The effect of different mouthwashes on surface properties and Streptococcus mutans adhesion of resin-based materials manufactured with digital methods

This study aimed to compare the effect of different mouthwashes on surface roughness (Ra), contact angle (CA) and S. mutans adhesion of subtractive manufacturing (SM) and additive manufacturing (AM) definitive resin materials. A total of 84 specimens were fabricated using a resin nano-ceramic CAD/CAM block (Cerasmart; GC (SM) ( N = 42) and a definitive resin (Permanent Crown Resin; Formlabs (AM) ( N = 42). The specimens of each manufacturing group were further divided into three immersion subgroups ( n = 14 per subgroup); 1: Control (Fusayama-artificial saliva) (Group SM-F and AM-F), 2: Alcohol-containing mouthwash (Total Care, Listerine) (Group SM-A and AM-A), and 3: Alcohol-free mouthwash (Total Care Zero, Listerine) (Group SM-AF and AM-AF). Baseline Ra and CA measurements were performed on 10 specimens per subgroup, while surface morphology was evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) on two specimens each. Following immersion, all specimens underwent the bacterial adhesion protocol. S. mutans adhesion was quantified on the same 10 specimens used for Ra and CA measurements, whereas SEM and AFM analyses were repeated on the same designated specimens. Depending on the normality of the data, both parametric (independent-samples t -test, one-way ANOVA, Tukey’s/Dunnett’s T3 post hoc tests) and non-parametric (Mann-Whitney U test) analyses were performed, and Spearman’s rank correlation analysis was used to evaluate the relationships among the study variables ( α = 0.05). Immersion medium significantly affected ΔRa ( p = 0.001). Post hoc analysis demonstrated significantly higher ΔRa values in the alcohol-containing mouthwash group than in the control ( p = 0.025) and alcohol-free mouthwash ( p = 0.014) groups. Among the six experimental subgroups, the highest mean ΔRa was observed in Group AM-A ( p < 0.001), whereas the lowest was observed in Group SM-F. No statistically significant differences were observed in ΔCA or S. mutans adhesion ( p > 0.05). The results of this study indicated no significant relationships among Ra, CA, and S. mutans adhesion. Alcohol-containing mouthwash increased the Ra in both SM and AM groups. However, although it tended to increase ΔCA, no statistically significant differences in ΔCA or S. mutans adhesion were observed.