Dental
Crowns
A natural tooth consists of
a crown (the part you see above the gum), and the root (the
part hidden under the gum, within the jawbone). It is the
root that actually holds the natural tooth in place.
Why
is a dental crown needed?
A dental crown is used to do
any of the following:
1. To restore an already broken tooth or a tooth that has
been severely worn down
2. To protect a weak tooth from breaking or to hold together
parts of a cracked tooth
3. To hold a dental bridge in place
4. To cover and support a tooth with a large filling when
there isn't a lot of tooth left
5. To cover a dental implant
6. To cover misshaped or severely discolored teeth
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Are
there any risks involved?
If tooth decay is right next
to the pulp, the pulp may not be strong enough to make healthy
dentin. If this happens, the pulp may need to be removed by
a participating dentist or endodontist, or the whole root
may have to be removed by an oral surgeon.
Some dental procedures can cause bacteria in the mouth to
enter the bloodstream and cause infections in other parts
of the body. People who have difficulty fighting off infections
may need to take antibiotics before and after dental surgery.
Such people include those who:
• Were born with heart defects.
• Have damaged or artificial heart valves.
• Have liver disease (cirrhosis).
• Have an impaired immune system.
• Have a history of bacterial endocarditis.
• Have artificial joints, such as a hip that has been replaced.
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How
well do dental crowns work?
A crown will work just like
a healthy tooth. However, crowns can sometimes come loose
over time and may need to be replaced or cemented in again.
If the decay is near the centre of the tooth and bacteria
invade the pulp, the pulp may die. If this happens, the crown
may need to be removed and root canal treatment will be needed
to eliminate the bacteria and dead pulp.
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What types of crown
materials are available?
Permanent crowns can be metal,
porcelain-fused-to-metal, resin, or completely ceramic.
1. All-ceramic or all-porcelain dental crowns
provide the best natural color match than any other crown
type and may be more suitable for people with metal allergies.
However, they are not as strong as porcelain-fused-to-metal
crowns and they wear down opposing teeth a little more than
metal or resin crowns. All-ceramic crowns are a good choice
for front teeth.
2. Porcelain-fused-to-metal
dental crowns can be color matched to your adjacent teeth
unlike the metallic crowns. However, more wearing to the opposing
teeth occurs with this crown type compared with metal or resin
crowns. The crown's porcelain portion can also chip or break
off. Next to all-ceramic crowns, porcelain-fused-to-metal
crowns look most like normal teeth. However, sometimes the
metal underlying the crown's porcelain can show through as
a dark line, especially at the gum line and even more so if
your gums recede. These crowns can be a good choice for front
or back teeth.
3. Metals
used in crowns include gold alloy, other alloys (e.g. palladium)
or a base-metal alloy (e.g. nickel or chromium). Compared
with other crown types, less tooth structure needs to be removed
with metal crowns, and tooth wear to opposing teeth is kept
to a minimum. Metal crowns withstand biting and chewing forces
well and probably last the longest in terms of wear down.
Also, they rarely chip or break. The metallic color is the
main drawback. Metal crowns are a good choice for out-of-sight
molars.
4. All-resin
dental crowns are less expensive than other crown types. However,
they wear down over time and are more prone to fractures than
porcelain-fused-to-metal crowns.
5. Temporary
versus permanent. Temporary crowns can be made in a dental
practice whereas permanent crowns are made in a dental laboratory.
Temporary crowns are made of acrylic or stainless steel and
can be used as a temporary restoration until a permanent crown
is constructed by the dental laboratory.
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What
steps are involved in preparing a tooth for a crown?
Preparing a tooth for a crown
usually requires two visits. The first step involves examining
and preparing the tooth and the second visit involves placement
of the permanent crown
1. Examining and preparing the
tooth. At the first visit, your dentist may take a few x-rays
to check the roots of the tooth receiving the crown and surrounding
bone. If the tooth has extensive decay or if there is a risk
of infection or injury to the tooth's pulp, a root canal treatment
may first be performed.
o Before the process of making
your crown has begun, your participating dentist will inject
a local anesthetic that will completely numb the teeth, gums,
tongue, and skin in that area. Nitrous oxide gas may be used
to reduce pain and help you relax. Next, the tooth receiving
the crown is filed down along the chewing surface and sides
to make room for the crown. The amount removed depends on
the type of crown used (for instance, all-metal crowns are
thinner, requiring less tooth structure removal than all-porcelain
or porcelain-fused-to-metal ones). If, on the other hand,
a large area of the tooth is missing (due to decay or damage),
participating dentists will use filling material to "build
up" the tooth enough to support the crown.
o After reshaping the tooth,
participating dentists will use impression paste or putty
to make an impression of the tooth to receive the crown. Impressions
of the teeth above and below the tooth to receive the dental
crown will also be made to make sure that the crown will not
affect your bite.
o The impressions are sent
to a dental laboratory where the crown will be manufactured.
