![Reverse Balanced-Force Preparation
• Instrument used for reverse balanced-force technique is NiTi greater taper hand file.
• Greater taper hand files can be used for reverse balanced-force technique, as the flutes
of these files are machined in a reverse direction unlike the other files.The handle of
these files is increased in size to make the reverse balanced-force manipulation easier.
•Technique involves:
• In reverse-balanced force, the file is used in 60° anticlockwise movement, followed by
120° clockwise movement with apical pressure using the GT files (largest [blue] to
smallest [white]) in a crown-down sequence progressively towards the apex.
•This procedure is repeated till the estimated WL using diagnostic radiograph is reached.
•WL is determined.
• 0.02 tapered ISO files are used to prepare the apical portion (balanced-force technique
is used).
• Radicular preparation is completed using the GT hand file of appropriate taper](https://image.slidesharecdn.com/cleaningandshaping-240719092702-0c1fecb3/85/Techniques-and-Principles-of-Cleaning-and-Shaping-27-320.jpg)
Techniques and Principles of Cleaning and Shaping
- 1. CLEANING AND SHAPING Dr. DHEERAJ GUPTA PG IINDYEAR
- 5. INTRODUCTION • Successful root canal treatment is an interplay of many procedures, of which shaping and cleaning play an important role. • Early studies on prognosis of root canal treatment indicated that failures were mainly attributed to incomplete obturation. • This was not true as obturation only reflects the adequacy of shaping and cleaning. • Canals that are poorly obturated are often incompletely shaped and cleaned. • Elimination (or significant reduction) of the inflamed or necrotic pulp tissue and microorganisms are the most critical factors. ROOT CANALTREATMENT STRAIGHT LINE ACCESS DEBRIDEMENT AND DISINFECTION OBTURATION
- 6. DEFINITION • Cleaning includes the removal of all organic debris, which could possibly serve as substrate for bacterial growth or as the source of periapical inflammation due to seepage of proteolytic breakdown products. • Shaping implies the development of a unique shape for every root canal, directly related not only to the length but also to the position and curvature of each individual root and root canal
- 7. Root canal preparation has been described in many ways: • Canal preparation • Biomechanical preparation – involves biological and mechanical objectives in preparing root canal • Chemo mechanical preparation – a combination of mechanical instrumentation and chemical disinfection by chemical means. • In 1974, Schilder introduced the term cleaning and shaping to the endodontic vocabulary. • Human root rarely contains a single simple root canal. Accessory canals, lateral canals, fins, isthmus and apical delta contribute to the root canal system. • Majority of these anatomical extensions are not accessible to instrumentation and are dependent on irrigating solution to flush through this system to dissolve organic debris and destroy the microorganisms at the same time. • The current terminology for root canal preparation is not cleaning and shaping, but shaping and cleaning. Once shaped and cleaned, the root canal system is obturated to prevent entry of microorganisms, from apical and coronal aspects, and to entomb any remaining microorganisms to prevent their proliferation
- 8. Goals of Root CanalTreatment • Major goals of root canal treatment are the following: • Promote healing of periradicular lesions • Prevention of periradicular disease Mechanical Objectives Biological Objectives 1. Continuously tapering funnel from the apex to the access cavity 2. Making the preparation in multiple planes, which introduces the concept of flow 3. Making the canal narrower apically and widest coronally 4. Avoiding the apical transportation of foramen 5. Keeping the apical opening as small as possible 1. Scrupulously remove all tissue debris, microbes and their by-products. 2. Limit the instrumentation to within the root canal.An exception to this rule is the use of the ‘patency files’. 3. Do not force necrotic material beyond the foramen. 4. Enlargement of the canals should create space which acts as a reservoir for irrigants and intracanal medicaments to eliminate the bacteria and their by-products.
- 9. Radicular Preparation • Instruments used in canal preparation are made of stainless steel or nickel–titanium (NiTi). • These instruments are manipulated in the canal manually (hand) or mechanically (rotary or reciprocal). • In the past, sonic and ultrasonic were used to prepare the canal.
- 10. Few terminologies: Initial Apical File – The smallest and first file that binds at correct working length Patency File –The Smallest file passively extended through the apical foramen to clear the portal of exit Recapitulation – Returning to a smaller file after every larger file to prevent packing of canal and ensure patency of canal Anti-curvature Filing – Prevent excessive removal of dentin from thinner part of curved canals i.e inner or furcal curve Pre-curving – Curving the instruments while negotiating curved canals Master Apical File –The largest file that binds correctly at working length after BMP
- 11. Bio – Mechanical PreparationTechnique Apico-coronal Preparation Standardized Method Step Back Modified Step Back Passive Step Back Corono-Apical Preparation Step Down Crown-down Pressure less Technique Double flareTechnique Modified double-flare technique Hybrid/Combined
- 12. Standardized Method • Introduced by Ingle as the first formal root canal preparation. •WL is determined and the initial apical file is selected. • Circumferential filing is done to increase the apical constriction two to three file sizes greater than the initial apical file to complete the preparation. • It is the technique of inserting the file into the root canal to the working length, engaging it into the dentine wall by applying lateral pressure and withdrawing it.This procedure is performed around all the walls of the canal.
