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Cleaning and shaping the root canal system
 

Cleaning and shaping the root canal system

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    Cleaning and shaping the root canal system Cleaning and shaping the root canal system Presentation Transcript

    • CLEANING AND SHAPING OF THE ROOT CANAL
    • Introduction
      • Endodontic therapy essentially is directed towards one specific set of aims to cure or prevent periradicular periodontitis.
      • Primary aim of all endodontic procedure & most notably of cleaning & shaping is to remove canal contents, specially infective microorganism.
      • An overview of steps in root canal treatment.
      ACCESS CAVITY PREPERATION CLEANING & SHAPING
      • WORKING LENGTH DETERMINATION.
      • INSTRUMENTATION
      • IRRIGATION
      OBTURATION
    • Objectives of Canal Preparation
      • Start with the end in mind
      • The root canal system must be:
      • Cleaned of its organic remnants
      • Shaped to receive a three dimensional filling of the entire root canal space
      The canal is Cleaned primarily by irrigation Shaped primarily by instrumentation Hence cleansing and shaping
    • 1.Remove the infected soft and hard tissue. Basic Objectives in cleaning and shaping of the root canal: (cohen)
      • 2. Give disinfecting irrigants access to the apical canal space.
      • 3. Create the space for the delivery of medicaments and subsequent obturation.
    • 4. Retain the integrity of radicular structures. X X X
    • OBJECTIVES
      • Biological objectives:
      • To completely debride the pulp space of
        • Pulp tissue
        • Bacteria / Microorganisms
        • Endotoxins
      • Mechanical objectives:
        • Continuously tapering preparation
        • Maintain original anatomy
        • Maintaining the position of the apical foramen
        • Foramen as small as practically possible
        • Continuously tapering preparation
    • WORKING LENGTH DETERMINATION
    • Definition and significance
      • “ The distance from a coronal reference point to point at which canal preparation and obturation should terminate”.
    • significance
      • Determines how far into the canal the instruments are placed and worked.
      • Determines how far into the canal ,debris, metabolites end products and other unwanted items are removed .
      • Limits the depth of canal filling.
      • It effects the degree of pain and discomfort the patient will feel.
      • If calculated correctly, helps in determining the success of treatment.
    • Anatomical considerations and terminology
      • Apical foramen
    • Anatomic apex and Radiographic apex Anatomic apex : Is the tip or the end of the root determined morphologically, Radiographic apex : Is the tip or end of the root determined radiographically
    • Apical constriction( minor apical diameter)
      • The apical constriction is the apical portion of the root canal having the narrowest diameter.
      • This position varies usually 0.5 to 1.0 mm short of the center of the apical foramen.
        • Less in Young and anterior teeth (0.5)(0.8).
    • prerequisite
      • Good, undistorted, preoperative radiographs showing the total length and all roots of the involved tooth.
      • Straight-line access.
      • Small stainless steel K-file facilitates the process and the exploration of the canal.
      • A definite, repeatable plane of reference, it should be noted on the patient’s record.
      • Knowledge of the average length of all of the teeth.
    • Different techniques
      • Radiographic methods
      • Digital tactile method
      • Paper point evaluation
      • By apical periodontal sensitivity
      • Electronic apex locators
    • Radiographic methods
      • Pre-operative radiograph
      • Radiograph of the tooth with endodontic instrument placed to
      • its tentative working length.
      • Parallel technique
      • Bisecting technique
    • GROSSMAN’S METHOD Actual length of tooth = Actual length of instrument X radiographic length of tooth Radiographic length of instrument Actual length of tooth Actual length of instrument Radiographic length of instrument Radiographic length of tooth =
    • INGLE’S METHOD
      • 1.Measure the tooth on the preoperative radiogr aph.
    • 2. Subtract at least 1.0 mm “safety allowance” for possible image distortion or magnification. 3. Set the endodontic ruler at this tentative working length and adjust the stop on the instrument at that Level. 4. Place the instrument in the canal until the stop is at the plane of reference unless pain is felt.
    • INGLE’S METHOD
      • 5. Expose, develop, and clear the radiograph.
      • 6. measure the difference and correct the working length by adding or subtracting the difference.
      • 7. From this adjusted length of tooth, subtract a 1.0 mm “safety factor”
    • INGLE’S METHOD
      • 8. Place the instrument with adjusting the stopper
      • 9.Take a confirmatory radiograph
      • 10.Record this final working length and the coronal point of reference on the patient’s record.
