Enamel around orthodontic brackets coated with flash-free and conventional adhesives

To evaluate enamel roughness and color after debonding flash-free adhesive precoated brackets and brackets coated with conventional orthodontic adhesives using nonbonded enamel as control.

A total of 80 extracted human premolars were divided into the following four groups: group I: APC^TM Flash-Free adhesive precoated brackets; group II: APC^TM PLUS adhesive precoated brackets; group III: noncoated brackets, which were coated manually at the time of bonding (all three brackets were Clarity^TM Advanced ceramic brackets [3M Unitek, Monrovia, CA, USA]); group IV: nonbonded enamel (control). Bonded premolars were subjected to demineralization, and then brackets were debonded. Each group was then divided into two subgroups to assess enamel around the debonded brackets, and also enamel in the control group, using an atomic force microscope and spectrophotometer. In addition, 12 samples were used to assess the bracket/adhesive/enamel junction with a scanning electron microscope.

Mean values of root mean square roughness (Rq) and maximum profile valley depth (Rv) for APC^TM Flash-Free, APC^TM PLUS, and Clarity^TM Advanced groups were 140 nm and 482 nm, 210 nm and 727 nm, and 447 nm and 1243 nm, respectively. All three groups showed higher roughness and depth values than the control enamel. Spectrophotometer results yielded ∆E* of 3.7 ± 0.6, 5.1 ± 0.4, and 7.1 ± 0.6 for APC™ Flash-Free, APC™ PLUS, and Clarity^TM Advanced groups respectively. Color coordinates showed progressively higher L* and b* values and progressively lower a* values from group I to group III.

Under the same demineralization conditions, enamel around debonded APC™ Flash-Free adhesive precoated brackets showed less roughness and color changes compared to the other two groups.