8. Microbiology of Endodontic Infections Flashcards
• Experiments that set the role of organisms in endo disease
• Took rats > conventional/healthy rats, and also rats that were germ-free (sterile environment, have a defined flora > not as extensive as that in the conv rat)
○ Exposed pulp in both rats
○ In healthy rats > pulp necrosis > apical perio lesions
○ In germ free rats > up to 100 days after exposure > pulp remained ____ (living, blood supply, actively alive)
§ Extended period > no disease in the germ free > tissue ____
• L: germ-free pulp
○ Dentin bridge, and the stained material is the pulp (below)
§ Stained: cells, pulpal contents, no real bacteria
• R: conventional rats
○ Extensive bacterial contamination > infection > abscess formation
• Provided proof that ____ are involved in order to see inflam and disease
vital
repair
bacteria
• Group led by Moller
• Took monkey teeth > devitalized the pulps (what you do in a RC > drill through tooth and remove the pulp) > artificially infected w organisms or not infected
○ Group used a mixeture of bacteria
○ Where devitalized pulp was > organisms infecting > tissue pathology > disease was noted
○ In case where pulps were not ifnected > periradicular tissues remained ____
• Proof that ____ were importantt for at least th einitaiation and maybe the full development of disease
normal
organisms
• Done by Sundqvist
• Took teeth w pulps that were necrotic but due to trauma
○ Pulps became necrotic, and he sampled the bacteria from the teeth (using end paper points to collect) > xferred to culture medium > bacteria that were dispersed by sonication > important bc they are in biofilms, so they ____ them up > isolate colonies following culturing (in anaerobic and aerobic conditions)
• Spread the samples on various selective/differential media > isolate single colonies
○ Koch’s postulates - identify microorgs assoc w dx > purify them out
• 90% of samples contained ____ bacteria
○ Found only in RC of teeth w apical perio, and the necrotic pulp tissue did not show evidence of dx
○ Some ended up being infected, and some not
§ Those that were infected > contained bacteria (mostly anaerobes)
• Showed that anaerobic bacteria were important in the dx
break
anaerobic
Entry of Microorganisms
caries
damage as a result of ____
activity
iatrogenic restorative procedures
damage as a result of ____ treatment
traumatic occlusion
damage as a result of ____ forces on the tooth
bacterial
dental
physical
Consequences of Microbial Entry
• Time elapsed between pulp exposure and infection of the entire canal is ____ but is usually a ____ process.
infection
• Colonization of the root canal system allows bacteria to come in contact with the periradicular tissues typically via ____ or root perforations.
unpredictable
slow
apical/lateral foramina
Consequences of Microbial Entry
1.____ conditions in
different areas of the root canal
- ____ of oxygen tension and nutrients (type and availability) is formed
- ____ residing in different parts can also differ in diversity, density and accessibility to treatment procedures
Apical region
____ oxygen tension
Nutrients from the periradicular tissues: proteins and glycoproteins
Lower bacterial counts
Bacteria less accessible to treatment measures
Coronal region
____ oxygen tension
Nutrients from the oral cavity: carbohydrates
Higher bacterial counts
Microorganisms more accessible to treatment
- Root canal infection is a dynamic process with different bacterial species dominating at different stages.
- Shifts in the composition of the microbiota are largely due to changes in environmental conditions, particularly in regard to ____ tension and ____ availability.
ecologic
gradient
microbiota
lower
higher
oxygen
nutrient
• Facultative type of flora
○ ____ species
§ Ferment carbohydrates
• Then necrosis starts > O2 levels drop > loss of blood cirulcation > ____ conditions
○ ____ species
§ Metabolize proteins moreso than carbohydrates
○ ____ bacteria
• Specific species become established
○ Concept known as geography-related pattern > composition of the flora is different among diff patients, and among diff sites/teeth
○ Depend on the ecology of the enviro
§ What’s available and what bac initiate the infection
saccharolytic
anaerobic
asaccharolytic
proteolytic
• ____ is set up
• Food chain bt specific bacteria
• Streptomuyces/actino produce formic acid > metabolized by caphlobacter
○ Also produce acetic acid > liked by the pseudoramobacter
• Porp prevotalis > isobutytrate
○ Treponema like them
• Population turns over as the products become more abundant and more species become established
○ Contributes to growht of the bacteria in the infection and estab of a specific type of flora
IC food web
Consequences of Microbial Entry
Necrotic Pulp Conditions That Favor Microbial Colonization
- Necrotic pulp provides bacteria with moist, warm, nutritious and anaerobic environment for colonization.
- Environment protected from host defenses because of lack of active ____ circulation in the necrotic pulp tissue.
- Root canal walls are non-shedding surfaces conducive to persistent colonization and formation of ____.
