Influence of Khat Extract on the Color Stability of Glazed and Polished Dental Ceramics: An In Vitro Comparative Study

Aim: To evaluate the impact of Khat extract on the color stability of three different types of dental ceramics: zirconia, lithium disilicate, and feldspathic ceramics, and to compare the stain resistance of polished vs glazed surfaces.Materials and methods: An in vitro comparative study was conducted using 60 circular disc-shaped ceramic samples with dimensions of 10 mm in diameter and 2.0 0.3 mm in thickness, equally divided into three groups, n = 20 each: Zirconia, lithium disilicate, and feldspathic CAD/CAM ceramics.Each group was further subdivided into 10 glazed and 10 polished samples.The specimens were immersed in a freshly prepared Khat extract medium at 37C, with twice-daily solution replacement.Color measurements were performed using spectrophotometry at baseline, 1 day, and 7 days.Color differences (E*) were calculated.Data were statistically analyzed using independent t-tests and ANOVA tests, with p-value < 0.05 considered significant.Results: The mean E* values indicated significant color changes in all subgroups.The polished samples exhibited higher levels of discoloration compared to the glazed ones.Among the materials tested, polished Feldspathic ceramics showed the greatest color change (E* =11.49after 7 days), followed by polished lithium disilicate (E* = 4.85).Conversely, CAD/CAM glazed zirconia demonstrated the highest resistance to Khat-induced staining (E* =0.70).Statistical analysis confirmed that the differences in color changes between glazed and polished samples were significant (p < 0.05).Conclusion: Khat extract significantly affects the color stability of dental ceramics, with polished surfaces being more prone to staining than glazed ones.Glazed zirconia exhibited the highest stain resistance, whereas polished feldspathic ceramics were the most susceptible.Clinical significance: Identifying the effect of Khat on ceramic discoloration, especially in regions where Khat chewing is prevalent, supports better material selection and finishing strategies for patients, helping improve long-term esthetic outcomes.