Effect of altering the type of enamel conditioner on the shear bond strength of a resin-reinforced glass ionomer adhesive

The purpose of this study was to determine the effects of changing the type of enamel conditioner on the shear bond strength of a resin-reinforced gla ss ionomer within half an hour after bonding the bracket to the tooth. Fres hly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned and polished, The teeth were randomly separated into 4 groups according to the enamel conditioner/etcha nt and adhesive used: group I, teeth were conditioned with 10% polyacrylic acid and brackets were bonded with a resin-reinforced glass ionomer adhesiv e; group II, teeth were conditioned with 20% polyacrylic acid and brackets were bonded with a resin-reinforced glass ionomer adhesive; group ill, teet h were etched with 37% phosphoric acid and the brackets were bonded with a resin-reinforced glass ionomer adhesive; group IV, teeth were etched with 3 7% phosphoric acid and the brackets were bonded with a composite adhesive. The results of the analysis of variance comparing the 4 experimental groups (F = 24.87) indicated the presence of significant differences between the groups (P =.0001). In general, the shear bond strengths were significantly greater in the 2 groups etched with 37% phosphoric acid. This was true for both the resin-reinforced glass ionomer ((x) over bar = 6.1 +/- 2.7 MPa) an d the composite ((x) over bar = 5.2 +/- 2.9 MPa) adhesives. On the other ha nd, the shear bond strengths were significantly lower in the two groups con ditioned with polyacrylic acid, The bond strength of the resin-reinforced g lass ionomer adhesive conditioned with 10% polyacrylic acid ((x) over bar = 0.4 +/- 1.0 MPa) was significantly lower than the group conditioned with 2 0% polyacrylic acid ((x) over bar = 3.3 +/- 2.6 MPa). The present findings indicated that the bond strength of the resin-reinforced glass ionomer adhe sive can be significantly increased in the initial half hour after bonding if the enamel is etched with 37% phosphoric acid instead of being condition ed with either 10% or 20% polyacrylic acid. The clinician needs to take the se properties into consideration when ligating the initial archwires.