Effect of Different Surface Pre-Treatments on the Repair Bond Strength of Resin Composite Subjected to Artificially Accelerated Aging: An in vitro Study

Abstract

Aim: This in vitro study aimed to evaluate and compare the surface roughness and shear bond strength (SBS) of aged composite repairs using three surface pretreatment methods—diamond bur (DP), tungsten carbide bur (TC), and air abrasion (AA)—in combination with two universal adhesives: Prime & Bond Universal (PBU) and Single Bond Universal (SBU). Methodology: Seventy-two composite discs were fabricated and aged by thermocycling. Specimens were randomly divided into three groups (n=24) based on surface pretreatment: Group A (DP), Group B (TC), and Group C. Surface roughness (Ra) was assessed using a profilometer on half the specimens from each group. All specimens were then acid-etched and further subdivided based on the adhesive used (SBU or PBU, n=12 each). Neo Spectra ST was bonded over the treated surface using a cylindrical mold and light-cured. SBS testing was conducted using a UTM, and failure modes were analyzed under stereomicroscope. Results: Surface roughness values varied across treatment groups, with air abrasion showing the highest Ra, followed by TC and DP. SBS results indicated that surface pre-treatment significantly influenced bonding efficacy. SBU demonstrated slightly higher SBS compared to PBU across most surface treatments. The highest SBS was observed in the group treated with DP combined with SBU (C2), suggesting a synergistic effect between mechanical and chemical bonding. Mixed failure modes were most common. Conclusion: Diamond point, followed by air abrasion application of Single Bond Universal yielded the most favorable outcomes, indicating superior micro-mechanical interlocking and chemical adhesion.