The crown is usually returned to your participating dentist
in 2 to 3 weeks. If your crown is made of porcelain, your
participating dentist will also select the shade that most
closely matches the color of the neighboring teeth. During
this first visit your participating dentist will make a temporary
crown to cover and protect the prepared tooth while the crown
is being made. Temporary crowns usually are made of acrylic
and are held in place using temporary cement.
2. Receiving
the permanent dental crown. At your second visit, a participating
dentist will remove your temporary crown and check the fit
and color of the permanent crown. If everything is acceptable,
a local anesthetic will be used to numb the tooth and the
new crown is permanently cemented in place. Your participating
dentist will then have you bite on a piece of carbon paper
that will indicate any high spots and reshape and polish the
crown to fit the tooth.
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What
can I expect after treatment?
Your lips and gums may remain
numb for a few hours until the anesthetic wears off. Avoid
chewing on your numb lip or cheek to avoid injuring your mouth.
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How should
I care for my temporary dental crown?
Most dentists suggest that
a few precautions be taken with your temporary crown.
1. Minimise the use of the side of your mouth with the temporary
crown. Shift the bulk of your chewing to the other side of
your mouth.
2. Avoid chewing hard foods (e.g. raw vegetables) which could
dislodge or break the crown.
3. Avoid sticky and chewy foods (e.g. chewing gum, caramel)
which have the potential of grabbing and pulling off the crown.
4. Slide flossing material out-rather than lifting out-when
cleaning your teeth. Lifting the floss, out as you normally
would, might pull off the temporary crown.
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What
problems could develop with a dental crown?
1. Allergic reaction. Because
the metals used to make crowns are usually a mixture of metals,
an allergic reaction to the metals or porcelain used in crowns
is extremely rare.
2. Discomfort or sensitivity.
Your newly crowned tooth may be sensitive immediately after
the procedure as the anesthesia begins to wear off. You may
experience some hot and cold sensitivity if the tooth that
has been crowned still has a nerve in it. Your dentist may
recommend that you brush your teeth with a toothpaste designed
for sensitive teeth. Pain or sensitivity that occurs when
you bite down usually means that the crown is too high on
the tooth. Call your dentist if this is the case. He or she
can easily fix this problem.
3. Loose crown. Sometimes the
cement washes out from under the crown. Not only does this
allow the crown to become loose, it allows bacteria to leak
in and cause decay to the tooth that remains. Contact your
dentist in the event that your crown feels loose.
4. Chipped crown. Crowns made
of all porcelain can sometimes chip. If the chip is small,
a composite resin can be used to repair the chip with the
crown remaining in your mouth. The crown may need to be replaced
if the chipping is extensive.
5. Crown that falls off. Sometimes
crowns fall off. Usually this is due to an improper fit or
a lack of cement. If this happens, clean the crown and the
front of your tooth. You can replace the crown temporarily
using dental adhesive or temporary tooth cement that is sold
in stores for this purpose. Contact your dentist's office
immediately. He or she will give you specific instructions
on how to care for your tooth and crown for the day or so
until you can be seen for an evaluation. Your dentist may
be able to re-cement your crown in place; if not, a new crown
will need to be made.
6. Dark line on crowned tooth
next to the gum line. A dark line next to the gum line of
your crowned tooth is normal, particularly if you have a porcelain-fused-to-metal
crown. This dark line is simply the metal of the crown showing
through.
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What
are "onlays" and "3/4 crowns"?
These are variations on the
technique of dental crowns. The difference between these crowns
and the crowns discussed previously is their coverage of the
underlying tooth - the "traditional" crown covers
the entire tooth; onlays and 3/4 crowns cover the underlying
tooth to a lesser extent.
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How long
do dental crowns last?
Dental crowns last between 5
and 15 years. The life span of a crown depends on the amount
of wear and tear the crown is exposed to, how well you follow
good oral hygiene practices, and your personal mouth-related
habits (you should avoid such habits as grinding or clenching
your teeth, chewing ice, biting your fingernails and using
your teeth to open packaging).
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Does
a crowned tooth require any special care?
While a crowned tooth does not
require any special care, remember that simply because a tooth
is crowned does not mean the underlying tooth is protected
from decay or gum disease. Therefore, continue to follow good
oral hygiene practices, including brushing your teeth at least
twice a day and flossing once a day-especially around the
crown area where the gum meets the tooth.
TEETH
IN AN HOUR - Teeth
In An Hour is a new protocol that allows patients to leave
the office with fixed teeth in less an one hour.
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