- 13. Standardized Method Advantages Disadvantages • Easy to master. • Preparation has the same shape, size and taper as a standardized instrument. • Less time consuming. • Stainless steel files should not be used in curved canals, because as the size of the instrument increases, flexibility decreases, resulting in mishaps (ledging, zipping, perforation). • NiTi instruments reduce/ eliminate mishaps. • Loss of WL due to the accumulation of dentine debris.
- 14. Step-Back Preparation (Telescopic Preparation or Serial Root Canal Preparation) • Canal is shaped (with copious irrigation) from apex with a fine instrument, working backwards coronally progressively with larger instruments. • Mullaney divided it into two phases: • a. Phase I • b. Phase II • II-A • II-B
- 15. Step-Back Preparation (Telescopic Preparation or Serial Root Canal Preparation) • Phase I The canal is lubricated and explored using a patency file (#8/10 K-file). WL is determined (e.g. 20 mm). The first instrument that snuggly fits at apical constriction (initial apical file) is selected (e.g. ISO 15). The next size instrument (#20) is used to the same WL, in the same watch-winding motion till the instrument becomes loose, followed by irrigation. File #25 is used in the same manner to theWL to complete the apical preparation and the canal is irrigated. • Phase II-A Next size file (#30) is used 1 mm short (i.e. 19 mm) of the actual WL with watch-winding motion till the instrument becomes loose and the canal is irrigated. The previous instrument (#25) is used to the actual WL (20 mm) to ensure the patency of the canal followed by irrigation. Sequential re-entry and reuse of each previous instrument is called recapitulation. The next instrument (#35) is used 2 mm short (i.e. 18 mm) of the WL in a lubricated canal in watchwinding motion till the instrument becomes loose. Till the straight midcanal is reached, where the instrument no longer fits snuggly.
- 16. Step-Back Preparation (Telescopic Preparation or Serial Root Canal Preparation) • Phase II-B (Refining Phase) • The last apical instrument (#25) is used to smoothen all the walls with push–pull strokes followed by copious irrigation.
- 17. Modified Step-Back Preparation • After the enlargement of the apical stop, the step-back procedure begins 2 mm coronal to the apical foramen. • This provides a short parallel retention form to the master GP point which snuggly fits in apical third. Advantages Disadvantages • Decreases apical transportation • Increases the percentage of canal walls being planed • Passing a pre-curved instrument in a coronally tight canal straightens the instrument, leading to ledge formation. • As it holds a minimal volume of irrigant, accumulation of dentinal mud leads to blockage of foramen. •WL is more likely to change as the coronal constriction is removed last.
- 18. Passive Step-BackTechnique • It is a combination of hand and rotary instrumentation. • After estimating theWL with #15 K-file, insert #20, 25, 30, 35 and 40 files passively (may not reach the WL). • GG drills are used for additional coronal enlargement. • #20 K-file is inserted into canal up toWL and foramen is enlarged using watch-winding motion. • Canal is then prepared with progressively larger instruments placed short of theWL. • Advantages • Gradual passive enlargement of canal in an apical to coronal direction • Decreases incidence of procedural errors like transportation, ledge and zip formation • Removal of debris and minor canal obstructions
- 19. Passive Step-Down Preparation (Crown-Down Preparation) • This step focuses on opening and flaring the coronal third followed by middle third preparation and finally the apical third. Procedure •After preparing the access cavity under RD, coronal third is flared using GG drills #1, #2. •Apical instrumentation – two steps: •WL is determined. •Apical stop is prepared to size #25. • Remaining canal is shaped using step-down technique in which large files are used in the middle third followed by sequentially decreasing the size of the file as we approach the apical third.
- 20. Passive Step-Down Preparation (Crown-Down Preparation) Advantages • Provides straighter access to the apical region. • Most of the pulp tissue, debris and microbes are eliminated before apical instrumentation. • Eliminates dentinal interferences in the coronal third early in the preparation. • Allows deeper penetration of irrigating solutions. • Better control over apical instrumentation. • Less chances of change in theWL due to change in the canal curvature. • Less chances of instrument fracture. • Due to better tactile sensation, lodging and transportation is also reduced.
