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crown is a tooth-shaped cover placed over a tooth that is badly damaged
or decayed. A crown, which many people call a cap, is made to look like
your tooth.
Crowns may be placed for several reasons, but generally the tooth has
been extensively damaged by decay or breakage and filling material can't
replace the missing tooth structure and make the tooth strong enough.
A crown may hold together parts of a cracked tooth and can be used to
hold a bridge in place. Crowns also are used for cosmetic purposes to
cover misshapen or badly discolored teeth.
Crowns can be prefabricated or made in a laboratory. Prefabricated crowns
are made of plastic or stainless steel and can be used as a temporary
restoration until a permanent crown is manufactured. In some cases, prefabricated
crowns can be used as a permanent restoration.
Crowns can be all metal, porcelain fused to metal (PFM), or all ceramic.
Metals include gold alloy, other alloys (palladium) or a base-metal alloy
(nickel or chromium). The all-metal or PFM crowns are stronger and are
better choices for back teeth. PFM and all-ceramic crowns look just like
normal teeth.
Usually, crowns last at least 7 years, but in many cases they last much
longer, up to 40 years or so.
Preparing the Tooth
If you need a crown, you may also need endodontic or root canal treatment on
the tooth, due to extensive decay or the risk of infection or injury to
the tooth's pulp. Not everyone who needs a crown will also need a root
canal.
Besides the crown, your dentist may need to build up a foundation to
support the crown. A foundation is needed if large areas of the natural
tooth structure 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 must file down the tooth to make room
for it. If you are receiving an all-metal crown, less tooth structure
will be removed because these crowns are thinner than PFM or all-porcelain
ones.
After filing down the tooth, your dentist will use a piece of thread
or cord to push the gum down around the tooth, and then make an impression
of the tooth. The impression material sets in five or six minutes and
is removed. Your dentist will also take an impression of the teeth above
or below the tooth that will receive the crown, to make sure the crown
will not affect your bite.
The impressions are sent to the lab, where the crown is made. During
that time, you will have a temporary crown. These crowns are usually
made of plastic and are made in your dentist's office on the day of your
visit. They are not meant to last. If a temporary crown is left in the
mouth, the cement eventually washes out and the tooth can decay.
At a second visit, your dentist will remove the temporary crown and
test the permanent one. Sometimes crowns need additional polishing or
glaze 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,
though if your tooth still has the nerve in it, you may have some hot/cold
sensitivity. If you notice pain or sensitivity when you bite down, you
should contact your dentist. Usually this means that the crown is too
high on the tooth. This can be fixed easily.
You may notice a dark line next to the gumline on your crowned tooth,
particularly if you have a PFM crown. This dark line is the metal of
the crown showing through and is normal. A crowned tooth is not protected
from decay or gum disease. You should continue practicing good oral hygiene.
Crowns, especially all-porcelain ones, can chip. This can sometimes
be repaired in the mouth. Your dentist will etch the porcelain with acid
and bond composite resin to it to fix the chip. If the chipping is extensive,
you may need a replacement crown.
It's also 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, contact your dental
office.
Your crown may fall out, due to a lack of cement or an improper fit.
If this happens, clean the crown and the tooth. You can replace the crown
temporarily using denture adhesive or temporary cement sold for this
purpose. 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 re-cement the old one on the tooth.
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