Method: Forty universal light-cured nano resin composite specimens (KALORE™ - GC America Inc.) aged in distilled water for three months. Specimens were randomly assigned into 4 groups (n=10) according to the following surface treatment methods: Control, untreated surface, no roughening or abrasion of the surface; 2) 600-grit and etching with 35% phosphoric acid; 3) Etching with 35%phosphoric acid and application of bonding agent; and 4) Roughening with diamond burs, etching with 35% phosphoric acid and application of bonding agent. Specimens were stored for 24 hours at 37 degrees C and 100% relative humidity. All groups received new composite resin application using a split bisected Teflon matrix and shear bond strength was measured using an Instron testing machine running at a crosshead speed of 0.5mm/min. Data were analyzed by two-way analysis of variance and Tukey’s post hoc test (p = 0.05).
Result: There were significant treatment and material interaction effects (p<0.01). Significant differences were found between the groups. Roughening with diamond burs, etching with 35%phosphoric acid and application of bonding agent showed significantly higher shear bond strength than no treatment/control. For all other experimental groups, no significant difference in shear bond strength at the repair interface was identified.
Conclusion: Assessing shear bond strength at the interface between aged and new composites showed that roughening with diamond burs, etching with 35% phosphoric acid and application of bonding agent produces the highest repair strength between aged and new composites. The adhesive used as an intermediate agent was important in composite resin repair.
Keywords: Adhesion, Bonding and Composites
See more of: Dental Materials 1: Adhesion - Bond Strength Testing and Mechanisms