An in vitro evaluation of bond strength of three glass ionomer cements.

The purpose of this study was to determine the bond strength of three commercially available glass ionomer cements when used to bond mesh-backed medium twin (0.130 inch) brackets to enamel surface. Three different enamel surface conditions, which included use of pumice, pumice and polyacrylic acid, and pumice followed by acidulated phosphate fluoride, were also tested to determine their effect on the bond strength. In addition, bond strength of one composite resin was compared with those of glass ionomer cements. The teeth were bonded with all the materials according to manufacturers' instructions. Each specimen was embedded in Super-Die with the bonded facial surface exposed. A surveyor was used to align the teeth in the stone uniformly for all specimens. A special bracket holder was used to hold the brackets precisely under the wings during debonding. An Instron universal testing machine was used to measure the force required for bond failure. To stimulate oral conditions, the direction of pull was so designed that it included an element of torsional stress along with tensile force. The findings indicate that a large variation existed between the bond strengths of all materials tested. The bond strength of glass ionomer cements was significantly less than that composite resin. However, the bond strength of at least one glass ionomer cement appears to be adequate for clinical use. The different surface preparation before bonding did not significantly affect the bond strengths of glass ionomer cements. Further investigation is required to test the bond strengths of glass ionomer cements clinically.