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

Physical gingival retraction
Physical retraction of the gingivae for impression taking is primarily
achieved with retraction cord. This is a fine cord that is placed into the
gingival sulcus and left in situ for a short time in order to ease the
marginal gingival tissues away from the preparation (Figs 6.3, 6.4).
Braided and knitted cords are available, knitted cords having the
advantage that they are less likely to unravel. Other materials are also
available to retract gingival tissues physically, including synthetic
polymers (Merocel)
13
and expanding synthetic materials
14
.
The length of time that the cord is left in place is important; too short
and the gingivae will not be adequately retracted, but too long may
result in damage to the sulcular epithelium
15
. Only light pressure
Fig. 6.3
Retraction cord in situ.
POOC06 02/18/2005 04:36PM Page 140

---

Indirect restorations – further considerations


141
should be used to place the cord as excess packing force may push 
the cord beyond the periodontal attachment into supra-alveolar con-
nective tissue which will be too deep to retract the gingivae and may
result in trauma. It may be advantageous to place two cords, with 
a fine cord placed first. This will remain in place during impression
taking. This has the advantage of controlling gingival exudates or
haemorrhage that may persist when a single cord is used; how-
ever great care must be taken not to insert the cord too deep and to
remember to remove the cord after the recording of the impression.
When the impression material is ready, the cord may be removed 
or left in situ if the margin is clearly visible. Care should be taken if 
the cord is removed as the sulcular epithelium may be damaged, 
especially if the cord is removed dry. Trauma should be avoided as it
may lead to haemorrhage from the gingival tissues, thus making it
impossible to obtain an accurate impression of the margin. In addition,
significant trauma to the gingival tissues may result in apical migra-
tion of the gingival margin and can lead to unaesthetic visible margins.
Chemical agents
Several chemical agents are available for control of gingival exudates
and haemorrhage, and are essentially either vasoactive or clotting