Dental restorative compositions having improved mechanical properties and hydrolytic stability

Claim 1

A dental restorative composition consisting essentially of: (a) a polymerizable composition containing at least one compound having at least two olefinically unsaturated groups, wherein, when said polymerizable composition is polymerized in the unfilled state, the resulting cured material has a water absorption as determined by ADA Specification No. 27 at 37° C. for one week, of less than 1 milligram per square centimeter; (b) a polymerization initator for said polymerizable composition; and (c) a hydrophobic inorganic filler having a volume average particle size below 15 microns, at least 30 percent of the particles of said filler having a size of less than 5 microns, said filler being present in an amount within the range of from about 35 to about 70 volume percent, based on weight of said polymerizable composition plus said filler, and said filler being selected from the group consisting of quartz and acid-washed and heat treated barium or strontium glass, wherein the heat treatment is carried out at a temperature below the sintering temperature of the glass, and at a temperature and for a period of time sufficient to effect at least a 50 percent reduction in the specific surface area of the glass.