Changes in Optical Characteristics and Surface Topography of CAD/CAM Materials after Bleaching Applications: An AFM Evaluation

Abstract

Purpose: To evaluate the effect of in-office and at-home bleaching agents on color changes (ΔE₀₀ ), translucency (TP₀₀ ), whiteness (WI_D ), surface roughness (R_a ), and surface topography (R_sk and R_ku ) of a resin nano-ceramic and a polymer-infiltrated ceramic network CAD/CAM material.

Materials and methods: Sixty specimens (6 mm × 7 mm × 1.3 mm) were prepared from Lava Ultimate (LU) and Vita Enamic (VE). The specimens were divided into 6 groups according to the bleaching agents applied (n = 10/group): control, Perfect Bleach Office + (PBO), Opalescence Boost (OB), Perfect Bleach (PB) with 10% and 16% carbamide peroxide and Whiteness Perfect (WP). ΔE₀₀ values were calculated before and after bleaching procedures with a spectrophotometer using the CIEDE2000 formula. ΔTP₀₀ and ΔWI_D values were calculated for each material. R_a , R_sk , and R_ku values of the specimens were evaluated with an Atomic Force Microscope. Two-way ANOVA was used for statistical analyses of the parameters measured after bleaching. For pairwise comparisons, Tukey test was performed.

Results: For LU, no statistically significant difference among the ΔE₀₀ values of the groups was observed (p = 1.000). For VE, only WP group presented significantly higher values (2.12 ± 2.66) than the other groups (p < 0.001). For both materials; ΔTP₀₀ values of at-home bleaching groups were significantly higher than in-office bleaching groups and control group (p < 0.001). For VE, ΔWI_D values did not demonstrate statistically significant difference (p = 1.000); however, for LU, PBO applied group showed statistically higher ΔWI_D values (3.00 ± 2.38) (p = 0.010) and WP applied group showed lower ΔWI_D values (0.47 ± 0.31) than the other groups (p = 0.030). For both LU and VE, there was no statistically significant difference among the groups regarding Ra (F = 4.544), R_sk (F = 2.369), and R_ku values (F = 2.391) (p = 1.000). All of the VE groups presented R_a values higher than 0.2 µm.

Conclusions: The optical properties of LU and VE after bleaching applications were affected by the contact time with bleaching agents rather than concentration. Bleaching procedure had no effect on the surface properties of these materials.

Keywords: Vita enamic; atomic force microscopy; bleaching agents; ceramics; color; color perception; composite resins; computer-aided design; surface properties.