Fillings are materials placed in the teeth to replace parts of a natural tooth. The most common cause is dental decay (dental caries), a bacterial induced process that dissolves the tooth. However, other causes exist which include erosion, a process whereby tooth substance is dissolved by acid either from dietary sources or by regurgitation, and abrasion caused by mechanical wearing of the teeth eg incorrect tooth brushing. The loss of tooth substance created by the process can lead to pain as a result of exposure of the sensitive parts of the tooth called the dentine and pulp.
Various materials are used as fillings:
Amalgam: This is the oldest and still most commonly used material for replacing large amounts of tooth substance in back teeth. It is an amalgamation of various metals such as silver and copper with mercury. There has been a great deal of concern about the use of amalgam over the years, particularly because of the mercury content. There is currently no proven risk to patients from the use of this material and it remains a good material for large cavities. There have however been some reports of allergy to the material or its constituents.
The advantage of this material is that it has a proven record for lasting many years and is relatively easy for the dentist to use. The disadvantages are that it is grey in colour and does not stick to the tooth, unlike some of the other filling materials.
Composite: Dental composite is made from acrylic and quartz and is tooth coloured. Considerable advances have been made in the composition of dental composites and in certain circumstances they can bond to the tooth, which is an advantage. They are generally more difficult to place than dental amalgam and in large cavities can cause stress within the tooth, which might cause some pain after they have been placed. This usually passes after a few days.
Dental composites are particularly good for filling front teeth because of their ability to match tooth colour and may also be used to change the shape of teeth. The bonding of the material to tooth may allow for the material to be used in small cavities within teeth.
The material is set hard (cured) by a blue light, which allows the dentist time to place it. It is very sensitive to moisture before it has cured and the dentist will need to use techniques to prevent contamination before it is set.
Glass ionomer: This material is tooth coloured and is made from glass. It sticks to tooth and can be used in small, shallow cavities, but it has poor strength. It is very useful in children’s teeth and can leach fluoride, which helps prevent further decay. It is sometimes used with dental composite to help the sealing of the tooth. Like composite it is very sensitive to moisture before it has set. Setting occurs by mixing the powder and liquid together, although the material can also be mixed with composite during manufacture to allow it to be cured with a light.
Glass ionomer cements have also been mixed with metals to improve their strength.
Cements: Dental cements are used as temporary fillings (eg in cases of emergency) when several fillings have to be done in a short period of time and when further treatment to a tooth may be required. They are made of zinc oxide and eugenol or similar materials and may last for a few weeks to many months. Some patients are allergic to eugenol and so non-eugenol cements are used.