The invention provides a radically polymerizable resin composition capable of suppressing shrinkage while maintaining strength by adding an appropriate amount of an expansive additive to the radically polymerizable resin composition causing curing shrinkage by a decrease in the free volume of a liquid component during curing. The radically polymerizable resin composition comprises a radically polymerizable compound (A), an expansive additive (B), a radical polymerization initiator (C), and an aggregate (D). The aggregate (D) contains cement. The aggregate (D) is 330 to 800 parts by mass with respect to 100 parts by mass of the radically polymerizable compound (A).

A modified polyester-based elastomer obtained by modifying a polyester polyether block copolymer consisting of a hard segment containing an aromatic polyester and a soft segment containing a polyalkylene ether glycol with an unsaturated carboxylic acid and/or a derivative thereof, wherein the modified polyester-based elastomer contains titanium and has a titanium content of less than 250 wt ppm.