BONDING STRENGTH OF GLASS IONOMERS TO DENSE SYNTHETIC HYDROXYAPATITE AND FLUOROAPATITE CERAMICS

The bonding strength of two glass ionomers, a resin-modified and a con ventional one, to dense synthetic hydroxyapatite (HA) and fluoroapatit e (FA) ceramics was compared by measuring the shear strength between t he ionomers and the apatites. Before the glass ionomers were applied o n the apatites, the surfaces of HA and FA plates were either fine-poli shed or acid-etched after fine polishing. Commercially pure titanium ( CP Ti) plates were used as a control. The effects of polyacrylic acid (PAA) surface preconditioning on bonding strength were also studied. T he results show that the ionomers bind to HA significantly more strong ly than to FA in all cases. The resin-modified material showed a signi ficantly higher shear strength to apatites than the conventional one. Acid etching increased the shear strength significantly For the conven tional glass ionomer to both HA and FA, and 25% PAA preconditioning in creased the shear strength significantly for the resin-modified glass ionomer to both HA and FA. It was concluded that glass ionomers seemed to bind to apatite chemically, and the bonding strength was influence d by the cohesive strength of the ionomers and the surface roughness o f the apatites. The dense synthetic apatites seemed to be good test ma terials for bonding evaluations of glass ionomers to mineral tissue.