Comparison of Composite Repair Shear Bond Strength with Different Adhesive Systems

Various methods of surface roughening and adhesives have been advocated for use in composite repair.   The efficacy of one-step self-etching adhesive systems compared to total-etch adhesives for composite repair has not been determined.  Objective: This study evaluated composite repair shear bond strengths (SBS) for 1) an experimental, one-step self-etching adhesive, EXM-618 (EXM) 3M/ESPE, 2) a two-step total-etch primer/adhesive, Single Bond (SB) 3M/ESPE, and 3) a three-step total-etch adhesive, ScotchBond Multipurpose Plus (SBMP) 3M/ESPE (control) using different surface preparations.  Methods: one hundred and eight resin composite cylinders were fabricated using Z-250 hybrid resin composite (3M/ESPE ) and randomly assigned to one of three surface preparation groups (n=36):  800-grit silicon carbide paper polished surface as a control (C),  Diamond Bur (B); or Microetcher (M); 50 µm Al₂O₃.  Following surface preparation, specimens were further randomly assigned to one of the three adhesive groups (n=12), all adhesives were used according to manufacturer’s instructions for composite repair.  Restorative Z-250 resin composite was bonded to the pre-polymerized resin cylinders using a custom jig (Ultradent), 2.38 mm dia x 2.5 mm ht and light-cured 40 seconds from the surface.  Specimens were thermocycled 500 times between 55°C and 5°C.  SBS was determined using a Zwick Materials Testing Machine at a crosshead speed of 5 mm/min. Results:  Kruskal-Wallis and Tukey HSD post hoc Test (alpha=0.05) indicated statistically significant differences between the experimental groups as indicated by the different letters in the table.

Conclusion: self-etching primer/adhesive systems provide comparable SBS to conventional adhesives for composite repair.  This research was supported by 3M/ESPE.