Dental treatments - fillings and crowns

Published by Bupa's Health Information Team, September 2009.

This factsheet is for people who would like information about having dental treatments.

Fillings, crowns, onlays, inlays, root fillings and veneers are used to restore decayed, worn or broken teeth or those affected by gum disease.

Your care will be adapted to meet your individual needs and may differ from what is described here. So it's important that you follow your dentist's advice.

About dental treatments

Teeth that are decayed, worn, broken or affected by gum disease may need to be restored by your dentist. The most common type of tooth damage is decay, mainly caused by eating or drinking sugary food and drinks. Your risk of developing decay can also be increased if you have poor oral hygiene, for example, not brushing or cleaning between your teeth properly.

Treatment options include fillings, crowns, veneers, inlays, onlays and root fillings. The extent of the damage to your teeth will determine which treatment is most suitable for you. Your dentist will discuss the options with you.

Types of dental treatment

Fillings

Fillings are used to fill holes (cavities) that have formed, usually as a result of decay or tooth wear. There are many types of filling, each suitable for different cavities.

Most people have a local anaesthetic injection to completely numb the area while the filling is being done. The numbness can take several hours to wear off.

If you're nervous of having an injection, ask your dentist if you can have an anaesthetic gel applied to the appropriate area of the gum instead. This gel numbs the gum so you can't feel the needle.

The decayed and weakened parts of the tooth are removed using small drills and the cavity is cleaned. If the cavity has spread to the side wall of your tooth, a band will be placed around the tooth with a small wedge holding it in place. This ensures that the filling hardens into the correct shape.

To protect the tiny nerves and blood vessels inside the tooth, very thin layers of underlinings, such as resin, are sometimes painted inside the hole before the filling material is packed in. The filling will either begin to harden during the first few minutes or, for some materials, a blue light is used to make it set within a few seconds.

Sometimes temporary fillings are used, at emergency appointments for example, where there may not be enough time to do the full treatment. Temporary fillings can last for quite a long time, but they aren't very strong so you will need to arrange to have a durable filling placed within a few weeks.

Amalgam fillings
Amalgam fillings are made of a combination of metals including silver, tin, copper and mercury. Amalgam is extremely durable and able to withstand the grinding and chewing of your back teeth over long periods of time.

Tooth-coloured fillings
You can choose tooth-coloured fillings to match the colour of your teeth, making them a natural-looking alternative to amalgam fillings. They are often used in teeth that show when you smile or talk. They aren't as durable as amalgam and so aren't always suitable for the grinding and chewing surfaces of the back teeth.

There are a few different types of tooth-coloured filling materials. The most common are called composite and glass ionomer. They are soft and can be moulded to the shape of a tooth before they harden. Tooth-coloured filling materials stick to teeth so they can be used to build up the edges of chipped or worn teeth.

Composite shrinks very slightly under the blue light. This can pull on the tooth and may cause sensitivity. It can also produce a tiny gap between the filling and your tooth that may attract bacteria and lead to further decay. However, more modern composites have significantly reduced this problem in recent years.

Tooth-coloured fillings must be kept completely dry until they have set, so the dentist will take special precautions to keep saliva away from the area. This may include placing a sheet of rubber over your tooth (called a rubber dam). This only stays in place during the treatment.

Glass ionomers can release fluoride which prevents decay. They aren't very durable and are usually used for children's teeth, small back fillings or fillings on root surfaces.

Crowns
If a tooth has been broken or weakened by a lot of decay or a large filling, you can have a crown (or cap) fitted to strengthen it and improve its appearance. You may have an X-ray taken to check your tooth. Crowns are shaped like natural teeth and fit over the prepared tooth. For teeth near the front of the mouth, crowns are usually made of ceramic materials. Crowns on back teeth may be made of porcelain or gold, or porcelain bonded onto gold. Gold crowns can either be gold or silver in appearance.

Newer ceramic crowns look like porcelain crowns and are strong enough to be used in all areas of the mouth.

Your dentist will give you a local anaesthetic injection to numb the tooth and will shape your tooth so that there is room for the new crown. Once prepared, a mould of your tooth is taken in a putty-like material so that the dental technician can make a crown that fits the tooth perfectly.

