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.