Effect of thermocycling and polishing protocols on the optical and mechanical properties of different CAD-CAM and 3D-printed materials.

PURPOSE: To evaluate the influence of material type and polishing protocol on translucency, surface roughness, hardness, and color stability of CAD-CAM and 3D-printed restorative materials before and after thermocycling.

METHODS

A total of 144 disk-shaped specimens (10 x 2 mm) were fabricated from VITA Enamic, Cerasmart, Celtra Duo, and a 3D-printed resin. Each was divided into four subgroups (n=9) based on surface treatment: glaze only; glaze, bur reduction, and composite polishing; glaze, bur reduction, and ceramic polishing; and glaze, bur reduction, and re-glazing. TP, Vickers hardness, surface roughness (Ra), and color change (ΔE) were measured before and after 10,000 thermal cycles. One specimen per group was examined by scanning electron microscopy. Data was analyzed with robust ANOVA (α= 0.05).

RESULTS

Material type and thermocycling significantly affected TP values (P< 0.001). CAD-CAM materials showed higher translucency and overall hardness values than the 3D-printed resin. Surface roughness was influenced by both material and polishing protocol (P< 0.001); glaze-only generally resulted in smoother surfaces, while ceramic polishing was associated with increased surface roughness in certain material groups. Color stability also varied significantly (P< 0.001); CAD-CAM ceramic polish showed the lowest ΔE values, while several 3D-printed groups exceeded clinically acceptable ΔE thresholds after thermocycling.

CLINICAL SIGNIFICANCE: Material type, surface treatment, and thermocycling affected optical and mechanical properties. CAD-CAM materials generally outperformed the 3D-printed resin, especially in translucency and hardness. Mechanical polishing protocols may provide more stable long-term surface characteristics than glazing alone, particularly for esthetically demanding restorations.