Home Dentistry Articles Crown (dentistry)
A crown (sometimes incorrectly called a cap)
is a tooth form produced by a dental technician. Materials used
to make crowns include precious metal alloy, semiprecious metal
alloy, porcelain, or a reinforced aluminosilicate-type ceramic
system such as Procera.
Why use a crown?
A very badly damaged tooth may be difficult
or impossible to restore to correct form and function using
a direct dental restorative material such as amalgam or dental
composite, since these materials are placed in the damaged tooth
and carved to shape by the dentist in the mouth, and thus have
limited strength. In such cases, the tooth may require an indirect
restoration made outside the mouth by a dental technician, who
can work to produce a customised tooth shape in the chosen material
that will fit the patient's damaged tooth exactly, somewhat
like a thimble fits over a finger to protect it.
Process of applying a crown
- Patient presents with badly damaged tooth. Tooth may be
restored using a direct filling material to act as a core
for the crown.
- Dentist prepares the tooth using a dental drill, removing
some tooth and core to allow sufficient thickness of crown
material to cover the damaged tooth and restore its strength.
At this stage the dentist will also prepare the margins
of the crown preparation ie. the join between the natural
tooth and the crown. There are several designs in the literature,
the common types being a chamfer (typically used for gold
and other metal crowns), and a shoulder (used for porcelain
where thickness is important for good strength and aesthetics).
- Dentist takes an impression of the teeth and records
how the teeth meet. Typically a polyvinylsiloxane putty
and a lightbody wash system are used to record the shape
of the prepared tooth. Dentist chooses the shade and material
of the crown, and writes a prescription for the technician
- A temporary crown is fabricated by the dentist and placed
over the prepared tooth.
- The models of the teeth are sent to the dental laboratory
where the technician makes the crown according to the prescription.
- The finished crown is returned to the dentist for fitting.
The crown is cemented over the damaged tooth, using a luting
cement, restoring the tooth to a good strength and function.