根管预备（Root canal preparation）.docVIP

根管预备（Root canal preparation） Step by step (Step-back) technical preparatory principles: - 1.: determine the working length with the former method. - 2., root tip preparation: the initial file is bent into the same shape as the root canal curvature. Gently insert the root canal and rotate the instrument to expand the root canal. Rotate clockwise 30~60 degrees, then gently press downward, rotate 30~60 degrees counterclockwise, and finally pull out of the appliance. This cutting pattern is similar to that of a watch spring. The instrument that exits the root canal is inserted into the root canal again after cleaning. Use the same cutting mode to enlarge the root canal until the instrument reaches the operating length without resistance. The big one is used to enlarge the root canal. - During the preparation, each instrument was withdrawn or replaced, and the root canals were alternately washed with saline and 3% hydrogen peroxide (recommended using 2.5% sodium hypochlorite and 17%EDTA solution; 5# syringe needle). The maximum number of instruments for root tip preparation should be 2~3 larger than the initial file. For example, when the sharp file was 20#, the main tip file should be 35#. To prevent root canal obstruction during preparation, small instruments are inserted into the root canal before removal of the larger instrument, removing dentin fragments from the root canal and flushing and lubricating the root canal walls with the rinse fluid. Take the root canal working length 20mm and the root canal of 15# as the example, the order of the instrument entering the root canal is 15# - 20# - 15# - 25# - 20#, and the operating length of each device is 20mm. - 3. step back preparation: after the root tip preparation is completed, the apical and middle of the root canal are opened by means of each additional number and the working length reduced by 1mm (0.5mm), that is, step back gradually. In step by step preparation, the main tip file should be inserted into the opera