A tooth with a filling in it will likely have a dull surface and be less sensitive to hot and cold. A filling is a substance that is placed in the cavity to restore the original shape of the tooth. It can also provide a protective barrier from other cavities in the future. Dental Fillings NYC are materials used to fill in cavities in teeth. They can be made of a variety of materials, including metals, ceramics, glass, and composites. Dental fillings can also be classified by the type of material used. It is always a good idea to have a dental filling replaced every six months, and most dentists recommend getting one every year.