A dental restoration or dental filling is a treatment to restore the function, integrity, and morphology of missing tooth structure resulting from caries or external trauma. A restoration can be direct and indirect and it is classified by location and size. A root canal filling, for example, is a restorative technique used to fill the space where the dental pulp normally resides.

Tooth decay is damage to a tooth that can happen when harmful bacteria in your mouth make acids that attack the tooth enamel. This can lead to a small hole in a tooth, called a cavity. More severe decay can cause a large hole or even destruction of the entire tooth. If tooth decay is not treated, it can cause pain, infection, and even tooth loss.

When a tooth is exposed to acid frequently—for example, if you eat or drink often, especially foods or drinks containing sugar and starches—the repeated cycles of acid attacks cause the enamel to continue to lose minerals. A white spot may appear where minerals have been lost. This is a sign of early decay.

Tooth decay can be stopped or reversed at this point. Enamel can repair itself by using minerals from saliva and fluoride from toothpaste or other sources. But if the tooth decay process continues, more minerals are lost. Over time, the enamel is weakened and destroyed, forming a cavity.

Restoring a tooth to good form and function requires two steps: (1) preparing the tooth for placement of restorative material or materials, and (2) placement of these materials. The process of preparation usually involves removing the decayed material from the tooth with a rotary dental handpiece and dental burrs. If permanent restoration cannot be carried out immediately after tooth preparation, temporary restoration may be performed.

A number of considerations will determine the type and extent of the preparation. The most important factor to consider is decay. The extent of the decay greatly influences the extent of the preparation, and in turn, the subsequent method and appropriate materials for restoration. Another consideration is unsupported tooth structure. When preparing the tooth to receive a restoration, unsupported enamel is removed to allow for a more predictable restoration. While enamel is the hardest substance in the human body, it is particularly brittle, and unsupported enamel fractures easily.

This technique involves placing a soft or malleable filling into the prepared tooth and building up the tooth. The materials used are most commonly gold, amalgam, dental composites, glass ionomer cement, or porcelain. The material is then set hard and the tooth is restored. The advantage of direct restorations is that they usually set quickly and can be placed in a single procedure. The decision of which material to use is usually made based on the location and severity of the cavity.

In this technique the restoration is fabricated outside of the mouth using dental impressions of the prepared tooth. Common indirect restorations include inlays and onlays, crowns, bridges, and veneers. Usually a dental technician fabricates the indirect restoration from records the dentist has provided. The most commonly used materials are gold and ceramics. The finished restoration is bonded permanently with a dental cement. The treatment is often done in at least two separate visits to the dentist because time is needed for the fabrication of the restoration after the impression is obtained. While the indirect restoration is being prepared, a temporary restoration is used to cover the prepared tooth and allow the patient to bite. This usually consists of a softer dental cement that can easily be removed with the dental drill.

Removable dental prostheses (mainly dentures) are a form of indirect dental restoration, as they are made to replace missing teeth. There are numerous types of precision attachments (also known as combined restorations) to aid removable prosthetic attachment to teeth, including magnets, clips, hooks, and implants which may themselves be seen as a form of dental restoration.

Casting alloys are mostly used for making crowns, bridges and dentures. Titanium, usually commercially pure but sometimes a 90% alloy, is used as the anchor for dental implants as it is biocompatible and can integrate into bone.

Metals and alloys

• gold (high purity: 99.7%) and gold alloys (with high gold content)
• gold-platinum alloy
• silver alloy
• cobalt-chrome alloy
• nickel-chrome alloy
• Amalgam: 65% Silver, 29% Tin, 6% Copper, 2% Zinc, 3% Mercury

Dental Amalgam is widely used because it is easily made into rigid direct fillings, completed in single appointment, with acceptable strength, hardness, corrosion, and toxicity properties. Its preparation is more forgiving than that of composite resins. Amalgam is now mainly used for posterior teeth (less visible) because of its gray color. Although the mercury in cured amalgam is not available as free mercury, concern about its toxicity has existed since its invention as a dental material. It is banned or restricted in Norway, Sweden and Finland.

