23. To do an instrumental treatment of root canal.
«Crown-Down» method
“Crown-down” method envisages root canal treatment that starts from canal orifices to apical hole with a gradual decrease in instrument diameter (e.g. from №40 –№ 10). At first is prepared the coronal part of the canal before the apical part. It allows improved access for the flow of irrigant solution within the canal; it reduces the probability of apical extrusion of infected material as most of the canal debris is removed before apical instrumentation takes place. Hand endodontic instruments are used in sequence (K-reamer; K-file; H-file).
«Step-Back» method
“Step-back” technique: envisages treatment from the apical hole to canal orifices with gradually increasing of instrument diameter (e.g. from №10 -№ 40). An apical part of the root canal is prepared first and the canal is then enlarged from apex to crown part of root. The most important part of the Step-back preparation is the reuse of files; one size smaller than the last one (recapitulation) used (e.g. № 0,8; 10; 0,8; 15; 10; 20; 15; 25). Blockage of canals may occur using this technique, and irrigation can be difficult. Hand endodontic instruments are used in sequence (K-reamer; K-file; H-file).
24. To select instruments for instrumental treatment of root canals.
Hand endodontic instruments: ▲-K-reamers, ■ - K-files, ● -H-files (K-reamers and K-files works with rotation movement ¼ - ½ of a turn and retraction; H- files works with rasping action and retraction (up and down), color coding - means size of instrument). Barbed broaches -- is used to remove pulp from root canals.
25. Root canal sealing by hardening pastes.
Before starting a root canal sealing, the size of a rotary paste -filler (like last file size) should be chosen. After paste is mixed: 1) - the rotary paste -filler should be dipped in a prepared sealing material, some amount of material should be taken. 2) root canal-filler is placed in the root canal, by careful movement, to the apical part of canal; after reaching an apical part, the canal-filler is taken back to the middle of root’ canal length. 3) - a rotating starts under the speed of 600-800 rpm and sealing material is distributed into the canal space, providing obturation. After 10-15 seconds of rotating, a rotary paste -filler (which is still rotating) should be removed from the root canal.
26. Root canal sealing by cold lateral condensation of gutta-percha.
1. Select a GP master point to correspond with the master apical file instrument. This should fit the apical region snugly at the working length.
2. Coat walls of canal with sealer using a small file.
3. Insert the master point, covered in sealer.
4. Condense the GP laterally with a finger spreader to provide space into which accessory points can be inserted until the canal is full.
5. Excess GP is cut off with a hot instrument and the remainder packed vertically into the canal with a cold plugger.
27. To seal root canal using method of vertical condensation of gutta-percha.
In this technique the GP is warmed using a heated instrument and then packed vertically. A good apical stop is necessary to prevent apical extrusion of the filling, but with practice a very dense root filling can result.
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