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

Fig. 6.4
Working impression.
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Chapter 6
agents. These chemical agents may be used alone or may also be used
in conjunction with retraction cord. Many chemical agents have been
used, including alum, sympathomimetics such as racemic adrenaline,
aluminium chloride and ferric sulphate. All these chemicals have 
the potential to traumatise gingival tissues
16
and may cause necrosis
of sulcular epithelium. Adrenaline has possible systemic effects, and
has been shown to cause cardiovascular disturbances and is better
avoided when halothane is being administered during general anaes-
thesia or when an adverse reaction with concurrent conditions or
medication may occur (e.g. beta-blockers, antihypertensives, tricyclic
antidepressants, uncontrolled hyperthyroidism, etc.) Agents that con-
trol exudates by promoting clotting, such as ferric sulphate, appear to
be safe in small quantities, though these agents can cause staining of
the tooth and gingival tissues and should be used with care.
Electrosurgery
This is the term used to describe the procedure whereby high fre-
quency electrical energy is used to cut and coagulate soft tissues. 
An active electrode tip directs energy, and various tips are available.
Use of a narrow tip leads to localised tissue dehydration and dis-
integration (cutting), whereas a broad tip spreads current and can be
used to produce coagulation. A passive electrode (often termed a
grounding plate) is a large plate placed remote from the operating site
and allows the current to pass through the patient’s body from the
active electrode. Most electrosurgery units are capable of producing a
variety of waveforms. A fully rectified and filtered waveform results
in good cutting and minimal shrinkage but poor haemostasis (usually
labelled ‘cut’). A fully rectified, not filtered waveform will give good
haemostasis as well as cutting tissue with little shrinkage (usually
labelled ‘cut/coag’) and is versatile. A partially rectified waveform will
give inefficient cutting and causes tissue shrinkage but is useful with a
ball-ended electrode to control haemorrhage (usually labelled ‘coag’).
Electrosurgery can be used for gingival retraction and for access 
to subgingival margins, though as with most techniques there are a
number of advantages and disadvantages:
Advantages:
• Easy retraction of multiple abutments
• Clear vision of finishing line
• Increased bulk of impression material
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Indirect restorations – further considerations


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• Decreased operative time
• Haemostasis
• Predictable healing, little discomfort
Disadvantages:
• Odour/taste (high volume suction is required)
• Technique sensitive
• Little tactile feedback
• Should not be used on or near patients with pacemakers
• Must not be used near flammable gases!
• May cause trauma to the tooth
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or adjacent supporting tissues
with poor technique
• Equipment cost
• Should not be used with topical local anaesthetic (which is
flammable)