In-vitro evaluation of microleakage under orthodontic brackets bonded with various adhesive systems

The aim is to evaluate the microleakage under orthodontic brackets bonded with three adhesive systems, different surface preparations, and two light curing units. 144 extracted bovine incisors were divided randomly into twelve groups. Six of these groups were preconditioned with air abrasion. Three adhesives were used to bond the brackets to enamel: 37% phosphoric acid+Transbond XT Primer+Transbond XT Adhesive, Transbond Plus Self-Etching Primer+Transbond XT Adhesive and 37% phosphoric acid+GC Ortho Connect. Elipar S10 Curing Light and Valo Ortho Curing Light were used to polymerize the adhesives. The specimens were stained with 0.5% basic fuchsine solution, sectioned buccolingually and evaluated under microscope (20x magnification) at enamel-adhesive and bracket-adhesive interfaces from gingival and incisal margins. Microleakage was observed in all groups. There was no significant difference between microleakage scores of gingival and incisal margins (p>0.05). When air abrasion was applied, the type of adhesive did not have a significant effect on microleakage. When enamel was not preconditioned with air abrasion, GC Ortho Connect showed more microleakage in enamel-adhesive (p=0.004) and bracket-adhesive interfaces (p=0.0001). Air abrasion caused more microleakage when brackets were bonded with Transbond XT Primer (p<0.05) and Transbond Plus Self-Etching Primer (p=0.0001). Valo Ortho Curing Light caused more microleakage when Transbond XT Primer was used without air abrasion preconditioning (p=0.0001). Regardless of the curing unit, adhesive type does not have a significant effect on microleakage, when air abrasion preconditioning. When the enamel is not preconditioned with air abrasion, one step adhesive system causes more microleakage than the conventional and self-etching adhesive systems. Keywords: microleakage, orthodontics, brackets, self-etching, one step adhesive, air abrasion