What is a dental filling?

A dental filling or restoration is a treatment designed to repair a cavity in your tooth caused by decay. Amalgam fillings are the most common type available. They are made from a mixture of mercury and different metals. However more aesthetically pleasing white fillings are also available.

There are some NHS restrictions on the types of materials clinicians can provide in certain teeth. You can ask your dentist if a different filling material is appropriate (such as a white composite filling instead of a silver amalgam filling), however, you may have to pay for this as a private treatment.

The choice of filling material for any cavity will depend upon many factors including the size of the cavity, the type of tooth being treated and how heavy your bite is in the area being treated.

Typical treatment length

30 minutes

Types of fillings


Most people recognise dental amalgams as silver fillings. A dental amalgam is made up from around 50% elemental mercury which is combined with either silver, tin or copper. The mercury binds the amalgam together to make it a strong and durable filling.

Advantages of amalgam

  • Strong and malleable, it is the filling of choice for back teeth as it can fill large cavities easily. It also sets quickly and can be bitten on within a few hours
  • They are cheaper than white fillings
  • Clinically proven to be a good filling choice
  • Easily repaired

Disadvantages of amalgam

  • Not suitable for everyone including pregnant and nursing mothers, children and people with a mercury allergy
  • Not as aesthetically pleasing as some other options


Also known as white fillings, composite fillings as classed as a cosmetic treatment. Composites have been around for over 40 years and consist of glass particles, synthetic resin and a setting ingredient.

Your clinician will be able to advise you as to the exact ingredients used.

Advantages of composite

  • Creates a natural looking filling
  • Suitable for small and medium sized fillings
  • Matches the shade of your teeth

Disadvantages of composite

  • Not suitable for very large restorations
  • Is a more time consuming procedure as the composite technically more difficult to place
  • Their life span can sometimes be less than their amalgam counter parts

Glass Ionomers

A less well known filling is the glass ionomer, this filling is based on the reaction of silicate glass powder and polyalkenoic acid, an ionomer. They are a type of white filling.

Advantages of glass ionomers

  • Releases fluoride which can help prevent decay around the filling
  • Effective fissure sealants

Disadvantages of glass ionomers

  • This filling is fairly weak and is most suitablefor baby teeth and non biting surfaces