Cleaning and Shaping the Root Canal System PDF

Cleaning and Shaping the Root Canal System By Einas Osman Sharfi  The aim of root canal treatment is to reduce the level of microbial contamination as far as is practical, and to entomb any remaining microorganisms with an effective three-dimensional...

Cleaning and Shaping the Root Canal System By Einas Osman Sharfi  The aim of root canal treatment is to reduce the level of microbial contamination as far as is practical, and to entomb any remaining microorganisms with an effective three-dimensional seal. This achieve by shaping and cleaning.  Shape: Produce a gradual smooth taper in the root canal with its widest part coronally and the narrowest part at the apical constriction, is normally about 1 mm short of the apex.  Clean: Use antimicrobial agents to remove microorganisms and pulpal debris from the entire root canal system. CLEANING CLEANING  The purpose of cleaning is to remove all intracanal material, whether of pulpal origin, vital or necrotic, or microorganisms, from the root canal system. The removal of vital pulp tissue ‘‘PULP EXTIRPATION’’  In sufficiently wide and straight canals, broaches are recommended to withdrawn the pulp tissue all in one piece. Barbed broach.  It is a very delicate instrument that fractures easily.  It is not designed to work on canal walls nor, far less, to engage them, but rather only to hook and twist the pulp filament around itself so that as to extract the pulp from the root canal. Barbed broach The removal of necrotic pulp tissue and microorganisms  Pulp tissue that is necrotic or in an advanced state of degeneration cannot be removed with a broach.  The removal of this material is achieved by the use of irrigating solutions and the mechanical action of the endodontic instrumen ts.  instruments contact and plane all walls to loosen debris.  The chemical action of irrigants further dissolves organic remnants and destroys microorganisms. SHAPING Mechanical objectives 1. The shape should be a continuously tapering funnel from the apex to the access cavity. Mechanical objectives 2. Cross-sectional diameters should be narrower at every point apically. Mechanical objectives 3. The root canal preparation should flow with the shape of the original canal. Mechanical objectives 4. The apical foramen should remain in its original position. Mechanical objectives 5. The apical opening should be kept as small as practical.  in order to obtain a better seal and to prevent extrusion of the gutta-percha filling (creation of apical stop or apical seat)  Apical Stop. A barrier at the preparation end is an apical stop.  Apical Seat. Lack of a complete barrier but the presence of a constriction represents an apical seat.  Open Apex. The apical preparation resembles an open cylinder (neither barrier nor constriction).  Open apex is undesirable and will probably not confine materials to the canal space. Biological objectives 1. Procedures should be confined to the roots themselves. 2. Necrotic debris should not be forced beyond the foramina. Biological objectives 3. All tissues should be removed from the root canal space. 4. Sufficient space for intracanal medicaments and irrigation should be created. Instrument Movements While Shaping  WATCH-WINDING  REAMING  FILING (Circumferential filing & anticurvature filing)  ROTARY MOVEMENTS WATCH-WINDING  movement with rotations of a quarter turn (clockwise and anti clockwise)  using small (size #08 or #10) K-files to reach WL or to explore the canal prior to coronal flaring REAMING  Reamers were thought to cut by being inserted into the canal, twisted clockwise one-quarter to one-half turn to engage their blades into the dentin, and then withdrawn, that is, penetration, rotation, and retraction. FILING (push-pull motion)  In a filing motion, the instrument is placed into the canal at the desired length, pressure is exerted against the canal wall, and while this pressure is maintained, the instrument is withdrawn without turning.  Filing is very efficiently done with Hedstrom files while K- files are the most popular instruments BALANCED FORCE  The balanced force technique involves three principle steps. 1. The first step (after passive insertion of an instrument into the canal) is a clockwise rotation of about 90 degrees to engage dentin BALANCED FORCE  The balanced force technique involves three principle steps. 2. In the second step, the instrument is held in the canal with adequate axial force and rotated counterclockwise to break loose the engaged dentin chips from the canal wall BALANCED FORCE  The balanced force technique involves three principle steps. 3. in the third step, the file is removed with a clockwise rotation to be cleaned Techniques of canal preparation  Several systems to prepare canal with hand or engine driven instruments have been described.  There are two principally different approaches:  the ‘‘apex first’’  and the ‘‘coronal first’’ techniques.  The former approach (apex first) advocates that WL is reached and the apical area is prepared first with increasingly larger instrument sizes,  whereas the latter (coronal first) uses descending instrument sizes to prepare coronal canal areas first and apical ones last. Techniques of canal preparation preperation begin with preperation begin with Apical part coronal part  Crown down  Crown down pressuere  Standerdized less  Step back technique  Double flare tchnique  Modified crown down  Passive step back technique STANDARDIZED TECHNIQUE  The standardized technique uses the same WL for all instruments introduced into a root canal.  