Quartz 4

L3 Anti-bacterial Strategies

14 min read

Anti-Bacterial Strategies in Endodontics1

  • Endodontic Microbiology
  • Irrigation

Endodontic Microbiology2

Progression of Pulp Disease

flowchart TD
    A[Healthy Tissue] -->|*** Injury or stimulus| B(Inflammation)
    subgraph Progression of Pulp Diseases
    B --> C(Necrosis)
    C --> D[Infection]
    D --> E[Tissue Destruction]
    end
    F[Bacteria] --> A
    B -->|*** If no treatment| C

Main Cause of Pulp Disease: Bacteria

Info

The primary stimulus for pulp and periapical disease is bacteria. Understanding the pathways of entry is fundamental to endodontic treatment.

  • Possible pathways of entry into teeth:
    • Caries
    • Cracks
    • Restorations breaking down
    • Fractures - tooth, restorations
    • Trauma - luxations, etc
    • Periodontal disease

First Step

The first step in treatment is to identify and eliminate these pathways.

The Role of Bacteria in Pulp & Periapical Diseases3

Evidence from Foundational Studies4

  • Kakehashi et al - 1965, 1969
    • Exposed pulps and left open to the oral cavity:
      • Germ-free rats → Pulps healed
      • Normal rats → Pulps degenerated & necrosed

Conclusion

This was the first definitive proof that bacteria are the primary cause of pulp necrosis and subsequent periapical disease following pulp exposure.

  • Korzen et al - 1974

    • Periapical inflammation was:
      • Directly related to bacterial invasion of the canal
      • More severe when bacteria were found along the entire length of the canal

  • Möller et al - 1981; Fabricius et al - 1982

    • No periapical inflammation with necrotic pulps
    • Inflammation was found only when the canals were infected

  • Sundqvist - 1976

  • This thesis examined traumatized teeth with necrotic pulps that appeared “closed” but were likely infected via micro-cracks.

    • Examined “closed” traumatised teeth

    • Periapical inflammation was found only in cases with infected canals

      • Always found > 1 strain
      • Up to 12 strains isolated
      • Size of radiolucency directly related to the number of strains isolated
      • Patients with pain had > 6 strains
      • Acute inflammation ⇒ more strains present

Note

Modern techniques like PCR can now identify hundreds of different strains, far more than what was possible in the 1970s.

Common Endodontic Microbes5

Common Genera in Infected Root Canals

  • ==The majority of bacteria in established, long-standing infections are obligate anaerobes.==
  • ==Facultative anaerobes are also present.==
  • ==Aerobic bacteria may be found, typically in the coronal parts of the canal where oxygen access is greater.==
  • The flora includes a mix of gram-positive and gram-negative cocci and rods.
Obligate anaerobesFacultative anaerobes
Gram-positive cocciGram-positive cocci
* Streptococcus* Streptococcus
* Peptostreptococcus* Enterococcus
Gram-positive rodsGram-positive rods
* Actinomyces* Actinomyces
* Lactobacillus* Lactobacillus
* Bifidobacterium
* Propionibacterium
* Eubacterium
Gram-negative cocciGram-negative cocci
* Veillonella* Neisseria
Gram-negative rodsGram-negative rods
* Porphyromonas* Capnocytophaga
* Prevotella* Eikenella
* Fusobacterium
* Selenomonas
* Campylobacter
SpirochetesYeasts
* Treponema* Candida

Commonly Reported Endodontic Microbes (from Sundqvist 1996)6

GROUP A - ANAEROBIC BACTERIA (Obligate, non-sporulating)

GroupMorphologyExamples
Gram-negative rodsPorphyromonas, Prevotella (formerly Bacteroides) - B. buccae, B. oris, B. denticola, B. endodontalis, B. gingivalis, B. loeschei, B. melaninogenica, B. oralis, B. ureolyticus
Fusobacterium - F. nucleatum
Wolinella - W. recta, W. curva
Selenomonas - S. sputigena
Gram-negative cocciVeillonella - V. parvula
Gram-positive rodsActinomyces - A. israelii, A. odontolyticus, A. meyeri
Eubacterium - E. alactolyticum, E. brachy, E. lentum, E. nodatum
Lactobaillus (anaerobic) - L. catamaeforme, L. minutus
Propionibacterium - P. acnes
Arachnia - A. propionica
Gram-positive cocciPeptostreptococcus - P. anaerobius, P. magnus, P. micros, P. prevotii
Streptococcus - S. constellatus, S. intermedius, S. morbillorum

