Endodontic microbiology and dressing strategy

Question 1

How are infections caused?

Answer 1

bacteria penetrate or infiltrate skin or mucosa

Question 2

3 ways bacteria can infiltrate a tooth

Answer 2

1. exposition of pulp via trauma or attrition
2. caries
3. gingivitis/periodontitis

Question 3

Characteristics of bacteria in oral cavity (3)

Answer 3

• highly variable mixture of facultative anaerobe and true anaerobe species
• either gram + or -
• in special biotopes, a well organised commensal spectrum of bacteria will develop

Question 4

Why do bacteria produce biofilms?

Answer 4

protection

Question 5

How does the biofilm change as it develops?

Answer 5

the spectrum of species changes from aerobe to anaerobe

Question 6

How does cariogenic bacteria progress into dentine? (4)

Answer 6

using dentinal tubules for invasion

dentinal tubules (1-2um) 
bacteria (0.1um) 

5-20 bacteria can fit in a tubule

propagation happens by adhesion and multiplication

Question 7

What kind of bacteria are found in deep dentine lesions and why?

Answer 7

facultative and strict anaerobe species: streptococci, lactobacilli

they have passed a process of selection (the deeper, the more difficult to get nutrients and oxygen)

Question 8

How do streptococci vs lactobacilli produce energy?

Answer 8

streptococci: mostly facultative anaerobes, some strict anaerobes
lactobacilli: facultative anerobes or microaerophillic

Question 9

What is the signficance of lactobacilli if found in salivary cultures?

Answer 9

indicate presence of active dentine lesions

Question 10

What happens when bacteria arrives in the pulp?

Answer 10

face a functioning system of defence, so a more or less balances state between attack and defence will be created

mechanism responsible for that is -> inflammation

Question 11

Describe the progression of pulpal inflammation. (6 steps)

Answer 11

1. Formation of secondary dentine (prior to bacteria entering the pulp)
2. Hyperaemia: blood vessels widen and fill w erythrocytes
3. Acute pulpitis
4. Necrobiosis: pulpal invasion (some pulp vital, some dead)
5. Necrosis: complete destruction of pulpal tissue, biofilms develop in the canal walls

Question 12

Describe how acute pulpitis progresses (3)

Answer 12

1. spaces between cells are filled with serum
2. then blood vessels become permeable for leukocytes
3. micro-abscesses form as it nears necrosis and bacteria enters the pulp

Question 13

What microroganisms/cells are present in necrobiosis

Answer 13

masses of invading microorganisms

inflammatory cells

Question 14

What is gangrene?

Answer 14

means necrosis with superimposed infection but most people just call it necrosis

Question 15

What types of bacteria can be seen in a pulpal biofilm? (3) How do yeasts appear under microscope? (1)

Answer 15

spirochettes, filaments with or without gram negative bacterial wall

yeasts are circular, appear larger than bacteria

Question 16

How do bacteria in pulpal biofilms survive without nutrients from the oral cavity such as carbohydrates? (2)

Answer 16

commensal symbiosis created by interspecies ecology of biofilms

species feed on metabolic products of other species, creating a network of interactions → helping them survive dire conditions of the pulp and host defences

Question 17

What is internal infection? Why is this clinically signficant?

Answer 17

infection of tubuli from inside

we must file the canals and remove enough dentine as bacteria can exist within canal walls and in dentine

Question 18

Different pathways to apical perio (flowchart)

Answer 18

Question 19

What is apical periodontitis?

Answer 19

After invading the whole pulp, bacteria meet a second line of defence at the apical foramen → triggers inflammation in PA tissues

(now faces full power of human’s immune defence)

Question 20

How does the balance between virulence of bacteria and immune defece cause either acute or chronic apical perio? (seesaw problem)

Answer 20

low virulence, good defence → chronic apical periodontitis

high virulence, low defence → acute apical periodontitis/abscess

Question 21

When does acute apical perio happen and what are some forms?

Answer 21

balance of virulence and defence in favour of attacker

primary acute apical perio, secondary acute apical perio, periapical abscess

Question 22

When does chronic apical periodontitis happen? What is the result (which cells are present)?

Answer 22

balance of virulence and defence in favour of defence

granuloma with lymphocytes, plasma cells, monocytes and macrophages (immune cells)

Question 23

When does chronic apical abscess happen?

Answer 23

equilibrium of virulence and defence

Question 24

T/F We can identify all root canal bacterial species using cultures***

Answer 24

No, only 10% can be cultured with conventional bacteriological methods

there is HIGH VARIABILITY in the species present in a sample and therefore you cannot determine the exact spectrum of bacteria causing endo disease

nowadays we use molecular biology and genetic screening

Question 25

How many species can be identified in the initial colonisation of the pulp?

Answer 25

mixed flora of only a few species (2-8) can be identified, mostly streptococci and obligate anaerobes

CANNOT only be only one as they need commensal symbiosis

Question 26

Which species are most common in problem cases? Why do they cause an issue?***

Answer 26

enterococcus faecalis

candida albicans

1. resistant against CaOH2
2. high penetration into tubuli
3. forms biofilms