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BDS3 Endodontics > Chemo-Mechanical disinfection > Flashcards

Chemo-Mechanical disinfection Flashcards

1
Q

What is the aetiology of endodontic disease?

A
  • Bacterial, fungal and viral origins

- The bacteria and fungi upon invading the root canal space will create inter biofilms

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2
Q

What are biofilms?

A
  • Biofilms are complex communities of bacteria and fungi that are adherent to the dentinal surface and are imbedded within a complex ECM that has been elaborated by the bacterial cells
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3
Q

What are 5 ways in which the biofilm can provide resistance for the microorganisms that reside inside the biofilm?

A
  • Antimicrobials may fail to penetrate beyond the surface layers of the biofilm
  • Antimicrobials may be trapped and destroyed by enzymes
  • Antimicrobials may not be active against non-growing micro-organisms
  • Expression of biofilm-specific resistance genes (e.g. efflux pumps)
  • Stress response to hostile environmental conditions (e.g. leading to an over expression of antimicrobial agent-destroying enzymes)
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4
Q

What are the clinical objectives of endodontic therapy? (2)

A
  • Remove canal contents

- Eliminating infection

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5
Q

Root canal complexities enhance the ability of bacteria and fungi to evade our attempts to eradicate them. Give examples of root canal complexities? (4)

A
  • Fins
  • Deltas
  • Isthmuses
  • Lateral canals
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6
Q

What is chemo-mechanical disinfection?

A
  • In this process we employ a mechanical means to debride and shape the canal
  • We supplement this with a chemical means in order to try to enhance our biofilm disruption
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7
Q

What are the design objectives for endodontics? (3)

A
  • Create a continuously tapering funnel shape
  • Maintain apical foramen in its original position
  • Keep apical opening as small as possible
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8
Q

What is the purpose of the mechanical preparation?

A
  • This creates space to allow irrigating solutions and medicaments to more effectively eliminate micro-organisms from the root canal system
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9
Q

What are the stages in mechanical preparation? (7)

A
  • Preparation of tooth
  • Access cavity preparation
  • Creating straight-line access
  • Initial negotiation
  • Coronal flaring
  • WL determination
  • Apical preparation
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10
Q

When doing our mechanical preparation of a root canal why do we start coronally and work our way apically?

A
  • In doing this we manage to eradicate the most significantly infected parts of the root canal surface - removing bacteria and fungi from biofilms coronally
  • Then we move apically where there is less infected material
  • This way we are less likely to carry infected material further into the tooth
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11
Q

What is the apical preparation size determined by?

A
  • Determined by the initial size of the root canal apex
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12
Q

What is passive exploration of the canal known as?

A
  • Known as gauging
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13
Q

What size is an apical canal preparation usually?

A
  • Usually at least ISO size 25
  • Some advocate 30 and larger to allow irrigation
  • Canal curvature impacts upon what is achievably safe
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14
Q

What are the ideal properties if an irrigant? (14)

A
  • Low cost
  • Washing action
  • Reduction of friction
  • Improving cutting of dentine by the instruments
  • Temperature control
  • Dissolution of organic and inorganic matter
  • Good penetration within the root canal system
  • Killing of planktonic microbes
  • Killing of biofilm microbes
  • Detachment of biofilm
  • Non-toxic to periapical tissue
  • Non-allergenic
  • Does not react with negative consequences with other dental materials
  • Does not weaken dentine
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15
Q

What part of sodium hypochlorite is responsible for antibacterial activity?

A
  • Hypochlorous acid
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16
Q

Why do we use sodium hypochlorite as an irrigant? (5)

A
  • Potent antimicrobial activity
  • Dissolves pulp remnants and collagen
  • Only root canal irrigant that dissolves necrotic and vital tissue
  • Helps disrupt smear layer by acting on organic component
  • Dissolves organic tissue
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17
Q

What factors are important to allow NaOCl to function in the root canal system? (5)

A
  • Concentration
  • Volume
  • Contact
  • Mechanical agitation
  • Exchange
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18
Q

What % solution of NaOCl do we use in the dental school?

A

3%

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19
Q

What is the range of % solutions of NaOCl that are used as irrigants?

A
  • Variation in suggested optimum concentration for antibacterial activity
  • Presence of organic material affects antibacterial activity
  • Used between 0.5-6% solutions
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20
Q

Why would we not use a flat cut needle to deliver irrigant?

A
  • The irrigant will be forced ahead with the needle
  • The problem with this is that straight cut needles with this force ahead of the needle we risk the potential of a hypochlorite accident
  • Do not want to squirt the hypochlorite through the constriction - risk of this is significant tissue damage
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21
Q

Why is it advantageous to use mechanical agitation to get the irrigant down to the apex?

