in terms of surface roughness and luminosity over the studied time.