Stain susceptibility and cleanability of conventional, CAD-CAM, and 3D-printed denture teeth

This in vitro study aimed to evaluate: (1) the effects of staining agent type and denture tooth material type on the color stability of newly developed milled and 3D-printed denture tooth materials compared with conventional polymethylmethacrylate (PMMA) denture teeth and (2) the effect of denture cleanser on the color stability of these materials.

A total of 200 disc specimens (4 mm thick, 10 mm diameter; shade A1) were fabricated from five denture tooth materials (n = 40 each): conventional PMMA (HP-Jet), milled CAD-CAM resins (Ivotion [SM-I], Candulor [SM-C]), and 3D-printed resins (Flexcera [AM-F], Straumann [AM-S]). Each group underwent two sequential procedures: staining followed by cleaning. Specimens were immersed in one of four staining solutions-deionized water (control), orange juice, coffee, or red wine-for a standardized period (n = 10 per solution/material). Color was measured at baseline, post-staining, and post-cleaning using a calibrated spectroradiometer. Color changes (ΔE₀₀) were calculated using the CIEDE2000 formula. Cleaning was performed using denture cleaning tablets per the manufacturer's instructions. Statistical analysis included two-way ANOVA with interaction and Tukey post hoc tests for staining and material effects, and repeated-measures comparisons with Šídák adjustment for the effect of cleaning (α = 0.05).

Both material type and staining agent significantly influenced color change (p < 0.05). Most groups showed perceptible but clinically acceptable discoloration (ΔE₀₀ > 1.2 and < 2.7). SM-C and AM-F exposed to orange juice exhibited minimal changes (ΔE₀₀ < 1.2). AM-F stained with red wine showed the highest color change (ΔE₀₀ = 4.49 ± 0.73), exceeding clinical thresholds. No significant differences were observed among materials stained with orange juice or coffee (p > 0.05). Cleaning significantly reduced ΔE₀₀ values (p < 0.05), especially for most of the wine-stained specimens, with several groups achieving post-cleaning ΔE₀₀ < 1.2.

The color stability of denture tooth materials is influenced by both resin type and staining agent. While most materials demonstrated perceptible yet clinically acceptable discoloration, red wine caused significant staining, particularly in 3D-printed AM-F. Cleaning was effective in reducing discoloration, often restoring color to imperceptible levels.