The Effects of Dietary pH Changes on Tooth Staining of the Enamel Surface

<p> Purpose: Patients’ demand for dental esthetics has increased in recent years. Additionally, teeth bleaching can improve self-care and oral cavity awareness. However, bleaching is not permanent as the consumption of foods and drinks can cause re-discoloration of teeth. Tooth staining may be caused by drinks such as coffee, wine, and tea, and foods such as curry. However, the mechanism by which these substances cause staining has yet to be clarified. Therefore, in this study we examined the effects of colored food on the enamel surface by dietary pH changes.</p><p> Methods: Extracted mandibular anterior bovine teeth were used as samples. The enamel samples were divided into four groups: turmeric (TM group), red pepper (RP group), tomato (TO group), and Milli-Q water (MQ group) as a control. The samples were immersed in 30 mL of solution for 3 hours in a 37°C incubator while being shaken. Color changes were measured before and after immersion. For colorimetry, L^＊, a^＊ and b^＊ in the CIE1976L^＊a^＊b^＊ color system were measured using a micro-area spectrophotometer, and ΔL^＊, Δa^＊, and Δb^＊ were obtained. Furthermore, the immersion solution was evaluated before and after immersion using a pH meter. A 3D laser microscope was used to measure the surface roughness of enamel.</p><p> Results: The results revealed that the Δa^＊ value, which indicated redness, and the Δb^＊ value, which indicated yellowness, increased due to the influence of natural ingredients in the TM and RP groups. The various natural pigments in food, such as curcumin in the TM group and carotenoids in the RP group, are thought to be involved in the coloration. The enamel surface roughness of the TO group changed significantly before and after immersion. The pH of the TO group was 4.0, which was below the enamel critical pH of 5.5.</p><p> Conclusion: The results of this study suggest that tooth staining of the enamel surface is affected by dietary pH changes.</p>