Techniques of Biomechanical preparation and different types

Biomechanical preparation

1. TECHNIQUES OF BIOMECHANICAL PREPARATION DR. SIMRAN

2. INTRODUCTION The major objective of the intra canal treatment procedures is to remove the contents of the canal and adjacent tissues in such a way that the filling procedures that follow will be facilitated. This means not only that the pulp tissue, necrotic debris, microorganisms, and affected dentin must be removed from the treated tooth, but also that the canal walls must be prepared to receive a filling material that will seal the apical foramen. OBJECTIVES A. MECHANICAL OBJECTIVES B. BIOLOGICAL OBJECTIVES

3. MECHANICAL OBJECTIVES: Continuous tapering conical shape Narrow apically and widest coronally Concept of flow - with the shape of original canal Apical foramen as narrow as possible Avoid transportation of apical foramen

4. BIOLOGICAL OBJECTIVES: Confinement of instrument to the roots Necrotic debris not forced periapical Complete removal of tissue from the canal space Sufficient space for obturating material

5. RULES GOVERNING BIOMECHANICAL PREPARATION 1. Direct access should be obtained along straight lines. 2. Smooth instruments should precede rough instruments. 3. The length of the tooth should be accurately determined. 4. Instruments should be used in sequence of sizes. 5. Reamers to be given ¼ to ½ turn. 6. Files to be used with pull motion. 7. Reamers and files to be used with instrument stops. 8. The canals should be enlarged at least three sizes greater than its original diameter. 9. A reamer or a file should not be forced if it binds into the canal. 10. All instrumentation should be done in a wet canal

6. TECHNIQUES OF ROOT CANAL PREPARATION

7. STEP-BACK TECHNIQUE Conventional step-back (Telescopic) technique Aim at a higher conicity by stepwise reduction of working length, once apical preparation has been finished with the MAF. Each step back is followed by irrigation and recapitulation with a small file. Enlarged first in apical third to atleast a no. 25 or 30 instrument. Each consecutively larger root canal instrument for middle third and coronal part.

8. Passive step-back technique Introduced by Torbinejad . Insertion of progressively larger hand instruments as deep as they can be passively placed. GG Drills are used for additional coronal enlargement followed by apical instrumentation using the step-back technique.

9. Advantages Popular technique employed with 2% standardized stainless steel files. Ability to prepare a proper apical stop prior to preparation of the middle third and coronal third of the root canal. Disadvantages Extrusion of debris into the periapex. Tendency to straighten in the canal. Loss of working length.

10. CROWN-DOWN TECHNIQUE Goerig et al. Following coronal flaring, large instruments are used to enter and enlarge the root canal a few millimetres apically each time. The instrument is followed by a smaller file, preparing only a few millimetres deeper than the previous instrument. This is repeated until working length is reached.

11. Advantages Less friction and stress on the instrument. Less canal straightening since reduced friction allows a more controlled preparation. Less contamination of the apical zone of the root canal by reducing transportation of infected debris. Early coronal and mid-root enlargement allowing early disinfection of the coronal parts of the root canal system. Reduction of extruded debris beyond the apical foramen. Disadvantages Coronal portion can be over prepared Could result in ledges and blockages with over zealous use of files

12. MODIFICATIONS OF CROWN-DOWN TECHNIQUE Crown down pressure less technique Double flare technique Balanced force technique

13. BALANCED FORCE TECHNIQUE Using Flex-R files The technique utilizes a clockwise rotation of the file up to 180 degrees to engage dentin, followed by a counterclockwise rotation of at least 120 degrees with apical force to shear off the engaged dentin; this cut is apparently perceptible as a subtle tactile "pop”. The balanced force technique has been advocated for curved canals; it has been claimed to allow the use of larger unprecurved files without canal transportation or ledging.

14. HYBRID TECHNIQUE

15. Advantages: Optimizes the advantages of crown down and step back techniques Disadvantages: Middle third preparation has to be done carefully in order to prepare a continuous tapered canal preparation

16. Challenges of root canal preparation Anatomical factors complexity of the anatomy of the root canal system (number, length, curvature and diameter of root canals); the complexity of the apical anatomy with accessory canals and ramifications; communications between the canal space and the lateral periodontium and the furcation area; the anatomy of the peripheral root dentine Microbiological challenges Both pulp tissue and root dentine may harbour microorganisms and toxins

17. Iatrogenic damage caused by root canal preparation Zipping Elbow Ledging Perforation Strip perforation Outer widening Apical blockage

18. Zipping Tendency of the instrument to straighten inside a curved root canal. This results in over-enlargement of the canal along the outer side of the curvature and under-preparation of the inner aspect of the curvature at the apical end point

19. Elbow Associated with zipping and describes a narrow region of the root canal at the point of maximum curvature as a result of the irregular widening that occurs coronally along the inner aspect and apically along the outer aspect of the curve.

20. Ledging As a result of preparation with inflexible instruments with a sharp, inflexible cutting tip particularly when used in a rotational motion.

21. Perforation Perforations are associated with destruction of the root cementum and irritation and/or infection of the periodontal ligament and are difficult to seal.

22. Strip perforation Strip perforations result from over-preparation and straightening along the inner aspect of the root canal curvature These midroot perforations are again associated with destruction of the root cementum and irritation of the periodontal ligament and are difficult to seal. The radicular walls to the furcal aspect of roots are often extremely thin and were hence termed ‘danger zones’

23. Outer widening First described by Bryant et al. ‘outer widening’ describes an over-preparation and straightening along the outer side of the curve without displacement of the apical foramen. This phenomenon until now has been detected only following preparation of simulated canals in resin blocks.

24. Apical blockage Apical blockage of the root canal occurs as a result of packing of tissue or debris and results in a loss of working length and of root canal patency As a consequence complete disinfection of the most apical part of the root canal system is impossible.

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