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Both crowns and most bridges are fixed
prosthetic devices. Unlike removable devices such as
dentures, which you can take out and clean daily, crowns and
bridges are cemented onto existing teeth or implants. Tooth
crowns and dental bridges are often confused. The difference
between a crown and a bridge is that a tooth crown is used
to repair and strengthen a damaged or decayed tooth, while a
dental bridge is used to replace a missing tooth. Both of
these restorations are permanently bonded to your natural
tooth or teeth. These restorations are used to correct your
bite and restore your teeth's strength and function, as well
as give you back a beautiful, full smile if you are missing
any teeth.
How are Crowns and Bridges Made?
Before either a crown or a bridge can be
made, the tooth (or teeth) must be reduced in size so that
the crown or bridge will fit over it properly. After
reducing the tooth/teeth, your dentist will take an
impression to provide an exact mold for the crown or bridge.
If porcelain is to be used, your dentist will determine the
correct shade for the crown or bridge to match the color of
your existing teeth.
Using this impression, a dental lab then makes your crown or
bridge, in the material your dentist specifies. A temporary
crown or bridge will be put in place to cover the prepared
tooth while the permanent crown or bridge is being made.
When the permanent crown or bridge is ready, the temporary
crown or bridge is removed, and the new crown or bridge is
cemented over your prepared tooth or teeth.
Essentially, a bridge is a fake tooth that is fused between
two dental crowns. Unlike a dental implant, crowns on either
side of the tooth gap support the bridge. Bridgework begins
by shaping the teeth on either side of the gap so that they
can be fitted with tooth crowns. Then, an impression of both
the teeth and the gap is made so that a custom bridge can be
made that perfectly fits your teeth. While the custom bridge
is being created, you will be fitted with a temporary bridge
so that you can begin to feel what the real reparation is
like.
When the permanent, custom bridge is finished, can be
removed and the permanent one can be bonded to your teeth.
With your bridge in place, you can once again eat the foods
you like and smile with confidence, knowing that there are
no gaps in your smile. If you have more than one missing
tooth, then a combination of a bridge and dental implants,
partial dentures, or full dentures might better serve your
dental needs.
How Long do Crowns and Bridges Last?
While crowns and bridges can last a
lifetime, they do sometimes come loose or fall out. The most
important step you can take to ensure the longevity of your
crown or bridge is to practice good oral hygiene. A bridge
can lose its support if the teeth or bone holding it in
place are damaged by dental disease. Keep your gums and
teeth healthy by Brushing with fluoride toothpaste twice a
day and flossing daily. Also see your dentist and hygienist
regularly for checkups and professional cleanings.
To prevent damage to your new crown or bridge, avoid chewing
hard foods, ice or other hard objects.
MORE ABOUT DENTAL CROWNS
How do Crowns Work?
A crown is a restorative that covers, or
"caps," to strengthened a damaged tooth to restore it to its
normal shape and size. Crown can be used to improve the
tooth appearance, shape or alignment. Crowns are necessary
when a tooth is generally broken down and fillings won't
solve the problem. If a tooth is cracked a crown holds the
tooth together to seal the cracks so the damage doesn't get
worse. Crowns are also used to support large fillings when
there is not enough tooth surface remaining to attach a
bridge. Crowns protect weaker teeth from fracturing or
restore fractured teeth and they also cover badly shaped or
discolored teeth.
CHOICES IN THE MATERIAL OF CROWN
Crowns can be made in three different
ways.
1. Gold crowns - Gold is very durable
but obviously not as aesthetically pleasing as porcelain,
which looks like your natural tooth. Gold is more durable
than porcelain on chewing surfaces so it is sometimes
preferable when a molar needs a crown. These alloys are
generally stronger than porcelain and may be recommended for
back teeth.
2. Porcelain fused-to-metal - These crowns have a metal,
sometimes gold, lining inside the porcelain exterior. They
are natural looking because the porcelain is on the outside
and more durable than porcelain alone because of the metal
lining. One caution for these types of crowns is that as the
years pass and your gums start to recede, the metal lining
can show as a dark line along the gum line, thus negating
the aesthetic look that you first wanted to achieve.
As mentioned, because of a metal lining, though covered with
porcelain, on the aesthetic zone or on the front area of the
mouth, If we can avoid using them, All Ceramic or Procelain
Crown would give the best aestheitc result. When placed,
they usually look opaque or "flat" because they do not let
light pass through like a natural tooth. There is often a
tell-tail dark line next to the gum-line that is undesirable
(often the darkness invades the adjacent gum tissue as an
adverse reaction).
