 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. |