Composite resin

Dental composites, also called "white fillings", are a group of restorative materials used in dentistry. In addition to fillings done at the clinic, composite resins are also used to manufacture crowns and in-lays in the laboratory. The greatest advantage of these materials is that they can be made tooth-colored. Their strength and durability is not as high as porcelain or metal restorations and they are more prone to wear and discoloration. Compositions vary widely, with proprietary mixes of resins forming the matrix, as well as engineered filler glasses and glass ceramics.

An initiator substance begins the polymerization reaction of the resin when light is applied at a specific wavelength (460-480 nm blue light) to yield necessary free radicals and start the process. This process is quick and safe, but it require the composites to be applied in thin layers as determined by their opacity. Immediately after light induced curing, the final surface can be be shaped and polished.

Glass ionomer cement

A glass ionomer cement (GIC) is one of a class of materials commonly used in dentistry as filling materials and luting cements. These materials are based on the reaction of silicate glass powder and polyalkenoic acid. These materials can also have the color of the tooth and they were used to restore anterior teeth before composite resins were developed.

As they bond chemically to dental hard tissues and release fluoride for a relatively long period, modern-day applications of GICs have expanded. The desirable properties of glass ionomer cements make them useful in restorations at low-stress areas on primary teeth. They do not need to be applied layer by layer, like in composite fillings.

Porcelain (ceramics)

Various types of dental porcelain (ceramic fired at high temperatures) are used in indirect fillings and crowns. They are also used as in-lays, on-lays, and aesthetic veneers. A veneer is a very thin shell of porcelain that can replace or cover part of the enamel of the tooth. Full-porcelain restorations are particularly desirable because their color and translucency mimic natural tooth enamel. Porcelain can be combined with metal to provide strength to a crown or bridge. These restorations are more durable than porcelain used alone.

Comparison of filling materials

• Composites and amalgam are used mainly for direct restoration. Amalgam is more durable but composites can be made to match the color of the tooth and the surface of the restoration can be polished after the procedure has been completed.
• Amalgam fillings expand with age, possibly cracking the tooth and requiring filling replacement.
• Composite fillings shrink with age and become prone to infiltration. If not noticed early, this results in new decay.
• Fillings are recommended for small to medium size restorations.
• Inlays and onlays are more expensive indirect restoration alternatives to direct fillings. They should be more durable than composite direct fillings, however.
• Porcelain, cobalt-chrome, and gold are used for indirect restorations like crowns and partial coverage crowns (onlays). Traditional porcelains are brittle and are not always recommended for molar restorations.

What Is Dental Amalgam?

Dental amalgam, sometimes called a “silver-filling” due to its appearance, is a mixture of mercury, silver, copper, tin and zinc used to fill cavities in teeth. Dental amalgam is approximately half (50%) mercury, by weight.

Is Dental Amalgam Safe?

Dental amalgam fillings may release small amounts of mercury in the form of a vapor (gas), depending on the number and age of existing fillings, and actions such as tooth grinding and gum chewing. When a new amalgam filling is placed or an old filling is removed, patients and healthcare providers may experience a temporary increase in exposure to mercury vapor. While there are no known health risks associated with ingestion (swallowing) of small particles of dental amalgam, inhaling (breathing in) mercury vapors may be harmful in certain patients.

In general, people with multiple dental amalgam fillings may have slightly higher mercury levels in their blood or urine, however, they usually remain at a level considered safe. Studies on people with dental amalgam do not show conclusive evidence that dental amalgam causes harmful health effects in the general population.

Who Should Be Concerned About Dental Amalgam?

Certain people, including women who are pregnant or who are planning to become pregnant, nursing mothers, children (especially those under the age of six), people with a known allergy to mercury, and people with neurological impairment or kidney dysfunction, may be more susceptible to the effects of exposure to mercury from dental amalgam and may be at greater risk for adverse health effects. Little information is known about the potential health effects of mercury vapor exposure from dental amalgam on these groups of people. As such, if you are a person who is in one of the high-risk populations identified and need a new filling, the FDA recommends you avoid dental amalgam if possible and appropriate. Talk to your dental provider about your health history and other available treatment options for fillings.

