Principles of intra coronal and radicular preparation


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Introduction to Endodontics
Forth Year

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Principles of intra coronal and radicular preparation

  2. 2. Endodontic therapy involves treating vital or necrotic dental pulps so that patients can retain their natural teeth in function and aesthetics
  3. 3. Removal of infected / necrotic tissue Disinfection of the root canal space Widen the root canal space Fill the root canal space with an inert material
  4. 4. Endodontic treatment can be divided into 3 main phases 1. Bio-mechanical preparation ( cleaning and shaping ) 2. Disinfection 3. Obturation
  5. 5. 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 that permits the simplest and most effective 3D fitting.
  6. 6. Why not prepare the canals to a standard size and shape?????? 1. A histological examination of root canal  root canal system  tortuous turns, apical foraminae and at times accessory canals. 2. This root canal system whose shape has been altered by age, operative procedures, decay and trauma; is unique for each tooth and is different from tooth to tooth. 3. A standard root canal is not existent.
  7. 7. CLINICAL OBJECTIVES (COHEN BURNS) 1. Pretreatment evaluation • Restorability of the tooth/teeth • Coexistant periodontal defect • Pulpal involvement??  Pulpectomy vs vital pulp therapy
  8. 8. 2. Access for success • Access cavity is designed to deroof the pulp chamber providing a straight line axis to orifices. • Shape determined by position of orifices. • Provide space for unhampered instrumentation and final obturation.
  9. 9. 3. Shaping facilitates cleaning • Shaping facilitates cleaning by removing restrictive dentin, allowing an effective volume of irrigant to work deeper and more quickly into all aspects of root canal system . • It was demonstrated that a 5.25% solution of NaOCl is able to penetrate, dissolve and flush out organic tissue and related debris from inaccessible aspects of the root canal system where files cannot reach. • Files shape and irrigants clean the root canal.
  10. 10. 4. Shaping facilitates obturation • Shaping facilitates 3-D obturation by removing restrictive dentin
  11. 11. BIOLOGIC OBJECTIVE  Biologic objective of cleaning and shaping procedures is  complete removal of pulp tissue
  12. 12. MECHANICAL OBJECTIVES  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
  13. 13.  Original anatomy maintained  Position of the foramen maintained  Foramen as small as practical
  14. 14. Principles of Endodontic cavity preparation Endodontic cavity preparation may be separated into two anatomic divisions: (a) Coronal preparation (a) Radicular preparation.
  15. 15. Black's principles of cavity preparation can be modified to include the Root canal 'cavity' preparation Black's principles are therefore divided into the following Endodontic Coronal Cavity Preparation I. Outline Form II. Convenience Form III. Removal of the remaining carious dentin (and defective restorations) IV. Toilet of the cavity
  16. 16. Endodontic Radicular Cavity Preparation I and II. Outline Form and Convenience Form (continued) IV. Toilet of the cavity (continued) V. Retention Form VI. Resistance Form
  17. 17. 1. Outline form  The entire preparation, crown to apex, falls under outline form.  Governed solely by the anatomy of the root canal.  To achieve optimal preparation, three factors of anatomy must be considered: (1) the size of the pulp chamber, (2) the shape of the pulp chamber, and (3) the number of individual root canals, their curvature, and their position internal
  18. 18. Size of Pulp Chamber: •Outline form is affected by the size of the pulp chamber •In young permanent teeth size of pulp camber is large •In geriatric patients the pulp size decreases. Shape of Pulp Chamber. • The finished outline form should accurately reflect the shape of the pulp chamber.
  19. 19. Number, Position, and Curvature of Root Canals: • To prepare each canal efficiently without interference, the cavity walls often have to be extended to allow an unstrained instrument approach to the apical foramen.
  20. 20. 2. Convenience form  Removing excess of coronal dentin, so as to allow passage of larger instruments, for better instrumentation, irrigation and obturation. Four important benefits are gained through convenience form modifications: (1) unobstructed access to the canal orifice, (2) direct access to the apical foramen, (3) cavity expansion to accommodate filling techniques, and (4) complete authority over the enlarging instrument.
  21. 21. Shamrock preparation •Modified outline form to accommodate the instrument unrestrained in the severely curved mesial canal •Extending only that portion of the wall needed to free the instrument, a cloverleaf appearance may evolve as the outline form
  22. 22. 3. Removal of the Remaining Carious Dentin and Defective Restorations : Caries and defective restorations remaining in an endodontic cavity preparation must be removed for three reasons: 1. To eliminate mechanically as many bacteria as possible from the interior of the tooth, 2. To eliminate the discolored tooth structure, that may ultimately lead to staining of the crown, and 3. To eliminate the possibility of any bacteria-laden saliva leaking into the prepared cavity.
  23. 23. The Access cavity should preferably have 4 walls. It serves several purposes 1.Correct positioning of the rubber dam so that the clamp is stable 2.Keeping the pulp chamber constantly flooded with as much irrigation solution as possible 3.Defining easily recognizable and stable reference points for the rubber stops on the endodontic files 4.Introducing a temporary cement so as to seal the pulp chamber adequately When one or more walls are lacking→ reconstructed
  24. 24. Toilet of the Cavity •All of the caries, debris, and necrotic material must be removed from the chamber before the radicular preparation is begun. •If the calcified or metallic debris is left in the chamber and carried into the canal, it may act as an obstruction during canal enlargement. • Soft debris carried from the chamber might increase the bacterial population in the canal
  25. 25. Cleaning and Débridement of the Root Canal 1. The first objective is achieved by skillful instrumentation coupled with liberal irrigation. 2. This double-pronged attack will eliminate most of the bacterial contaminants of the canal as well as the necrotic debris and dentin
  26. 26. Whenever drying the chamber or canals air must never be aimed down the canals → Emphysema of the oral tissues
  27. 27. 4. Retention form  Near parallel walls in the apical 2-3 mm ensure a snugly fitting G.P [ Apical TUG BACK ] .  Most crucial for preventing apical leakage.
  28. 28. 5. Resistance form  Resistance to overfilling is provided by maintaining the integrity of the natural constriction of the apical preparation  Prevents over instrumentation  Prevents forcing debris or obturating material  Provides a stop, against which G.P can be compacted. .
  29. 29. Violating this integrity by over instrumentation leads to complications: (1)acute inflammation of the periradicular tissue from the injury inflicted by the instruments or bacteria and/or canal debris forced into the tissue, (2) chronic inflammation of this tissue caused by the presence of a foreign body—the filling material forced there during obturation, and (3)the inability to compact the root canal filling because of the loss of the limiting apical termination of the cavity—the important apical stop
  30. 30. A. Radiographic apex. B. Resistance Form, development of the "apical stop" at the Cementodentinal junction against which filling is to be compacted and a stop to resist extrusion of canal debris and filling material. C. Retention Form to retain primary filling point. D. Convenience Form subject to revision as needed to accommodate larger, less flexible instruments. External modifications change the Outline Form. E. Outline Form, basic preparation throughout its length dictated by canal anatomy.