112
Chapter 5
Space-filling core
When
much coronal dentine remains, the role of a core is simply to
fill out any undercuts and give an appropriate shape that will
provide adequate retentive and resistance form (described later).
The restorative material simply acts to prevent or ‘block out’ any
undercuts to the path of insertion of the intended indirect restoration.
This situation commonly arises when an
intra-coronal restoration
(i.e. an inlay) is planned to replace a previous direct restoration. The
preparation will have to be modified to eliminate the undercuts;
extending the preparation would be unnecessarily destructive com-
pared with placement of a core material to block out the undercuts.
Similarly, the same approach can be taken
to give smooth axial walls
when an extra-coronal restoration such as a full coverage crown is
planned.
In the above example, the functional
demands and stresses encoun-
tered by the core material will be minimal. The mechanical properties
of a core material in this situation are not critical,
and the material
choice is largely determined by secondary factors such as ability to
bond to tooth structure, cariostatic properties
and ease of handling
(e.g. command set).
Fig. 5.3
Types of core restorations, (a) structural and (b) space-filling.
POOC05 02/18/2005 04:36PM Page 112
Structural core
When a large amount of coronal dentine has been lost, it is more likely
that an extra-coronal full-coverage restoration will be planned. The
core material will replace a substantial part
of the clinical crown and
will form the bulk of the final preparation. In this case, the core mater-
ial will be subjected to significant functional
demands and stresses,
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