Composite fillings, also known as white fillings, are more than just aesthetically better matched to the tooth, they have the distinct advantages over metal fillings as they are environmentally non toxic, as no mercury is used.
They bonded directly to the surface of the tooth thus protecting the tooth from fracturing as they do not require the removal of healthy tooth structure, as with mercury fillings.
General Definition: A dental filling is a dental restorative material used to restore the function, integrity and shape of missing tooth structure. The structural loss typically results from decay or external trauma. It is also lost intentionally during tooth preparation to improve the aesthetics or the physical integrity of the intended restorative material.