Comparison of Two Self-Etching Primers and Effect of Saliva Contamination on Shear Bond Strength of Orthodontic Brackets

AbstractIntroductionSaliva contamination during the bonding procedure is a common cause of bracket bond failure. By combining acid and primer in one component, self-etching primers (SEP) reduce the working time and the risk of contamination.ObjectivesThe purpose of this study was to investigate the effect of saliva contamination of the enamel surface on the shear bond strength of orthodontic brackets cemented with two self-etching primers.Materials and MethodsOne hundred orthodontic brackets were bonded to human premolars with Transbond Plus Self-etching Primer (TPSEP, 3M Unitek, Monrovia, CA) or First Step (FS, Reliance Orthodontic Products, Itasca, IL) under the following enamel surface conditions: 1) dry enamel; 2) saliva contamination/primer; 3) saliva contamination/air drying/primer; 4) primer/saliva contamination; 5) primer/saliva contamination/air drying/reapplication of the primer. Samples were stored for 7 days in water at 37°C and submitted to 500 cycles of thermal stress. Bond failure sites were classified by an Adhesive Remnant Index score system.ResultsMean shear bond strengths were significantly higher in the TPSEP groups compared to the FS groups (p<.001). For the same adhesive, no significant differences were found between the enamel surface conditions. More adhesive failures were observed in the FS groups.ConclusionsBrackets bonded with TPSEP had the highest shear bond strength values, under the different enamel surface conditions. For both SEPs, bond strengths were not significantly affected by the enamel surface conditions. The FS groups failed more frequently at the enamel /resin interface