Influence of polishing technique and coffee thermal cycling on the surface roughness and color stability of additively and subtractively manufactured resins used for definitive restorations

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 a and color coordinate measurements were performed after polishing and after coffee thermal cycling. Color difference (ΔE 00 ) 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 a of 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 a at different time intervals within each material-polishing pair. ΔE 00 was assessed with 2-way ANOVA (α = 0.05). Results: Other than VA-after polishing (p = 0.055), tested materials had significantly different R a within each polishing-time interval pair (p ≤ 0.038). When R a differences 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 a differences among different time intervals within each material-polishing pair were considered, significant differences were observed among all pairs (p ≤ ...