A crown is a tooth-shaped "cap" placed over a tooth that is badly damaged or decayed. It is an artificial restoration that fits over the remaining part of a repaired tooth, makes it strong and gives it the shape of a natural tooth.
Reasons for placing a crown:
- To replace a large filling when there isn't enough tooth material remaining
- To protect a weak tooth from fracturing
- To restore a fractured tooth
- To attach a bridge
- To cover a dental implant
- To cover a discolored or poorly shaped tooth
- To cover a tooth that has had root canal treatment
Materials
Crowns are made in the dental laboratory. Crowns can be all metal, porcelain fused to metal, porcelain fused to precious metal or all ceramic. Metals include gold alloy and other alloys (Palladium, Nickel or Chromium). The all-metal or porcelain fused to metal crowns are stronger and are better choices for back teeth. Porcelain fused to metal and all-ceramic crowns look just like normal teeth. All-ceramic crowns are metal-free, strong and have the appearance of a porcelain crown. Therefore, it is suitable for use in all areas of the mouth. Crowns last at least eight years, but in many cases they last much longer, up to 40 years or so.
Process
If you need a crown, you may also need a root canal treatment on the tooth, due to extensive decay or the risk of infection or injury to the tooth's pulp. However, not everyone needs a root canal treatment that needs a crown.
If you are receiving the crown after a root-canal treatment, your dentist may insert a post-and-core foundation, which is needed if large areas of the natural tooth structure were decayed, damaged, or missing. A post may be necessary to support the crown and to help the crown stay in place. A post crown can be made of prefabricated stainless steel which the dentist can fit directly into the root canal, or a custom-made post can be constructed by the dental technician to fit the shape of the prepared root canal properly. The post is placed into the root canal and cemented in position, ready for the crown to be attached.
Preparation
The dentist will prepare the tooth by removing most of the outer surface, and leaving a strong inner core. Once the tooth is shaped, the dentist will take an impression of the prepared tooth, and one on the opposite side of the jaw to make sure the crown will not affect your bite. The impression material sets for three or four minutes and is removed.
The impressions will then be given to the dental technician and sent to the lab, along with an appropriate shade of color and any other information needed for the crown to be made. In the meantime, you will receive a temporary crown. These crowns are usually made of acrylic and are made in your dentist's office on the day of your visit or in the laboratory. They are not meant to last. At your second visit, your dentist will remove the temporary crown and test the permanent one. Sometimes crowns need additional polishing or glaze before they are placed. Once the crown is ready, it's cemented onto your tooth.
How long does the treatment take?
The treatment takes at least two or three visits: the first, for the preparation, impression, color matching and fitting of the temporary crown; the second and third visit for the trial and fitting of the permanent crown. The visits generally take 1 to 2 weeks.
