Endodontic microbiology and dressing strategy Flashcards
How are infections caused?
bacteria penetrate or infiltrate skin or mucosa
3 ways bacteria can infiltrate a tooth
- exposition of pulp via trauma or attrition
- caries
- gingivitis/periodontitis
Characteristics of bacteria in oral cavity (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
Why do bacteria produce biofilms?
protection
How does the biofilm change as it develops?
the spectrum of species changes from aerobe to anaerobe
How does cariogenic bacteria progress into dentine? (4)
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
What kind of bacteria are found in deep dentine lesions and why?
facultative and strict anaerobe species: streptococci, lactobacilli
they have passed a process of selection (the deeper, the more difficult to get nutrients and oxygen)
How do streptococci vs lactobacilli produce energy?
streptococci: mostly facultative anaerobes, some strict anaerobes
lactobacilli: facultative anerobes or microaerophillic
What is the signficance of lactobacilli if found in salivary cultures?
indicate presence of active dentine lesions
What happens when bacteria arrives in the pulp?
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
Describe the progression of pulpal inflammation. (6 steps)
- Formation of secondary dentine (prior to bacteria entering the pulp)
- Hyperaemia: blood vessels widen and fill w erythrocytes
- Acute pulpitis
- Necrobiosis: pulpal invasion (some pulp vital, some dead)
- Necrosis: complete destruction of pulpal tissue, biofilms develop in the canal walls
Describe how acute pulpitis progresses (3)
- spaces between cells are filled with serum
- then blood vessels become permeable for leukocytes
- micro-abscesses form as it nears necrosis and bacteria enters the pulp
What microroganisms/cells are present in necrobiosis
masses of invading microorganisms
inflammatory cells
What is gangrene?
means necrosis with superimposed infection but most people just call it necrosis
What types of bacteria can be seen in a pulpal biofilm? (3) How do yeasts appear under microscope? (1)
spirochettes, filaments with or without gram negative bacterial wall
yeasts are circular, appear larger than bacteria
How do bacteria in pulpal biofilms survive without nutrients from the oral cavity such as carbohydrates? (2)
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
What is internal infection? Why is this clinically signficant?
infection of tubuli from inside
we must file the canals and remove enough dentine as bacteria can exist within canal walls and in dentine
Different pathways to apical perio (flowchart)
What is apical periodontitis?
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)
How does the balance between virulence of bacteria and immune defece cause either acute or chronic apical perio? (seesaw problem)
low virulence, good defence → chronic apical periodontitis
high virulence, low defence → acute apical periodontitis/abscess
When does acute apical perio happen and what are some forms?
balance of virulence and defence in favour of attacker
primary acute apical perio, secondary acute apical perio, periapical abscess
When does chronic apical periodontitis happen? What is the result (which cells are present)?
balance of virulence and defence in favour of defence
granuloma with lymphocytes, plasma cells, monocytes and macrophages (immune cells)
When does chronic apical abscess happen?
equilibrium of virulence and defence
T/F We can identify all root canal bacterial species using cultures***
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
How many species can be identified in the initial colonisation of the pulp?
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
Which species are most common in problem cases? Why do they cause an issue?***
enterococcus faecalis
candida albicans
- resistant against CaOH2
- high penetration into tubuli
- forms biofilms
