Effect of Cola on Bond Strength of Composite to Enamel

Objective: The purpose of this study was to evaluate the effect of a soft drink (Coca-Cola) on the shear bond strength of composite to enamel.  Methods: Eighty enamel sections were obtained from human third molars and mounted in PVC pipe.  A small area of the enamel was flattened using 600-grit silicon-carbide paper.  The eighty flattened teeth specimens were randomly divided into four groups of twenty and assigned to a different adhesive: (1) Scotchbond Multipurpose, (3M ESPE), (2) Optibond Solo Plus (Kerr), (3) Clearfil SE Bond (Kuraray), and (4) Clearfil Tri-S Bond (Kuraray).   Each group had ten specimens as controls not exposed to the soft drink.  Ten specimens from each adhesive group were immersed in Coca-Cola at room temperature for 15 minutes then artificial saliva at 37⁰C for 2 hours in the lab oven.  This sequence was repeated 3 times a day for thirty days. All specimens were kept in artificial saliva at 37⁰C when not cycled with soda.  Each specimen had its assigned adhesive applied as per manufacturers' directions, then placed in the Ultradent Jig.  The composite (Filtek Supreme Plus, 3M/ESPE) was inserted into a mold in 2-mm increments to a height of 3-4mm and cured for 20 seconds per increment.  All specimens were stored 24 hrs in 37⁰C distilled water and tested in shear in a universal testing machine (MTS Insight).  A mean shear bond strength value (MPa) and standard deviation was determined per group.  See table.  Data was analyzed with 2-way ANOVA/Tukeys (alpha=0.05). Results:  The 2-way ANOVA found a significant difference between groups based on bonding agent (p<0.016), but not on surface treatment (p=0.935) with no significant interaction (p=0.074). Clearfil Tri-S had significantly lower bond strengths.  Conclusions:  Coca-Cola had no significant effect on the shear bond strength of composite to enamel.