It may take one or two weeks for the crown to be ready, so your dentist will fit a temporary one. At the second appointment, your dentist will take off the temporary crown and cement the new one in place.

Inlays and onlays

Inlays and onlays are similar to fillings. An inlay is placed within the biting surface of the tooth while an onlay covers a larger area of the tooth. However, like crowns, they are made in a laboratory and then cemented to the tooth with special adhesive. You will probably need two visits to the dentist.

During the first visit, the dentist removes the old filling or decay and makes a mould of the tooth in a putty-like material. A temporary filling is placed to protect the tooth while the dental technician uses the mould to make the inlay or onlay. On the second visit, the temporary filling is removed and the inlay or onlay cemented in place.

Inlays and onlays are very strong and, in some circumstances, may be more durable than ordinary fillings. They are suitable for the grinding surfaces of the molar teeth and can be made from porcelain or composite material as well as gold.

Root fillings

Teeth have a core of blood vessels and nerves at their centre in a space called the root canal. Very deep decay or injury to a tooth can destroy this living tissue and make it darken in colour. A 'dead' tooth is prone to infection. This in turn may lead to an abscess which can cause pain and swelling around the tooth. The root canal needs to be cleaned out thoroughly before any restoration work is done.

Your dentist will give you a local anaesthetic injection to numb the area before removing any decay using a drill. It shouldn't feel any different to having a filling. A rubber dam will usually be placed over your tooth to keep it dry. Disinfectant and thin instruments are used to remove bacteria and dead cells from the root canals. There can be as many as four root canals in each tooth and they all need to be cleaned out in this way.

Afterwards your tooth is sealed by placing a temporary filling into the root canal. Once your dentist is happy that the infection has gone, a filling or crown can be placed on top.

Root fillings are complicated and you may need two or more appointments. You will need to have a number of X-rays during root canal treatment. When completed, a root filling should feel no different to an ordinary filling.

Veneers

This is when a thin layer of tooth-coloured material, usually porcelain, is fitted over a discoloured tooth.

On the first visit you may have a local anaesthetic injection to numb the tooth but this isn't always necessary. The surface of your tooth may be filed down slightly to allow for the added thickness of the veneer so bear in mind that it can't be reversed. Your dentist will then take a mould of your tooth in a putty-like material. This is sent to a laboratory where the veneer is made by a dental technician over one to two weeks. While you're waiting, you may have a slightly roughened, sensitive tooth. On the second visit your dentist will bond the veneer onto the front of your tooth.

Although veneers can last for many years, they can be damaged through an accident, break or chip and may need to be replaced.

What are the risks?

Amalgam fillings

Some people have concerns about the safety of amalgam fillings because they contain mercury. In large enough doses mercury is toxic. However, fillings only use very small amounts.

Very small amounts of mercury collect in our bodies from a number of sources including the environment, our food and our amalgam fillings. It's estimated that amalgam fillings account for a sixth of the average daily amount - about nine millionths of a gram.

Extensive research has been done to investigate the effect of amalgam fillings on health. No harmful effects from amalgam fillings have been shown and the World Health Organization (WHO) and the UK's Medicines and Healthcare products Regulatory Agency (MHRA) support the continued use of amalgam fillings. However, dentists take special precautions when removing amalgam fillings because drilling into the amalgam creates higher levels of mercury vapour. Your dentist uses extra water and suction to minimise the amount of vapour.

Although there is no evidence linking amalgam to birth problems, placing and removing amalgam fillings in pregnant women is generally avoided as a precautionary measure because mercury can be passed on through the placenta and breast milk. If you are or think you may be pregnant, tell your dentist so he or she can plan your treatment accordingly.

A very small number of people are allergic to metals in amalgam and may need to have another type of treatment.

Tooth-coloured fillings

Tooth-coloured filling materials don't contain mercury. However, there have been concerns that they release a chemical called bisphenol A. This chemical is also used in the manufacture of some food packaging and water pipes.

Bisphenol A appears to copy the action of human oestrogen hormones and has been linked to breast cancer, prostate cancer and male infertility. The British Dental Association has looked into this and found that most filling materials don't release bisphenol A. There is no evidence of harm from this type of filling. However, this chemical is being used less in newer filling products.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.