Color Stability of Monolithic Zirconia in Various Staining Liquids: An In Vitro Study

Abstract

This study aimed to compare the color stability of monolithic zirconia (MLZ) after immersion in various staining liquids. Fifty MLZ samples (n = 50) were color infiltrated by brushing/painting the samples pre-sintering. All zirconia samples were then brushed inside a toothbrushing simulator machine to create abrasion. Ten samples each were immersed in artificial saliva (gp-1), coffee (gp-2), protein shake (gp-3), chlorhexidine mouthwash (gp-4), and a soft drink (gp-5). Besides chlorhexidine mouthwash (immersion time: 14 days), the samples were immersed in the liquids for 28 days. A spectrophotometer was utilized to observe the color differences (∆E) at the baseline vs. 28 days post-immersion. The means and standard deviations were compared using analysis of variance (ANOVA) and a multiple comparisons test. A p-value < 0.05 was considered significant. The greatest ∆E (4.57) was observed after immersion in the coffee, followed by a soft drink (∆E: 4.03). Chlorhexidine mouthwash immersion of MLZ samples also significantly changed their color stability (∆E: 3.60). The inter-group comparisons revealed statistically significant differences (p < 0.05) when ∆E values of gp-1 (artificial saliva) were compared with all other groups. Significant differences (p < 0.05) were also seen when ∆E values of gp-2 (coffee) were compared with gp-3 (protein shake) and gp-4 (chlorhexidine). All other inter-group comparisons revealed non-significant results (p > 0.05). The results of the present study demonstrate that coffee immersion of MLZ samples causes more significant discoloration (increased ∆E values) than other liquids. Further in vitro and clinical studies are warranted to corroborate the present study’s findings.