- Major ecologic factors include ____ tension, type and amount of available nutrients and bacterial interactions. (temperature, pH, and receptors for adhesins may also be important)
- About ____ bacterial species, out of about 600 to 700 in the oral cavity, are consistently selected out for growth and survival in necrotic pulp tissue.
blood
complex communities (biofilms)
oxygen
10 to 20
Consequences of Microbial Entry
• ____ are the major type of microorganism implicated in the
pathogenesis of apical periodontitis.
• Root canal microbiota is dominated by bacterial morphotypes that include ____, rods, ____ and spirochetes.
• Involved bacteria are usually part of the ____ oral microbiota (“____ pathogens”).
bacteria cocci filaments normal opportunistic
• Stages of biofilm formation
• Biofilms need a supporting substratum > enamel on the surface, or the salivary pellicle coated enamel
○ In RC infection > dentin or the outer surface of a tooth structure
• Conditioning film > allows bac to stick to spec proteins
○ Ind ____ colonizing bacteria come in > stick and form micro colonies > inc in size due to cell div, and produce EC polysacc’s > forms EPS matrix (ECM - grey)
○ Other bacteiral congregations or lightly adherent groups move in (secondary colonizers) > biofilm becomes more complex
○ Bacteria are dividing, growth is away from the surface of the biofilm (lower surface), until the mature biofilm becomes large enough that bac begin to slough off > ____ stage: impt aspect of biofilm formation > allows biofilms to spread
§ Bac get knocked off > free in the enviro (planktonic state) > find a free surface again > biofilms can grow more
primary
dispersal
Complex microbial communities
• L: carious lesion ○ Evidence of disease w radiolucency around the root • Take the tooth > slice it longitudinally ○ Clear area = root canal ○ Pink = invading host cells (neutropihls) ○ Purple = bacteria § Deposited on the inner wall of the root • Enlarged that ○ Structure of the biofilm § Reminiscent of C □ Looks same as plaque formation and maturation; a lot of rods, but it's more dense where it's \_\_\_\_ to the wall; as move out from the biofilm the bacteria become more dispersed □ Specific interaction bt bacteria, and they're multiplying to form microcolonies ○ D - more cocci, not as filamentous § See other debris (cellular, etc.) that's sticking to the surface of the biofilm § Distance bt the two walls of the tooth > they're close together > biofilms can look quite different still
adherent
Complex microbial communities
____ biofilms generally observed in apical segment of approximately 80% of the root canals of teeth with primary or post-treatment apical periodontitis
Morphology of biofilms differed consistently from individual to individual by ____, morphotypes and bacterial cells/extracellular matrix ratio.
____ underneath biofilms were often invaded by bacterial cells from the bottom of the biofilm community
intraradicular
thickness
dentinal tubules
Complex Microbial
Communities (Biofilms) Criteria Used to Establish Causal Link Between Biofilms
and an Infectious Disease
- Infecting bacteria ____ to or associated with a surface.
- Direct examination of infected tissue shows bacteria forming ____ or microcolonies encased in an extracellular matrix.
- Infection is generally ____ to a particular site. Although dissemination may occur, it is a ____ event.
- Infection is difficult or impossible to eradicate with ____ in spite of the responsible microorganisms being susceptible to killing in the planktonic state.
- Ineffective host ____ is evident as suggested by the location of bacterial colonies in areas of host tissue associated with host inflammatory cells (polymorphonuclear neutrophils (PMN) and macrophages).
(6. ____ or significant disruption of biofilm structure and ecology leads to remission of the disease process.)
adhered clusters confined secondary antibiotics clearance elimination
Involvement of dentinal tubules
- Dentinal tubules have a ____ conformation and traverse the entire width of the dentin.
- Largest diameter (2.5 μm) is near the ____ and smallest diameter (0.9 μm) is near the ____ or cementum.
- Smallest tubule diameter is similar to the ____of most oral bacterial species (0.2 to 0.7 μm).
- When dentin is exposed the pulp is at risk of infection because of the ____ of normal dentin due to its tubular structure.
conical pulp enamel cell diameter permeability
Involvement of Dentinal Tubules
Bacterial Invasion of Dentinal Tubules in a Vital Pulp
- ____ movement of dentinal fluid and tubular contents influence dentinal permeability and may delay intratubular invasion by bacteria.
- Functional or physiologic diameter of the tubules is only 5-10% of the anatomic diameter seen by microscopy because of the presence of tubular contents.
