Effect of changing enamel conditioner concentration on the shear bond strength of a resin-modified glass ionomer adhesive

The purpose of this study was to determine the effects on shear bond streng th of changing the concentration of the enamel conditioner used with resin- reinforced glass ionomer. Shear bond strength was measured within 30 minute s after bonding. Forty-six freshly extracted human molars were collected an d stored in a solution of 0.1% (weight/volume) thymol. The teeth were clean ed and polished, then randomly separated into 2 groups. In group I, enamel was conditioned with a 10% polyacrylic acid solution before bonding. In gro up II, the enamel was conditioned with a 20% polyacrylic acid solution. The results of t test comparisons of the 2 experimental groups (t = 4.9) indic ate significant differences (P=.001), Shear bond strength was significantly greater in the group conditioned with the 20% polyacrylic acid concentrati on ((x) over bar = 3.3 +/- 2.6 MPa) than in the group conditioned with the 10% concentration ((x) over bar = 0.4 +/- 1.0 MPa). The present findings in dicated that the lower initial shear bond strength of resin-reinforced glas s ionomer adhesive can be improved more than 8-fold when the concentration of the polyacrylic acid enamel conditioner is increased from 10% to 20%, Th e clinician needs to take these properties into consideration when ligating the initial archwires.