A
  • This leads to improved irrigation, penetration and biofilm and smear layer disruption
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22
Q

What is an endoactivator?

A
  • Sonic device with fibre tips that go on
  • It vibrates
  • Don’t usually have these in the dental school so use manual dynamic irrigation
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23
Q

What is manual dynamic irrigation?

A
  • This is where we use a GP point into the canal and start to pump it in and out
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24
Q

What are the possible problems with NaOCl? (3)

A
  • Possible effect on dentine properties
  • Inability to remove smear layer itself
  • Effect on organic material
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25
Q

What is the smear layer?

A
  • The layer of organic and inorganic material that is laid down when you machine the root surface
  • When cutting dentine with the files going to create smear layer - this smear layer is going to potentially limit your disinfection in tubules and will prevent penetration of tubules so reduce the extent of sealing you achieve
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26
Q

To what depth does the smear layer penetrate dentine?

A
  • Superficial 1-5 micrometres with packing into tubules
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27
Q

What are 2 negatives about the smear layer in a root canal?

A
  • Bacterial contamination, substrate and interferes with disinfection
  • Prevents sealer penetration
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28
Q

What materials might we use to remove the smear layer in endodontics? (4)

A
  • 17% EDTA
  • 10% Citric acid
  • MTAD (mixture of a tetracycline isomer, an acid and a detergent)
  • Also use sonic and ultrasonic irrigation - can activate it by using these or by using manual dynamic irrigation
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29
Q

What is EDTA short for?

A
  • Ethylenediaminetetraacetic acid
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30
Q

What is EDTA and what is it capable of doing when used with NaOCl?

A
  • EDTA is a chelating agent that is capable, when used with NaOCl, of removing the smear layer
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31
Q

What % solution of EDTA is used to remove the smear layer?

A
  • 17% solution
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32
Q

How long is the contact time necessary for a 17% solution of EDTA to remove the smear layer?

A
  • 1 minute contact time necessary
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33
Q

When EDTA removes the smear layer what does it do to dentine?

A
  • Opens up the tubules and allows to penetrate the tubules
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34
Q

If hypochlorite and EDTA react it will affect their efficacy. How can we avoid this?

A
  • Should withdraw or aspirate one irrigant, ideally dry, place next irrigant, have it active, withdraw and aspirate then dry then go back to irrigants
35
Q

Why might dentine be put at risk when using both EDTA and NaOCl in the root canal?

A
  • The dentine is made more susceptible to the hypochlorite action because EDTA is chelating agent and that will capture the inorganic component of the dentine
  • Will expose collagen within the dentine and that can be acted upon by the hypochlorite

So need to get balance right to not put dentine at risk

36
Q

What are possible complications of NaOCl? (4)

A
  • Discoloration of fabrics
  • Ophthalmic injuries due to eye contact
  • Apical extrusion leading to tissue necrosis - intracanal use, no more toxic than saline solution
  • Allergic reactions
37
Q

Why must we wear eye protection when using NaOCl?

A
  • As if splash into eyes can cause blindness
38
Q

Does chlorhexidine digluconate have antibacterial activity?

A
  • Yes
39
Q

Does Chlorhexidine digluconate have antifungal activity?

A
  • Yes, but less than NaOCl
40
Q

Is Chlorhexidine Digluconate active against biofilms?

A
  • Somewhat active against biofilms, but unable to disrupt biofilms
  • (NaOCl is able to disrupt biofilms so makes chlorhexidine a poorer choice as an irrigant)
41
Q

Absorption of Chlorhexidine Digluconate prevents microbial colonisation for time beyond the time of application. How long can it do this?

A
  • Varying times - up to 12 weeks
42
Q

Is chlorhexidine digluconate biocompatible?

A
  • Yes biocompatibility considered acceptable
43
Q

Is sensitivity to CHX possible?

A
  • Yes

- Risk of anaphylactic reaction

44
Q

What does CHX interacting with NaOCl form? (3)

A
  • Para-chloroaniline
  • Cytotoxic and carcinogenic
  • Uncertain bioavailability
45
Q

In the dental school: once canal preparation is complete the canal should be finally irrigated with…? (4)

A
  • 3% NaOCl throughout instrumentation and at least 30ml after instrumentation complete with manual dynamic irrigation - at least 10 mins prior to obturation
  • 17% EDTA 1min penultimate rinse
  • 3% NaOCl final rinse
  • Dry canal using absorbent paper points between irrigants
46
Q

What should you dry the canal with between irrigants?

A
  • Using absorbent paper points
47
Q

What are common symptoms of NaOCl extrusion? (6)

A
  • Pain
  • Swelling
  • Ecchymosis
  • Haemorrhage
  • Neurological complications
  • Airway obstruction
48
Q

What is ecchymosis?

