Effect of Different Surface Treatments and Toothbrushing Durations on Surface Roughness and Color Stability of CAD/CAM Interim Crown Material

The clinical performance of interim restorations, particularly in the anterior region, largely depends on surface roughness (Ra) and color stability. This study investigated the influence of different toothbrushing durations on the surface roughness and color stability of CAD/CAM interim restorative materials subjected to varying polishing protocols. A total of 140 rectangular specimens (15 × 9 × 2 mm) were fabricated from highly cross-linked PMMA blocks (Telio-CAD, Ivoclar Vivadent, Schaan, Liechtenstein) and allocated to two surface treatment groups: conventional polishing and surface coating with Optiglaze Color (GC Corp, Tokyo, Japan). Each group was further divided into seven subgroups (n = 10), including a control (no brushing) and groups that performed simulated brushing (DentArge TB-6.1, Analitik Medikal, Gaziantep, Turkiye) with distilled water or toothpaste (Colgate Total; Colgate-Palmolive, New York, NY, USA), for 2 weeks, 3 months, or 1 year. Ra values were recorded before (Ra0) and after brushing (Ra1), and color changes (ΔE00) following immersion in coffee solution were calculated. Statistical analysis was performed using a three-way ANOVA and Tukey’s HSD test (α = 0.05). Specimens coated with Optiglaze Color exhibited significantly lower Ra values compared with conventionally polished specimens (p < 0.05). The Con_Tp_1Yr group demonstrated the highest Ra value (0.53 ± 0.08 µm) compared to all other specimen groups (p < 0.05). A one-year brushing duration markedly increased ΔE00 values in both surface treatment groups regardless of brushing medium (p < 0.05). While surface coating was more effective than conventional polishing in obtaining smoother surfaces at all brushing durations, prolonged brushing with toothpaste produced a progressive increase in surface roughness in both treatments. Ra values increased consistently over time, with the most pronounced changes observed after one year of brushing. Within the limitations of using a single CAD/CAM material, it may be concluded that surface coating improves the initial smoothness of interim crowns; however, extended brushing and different brushing media can intensify color changes, indicating that the long-term stability of surface-coated interim restorations may be compromised under abrasive conditions.