Purpose: To evaluate how different polishing techniques and coffee thermal cycling affect the surface roughness and stainability of additively and subtractively manufactured resins used for definitive prostheses.

Materials and methods: Two additively manufactured composite resins (Crowntec, CT and VarseoSmile Crown Plus, VS) and a subtractively manufactured resin nanoceramic (Cerasmart, CS) were used to fabricate 90 rectangular-shaped specimens (14 × 12 × 1 mm) (n = 30). After baseline surface roughness (R_a) measurements, specimens were divided into three groups based on the polishing technique; conventional polishing with a 2-stage polishing kit (CP) and surface sealant application (Optiglaze, OG or Vita Akzent LC, VA) (n = 10). After polishing, specimens were subjected to 10,000 cycles of coffee thermal cycling. R_aand color coordinate measurements were performed after polishing and after coffee thermal cycling. Color difference (ΔE₀₀) was calculated. Scanning electron microscope images were taken at each time interval. Kruskal-Wallis or 1-way analysis of variance (ANOVA) were used to evaluate R_aof materials within each polishing-time interval pair and different polishing techniques within each material-time interval pair, while Friedman or repeated measures ANOVA were used to evaluate R_aat different time intervals within each material-polishing pair. ΔE₀₀was assessed with 2-way ANOVA (α = 0.05).

Results: Other than VA-after polishing (p = 0.055), tested materials had significantly different R_awithin each polishing-time interval pair (p ≤ 0.038). When R_adifferences among different polishing techniques within each material-time interval pair were considered, CS had differences after coffee thermal cycling, CT had differences before polishing and after coffee thermal cycling, and VS had differences within each time interval (p ≤ 0.038). When R_adifferences among different time intervals within each material-polishing pair were considered, significant differences were observed among all pairs (p ≤ 0.016), except for CS-VA (p = 0.695) and VS-VA (p = 0.300). ΔE₀₀values were affected by material and polishing technique interaction (p = 0.007).

Conclusions: R_aof CS was similar to or lower than the R_aof other materials, regardless of the time interval or polishing technique. CP mostly led to lower R_athan other polishing techniques, whereas VA resulted in a high R_aregardless of the material-time interval pair. Polishing reduced the R_a, while coffee thermal cycling was found to have a small effect. Among tested material-polishing pairs, only CS-VA had moderately unacceptable color change when previously reported threshold values were considered.