Dental Fillings & Onlays

Fillings help restore teeth damaged by decay back to their normal function and can prevent further decay. Your dentist will consider several factors when choosing which filling material is best for you. These factors include the extent of the repair, where in your mouth the filling is needed, and the cost.

An onlay is an indirect restoration usually fabricated from either porcelain or gold and is cemented onto a tooth that requires cuspal replacement. A crown can be seen as an onlay that covers all the cusps.

Type of Dental Fillings:

Amalgam

• Made of: A mixture of silver, tin, zinc, copper and mercury. Mercury is nearly 50% of the mixture
• Types: Traditional (non-bonded)
• Used for: Fillings in back teeth
• Lasts: At least 10 years, usually longer
• Costs: The least expensive type of restorative material

Advantages

• Amalgam fillings are strong. They can withstand the forces of chewing.
• They are less costly than the alternatives.
• Amalgam fillings can be completed in one dental visit.
• They are less sensitive to moisture during the filling process than composite resin.

Disadvantages

• Amalgam doesn’t match the color of your teeth.
• Amalgam fillings can corrode or tarnish over time. This can cause discoloration where the filling meets the tooth.
• A traditional (non-bonded) amalgam filling does not bond (hold together) with your tooth.
• The cavity preparation (the “pocket” in your tooth) developed by your dentist requires undercuts or ledges to keep the filling in place. Your dentist may have to remove more of the tooth to create a secure pocket.
• Some people may be allergic to mercury or be concerned about its effects. Research shows that the amount of mercury exposure from fillings is similar to what people get from other sources in the environment.

Composite Resin 

• Made of: A mixture of plastic and fine glass particles.
• Types: Direct and indirect. Direct fillings are placed by your dentist using a bright blue light that hardens the soft material. For indirect fillings, your dentist prepares the tooth and takes an impression of it. A laboratory or the dentist then will make the filling from the mold. During a second visit, your dentist cements this filling into place.
• Used for: Small and large fillings, especially in front teeth or the visible parts of teeth; also for inlays
• Lasts: At least five years
• Costs: More than amalgam

Advantages

• Your fillings or inlay will match the color of your teeth.
• A filling can be completed in one dental visit. An inlay may require two visits.
• Composite fillings can bond directly to the tooth. This makes the tooth stronger than it would be with an amalgam filling.
• Less drilling is involved than with amalgam fillings. That’s because your dentist does not have to shape the space as much to hold the filling securely. The bonding process holds the composite resin in the tooth.
• Indirect composite fillings and inlays are heat-cured. This step increases their strength.
• Composite resin can be used in combination with other materials, such as glass ionomer, to provide the benefits of both materials.

Disadvantages

• Composite resins cost more than amalgam fillings.
• Although composite resins have become stronger and more resistant to wear, it’s not clear whether they last as long as amalgam fillings under the pressure of chewing.
• The composite may shrink when placed, producing gaps between the tooth and the filling. This can lead to more cavities in areas where the filling is not making good contact with your tooth. The shrinkage is reduced when your dentist places this type of filling in thin layers.
• These fillings take more time to place. That’s because they are usually placed in layers. The increased time and labor involved also contribute to the higher cost.
• Indirect fillings and inlays take at least two visits if your dentist is not prepared to make the inlay while you wait. Your dentist takes impressions on the first visit and places the filling or inlay on the second visit.