Pathway 15-6 Primary Intraradicular Infection

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Questions and Answers

What role is hypothesized for herpesviruses in apical periodontitis?

Directly destroying bacteria within the root canal.

Preventing the reactivation of pathogenic bacteria during inflammation.

Impairing local host defenses which increases bacterial overgrowth. (correct)

Providing a beneficial relationship with local immune cells.

Which statement regarding herpesviruses and apical periodontitis is likely true?

Herpesvirus-infected inflammatory cells may respond to bacterial infection. (correct)

Herpesviruses act solely as contributors to the healing process.

Herpesviruses are always present as active infections in lesions.

The role of herpesviruses in apical periodontitis is conclusively established.

What impact might reactivation of herpesviruses have on host immune responses in apical periodontitis?

Enhancement of the immune response to infectious agents.

Minimization of inflammation in the periradicular area.

Increased production of antibodies against herpesviruses.

Impairment of local defense cells' ability to respond effectively. (correct)

Which type of bacteria predominantly characterize in LATE stages of primary intraradicular infections?

Anaerobic bacteria Signup and view all the answers

How does the size of an apical periodontitis lesion correlate with bacterial species richness?

Larger lesions are associated with increased bacterial diversity Signup and view all the answers

⭐️What is the range of bacterial cells that may inhabit a necrotic pulp tissue?

10^3 to 10^8 per root canal Signup and view all the answers

⭐️What is the average number of species found in infected root canals based on molecular studies?

10 to 20 species Signup and view all the answers

Which of the following genera is not typically associated with primary intraradicular infections?

E. coli Signup and view all the answers

What is the implication of the fifth-generation HTS studies on bacterial diversity in root canals?

It indicates that diversity may be even higher than previously thought Signup and view all the answers

⭐️What percentage of the endodontic microbiota in primary infections is composed of uncultivated species?

40% to 66% Signup and view all the answers

Which bacteria were found to be significantly higher in samples from abscesses compared to asymptomatic teeth?

Porphyromonas endodontalis Signup and view all the answers

Which factor is NOT mentioned as influencing the microbial ecology of the root canal?

Presence of antibiotics Signup and view all the answers

What is the main source of nutrients for bacteria in the root canal system?

Necrotic pulp tissue Signup and view all the answers

Which method has revealed significant differences in bacterial communities in symptomatic and asymptomatic teeth?

Molecular biology techniques Signup and view all the answers

What type of environment does a necrotic root canal provide for bacterial colonization?

Moist, warm, and anaerobic Signup and view all the answers

What determines the composition of the root canal microbiota?

Ecological determinants Signup and view all the answers

⭐️How does the bacterial community's pathogenicity relate to abscess outcomes?

Different species combinations may influence pathogenicity. Signup and view all the answers

What causes shifts in the composition of microbiota within the root canal?

Changes in environmental conditions. Signup and view all the answers

⭐️⭐️During which stage of pulpal infection do facultative bacteria primarily dominate?

Initial infection phase Signup and view all the answers

⭐️What type of bacterial species initially dominates in the root canal system during the early stages of infection?

Saccharolytic species Signup and view all the answers

Which of the following factors primarily influences the shifts in the microbiota composition in the root canal system?

Oxygen saturation levels and nutrient availability Signup and view all the answers

⭐️What is the critical nutrient source for bacteria during the later stages of the infectious process?

Proteins and glycoproteins from exudate Signup and view all the answers

⭐️Which type of bacterial interaction enhances the survival capacity of the involved species in the root canal?

proteinases Signup and view all the answers

What is coaggregation in the context of bacterial colonization?

The direct adherence of bacteria to one another Signup and view all the answers

In what stage does the dominance of asaccharolytic species occur within the root canal system?

Later stages of infection Signup and view all the answers

What is the role of negative interactions between bacterial species in the root canal?

Limiting population densities Signup and view all the answers

⭐️Which nutrient form is predominantly utilized by anaerobic bacteria in the apical part of the canal?

Peptides or amino acids Signup and view all the answers

What is the primary reason viruses are not found in necrotic root canals?

Viruses require living cells for replication Signup and view all the answers

What type of microorganisms has been reported in some cases, though inconsistently detected, in primary endodontic infections?

Archaea Signup and view all the answers

What characteristic behavior do fungi exhibit in relation to primary intraradicular infections?

They are more commonly found in posttreatment disease as compared to Primary infection. Signup and view all the answers

What is the effect of induction of periradicular inflammation on nutrient availability?

Increases protein availability from exudate Signup and view all the answers

Which of the following distinguishes archaea from bacteria?

Ability to thrive in extreme environments Signup and view all the answers

What does DGGE, T-RFLP, or HTS analysis reveal about endodontic bacterial communities in symptomatic compared to asymptomatic teeth?

There are significant differences in the structure of bacterial communities between symptomatic and asymptomatic teeth. Signup and view all the answers

How do molecular techniques like DGGE, T-RFLP, or HTS contribute to understanding endodontic infections?

They reveal the intricate details of bacterial diversity and community structures. Signup and view all the answers

⭐️What type of interaction allows a pair of species to attach to one another?

