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Chapter 5
cure may not be achieved in substantial core build-ups.
Chemical-
cure or dual-cure resin composites (the latter having the advantage
of ‘command set’) have an advantage in that those portions of the
material not exposed to the curing light will still undergo polymerisa-
tion due to the chemical cure. However,
they may undergo increased
discoloration (due to the tertiary amine activator
7
) compared with
light-cured resin composites and thus should be used with caution
in anterior teeth in which non-opaque
aesthetic restorations are
planned. Some resin composites are marketed specifically for core
build-up, are coloured and have advantages over tooth-coloured
composites. It has been suggested that because of water sorption
and
expansion, additional die relief should be provided during
construction, or impression taking should be delayed after pre-
paration to prevent discrepancy between the working die and the
prepared tooth
8
.
Glass ionomers and resin-modified glass-ionomer cement
Traditional glass-ionomer cements are only suitable for use as a
space-filling core, where they will not be subjected to any stresses, as
they are inherently weak materials. Several glass-ionomer materials
are marketed specifically for use as a core
build-up material such as
RmGIC. They bond to dentine, release fluoride, have comparable
thermal behaviour to dentine, can be
made a contrasting colour to
tooth (e.g. blue) and are easy to prepare, although the long-term
behaviour of these materials is not well documented. Water sorption
and expansion are higher with these
materials than with resin
composites and, for this reason, after preparation there should be a
delay before impression taking. At present,
their use as a structural
core may be questionable. However they may eventually become the
materials of choice with further developments.
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