A
  • Type of bruise
49
Q

Where does ecchymosis in a classic NaOCl accident manifest?

A
  • Along the course of superficial venous vasculature

- Rare despite millions of RCT’s performed annually

50
Q

What are the risk factors that could cause a hypochlorite accident? (6)

A
  • Excessive pressure during irrigation
  • Needle locked within canal
  • Loss of control of working length
  • Larger apical diameters/constriction (root resorption/immature teeth/developmental abnormalities)
  • Anatomical factors/proximity to sinus
  • Higher NaOCl concentration?
51
Q

Explain why pressure is the main factor in causing a hypochlorite accident?

A
  • If hypochlorite is pushed beyond the patent apical foramen under pressure, if the pressure is significant to cause hypochlorite to cross the vascular wall and enter the blood supply that is where the significant problems occur
  • Pressure generated by positive- pressure irrigation delivery systems at the periapex have to exceed the venous pressure in the superficial veins of the neck
52
Q

What flow rate much you NEVER exceed when delivering NaOCl into the root canal to avoid a hypochlorite accident?

A
  • 1ml/15 seconds
53
Q

Explain the steps to manage NaOCl extrusion into the tissues? (8)

A
  • ALL treatment must STOP
  • Keep calm and try not to alarm your patient
  • Advise the patient of what has happened and reassure them regarding the immediate management
  • Where pain is present consider administration of LA via a block of the affected region
  • If profuse bleeding through the root canal is occurring, allow this to continue until haemostasis is observed
  • A steroid-containing intracanal medicament (e.g. Odontopaste) should be placed in the root canal, ensuring no pressure is used during application
  • Do not obturate the tooth at this visit, but seal to coronal access cavity
  • Priority must be given to pain relief, reduction of the swelling, and prevention of secondary infection
54
Q

In order to manage NaOCl extrusion into the tissues, priority must be given to pain relief, reduction of the swelling, and prevention of secondary infection. How might we do this? (6)

A
  • Cold compress during the first few days
  • Warm compresses for resolution of the soft tissue swelling and elimination of the haematoma
  • Analgesics (ibuprofen 400-600mg QDS/ paracetamol 1000mg QDS)
  • Review within 24hrs
  • Prescription of antibiotics (case specific)
  • Refer if severe and appears that patient’s condition is deteriorating
55
Q

What are the guidelines for the use of NaOCl in order to prevent a hypochlorite accident? (1-4 of 17)

A
  1. Careful pre-operative radiographic assessment is essential - be vigilant of open apices and perforations and discuss with senior staff if either is suspected prior to commencing treatment
  2. It is important that the pre-endodontic restorative state of the tooth is assessed. a pre-endodontic build-up is necessary if isolation is likely to be compromised
  3. Ensure the patient is provided with a disposable bib to protect clothing. This must adequately cover clothing. If necessary use 2 bibs overlapping
  4. Provide patient with protective eyewear
56
Q

What are the guidelines for the use of NaOCl in order to prevent a hypochlorite accident? (5-8 of 17)

A
  1. Always use dental dam to isolate the tooth requiring RCT and ensure this is sealed well with OrasealTM. The oral seal should be ‘moulded’ to the tooth contours with a damp cotton wool pledget. Placing the clamp prior to dam placement can facilitate visualisation. Ensure floss is used to secure the clamp during placement and removed after dam is seated
  2. Test the dental dam seal by irrigating with chlorhexidine first to ensure no leakage
  3. Dam placement must be checked by the supervising clinician
  4. Ensure that all syringes are clearly labelled with adhesive labels (must be leur lock syringes)
57
Q

What are the guidelines for the use of NaOCl in order to prevent a hypochlorite accident? (9-14 of 17)

A
  1. Always use a side-vented needle for irrigation of the root canal
  2. Always use a leur-lock 27G needle and ensure this is securely attached to a 3mm syringe - test this before use
  3. Fill syringe less - approx. 3/4’s full to aid control
  4. Always use a silicone stop in the needle and set to 2mm short of working length
  5. Always pass the endodontic syringe behind the patient’s head and never over the patient’s face
  6. The irrigating needle should not bind in the root canal at any time
58
Q

What are the guidelines for the use of NaOCl in order to prevent a hypochlorite accident? (15-17 of 17)

A
  1. Whilst irrigating, depress the plunger with index finger rather than thumb to reduce the pressure
  2. Report any irrigation/endodontic incident to senior staff immediately
  3. If you have any concerns about the clinical handling of the sodium hypochlorite by the operator, then you should raise your concerns with the individual or a senior member of NHS/university staff if necessary
59
Q

What are intra-canal medicaments?

