Disinfection of the Root Canal Space
ESCN Session 5
Robert S. Roda DDS MS
http://web.mac.com/robertroda

Purpose of Root Canal Therapy
o To prevent and cure apical periodontitis

An inflammatory process in the periradicular tissues caused by microorganisms in
the infected root canal

Initial Infection
o Mostly gram negative and anaerobic
o eg. Fusobacterium

Post-Treatment Infection
o Gram positive facultative anaerobes
o eg. Enterococcus faecalis

Microorganisms
o Two forms:
 Planktonic
 Sessile
 Forms a biofilm

Biofilm Composition
o Bacteria
o Polysaccharide Extracellular Matrix
 Protection
 Signaling
 Nutrition

Biofilm
o Five Stages of Biofilm Development
1. Reversible attachment
2. Irreversible attachment
3. Matrix secretion
4. Growth
5. Differentiation
 Detachment

Biofilm
o After attachment to a surface, a bacterium expresses a different set of
genes
o Microorganisms in biofilms have reduced susceptibility to antimicrobial
agents
o Biofilms adapt to changing conditions
o Becomes more persistent under stress
o Less susceptible to second application of disinfectants
o Bacteria can transfer acquired resistance to other bacteria

Bacteria in Dentinal Tubules

Aim of Endodontic Therapy
o Removal of the biofilm from the canal space and prevention of reinfection
Two Stages of Root Canal Therapy
o Reduce / Eliminate Bacteria
 Mechanical canal preparation
 Chemical disinfection

o Prevent Re-infection
 Apical seal
 Sealed obturation
 Coronal Seal
 Sealed Restoration

Mechanical Preparation
o Removal of most organic substrate from the canal system
o Development of a purposeful form
 to allow deep penetration by irrigants
 for reception of a dense root filling

Mechanical Preparation
o Broaches
o Hand files
o Rotary files
o Ultrasonically activated files
o Sonically activated files
o Lasers


Instruments Don’t Get Everything
Instruments Create Smear Layer

Smear Layer
o A layer of debris on dentin
 Organic component
 Collagen, bacteria, pulp remnants
 Inorganic component
 Dentin chips
 Foreign debris (insoluble)
o Created by mechanical scraping of dentin

Affects:
o Restorative dentistry (bonding)
o Periodontics (regeneration)
o Endodontics? (disinfection and seal)

Should it be removed?
o Yes:
 Potentially infected material / substrate
 Prevents disinfectants and filling materials from getting into
tubules
 Detriment to apical seal
o No:
 Enhances apical seal
 Does not affect prognosis
 Removal may weaken teeth

Chemical Disinfection
o Irrigation
 Passive
 Active
o Inter-appointment Medicaments
 Phenolic
 Calcium hydroxide

Effectiveness is Proximity Dependant

Irrigants
o Distilled water
o NaOCl
o EDTA
o Chlorhexidine

Distilled Water
o No antibacterial action
o Does not dissolve tissue

Sodium Hypochlorite
o 6% vs 3% NaOCl
o Kills some bacteria (E. faecalis is resistant)
o Dissolves necrotic tissue
o Does not remove smear layer
o Reduces bonding strength
o Current Irrigant of Choice

EDTA
o Kills some bacteria?
o Removes smear layer
o Erosion of dentin

Chlorhexidine
o 0.12% vs 2%
o Kills some bacteria (similar to NaOCl)
o Kills E faecalis
o Does not dissolve tissue
o Toxicity?
 Tissue Fixitive
 Carcinogenic byproducts?

