Dental filling material

Different filling materials

There are a number of different fillings, including:

• Amalgam (silver coloured).
• Composite fillings (tooth coloured).
• Glass ionomer (tooth coloured).
• Gold inlays and onlays (gold coloured).
• Porcelain inlays (tooth coloured).

What are amalgam fillings?

Dental amalgam is a dental filling material used to fill cavities caused by tooth decay. It has been used for more than 150 years in hundreds of millions of patients around the world.

Dental amalgam is a mixture of metals, consisting of liquid (elemental) mercury and a powdered alloy composed of silver, tin, and copper. Approximately 50% of dental amalgam is elemental mercury by weight.  The chemical properties of elemental mercury allow it to react with and bind together the silver/copper/tin alloy particles to form an amalgam.

Dental amalgam fillings are also known as “silver fillings” because of their silver-like appearance.  Despite the name, "silver fillings" do contain elemental mercury.

When placing dental amalgam, the dentist first drills the tooth to remove the decay and then shapes the tooth cavity for placement of the amalgam filling. Next, under appropriate safety conditions, the dentist mixes the powdered alloy with the liquid mercury to form an amalgam putty. (These components are provided to the dentist in a capsule as shown in the graphic.) This softened amalgam putty is placed and shaped in the prepared cavity, where it rapidly hardens into a solid filling.

What should I know before getting a dental amalgam filling?

Deciding what filling material to use to treat dental decay is a choice that must be made by you and your dentist.

FDA continues to evaluate the available information on dental amalgam, and will update the information on this web page as necessary. As you consider your options, you should keep in mind the following information.

Benefits:

Dental amalgam fillings are strong and long-lasting, so they are less likely to break than some other types of fillings.

Dental amalgam is the least expensive type of filling material.

Potential Risks:

Dental amalgam contains elemental mercury. It releases low levels of mercury in the form of a vapor that can be inhaled and absorbed by the lungs. High levels of mercury vapor exposure are associated with adverse effects in the brain and the kidneys.

FDA has reviewed the best available scientific evidence to determine whether the low levels of mercury vapor associated with dental amalgam fillings are a cause for concern. Based on this evidence, FDA considers dental amalgam fillings safe for adults and children ages 6 and above.   The weight of credible scientific evidence reviewed by FDA does not establish an association between dental amalgam use and adverse health effects in the general population.  Clinical studies in adults and children ages 6 and above have found no link between dental amalgam fillings and health problems.

What are composite fillings?

Dental composite resins (better referred to as "resin-based composites" or simply "filled resins") are types of synthetic resins that are used in dentistry as restorative material or adhesives. Dental composite resins have certain properties that will benefit patients according to the patient's cavity. It has a micro-mechanic property that makes composite more effective for filling small cavities where amalgam fillings are not as effective and could therefore fall out (due to the macro-mechanic property of amalgam). Synthetic resins evolved as restorative materials since they were insoluble, of good tooth-like appearance, insensitive to dehydration, easy to manipulate and reasonably inexpensive. Composite resins are most commonly composed of Bis-GMA and other dimethacrylate monomers (TEGMA, UDMA, HDDMA), a filler material such as silica and in most current applications, a photoinitiator. Dimethylglyoxime is also commonly added to achieve certain physical properties such as flow-ability. Further tailoring of physical properties is achieved by formulating unique concentrations of each constituent.

Many studies have compared the longevity of resin-based composite restorations to the longevity of silver-mercury amalgam restorations. Depending on the skill of the dentist, patient characteristics and the type and location of damage, composite restorations can have similar longevity to amalgam restorations. (See Longevity and clinical performance.) In comparison to amalgam, the appearance of resin-based composite restorations is far superior.

 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 to complete if your dentist is not prepared to make the inlay while you wait. Your dentist takes impressions at the first visit and places the filling or inlay at the second visit.

What are glass ionomer fillings?

Glass ionomer cements (GICs) can have a range of compositions, but the chief constituents are alumina, silica, and calcium. A source of fluoride, such as fluorite, is also usually incorporated to offer protection against tooth decay. More minerals can also be added into the GIC to boost demineralization and/or prevent acidification. The glass ionomer may be incorporated with resin for extra strength as well as to reduce the sensitivity level to the presence of moisture on placement. GICs signify an extremely very flexible dental restoration solution as the physical properties of GIC can be altered to match a particular dental application by modifying the ratios of the constituent chemicals^.

Similar to resin composites, GICs are tooth-colored and therefore possess cosmetic appeal. The key benefit of GICs is their chemical bonding to dentin and enamel, which enhances the strength of the restoration and eliminates the need for a bonding agent during placement.The bond strength of this adhesion is usually increased by incorporation of polycarboxylic acid. GICs have been known to display a contact-free area wear that is five times greater than that of amalgam and three times greater than for resin composite materials. Moreover, in contrast to other restoration materials that can unexpectedly fail because of mechanical fatigue, GICs become stronger over time as water is absorbed and are therefore less susceptible to failure.

Lately, bioactive glass is used for making GIC. Resin-modified GIC comprising of bioactive glass has been demonstrated to result in a thick uniform layer of mineralization on the restoration-dentin interface, enhance the mechanical properties of a filling, and reduce the incidence of secondary tooth decay at restoration margins.

 What are gold inlays and onlays?

Gold fillings, also called inlays or onlays, are composed of an alloy of gold, copper and other metals.

This type of dental filling is usually considered the most durable, lasting 20 years or more, but it is also the most costly. Gold fillings also require more than one office visit to place because they require impressions to manufacture at a dental laboratory.

Direct placement of gold is a restoration called a gold foil. These types of dental restorations are infrequently performed and are usually used for small fillings. Gold foils can be placed in one visit, just like an amalgam or composite filling.

Ultimately, the best dental filling is no dental filling. Prevention is the best medicine. You can dramatically decrease your risk of cavities and other dental diseases simply by:

• brushing your teeth twice a day with fluoride toothpaste
• flossing daily
• eating a balanced diet
• visiting the dentist regularly.

What are porcelain inlays?
An porcelain inlay or onlay restoration is a custom made filling.  Porcelain inlays are popular because they resemble your natural tooth.  A porcelain inlay is made by a professional dental laboratory and is permanently cemented into the tooth by your dentist.

Inlays & Onlays can be utilized to conservatively repair teeth that have large defective fillings or have been damaged by decay or trauma.  Inlays are an ideal alternative to conventional silver and composite fillings because they are esthetic, last longer and their bond resotres strength to the tooth.  Also, they are more conservative than crowns because less tooth structure is removed in the preparation of inlays & onlays.

As with most dental restorations, inlays are not always permanent and may someday require replacement.  They are highly durable and will last many years, giving you a beautiful long lasting smile.