ABE Endodontic Microbiology and Pathology 3

Question 1

Which anaerobic species is considered a 'keystone pathogen' capable of restructuring the entire microbial community in endodontic infections despite low abundance?

Accepted Answer

Porphyromonas endodontalis

Answer

P. endodontalis, like P. gingivalis, can modulate the local microbiome and immune response disproportionate to its numbers, fitting the keystone pathogen model.

Question 2

Condensing osteitis (focal sclerosing osteomyelitis) is best characterized as:

Accepted Answer

A reactive bone formation response to low-grade pulpal inflammation

Answer

Condensing osteitis represents reactive periapical bone sclerosis in response to chronic, low-grade pulpal infection or irritation.

Question 3

Which component of gram-negative bacterial cell walls is most responsible for stimulating macrophages to release IL-1β and TNF-α in periapical tissues?

Accepted Answer

Lipopolysaccharide (LPS)

Answer

LPS (endotoxin) from gram-negative bacteria is a potent stimulator of macrophage-derived pro-inflammatory cytokines via TLR4 signaling.

Question 4

During the transition from pulp necrosis to periapical abscess formation, which process represents the earliest response at the periapex?

Accepted Answer

Vascular dilation and neutrophil emigration

Answer

The earliest periapical response involves vascular dilation and neutrophil emigration as the acute inflammatory response begins.

Question 5

Extra-radicular infection most commonly involves which microbial structure adherent to the external root surface?

Accepted Answer

Bacterial biofilm on the root apex (apical biofilm)

Answer

Extra-radicular infection often manifests as an apical biofilm on the external root surface, which may explain persistent periapical pathology after adequate root canal treatment.

(ABE) American Board of Endodontics Practice Test

(ABE) American Board of Endodontics Practice Test

ABE Endodontic Microbiology and Pathology 3