what are dental crowns?

A crown is a tooth-shaped cover placed over a tooth that is badly damaged or decayed. A crown is made to look like your tooth. Many people call it a cap.

Crowns may be placed for several reasons. Usually the tooth has been broken or damaged a great deal by decay. As a result, a filling can’t replace enough of the tooth or make the tooth strong enough. A crown may hold together parts of a cracked tooth. It also can be used to hold a bridge in place. Crowns can be used to improve appearance as well. They may be placed to cover misshapen or badly discoloured teeth.

Crowns can be made ahead of time (prefabricated) or made to order in a laboratory. Prefabricated crowns are made of plastic or stainless steel. They can be used on a temporary basis until a permanent crown is made.

Crowns can be all metal, porcelain fused to metal (PFM), or all ceramic. We tend to make our crowns out of a material called Zirconia. Not only is it ten times stronger than an ordinary metal or PFM crown, but it is also bio-compatible with the body. Zirconia crowns can also mimic the natural dentition a lot better than the older PMF crowns. Crowns usually last at least seven years. In many cases they last much longer, up to 40 years.


preparing the tooth

Before placing a crown, your dentist may need to build up a foundation to support it. A foundation is needed if large areas of the tooth are decayed, damaged or missing. If you are receiving the crown after root canal treatment, your dentist may insert a post-and-core foundation.

To place a crown, your dentist will file down the tooth to make room for the crown. If you are receiving an all-metal crown, less of the tooth needs to be removed because these crowns can be made thinner than Zirconia crowns.

After filing down the tooth, your dentist will use a piece of thread or cord to push down the gum around the tooth. Then the dentist will make an impression (copy) of the tooth with a rubber-like material. The impression material sets in about five minutes. Then it is removed. Your dentist will also take an impression of the teeth above or below the tooth that will receive the crown. The purpose is to make sure the crown will fit into your normal bite.

The impressions are sent to the lab, where the crown is made. During that time, you will have a temporary crown placed. These crowns are usually made of plastic. They are made in advance by the laboratory or made by the dentist during your preparation visit. Then the dentist fits the temporary crown to your tooth.

These crowns are not meant to last for a long time. In some cases, however, a temporary crown can stay in place for a year or longer. If it needs to last longer, a lab-made plastic crown is best. It is stronger and will last longer than a temporary plastic crown that is made by the dentist.

Temporary cement is used to keep the crown in place. It is special cement that is designed to be weak. This allows your dentist to easily remove the temporary crown at each visit as your permanent crown is fitted.

At a second visit, your dentist will remove the temporary crown and test the permanent one. Sometimes crowns need additional polishing or glazing or some other adjustment before they are placed. Once the crown is ready, it’s cemented to your tooth.


after a crown

You shouldn’t feel any discomfort or sensitivity after a crown is placed. However, if your tooth has not had a root canal it will still contain the nerve. You may therefore have some temporary sensitivity to heat and cold. If you notice pain or sensitivity when you bite down, contact your dentist. Usually this means that the crown is too high. This can be adjusted easily.

A crowned tooth is protected from decay, except for the gum line. A crown does not protect against gum disease. You should continue practicing good oral hygiene.

It is possible that the cement could wash out from under the crown, but the crown does not fall out. Under these conditions, bacteria can leak in and cause decay. If your crown seems loose when you chew, or if you have an unusual odour around the tooth, discuss this with your dentist. Your dentist will check your crowns at your regular visits.

Crowns sometimes fall out. This can be caused by a lack of cement or an improper fit. If this happens, place the crown in a secure, zip-top plastic bag. Then bring it to your dentist to have it cemented back in place. If you are in no discomfort and your appearance is not affected, don’t try to put the crown back in place yourself.

If you do need to put it back in your mouth, clean it well on the inside and place it back on the tooth. Contact your dental office immediately and try to schedule a visit for the next day.

If you are away from home, seek a dentist in the area who can evaluate the problem. You may need a new crown or it may be possible to cement the old one back on the tooth.


 

zirconia crowns

what are zirconia crowns?

Zirconia has been used in orthopedic surgery for years, and has proved to be highly bio-compatible. Zirconia manufacturers have worked on new crowns that are custom milled from solid blocks of Zirconia and baked at extremely high temperatures so that the completed crown is pretty near unbreakable. Zirconia is 100% biocompatible. It is inert, and the body does not reject zirconia so you don’t have to worry about allergies or adverse reactions.

Zirconia Crowns have several advantages of both traditional Gold Crowns and Porcelain.

Although Gold Crowns are well tolerated, last long and are a good technical choice, many consumers much prefer to have a natural effect that blends into the overall smile. Many also don’t want metal in their mouths.

In most cases the choice will be between a Porcelain Crown and a Zirconia Crown. Zirconia Crowns have several advantages of standard Porcelain crowns.


strength and longevity

Zirconia is virtually indestructible whereas Porcelain crowns are prone to chipping. Crowns have a lifetime of around 10 years. Zirconia should last a lifetime.


cosmetic

Have you ever seen people with a large unsightly black line above their gums? Up until recently most crowns are Porcelain which is Fused to a Metal base. Over time, the metal begins to show more and more and the restoration can look opaque and monochromatic, with the tell tale dark grey line at the crown join.

The Zirconia Crowns not only look more translucent, but are much stronger than the Porcelain fused to the Metal posts. The Zirconia crowns are milled from a single block of crystal and can be up to five times stronger than a porcelain / metal fuse.


less tooth removal

In cases where there is not much room for porcelain build up – for example if a tooth abutment is already quite bulky, a Zirconia Crown can be used because it provides more strength in less volume than a porcelain crown.