GROUP B - AEROBIC & FACULTATIVELY ANAEROBIC BACTERIA

GroupMorphologyExamples
Gram-negative rodsCapnocytophanga - C. ochracea
Eikenella - E. corrodens
Campylobacter - C. sputoum
Gram-positive rodsActinomyces - A. naeslundii, A. viscosus
Gram-positive cocciStreptococcus - S. mutans, S. mitis, S. milleri, S. sanguis, S. faecalis

Conditions Favourable for Bacterial Colonisation of Root Canals7

  • Space

  • A necrotic pulp leaves a void that bacteria can occupy.

  • Co-colonising organisms

  • The infection is polymicrobial. Different species support each other in a symbiotic relationship, where the metabolic byproducts of one group serve as nutrients for another.

flowchart TD
    subgraph Bacterium Group 1
        A[FUSOBACTEREUM]
        B[BUBACTERIUM]
        C[PEPTOSTREPTOCOCCUS]
    end
    subgraph Bacterium Group 2
        D[CAPNOCYTOPHAGA]
    end
    subgraph Bacterium Group 3
        E[STREPTOCOCCUS]
        F[ACTINOMYCES]
    end
    subgraph Bacterium Group 4
        G[VEILLONELLA]
    end
    subgraph Bacterium Group 5
        H[CAMPYLOBACTER]
    end
    
    A --> D
    A --> E
    A --> G
    A --> H
    B --> A
    B --> E
    C --> A
    C --> G
    D --> E
    D --> G
    E --> F
    F --> G
    G --> H
    H --> A

  • Low oxygen tension

  • The enclosed environment, especially towards the apex, is low in oxygen, favouring the growth of pathogenic anaerobic bacteria.

  • Nutrients

    • Pulp tissue remnants
    • Necrotic debris
    • Saliva
    • Foods
    • Inflammatory exudate, etc

Bacterial Distribution and Proliferation8

  • ==Apical vs. Coronal: The apical third of the canal is more anaerobic than the coronal portion.==

  • ==Canal vs. Tubules: As bacteria penetrate the dentinal tubules, the environment becomes progressively more anaerobic.==

  • ==Over time, the more pathogenic anaerobic bacteria tend to dominate the ecosystem.==

  • Fabricius et al 1982

    • Types of bacteria in different parts of the root:
Type of BacteriaRoot CanalWithin DentineApical Third
Facultative AnaerobesMediumLowVery Low
AnaerobesMediumMedium-HighHigh
  • Also more anaerobes with more TIME

Guiding Principle9

  • Louis Pasteur
    • “Don’t worry about the bacteria …..
    • …. it is the environment in which they live that is important”

Goal of Treatment

The goal of treatment is to alter this favourable environment to make it inhospitable for bacteria.

Aims of Endodontic Treatment10

× What should we aim to achieve?

Biological Aims11

Warning

These are the most critical aims of treatment.

  • To remove from the root canal system all organic material that is capable of either decomposing into tissue destructive by-products or that can support bacterial growth;

  • To remove or destroy all the micro-organisms present in the root canal system

Mechanical Aims1213

Info

These are the procedures used to achieve the biological aims.

  • To prepare the root canal space to a form which allows complete filling;

  • To fill the prepared canal space with a biocompatible filling material in order to completely seal the coronal and apical ends of the canal. The apical end of the root filling should be placed as close as possible to the cemento-dentinal junction.

The Three Stages of Filling

The

An Interesting Case

A patient presented with an infected lower first molar with periapical radiolucencies. Initial treatment involved removing caries and placing a medicament. The patient did not return for 2.5 years. Upon their return, radiographs showed significant healing of the periapical bone, even though the final root canal filling had not been placed.

This case highlights a crucial concept: The success of endodontic treatment depends primarily on cleaning and disinfecting the canal system, not just on the final root filling.

The treatment can be viewed in two stages:

  1. Stage 1: Treat the Presenting Problem. This involves diagnosis, removing the cause (caries, old restorations), and disinfecting the canal system through instrumentation, irrigation, and inter-appointment medicaments. This stage addresses the active infection and symptoms.
  2. Stage 2: Prevent Future Infection. This is achieved by placing a well-sealed root canal filling and a high-quality coronal restoration to prevent reinfection.

