How do you tell when a tooth needs a crown? A dental crown is needed when a tooth is badly broken down—either a cusp has broken off or is at risk of breaking, or there are large old fillings or a large amount of tooth decay. If a small part of the tooth is damaged by decay, a filling will do. Larger defects require a crown when the tooth has extensive damage. Our web site has some information to help you decide which type to get.
To give you an idea of how large a simple filling should be, the picture on the left shows three teeth with fillings. While two of the fillings are an appropriate size, the filling in the middle tooth is too large and this tooth should have a crown. The buccal cusps, which you see toward the top of the photograph, are too thin and are at high risk of breaking.
What type of crown does your tooth need?
The strongest dental crowns have some type of metal in them. An all-metal crown is usually made of gold because of its resistance to corrosion and its excellent fit. There are cheaper metals, though, which can reduce the fee maybe ten to twenty percent. But using a cheap metal is false economy. As much as 80 to 90% of the cost of a crown is in the labor, so you save very little by using a cheaper metal. But you lose a lot in the reduction of the precision in the fit. The greatest threat to the lifespan of a crown comes from decay that might leak into the tooth from an open margin between the crown and the tooth. Softer gold alloys can be cast to a very precise fit, greatly minimizing the chance of any of this leakage.
The least expensive crowns are made of stainless steel. They are usually factory-made and then crimped to fit the tooth. This is usually the type of crown that is put on a baby tooth, because, while it doesn’t last as long as a precision-fit one, it is good enough to hold up until the tooth falls out. Its ease of placement, since it doesn’t need any laboratory work, make it a fraction of the cost of a precision crown.
Another type is porcelain-fused-to-metal. It has a metal core, and has porcelain baked on the outside.
A third basic category is an all-porcelain crown.
Something a little bit different are porcelain onlays. While porcelain onlays cover all or most of the chewing surface of the tooth, they don’t go all the way to the gumline as crowns do, so less of the tooth has to be ground away, and there isn’t any chance that they will irritate the gum.
When you have a crown on a front tooth, a true cosmetic dentist will recommend an all-porcelain crown. General dentists generally feel more comfortable doing porcelain fused to metal in these situations, but porcelain fused to metal crowns have serious esthetic shortcomings. You can read about those if you follow the link.
There is also a CEREC crown technology for making one of these restorations by computer. A CAD-CAM device mills a block of very tough porcelain while you wait in the chair, meaning that you can get your crown in the same appointment that your tooth is prepared. Otherwise, two appointments are required.
Some people have been told by their dentists that they have soft teeth and that is why they need crowns. They say this because the person gets a lot of decay, but this isn’t from soft teeth. Read the page to find out the real cause of teeth being extra susceptible to decay.
Some metals used in these restorations can provoke metal allergy.
This content was written by Dr. David Hall. Click here to ask Dr. Hall a question.