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

Temporary cementation
There are several materials available for temporary cementation.
Essentially any temporary cement must be weak enough to allow easy
removal of the temporary restoration and residual cement from the
preparation, yet strong enough to retain the temporary restoration
while the definitive restoration is being constructed. The choice of
material is based on the retention available in that a preparation with
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Indirect restorations – further considerations


139
poor retentive form will require the use of a stronger temporary
cement. In addition, the constituents of the temporary cement should
not interfere with the final cementation.
It is often suggested that eugenol-containing temporary cements
may reduce bond strengths obtained with definitive resin-based
cement
7,8
(the eugenol acts as a plasticiser and weakens the bond)
though this has been questioned
9,10
. Various eugenol-free temporary
cements are available for routine use, and it is uncommon to require a
stronger cement. A close fitting rigid temporary restoration (e.g. metal
and acrylic provisional restoration) may be very difficult to remove 
if these cements are used and most can be modified by the addition 
of a small amount of petroleum jelly.
IMPRESSION TAKING
When an indirect restoration is provided, it is usual to take an impres-
sion of the prepared tooth and use this impression to create a model
on which the restoration is constructed. Obviously, the restoration
can only be as accurate as the impression, and the influence of the 
gingival tissues and choice of material for this impression are critical.
Gingival management
Periodontal disease should be controlled such that the state of 
the periodontal tissues is optimised before any procedure and 
maintained thereafter. Untreated periodontal disease compromises
success of restorative treatment and poor restorative treatment leads
to adverse effects on the periodontium. The fit and quality of restora-
tions are of paramount importance – defective margins are directly
related to the severity of periodontal disease
11,12
. When margins of a
preparation are above the level of the gingivae, impression taking 
is relatively straightforward. However due to the very nature of 
teeth that require such restorations having had multiple previous
restorations, it is usual that the margins are close to, at, or even below
the level of the gingivae. In this situation, obtaining an accurate
recording of the margin of the preparation becomes more difficult 
and not only is it necessary to record the margin, but it is also neces-
sary to record unprepared tooth beyond the margin in order that 
the restoration can be constructed with the correct emergence profile.
In order to achieve this, the gingival tissues require careful handling
and will need to be retracted, i.e. moved away from the margin while
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Chapter 6
the preparation is taken, and gingival exudates or haemorrhage must
be controlled. There are several ways in which this may be achieved,
including use of:
• Physical gingival retraction
• Chemical agents
• Electrosurgery
• Rotary gingival curettage