Crowns and Bridges
Crowns
When a tooth is heavily decayed it is more likely to fracture
and lose considerable tooth substance. The greater risk is that a
fracture line may go below the margin of the gum which makes
restoration more difficult or near impossible.
Crowns may be made from several different materials, gold and
porcelain being the most common types.
Gold is usually used on the back teeth, as it has several
advantages over porcelain teeth.
Gold is strong in thin section and less tooth needs to be
drilled away before taking the impression and fitting the
crown.
The lab technician finds it easier to use gold as it shrinks
less when cast and is easier to polish. Crowns of porcelain shrink
when cast and the technician has to estimate this when making the
crown.
Porcelain is usually always used for the front teeth but may be
used for the back teeth. This material can be made to appear very
natural though several factors affect this and are outlined
below;
Some porcelain crowns have metal inside which gives strength and
support to the porcelain. This acts as a barrier for light and
gives the crown a dull colour. On posterior teeth this won't be
noticed but in the front of the mouth it can occasionally be a
problem as the tooth looks duller than the natural teeth.
Bridges
A bridge allows the dentist to replace lost teeth without the
use of a denture or dental implant. Basically a false tooth is held
in place by being attached to a tooth next door. The disadvantage
is that the teeth next to the space have to be prepared in a
similiar way to a crown in order to accept the bridge. If these
teeth already have crowns or big restorations then this is not a
problem, the major concern however is when these teeth have small
or no restorations (fillings). One compromise is the 'acid etched
bridge', with this type a fine ledge is placed on the back of the
adjacent teeth.
One disadvantage of a bridge is that the patient should wait
three months before placement as the 'gum' shrinks after a tooth is
extracted. If the bridge was fitted early a gap would appear
underneath the pontic (the false tooth). At the back of the mouth
this may not be a problem, at the front of the mouth however this
may appear as a black line along the gum.
For more information on crowns and bridges please contact us.
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