• Women who are pregnant or planning to become pregnant. Placement of new amalgam fillings in a pregnant mother may result in high, transient spikes of mercury exposure to the mother and fetus. Some studies have shown a relationship between the number of amalgam fillings a mother has and mercury levels in umbilical cord blood. Results from these studies did not identify any certain associations with harmful health effects; however, the data is very limited.
• Nursing mothers. The amount of mercury in breast milk is typically very low. Some studies have reported a relationship between the number of amalgam fillings a mother has and the amount of mercury in breast milk. The very few, limited studies that have been conducted to evaluate possible harm to infants and children exposed to dental amalgam mercury as a result of breast-feeding did not identify any definite associations with harmful health effects.
• Children, especially those under the age of six. Clinical studies in children ages six and older have not found a definite connection between the use of dental amalgam and harmful health effects. Studies on children under the age of six are very limited. The developing neurological systems of children may be especially sensitive to exposure to mercury vapor.
• People who are more sensitive to mercury or other components of dental amalgam. Some people may have an allergy or sensitivity to mercury or other components (e.g., silver, copper, tin or zinc) of dental amalgam and may report or experience health effects, including allergic reactions and oral ulcers, as well as more generalized symptoms, after placement of an amalgam filling.
• People with neurological impairment or kidney dysfunction. Studies show mercury is localized in certain tissues of the body including the brain and kidneys. Very limited clinical information is available about possible health effects of mercury vapor exposure on individuals who already have kidney and/or neurological impairments.

Although a direct correlation between mercury from amalgam and possible harmful health effects has not been established, and there may be cumulative effects from exposure to mercury from other sources such as the environment or diet, some signs or symptoms of excessive mercury in the body may include:

• Mood disorders (for example, anxiety, depression, irritability)
• Sleep troubles or disturbances
• Fatigue (feeling tired)
• Memory troubles or disturbances
• Tremors (shaking)
• Difficulties with coordination
• Visual changes
• Changes in hearing

Should Dental Amalgam Fillings Be Removed?

If your filling is in good condition and your dentist or health care professional says there is no decay beneath the filling, removal of your amalgam filling is not recommended. This is because removing intact amalgam fillings may result in unnecessary loss of healthy tooth structure and potentially exposes you to a temporary increase in mercury vapor released during the removal process. Intact amalgam fillings in anyone, including those of greater risk such as pregnant or nursing mothers and children, should not be removed for the purpose of preventing any disease or health condition, unless considered medically necessary by a health care professional. If you have a health condition (especially sensitivity or allergy to mercury, or neurological or kidney disease), you should discuss the need for removal and replacement with your dentist or physician.

What Other Materials Can Be Used for My Filling and What Are Their Benefits and Risks?

The use of dental amalgam has been declining through the years, with materials such as resin-based composites and glass ionomers (sometimes called “porcelain”, “resin” or “white fillings”) being more widely used. The durability of these alternative materials has improved since they were first developed, but may not reach that of dental amalgam fillings, especially in areas with higher biting forces or wear and stress from chewing, such as the back teeth (molars). Dental amalgam has advantages over resin-based materials in certain clinical situations, for example:

• when a patient is identified as being at higher risk for tooth decay;
• when there is a need for large fillings in posterior (back) teeth where biting forces are high; and
• where moisture can present a problem for certain placement such as near the gumline.

Although resin-based materials may require more time for placement, they typically require the removal of less healthy tooth structure for placement, compared to dental amalgam. In addition, resin-based materials offer the added benefit in that they are color-matched to tooth structure and do not contain any heavy metals. However, resin-based materials also have risks associated with their use, with primary concerns being potential exposure and hypersensitivity to certain chemicals such as methacrylate and how long they will last (longevity).

If you need a filling, discuss all treatment options with your dental provider, including the benefits and risks of using dental amalgam and other dental restorative materials, to help you make an informed decision. If you are concerned about mercury exposure from dental amalgam, resin-based materials should be strongly considered. The decision about what material to use to fill cavities in teeth is one that should be made between you and your dental provider (and physician if needed).

The durability of any filling or tooth depends on many factors besides dental filling materials. To help your teeth and fillings last as long as possible, you should maintain a healthy diet, proper oral hygiene, and regular dental checkups.

Irritation of the pulp

When a deep cavity is filled, the vibration, heat and chemical stimulation that the tooth receives may irritate the pulp and generate pulpitis (inflammation of the pulp). This can result in pain when biting on the treated tooth or sensitivity to cold and hot substances. It may settle down spontaneously with time. If not, root canal treatment is usually conducted to resolve the pain and save the tooth.