    • INGLE’S METHOD
    • IN RESORPTIVE CASES (As modified by Franklin S Weine)
    • Digital tactile method
      • Accuracy ?????
        • Seidberg – 64% accuracy
        • In vivo – 25% accuracy
        • Preflared canals – 75% accuracy
      • Clinicians should be aware of this and this should be in conjunction with other methods.
      • Disadvantages :
      • Ineffective in root canal with immature apex.
      • Inaccurate if canal is constricted throughout its length or it curvature is present.
    • Paper point evaluation Indications : Root canal with immature apex Cases in which apical constriction has been lost. Paper point evaluation, by addition of mm markings 18, 19, 20, 22, 24mm from tip and can be used to estimate working length.
    • By apical periodontal sensitivity
      • Always working length determinants should be painless.
      • In inflamed tissue, hydrostatic pressure developed may cause moderate to severe instantaneous pain.
      • When pain is afflicted in this manner, little useful information is gained by clinician, and considerable damage is done to patients trust.
      • Canal contents totally necrotic – mild awareness or no reaction
      • APEX LOCATORS
      • Advantages
        • Accurate
        • Easy and fast
        • Reduction of exposure to radiation
    • Electronic apex locators Connections of the electrodes To file & cheek File placed to length indicated at “zero” by apex locator Apex indication in different apex locators
    • DETERMINING LENGTH OF TOOTH
    •  
    • First generation
      • RESISTANCE TYPE
      • Measured the difference in resistance between the periodontal ligament and the oral mucosa (6k Ω )
      • Uses direct current
      • Requires dry field for accurate measurements
    • Second generation
      • IMPEDANCE TYPE
      • Based on impedance measurements at same or different frequencies
      • Uses alternating current
      • Requires dry field for accurate measurements
    • Third generation
      • FREQUENCY DEPENDENT Multiple frequency type
      • Uses multiple frequencies to determine the position of the file in the canal
      • Uses alternating current
      • Difference method/ratio method
      • Can be used in wet/dry fields
      • Most accurate among the three
      • Apex locator with built in pulp tester
      • Handpiece with built in apex locator
    •  
    •  
    • Eliminating or minimizing the influence of affecting factors
      • Monitor the working length periodically
      • Stop attachment be perpendicular and not oblique to the shaft of the instrument.
    • Techniques of pulp space preparation Hybrid technique Step back step down combination procedure Apical coronal preparation technique Step back preparation & modifications. Coronal to apical preparation technique Step down tech
    • Standardized preparation
      • Premise: canal circular in CS in apical third
      • Standardized files used sequentially to the full working length
      • Produces prep with same size and shape as last std instr
      • Canal enlarged until clean white dentin shavings are seen on the apical few mm of the instrument
      • Filing continued for a further 2 or 3 sizes
      • Canal is made to fit filling material
      • Obturation – silver points accepted
      • Disadvantages:
      • In small curved root canals
      • Ledging, zipping, elbow formation,
      • perforation and loss of working length owing to compaction of dentin debris
      Hourglass preparation
    • STEP BACK PREPARATION (Telescopic, Serial root canal prep)
      • 2 phases –
      • Apical preparation. ( phase 1 )
      • Preparation of remaining canal by stepping back. ( phase 2 )
    • WL established ,1 st active instr 8,10, 15 lubricated Motion- watch winding Apical preparation upto the file #25(MAF)to full WL With recapitulation using prior size
    • Stepping back in increments with recapitulation using # 25 file to ensure patency to the constriction with irrigation (step back up the canal 1mm and 1larger instr at a time)
    • For coronal and mid root preparation Gates Glidden drills Nos 2,3,4 along with lubrication
    • Return to # 25 last file (MAF) Short of working length to smooth the step back with vertical push- pull strokes (circumferential filing) H files used.
    •  
    • Advantages
      • Better tactile awareness
      • Keeps apical prep small in its original position- gradual taper
      • Greater taper coronally compared to standard prep more dentin removal and cleaner walls.
      • Avoids zipping.
