Effect of Air Abrasion, Diamond Bur Roughening and Hydrofluoric Acid Etching on Shear Bond Strength of Repaired Resin Composites: An In Vitro Study

Abstract

Background: Composite restorations often fail over time, and repair is a minimally invasive alternative to replacement that preserves tooth structure.

Objectives: To evaluate and compare the effect of various surface treatments on the shear bond strength of repaired dental composite restorations.

Methodology: This experimental in-vitro study was conducted from Jan 24 to Mar 25 after the approval of Review Board of Azra Naheed Dental College, on 60 cylindrical micro-hybrid composite specimens fabricated in Teflon molds, light-cured in 2.5-mm increments, stored in distilled water at 37°C for 24h, and thermocycled for 500 cycles. The samples were divided into to 4 groups (n=15): Group A (silane only), B (air abrasion with 50µm Al₂O₃+silane+adhesive), C (diamond bur roughening+silane+adhesive) and D (9% HF etching+silane+adhesive). A repair layer of the same composite was applied to form bilayer samples. SBS was measured using universal testing machine.

Results: All 60 specimens were tested. The overall SBS was 18±8.07 MPa. Mean SBS (MPa) in the air abrasion group (B) was 30.47±2.03, followed by diamond bur group (C) 18.17±2.10, HF 13.96±1.19 (D) and the control group (A) 9.42±1.20. Surface treatment significantly affected SBS (p<0.001). Tukey HSD showed that all pairwise associations were significant (p<0.001).

Conclusion: Air abrasion produced the highest repair SBS and the most favorable failure pattern, outperforming diamond bur roughening, HF etching and silane treatment. Air abrasion is the preferred surface treatment for composite repair, however, diamond bur is an acceptable alternative, while HF etching is least favorable as the primary conditioning method.

Keywords: Air Abrasion, Dental; Composite Resins; Dental Restoration, Hydrofluoric Acid; Shear Strength; Surface Properties