Polymerization shrinkage by volume was overcome by adding:

Advantages of adding fillers: Reduces the coefficient of thermal expansion Reduces polymerization shrinkage Increases abrasion resistance Decreases water sorption Increases tensile and compressive strengths Increases fracture toughness Increases flexure modulus Provides radiopacity Improves handling properties Increases translucency Ref: Textbook of Operative Dentistry, Nisha and Amit Garg, 3rd edition, Pg no:253