One of the most common pieces of news a dentist gives a patient upon examination is that they have a cavity. In fact, 90 percent of American adults get cavities. In 2005 alone, over 180 million cavities were filled. The good news is, today, cavities can be filled more quickly and painlessly than ever before.

Cavities are caused by plaque. Plaque causes decay and decay creates a hole in the tooth, which explains why they are called cavities. Whether the decay is new or buried under an old restoration, it needs to be removed, which, as you probably know, is done with a dentist's drill. The most common sites for decay occur in the contact area, in the deep grooves of the tooth or near the gum line or the root. If it's near the root, the dentist may first put in a liner of glass ionomer, composite resin or other material to protect the nerve. If necessary, you may also be given an anesthetic.

Once the decay's been cleaned out of a cavity, the dentist evaluates how much of the tooth is left, and that determines what kind of restoration he'll put in there. The type of restoration used also depends on its location. For example, if it's in the aesthetic zone (the most visible front part of the smile), it needs to look natural and blend in. If it's in the back of the mouth, it needs to be strong and durable.

Teeth can be filled with either porcelain, gold or silver amalgam (which consists of mercury mixed with silver, tin, zinc and copper), although with all the great resin filling materials available, there really is no need to go silver anymore. A filling is the smallest of the restorations, called a direct restorative because once the decay is cleaned out, the restorative is fit directly to the teeth.


  • Gold fillings are the Teflon of the filling family, but for all their power, they're equally garish. If the tooth is way in the back of the mouth, say, within a molar, where it will be well concealed, a gold filling will sustain the hard work it endures and its color won't offend.

When to go for the gold:

  • When the filling is in the back of the mouth, so you can't really see it.
  • When the tooth requires durability. Gold lasts at least 10 to 15 years and doesn't corrode.
  • Downsides of gold:
  • It's more expensive than other materials, up to ten times higher than the cost of an amalgam.
  • Many patients don't like the look of gold in their mouths.
  • Its placement requires at least two office visits.
  • Galvanic shock: The ADA notes that if a gold filling is placed directly next to a silver amalgam, it can cause a sharp pain, called galvanic shock. While this is a rare occurrence, the interaction between the two metals and saliva can cause an electric current to occur.
  • Silver amalgam
  • Silver amalgams consist of mercury mixed with silver, tin, zinc, and copper. It should be noted that silver amalgams are being used less and less because of the advancements in the arena of resin. With the many resin filling materials available, silver has become increasingly outdated.

The advantages of silver amalgam:

  • It's nearly as durable as gold.
  • It can withstand chewing forces.
  • It's less expensive than both gold and composite fillings.
  • Downsides of silver:
  • Many patients don't like the look of silver in their mouths.
  • Sometimes healthy parts of the tooth need to be removed to make room for the amalgam filling.
  • It has the potential to crack and fracture more than other filling materials.
  • A very small percentage of people (1 percent) are allergic to the mercury present in amalgam restorations. The reaction is typically similar to a mild skin rash.
  • Mercury

A thing of the past or an old standby?
Growing up, most of us who had cavities had them filled with amalgams made of silver, tin, mercury, and some other trace elements like copper. While their aluminum-foil like appearance wasn't the most attractive, they were durable (many last up to 20 years). Today, even though more attractive tooth-colored composite resins are available (and used by many dentists), the standard amalgam is what most practices still fill cavities with.

Theories of mercury leaking from cavities causing toxicity resulting in certain autoimmune diseases have spread far and wide in the dental world. But while high levels of mercury found in certain seafood have altered people's menu selections, its appearance in fillings is far less volatile. Although mercury by itself is classified as a toxic material, the mercury in an amalgam is chemically bound to other metals to make it stable and therefore safe for use in dental applications. In fact, amalgam is the most thoroughly studied and tested restorative material now used. The safety and effectiveness of amalgams have been reviewed by major U.S. and international scientific and health bodies, including the American Dental Association; the National Institutes of Health, the U.S. Public Health Service, the Centers for Disease Control and Prevention, the Food and Drug Administration, and the World Health Organization. All have concluded that amalgam is a safe and effective material for restoring teeth.

Composites are by far the most subtle restorations. Composites are made of a material called bis-gma resin, which includes a type of glass filler particle in a resin base. A composite is sculpted either into a cavity or onto a tooth; it's then cured with a light and shaped in. The procedure is also known as bonding or a bonded restoration. When the decay is minor, a composite is an excellent choice.

The upside of a tooth-colored composite:

  • A composite is a good choice when the decay is minor. Since it's contained within a tooth (as opposed to taking over an entire side or section of a tooth), it doesn't encounter much force.
  • Its color blends in with your other teeth. But, bear in mind that it's operator-sensitive; how good it looks depends on how good the dentist is who's placing it.
  • It's kinder to the soft tissue then gold or silver amalgams.
  • Unlike other fillings, composites actually chemically bond to your tooth structure, giving further support to your tooth.
  • Less removal of the tooth's structure is required with composite fillings.

The downsides of composites:

  • They don't last as long as the other options (five to ten years, usually), and can't withstand as much chewing force as the other options. However, as technology continues to improve, composites are getting better and stronger.
  • Depending on their location, the composite materials can chip off.
  • They can cost up to twice as much as silver amalgams. (Most dental insurance covers the cost of composites up to the price of the silver filling; then the patient must pay the difference.)