ABE Endodontic Microbiology and Pathology 4

Question 1

Which species of Actinomyces is most frequently implicated in extra-radicular actinomycosis, a cause of refractory periapical pathology?

Accepted Answer

Actinomyces israelii

Answer

Actinomyces naeslundii

Answer

Actinomyces viscosus

Answer

Actinomyces meyeri

Question 2

The Malassez epithelial cell rests in the periodontal ligament are significant in endodontic pathology because they:

Accepted Answer

Can proliferate to form the epithelial lining of a radicular cyst

Answer

Produce pro-inflammatory cytokines during periapical infection

Answer

Synthesize collagen to wall off periapical infections

Answer

Differentiate into osteoclasts under RANKL stimulation

Question 3

Which pattern of periapical cyst behavior has been proposed to explain why some cysts do NOT heal after successful root canal treatment?

Accepted Answer

True cyst — completely enclosed epithelial cavity independent of the canal

Answer

Pocket cyst (bay cyst) — open to the root canal

Answer

Lateral periodontal cyst

Answer

Odontogenic keratocyst

Question 4

A patient presents with a draining sinus tract traced to the apex of tooth #30. The most likely microbial etiology of this chronic presentation is:

Accepted Answer

Mixed anaerobic consortium dominated by gram-negative anaerobes

Answer

Predominantly aerobic, gram-positive cocci

Answer

Candida albicans fungal overgrowth

Answer

Single-species Staphylococcus aureus infection

Question 5

Leukotrienes (LTB4) contribute to periapical pathology primarily by:

Accepted Answer

Promoting chemoattraction of neutrophils to the infection site

Answer

Inhibiting osteoclast differentiation

Answer

Suppressing T-lymphocyte activation

Answer

Blocking prostaglandin synthesis

Question 6

In the context of endodontic microbiology, quorum sensing is best described as:

Accepted Answer

Cell-to-cell communication via chemical signals regulating virulence gene expression

Answer

Bacterial resistance mechanism against calcium hydroxide

Answer

The process of bacterial sporulation under nutrient deprivation

Answer

Horizontal gene transfer of antibiotic resistance plasmids

Question 7

Which histological feature differentiates an acute apical abscess from an acute exacerbation of chronic apical periodontitis (phoenix abscess)?

Accepted Answer

Presence of fibrous connective tissue and chronic inflammatory cells in the surrounding stroma

Answer

Exclusive neutrophil infiltration with no background tissue

Answer

Presence of cholesterol clefts

Answer

Absence of bone involvement