What is a crown?
Your dentist may suggest placing a crown as part of your treatment plan. A dental crown or ‘cap’ is a restoration which covers over and encases the natural tooth and is designed to look like a real tooth. Dentists use crowns when rebuilding broken or decayed teeth or to improve the cosmetic appearance of a tooth. Crowns are made in a dental laboratory by a dental technician who uses moulds of your teeth made by your dentist. The type of crown your dentist recommends will depend on the tooth involved and your preference. Materials available include porcelain bonded to metal, gold alloy and metal-free zirconia.
Apart from cosmetic indications, the most common reason for suggesting a crown is to strengthen an already weakened tooth. When more that half of the tooth is filling material, the tooth will be weak because there will only be a thin shell of real tooth on one side. If a tooth has had a root canal, the tooth is likely to have had a deep area of decay in the past, and now a deep filling (the root canal itself doesn’t weaken the tooth). Occasionally the tooth may have not developed properly, and a crown will restore the structure. Often around old amalgam fillings large cracks may threaten to split your tooth in two. Such an event is disastrous for a tooth, and will result only in extraction. Crowning in all cases will cap the entire surface of the tooth with a thin shell of very strong material- like a helmet, holding together cracks, building up lost tooth structure and adding great strength. The tooth needs to be prepared by shaving back the tooth on all sides by about 1mm, otherwise the cap would be too big to go over the tooth. This may sacrifice some tooth enamel, but the overall gain makes it worthwhile.
What do you use to glue in crowns?
At Cornerstone dental, we cement crowns using a variety of different materials, depending on the purpose. Resin-Modified Glass Ionomer Cement has good flow properties (it can be thinned out well, important for cements), does not dissolve well, releases fluoride, and is biocompatible (liked by tooth and gum tissue). Resin cements can be used to bond porcelain crowns to tooth for higher strength and adhesion, much like a filling can be bonded to tooth- but need to be kept very dry when placed. Zinc oxide is a very traditional cement still used today, but mainly on temporary crowns which need to be later replaced, or gold crowns which can rely on a precise fit rather than the cement to hold them in.