How Do Dentists Fill Cavities?

Last Editorial Review: 9/20/2017

Ask the experts

How do they fix cavities when you need fillings?

Doctor's response

Before a dentist can fill a cavity, it must be thoroughly cleaned by hand instruments and mechanical rotary instruments, called handpieces. The clean cavity is then filled with either dental amalgam, composite material, gold, or porcelain to restore the tooth to its original shape and size.

The most economical, time-honored material is the silver filling (also known as dental amalgam). It is composed of silver, tin, traces of metallic mercury, and other compounds. Dental amalgam has been used safely in dentistry for nearly 150 years. While some people have raised concerns over the health effect of mercury in the dental amalgam, the actual amount of metallic mercury in dental amalgam is less than the mercury found in seafood or polluted air. Swedish and American scientists could find no correlation between having new silver fillings and changes in the levels of mercury in the blood or urine. The American Dental Association still supports dental amalgam as a safe and effective filling material, especially for the cavities on the chewing surfaces of back teeth (bicuspids and molars). The amalgam can be a health problem if the patient has a true allergy to mercury (true allergy to mercury is rare, and the condition must be ascertained by a physician).

An alternative to amalgam is the use of composites. Composites are plastic resins mixed with quartz fillers or other hard minerals for strength. Composites are widely used to fill cavities in the front teeth because they come in various shades that match the natural tooth color. However they are less suitable for cavities in the back teeth because they are softer than amalgam and more prone to wear down and chip with chewing. If the composites are inadequately "cured" with the special composite light, leakage of bacteria and saliva can occur under the filling. Such leakage causes tooth sensitivity to cold and sweets. Leakage also causes the decay process to recur under and around the composite filling, causing subsequent fracture of the tooth.

Gold is an excellent material for filling teeth. It has good wear compatibility to the enamel of opposing and adjacent teeth. Gold adapts very well to the edges of a cavity and is totally inert or nontoxic. However gold is expensive, is unsightly in color, and is technically challenging to use. Therefore, gold fillings are rarely performed anymore.

A new filling material that is increasing in popularity is porcelain. Even though it is almost as expensive as gold, the color of porcelain filling can be matched to the natural tooth color. Two appointments are necessary to perform the porcelain filling. During the first appointment, the dentist cleans the cavity and takes an impression of the tooth. A dental laboratory then creates a stone model of the tooth and fabricates the porcelain filling from the tooth model. The porcelain filling is then cemented or "bonded" onto the tooth during a second appointment with the dentist.

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