The characteristics of resin matrices containing 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA) alternatives and spiro orthocarbonate (SOC) were examined to produce dental restorative composites exhibiting lower curing shrinkage and better mechanical strength than the commercially available dental composites. Bis-GMA alternatives were prepared by replacing the hydroxyl groups in Bis-GMA with alkoxy groups. Various SOCs that showed the expected volume expansion during the curing reaction caused by the ring opening reaction were added to Bis-GMA alternatives for a further decrease in curing shrinkage. The curing shrinkage of the dental composites containing Bis-GMA alternative and SOC was always lower than that of the dental composite used as the control, which contained 70 wt% Bis-GMA and 30 wt% triethylene glycol dimethacrylate (TEGDMA) as the resin matrix. Furthermore, the mechanical strength of the dental composites prepared from the 2,2-bis[4-(2-methoxy-3-methacryloyloxy propoxy)phenyl]propane (Bis-M-GMA) mixture containing approximately 10 wt% SOC was higher than that of the dental composite used as the control.