Y3 L5 Root canal cleaning Flashcards
What does root canal cleaning refer to?
Using a variety of techniques, medicaments and irrigants to ideally remove all inorganic debris, organic substrate and micro-organisms.
What are the aims of cleaning?
- To prevent the tooth from being a source of micro-organisms i.e. eliminating infection.
- Vital cases = asepsis. Preventing infection usually in the treatment of irreversible pulpitis.
- Non vital cases = antisepsis. Treating infection i.e. apical periodontitis.
Describe the principle of asepsis in vital pulp therapy.
- Sterile working environment
- Rubber dam
- Coronal disinfection
- Sterile instruments
- Stable, well-sealed, temporary restoration
- High quality permanent coronal restoration
NB: these apply to non-vital cases as well.
Describe the principle of antisepsis in non-vital endodontics.
- Removal of the inner portion of the canal wall where dentinal tubules are most heavily infected- mechanical means
- Removal of as many micro-organisms as possible from the canal system, including isthmuses, crevices and lateral areas of oval canals- chemical irrigants required
- Remove sources of substrate for bacterial growth, internal sources- necrotic pulp tissues, external sources- quality of restorative seal
What are the methods of bacterial reduction?
- Instrumentation
- Irrigation
- Antimicrobial medication
- Sealers
- Other e.g. lasers, photo-activated disinfection, high frequency electrical pulses, ozone
What are the 2 components of root canal cleaning?
- Removal of bacteria
- Management of the smear layer
What cleaning materials are used in the UDH?
- Sodium hypochlorite 2% (NaOCl)
- EDTA 17%
- Chelating agents (e.g. Glyde)
- Saline
- Endodontic chlorhexidine
What are the features of an ideal irrigant?
- Has a broad antibacterial spectrum
- Efficacious against anaerobic and facultative microorganisms
- Dissolves and digests necrotic tissue
- Prevents formation of smear layer or dissolves it
- Inactivates endotoxins
- Non-toxic systemically
- Non-caustic to local tissues
Describe sodium hypochlorite 2%.
- Gold standard for disinfecting
- Has a broad antibacterial spectrum
- Dissolves and digests endodontic micro-organisms and necrotic tissue
- Removes organic components from the smear layer
- Inactivates endotoxins
- At low concentrations it is minimally irritating
- Must replenish regularly constantly dripping into canal as it will become inactivated if just left there. Reduced effectiveness.
How long should NaOCl be used for?
Between 20 minutes and 2 hours
Does temperature affect NaOCl efficacy?
No.
Agitation has a greater effect than increasing temperature.
Does increasing concentration affect NaOCl efficacy?
- Antibacterial efficacy of sodium hypochlorite remains unchanged regardless of its concentration
- Higher concentration increases risk of tissue damage to the patient if apical extrusion occurs
How do you prevent a hypochlorite accident?
- Must keep irrigant needle 3-4mm from the apex
- Use side vented needle
- Must set rubber stopper on needle
- Keep syringe moving
- Gentrle drips
- Maximum 2% NaOCl
What should you do if a hypochlorite accident occurs?
What is the smear layer?
A powdery, loose adherent layer, typically 1-2um thick on the surface of the canal wall.
- After mechanical instrumentation, this smear layer is left behind.
- It is composed of bacteria, necrotic debris, particulate dentine debris, pulpal remnants.
- Occludes dentinal tubules.
What are the issues of leaving the smear layer behind?
- It harbours microorganisms and can act as substrate for microbial proliferation
- Creates an avenue for leakage
- Interferes with the physical properties and adaptation of root canal sealer material
What chemical is used to remove the smear layer?
17% EDTA
- Ethylenediamine tetraacetic acid
- Solution used after NaOCl has been used
- Sometimes citric acid is used as an alternative
What are chelating agents?
- E.g. Glyde
- Used to dissolve calcium from the dentine
- Facilitates instrumentation, aids removal of smear layer, reduces hardness of dentine, prevents soft tissue clumping
- Glyde acts as a lubricant to fit files into canals, only at the very beginning
Why should paste chelating agents not be used during canal preparation?
- They increase stress on rotary instruments
- Are inefficient in preventing smear layer
-Interfere with NaOCl by reducing available chlorine rendering it ineffective
Therefore, Glyde is only used at the very beginning when we are trying to introduce our files.
Describe endodontic chlorhexidine (2%).
Chlorhexidine digluconate has excellent antimicrobial properties but cannot be advocated as the main irrigant in standard cases.
- Has the property of substantivity (binds to dentine surface)
- Does not dissolve necrotic tissues
- Is less effective against gram -ve microorganisms
- It is more effective against +ve microorganisms, therefore more useful in retreatment cases
- Reacts with NaOCl to form a thick brown/red precipitate (messy)
- In the root canal it should only be used at 2% not 0.2% (mouthwash)
Outline the standard irrigation regimen in RCT.
Why should we agitate the irrigant?
- Constant moving of the irrigant and replenishing means irrigant can reach isthmuses
- Uninstrumented recesses may be left in many oval canals after preparation, and these recesses may often not be completely obturated
- Special ultrasonic agitation tips are available to overcome this issue
What factors make cleaning more effective/easier?
- Larger canals
- Enhanced taper
- Using an endodontic ultrasonic
- Using NaOCl and EDTA/citric acid
What is enterococcus faecalis?
A gram positive bacteria with a pathigenic role in treatment failure.
Resistant to CaOH dressing (temp dressing between appointments), but can be killed by Chx 2%. Or can use iodine potassium iodide (IDK) for 5-10 mins, beware of iodine allergy.
Associated with:
- Well filled, but failed, endodontic treatment
- Treatment that spans many appointments
- Canals that have been left open
- Canals that have suffered coronal leakage
Why are inter-appointment dressings needed?
To suppress bacteria regrowth and prevent further bacterial and substrate ingress between treatment vists if treatment lasts more than 1 visit (most cases).
What inter-appointment dressing is used most commonly?
Calcium hydroxide (CaOH2)
- Very high pH so suppresses bacterial growth
- Hydroxyl ions are antibacterial via protein and DNA destruction
- Some species are resistant e.g. E. Faecalis
- Inactivated by hydroxyapatite
- Only effective for 7 days
- Not perfect, but don’t have any other option
Describe the technique for placing a temporary CaOH2 dressing.
- CaOH mixed with water or available as a pre-mixed aqueous solution (e.g. Hypocal)
- Syringe in or use paper points to place into canals
- Cotton pledget to seperate CaOH2 from temporary dressing
- GIC or PolyF used for temp dressing (good seal)
