Effect of toothbrushing abrasion on color stability and surface roughness of four permanent crown materials produced by additive and subtractive manufacturing

The clinical performance of permanent crown materials depends on their ability to maintain optical and surface properties under mechanical challenges such as toothbrushing. However, comparative data on the effect of toothbrushing abrasion on materials produced by different manufacturing techniques are still scarce. This study aimed to compare the effects of toothbrushing abrasion on the color stability and surface roughness of four permanent crown materials produced by additive and subtractive manufacturing techniques. A total of 104 specimens were prepared from four materials, each divided into two independent subgroups for color and surface roughness analyses ( n = 13), resulting in 26 specimens per material. The materials included a three-dimensionally printed (3D-printed) resin (VarseoSmile Crown Plus), a resin composite computer-aided design/computer-aided manufacturing (CAD/CAM) block (Tetric CAD), a lithium disilicate glass-ceramic (IPS e.max CAD) and a feldspathic ceramic (VITA Mark II), which were finished according to the protocol recommended for each material. Color parameters (L*, a*, b*) and surface roughness (Ra) were measured before and after standardized toothbrushing simulation using an electric toothbrush, representing approximately two years of clinical use. Color differences were calculated using the CIEDE2000 (ΔE₀₀) formula, and surface morphology was qualitatively assessed by scanning electron microscopy. Statistical analyses were performed using non-parametric tests ( p < 0.05). No statistically significant differences were found among the materials in terms of color change (ΔE₀₀) after toothbrushing ( p = 0.238). Toothbrushing significantly increased surface roughness in all groups ( p ≤ 0.002), although the magnitude of change did not differ significantly among materials ( p = 0.068). The median ΔE₀₀ remained below the perceptibility threshold (0.8) in all materials, whereas individual specimens exceeded it most frequently in Tetric CAD (5/13) and VarseoSmile Crown Plus (6/13), and three specimens exceeded the acceptability threshold (1.8). Toothbrushing abrasion significantly increased surface roughness in all materials, whereas the median color change remained below the perceptibility threshold. Because only one additively manufactured resin was evaluated and the materials also differed in composition and surface-finishing protocol, these findings apply to the materials tested rather than to additive or subtractive manufacturing in general.