A filling is a dental procedure where material is used to replace tooth structure that has been lost due to tooth decay or a minor fracture. The filling restores lost tooth structure and re-establishes the contour of the tooth. Fillings are also referred to as “direct restorations” because the decay is removed, the tooth is prepared to receive the filling, and filling material is placed directly into the preparation, restoring the tooth to its original shape. There are three primary types of filling materials that are generally used today; silver amalgam, glass/plastic composite and glass ionomer. Though no longer as popular as in the past, some patients still ask for gold foil, a fourth material option.
Types of fillings
Amalgam (silver filling)
Amalgam restorations, or “silver fillings,” have been used to fill teeth for hundreds of years. Amalgam is composed of mercury and powdered metal called an alloy, which is made up primarily of silver, copper, tin, and zinc. This type of filling material is manufactured in a capsule with a membrane separating the mercury from the metals. When mixed (in a triturator or amalgamator), the membrane breaks and the material gains a thick, creamy consistency. The amalgam is placed in the preparation, condensed, burnished, and carved. The amalgam restoration is fully set in 24 hours.
When a tooth is prepared to receive an amalgam, the preparation needs to have retention grooves and be undercut in order to lock the filling into place. Therefore, in order to use amalgam to replace lost tooth structure, more tooth structure must be removed to be sure the filling will stay in place.
Advantages of amalgam restorations:
- Amalgam is cost-effective.
- Amalgam is strong and lasts a long time.
- The placement of amalgam is less technique-sensitive, making it the preferred restoration in situations where isolation of the tooth from blood or saliva is not possible.
Disadvantages of amalgam restorations:
- Amalgam is not tooth-colored, making it less desirable.
- Although amalgam can be bonded into the tooth with the use of a metallic bonding agent, tooth structure needs to be shaped through material removal to lock the filling into place.
- Because of mercury content, the use of amalgam has been controversial for decades, due to the effect of mercury content on humans.
Composite (white filling)
Composite restorations, or tooth-colored fillings, are composed of powdered glass and plastic resin. Manufactured in light-tight capsules, this material is completely mixed in shades designed to match your teeth. Composite is very light-sensitive and must be covered when not in use because it cures (hardens) in the presence of light.
The technique for placing a composite restoration is very specific and must be followed accurately. Decay is removed from the tooth, along with any loose, jagged enamel (called “loose enamel rods”). There is no need to remove any more tooth structure for retention of the filling, as is necessary for amalgam. The tooth is isolated or kept dry (possibly with the use of a rubber dam), and an acid etch solution is placed in and over the edges of the area of preparation for 10-15 seconds. After a thorough rinse, the preparation is left damp and an adhesive solution is placed, spread out with a stream of air and cured with a UV light. The composite material is then placed in the preparation and cured with a UV light. Composite material may be applied in layers, depending on the size of the preparation. The filling is then shaped and polished.
Advantages of composite restorations:
- Composite is tooth-colored.
- Composite is strong and durable.
- Composite requires removal of less tooth structure.
- Composite is bonded into place and believed to make the entire tooth stronger.
Disadvantages of composite restorations:
- Composite undergoes some shrinkage when cured and may need to be placed in layers, therefore requiring more time to complete treatment.
- This shrinkage makes such fillings more difficult to place (more technique-sensitive) and can result in extreme tooth sensitivity following placement.
- If the preparation is contaminated with blood or saliva during the filling process, the technician must repeat the entire procedure over, beginning with the acid etch. Blood and saliva contamination prevent the composite from bonding to the tooth and the tooth will present with recurrent decay in a short time.
- Composite is more expensive.
Glass ionomer (a white filling that releases fluoride)
Glass ionomer restorations are composed of glass and organic acid. Although they are tooth-colored, they are more matte or opaque than composite restorations. Glass ionomers may need to be light cured, or they may set by an acid/base reaction. Glass ionomer restorations release fluoride and are desirable when you have a higher risk of Tooth Decay.
Advantages of glass ionomer restorations:
- Glass ionomer is tooth-colored.
- Glass ionomer requires minimal tooth removal for placement.
- Glass ionomer releases fluoride, and the fluoride is “replenished” when you brush with a fluoride toothpaste or get fluoride treatment at the dentist.
- Glass ionomer does not require the bonding agents that composites require, making placement faster.
- Glass ionomer does not shrink the way composites can during the setting phase.
Disadvantages of glass ionomer restorations:
- Although they are tooth-colored, they do not polish as well as composite restorations.
- They are not as strong as composite restorations.
- They are about the same cost as composite restorations.
Gold foil (gold fillings)
Gold foil is mentioned only because, even though this type of filling has fallen out of use, there are a few individuals whose teeth still have gold foil as a filling material. Gold foil is manufactured with tiny, soft pieces of gold that are compressed (tapped) into the cavity preparation, carved, and polished.
Advantages of gold foil restorations:
- Gold is kind to the opposing teeth, creating the least amount of wear of any dental restorative material.
- Gold foil is strong and resists wear.
Disadvantages of gold foil restorations:
- Gold foil is not tooth-colored.
- Gold foil placement is time consuming.
- Depending on the market, gold foil can be expensive.
Indications for a filling
Fillings are indicated when you have lost less than half of the surface structure on the biting surface of the tooth, between the tips of the cusps. Once you lose a cusp or start placing fillings up the inclines of cusps, the strength of the tooth is compromised and a Crown or an Inlay/Onlay should be considered as the preferred means of restoration. Unfortunately, many patients cannot afford the preferred restoration, and many large fillings are placed as an alternative. Some of the problems that may occur when restorations that are too large are placed include, but may not be limited to:
- Weakness of the remaining tooth which may lead to a fracture.
- Reduction of tooth structure may cause the remaining tooth to flex when you bite down, causing pain.
- Overly of large fillings can irritate the pulp (nerve) and cause death of the tooth, requiring a Root Canal Treatment.
Sometimes fillings are simply replaced due to more decay around the existing filling (called “recurrent decay”). Sometimes silver fillings are fractured and cavity producing bacteria and sugar can seep down into the crack and under the filling, creating more decay; fractured fillings need to be replaced.