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

Pulp chamber roof removal
The cavity is then opened up to afford smooth-walled access to the
pulp cornua. Extension of the preparation cervicolingually, especially
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in lower incisors, improves access to the buccolingual extremities of
an elliptical pulp space (Figs 3.3, 3.4). The use of magnification in the
form of loupes or an endodontic microscope has very much enhanced
the ease of identification of root canals. Another aid is the use of ultra-
sonically powered instruments used at low power and without water
60


Chapter 3
Fig. 3.3
Axial access for a lower incisor. (Straight line access to the root canal
requires extension of the access to the incisal edge.)
Fig. 3.4
Coronal opening.
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Principles of endodontics


61
cooling. Careful use of specially designed tips facilitates the widening
of the opening of root canals that may be partially obliterated by
calcific material.
Preparation margin modification
Refinement of the preparation margins is carried out, if necessary, to
facilitate reproducible positioning of instrument handles against a
reliable reference point. Location of the pulp chamber may prove to be
difficult under prosthetic crowns. Alignment of the root relative to the
crown may be confirmed by imaging techniques, by palpation and by
subgingival probing.
Cavity refinement
Creation of pulpally converging walls on opposing aspects of the
access cavity is achieved by the use of a safe-ended, non-cutting bur
(e.g. a Batt bur) which will prevent damage to the floor of the pulp
chamber.
Irrigation
Copious irrigation with sodium hypochlorite (NaOCl) will arrest any
haemorrhage, assist in the removal of pulpal remnants (dissolves
organic material) and debris obstructions, and assist in the preven-
tion of extension of contamination from crown to root apex (i.e. acts 
as a disinfectant). A variety of concentrations of sodium hypochlorite
(from 0.5% to 5%) are advocated. Higher concentrations act more
quickly, although the risk of tissue irritation, if the irrigant is extruded
past the apex and into the peri-radicular tissues, is greater. Lower 
concentrations are also antibacterial, and are less irritant to tissues,
but require longer contact times and greater volumes.