A
  • Materials placed inside the root canal between treatment appointments in an attempt to destroy microorganisms and prevent re-infection (can also help to disrupt any connective tissue that is left in the canal)
60
Q

What are the ideal properties of an intra-canal medicament? (4)

A
  • Attempt to destroy microorganisms and prevent re-infection
  • Reduce and prevent multiplication of any bacteria that do remain
  • Reduce inflammation and exudate
  • Control of root resorption
61
Q

What is Exudate?

A
  • A mass of cells and fluid that has seeped out of blood vessels or an organ, especially in inflammation.
62
Q

What does an anti-microbial paste contain? (2)

A
  • Corticosteroid

- Tetracycline (antibiotic)

63
Q

What are anti-microbial pastes used to manage?

A
  • Used to manage ‘hot pulps’
64
Q

What is a ‘hot pulp’?

A
  • The pulp status whereby LA although delivered appropriately does not lead to management of discomfort during instrumentation
65
Q

Why would we use an antimicrobial paste in the management of a ‘hot pulp’?

A
  • By applying the paste we may get a reduction in pulpal inflammation which may allow a subsequent instrumentation at a following visit (so can facilitate follow up treatment)
  • Have limited effectiveness so should only be in for a short period of time
66
Q

Anti-microbial pastes have a limited effectiveness so should only be in for a short period of time. How long are they effective for?

A
  • effective for 5-7 days
67
Q

What is the pH of non-setting calcium hydroxide?

A

12.5

68
Q

Which material is considered the gold standard for a dressing material?

A
  • Calcium hydroxide
69
Q

What does the high pH of calcium hydroxide contribute to?

A
  • Contributes to antibacterial activity
  • Numerous studies demonstrate bacterial reduction after inter-appointment dressing
  • Prolonged antibacterial activity
70
Q

What does the hydrolysis of lipopolysaccharides by calcium hydroxide do?

A
  • Reduces its inflammatory potential in an endo infection
71
Q

Is non-setting calcium hydroxide effective in removing tissue debris?

A
  • Yes
72
Q

How long should the treatment of non-setting calcium hydroxide be?

A
  • Treatment for 7 days
73
Q

What does the combination of non-setting calcium hydroxide and NaOCl do?

A
  • Improved cleaning ability
74
Q

When a canal is undergoing inter-appointment disinfection the canal should be completely filled with calcium hydroxide paste. Why is this and how is it inserted into the canal?

A
  • Must come into direct contact with bacterial cell wall to be effective
  • Placed by injection through a small disposable syringe tip (Ulracal, Optident)
75
Q

When should inter-appointment disinfection occur?

A
  • Once the cleaning and shaping of the canal has occurred
76
Q

When injecting inter-appointment medicaments we need to be careful not to extrude materials. Why is this important?

A
  • As the medicament (calcium hydroxide) has such a high pH so can be an irritant to the peri-radicular tissues and if it interacts with vital structures can lead to significant effects such as anaesthesia or paraesthesia
77
Q

When we inject the non-setting calcium hydroxide into the root canal system we want to get as complete a filling or passage as possible into all of the intricacies of the root canal system as there can be complex systems. How might we do this?

A
  • Can try to encourage this using a small file to agitate the calcium hydroxide or can use an endo activator
78
Q

What is the purpose of inter-appointment temporary dressings?

A
  • Must effectively seal the root canal from contamination between visits
79
Q

Give 3 examples of inter-appointment temporary dressings?

A
  • Cavit
  • IRM
  • Glass ionomer cements
80
Q

What happens if we fail to place an appropriate inter-appointment temporary dressing?

A
  • IF fail to do this there is a significant risk that bacteria may enter the root canal system via the oral cavity again and therefore all efforts for disinfection would be lost so need to make sure seal is sound
81
Q

What can failure of a temporary restoration be due to? (3)

A
  • Inadequate thickness of material
  • Improper placement of the material
  • Failure to evaluate the occlusion after placement
82
Q

A small layer of Coltosol may be placed in the root canal space prior to an inter-appointment temporary dressing. What is Coltosol?

A
  • This is a provisional restorative material that is bright white material, it does set hard but is not generally considered hard enough to display longevity that would allow it to sit in the oral cavity or directly in contact with saliva
  • So Coltosol can be used as an intermediate layer or base on top of the cotton wool that is placed within the canal
83
Q

Why is Coltosol sometimes used in a root canal as an intermediate layer prior to a inter-appointment temporary dressing?

A
  • The reason it is used is because it is bright white and is very readily visualised and can be removed using the ultrasonic
  • So it can prevent the need to cut through a very thick layer of GIC, and so means we are less likely to create additional tooth structure loss whilst regaining access
84
Q

How thick do we want the GIC placed in the canal to be to prevent displacement and leakage?

A

3mm

BDS3 Endodontics (8 decks)

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