A dental filling is a type of restorative dentistry treatment used to repair minimal tooth fractures, tooth decay or otherwise damaged surfaces of the teeth. Dental filling materials, which include composite, porcelain and silver amalgam, may be used to even out tooth surfaces for better biting or chewing.
Enamel loss is a common component of tooth decay, and may result in tooth sensitivity. In many cases, tooth sensitivity caused by enamel loss will be significantly improved or completely eliminated once an appropriate dental filling material is placed.
Why we use tooth-colored-composite fillings over traditional amalgam fillings? We use composite fillings over amalgam for a few different reasons. One main reason, amalgam does contain mercury, but NOT to be worried, the amount of mercury is harmless to the body. After the other chemicals that the amalgam contains are mixed with the mercury; the amount is weakened tremendously. Secondly, amalgam is metal and a dark gray color. Although this has been used for years and years, we prefer to provide our patients with a tooth colored material that matches the color of their own teeth. This, in fact, helps to blend the filling into the tooth so it not noticeable.
(Obtained from consumer guide to dentistry: http://www.yourdentistryguide.com)