Types of Tooth Fillings

There are two main types of tooth fillings: metal and tooth colored. Metal fillings are usually an amalgam of mercury, silver, tin and copper. These are referred to as silver because of their color, not because silver is the main component. Some dentists also offer the option of gold alloy metal fillings (gold mixed with slightly harder metals such as copper). Tooth-colored fillings may be resin composite (a mix of acrylic and glass), glass or resin ionomers or porcelain. Metal amalgam and tooth-colored resin composite are currently the most popular filling materials.

Why Are There Different Types of Tooth Fillings?

Various tooth fillings have different attributes that make them suitable for different types of restoration. The desirable features of a tooth filling include:

• Cost efficiency of materials
• Ease of placement
• Durability of materials
• Placement without removal of too much healthy tooth tissue
• Biocompatibility (the materials don’t react with the body in an unwanted way)
• Natural appearance
• Resistance to corrosion and discoloration over time
• Whether the filling strengthens or weakens the tooth over the long term
• If the filling creates a good seal to keep out bacteria and food debris
• Minimal wear on opposing tooth
• Able to be used for restoration of chewing and biting surfaces

No one filling material meets all the criteria above. This means dentists and patients have to determine together which type of dental filling will provide the most satisfactory result based on the location of the tooth, the size and depth of the cavity and how much money the patient is willing or able to spend. Dental insurance often reimburses for fillings based on the assumption that the cheapest materials and least time consuming technique will be used (usually metal amalgam fillings). The patient is expected to pay for the difference in costs for more expensive materials or procedures. Here’s more information about each type of tooth filling your dentist may discuss during your consultation:

Metal Amalgam

Metal amalgam tooth fillings are known for being:

• The least costly filling material
• A material that all dentists are trained to install
• Able to withstand chewing forces (which makes it good for use in the molars)
• Durable, long-lasting and resistant to wear
• Seals well and tends to help prevent further decay in the treated area

On the other hand, its silver color is readily visible in the mouth and tends to become discolored to a less-attractive dark metallic color over time. Since the amalgam does not adhere to the tooth surface, a certain amount of healthy tooth structure must be removed. This is done to create a hole the right size and shape to wedge the metal amalgam into where it will be held tightly in place.

Are Amalgam Fillings Safe?

The most troubling concern regarding metal fillings is the presence of mercury (metal amalgams are often about 50 percent mercury mixed with other metals). Trace amounts of mercury vapor may be released from the amalgam over time depending on the size and number of fillings and the patient’s lifestyle habits such as tooth grinding. These tiny amounts of mercury may be ingested or inhaled over the lifetime of the filling. However, this is not the only source of environmental exposure to mercury for most people and has not been found to exceed limits that are considered safe.

Since mercury-based fillings have been used regularly in dentistry for more than 150 years, they are the best researched dental restoration material. At this time, the FDA, CDC and other public health agencies have found no reason to recommend restricting or discontinuing the use of mercury in dental fillings. At the same time, patients do have the option to request removal of mercury fillings and replacement with other materials if they are concerned about potential health risks.

Tooth-Colored Resin

This resin is usually a mix of acrylic (plastic) and silica (glass) that forms a soft composite material which can be hardened via exposure to a blue light laser lamp. The benefits of using resin include:

• Close match to the surrounding enamel, making the restoration look natural
• The material will not corrode over time
• Fairly strong and long lasting
• May be used in small to mid-sized cavities in the front or back teeth
• Like metal amalgam, can be placed in a single visit
• Allows preservation of more healthy tooth tissue
• May be placed after the cavity has been prepared with an air abrasion tool rather than a drill (some patients find this more comfortable)

Composite is more challenging to place since, like all tooth filling materials except amalgam, the treatment area must be kept completely dry during the procedure. Since the composite is applied and hardened (cured) in layers, it takes longer to install than an amalgam filling. Some patients find that resin may become stained over time. This material is not as strong or as long-lasting as metal amalgam and usually is not recommended for restoring larger cavities. It tends to work best for repairing areas where decay has not penetrated past the enamel. Composite is somewhat more expensive than amalgam.

Gold Alloy Tooth Fillings

Gold alloy is a very strong tooth filling material, but its texture makes it easy to mold to a perfect fit with the prepared cavity. This permits less removal of healthy tooth structure while enabling a tight seal to keep out food debris and discourage further decay. The metal tends to withstand pressure and chewing forces while not causing undue wear and tear on the opposing teeth. It is resistant to discoloration and will remain gold colored over time. Gold is the most costly dental filling material, and the fitting will take two visits to complete.

Tooth-Colored Ionomers (Polymers)

These come in a couple of different varieties, those that are mainly resin, and those that are mainly glass (each variety is still a mixture of resin and glass materials). These are tooth-colored restorations. They are not as strong as resin composite and are typically only used for small cavities on front teeth. Glass ionomers can be treated with fluoride that may reduce the chance of further decay. Ionomer fillings wear out faster than either composite or metal amalgam. These ionomer fillings may become loose, fracture, develop a rough surface or experience other problems that require replacement. They fall somewhere between metal and composite fillings in price.

Porcelain Inlays and Overlays

These are indirect fillings (they are custom fabricated in the lab based on a mold of the tooth and then placed in a separate visit). Porcelain is the most biocompatible filling material and is not known to cause any allergic reactions in patients. An inlay or onlay is usually recommended for repairing large cavities that are not quite large enough to justify a full crown. The material is generally long lasting and very durable and does not require removal of significant amounts of healthy tooth tissue. Porcelain fillings can be used in both front and back teeth for natural-looking restoration. Placement recommendations vary since the material may be hard enough to cause wear on opposing teeth. Certain biting forces may also cause cracking since the material is not as flexible as metal. Porcelain inlays and overlays are precisely color matched to the surrounding enamel.