Effect of polishing and denture cleansers on the surface roughness of new-generation denture base materials and their color change after cleansing.

Purpose: To evaluate the effect of polishing and denture cleansers on the surface roughness (R) of new-generation denture base materials that are additively, subtractively, and conventionally fabricated, while also assessing their color change after cleansing.

Material And Methods: One hundred and fifty disk-shaped specimens (Ø10 × 2 mm) were prepared from five denture base materials (one subtractively manufactured nanographene-reinforced prepolymerized polymethylmethacrylate (PMMA) (SM-GC), one subtractively manufactured prepolymerized PMMA (SM-PM), two additively manufactured denture base resins (AM-DT and AM-ND), and one heat-polymerized PMMA (CV) (n = 30). The R of the specimens was measured before and after conventional laboratory polishing, while color coordinates were measured after polishing. Specimens were then divided into three subgroups based on the denture cleanser: distilled water, 1% sodium hypochlorite (NaOCl), and effervescent tablet (n = 10). The R and color coordinates were remeasured after nine cleansing cycles over a period of 20 days. The CIEDE2000 formula was used to calculate the color differences (ΔE). Two-way analysis of variance (ANOVA) was used to analyze the R values before (n = 30) and after (n = 10) cleansing, while repeated measures ANOVA was used to analyze the R of material-time point pairs within each denture cleanser (n = 10). ΔE data after denture cleansing was also analyzed by using two-way ANOVA (n = 10) (α = 0.05).

Results: Before polishing, R varied significantly among the materials. SM-GC and SM-PM had the lowest and AM-ND the highest R values (P < 0.001). Polishing significantly reduced R of all materials (P < 0.001), and after polishing, R differences among materials were nonsignificant (P ≥ 0.072). Regardless of the denture cleanser, the R of AM-DT, AM-ND, and CV was the highest before polishing when different time points were considered (P < 0.001). After cleansing, AM-ND had the highest R of all the materials, regardless of the cleanser (P ≤ 0.017). AM-DT had higher R than SM-PM when distilled water (P = 0.040) and higher R than SM-GC, SM-PM, and CV when NaOCl was used (P < 0.001). The type of cleanser significantly influenced the R of AM-DT, AM-ND, and CV. For AM-DT, NaOCl led to the highest R and the tablet led to the lowest R (P ≤ 0.042), while for AM-ND, distilled water led to the lowest R (P ≤ 0.024). For CV, the tablet led to lower R than distilled water (P = 0.009). Color change varied among the materials. When distilled water was used, SM-GC had higher ΔE than SM-PM and AM-DT (P ≤ 0.034). When NaOCl was used, AM-ND had higher ΔE than SM-GC, SM-PM, and AM-DT, while CV and SM-GC had higher ΔE than SM-PM and AM-DT (P ≤ 0.039). Finally, when the tablet was used, AM-ND and CV had the highest ΔE, while AM-DT had lower ΔE than SM-GC (P ≤ 0.015).

Conclusions: The tested materials had unacceptable surface roughness (>0.2 μm) before polishing. Roughness decreased significantly after polishing (<0.2 μm). Denture cleansers did not significantly affect the surface roughness of the materials, and roughness remained clinically acceptable after cleansing (<0.2 μm). Considering previously reported color thresholds, AM-ND and CV had unacceptable color change regardless of the denture cleanser, and the effervescent tablet led to perceptible, but acceptable color change for SM-GC, SM-PM, and AM-DT.