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Bibiana Vogel Peres Riesgo1, Luiza Ribeiro2, Pablo Machado Soares1
1MSciD and PhD Post-Graduate Program in Oral Science, Faculty of Dentistry, Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul State, Brazil.
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This study evaluated the effect of glaze application protocols on surface roughness, translucency, and fatigue behavior of a lithium disilicate-based ceramic (CEREC Tessera, Dentsply, Germany). Discs (A2 HT shade; Ø = 10 mm; thickness = 1 mm) were fabricated and randomly assigned to three groups (n = 7 for roughness and translucency; n = 12 for fatigue): CTRL (crystallization only), CCG (combined crystallization/glaze firing), and C+G (crystallization followed by additional glaze firing). Surface roughness (Ra, Rz) was measured using a contact profilometer, and translucency (TP00) was calculated from CIEDE2000 color coordinates. The ΔTP between groups was also determined. Specimens were cemented to glass fiber reinforced epoxy resin discs and subjected to cyclic fatigue testing under water immersion until failure. One-way ANOVA and Tukey's post-hoc tests were used for roughness and translucency, and Kaplan-Meier with Mantel-Cox for fatigue. One fractured specimen per group was examined by SEM to assess crack initiation and propagation. Glazing increased surface roughness, as CCG and C+G showed higher Ra and Rz values compared to CTRL (p > 0.05). TP00 ranged from 27.12 (C+G) to 28.33 (CCG), with no significant differences. ΔTP values (0.30 for CCG, 0.91 for C+G) were below the perceptibility threshold. Fatigue performance differed among groups (p < 0.05), with C+G showing higher mean cycles to failure compared to CTRL and CCG, although fatigue failure load did not differ significantly. SEM analysis revealed fractures initiating at the cementation surface under tensile stress and propagating toward the occlusal surface.