The effect of bleaching on shear bond strength of brackets bonded with a resin-modified glass ionomer

Introduction: This study assessed the effect of a 35% hydrogen peroxide bleaching gel on the shear bond strength and bond failure site of a resin-modified glass ionomer (Fuji Ortho LC, GC Europe, Leuven, Belgium). Methods: Forty-five bovine mandibular permanent incisors were randomly divided into 3 groups; each group contained 15 teeth. Bleaching treatment was performed at 2 different times before the bonding procedure. Forty-five stainless steel brackets were bonded with the resin-modified glass ionomer. After bonding, all samples were stored in distilled water for 24 hours and then tested in shear mode on a testing machine. Results: Group 1 (no bleaching) showed significantly higher shear bond strength values than groups 2 (bleaching immediately before bonding) and 3 (bleaching 1 week before bonding). No significant differences were found between groups 2 and 3. Moreover, no significant differences in debond locations were found among the 3 groups. Conclusions: Bleaching treatment before bonding significantly lowered the bond strength values of Fuji Ortho LC.