Receptor-adhesin interactions, generally lectin-like Signup and view all the answers

⭐️What is a characteristic feature of the receptor-adhesin interactions between species?

They require specific proteins and carbohydrates on the surfaces of the species Signup and view all the answers

Which component primarily mediates the attachment between two species in receptor-adhesin interactions?

Specific surface proteins acting as receptors Signup and view all the answers

⭐️What type of molecular interaction is commonly associated with receptor-adhesin bonding?

Lectin-like interactions between proteins and carbohydrates Signup and view all the answers

⭐️In receptor-adhesin interactions, what is the role of the carbohydrate present on the surface of a species?

To serve as the binding site for specific proteins Signup and view all the answers

Study Notes

Primary Intraradicular Infection

Primary intraradicular infection is caused by bacteria in necrotic pulp tissue of untreated teeth.
This can develop from previous pulp invasion or from new bacteria colonizing the root canal.
Primary infections are dominated by anaerobic bacteria.
The number of bacterial cells can range from 10^3 to 10^8 per root canal.
Molecular studies have found a mean of 10 to 20 species/phylotypes per infected canal.
Canals of teeth with sinus tracts can have a much larger number of diverse species.
The size of apical periodontitis lesions is proportionally related to the number of bacterial species and cells.
Larger apical lesions have higher bacterial diversity and density.
The most prevalent bacterial species in primary infections belong to different genera of gram-negative and gram-positive bacteria.
Approximately 40% to 66% of the endodontic microbiota in primary infections is composed of uncultivated species.
The structure of bacterial communities in symptomatic teeth, including abscesses, is significantly different from asymptomatic teeth.
The dominant species in asymptomatic versus symptomatic cases are different, and there are more species in symptomatic cases.
Levels of specific pathogenic species, like Porphyromonas endodontalis, are significantly higher in abscesses.

Geographic Influence

Findings from different countries often vary in the prevalence of species involved in endodontic infections.
Studies have shown a geographical influence in the composition of the root canal microbiota.
The factors that lead to these differences remain unconfirmed.

Microbial Ecology and the Root Canal Ecosystem

Necrotic pulp provides a moist, warm, nutritious and anaerobic environment for bacterial growth.
Root canal walls are nonshedding surfaces, allowing persistent colonization and complex community formation.
The necrotic root canal is a fertile environment for bacterial growth.
Only a limited assortment of oral species colonize the root canal, suggesting ecological determinants.
Major factors influencing the composition of the root canal microbiota: oxygen tension, nutrient availability, and bacterial interactions.
In the initial stages of infection, facultative bacteria dominate.
As oxygen is depleted, an anaerobic environment develops, favoring the growth of obligate anaerobic bacteria.
Anaerobic conditions become more pronounced in the apical third of the canal as time progresses.
Nutrient sources for bacteria in the root canal system: necrotic pulp tissue, proteins and glycoproteins from tissue fluids and exudate, components of saliva, products of bacterial metabolism.
The main canal, with its higher volume, harbors the highest concentration of bacteria, particularly fastidious anaerobic species.
Shifts in the composition of the microbiota can also be dependent upon nutrient utilization.
Saccharolytic species dominate in the early stages, then outnumber asaccharolytic species, dominating later stages.
As infection progresses, proteins become the principal nutrient source, favoring the establishment of anaerobic species that utilize peptides or amino acids.

Bacterial Interactions

Different bacterial species interact due to their close proximity within the root canal.
Early colonizers play a role in dictating the composition of the community.
Positive interactions enhance bacterial survival and allow coexistence.
Nutritional interactions, including food webs and bacterial cooperation, improve metabolic efficiency.
Negative interactions, like competition and amensalism, limit population densities.
Coaggregation, a specific interaction where bacteria adhere to bacteria already attached to surfaces, facilitates colonization and metabolic interactions.

Other Microorganisms in Endodontic Infections

Fungi are occasionally detected in primary intraradicular infections, especially Candida species.
Archaea, often extremophiles, have been found in some but not all studies of primary endodontic infections.
No archaea are known human pathogens, and their role in apical periodontitis is unclear.
Viruses, being inanimate, cannot prosper in the necrotic root canal.
Viruses have been detected in root canals only in teeth with vital pulps.
Herpesviruses have been found in some apical periodontitis lesions, but their role in the disease is not well established.

Summary

The bacterial composition of primary intraradicular infections is complex and influenced by numerous factors, including geographic location and bacterial interactions.
The shift from a primarily aerobic to anaerobic environment in the necrotic root canal allows different species to dominate at different stages of infection.
The role of other microorganisms like fungi, archaea, and viruses in endodontic infections remains unclear, requiring further research.

Endodontic Bacterial Communities

Molecular studies using DGGE, T-RFLP, or HTS analysis have shown differences in the structure of bacterial communities in symptomatic and asymptomatic teeth.
Symptomatic teeth, including those with abscesses, exhibit significantly different bacterial community structures compared to asymptomatic teeth.

Receptor-Adhesin Interactions

Species can attach to each other through specific receptor-adhesin interactions.
These interactions are often lectin-like.
Lectin-like interactions involve a protein on one species attaching to a carbohydrate on the other.

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