Effects of glazing methods on the optical and surface properties of silicate ceramics

Purpose: This study aims to evaluate the effect of different glazing methods on translucency parameter (TP), contrast ratio (CR), opalescence parameter (OP), surface roughness (Ra) and topography of the silicate ceramics. Methods: Seventy specimens (10 x 10 x 1 mm) were fabricated from lithium disilicate (IPS e.max CAD, abbreviated as E) and zirconia-reinforced lithium silicate (Vita Suprinity, abbreviated as VS) ceramics and divided into 7 subgroups (n = 10) according to the polishing and glazing procedures: (1) mechanical polishing before-crystallization (m-BC), (2) mechanical polishing after-crystallization (m-AC), (3) glaze powder/liquid after-crystallization (pl-AC), (4) glaze-paste before-crystallization (gp-BC), (5) glaze-paste after-crystallization (gp-AC), (6) glaze-spray before-crystallization (gs-BC), (7) glaze-spray aftercrystallization (gs-AC). Color and Ra measurements were performed. CIEL*a*b* and CIEXYZ parameters were recorded and TP, CR, and OP values were calculated. Data were analyzed using two-way ANOVA and Tukey HSD tests (alpha= 0.05). Results: In E groups, the highest Ra value was found in gs-AC (1.66 +/- 0.14 mu m) while the lowest value was found in pl-AC (0.68 +/- 0.08 mu m). In VS groups, the highest Ra value was found in gp-BC (1.64 +/- 0.25 mu m) while the lowest value was found in m-AC (0.77 +/- 0.06 mu m) (p <0.05). The mean TP value of E (17.62 +/- 0.73) was found to be higher than VS (15.37 +/- 1.16). The CR (0.72+0.030) and OP (12.06 +/- 0.74) values of VS were found higher than CR (0.57 +/- 0.02) and OP (6.72 +/- 0.40) values of E. Conclusions: Zirconia-reinforced silicate ceramics have higher opalescence and lower translucency values than lithium disilicate ceramics. Increase in surface roughness reduces translucency. Glaze powder/liquid after-crystallization is the most effective way to reduce surface roughness of lithium disilicate ceramics while that is mechanical polishing after-crystallization for zirconia-reinforced silicate ceramics. (C) 2019 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.