Composite (White) vs. Amalgam (Silver) Fillings
The main decision that a patient will need to make at their filling appointment (or during the treatment planning) is their choice in filling material. The two main classes of fillings are composite resin and amalgam metallic alloy. These two filling types are often referred to by patients and doctors as "white" and "silver" fillings because of their color.
The recommendation most doctors will make is for the placement of a composite filling. Composite fillings have a 40 year history and are comprised of a plastic resin that is initially soft but cures to full strength after a short exposure to the blue range of the light spectrum. Composite fillings are bonded or "glued" in place to the tooth on a microscopic level. The pros to using composite fillings are that they can be very small in size and adapt to any shape of cavity, come in a wide variety of colors to match your smile, and have no chance of darkening a tooth over time.
Amalgam alloy fillings are comprised of a mixture of copper, silver, tin and elemental (safe) mercury. They have a 100 year history of use. Amalgam fillings are held in place by the shape of the cavity. One major drawback of an amalgam filling is that if the cavity is too small the filling still has to be of sufficient size for proper hold and overall strength. The minimum size requirement of amalgam fillings limits the doctor when attempting to preserve natural tooth structure. Besides only coming in one color, the silver in amalgam fillings has the tendency to tarnish and percolate into the tooth over long periods of time, resulting in a gradual darkening of the tooth.
Composite fillings are not without their shortcomings however. During the bonding procedure where the doctor is placing the filling, the tooth needs to be kept as dry as possible. Any water introduced will retard the gluing of the filling into place and reduce the overall longevity of the filling. In certain circumstances, such as bleeding gums or hard to reach locations, if a filling cannot be kept dry enough, then an amalgam filling is a better, longer lasting choice.
Composite (plastic) fillings are also softer in nature than amalgam (metal) fillings. Because of this they tend to wear down faster in those who grind their teeth. Composite fillings also need to be kept clean and require regular brushing and flossing, otherwise they tend to develop a new cavity along their edges. Amalgam fillings are more forgiving in this aspect. If a cavity starts to form along its edge the silver tarnishes and helps seal out the bacteria, making it harder for the bacteria to dig deeper. However amalgam fillings will still experience recurrent cavities if not cared for properly as well.