To obtain an adhesive composition of simple bonding operations capable of providing excellent adhesion to an aprismatic enamel constituting the outermost layer of the dentin and suppressing damage to the periphery of a treatment site, i.e., loss of glossiness, discoloration, fouling and induction, or the like, of dental caries on the dentin surface by excessive decalcification.

This adhesive composition comprises (a) an acidic group- containing polymerizable monomer, (b) water and (c) a water-soluble solvent. The adhesive composition may directly be applied to the aprismatic enamel surface and is an extremely simple one-step type adhesive composition.