Effects of Different Surface Treatments on Bond Strength Between Additively Manufactured Definitive Restorative Materials: An In Vitro Study

Additively manufactured definitive restorative materials have gained popularity recently. The current in vitro study evaluated the effects of surface treatment and thermocycling on the shear bond strength (SBS) between four 3D-printed definitive restorative materials and a self-adhesive resin cement (SARC). Disc-shaped specimens were fabricated from four printable materials: two composite materials, Crowntec (Crowntec) and CRS Composite (Custom Resin Solutions), and two ceramic-filled composites, Alias Dental Crown (Alias) and Permanent Crown (PC) (n = 12 per subgroup). Specimens were divided into four surface treatment subgroups: control, 9% hydrofluoric acid etching (HF), 50 µm aluminum oxide (Al2O3) airborne-particle abrasion (S50), and 110 µm Al2O3 airborne-particle abrasion (S110). SARC was applied using Teflon molds (∅ 3 × 3 mm). After all specimens were stored in water at 37 °C for 24 h, half of the specimens were subjected to 10,000 thermocycles. Subsequently, SBS testing was performed for all specimens. Data were analyzed using Kruskal–Wallis and Mann–Whitney U tests (α = 0.05), and failure modes were classified microscopically. Before thermocycling, compared with control groups, HF significantly decreased SBS in Crowntec, whereas S110 significantly increased SBS in Alias (p < 0.05). After thermocycling, surface-treated CRS and Alias groups showed significantly higher SBS than controls (p < 0.05); Crowntec showed increased SBS after HF and S50, and Permanent Crown only after S50. No significant differences were found among control groups (p > 0.05). Surface-treated groups exhibited mainly mixed and cohesive failures. Surface treatments generally improved the SBS after thermocycling.