- 21. Crown-Down Pressure less Preparation • Coronal flaring is done with the GG drills, followed by larger files in the coronal third and then progressively smaller files are used in an apical direction without any pressure till the desired length is reached. Procedure •After application of the RD, canal patency is determined using #10 K-file. • Insert #35 file until it just binds and measure the length.This is known as radicular access length (RAL). • Coronal portion is flared using GG drill in a brush-out motion up to RAL. • #30 file is inserted and rotated clockwise slightly beyond RAL until resistance is felt and the canal is prepared till the instrument is loose. •The next smaller files are inserted in sequential order to a point 3 mm short of the radiographic apex (provisionalWL). • Obtain a radiograph with the file at the provisionalWL and estimate the trueWL.The file that fits snugly at the trueWL is the initial apical file. • Continue stepping down with smaller files to the trueWL. •Apical stop is enlarged three times the initial apical file. • Finally the canal walls are finished by circumferential filing. Advantages • By eliminating the coronal constrictions, it reduces the effect of canal curvature and hence better tactile sensation. •Allows effective irrigation and hence the danger of pushing the debris beyond the apex is reduced (thus eliminating postoperative discomfort). •WL is less likely to change during apical instrumentation. • Holds larger volume of irrigants and hence helps in dissolution of pulp tissue in the apical and lateral canals. • Improves identification of foramen as it accepts larger files into the apical one-third, which is easier to visualize in the radiograph. •This technique reduces the risk of instrument fracture. • Precurved files remain curved, can be easily inserted and freely passed down the canal.
- 22. HybridTechnique • Combination of step-down and step-back preparation is known as hybrid technique. • Patency of canal is checked with #10 K-files. •The canal preparation is done using hand/GG drills from coronal till point of curvature without excess apical pressure. •WL is determined. • Unprepared apical portion of the canal is prepared using step-back technique. • Recapitulation is done with patency file. • Copious irrigation is done at every step. • Blend the step-back with step-down preparation.
- 23. Double-FlaredTechnique • In this technique, canal is prepared with crown-down pressure less technique with copious amount of frequent irrigation. • OnceWL is reached, foramen is enlarged to master apical size. • Canal is once again flared from apex using step-back method till the middle third which gives it a double flare. • Advantage Disadvantage Better cleaning with more volume of irritant exchange Excessive removal of dentine compromising the strength of the root
- 24. Balanced-Force Preparation • It is one of the methods used to prepare a curved canal without precurving the instrument. •This technique involves oscillation (reciprocation) of the instrument in clockwise and CCW directions. • Coronal flaring is done using crown-down technique followed by irrigation. •WL is determined. • Balanced-force movement of file is followed at the apical third of the canal.
- 25. Balanced-Force Preparation These include three phases: a. Phase I: file insertion – file is placed into the canal with light pressure until it binds against the wall.The file is then rotated clockwise through 60–90° so that the flutes engage the dentine and advance apically (clockwise rotation always advances the file apically as it engages the dentine). b. Phase II: file cutting – the file is now rotated 120–180° in CCW direction with apical pressure which prevents the movement of the file in the coronal direction.This breaks off the dentine engaged in the flutes with a clicking sound and enlarges the canal. c. c. Phase III: flute loading – a final clockwise rotation without apical advancement allows flutes to be loaded with debris and removed from the canal.
- 26. Balanced-Force Preparation •Thus, a balanced force is used to remove the dentine. •The preparation is done in crown-down technique by sequentially using smaller files till WL is reached.The apical width is then enlarged to master apical size. Advantages • It positions the instrument near the canal axis even in severely curved canals and avoids recognizable transportation of original canal path. •Works effectively without precurving (but might need a tip bend in sharply deviated apical foramen). • File cutting occurs only at the apical extent of the file.
- 27. Reverse Balanced-Force Preparation • Instrument used for reverse balanced-force technique is NiTi greater taper hand file. • Greater taper hand files can be used for reverse balanced-force technique, as the flutes of these files are machined in a reverse direction unlike the other files.The handle of these files is increased in size to make the reverse balanced-force manipulation easier. •Technique involves: • In reverse-balanced force, the file is used in 60° anticlockwise movement, followed by 120° clockwise movement with apical pressure using the GT files (largest [blue] to smallest [white]) in a crown-down sequence progressively towards the apex. •This procedure is repeated till the estimated WL using diagnostic radiograph is reached. •WL is determined. • 0.02 tapered ISO files are used to prepare the apical portion (balanced-force technique is used). • Radicular preparation is completed using the GT hand file of appropriate taper