Abstract: The present invention relates to a composite material exhibiting a low or even negligible volumetric shrinkage upon curing, or even a small expansion (e.g. up to 0.5%), in particular composite materials in the form of dental filling materials. The present invention also relates to a method of controlling volumetric shrinkage of a composite material upon curing, and to a method of reconstructing a tooth. The present invention also relates to ultrasonic curing of dental filling materials. The present invention further relates to a population of zirconia particles and methods for preparing such zirconia particles (e.g. zirconia in the tetragonal phase or zirconia in the cubic phase). The martensitic transformation of the filler ingredients is, e.g., triggered by application of ultrasound or by a chemical trigger.