10 minutes - 1ml of 1% NaOCl

  • Good anti-microbial action

  • Leaves Smear Layer

Sodium Hypochlorite (NaOCl)

NaOCl is a powerful agent with several key properties.

  • Tissue Dissolution: It is highly effective at dissolving organic tissue. A demonstration showed that a large piece of necrotic pulp almost completely dissolved after 10 minutes in 1% NaOCl.
  • Antibacterial Efficacy: It is an excellent broad-spectrum antibacterial agent.

Evidence and Studies1415

  • Baumgartner & Cuenin - JoE 1992

    • Tissue Dissolution:

      • 1%, 2.5%, 5.25% - removed all pulp remnants and predentin → no difference
      • 0.5% - removed most but not all

    • Smear Layer:

      • But ALL concentrations left Smear Layer when the canal walls were instrumented
No pulp debris; no predentineNo pulp/predentine; Smear Layer
1% NaOCl No instrumentation1% NaOCl + instrumentation
Pulp debrisBaumgartner
No irrigant; No instrumentation& Cuenin - 1992

  • Byström & Sundqvist - 1983

    • Saline some flushing action only
      • But >50% of canals still had bacteria after 5 visits
    • 0.5% NaOCl - an effective anti-bacterial agent

  • Byström & Sundqvist - 1985

    • 0.5% and 5% NaOCl - no difference in their anti-bacterial effectiveness

  • Antibacterial Action of Endodontic Irrigants (D’Arcangelo et al, J Endod 1999)

    • NaOCl - bactericidal for ALL 13 species tested
    • Used different concentrations of NaOCl
      • 0.5%, 1%, 3%, and 5%
      • NO difference between concentrations
    • NO organisms viable after 10 minutes of contact with each concentration

Concentration Considerations1617

  • ==Optimal Concentration (1%): Provides the best balance of properties. It has excellent antibacterial and tissue-dissolving capabilities, equivalent to higher concentrations, but with significantly lower toxicity. Therefore, 1% NaOCl is the preferred concentration.==

  • 1% - preferred concentration:

    • Good anti-bacterial action
    • Good tissue dissolving ability, and
    • Lower toxicity

  • 0.5%

    • Slightly less toxic, good antibacterial activity
    • but poor tissue dissolving action

  • 2.5% and 5.25%

    • Good antibacterial and tissue dissolving actions BUT VERY TOXIC

The “Smear Layer”1819

Definition and Composition

  • A layer of moistened debris compacted against the canal walls during instrumentation
    • A result of the filing / rasping action of files
  • Consists mainly of inorganic matter
    • Has some organic matter & tissue remnants
    • Can contain bacteria

Note

When NaOCl is used as the irrigant during instrumentation, the resulting smear layer is primarily inorganic, as the NaOCl dissolves most of the organic debris.

Clinical Implications20

  • The smear layer is detrimental and must be removed.

  • Reduces permeability of the dentine

  • ==It can harbor bacteria, protecting them from disinfectants.==

  • Prevents access to bacteria in the dentinal tubules by irrigants and medicaments

  • A porous and weakly adherent layer that breaks down with time

  • ==This can create a gap between the root filling and the canal wall, allowing for microleakage.==

  • Reduces adhesion of sealers to canal walls

  • ==It negatively affects the adhesion and seal of root canal sealers to the dentine wall.==

  • Can be removed by chelating agents

    • e.g. EDTAC

Combined Use of EDTA and NaOCl21

Do Not Mix

Since NaOCl removes organic debris and EDTA removes inorganic debris, they are used in combination to completely clean the canal walls. They cannot be mixed together, as they deactivate each other, and must be used sequentially.

A scanning electron microscopic evaluation of four root canal irrigation regimens

  • Baumgartner JC, Mader CL.
  • J Endod 1987; 13: 147-57.

Study Findings (Baumgartner & Mader - 1987)22

SalineNo InstrumentationSaline+ Instrumentation
NaOClNo InstrumentationNaOCl+ Instrumentation
EDTANo InstrumentationEDTA+ Instrumentation
EDTA + NaOClNo InstrumentationEDTA + NaOCl+ Instrumentation

  • Baumgartner & Mader - 1987

    • Used alternately between each file

  • Byström & Sundqvist - 1985

    • Had better anti-microbial action than when NaOCl used alone

Anti-Bacterial Efficacy2324

  • Based on: Byström & Sundqvist 1981, 1985
Irrigant% canals free of bacteria
Saline20
NaOCl50
NaOCl + EDTA70

Note

Even with the best irrigation protocol, 100% disinfection is not achieved, highlighting the need for intra-canal medicaments.