- The few bacteria that reach the pulp may not be significant because the vital pulp can eliminate such a transient infection and rapidly ____ or remove bacterial products due to the presence of host defense molecules, such as ____ and components of the ____ system.
outward
clear
antibodies
complement
Involvement of Dentinal Tubules
Bacterial Invasion of Dentinal Tubules in a Non-vital Pulp
- Since most bacteria in the carious process are ____ they may invade dentin by repeated ____ which can “push” cells into the tubules.
- Bacterial cells may be forced into tubules by ____ pressures placed on dentin during mastication.
- Dividing cells can be observed within tubules indicating that bacteria can derive nutrients probably from degrading ____ processes, denatured collagen, bacterial cells that die during the course of infection and intracanal fluids that enter the tubules by capillary action.
nonmotile
cell division
hydrostatic
odontoblastic
Involvement of dentinal tubules
• Bacteria aren't actively invading the tubules > they get in indirectly • In this model (love and jenkinson) ○ The dentin is lined by \_\_\_\_ § Has specific regions that act as receptors for the adhesins on bact § Strepto gordondii > primary colonizer □ At end of tubule, receptor will find receptor and stick to the collagen □ Can grow in this area > start to divide and form chains > grow into the tubules not by moving as free cells, but as elongating as chains into the tubule ® Many of oral streptococci grow in \_\_\_\_ (how to diff from staphylococci) ○ Secondary colonizer comes along > has an \_\_\_\_ that recognizes a protein on the surface of the streptococci § Stick to the primary colonizer > not independently moving into the tubule, but carried when the streptococci chain \_\_\_\_ § The streptococci are dragging the secondary colonizers in ○ This is how tubules become infected
collagen
chains
adhesin
elongates
Diversity of endodontic microbiota
• Represents the distribution of various bacteria/members of taxons that are involved in endo infections ○ The difference > these analysis done from studies that where detection of bac were totally using molecular methods, totally using culturing methods, or using a combination of both methods • Molecular methods - PCR to 16s rRNA seq, to pyrosequencing (DNA arrays, etc.) • Culturing methods - automated systems (API), and serotyping to ID bacteria • Can see diff kjinds of bacteria using \_\_\_\_ methods as opposed to \_\_\_\_ methods ○ Some taxa (TM7, SR1) > contain bacteria that have never been cultured in the lab, but can now ID in clinical samples ○ Allow to detect presence even though can't visibly culture them in the lab • Some of the taxa > solely determined to be in taxa based on DNA/RNA sequence
molecular
culturing
Diveristy of the endodontic microbiota
• Shows phylogenetic relationship ○ Length of lines represent genetic distance § The closer two phyla are, the more closely related they are genetically § The length of the line indicates how far removed they are from earlier connection to another phyla • Represent the most commonly found types of bacteria present in endo inf ○ \_\_\_\_ > gram + ○ \_\_\_\_ > gram - ○ Bacteroidetes § P gingivalis is in this phylum • In terms of the species found in absecess, \_\_\_\_ and \_\_\_\_ make up the bulk of the species IDed in abscesses ○ Depicted in the previous slide ○ Another way of looking at the istributio of diff phyla in endo infections ○ Pertains to asbcesses § Three studies that were done w cultural, and three w molecular methods □ Bulk of bacteria are members of \_\_\_\_ and \_\_\_\_ ® Significant portion of bac we find in abscesses
firmocutes proteobacteria firmucutes bacteriodetes firmucutes bacteriodetes
• Representation of the phylogenetic tree of life
○ 3 domains
§ ____
§ ____
§ ____
□ Red ones are the ones he showed us two slides again
® Major phyla found in endo inf
□ Not all the phyla are found in endo infections
® Limitation/restriction
eukarya
archea
bacteria
• Divide endo infections into diff types ○ Intraradicular § Primary □ Initial \_\_\_\_ § Secondary □ Primary inf is cleared up, and a new inf occurs in the same canal ® May or may not be due to similar or diff bac found in the primary system ○ Extraradicular § \_\_\_\_ § \_\_\_\_
infection
dependent
independent
Primary infections w/ sympatomatic (acute) apical periodontitis
• Members of flora found in primary infections ○ Don't worry ab symptomatic • Detection of bacteria in a sample ○ \_\_\_\_ § 75% of samples contain this, not 75% of the bacteria in the inf are d denticola § Presence of bac in a sample ○ \_\_\_\_ § Assoc w periodontal dx ○ \_\_\_\_ is low on the list on being detected in these samples ○ Diverse group of bacteria; not so diverse in terms of genera, but diverse in species
treponema denticola
porphymonas gingivalis
enterococcus vicalis
Primary infections w/ asymptomatic (chronic) apical periodontitis
• Shift in terms of major players ○ T denticola has moved farther down ○ \_\_\_\_ has moved up ○ Enterococcus is still low on the list compared to the others • Overall, generally you see the same bacteria
dialister
