MS2 - Endodontic Microbiology

Question 1

Are endodontic infections strictly associated with just bacteria?

Answer 1

Bacteria remain the major cause, but other microorganisms have been associated, such a fungi and viruses

Question 2

Comment on the state of the dentine-pulp complex before and after being exposed to the oral cavity

Answer 2

the dentine-pulp complex is normally sterile and isolated from the oral microbiota, but if these protective layers are lost, the pulp will be exposed to the oral microbiota

Question 3

Does dentinal exposure of bacteria (dentinal caries) represent a significant route of pulp infection?

Answer 3

as long as the pulp is vital, dentinal exposure does not represent a significant route of pulp infection. except when dentine thickness is considerably reduced and dentine permeability is significantly increased

Question 4

in what way does the dentine permeability increase?

Answer 4

dentine tubules travel the entire width of dentine and have a conical formation

• smallest diameter near the enamel or cementum (0.9um)
  
  • Largest diameter near the pulp (2.5um)

Question 5

Does bacterial invasion through dentinal tubules occur more rapidly in a tooth a vital or non-vital pulp?

Answer 5

non-vital pulp

Question 6

how does the vitality of the pulp affect the rate of caries progression through dentine?

Answer 6

if the vitality of the pulp is compromised, and the defence mechanisms are impaired, even a small number of bacteria may initiate pulpal infection

Question 7

What are some causes of root canal exposure and/or infection? (4)

Answer 7

• caries (most common)
• dental trauma
• direct pulp exposure
• bacteria associated with perio propagating through dentinal tubules or apical/lateral ramifications

Question 8

Can periodontal disease lead to an endodontic infection?

Answer 8

Yes

Microorganisms associated with perio can reach the pulp through dentinal tubules or through apical / lateral ramifications

Question 9

(extra)

What is a Ramification in endodontics?

Answer 9

potential pathway through which bacteria can travel from a necrotic root canal to the PDL and cause disease and vice versa (from PDL to pulp - eg periodontitis)

Question 10

Can rapid pulpal necrosis occur as a result of periodontal disease?

Answer 10

Only if the periodontal pocket reaches the apical foramen → due to irreversible damage to the main blood vessels that penetrate the apical foramen

Question 11

What is that main goal of endodontic treatment that will get the best long-term success

Answer 11

Microbial reduction → eradicate bacteria colonisation or reduce the bacterial load to levels that permit periradicular tissue healing

** Bacteria have to reach a quorum of cells sufficient to cause disease (bacterial load) → before that threshold is reached, no signs and symptoms will be present

Question 12

Approximately how much of a root canal is untouched after completing instrumentation?

Answer 12

A study found that around 60-80% of the total root canal length remained untouched by instrumentation → irrigation is very important

Question 13

*What is the microbiological rationale of reinfection after endodontic treatment?

Answer 13

* Bacteria have to reach a quorum of cells sufficient to cause disease (bacterial load) → before that threshold is reached, no signs and symptoms will be present

• if the threshold is exceeded, infectious disease is established (apical periodontitis)
• if the treatment does not succeed in reducing bacteria levels below the threshold, the disease will persist
• Successful treatment is not to sterilise the root canal, but to reduce the bacterial populations to subcritical levels compatible with healing

Question 14

In term of the microbiology in a root canal system, what deems a treatment successful?

Answer 14

Not necessarily making the root canal sterile, but reducing the bacterial populations to subcritical levels compatible with healing

Question 15

What does the (fake) equation P=N.V.I. / R stand for

+which of these factors can we change?

Answer 15

Pathogenicity = Number of bacteria x Virulence x Interactions / Resistance

• the only factor that we can influence is number of bacteria

Question 16

Are gram positive or gram negative bacteria more prone to resistance during RCT and what in an example of the bacteria?

Answer 16

Gram positive

E. faecalis

(can persist after rct and dressing)

Question 17

Which type of bacteria is more prone to resistance during RCT, and what is an example of this type of bacteria?

Answer 17

Gram Positive bacteria

E. faecalis

Question 18

What are the 4 basic dynamics of of pulp response from caries exposure?

Answer 18

Question 19

How deep does bacteria travel before the. pulp responds?

Answer 19

the pulp responds by inflammation long before the bacterial products reach the pulp

Question 20

Can you predict the time it will take a pulp exposed to bacteria to become necrotic?

Answer 20

No, its unpredictable

Question 21

From the histological point-of-view, what represents the transition from reversible pulpitis to irreversible pulpitis?

Answer 21

The occurrence of focal necrosis (although of limited extension) associated with bacterial colonisation

i.e. small amt of necrosis

Question 22

No matter what the route of bacterial access to the root canal is, what is a pre-requisite for estabilishing primary endodontic infections

Answer 22

necrosis of pulp tissue

Question 23

T/F Occurence of apical perio is only dependent on how virulent the bacteria is

Answer 23

F, multifactorial disease that is a result of the interplay of many host and bacterial factors

Question 24

(Extra)

Can you have periapical inbfection/inflammation without an infection in the pulp?

Answer 24

no

Question 25

What is the possible cause of this lesion?

Answer 25

no caries or occlusal fracture / pulp exposure

trauma or perio causing bacterial invasion though lateral canals/dentinal tubules, causing pulp necrosis leading to apical periodontitis

(this case was trauma)

Question 26

What may be the cause of these lesions?

