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In the third dental composition of the present invention, the sulfonic acid group-containing monomer (F) is not particularly limited, provided that it is a monomer having in one molecule at least one -S0$_{3}$H group or group which readily reacts with water as an essential component of the present invention to produce a -S0$_{3}$H group and at least one polymerizable unsaturated group. Known compounds can be used as component (F). 

Typical examples of the sulfonic acid group-containing monomer include (meth)acrylate derivatives and (meth) acrylamide derivatives of sulfonic acid represented by the following general formula (7), vinylsulfonic acid, styrene› sulfonic acid and the like. 

wherein R$_{1 }$ is hydrogen atom or a methyl group, R$_{3 }$ is an organic group having a valence of 2 to 6 and 1 to 30 carbon atoms, which may have an ether linkage and/or an ester linkage, Z is oxygen atom or an imino group (-NH-), n$_{1 }$ is an integer of 1 to 5, and n$_{3 }$ is 1 or 2. 

Preferred examples of the sulfonic acid group-containing monomer represented by the general formula (7) are as 30 follows. 

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A mixture of a plurality of the above sulfonic acid group-containing monomers can be used as required. 

The amount of the sulfonic acid group-containing mono- mer (F) in the present invention is preferably 0.01 to 12% by weight, more preferably 0.5 to 10% by weight, based on the total of all the constituent components. If the amount is below 0.01 % by weight, the effect of improving adhesive strength to enamel will be liable to be insufficient, and if the amount is above 12% by weight, adhesive strength to dentin will be liable to deteriorate. 

The sulfonic acid group-containing monomer may be mixed with the inorganic strong acid and/or the non- polymeric organic sulfonic acid illustrated as component (E). In this case, the total amount of the inorganic strong acid and/or the non-polymeric organic sulfonic acid is preferably 3% or less by weight, and the total amount of the inorganic strong acid and/or the non-polymeric organic sulfonic acid and the sulfonic acid group-containing monomer is prefer› ably 12% or less by weight. 

The inorganic strong acid and/or the non-polymeric organic sulfonic acid (E) of the second dental composition or the sulfonic acid group-containing monomer (F) of the third dental composition in the present invention need to be added in a state where at least one hydrogen cation can be supplied. When they are neutralized by a metal or amine and added as a neutral salt, they are not component (E) or component (F). Similarly, when a basic substance such as a hydroxide of a metal or an amine is added as an optional component and all or part of the acid is neutralized, the neutralized acid is not component (E) or component (F). 

In addition to the above components (A), (B), (C), (D), (E), (F) and (G), the dental composition of the present invention may contain a variety of optional components to be described later as far as they do not impair the effect of the present invention. In this case, the weight contents of the above components (A), (B), (C), (D), (E), (F) and (G) are based on 100% by weight of the total of these components (A), (B), (C), (D), (E), (F), (G) and other optional compo- nents. 

As described above, the composition of the present inven› tion may contain a monofunctional monomer, a water› insoluble organic solvent, a polymerization initiator, a metal salt, inorganic or organic fine particles and the like within limits not prejudicial to its performance. 

Illustrative examples of the monofunctional monomer include monofunctional monomers having no acid group, such as methyl methacrylate, ethyl methacrylate, tetrahy› drofurfuryl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxylethyl methacrylate, glycidyl methacrylate, N-methylol methacrylamide, diacetone methacrylamide and acrylates thereof; monocarboxylic acid group-containing monofunctional monomers such as acrylic acid, methacrylic acid, 2-(meth)acryloyloxyethyl hydrogen malate, 2-(meth) acryloyloxyethyl hydrogen succinate and N-(meth)acryloyl- 5-aminosalicy lie acid; and the like. 

Illustrative examples of the water-insoluble organic sol› vent include hexane, heptane, octane, toluene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, pentanone, hexanone, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate, vinyl acetate, diethyl ether and the like. 

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