Fillings are used to treat cavities, repair cracked or broken teeth, replace old, silver mercury fillings and teeth that have been worn down from misuse (such as from nail-biting or tooth grinding). Since they bond to the tooth, composite fillings restore most of the original strength of the tooth as well as its natural appearance. Composites fillings require less removal of tooth structure. Especially with new cavities, the size of the hole made for the filling can be dramatically smaller with composites. Teeth restored with white fillings are also less sensitive to hot and cold than teeth restored with amalgam.