Bond strength for orthodontic brackets contaminated by blood: Composite versus resin-modified glass ionomer cements

Purpose: The purpose of this study was to evaluate and compare the shear bond strengths of a self-cured glass ionomer versus composite cement for bonding of stainless steel buttons with various enamel surface and setting conditions. Materials and Methods: Stainless steel orthodontic buttons were bonded using composite material under 3 different enamel and setting conditions: 1) conditioned and dry enamel surface, 2) conditioned and precontamination of the enamel surface with blood before bonding, 3) conditioned and immediate blood contamination postbonding and were compared with 3 different enamel conditions and setting for bonding with the glass ionomer cement: 1) nonconditioned and wet enamel surfaces, 2) nonconditioned and blood contamination of enamel before bonding, and 3) nonconditioned and immediate blood contamination postbonding. The brackets were bonded to 109 recently extracted teeth and allowed to set in a moist plastic container for 24 hours. They were subsequently tested in shear mode with a universal testing machine. The maximum bond strength and the site of bond failure were recorded. In addition, the location of the bond failure was studied. Results: Composite was capable of sustaining greater forces than the resin-modified glass ionomer materials. Hence, it took more force to debond a bracket cemented with composite than with resin-modified glass ionomer. The effect of contamination was similar in both of the materials, and the magnitude of the decrease in bond strength was nearly of the same proportion. The postcontamination values were not significantly different from the uncontaminated bond strength for either material. The type of bond failure was significantly different for the different materials, and there were significant differences among the treatment conditions. Conclusion: Composite resin had significantly greater shear strength than resin-reinforced glass ionomer cement. Both materials showed a significant decrease in bond strength when precontaminated with blood. The postcontamination values were not significantly different from the uncontaminated bond strength for either material.