Cleaning and shaping 1


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Introduction to Endodontics
Forth Year

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Cleaning and shaping 1

  2. 2. Objectives of cleaning and shaping 1. To remove and/or eliminate from the root canal, all of its contents that may lead to the growth of micro-organisms or breakdown of toxic products into the peri-radicular space. 2. To remove the irregularities of canal walls as well as obstructions such as calcifications, filling materials etc. 3. To prepare the root canal not only for its disinfection but also to develop a shape a shape that permits the simplest and most effective 3D filling.
  3. 3. Principle of cleaning : Removal of the necrotic tissue and irritants from the root canal system. Instruments must contact and plane the canal walls to debride the canals
  4. 4. How to assess cleaning??  Presence of clean dentinal shavings  The colour of the irrigant  Canal enlargement three sizes larger than the size of the first instrument that binds with the canal Obtaining Glassy smooth walls : properly prepared canals should feel smooth in all dimensions when the tip of a small file is pushed against the canal walls
  5. 5. Principle of Shaping: Provide a shape that facilitates cleaning and a 3 Dimensional filling [obturation] Main objective is to provide a continuously tapering preparation • Prepration must flow and progressively narrow in an apical direction • Starting at orifice and moving apically, every cross sectional diameter of preparation should decrease
  6. 6.  Original anatomy maintained  Position of the foramen maintained  Foramen as small as practical
  7. 7. • Files shape and irrigants clean the root canal.
  8. 8. Working Length Determination Working Length : Defined as the distance from a predetermined coronal reference point to the point the cleaning and shaping, and obturation should terminate
  9. 9. a) Radiographic apex • The termination of the root, as shown on the radiograph. • Not a true indicator especially  buccal/lingually curved roots. b) Minor constriction/minor foramina: • Narrowest portion of the root at the apex • Corresponds to the junction of dentin cementum (CDJ) • Histological
  10. 10. c) Major constriction: • It is the anatomic apex of the root • Bordered by cementum • Corresponds with the radiographic apex
  11. 11.  Till many years the endodontic treatment was restricted to 0.5-2 mm short of the radiographic apex.  It should be 1mm from the radiographic apex  Working short → apical blockage ← dentin chips  Apical blockage → combination of pulp, bacteria and their endotoxins → dentin mud.
  12. 12. Methods of Working Length Determination  Predetermined normal tooth length  Radiographs  Tactile sense  Paper points  Patient response  Electronic Apex Locators
  13. 13. Dummer : Types of Apical Constrictions
  14. 14. Radiographic apex location Though not very accurate, provide with a baseline measurements  almost reliable. Procedure: After access preparation small file is used to explore the canal and check the patency. The largest file to bind at the apex is then inserted. -Small file may get dislodged -The tip of the file is not very clear on a radiograph
  15. 15. • Instrument is placed in the canal, inserted to a point until pain is felt [not always reliable]. • Rubber stopper is then adjusted to a plane of reference on the tooth. • Radiograph is then taken and the radiographic length is measured. • At least 1 mm is subtracted as ‘Safety allowance’ for possible image distortion or magnification
  16. 16. A. Do not use weakened enamel walls or diagonal lines of fracture as a reference site for length-of-tooth measurement. B. Weakened cusps or incisal edges are reduced to a well-supported tooth structure. Diagonal surfaces should be flattened to give an accurate site of reference.
  17. 17. When 2 canals are superimposed  a mesially directed radiograph is taken SLOB RULE : Same side lingual opposite side buccal SLOB
  18. 18. Clark’s Rule  MLM  when an X-ray is directed mesially the lingual canal appears more mesial.  MBD  when as X-ray is directed mesially the buccal canal is projected towards the distal on the film.  When 2 canals are present, it is always advisable to use 2 instruments & use MLM rule/MBD
  19. 19. Electronic Apex locators: Electronic devices used for the determination of the working length It consists of a lip clip, a file clip, a connection cord and the device itself.
  20. 20. The lip clip is placed into the metal ring / loop attached to the carrier tray of the Modu PRO kit. Attach the endodontic file to the file clip and introduce into the canal slowly. The display on the Apex locator will indicate the distance of the file tip to the apex.
