A Crown (cap) is an artificial material used to replace large parts of a tooth or a whole tooth that has been fractured or decayed. Crowns fit over and cover the outside of teeth, unlike fillings which only fill the cavities in teeth. While a cement is often placed between the Crown and the tooth to ensure that it remains secure, the Crown stays in place mainly because it fits so tightly over the tooth.
Often an impression (mould) of the mouth will be made to help the Dentist decide on the best approach to the tooth and in the construction of a temporary crown. The impressions are taken by placing a rubber paste/gel into a small holder which is pressed against the teeth. The rubber sets quickly and can soon be removed. The mould can then be used to make a plaster model of the mouth.
Often a tooth will need local anaesthetic to deaden any pain before it can be worked on. If the tooth already has a root canal filling no anaesthetic may be needed as no pain will be felt. The decayed tooth structure is removed using small drills to clean out the decay. Fine hand instruments, like small spoons may also be used. The remaining tooth then has to be very carefully milled (trimmed down) to an ideal shape. If there is not enough tooth structure left to work with, the Dentist may construct a core (which can be made out of a filling or may be cast metal, constructed in the dental laboratory), giving the Dentist something to work with. Occasionally more tooth will be exposed by doing a small crown-lengthening procedure on the gum around the tooth. This procedure removes part of the gum to reveal more of the tooth.
Once the tooth or core has been milled, a very accurate impression of the teeth needs to be taken. This impression is used by a dental technician to construct the final crown. The construction of the crown has to be very accurate, and usually takes a number of days to complete. During this time the Dentist will often make and insert a temporary crown out of a weak metal or acrylic which can protect the tooth while the final crown is being made.
After removing the temporary crown, the final crown is inserted over the tooth. The Dentist will check the fit of the Crown and the bite (the way the teeth fit together on biting), and make any necessary adjustments before cementing the crown in place.
Why do I need this?
After decay has been removed or after a fracture has occurred, very little may be left of the tooth. The remaining tooth needs to be sealed to protect it from further decay. The deeper parts of the tooth are more sensitive (as they are closer to the nerve) and a Crown provides a covering over the top of the tooth to act at a protective barrier. The missing tooth also needs to be replaced to allow it to function for eating and speaking and often for the sake of appearance. Crowns fit over the tooth like a thimble, thus helping to strengthen any remaining part of the tooth that may be weakened or brittle.
There are many types of Crowns and there is not any one type that will suit all teeth. Some Crowns are based on alloys (mixtures) of gold and other precious metals. These are often used in the back of the mouth, where good strength is required and the colour is not as important. Other crowns have a metal base which then has porcelain or acrylic baked onto the metal surface. These allow for a more realistic tooth colour. Some crowns are constructed entirely of acrylic or porcelain. Differing types of Crown constructions often mean widely differing costs.
IS it uncomfortable?
Having a Crown treatment is usually painless. Occasionally teeth may be a little sensitive for a few days after receiving a Crown, this is normal and should settle down naturally. Ask your Pharmacist for advice if pain relief is required. NEVER take more than the recommended dose and because there are certain pain relievers, anaesthetics and other medications which should not be used in combination it is important to tell your Dentist what kind of pain relieving medication you are taking.
Health careAs with all dental conditions your Dentist should be consulted. Your Dentist will diagnose and treat your particular problem. Ask your Dentist which is the best type of Crown