[Increasing the adhesion of glass ionomer cements in bracket bonding]

For attaching orthodontic brackets glass ionomer cements are being discussed as an alternative material to synthetic glues since they are less aggressive toward the tooth enamel. A serious disadvantage consists in a lower degree of adhesion to enamel. The adhesion can, however, be increased to some extent by enamel preparation. In order to investigate further improvement in this area, 250 freshly extracted bovine teeth were treated with 22 chemicals and their enamel-conditioning properties were tested. For the attachment of the brackets the glass ionomer cements AqaCem and Ketac-cem are used. Tensile shear tests were carried out with a Wolpert universal testing machine. Best results were obtained with the aromatic carbonacids benzoic acid and salicylic acid in acetonic solution. The mean adhesive power was 9.8 MPa. This means an increase of 38% as compared to other pre-conditioning materials such as polyacrylic acid. It can be assumed, that aromatic carbonacids as small, very reactive molecules can establish a closer contact to the phosphate groups of enamel than can the macromolecular polyacrylic acid. Thus, a further step on the way to using glass ionomer cements as a bracket bonding material seems to have been taken.