Comparison of surface treatment protocols for a 3D-printable resin for definitive crowns: Effects on surface...

This study aimed to compare the effects of surface treatment protocols on the surface roughness and shear bond strength (SBS) of a three-dimensional (3D)-printable resin for definitive crowns.

A 3D-printable resin for definitive crowns (Saremco Print Crowntec) was used to produce 168 specimens (10 × 10 × 2 mm³) using liquid crystal display (LCD)-based technology. Specimens were allocated to seven surface treatment groups (n = 24/group): control, Al₂O₃ air abrasion (110 µm, 50 µm), 9% hydrofluoric acid (HF) etching (1 and 3 min), and CO₂ laser treatment with parallel and grid patterns. Each group included 12 specimens with primer and 12 specimens without primer. Dual-cure cement was applied via cylindrical molds (Ø2.38 × 3 mm). SBS tests were conducted. Data were analyzed using two-way ANOVA and the Tukey test (p < 0.05).

Surface treatments significantly affected SBS (p < 0.001). The highest SBS was with 110-µm Al₂O₃ air abrasion (14.05 ± 3.78 MPa), followed by CO₂ laser with parallel lines (11.86 ± 5.51 MPa). The 1-min HF etching (9.47 ± 4.04 MPa) and the control group (7.08 ± 2.98 MPa) showed low SBS. The primer application did not significantly affect SBS. A weak positive correlation was found between SBS and surface roughness (r = 0.297, p = 0.006).

Air abrasion with 110-µm Al₂O₃ provided the highest bond strength for 3D-printed restorations. CO₂ laser with parallel line patterns was an alternative. Under the tested conditions, 1-min HF etching showed low bond strength, whereas a 3-min application resulted in improved outcomes. Surface roughness appears to aid bonding, but is not sufficient alone.