3. Composite Crown - Composite crowns
provide a good "temporary" cheaper alternative to porcelain
crowns for the short term. They will eventually wear down or
break and you should expect to have your composite crowns
replaced or "upgraded" to a porcelain or gold crown.
4. Porcelain crowns - the most natural
in appearance because of their transparent properties. They
are strong and durable.
The most beautiful crown for a tooth is,
without question, all-porcelain or all-ceramic. With
porcelain fused to metal crowns, there has to be an opaque
layer put over the metal to block out its color. This makes
it impossible to have a translucent restoration that mimics
the translucency of natural teeth. Only with pure porcelain
or pure ceramic can you have such translucency.
CHOICES IN ALL-PORCELAIN AND
ALL-CERAMIC CROWNS
There are various types of all-porcelain
or all-ceramic crowns. Let's explain the differences between
some of them:
1.The Procera crown - Procera is a
milled ceramic on the inside with a more traditional
porcelain baked onto the outside. The advantage of Procera
is its exceptional strength. However, the milled ceramic
core is opaque white, so many cosmetic dentists feel that it
isn't as natural-looking as the more translucent materials.
An advantage of Procera is that it doesn't have to be bonded
to the tooth but can be cemented with ordinary crown and
bridge cement.
2. The Lava crown - Lava is similar to
Procera, but the milled ceramic on the inside is a more
translucent Zirconia, rather than an opaque white material.
The Zirconia is shaded, and then the final esthetics of the
crown are achieved in the baked-on outer layer. The Lava
crown can also be cemented with traditional techniques.
However, any crown cemented with a traditional crown and
bridge cement is going to be susceptible to a compromise in
the appearance if that cement line ever shows.
3. Feldspathic porcelain is the
standard, traditional porcelain that is used for crowns.
Many cosmetic dentists feel that this is the most beautiful
porcelain.
The Empress crown - Empress is strictly speaking not a
porcelain, but is more like a glass. It can be called a
ceramic material. The Empress material is cast rather than
baked as a feldspathic porcelain crown is. The fit of
Empress is more precise than the baked feldspathic
porcelain. However, the color in Empress is mostly baked on
the outside. Empress can be very beautiful. For appearance's
sake, some expert cosmetic dentists prefer the feldspathic
porcelain, and some prefer the Empress.
4. The Cerec crown - Cerec is are also
milled from a block of very hard ceramic material. What's
unique about Cerec is that the crown is milled by a computer
in the dentist's office rather than in a separate dental
laboratory. Thus, the dentist doesn't have to send out for
it to be made-it can be made on the spot. So, no second
appointment is required, and no wearing of a temporary crown
between appointments. Cerec is milled from a block of
ceramic that is a single color, so it is generally not
considered esthetic enough for demanding cosmetic dentists.
A few exceptional dentists who are artists, however, are
able to custom stain Cerec for front teeth so that they are
truly beautiful. Some even make Cerec veneers that can be
placed the same day. To be precise, Cerec is actually a
technique and not a material. There are several companies
that make ceramic materials for use in Cerec machines.
5.The InCeram crown - InCeram is made of a very dense and very
tough aluminous porcelain. It also has excellent esthetics,
but is more opaque than feldspathic porcelain. InCeram is
also strong enough to be cemented with traditional dental
cement.
There are other types of all-ceramic crowns. We're not going
to list all of them here.
ADVANTAGES AND DISADVANTAGES OF
ALL-PORCELAIN AND ALL-CERAMIC CROWNS
Let's compare all-porcelain with
porcelain fused to metal.
All-porcelain is generally not as strong as porcelain fused
to metal. It has to be bonded to the tooth in order to have
adequate strength for oral function. The bonding technique
is very demanding.
With porcelain fused to metal, the porcelain has to be
opaque in order to block out the appearance of the metal
underneath. They all also eventually develop an unsightly
dark line at the margin where the edge of the crown meets
the tooth.
Some of the all-ceramic systems that
have an inner ceramic core with an outer layer of porcelain
baked on require more tooth reduction. Grinding away more of
the tooth is often not desirable.
Some of the ceramic materials that are
very tough and fracture resistant are also quite abrasive
against the opposing teeth. Of the crowns listed above, the
Empress is the kindest to the teeth it chews against. There
are several factors that need to go into the selection of a
crown material: strength requirements, esthetic
requirements, the abrasivity of the material against the
opposing teeth, and the skills of the dentist.
There is not a single crown that is clearly
superior for all situations. Many cosmetic dentists will
have several types that they will use, each for a different
situation.
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