Restoring the Bond: How Different Saliva Clean-Up Methods Impact Composite Filling Repairs

Abstract

This study set out to explore how different ways of cleaning up saliva from dental surfaces affect how strongly new composite fillings bond to old ones. We took 100 specially prepared composite discs, roughened them up by sandblasting, and then split them into 10 groups. These groups included a perfectly clean control, a group we contaminated with saliva but didn't clean, and eight groups where we tried various cleaning methods (like rinsing, rinsing and re-etching, rinsing and re-applying adhesive, just air-drying, rinsing and re-applying a primer/adhesive, rinsing with chlorhexidine, rinsing with ethanol, and a final group that was contaminated but not pre-treated). For the contaminated groups, we put artificial saliva on the surface before applying the adhesive and adding the new composite. Then, we measured how much force it took to break the bond (microshear bond strength) and looked at how the breaks happened.

Our findings clearly showed that saliva contamination drastically weakened the bond strength (10.2±1.5 MPa) compared to our clean control group (28.5±2.1 MPa). But here's the good news: re-applying the universal adhesive after rinsing (Groups 5 and 7) was incredibly effective. These methods brought the bond strengths right back up (26.9±2.0 MPa and 27.2±2.2 MPa, respectively), making them almost as strong as the uncontaminated control. Rinsing and then re-etching with phosphoric acid (25.1±2.3 MPa) also significantly improved the bond. On the other hand, simple rinsing, just air-drying, or using chemical agents like chlorhexidine and ethanol weren't nearly as effective. When we looked at how the bonds broke, we saw that in the effectively cleaned groups, the breaks happened within the material itself, not just at the bond line, which is a sign of a strong connection. In short, saliva is a real problem for composite bonds, but a simple step like rinsing and re-applying the universal adhesive can be a game-changer for restoring that crucial strength.