    • Disadvantages
      • Chances of pushing debris into peri-radicular tissues
      • Working Length likely to change as canal curvatures are eliminated
    • MODIFICATIONS OF STEP BACK
      • Weine – precurving of files to minimize canal alteration
    • CORONO APICAL PREPARATION
      • ADVANTAGES
      • Better tactile awareness in negotiating the delicate apical third microanatomy.
      • It reduces pressure.
      • Holds greater volume of irrigant - enhances cleaning.
      • Removal of dentin mud decreases post treatment problems.
      • DISADVANTAGES:
      • Increased removal of tooth structure
    • STEP DOWN TECHNIQUE
    • Step down technique Principle- coronal aspect of the root canal is prepared and cleaned before the apical part coronal preparation using gates glidden, smaller hand instruments to the apex
    • K-File Series Step-Down Technique. Starting with a No. 50 instrument (for example) and working down the canal to, say, a size No. 15, the instruments are used in a watch-winding motion until the apical constriction (or working length) is reached. When resistance is met to further penetration, the next smallest size is used. Irrigation should follow the use of each instrument and recapitulation after every other instrument. To properly enlarge the apical third, and to round out ovoid shape and lateral canal orifices, a reverse order of instruments may be used starting with a No. 20 (for example) and enlarging this region to a No. 40 or 50(for eg).
    • Balanced force 1985 (ROANE ) TECHNIQUE
      • Preparing curved canals with Flex- R files (mod of K files) triangular Cross Section inst because decreased mass & deeper cutting flutes improves flexibility
      • Non cutting tip (70 degree taper ) made up of initial tip (wide cone)
      • Establish radicular access by step down or crown down tech before preparing apical 3rd of canal.
      • File placed to WL ,rotated clockwise 90 degree with light pressure to engage dentin then
      • Rotate file counter clockwise 120  C maintaining apical pressure to cut & enlarge the canal
    •  
    •  
    • Advantages
      • Counter clock wise rotation and apical pressure strikes a balance between tooth structure and instr elastic memory.
      • This balance locates the file very near the central axis even in curved canals
      • It avoids transportations.
      • Disadvantages
      • Strip perforations
    • THREE DIMENSIONAL CLEANING AND SHAPING CONSERVATION OF MAXIMUM TOOTH STRUCTURE
      • CORONO APICAL PREPARATION
      • ( CROWN DOWN )
      • ADVANTAGES
      • Better tactile awareness in negotiating the delicate apical third microanatomy.
      • It reduces pressure.
      • Holds greater volume of irrigant - enhances cleaning.
      • Removal of dentin mud decreases post treatment problem.
      • APICO CORONAL PREPERATION
      • ( STEP BACK )
      • ADVANTAGE
      • Better tactile awareness
      • Keeps apical prep small in its original position- gradual taper
      • Greater taper coronally compared to standard prep more dentin removal and cleaner walls.
      • Avoids zipping.
    • Step back Crown down
      • DISADVANTAGE
      • Chances of pushing debris into peri-radicular tissues
      • Working Length likely to change as canal curvatures are eliminated
      DISADVANTAGES : Increased removal of tooth structure
    • Procedural Accidents
    • Procedural accidents in endodontics are those unfortunate occurrences that happen during treatment, some due to inattention to detail, and others totally unpredictable.
      • Loss of working length
      • Ledging, zipping, elbow
      • Separated instruments
      • perforation
      • Over instrumentation
      • Canal blockage
      • It is a very common and frustrating error usually noted on a master cone radiograph.
      • It is actually secondary to the other procedural errors.
      LOSS OF WORKING LENGTH
    • LEDGING
      • Any deviation from the original canal curvature results in the formation of a ledge.
      • CAUSES
      • Inadequate access cavity preparation
      • False estimation of pulp space direction
      • Failure to pre-curve SS instruments
      • Failure to use instruments in a sequential manner
      • Attempt to retrieve separated instruments
      • Attempt to prepare calcified canals
    • ZIPPING OR ELLIPTICATION Transportation or transposition of the apical portion of the canal
    • PERFORATION
      • An artificial opening in a tooth or its root , created by boring, piercing , cutting or pathologic resorption, which results in a communication between the pulp space and the periodontal tissues
      • Incidence 3-10%
      • Causes
      • - Caries
      • - Resorptive defects
      • - Iatrogenic events
      Perforation
    •  
    • Classification based on the location Mid – root Apical Cervical
    • SEPARATED INSTRUMENTS The incidence of separation is 2-6%
    • Thank U