Effect of simulated brushing and disinfection on the surface roughness and color stability of CAD-CAM denture base materials

Abstract

Purpose: To evaluate the effect of simulated brushing and chemical disinfection on the surface roughness and color stability of CAD-CAM denture base materials and to compare with those of a heat-cured denture base material.

Material and methods: Disk-shaped specimens (Ø 10mm × 2 mm) were prepared from 3 CAD-CAM denture base resins (AvaDent, Ava; Merz M-PM, Merz; Polident d.o.o, Poli) and a heat-cured polymethylmethacrylate resin (Promolux, Conv) (n = 30). After polishing, baseline surface roughness (R_a) and color coordinates were measured. The measurements were repeated after 20000 cycles of simulated brushing, and the specimens were divided into 3 groups according to disinfection protocol (distilled water, 1% sodium hypochlorite (NaOCl), and effervescent tablet) (n = 10). After 9 cleaning cycles over a period of 20 days, R_a and color coordinates were remeasured. Color differences (ΔE₀₀) were calculated by using CIEDE2000 formula. One-way analysis of variance (ANOVA) and pairwise t-tests were used to analyze R_a and ΔE₀₀ data, while repeated measures ANOVA test was used to compare baseline, after brush, and after disinfection R_a values (α = 0.05).

Results: Brushing did not affect the R_a values of tested materials (P ≥ .08). Both before and after brushing, Merz and Conv had higher R_a values than Poli and Ava (P < .001). Among disinfectants, effervescent tablet led to the lowest R_a for Merz (P = .003) and the highest R_a for Poli (P ≤ .039). Only NaOCl resulted in significant differences among the R_a of materials (P < .001), as Merz and Conv had higher R_a values than Poli (P ≤ .002). Repeated measures ANOVA revealed that effervescent tablet disinfection of Merz led to lower R_a values than those of baseline and after brushing (P ≤ .042). After brushing, Ava and Conv had higher ΔE₀₀ values compared with Merz and Poli (P ≤ .015). When compared with other disinfection protocols, effervescent tablet led to higher ΔE₀₀ values for Merz and Poli (P < .001). Significant differences were observed among materials when NaOCl was used; Conv had higher ΔE₀₀ values than Ava and Merz (P = .004).

Conclusions: Brushing did not increase the surface roughness of materials. Disinfection protocol's effect on the surface roughness varied. The effect of brushing on the color of materials varied; color of Ava and Conv was affected from brushing more than the other materials. Color stability of materials varied depending on the disinfection protocol. Effervescent tablet caused higher color change with Merz and Poli compared with other disinfectants. NaOCl led to small color change for Poli, Ava, and Merz materials.

Keywords: CAD-CAM; Color stability; Denture base; Disinfection; Simulated brushing; Surface roughness.