and therefore relies on the inherent shape of the instruments to impart the final shape to the canal. STANDARDIZED TECHNIQUE  Negotiation of fine canals is initiated with lubricated fine files in a so-called watchwinding movement.  These files are advanced to working length and worked either in the same hand movement or with “quarter-turn- and-pull” until a next larger instrument may be used. STANDARDIZED TECHNIQUE  Conceptually, the final shape should be predicted by the last instrument used  A single matching gutta percha point may then be used for root canal filling. STANDARDIZED TECHNIQUE  This method was satisfactory in straight canals, but was quite unsuitable for curved Canals.  As the instrument sizes increase, they become less flexible and led to iatrogenic errors in curved root canals.  Common problems encountered were ledging, zipping, elbow formation, perforation and loss of working length owing to compaction of dentine debris Iatrogenic errors C, Apical zip D, Ledge with A, Apical B, Ledge. with perforation. zip perforation STEP-BACK Technique  This Technique relies on stepwise reduction of WL for larger files, typically in 1- or 0.5-mm steps, resulting in flared shapes with 0.05 and 0.10 taper, respectively. STEP-BACK Technique  Incrementally reducing the working length when using larger and stiffer instruments also reduced the incidence of preparation errors, in particular in curved canals. STEP-BACK Technique  Can be divided into two phases.  Phase I is the apical preparation starting at the apical constriction.  Phase II is the preparation of the remainder of the canal, gradually stepping back while increasing the instrument size STEP-BACK Technique Phase I  The first file that is set to the working length and inserted into the canal to the point it binds is referred to as Initial Apical File (IAF)  The root canal is then widened with IAF and two to four sequentially larger files STEP-BACK Technique Phase I  The final file is used at full working length is referred to Master Apical File MAF  Note:  no instrument size must be skipped  The canal must be copiously irrigated STEP-BACK Technique Phase II  Then the step-back process (Phase II) begins with a file one size larger than the MAF.  Its WL is set 1 mm short of the full WL, and it is carried down the canal to the new shortened depth.  The same process is repeated with subsequent instruments again shortened by 1.0 mm from the MAF. STEP-BACK Technique Phase II  In between placing each larger instrument, the master apical file is inserted to the working length to clear any debris collecting in the apical part of the canal; this is referred to as RECAPITULATION.  The canal must be copiously irrigated The stepback technique example.  Length 20 mm  8,10,15,20,25 bind,30  35MAF  STEP BACK  40 19 mm  35 20 mm ( recapitulation)  45 18 mm  35 20mm recapitulation  50 17mm  35 20 mmrecapitulation  55 16mm  35 20mm recapitulation  The stepback technique helped to overcome the procedural errors of the standardised technique in slight to moderately curved canals, but in the more severely curved root canals problems still exist.  There are three ways in which some of the problems of the curved root canal may be overcome, by using: . A special filing technique. . A file with a modified non-cutting tip. . More flexible instruments. PASSIVE STEP-BACK  The passive step-back technique uses a combination of hand instruments (files) and rotary instruments (Gates- Glidden drills and Peeso reamers) to achieve adequate coronal flare before apical root canal preparation. PASSIVE STEP-BACK  Step One  With use of the diagnostic film, a No. 15 file is placed in the canal at the estimated working length of the root canal PASSIVE STEP-BACK  Step Two: Passive Step-Back Hand Instrumentation  No. 10 or 15 K-type file to estimated WL.  No. 20,2S, 30,35, and 40 K-type files are carried into the canal passively.  Copious irrigation. PASSIVE STEP-BACK  Step Three: Passive Use of Gates-Glidden Drills.  A No. 2 Gates-Glidden drill is inserted into the mildly flared canal to a point where it binds slightly.  It is then pulled back about 1 to 1.5 mm and the slow-speed handpiece is activated.  With an up-and-down motion and slight pressure, the desired canal wall(s) is planed and flared.  A similar technique is used to plane and flare the coronal region with No. 3 Gates-Glidden drill.  A No. 4 Gates-Glidden drill is used in large canals.  Step Four: Passive Use of Peeso Reamers. A No. 2  A No. 2 Peeso reamer is placed into the canal to a pointwhere it binds slightly.  It is then pulled back about 1 to 1.5 mm and the slow-speed handpiece is activated.  With an up-and-down motion the coronal portion of the canal is shaped and flared further.  With the use of a similar technique, the coronal 2 to 3 mm can be flared with a No. 3 Peeso reamer.  Step Five: Confirmation of Working Length.  Step Six: Apical Preparation.  After the canal is flared and the corrected working length is determined, a No. 20 file should penetrate to the working length without any resistance.  The canal is then prepared with sequential use of progressively larger instruments placed successively short of the working length.  