Effect of surface finishing procedures on the color stability of a 3D-printed permanent resin material in artificial saliva at different pH levels: an in vitro study

New additively manufactured (AM) permanent crown materials are becoming increasingly widespread in clinical and scientific fields. However, limited information is available on the color stability related to surface characteristics under various oral environmental conditions. This study aimed to evaluate the color stability and surface changes of AM permanent resin material produced using two different surface finishing procedures at three pH levels of artificial saliva (AS). The study included six experimental groups, each with 10 specimens. A total of 60 disc-shaped BEGO TriniQ (Bego, Bremen, Germany) specimens were fabricated using a digital light processing (DLP) 3D printer. The specimens were allocated according to the surface-finishing procedure and the three AS pH levels (3, 7, 12). Three groups received mechanical polishing only (M3, M7, and M12), whereas the remaining three groups received mechanical polishing followed by glaze coating with GC Optiglaze (GC, Tokyo, Japan) (MG3, MG7, and MG12). The specimens were immersed in AS at pH 3, 7, or 12 for 21 days. Before and after immersion, surface topography and spectroscopic analyses were performed using FESEM, XRD, and FTIR, and color changes were calculated using the CIEDE2000 (ΔE 00 ) formula. Two-way ANOVA, One-Way ANOVA followed by Bonferroni post-hoc test, and Independent samples t-test were conducted after confirming normal distribution, with significance accepted at ( p < 0.05). Both surface finishing procedure and AS pH level had statistically significant effects on ΔE 00 ( p < 0.001), whereas their interaction was not significant ( p = 0.123). Significant differences were found across pH levels within both surface groups ( p = 0.031 for MG; p = 0.004 for M), and within both surface finishing groups, ΔE 00 at pH 12 was significantly greater than at pH 3 and pH 7 ( p < 0.05). The M groups exhibited significantly higher ΔE 00 values than MG groups at all pH levels ( p = 0.003, p < 0.001, and p < 0.001 for pH3, 7, and 12, respectively). All MG groups remained below the 50:50 acceptability threshold (AT = 1.8) under all pH conditions. The surface-finishing procedure and the AS pH level independently affected the color stability of the tested AM permanent resin material. MG specimens showed lower ΔE 00 values than M specimens under all AS pH conditions, while the greatest ΔE 00 values were observed under highly alkaline AS.