Operative dentistry aje qualtrough, jd satterthwaite la morrow, pa brunton

CREATION OF INTEROCCLUSAL SPACE
In order to place an indirect restoration, particularly an extra-coronal
restoration, then the tooth usually has to be reduced to provide
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Chapter 6
sufficient interocclusal clearance for the restorative material (i.e. space
between the tooth requiring a restoration and opposing teeth when
the remaining teeth are together in the intercuspal position). This
space in the intercuspal position is required at the fossae regions and
for the supporting cusps. Although it is usually necessary to reduce
the non-functional cusp, this is not universally so. Space for the non-
functional cusps (remember their position in excursion) is determined
by the anterior and posterior determinants of the functional occlusion
(see Chapter 1) that in turn determine the degree of separation of
opposing teeth during excursive movements. These are:
• Condylar guidance
• Anterior guidance
• Curves of Spee, Wilson, Monson
• Occlusal plane angle
• Non-working interferences (especially if on the tooth to be
restored)
• Premature contact (and slide from RCP to ICP on tooth to be
restored)
In some situations, it may be possible to encroach on the space
available during disclusion of opposing teeth rather than reducing a
non-functional cusp, though great care is required not to introduce 
a non-working interference or to produce an unaesthetic restora-
tion and this approach alone is seldom enough to overcome space
problems.
In some situations in which space is limited, thin adhesively
retained metal-cast restorations may prove useful, as described previ-
ously. In other situations, this approach cannot be used, for example
when preparation would result in exposure of the pulp, when only
very short preparations are possible with little retention or when
space for the restorative material is at a premium. In these situations 
it is usually necessary to create more interocclusal space for the
restorative material without unnecessary tooth reduction. This may
be achieved through orthodontic movement of the tooth to be
restored or by increasing the occlusal vertical dimension.