Weakening of tooth structure

In situations where a relatively larger amount of tooth structure has been lost or replaced with a filling material, the overall strength of the tooth may be affected. This significantly increases the risk of the tooth fracturing in the future when excess force is placed on the tooth, such as trauma or grinding teeth at night. The standard treatment of large cavities and root canal therapy in premolars and molar includes sealing with a crown because this reduces the risk of fracture.

Good oral health helps you enjoy life. It lets you: speak clearly; taste, chew, and swallow delicious and nutritious foods; and show your feelings through facial expressions such as smiling.

If you protect your oral health with good oral hygiene practices (brushing and flossing), the odds are in your favor you can keep your teeth for a lifetime.

Brush Your Teeth

To keep your teeth healthy, it is important to remove dental plaque, a sticky, colorless film of bacteria. Plaque buildup can cause tooth decay and gum disease.

Even teeth that already have fillings are at risk for tooth decay. Plaque can build up underneath a chipped filling and cause new decay. And if there are areas in your mouth where your gums have pulled away from the teeth (called gum recession), the exposed tooth roots can decay as well.

Dental plaque is hard to see. You can see it more easily if you stain it. After you brush your teeth, chew “disclosing tablets” (which you can buy at a drug store), or brush with a special disclosing toothpaste. The color will show you where there is still plaque, and you can then brush those areas again to remove it. (Parents – Disclosing tablets can also be very helpful for teaching children how to do a good job brushing their teeth!)

Brushing tips:

• Use fluoride toothpaste. Fluoride is what protects teeth from tooth decay (cavities). It prevents decay by strengthening the tooth’s hard outer surface, called enamel.
• Angle the bristles toward the gumline, so they clean between the gums and teeth.
• Brush gently using small, circular motions. Do not scrub hard back and forth.
• Brush all sides of each tooth.
• Brush your tongue.

And, remember to replace your toothbrush when the bristles become frayed.

Clean Between Your Teeth

Cleaning between teeth to remove plaque is also part of a good oral hygiene routine. If plaque is not removed, some of it can harden below the gum line and irritate the gums. The gums become red, swollen, and may bleed easily. These are signs of gingivitis. Gingivitis is a mild form of gum disease, and you can usually reverse it with daily brushing and flossing.

If plaque stays on your teeth for too long, it can harden. This hardened plaque is called calculus, or tartar. The only way to remove tartar is to have your teeth cleaned by a dentist or dental hygienist. If the tartar is not removed, the gingivitis can get worse and lead to more severe gum (periodontal) disease. In advanced stages, gum disease causes sore, bleeding gums; painful chewing problems; loose teeth; and even tooth loss.

Floss to remove plaque, and food particles, from between your teeth.

Flossing tips:

Some people find flossing difficult because of arthritis or other issues. If it’s too hard to hold floss, try a plastic or wooden dental pick or one of these:

Helpful Tips

Follow these tips to keep your teeth and gums healthy:

• Brush your teeth twice a day with a fluoride toothpaste.
• Clean between teeth regularly to remove plaque. Use dental floss or a special brush or wooden or plastic pick recommended by a dental professional. Or try a floss holder, floss threader, or water flosser.
• Visit the dentist for routine check-ups and professional cleaning.
  • If you are at a higher risk for tooth decay (for example, if you have a dry mouth because of medicines you take), your dentist or dental hygienist may give you a fluoride treatment, such as a varnish or foam during the office visit. Or, the dentist may recommend a fluoride gel or mouth rinse for home use.
  • If you are at higher risk for gum disease because of a medical condition (for example, diabetes), your dentist may want to see you more frequently.
• Drink fluoridated water. Drinking water with the right amount of fluoride protects your teeth throughout the day.
• Don’t smoke. Smoking increases your chance of gum disease.
• If you are planning to become pregnant, have a dental checkup. Because of hormonal changes, pregnant women may develop gingivitis and experience gums that are swollen and bleed easily. During pregnancy, it is especially important to practice good oral hygiene to maintain the health of your gums.
• Eat a well-balanced diet. Limit sweets and sugary drinks, such as soda.