Optimal Irrigation Sequence

Info

The sequence in which the irrigants are used is critical for achieving the cleanest possible canal system.

An SEM study of the effects of different irrigation sequences and ultrasonics

  • Abbott PV, Heijkoop PS, Cardaci SC, Hume WR, Heithersay GS.
  • Int Endod J 1991; 24: 308-16.

Study Design (Abbott et al, IEJ 1991)25

  • Irrigation sequences tested:
    • EDTAC / NaOCI / EDTAC
    • NaOCI / EDTAC / NaOCI
    • Savlon (chlorhexidine / cetrimide) - control
  • Solutions Used:
    • EDTAC - 17%
    • NaOCI - 1%

Results

  • ==The sequence of EDTAC → NaOCl → final EDTAC flush produced the cleanest root canal walls, free of smear layer and smear plugs.==

  • EDTAC / NaOCI / EDTAC ↓ *** BEST

  • NaOCI / EDTAC / NaOCI *** SMEAR

  • Savlon - control *** WORST

Barriers to diffusion of Ledermix paste in radicular dentine26

  • Abbott PV, Hume WR, Heithersay GS.
  • Endod Dent Traumatol 1989; 5: 98-104.

Study Findings (Abbott et al, EDT 1989)27

  • EDTAC / NaOCl / EDTAC sequence
  • Maintained permeability of dentine
  • Increased diffusion through dentine of triamcinolone and demeclocycline from Ledermix paste
  • Solutions Used:
    • EDTAC - 17%
    • NaOCl - 1%

Summary of the EDTAC / NaOCl / EDTAC Sequence28

  • Prevents smear layer build-up

  • Using EDTAC during filing chelates the inorganic dentine debris as it is created, preventing it from being compacted into a dense smear layer.

  • Removes inorganic matter

  • Removes organic tissue

  • Removes remaining debris

    • The final NaOCl and EDTAC flushes work to remove any remaining organic and inorganic components, respectively.

  • More efficient anti-bacterial action

  • Leaves dentinal tubules open

    • Maintained dentine permeability
    • Increased access for medicaments

Anatomical Complexities29

Info

The internal anatomy of a tooth is far more complex than a simple, single cone-shaped tube. This complexity underscores why chemical disinfection is non-negotiable.

Dentinal Tubules30

Walton 1996

  • Bacteria can and do invade deep into the dentinal tubules, far beyond the reach of any mechanical instrument.
  • Effective disinfection relies on irrigants and medicaments penetrating these tubules.

Fins, Transverse Anastomoses, Lateral Canals, Accessory Canals, etc

  • The root canal system often contains intricate networks of fins, webs, loops, and multiple canals that are impossible to clean mechanically with files.
  • Files will only instrument a portion of the canal's total surface area, leaving large areas untouched.
  • ==Irrigation and medicaments are the only means of disinfecting these complex, inaccessible areas.==

Blockage and Extrusion

Proper irrigation is also critical to prevent debris from being compacted into the apical third of the canal (creating a blockage) or extruded beyond the apex (causing a periapical inflammatory reaction). Constant flushing with a file-irrigate-file-irrigate sequence is essential.

(End of Lecture Content)

Anti-Bacterial Strategies in Endodontics1

W/Prof. Paul V. Abbott AO

Methods to Reduce Endodontic Microbial Flora

  1. Identify and remove the cause
  2. Aseptic procedures
  3. Mechanical instrumentation
  4. Anti-bacterial irrigants
  5. Intracanal medicaments
  6. Interim and temporary restorations
  7. Root canal filling
  8. Coronal restoration

Mechanical Instrumentation (Filing)

How effective is it at removing bacteria on its own?

Instrumentation with endodontic files enlarges and shapes the canal, but its effectiveness at removing bacteria alone is limited.

  • Bistrom & Sundqvist (1981) Study:
    • ==This study evaluated the effect of instrumentation without irrigants or medicaments.==
    • Findings:
      • Initial bacterial counts were high (10⁴ to 10⁶ cells).
      • After one session of instrumentation, bacterial counts were reduced 100 to 1,000-fold, but a significant number of bacteria remained.
      • ==Bacterial counts increased between appointments when no medicament was used.==
      • ==After five appointments of instrumentation alone, 50% of teeth still contained cultivable bacteria.==
    • Conclusion: ==Mechanical instrumentation alone is insufficient and unpredictable for eliminating bacteria. The

Irrigation of Root Canals

Info

Irrigation is the process of flushing the root canal system with a liquid, typically using a syringe, in between each file used during instrumentation.