Narrow or curved root canals should not be enlarged beyond the size of No. 25 or 30 files. Preparation techniques begin with coronal part Crown down (Step down) technique  advantages:  the technique permits straighter access to the apical region,  it eliminates coronal interferences,  it removes the bulk of tissue and microorganisms before apical shaping,  it allows deeper penetration of irrigants,  and the WL is less likely to change. Crown down (Step down) technique Steps 1. preparation of two coronal root canal thirds using Hedstrom files of size #15, #20, and #25 to 16 to 18 mm or where they bind. Crown down (Step down) technique 2. GG drills Nos. 2 and 3, and then potentially No. 4, are used sequentially shorter, thus flaring the coronal segment of the main root canal. Crown down (Step down) technique 3. Then, apical instrumentation is initiated; it consists of :  Negotiating the apical part with a small K-file,  shaping an apical ‘‘seat,’’  combining the two parts, by stepwise decreasing of WL of incrementally larger files.  Frequent recapitulation with a #25 K-file to WL is advised to prevent blockage. CROWN-DOWN PRESSURELESS technique Steps  Estimated WL is determined  size #35 K-file is introduced into the root canal with no apically directed pressure.  Then, a GG No. 2 is used, short of or to the length explored by the size #35 file.  followed by GG Nos. 3 and 4 with progressively shorter WLs. CROWN-DOWN PRESSURELESS technique  a size #60 hand file is used with no apical force, with reaming motion.  Then size #55 and smaller files are used (#50, #45 and so on)  A radiograph is taken when an instrument penetrates deeper than the estimated WL CROWN-DOWN PRESSURELESS technique  after that, the apically directed procedure continue until an instrument reached the definitive WL.  The final step is to enlarge the apical area to three sizes larger than the first file that bound at WL. DOUBLE FLARE technique  an exploratory action with a small file,  crown-down portion with K-files of descending sizes,  an apical enlargement to size #40 or similar.  stepping back in 1 mm increments with ascending files sizes and frequent recapitulations with the MAF. Copious irrigation is considered mandatory. DOUBLE FLARE technique Modified crown-down technique (Modified double flare)  Irrigate the pulp chamber, and identify the root canal with an explorer or fine file.  Estimate 2/3 length of canal from pre-operative X-ray. Check for patency with a size 15 file.  Widen to form gradual coronal flare with Gates-Glidden bur 2, then 3, then 4 at successively shorter lengths.  confirm working length Modified crown-down technique (Modified double flare)  confirm working length  Prepare apical region to three sizes larger than the size of the first file which binds at the working length. Irrigate well between each file.  The remainder of the canal is now flared by 'stepping back. ROTARY INSTRUMENTATION Introduction  The introduction of NiTi alloy for manufacturing hand files, and later engin driven instruments, has altered canal shaping procedures drastically over the past two decades ENGINE-DRIVEN ROTARY Systems  A variety of NiTi rotary file systems have been developed by different manufacturers  Many designs of NiTi instruments are available.  Most resemble a basic file  Some are available in different tapers and with noncutting tips  Another unique design (Lightspeed) resembles a Gates- Glidden drill,  Both types can be used with either conventional or special low-torque, controlled speed motor systems, including battery-operated handpieces First-generation motor without torque control Frequently used simple torque-controlled motor. Newergeneration motor with built-in apex locator and torque control. Techniques  After negotiating the canals and determining the corrected working length, NiTi rotary instruments are used to flare either with the step-back or the crown-down methods.  Straight-line access to the canal space is established.  A small hand file (No. 10 stainless steel) is used to explore the canal to the corrected length.  Hand instrumentation (reaming) is performed at the corrected length through two or three sizes with either stainless steel or NiTi files (glide path ).  This is followed by rotary instrumentation.  glide path :  It relates to securing an open pathway to the canal terminus that subsequent engine-driven instruments can follow.  The typical minimum glide path is a size #15 to #20 K-file and should be confirmed with a straight, not precurved file.  Very light pressure is used along with lubrication (irrigant) to place the NiTi rotary instrument into the canal until resistance is felt.  The instrument is then immediately withdrawn in a smooth motion from the canal space  After each withdrawal, the flutes are cleaned with wet gauze or an alcohol sponge, and the file is examined for distortions and/or deformations  This process is repeated by using a sequence of larger instruments to the desired length, with recapitulation and irrigation between each instrument size Advantages  Flexibility , the files have less tendency to transport curved canals.  Finger fatigue is less because the handpiece is doing much of the work.  Somewhat less time is required to prepare the canal.  Preliminary evidence indicates that debridement effectiveness is comparable to that with hand instrumentation Disadvantages  Expense is greater if one of the special motor systems is purchased;  in addition, the files are costly.  Files are prone to breakage, without warning, particularly if overused. Examples of rotary systems  Light Speed system  Profile system  ProTaper  K3 system  Hybrid tehnique. Protaper Light speed Evaluation Criteria  There are basically three criteria for evaluation of canal preparation. 1. Dibridement.  After preparation, the MAF tip is pressed firmly against each wall on the outstroke. All walls should feel smooth. 2. Taper.  The selected spreader passes easily to or within 1 mm of the working length with space alongside for the master gutta-percha cone. 3. Apical Preparation.  A seat or a stop or is identified by using a filesmaller than the MAF at the working length. THANK YOU