Effects of different chlorhexidine pretreatments on adhesion of metal brackets in vitro

Ninety bovine enamel specimens were allocated to six groups (n=15). Metal brackets were bonded on all specimens after chlorhexidine pre-treatments forming the following groups: (1) untreated specimens (control); (2) 40% varnish (EC40, Biodent BV, Netherlands), remnants removed with brushing mimicking patient cleaning; (3) 40% varnish (EC40), remnants removed with brushing mimicking professional cleaning; (4) 1% varnish (Cervitec Plus, Ivoclar vivadent, Schaan, Liechtenstein), remnants not removed; (5) brushed with% 1 gel (Corsodyl, GlaxoSmithKline, Münchenbuchsee, Germany), remnants not removed; (6) immersed in 0.07% mouthrinse (Corsodyl, GlaxoSmithKline, Münchenbuchsee, Germany), remnant not rinsed. Debonding of brackets was performed using a universal testing machine. Data were analysed using one-way ANOVA and post-hoc Scheffé test.Group 4 performed significantly inferior than all the other groups and the control. Group 4 presented the highest number of adhesive failures at the enamel-resin interface whereas in other groups no failures at adhesive-resin interface was observed.Presence of chlorhexidine varnish prior to bracket bonding adversely affects adhesion. Concentration of chlorhexidine pre-treatment has no influence on shear bond strength.Standard caries prevention measures based on mechanical plaque removal, non-cariogenic dietary habits and regular fluoride supplementation are often insufficient to prevent new lesions in orthodontic patients [1]. Following the formation of a highly colonized cariogenic micro-flora, neither tooth brushing nor increased fluoride delivery is capable of effectively preventing the demineralization process [1,2]. Thus, the use of an antimicrobial agent to suppress cariogenic bacteria, and thereby to inhibit the development of new caries lesions, seems to be a rational approach during orthodontic treatment [3,4].Chlorhexidine (CHX) is the most potent documented antimicrobial against Mutans streptococci (MS), one of the most prono