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

Removal of infected dentine
It is necessary to eliminate any direct source of canal contamination
and potential pathway of contamination from the mouth. All unsound
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Principles of endodontics


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restorations and tooth structure should be removed and cavities on
the axial wall of the crown thoroughly excavated and, if below the
rubber dam, sealed before isolation. If the pulp chamber is opened at
this stage it is helpful to protect the floor and the opening(s) to the root
canal(s) with a gutta-percha or cotton pellet, which fills the pulp
chamber, before placing sealants or new restorations. Total removal
of extensive restorations may, however, be undesirable as this could
compromise support from weakened residual coronal tissues and
make isolation more difficult.
Technique
This may be divided into stages:
• Initial access cavity outline and isolation
• Pulp chamber entry
• Pulp chamber roof removal
• Preparation margin modification
• Cavity refinement
• Irrigation
• Canal orifice opening
Initial access cavity outline and isolation
The initial access stage may be executed before placement of rubber
dam (required for isolation) in order to aid orientation.
Pulp chamber entry
Careful reference to preoperative radiographs will give an indication
of pulp size or position. Long shank bur designs improve visibility
but it is essential that landmarks on the floor of the pulp chamber 
are maintained. The dust of enamel, dentine or dressing created at this
stage may be gently cleared using a three-in-one syringe and aspirator
across the mouth of the cavity. Air (or fluids) under pressure should
not be blown into the pulp chamber because impaction of debris into
the canal may cause blockage and there is a risk of air embolus.