The ultimate objective of endodontic technique is the elimination of the root system as a source of infection and inflammation to the apical periodontium after irreversible pulp pathosis. The most desirable way to render root canals innocuous is to clean and shape them, to eliminate bacteria and tissue debris from within them, and then to obliterate them by means of a dense three-dimensional root canal filling. Accessory canals are present in practically all teeth. Many accessory canals are very small and calcify spontaneously during chronic pulp irritation, and others contain too little tissue to be clinically significant. Often, however, accessory canals are of considerable size, and, where the tissue within them becomes necrotic or infected, they may contribute to lateral root abscesses unless sealed off from the periodontal ligament. Root canal filling procedures should be directed toward the filling of significant lateral canals as well as the filling of main root canals (Fig. 8). Many techniques have been used to obturate root canals successfully. Most of these techniques employ either silver cones or gutta percha in some form. When used well, all of these techniques are valuable; when abused, no technique can succeed. The difficulty of adapting a silver cone to a less than geometrical round foramen sets certain potential limitations upon the use of silver cones in all cases. Likewise, small dimensional changes inherent in the use of gutta percha and a solvent, as well as certain problems of apical adaptation of the gutta percha when no solvent is used, encourages the evolvement of a technique by means of which gutta percha is rendered plastic without the use of solvents. Vertical condensation of warm gutta percha produces consistently dense, dimensionally stable, three-dimensional root canal fillings. Lateral canals are filled with extraordinary frequency, often with gutta percha, sometimes with cement. The final test of a root canal filling is its capacity to seal off the root canal system from the periapical tissues. The tissue compatibility of almost all commonly used root canal filling materials is very high, and for decades bone has been demonstrated to be laid down in close proximity to all of them. Overfilling, while not necessarily beneficial, will not prejudice the outcome of a case or prevent healing. Overfilling must be distinguished from overextension of underfilled cases.
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