A method of forming a dental composite includes photopolymerizing a dental composition. The dental composition includes a free-radically polymerizable (meth)acrylate resin, 75 percent by weight or greater of filler particles, and about 0.005 percent to about 5 percent by weight of at least one polymerizable stable radical. The photopolymerizing forms the dental composite such that the dental composite has a flexural modulus of about 9500 MPa or greater and the polymerizable stable radical reduces shrinkage stress of the dental composite caused by the photopolymerizing by 10% or greater. A method of forming a dental composite composition includes combining a free-radically polymerizable (meth)acrylate resin, 75 percent by weight or greater of filler particles, and about 0.005 percent to about 5 percent by weight of at least one polymerizable stable radical to form the dental composite composition.