A dental composition comprising a polymerizable resin comprising ethylenically unsaturated groups; a thermally activated initiator dissolved in the resin; and an inorganic filler combined with the resin in an amount greater than about 60 percent by weight based upon the weight of the composition; wherein the initiator is activated at a temperature of about 100 to about 150° C. to provide free radicals; and wherein the filler has a surface area of at least about 65 square meters per gram filler; a dental mill block comprising the thermally cured composition, a method of manufacturing the dental mill block, and a kit comprising a plurality of the mill blocks are provided.