Effect of a fluoridated etching gel on enamel morphology and shear bond strength of orthodontic brackets

The purpose of this study was to compare the enamel morphology and shear bond strengths of orthodontic brackets bonded to enamel etched with a fluoridated or a nonfluoridated phosphoric acid gel. Ten extracted third molars were used for the enamel morphology evaluation. The buccal surfaces were divided in two sections separated by an occlusogingival groove. One side was etched for 60 seconds with a 38% phosphoric acid gel, and the other side was etched with a 60% phosphoric acid gel containing 0.5% sodium fluoride. The specimens were then examined with a scanning electron microscope. For the shear bond strength tests, 30 extracted third molars were used. The buccal enamel surfaces of the mesial cusp were used, and the teeth were randomly divided into two groups of 15 teeth each--group 1, 38% phosphoric acid gel for 60 seconds; group 2, 60% phosphoric acid gel with 0.5% sodium fluoride for 60 seconds. Orthodontic lingual buttons were bonded to the etched surfaces with a composite resin. The results showed that the overall morphologic etching effect was similar in both groups. The mean shear bond strength for group 1 was 11.8 MPa +/- 4.2, and for group 2 it was 16.5 MPa +/- 5.1. This difference was statistically significant (p less than 0.01).