Effectiveness of a hydrophilic primer when different antimicrobial agents are mixed

The purpose of this study was to determine whether different types of antimicrobial agents with hydrophilic primer applied to etched enamel surfaces will affect the shear bond strength (SBS) and the bracket/adhesive failure modes of metallic orthodontic brackets. Eighty noncarious human premolars were divided into four groups of 20 each. A composite resin (Transbond XT) was used to bond stainless steel brackets. Teeth in the first group were used as a control and bonded with standard procedures. For the other three groups, mixtures containing a hydrophilic primer (Transbond MIP) and one of three anti-microbial agents were prepared (Cervitec: in 1:2 ratio; chlorhexidine mouthwash and EC40 varnish in 1:1 ratio). These mixtures were applied to the etched enamel surfaces and thoroughly light cured for 20 seconds, and the brackets were bonded and light cured for 40 seconds. The SBS values of these brackets (Mpa) were recorded using a universal testing machine. Adhesive Remnant Index scores were determined after failure of the brackets. Data were analyzed using analysis of variance (ANOVA), Tukey honestly significant difference, and chi-square tests. Results of ANOVA revealed statistically significant differences in bond strengths among the various groups tested (P < .05). The bond strength values in these four groups compared favorably with those from other studies and the minimal bond strength values that are clinically acceptable. However, results of this study demonstrated that groups 1 (control) and 2 (Cervitec varnish) had higher SBS values than the other applications. Application of different antimicrobial agents may result in differences in the site of failure.