CLEANING N SHAPING methods advantages and disadvantages

Editor's Notes

• #4: Permits vertical pluggers to fit freely with in R C system and to generate hydraulics required to transform and capture maximum cushion of GP and microfilm of sealer into all foramina. Facilitates 3 dimensional cleaning by allowing easy access to files and irrigants during shaping process.
• #7: Herbert Schilder taught endodontists to think and operate in the third dimension. Schilder's five mechanical objectives for successful cleaning and shaping were first introduced to the endodontic literature 50 years ago.
• #15: During the inward stroke, the cutting force is a combination of both resistance to bending and the apically directed hand pressure. These two combine at the junctional angle of the instrument tip and gouge the curving canal wall very quickly.
• #16: The gouge imparts a shape that does not allow even a small instrument to pass beyond it. This procedural error can occur anywhere beyond the point where a canal begins to curve.
• #17: Canal ledging is responsible for more short endodontic obturations than any other procedural errors. The withdrawal or pull portion of this action produces very little potential for canal wall damage.
• #22: The pull motion strips out treads started by the one fourth turn to the right motion. Angles up to a half turn have been advocated. This can be an effective motion if the instrument is not forcefully pushed toward the apex and the preparation depths are allowed to diminish with each subsequent instrument.
• #26: Balanced force instrumentation has been demonstrated to extrude no more debris through the apex than other techniques of canal preparation. Balanced force instrumentation is specifically designed to operate K-type endodontic instruments and should not be used with Broach type or Hedstrom type instruments, since neither possesses left-hand cutting capacity.
• #32: Also called as “single length technique” – recently gained popularity with Protaper and Mtwo rotary instruments. Canals shaped with standardized technique, end up wider than the instrument size Second production quality is insufficient both for instruments and for gutta percha cones, leading to size variations. In small curved root canals Ledging, zipping, elbow formation, Perforation and loss of working length owing to compaction of dentin debris
• #42: The gutta-percha trial point should go fully to the constriction, and a slight tug-back should be felt when the point is removed (retention form). This shows that it fits tightly into the last 2 to 3 mm of the prepared canal.
• #47: In narrow calcified canals sizes 08 &10 should be first used to enable placement of the Hedstroem files and establish patency. They are also used intermittently between the Hedstroem files to maintain canal patency.
• #49: Minimize or eliminate the amount of necrotic debris that could be extruded through the apical foramen during instrumentation. Preparation of the coronal portion tends to shorten the effective length of the canal, and determining the working length after such enlargement will reduce the problem of its alteration during preparation. It allows better control over apical instruments
• #50: Prevents: post-treatment discomfort incomplete cleansing difficulty in achieving a biocompatible seal at the apical constriction It has risen in popularity, especially among those using nickel-titanium instruments with varying tapers
• #53: Counter clock wise rotation and apical pressure strikes a balance between tooth structure and instrument elastic memory. This balance locates the file very near the central axis even in curved canals. It avoids transportations. (Montgomery 1988)
• #57: This pressure action was followed by a negative pressure (suction) that removed the debris: “The irrigant fluid was injected through the outer tube while the reflux occurred through the inner tube.” More recently, they have improved the device and reported that the “smaller new machine produced equivalent or better cleanliness results in the root canal system using significantly less irrigant (NaOCl).”
• #58: Procedural accidents in endodontics are those unfortunate occurrences that happen during treatment, some due to inattention to detail, and others totally unpredictable.
• #61: PREVENTION By pre-curving or over curving the apical 3-4 mm of the file with the same curvature as the canal depicted in the radiograph By-passing the ledges if small enough
• #67: Files should be over-curved , especially in the apical 3 to 4 mm and always worked in the direction of curvature with short , in-out strokes ; do not rotate the file or change its orientation. Anti-curvature or reverse filing should be used in curved canals and in roots with deep proximal invaginations…