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Influence of modifying the resin coat application protocol on bond strength and microleakage of metal orthodontic brackets.

OBJECTIVE
To determine the shear bond strength (SBS) and microleakage of metal brackets bonded with two different adhesives when a resin coat and the adhesive were light-cured separately or simultaneously.


MATERIALS AND METHODS
Eighty stainless steel brackets were bonded to the enamel of extracted premolars, 40 with Transbond Plus adhesive (group 1) and 40 with Transbond XT (group 2). Each group was subdivided into four equal subgroups; a, b, c, and d. Brackets in subgroups a and b were bonded with the adhesive without coating. For brackets in subgroup c, Ortho-Choice Ortho-Coat was applied and cured after curing of the adhesive, while the coat was applied and cured with the adhesive for brackets in subgroup d. The specimens were immersed in a 2% methylene blue dye. After debonding, the teeth and brackets were examined with a stereomicroscope. The data were subjected to a two-way analysis of variance (ANOVA), Duncan multiple range test, and Pearson correlation.


RESULTS
Both adhesives had comparable SBS. Curing of the coat after curing of the adhesive showed significantly higher SBS than other protocols. There was no significant difference in SBS of the adhesives without coating and with curing of the coat and adhesive simultaneously. Application of the coat significantly reduced microleakage. There was a significant negative relationship between SBS and microleakage.


CONCLUSIONS
SBS was significantly improved with curing of the coat and adhesive separately, while it was not adversely affected when the coat and adhesive were cured simultaneously. Using the coat with either protocol significantly reduced the microleakage.