This document discusses cleaning and shaping of the root canal during endodontic treatment. It describes the principles and techniques for preparing the coronal and radicular cavities, including outline form, convenience form, and resistance form. Various root canal preparation techniques are covered, such as step-back, step-down, hybrid, and balanced force techniques. Common root canal irrigants like sodium hypochlorite, hydrogen peroxide, EDTA, chlorhexidine, and MTAD are described in terms of their properties, mechanisms of action, advantages, and limitations.

1. CLEANING AND SHAPING OF
ROOT CANAL

2. Cleaning and shaping protocol
• Cleaning and shaping the root canal consists of removing the pulp tissue
and debris from the canal and shaping the canal to receive an obturation
material
• Using sequentially larger size of files and irrigating and disinfecting the
canal to clear it of debris , one shapes the canal to receive a well
condensed filling that seals the root canal apically and laterally to prevent
any leakage

3. Principles of endodontic cavity preparation
• List of preparations of endodontic cavity preparation is established by
slightly modifying “Principles Of Cavity Preparation“ established by
G.V.Black
• Endodontic preparations consists of both coronal and radicular
preparation each prepared separately but ultimately flowing together into
a single preparation

4. ENDODONTIC CORONAL CAVITY
PREPARATION:
• Outline form
• Convenience form
• Removal of the remaining carious
dentine( and defective
restorations)
• Toilet of the cavity
ENDODONTIC RADICULAR CAVITY
PREPARATION:
• Outline form and convenience
form(continued)
• Toilet of the cavity( continued)
• Resistance form
• Retention form

5. Coronal cavity preparation
PRINCIPLE 1: OUTLINE FORM
• The outline form must be correctly shaped to establish complete access for
instrumentation, from cavity margin to apical foramen
• To achieve optimal preparation, three factors of internal 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

6. PRINCIPLE 2: Convenience Form
• Convenience form was conceived by Black as a modification of the cavity outline form to
establish greater convenience in the placement of intracoronal restorations.
• In endodontic therapy, however, convenience form makes more convenient (and accurate)
the preparation and filling of the root canal.
• Four important benefits achieved through convenience form modifications are
1. Unobstructed access to the canal orifice
2. Direct access to the apical foramen
3. Cavity expansion to accommodate filling techniques
4. Complete authority over enlarging instruments

7. Principle 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

8. Principle 4: 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.
• Coronal debris may also stain particularly in anterior teeth

9. Principle 5: retention form
• The final 2-3mm of radicular wall should be nearly parallel to allow for a
snug fitting of gutta percha cone
• These final 2- 3mm of canal preparation is most crucial because this is
where the sealing against future percolation or leakage takes place

10. Resistance form
There are mainly two objectives of resistance form
• Resistance to overfilling is the primary objective of resistance form
• The other objective is maintaining the integrity of the natural constriction
of apical foramen. Voilating this integrity by overinstrumentation leads to
loss of apical patency, which makes proper compaction of gutta percha
cones difficult

11. OBJECTIVES OF ROOT CANAL PREPARATION

12. •Different techniques of
root canal preparation

14. Step back (Telescopic) technique
• The canal is enlarged first in the apical third to atlest a no 25 or 30
instrument and then each consecutively larger root canal instrument is
used for shaping the middle third and coronal part of the root canal
• Step back preparation is done in two phases
1. Phase1- apical preparation
2. Phase 2- preparation of the remaining canal by stepping back

16. Advantages
1. Better tactile awareness
2. Less chances of periapical trauma
3. The development of apical stop prevents overfilling of root canal
4. Greater condensation pressure can be exerted which often fills lateral
canals with the sealer

17. Disadvantages
• Apical extrusion of the debris through the apex
• Working length likely to change as canal curvatures are eliminated

18. Step down technique
• Also called as crown down pressureless technique
• Gates glidden drills or large sized files are used in the coronal 2/3rd of the
canal and progressively smaller files are used from the coronal
preparation until desired length is obtained

19. Advantages
• Eliminates the extrusion of the debris through the apex during
instrumentation
• Achieves complete cleansing of the canal.,Helps in achieving a
biocompatible seal at the apex
• Provides coronal escape way that reduces the piston in cylinder effect
responsible for debris extrusion from the apex
• Increased space for irrigation penetration and debridement

20. Disadvantages
Incresaed removl of tooth structure
Less tactile sensitivity

21. Hybrid technique
• Proposed by Goenig and Bauchman
• Uses both step down and step back concepts of preparation
• Early radicular access is obtained with Gates Glidden drill from no. 1 to 6
• The apical region is enlarged with step back technique

22. Balanced force technique
• Uses flex r file with non cutting tip
• Reaming action using clock wise insertion and by counter clockwise
cutting and removal with apical force
• The entire preparation is step down in nature beginning with flaring of
coronal and mid thirds of canal with gates glidden drill
• Clockwise rotation should never exceed 180 degree
• Counter clockwise rotation is 120 degree or greater

23. Balanced force or Roane technique

24. Root canal irrigants
• Every root canal system has spaces that can not be cleaned
mechanichaly .
• The only way to clean webs, fins and anastomoses is
through effective use of irrigation solution.
• in order to get the maximum efficiency from irrigant ,
irrigant must reach the apical portion of the canal .

