Root canal instrumentation

CLEANING AND SHAPINGOF ROOT CANAL SYSTEM

INTRODUCTION
DEFINITIONS
Cleaning: removal of all potentially pathogenic contents from root canal

Shaping: dual action – 3D prgogressive access apical preperation to permit final obturation instruments & materials to fit easily

MECHANICAL OBJECTIVES

• CONTINUOUS TAPERING CONICAL SHAPE
• NARROW APICALLY AND WIDEST CORONALLY
• APICAL FORAMEN AS NARROW AS POSSIBLE
• AVOID TRANSPOTATION OF APICAL FORAMEN
• CREATION OF SUFFICIENT SPACE FOR OBTURATING MATERIAL
• MAINTAIN ORIGINAL CANAL ANATOMY
• MAINTAIN ORIGINAL CANAL CURVATURE

BIOLOGICAL OBJECTIVES

• NECROTIC DEBRIS NOT FORCED PERIAPICALLY
• COMPLETE REMOVAL OF TISSUE FROM THE CANAL SPACE
• COMPLETE REMOVAL OF MICROORGANISMS
• REMOVAL OF SMEAR LAYER


PRINCIPLES OF CANAL INSTRUMENTATION
STRAIGHT LINE ACCESS OF THR FILE
PRECURVING THE APICAL PART OF FILE
RETAINING ITS ORIGINAL FORM & SHAPE
IRRIGATION
RECAPITULATION
REMOVAL OF DENTINAL DEBRIS
EDTA PASTE
NEVER APPLY APICAL PRESSURE
NEVER ENGAGE THE FILE TO DENTIN
EXAMINATION OF FILE SHAPE BEFORE UES IT
MEASURE THE LENGTH OF FILE AFTER REMOVAL FROM THE CANAL

PHASES IN SHAPING OF ROOT CANAL

• NEGOTIATION (PATENCY FILING)
• CORONAL PRE-ENLARGEMENT
• WORKING LENGTH DETERMINATION
• SHAPING TECHNIQUES


PATENCY FILING
• PRECURVED SIZE 10 FILE / STAINLESS K FILE
• REAMING MOTION
• IN CALCIFIED CANALS OR WITH OBSTRUCTIONS, ISO SIZE 8 FILE OR SIZE 6 K FILE
• CREATING A PATH PASSIVELY TO THE APICAL FORAMEN (Glide path)
• HELPS IN MAINTAINING A CONTINUOUS & CLEAR PATH FROM THE ORIFICE TO THE APEX

CORONAL PRE-ENLARGEMENT

ADVANTAGES:
• REDUCED POTENTIAL OF EXCTROSION DEBRIS BEYOND APEX
• APICAL GAUGING MORE ACCURATE
• PREVENTS PREMATURE BINDING OF INSTRUMENTS TO CANAL WALLS
• BETTER IRRIGATION
• BETTER VISION

TECHNIQUES

STEP BACK TECHNIQUE CROWN DOWN TECHNIQUE

HYBRID TECHNIQUE

Advantages of Crown-down technique
• Elimination of microbes and infected dentin
• Less extrusion of derbies apically
• Less postoperative pain and tenderness
• Better and deeper penetration of irrigant
• Less strain and physical load on the file apically
• Less possibility of ledge formation and file separation
• Provide more tactile sensation in the apical 1/3rd
• Less time for preparation

STEP BACK TECHNIQUE

• No 10 & No 15 FILE INSERTED TILL WORKING LENGTH; USE IN REAMING MOTION
• APICAL ENLARGEMENT TO DEVELOP APICAL STOP ATLEAST 3 SIZES (25 FILE SIZE)
• INCREAZE FILE SIZE PROGRESSIVELY & WORKING SHORT BY 1 MM

• RECAPITULATION
• AFTER PREPARING THE BODY OF CANAL, 2 & 3 GATES GLIDEN DRILLS ARE USED FOR CORONAL PREPARATION
• CIRCUMFERENTIAL FILING USING MAF

CROWN DOWN TECHNIQUE

• CORONAL FLARING WITH GG DRILLS NO 2 OR 3 WITH EACH FILE BEING SEQUENTIALLY SHORTER
• A LARGE FILE (SIZE 60) IS PLACED IN CORONAL ASPECT & CANAL IS INSTRUMENTED IN WATCH WINDING MOTION
• SEQUENTIALLY SMALLER FILES + 1mm TILL WORKING LENGTH
• APICAL ENLARGEMENT WITH MAF
• FINAL TAPER WITH CIRCUMFERRENTIAL FILING