Answer 26

large restorations and caries near the pulp - likely pulp necrosis due to the sequelae of bacterial pulp exposure leading to apical periodontitis

Question 27

T/F Bacteria exists in periradicular bone (where you see PA RL) with apical perio

Answer 27

F, bacteria is inside the canals, apical perio is inflammation consequent to infection

also in abscess if it was there

Question 28

Explain the spatial distribution of endodontic microbiota

Answer 28

• planktonic bacterial cells: suspended in fluid and enmeshed in necrotic pulp tissue in the main root canal → just irrigation can remove
• biofilms, only 5-10% of the bacteria (but the problem): sessile, multicellular microbial community (of microcolonies) enmeshed in self-produced matrix of extracellular polymeric substance (EPS - 85% of volume of biofilm), mostly comprised of polysaccharides but also proteins and nucelic acids → matrix protects bacteria. Biofilms can be:

1. intracanal/radicular: only way to remove is through files
2. extra-radicular

Question 29

What are Planktonic bacterial cells (in brief) and how can these be removed from the root canal?

Answer 29

bacteria suspended in a fluid phase and enmeshed in necrotic pulp tissue

can be removed with irrigation

Question 30

Why are biofilms difficult to treat and how should they be removed from the root canal?

Answer 30

They are cells that are enmeshed in a self-produced matrix of extracellular polymeric substance (EPS)

require mechanical and chemical disruption of the biofilm - filing and irrigation

Question 31

how can endodontic infections be classified according to their anatomic location?

Answer 31

1. Intraradicular infection
2. Extraradicular infection

Question 32

what is an intraradicular infection?

Answer 32

Infection caused by microorganisms colonising the root canal system

Question 33

*What are the 3 categories of intraradicular infections and how are they categorised in this way?

Answer 33

categorised according to the time the microorganisms entered the root canal system

1. Primary infection - caused by microorganisms that initially invade and colonise the necrotic pulp tissue (through dentine tubules, ramifications, exposed pulp etc)
2. Secondary Infection - caused by microorganisms not present in the primary infection, but i_ntroduced in the root canal_ system some time after intervention (eg. leakage in temporary resto b/w appts, touching the files/gutta percha w gloved fingers)
3. Persistent Infection - Caused by microorganisms that were members of the primary and secondary infection and r_esisted intracanal antimicrobia_l procedures and were able to endure periods of nutrient deprivation in treated canals (e.g. E. faecalis)

Question 34

What is shown in these 2 examples?

Answer 34

e. g 1) persistent intraradicular infection - had apical perio, good tx provided, but no healing due to persistent bacteria
e. g. 2) persistent infection and late failure - bacterial load was reduced and good bone healing occured but bacteria remained (good short term success)

Question 35

What is shown here?

Answer 35

primary Intraradicular infection

Question 36

What is shown here?

Answer 36

Secondary intraradicular infection

Question 37

How does the size of a periapical lesion relate to the diversity and bacterial load in the canal in primary intraadicular infection?

Answer 37

the larger the lesion, the greater diversity and density of bacteria in the canal

(directly proportional)

Question 38

What type of bacteria are most prevalent in primary intraradicular infections?

Answer 38

Mixed community dominated by anaerobic bacteria, with diverse range of gram +ve and -ve

Question 39

What bacteria are most commonly responsible for secondary or persistent intraradicular infections and why can they cause issues and which characteristics allow this?

Answer 39

Gram positive bacteria

Bacteria that resist intracanal procedures and are present at the time of obturation can influence the outcome of the endodontic tx - are a major cause of post-tx apical periodontitis

character: can be more resistant to antimicrobial treatment measures and have ability to adapt to harsh environmental conditions in instrumented and medicated root canals

(exceptions include some anaerobic rods - F.nucleatum, Prevotella)

Question 40

When may effective complete chemo-mechanical preparation (CMP) be ineffective immediately post-op?

Answer 40

when there is extraradicular infection

Question 41

What causes apical perio lesions vs extraradicular infection (e.g. most common - acute apical abscess)?

Answer 41

apical perio - formed in response to intraradicular infection and constitute an effective barrier (by immune system) against the spread of infection to alveolar bone and other body sites (bacteria NOT in apical perio lesion)

extraradicular infection - in specific circumstances, bacteria can overcome this defence barrier and establish extra-radicular infection

Question 42

What is the most common form of extraradicular infection?

Answer 42

acute apical abscess

Question 43

What are the forms of extraradicular infection that are dependant on intraradicular infection?

Answer 43

• acute apical abscess
• chronic apical abscess
• “wet canals” (persistent exudation)

Question 44

What are the features of an extraradicular infection that is independent of the intraradicular infection and how can they be treated?

Answer 44

-Bacteria are outside the canal and are no longer fostered by the intraradicular infection

→ can persist even after the successful eradication of the intraradicular infection

• the bacteria travel through the dentine / cementum and establish themselves on the outer surface of the root (i.e. there is extra-radicular biofilm)
• the only treatment when this happens in apical surgery

Question 45

What technology is available to perform a RCT

Answer 45

• EAL
• microscope
• thermoplastic obturation
• CBCT guided endodontics
• digital x-ray
• Sonendo (modern irrigation machine)

Question 46

In irreversible pulpitis, where in the pulp is the majority of bacteria located? What about necrotic pulp? How does this effect how long the RCT takes?

Answer 46

irreversible pulpitis - pulp chamber or coronal-middle ⅓ of the root → can do single session

necrotic pulp - whole pulp infected

Question 47

How will you know if extra-radicular infection is present?

Answer 47

if apical perio persists after thorough tx (i.e. when you know intra-rad infection is resolved)