Objectives of Canal Preparation

Start with the end in mind

Objectives of root canal preparation

The root canal system must be:• Cleaned of its organic remnants• Shaped to receive a three

dimensional filling of the entire root canal space

Objectives of root canal preparation

The canal is • Cleansed primarily by irrigation• Shaped primarily by

instrumentation

Five Mechanical objectives

•Develop a continuously tapering conical form in the root canal preparation•Make the canal narrower apically, with the narrowest cross-sectional diameter at its terminus•Make the preparation in multiple planes•Never transport the foramen.•Keep the apical foramen as small as possible Herbert Schilder

The real key to obturation is Cleaning and Shaping

Cleansing of the root canal

Objectives• Removal of organic and

inorganic debris• Elimination of bacteria

InstrumentsInstruments differ according to:• Metal• Tip design• Cross sectional geometry• Length of cutting blades• Sizing• Taper

Metals

Nickel titanium Stainless steel

Excellent flexibility Less flexible

Conforms to canal Straightens and curvature transports canal

No deformationPermanent deformation

ISO-Symbols

= K-Reamer

= K-File

= H-File

= Rat Tail File

= Nervbroach

= Paste Filler

METHODS OF DETERMININGWORKING LENGTH

• Radiographic Methods• Digital Tactile Sense• Apical Periodontal Sensitivity• Paper Point Measurement• Electronics

Clinical Technique

Actual WL determination• Radiograph• Apex locator

Clinical Procedure

Apex Locator

Clinical Procedure

Actual WL determinationPreparation should terminate at• Apical constriction• 1 mm short of radiographic

apex

Clinical Procedure

• Estimate working length• Parallel radiograph• Estimated working length is the distance

from the reference point to the radiographic apex

• Apico coronal techniques( standardized ,step-back, balanced force )

• Corono-apical techniques ( step-down , Double flared, crown-down-pressureless)

Root canal preparation

• Standard technique• Step-back technique• Serial shaping technique• Anti-curvature filing• Balance force

preparation• Crown down technique

Instrumentation

• Motion of instrumentation:Filing and Reaming

• Combination with reaming and filing:

1. Turn-and-Pull2. Watch-Winding3. Watch-Winding-and-Pull

• Anti-curvature filing

Step-back technique

Step-back technique

Master Apical File

• Take a radiograph with MAF in place. This confirms:– Length– Placement

RECAPITULATIONRepeated reintroduction and reapplication of instruments

previously used throughout the cleaning and shaping process in

order to create well-designed, smooth, unclogged, evenly tapered

root canal preparations.

Apical PatencyMaintain a pathway

through the apical constriction with a small K-file (#10 or #15)

during cleaning and shaping

Other methods ;

Crown Down Technique

•Coronal third Orifice shapers•Middle third 0.06 taper rotary Profiles•Apical third 0.04 taper hand Profiles

Crown Down Technique

• The coronal portion is prepared before the apical portion

• Reduces effect of canal curvature• Improves tactile awareness during apical

preparation• Allows more effective irrigation• Removes majority of tissue and microbes

before apical third is approached• Reduces change in working length during

apical preparation

Anti-curvature filing

Irrigation

An ideal irrigant:• Is nontoxic • Dissolves vital and necrotic tissue• Is bactericidal• Lubricates the canal

• Sodium Hypochlorite:• Lower concentrations (e.g., 0.5% or1%) dissolve mainly

necrotic tissue

• Chlorhexidine:• A broad-spectrum antimicrobial agent effective against

gram-negative and gram-positive bacteria• A cationic molecular• binds to hydroxyapatite

Iodine Potassium Iodide:• an oxidizing agent by reacting with free sulfhydryl

groups of bacterial enzymes• MTAD• EDTA• Hydrogen peroxide

Cleaning---Irrigation

• Sodium Hypochlorite?• Dissolves organic debris ✔• Has a powerful anti-bacterial action ✔• Lubricates the use of files ✔• Disinfects & cleans where files don’t reach

✔• The tissue-dissolving ability of 5.25-

1%

What irrigant should we use?

Sodium hypochlorite

• Dissolves vital and necrotic tissue

• Is bactericidal• Lubricates the canal

Smear layer

• What is the smear layer ?

• Remove ?

Prolube

• Facilitates placement of file• Entraps debris• Aids in removal of the smear

layer

EDTA and carbamide peroxide in a water soluble base

Good luck