Purpose of Irrigation

  • Anti-microbial action
  • Dissolution of tissue and debris
    • Organic matter
    • Inorganic matter
  • Flushing action
  • Lubrication
  • Help clean areas inaccessible to files

Common Irrigants31

  1. Sodium Hypochlorite (NaOCl): The most common and effective irrigant.
  2. Ethylenediaminetetraacetic acid (EDTA): ==A chelating agent used to remove the inorganic component of the smear layer. A common formulation is EDTAC, which includes the surfactant Cetrimide.==

Footnotes

  1. Original PDF page 1: L3 Anti-bacterial Strategies - 1 - 2023, p.1 ↩ ↩2

  2. Original PDF page 2: L3 Anti-bacterial Strategies - 1 - 2023, p.2 ↩

  3. Original PDF page 3: L3 Anti-bacterial Strategies - 1 - 2023, p.3 ↩

  4. Original PDF page 4: L3 Anti-bacterial Strategies - 1 - 2023, p.4 ↩

  5. Original PDF page 5: L3 Anti-bacterial Strategies - 1 - 2023, p.5 ↩

  6. Original PDF page 6: L3 Anti-bacterial Strategies - 1 - 2023, p.6 ↩

  7. Original PDF page 7: L3 Anti-bacterial Strategies - 1 - 2023, p.7 ↩

  8. Original PDF page 8: L3 Anti-bacterial Strategies - 1 - 2023, p.8 ↩

  9. Original PDF page 9: L3 Anti-bacterial Strategies - 1 - 2023, p.9 ↩

  10. Original PDF page 10: L3 Anti-bacterial Strategies - 1 - 2023, p.10 ↩

  11. Original PDF page 11: L3 Anti-bacterial Strategies - 1 - 2023, p.11 ↩

  12. Original PDF page 12: L3 Anti-bacterial Strategies - 1 - 2023, p.12 ↩

  13. Original PDF page 13: L3 Anti-bacterial Strategies - 1 - 2023, p.13 ↩

  14. Original PDF page 27: L3 Anti-bacterial Strategies - 1 - 2023, p.27 ↩

  15. Original PDF page 28: L3 Anti-bacterial Strategies - 1 - 2023, p.28 ↩

  16. Original PDF page 29: L3 Anti-bacterial Strategies - 1 - 2023, p.29 ↩

  17. Original PDF page 30: L3 Anti-bacterial Strategies - 1 - 2023, p.30 ↩

  18. Original PDF page 31: L3 Anti-bacterial Strategies - 1 - 2023, p.31 ↩

  19. Original PDF page 32: L3 Anti-bacterial Strategies - 1 - 2023, p.32 ↩

  20. Original PDF page 33: L3 Anti-bacterial Strategies - 1 - 2023, p.33 ↩

  21. Original PDF page 34: L3 Anti-bacterial Strategies - 1 - 2023, p.34 ↩

  22. Original PDF page 35: L3 Anti-bacterial Strategies - 1 - 2023, p.35 ↩

  23. Original PDF page 36: L3 Anti-bacterial Strategies - 1 - 2023, p.36 ↩

  24. Original PDF page 37: L3 Anti-bacterial Strategies - 1 - 2023, p.37 ↩

  25. Original PDF page 38: L3 Anti-bacterial Strategies - 1 - 2023, p.38 ↩

  26. Original PDF page 39: L3 Anti-bacterial Strategies - 1 - 2023, p.39 ↩

  27. Original PDF page 40: L3 Anti-bacterial Strategies - 1 - 2023, p.40 ↩

  28. Original PDF page 41: L3 Anti-bacterial Strategies - 1 - 2023, p.41 ↩

  29. Original PDF page 42: L3 Anti-bacterial Strategies - 1 - 2023, p.42 ↩

  30. Original PDF page 43: L3 Anti-bacterial Strategies - 1 - 2023, p.43 ↩

  31. Original PDF page 45: L3 Anti-bacterial Strategies - 1 - 2023, p.45 ↩

Graph View

Backlinks