Evaluation of the shear bond strength of surface-treated cobalt-chromium metal crowns on Corticobasal® implant abutments cemented using different luting agents

Purpose

This in-vitro study aimed to compare the shear bond strength (SBS) of cobalt-chromium (Co-Cr) crowns on Corticobasal® implant abutments, evaluating the effects of two surface treatments and two luting agents.

Materials and Methods

Thirty Co-Cr crowns were fabricated using CAD-CAM technology with a direct metal laser sintering process and divided into three groups based on surface treatment: Group I (untreated), Group II (sandblasted with 50 μm Al₂O₃), and Group III (Er: YAG laser etching). Each group was further subdivided based on luting cement: Sub group A (GC Fuji Plus) and Sub group B (Rely X U200).

This resulted in a total of six groups. The implants were stabilized in auto-polymerizing acrylic resin, and cementation followed standardized protocols. Thermocycling with 1000 cycles (5 °C–55 °C) simulated oral conditions. SBS was tested using a universal testing machine at a crosshead speed of 1 mm/min. Failure patterns were analyzed using stereomicroscopy to classify adhesive, cohesive, and mixed failures. Statistical analysis was performed using one-way ANOVA and Bonferroni post-hoc tests (p < 0.05).

Results

Group IIIA (laser-treated, GC Fuji Plus) showed the highest SBS (243.15 MPa), followed by Group IIA (sandblasted + GC Fuji Plus), at 231.81 MPa. The lowest SBS was observed in Group IB (untreated, Rely X U200) at 124.24 MPa. Both sandblasting and laser treatment significantly enhanced SBS, with GC Fuji Plus consistently outperforming Rely X U200. A significant difference of 48.17 MPa was observed between laser-treated Groups IIIA and IIIB (p < 0.01).

Conclusion

Laser etching and GC Fuji Plus cementation provided the highest SBS for Co-Cr crowns on Corticobasal® implants. Sandblasting was a secondary effective treatment, while untreated crowns exhibited the weakest bond strength.