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Preparation of the Root Canal System
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INTRODUCTION Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18:269-96. ♦ Each root canal system is different from another; therefore, no two root canal preparations should be exactly alike. Certain constant principles for cleaning and shaping, however, are carried out in every case: ♦ The root canal preparation should develop acontinuously tapering funnel from the root apex to the coronal access cavity. ♦ The cross-sectional diameter of the preparation should be narrower at every point apically and wider at each point as the access cavity is approached. ♦ The preparation should occupy as many planes as are presented by the root and the canal. The preparation should flow with the shape of the original canal. ♦ The apicalforamen should remain in its original spatial relationship both to the bone and to the root surface. The apical opening should be kept as small as is practical in all cases. Ruddle C. Cleaning and shaping the root canal system. In Cohen S, Burns RC (eds). Pathways of the pulp. 8th ed. St. Louis: CV Mosby Company, 2002:231-273. Clinical Objetives: “Start with the end in mind” ♦ Pretreatment – ensurerestorability ♦ Access for Success – remove the pulpal roof entirely, obtain straight line access, visualize all orifices without moving the mouth mirror, achieve axial walls with adequate taper and access the canals. Mechanical Objectives: ♦ Continuously tapering preparation from the chamber to the foramen. ♦ Maintain original anatomy, consider curvatures and root concavities. ♦ Maintain theposition of the foramen. ♦ Keep the foramen as small as practical. The foramen is circular shaped therefore doubling the file size increases the diameter fourfold. (pr2 ) Concepts and Strategies for Canal Preparation: The majority of teeth range from 19-25mm, the crown is usually about 10mm, therefore the root lengths range from 9-15mm. This length can be divided into thirds; coronal, middle and apical.♦ Coronal 2/3rds Preenlargement: o Increases tactile perception and control of the apical third. o Enhances cleaning by allowing a greater volume of irrigant in the canal. o Removes the bulk of debris, decreasing irritants potentially pushed past the apex.

♦ Apical 1/3rd Finishing: o Scout the terminus – small files and radiographs will confirm the anatomy prior to any iatrogenic mishaps. oEstablish patency, avoid packing the apical terminus with dentinal mud. Establish working length with both EAL’s and radiographs. Walton RE, Rivera EM. Cleaning and shaping. In Walton RE, Torabinejad M (eds). Principles and Practice of Endodontics. 2nd ed. Philadelphia: WB Saunders, 1996:181-233. 1. Major objectives of access preparation ♦ Straight-line access into the canal system and comple teunroofing of the pulp chamber, this aspect is often neglected in anterior teeth. ♦ Removal of all caries and defective restorations ♦ Creation of divergent walls to provide a positive seat for the temporary restoration and to maximize direct visibility of the canal system ♦ Conservation of tooth structure 2. Special considerations during access preparation ♦ Caries, defective restorations, and...