The transmission and attentuated total reflectance spectra of a dental cement formed from an aluminosilicate glass and aqueous polyacrylic acid (ASPA) are reported. Interpretation of spectra show that a siliceous hydrogel is formed together with the polyacrylate salts of calcium and aluminum. In the fully hardened cement a minor proportion of -COOH remains unconverted to -COO-groups for steric reasons. Chemical studies on the formation of the glass-ionomer cement, ASPA, show that the setting mechanism can be described as an acid-base interaction between an aluminosilicate body and polyacrylic acid.