Root-canal sealing Tools for root canals obturation ：根管充填根管密封工具.ppt

Thermomechanical compaction This involves a reverse turning (e.g. McSpadden compactor or GP condenser) instrument which, like a reverse Hedstroem file, softens the GP, forcing it ahead of, and lateral to the compactor shaft. This is a very effective technique, particularly if used in conjunction with lateral condensation in the apical region, but requires much practice to perfect. Thermoplasticized injectable GP (e.g. Obtura, Ultrafil) These commercial machines extrude heated GP (70-160°C) into the canal. It is difficult to control the apical extent of the root filling, and some contraction of the GP occurs on cooling. Useful for irregular canal defects, e.g. following internal root resorption. Coated carriers (e.g. Thermafil) These are cores of metal or plastic coated with GP. They are heated in an oven and then simply pushed into the root canal to the correct length. The core is then severed with a bur. A dense filling results, but again apical control is poor and extrusions common. They are expensive and difficult to remove. Once the filling is in place the tooth will need to be permanently restored, provided the follow-up radiograph is satisfactory. Fillings that appear inadequate radiographically may be reviewed regularly, or replaced, depending upon the clinical circumstances. THE CORONAL SEAL Regardless of the technique used to obturate the canals, coronal microleakage can occur through seemingly well- obturated canals within a short time, potentially causing infection of the periapical area. A method to protect the canals in case of failure of the coronal restoration is to cover the floor of the pulp chamber with a lining of glass ionomer cement after the excess gutta-percha and sealer have been cleaned from the canal. Glass ionomers have the intrinsic ability to bond to the dentin, so they do not require a pretreatment step. The resin-modified glass ionomer cement is simply flowed approximately 1 mm thick over the floor of the pulp chamber and polymer