Assessing shear bond strength of various surface treatments of 3D-printed provisional material with bis-acryl relining material.

Objective: Marginal adaptation of the provisional restoration often requires relining from relining materials. This study determined the effects of surface treatments on the shear bond strength (SBS) between 3D-printed provisional and bis-acryl relining materials.

Materials And Methods: The 3D-printed provisional specimens (9 × 9 × 2 mm) were prepared using methacrylate-based material. Five test groups (n = 15) based on surface treatments were evaluated; (1) no treatment (CT), (2) ethanol (ET), (3) universal adhesive; CLEARFIL TRI-S BOND Universal Quick (UA), (4) airborne-particle abrasion with 50 μm aluminum oxide particles (AA), and (5) airborne-particle abrasion followed by universal adhesive (AA-UA). The specimens were bonded with relined bis-acryl resin material and left at room temperature for 24 h, allowing the complete polymerization. Then, shear bond strength was performed using a universal testing machine with a knife-edge blade parallel to the bonded surface at a crosshead speed of 1 mm/min until failure occurred. The fracture surfaces were examined under stereomicroscopy (20X) and scanning electron microscopy (50X).

Results: The CT group had the lowest shear bond strength (1.92 ± 0.26 MPa), which was no statistically significant difference from ET (2.11 ± 0.23 MPa). The significantly highest shear bond strength was obtained from AA-UA (14.39 ± 1.07 MPa) (p < 0.05), followed by AA (6.39 ± 0.59 MPa) and UA (3.34 ± 0.21 MPa), respectively. Failure modes obtained were varied, with mixed and cohesive failures in AA-UA (46.6% mixed failures) and AA groups (66.6% mixed failure) whereas primarily adhesive failures were observed in CT (93.5%), ET (86.6%), and UA groups (86.6%).

Conclusions: Within the limitation of this study, the optimal bond strength was obtained when airborne-particle abrasion and universal adhesive were applied on the 3D-printed provisional material and relined with bis-acryl relining material.