The Influence of Surface Treatment on the Color of Enamel and Dentin: An In Vitro Study Using Machine Learning-Based Analysis

Objective: To investigate how surface treatment affects the color of enamel and dentin, and to evaluate whether the color differences are acceptable.

Materials and methods: Freshly extracted premolars were prepared using diamond burs (blue, red, and yellow tapes). Tooth surfaces were divided into control and acid-etched areas and treated with phosphoric acid (5, 15, 30, 45, and 60 s). Adhesives were applied and light-cured. Hyperspectral images were captured to analyze reflectance spectra, calculating L, a, b, and ΔE2000 values under the D65 illuminant. Enamel and dentin slices underwent atomic force microscopy for surface roughness. A random forest model was trained to assess the effects of multiple factors on color differences. Statistical analyses included one-way ANOVA, Tukey tests, and independent-sample t-test.

Results: Extended acid-etching times notably increased ΔE2000 values for enamel, surpassing acceptable thresholds in all groups except for the 5-s acid-etching followed by adhesive application. Dentin ΔE2000 remained stable regardless of surface treatment. Machine learning highlighted the influence of acid etching and surface roughness on enamel. Bur tape color had minimal impact.

Conclusions: The effects of acid etching on the color vary between enamel and dentin. Greater attention should be focused on enamel surface. Acid-etching time should be appropriately reduced.

Clinical significance: Comprehending the varying impacts of surface treatment on the color of enamel and dentin could contribute to achieving superior esthetic outcomes.