25. Properties of ideal root canal irrigant
Anti microbial properties
Tissue solvent.
Flush debris.
Lubricant.
Eliminate the smear layer.
Low toxicity level

26. COMMONLY USED
IRRIGATING SOLUTIONS

27. • CHEMICALLY NONACTIVE
SOLVENTS:
1. Water
2. Saline
• CHEMICALLY ACTIVE SOLVENTS:
1. Alkalis : sodium hypochlorite
2. Antibacterial agents :
chlorhexidine
3. Oxidizing agents: hydrogen
peroxide
4. Chelating agents: EDTA ( ethylene
diamine tetra acetic acid)
5. MTAD

28. Sodium hypochlorite
• Sodium hypochlorite, a reducing agent, is a clear straw coloured solution
containing about 5% free available chlorine
• Naocl produces hypochlorus acid and hypochlorite ion, these are
responsible for the antimicrobial ability of Naocl
• NaOCl has tissue dissolving prope

29. Mechanisam of action
 Sodium hypochlorite (NaOCl) ionizes in water into Na and the
hypochlorite ion, OCl, establishing an equilibrium with hypochlorous acid
(HOCl).
 Hypochlorous acid is responsible for the antibacterial activity; the OCl
ion is less effective than the undissolved HOCl.
 Hypochloric acid disrupts several vital functions of the microbial cell,
resulting in cell death.

30. Concentration and temperature
• 0.5%-5.2% solution is an effective concentration for use as an irrigant.
• 2.5% Naocl is a commonly employed concentration as it decreases the
potential for toxicity while maintaining some tissue dissolving and
antimicrobial activity
• Increasing the temperature of hypochlorite irrigant to 600C, significantly
increased its antimicrobial and tissue-dissolving effects.

31. Drawbacks of sodium hypochlorite
• Cytotoxicity and toxic effects on healthy periradicular tissues on
inadvertent extrusion during the irrigation procedure.
• It doesnot remove the inorganic portion of smear layer.
• Unpleasant taste.
• Solution should be kept in a cool place away from sunlight

32. Sodium hypochlorite accident
 Immediate severe pain for 2-6 minutes.
 immediate edema in adjacent soft tissue because of perfusion to the
loose connective tissue.
 Extension of edema to a large site of the face such as cheeks, peri-orbital
region, or lips.
 Ecchymosis on skin or mucosa as a result of profuse interstitial
bleeding.

33. Management
 inform the patient about the cause and nature of the complication.
Immediately irrigate with normal saline to decrease the soft-tissue irritation by diluting
the NaOCl.
 Let the bleeding response continue as it helps to flush the irritant out of the tissues.
 Recommend ice bag compresses for 24 hours (15-minute intervals)to minimize swelling.
 Recommend warm, moist compresses after 24 hours (15-minute intervals).
 pain control with strong analgesics for 3 to 7 days
 Prophylactic antibiotic coverage for 7 to 10 days to prevent secondary infection or
spreading of the present infection.

34. HYDROGEN PEROXIDE
 It is a clear, colorless , odorless liquid.
 H2O2 is active against viruses, bacteria, and yeasts.
 It has been particularly popular in cleaning the pulp chamber from blood
and tissue remnants, but it has also been used in canal irrigation.

35. Mechanisam of action
 It is highly unstable and easily decomposed by heat and light.
 it rapidly dissociate into H2O+O (water+nascent oxygen) . The liberated
nascent oxygen has bactericidal effect but this effect is transient and diminishes
in presence of organic debris .
 The rapid release of nascent oxygen on contact with organic tissue results in
effervesce (bubbling) action which aid in mechanical debridement by
dislodging dentin debris and necrotic tissue particles and floating them to the
surface.

36. • It is recommended to use in 3% conentration for endodontic irrigation.
Advantages of using alternating 3%H2O2 with Naocl solution are :
1.Effervescent reaction (bubbles pushes debris mechanichally out of root canal)
2.Solvent action of sodium hypochrorite on organic debris.
3.Disinfection and bleaching effect by both solutions.

37. Limitations
 Unable to remove smear layer.
 Always use NaOCl last because Hydrogen peroxide release of nascent
oxygen on contact with organic tissue which may build up pressure on
closing tooth and causes pain .
• Soft tissue emphysema may occur when hydrogen peroxide irrigant
enforced beyond the apical foramen.

38. EDTA
• EDTA was introduced into endodontic practice by Nygaard Ostby.
• Relatively nontoxic and non irritating
• Forms highly soluble metal chelates in combination with heavy metals
• Functions by forming a calcium chelate solution with the calcium ion in
dentin.thus can remove the inorganic portion of smear layer
• The recommended regime for irrigation is to employ 17% EDTA for 1
minute followed by a final rinse with NaOCl

39. CHLORHEXIDINE DIGLUCONATE
• 2% chlorhexidine digluconate possess broad spectrum antimicrobial
activity against most common endodontic pathogens
• CHX is very effective against Enterococcus faecalis, most common
pathogen found in root canal filled teeth exhibiting clinical failure
• CHX shows sustained activity in canal due to its property of
“substantivity”
• Since CHX does not remove the smear layer it should be employed with
other irrigants in conjunction

40. MTAD
• MTAD employs a mixture of a tetracycline isomer( doxycycline) citric
acid,and a detergent “TWEEN 80” as a final rinse to remove the smear
layer
• It is commonly employed after irrigation with 1.3% NaOCl
• The combination of MTAD and NaOCl has been advocated to remove the
smear layer and also has substantial antimicrobial efficacy

41. Thank you