Sealing and filling compositions for use in filling and/or sealing a root canal. The sealer and filler compositions include a polymerizable material that shrinks when polymerized. The composition also includes a gas releasing component that at least partially offsets the shrinkage caused by polymerization of the polymerizable material. The gas releasing component offsets polymerization shrinkage by creating tiny gas bubbles in the polymeric material, which causes expansion. The gas releasing component can be an acid and a base such as citric acid and sodium bicarbonate, which when mixed give off carbon dioxide. The composition can also include a dispersing agent to disperse the gas bubbles throughout the composition.