Effect of surface treatment protocols and thermocycling on the optical, surface, and mechanical properties of additively manufactured resin materials.

OBJECTIVES: This study evaluated the effects of surface treatment protocols and thermocycling on the optical, surface, and mechanical properties of additively manufactured resins. MATERIALS AND METHODS: Five materials (saremco print CROWNTEC, VarseoSmile Crownplus, VarseoSmile TriniQ, VarseoSmile TriniQ for Formlabs, and Ceramic Crown) were assigned to six groups: control, silane, sandblasting (SB), SB+silane, hydrofluoric acid (HFA), and HFA+silane. After surface treatments and 5,000 thermocycles, color change (ΔE₀₀), translucency (ΔTP₀₀), gloss, surface roughness (Ra), and microhardness (VHN) were measured. Data were analyzed using robust ANOVA and aligned rank transform (ART) mixed ANOVA with Holm-adjusted multiple comparisons (α = 0.05). RESULTS: Material type, surface treatment, and aging significantly affected all evaluated parameters (p < 0.001). Following surface treatment (T1), SB and SB + S groups exhibited significantly higher surface roughness and microhardness compared with control, silane, HFA, and HFA + S groups (p < 0.001). In terms of ΔE₀₀, SB and SB + S groups exceeded the clinical acceptability threshold (ΔE₀₀ > 1.8), whereas C, S, HFA, and HFA + S groups remained below the perceptibility threshold at T1. After thermocycling (T2), clinically unacceptable color changes were observed in most treatment groups, gloss values decreased significantly, and microhardness increased (p < 0.001). ΔTP₀₀ values were significantly influenced by material type (p < 0.001) but not consistently by surface treatment. Gloss values decreased significantly over time (p < 0.001), with the lowest values observed at T2. Among the materials, Ceramic Crown showed significantly higher microhardness and lower color change compared with the others (p < 0.05). CONCLUSIONS: Surface treatments and thermocycling significantly affect additively manufactured resins; mechanical pretreatments improve hardness but may compromise optical properties. CLINICAL RELEVANCE: Careful selection of surface treatment protocols is required to achieve a balance between mechanical performance and esthetic outcomes in additively manufactured restorations.