  21. 21. Apical canal Preparation Termination of the preparation Apical enlargement or Apical size • Minimum of three sizes larger than the first file that binds at the apex • Larger the size more efficient will be the irrigation cleaning
  22. 22. Elimination of etiology • Files alone cannot eliminate the etiology + • Irrigants, intracanal medicaments Apical Patency
  23. 23. Various motions of the hand instruments: Watch winding / Twiddling: •Reciprocating clockwise /counterclockwise rotation of the instrument in an arc of 30 o – 90 o. •Used to negotiate canals and to work the files to the working length •Least aggressive
  24. 24. Watch winding and pull motion
  25. 25. Reaming Defined as the clockwise cutting rotation of the file. Instrument is placed into the canal until binding is encountered and then rotated 180-360 degrees to plane walls and enlarge the canal
  26. 26. Filing •Defined as placing the file into the canal and pressing it laterally while whitdrawing it along the path of insertion to scrape the wall •Indicates push-pull motion •There is very little rotation •Scraping or Rasping action •May lead to canal ledging, perforations and other procedural errors
  27. 27. Turn- pull Technique: •Modification of the filing technique •Placing the file to the point of binding, rotating the instrument 90 degrees and pulling the instrument along the canal wall
  28. 28. Circumferential Filing : • Used for canals that are larger and are not round. • The file is placed in the canal and withdrawn in a directional manner sequentially against the mesial, distal, buccal and lingual walls
  29. 29. Techniques for Preparation Canal preparation techniques can be broadly divided into those that adopt an ‘apical to coronal’ preparation procedure and those that adopt a ‘coronal to apical’ approach
  30. 30.  Step back technique  Step down technique  Passive Step Back Technique  Anticurvature Filing  Balanced Force Technique  Nickel Titanium Rotary preparation
  31. 31. STEP BACK PREPARATION  Also called Telescopic or Serial root canal preparation. Phase I – Apical Preparation • Canal is generally explored with a fine instrument • Working length is then determined • 1st instrument to be inserted should be a fine (No. 8,10 or 15) K-file, pre-curved and coated with a lubricant • Motion is generally ‘watch winding’- 2 or 3 quarter turns clockwise- anti clockwise and then retraction.
  32. 32. • Upon removal, the instrument is wiped clean, recurved, relubricated and • reinserted. Procedure is repeated until the instrument is loose in position. • Then the next size K-file is used • By the time a size 25- K file has been used to full length, Phase I is complete.
  33. 33.  In curved canals the apical preparation with instruments of sizes > 25 would pose a danger of zipping.  The instruments, as they become larger also become stiffer  The instruments also tend to straighten with in the canal.  During the whole procedure recapitulation with a smaller file & copious irrigation is essential so as to ensure patency of the canal
  34. 34. A B C D Hazards of overenlarging the apical curve. A. Small flexible instruments (No. 10 to No. 25) readily negotiate the curve. B. Larger instruments (No. 30 and above) markedly increase in stiffness and cutting efficiency, causing ledge formation. C. Persistent enlargement with larger instruments results in perforation. D. A “zip” is formed when the working length is fully maintained and larger instruments are used.
  35. 35. Phase II  In a fine canal, step back process begins with a N0: 30 K-file with a working length set 1mm shorter.  The instrument is pre-curved, lubricated, carried down the canal to the new WL, watch wound and retracted.  Process is repeated till #30 file is loose within the canal.  Recapitulation to the full length with a # 25 K file follows to assure patency to the constriction.  Thus, preparation steps back up the canal one millimeter and one large instrument at a time.
  36. 36.  When the mid-canal is reached, where the instruments no longer fit, perimeter/ circumferential filing may begin.  H- Files can be used at this stage as they are more aggressive.  A Gates-Glidden drill can be used at this stage. Starting with a smaller drill (no. 1& 2) and then gradually increasing the size to 4,5 &6.
  37. 37.  The drill should be used with great care.  A proper continuing taper is developed to finish Phase II A  Refining Phase II B is a return to size No. 25 instrument, smoothening all around the walls to perfect the taper from the apical constriction to the canal orifice.
  38. 38. STEP BACK PREPARATION PHASE I [Apical Preparation] PHASE II [Coronal Preparation] PHASE II A REFINING PHASE II B
  39. 39. Advantage:  Considered to minimize procedural errors, such as transportation, ledging and apical perforation Disadvantage:  Results in significant apical extrusion of debris, Apical blockage, canal deviation, alteration of working length