Bond Strengths of Repaired Composite-Repair Interface using Different Surface Treatments

Objective: This study determined the in vitro shear bond strength of repaired aged nano-filled resin composite-repair interface using different surface treatments.

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.