Smear Layer Removal
o Two stage chemical process
o Remove inorganic component
 Mild acids (chelation)
 EDTA
 Citric acid
 Phosphoric acid
 Tetracycline
o Remove organic component
 Sodium hypochlorite

Current Disinfection Technique
o Irrigate thoroughly with NaOCl
o Evacuate NaOCl
o Syringe EDTA into canal (1-2 min)
o Evacuate EDTA
o Flush with NaOCl (1 min minimum)
o Evacuate NaOCl
o Flush with 2% CHX (5 min)
o Use paper points to dry

BioPure™ MTAD™ Cleanser
o Mixture of Tetracycline and Acid - Detergent
o Detergent (Tween 80) ™ acts as a surfactant - facilitates penetration
o Citric acid removes smear layer
o Doxycycline
 removes smear layer
 kills resistant bacteria
o Removes Smear Layer

Properties of MTAD
o Effective when combined with any concentration of NaOCl over 1.3%
o Kills E. faecalis better than 2% CHX
o Kills bacteria in whole saliva better than NaOCl
o Sustained effect? (binds to dentin)
o Biocompatibility > EDTA, 0.12% CHX, 5.25% NaOCl
o Does not affect flexural strength of dentin
o Does not decrease bond strength of dentin
o FDA Approved 2004
o Allergenicity
 True allergy is rare
 Do not use in pregnant women or children under age 8

MTAD™ Cleanser Technique
o Irrigate thoroughly with NaOCl
o Evacuate NaOCl
o Syringe 1ml BioPure MTAD cleanser into canal (5 min)
o Flush with 4ml BioPure MTAD cleanser
o Use paper points to dry

QMix 2in1
o EDTA and Chlorhexidine
o Removes smear layer
o Kills planktonic bacteria
o Kills biofilm bacteria

QMix Protocol
o Irrigate with NaOCl throughout
o Dry canals
o QMix for 90 sec
o Dry Canals
o Obturate

Increase Irrigant Effectiveness
o Volume
o Concentration
Temperature
Agitation
o Combination - NaOCl + ProLube® or RC Prep ®
o Change solution frequently
o Increase time of contact

Irrigation - Two Types
o Passive
 Allow the irrigant to passively work
 Soaking
o Active
 Add heat or agitation
 Increase irrigant action
 Tissue dissolution
 Increase antimicrobial action
 Increase irrigant flow
 Clean canal iregularities

Passive Irrigation
o Soaking
o EDTA 1-2 minutes
o NaOCl 1/2 hour*
o The longer the better

Active Irrigation
o Manual Dynamic
o Sonic
o Ultrasonic
o EndoActivator
o EndoVac
o Ultrasonic Irrigation

Manual Dynamic Irrigation
o Manual push-pull motion
o Use a fitted master gutta percha cone
o Forces irrigants into canal ramifications

Sonic Instruments (2-3 kHz)
o Sonic Handpieces (Micromega 1500/3000)
o sonic vibrations created by air/water jet
o vibrates in a figure eight motion
o difficult to control tip movement
o canal walls left rough (creates smear layer)
o slow
o relatively less expensive than ultrasonic
o best use is for coronal instrumentation and for irrigation

Ultrasonic Instruments (25-30 kHz)
o piezo-electric energy applied to files
o
o
o
o
o
o
acoustic streaming (cavitation?)
used for canal flaring (middle, coronal 1/3)
creates (removes) smear layer?
removal of debris from inaccessible fins
can use hypochlorite for irrigant (tube damage)
potential for instrument fracture

Ultrasonic Instruments (25-30 kHz)
o Ultra-sonic operates in a linear motion.
o Controlled tip motion.
o More energy through a predictable range of motion.
o Low Power Setting – 1 to 5
o Must use a light paint brush stroke
o Cleaning Webs and Fins
o C-Shaped Canals

EndoActivator
o Soft plastic tips
o Does not create smear layer
o Battery operated (cordless)
o Sub-sonic oscillation (10000 rpm max)

EndoVac
o Attach suction to modified irrigation needle

Ultrasonic Irrigation
o Irrigation needle attached to ultrasonic
o Hypochlorite overextension?

Minimally Invasive Endodontics
o Conserve peri-cervical dentin
o Attempt to reduce incidence of fracture
o Minimize size of access
o Minimize size of root canal preparation

OneStudy
o Compared TEC and CEC
o WaveOne instrumentation
o Static Fx load Instron)
o Canal cleanliness - micro CT
o TEC – less load to Fx in premolars and molars (incisors unaffected)
o CEC – compromised canal cleaning only in lower molar distal roots