CLEANING AND SHAPING
Objectives of cleaning and shaping
The objectives of cleaning and shaping are to:
• Create a continuously tapering preparation.
• Maintain the original anatomy.
• Retain the position of the apical foramen.
• Keep the foramen as small as possible.
Step-down is now regarded as the preferred preparation technique
5
.
In this method, the coronal part of the canal is prepared before the
apical region. The canal working length is determined following the
step-down stage and before apical preparation is commenced.
The outcome of this approach to treatment is improved for the
following reasons:
• There is better tactile control of instruments in the apical third.
• Pre-enlarged canals can hold a greater volume of irrigant to
enhance cleaning.
• Pre-enlarged canals promote the removal of dentine mud.
• Post-treatment problems are reduced as the bulk of bacteria and
their toxins will have been removed.
• Identification of the foramen is facilitated.
It is useful to remember that most teeth range from 19 to 25 mm
in length. Most crowns are about 10 mm, and most roots range from
9 to 15 mm. The root may be divided into thirds: coronal, middle and
apical.
Summary of cleaning and shaping procedures
• Preoperative radiograph
• Administration of a local anaesthetic
• *Rubber dam placement
• *Access cavity
• Identification and widening of canal orifices
• Investigation of canal patency
• Coronal two-thirds shaping
• Working length determination (using radiographs and/or an apex
locator)
• Apical shaping
• Mid-third shaping and canal refinement
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Chapter 3
POOC03 02/18/2005 04:33PM Page 68
Principles of endodontics
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