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Dental
Crowns
Dental
Crowns for Your Teeth
As
we age, many of us find ourselves with
teeth that are no longer structurally
sound. Root canals, lost fillings, decay
below a filling, chipping and cracking
of the enamel are all things that can
lead to large scale defects in a tooth's
surface. When the entire surface of
the tooth is a problem, but the root
system is intact, a crown might be just
what the dentist orders.
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What
are Tooth Crowns?
Grinding
your teeth, an improper bite, age, fillings
and tooth decay can all be contributing
factors in the wearing down, cracking
or breakage of your teeth. Dental crowns
cover the entire visible surface of
your affected tooth and add strength,
durability and tooth stability.
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Who
is a candidate for Tooth Crowns?
Grinding
your teeth, an improper bite, age, fillings
and tooth decay can all be contributing
factors in the wearing down, cracking
or breakage of your teeth. Dental crowns
cover the entire visible surface of
your affected tooth and add strength,
durability and tooth stability.
Dr
Phillip F. Ajaje will usually be able
to spot problem areas in your mouth
that might lead to tooth damage and
a need for crowns. Chewing patterns
play a big role as well. By selectively
grinding the tips of your middle and
back teeth (called cusps) will alter
your bite to reduce the stress on at-risk
teeth.
In
other instances, crowns are used to
replace a actual missing tooth. These
crowns are anchored to the teeth on
either side, with a bridge section connecting
the two crowns. Instead of bridges,
single tooth dental implants may be
used that eliminate the need for supporting
the crowns.
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How
are Tooth Crowns Attached to your Tooth?
Dr
Phillip F. Ajaje will make an impression
of the tooth and a dental laboratory
will create the crown. You will typically
leave the office with a temporary crown
to wear while the permanent crown is
being made - this takes about two weeks.
The permanent crown is then cemented
onto your tooth. Typically, only two
visits are required for this part of
the procedure. Often, a preliminary
restoration of your tooth may be needed
before a crown can be placed. To stabilize
your tooth, a filling must first be
put in place prior to placing a crown
due to the loss of original tooth structure.
Tooth crowns usually last ten to fifteen
years.
Be
sure to discuss with your cosmetic dentist
that the cement colour used for your
permanent crown will be the same as
used for your temporary crown. A try
in paste is used for this purpose. The
colour of the cement does affect the
overall colour of a porcelain crown,
so this needs to be discussed long before
your temporary crown is placed.
In
some cases your cosmetic dentist may
choose to use a Flipper instead of a
temporary crown. A Flipper is a false
tooth to temporarily take the place
of a missing tooth before the permanent
crown is placed. A Flipper can be attached
via either a wire or a plastic piece
that fits in the roof of your mouth.
Flippers are meant to be a temporary
solution while awaiting the permanent
crown.
As
the illustration above indicates:
1)
a tooth presents with a large cavity
or broken portion of tooth structure.
This tooth is vulnerable to further
decay and fracture.
2)
the dentist will 'prepare' or shape
the tooth for a crown. In preparing
the tooth, the dentist will incorporate
resistance and retention features in
order for the crown to stay in place.
These features vary in every tooth and
are determined by the type of bite you
have. An impression of the prepared
tooth is taken and sent to a dental
laboratory for processing.
3)
a crown is then fabricated in the dental
laboratory with instruction from the
dentist such as type of crown and shade
or colour of the tooth. The crown is
then cemented in place by the dentist.
A temporary crown is placed while the
laboratory is constructing the crown.
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Types
of Tooth Crowns
There
are basically 2 types of crowns, those
made of ceramic crowns and metal-ceramic
crowns. Metal-ceramic crowns are extremely
durable and are normally used in molars,
where the forces from chewing and grinding
are most prevalent. Ceramic crowns are
used primarily for front teeth, since
they can best resemble the natural tooth
colour.
All
Porcelain Crowns
The
new reinforced resin or bonded all-porcelain
type of crown has the nicest appearance.
This crown can be made from pure ceramic
or a new reinforced composite resin,
and is almost indistinguishable from
natural teeth. The new bonding technology
involved provides an exceptional bond
your tooth. It is metal-free, and thus
satisfies the needs of patients with
metal sensitivities. When correcting
your back teeth with bonding, the cosmetic
dentist will perform a tooth coloured
onlay. This type of procedure is used
to correct only those parts of the tooth
that are in need. This is a metal-free
procedure.
Porcelain
fused to Metal Crowns
For
a very natural appearance, porcelain
fused to metal crowns are the answer.
However, they have a metal substructure
and require an opaque below the porcelain.
This can make the translucency of natural
teeth difficult to replicate. Occasionally
a darker line will be visible at the
edge of the crown, near to your gum
when it recedes with age.
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Types
of Porcelain
There
are basically two types of porcelain
you're likely to hear and read about
most - the felspathic
and pressed ceramic porcelains.
The felspathic type is the original
method that has been around for 20 years.
A Ceramist in a dental lab bakes porcelain
onto tin foil and then heats it in an
oven. The Ceramist is able to create
tints and opaques inside the porcelain
to give the natural look we seek.
Pressed
ceramic is created from
a single ingot. The single ingot is
milled in one piece to create the desired
shape. The stains and opaques are applied
only to the surface of the porcelain
to give a natural look.
Zirconium
oxide - One of the most
difficult areas in dentistry today is
the restoration of dental structures
with biocompatible materials that are
strong enough to withstand the forces
of chewing (500-1000lbs pressure on
molar teeth). Recent technology from
Germany now offers a material that has
overcome most of the pitfalls of present
day products. Patients now have a choice
of a material that is esthetic, strong,
pure, biocompatible and capable of being
used for single and long span dental
bridgework. That material is called
Zirconium oxide.
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Pros
and Cons of Dental Crowns Types
Tooth
crowns in general add a good deal of
strength to weakened or worn teeth.
Depending on your habits and the condition
of your gums, there can be some drawbacks.
Your cosmetic dentist will advise which
is best for you given many factors,
including how important appearance is
to you. The following are the advantages
and disadvantages of the most common
crown types.
Advantage:
Porcelain crowns or new reinforced resin
are considered to be the most aesthetically
pleasing, as it is so easily matched
in colour to the surrounding teeth.
Disadvantage:
The thickness of the porcelain required
for pleasing aesthetics also requires
that more tooth structure needs to be
removed. It is more difficult for your
cosmetic dentist to get an ideal fit
where your gum meets the crown. Gingival
inflammation appears to be more common
with porcelain crowns than gold crowns.
All-porcelain crowns require a higher
skill level from your dentist and lab.
- Porcelain
Fused-to-Metal Crowns
Advantage:
Porcelain fused-to-metal crowns
have a very natural appearance.
Disadvantage:
They have a metal substructure and require
an opaque below the porcelain. This
can make the translucency of natural
teeth difficult to replicate. Occasionally
a darker line will be visible at the
edge of the crown, near to your gum
when it recedes with age.
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