ORE Part 1 Pharmacology in Dentistry 4

Question 1

What is the mechanism of action of bisphosphonates and why are they relevant in dental practice?

Accepted Answer

Inhibit osteoclast function by blocking the mevalonate pathway, reducing bone resorption — dental relevance: MRONJ (medication-related osteonecrosis of the jaw) is a rare but serious complication after extractions

Answer

Bisphosphonates inhibit osteoclasts, reducing bone turnover. MRONJ (medication-related osteonecrosis of the jaw) is a rare but serious complication, especially with IV bisphosphonates (used in metastatic cancer), manifesting as exposed, necrotic jaw bone, often triggered by extractions.

Question 2

Which antibiotic can reduce the efficacy of the combined oral contraceptive pill?

Accepted Answer

Current evidence suggests ONLY enzyme-inducing antibiotics (e.g., rifampicin) reduce OCP efficacy — broad-spectrum antibiotics no longer considered to do so per FSRH 2019 guidance

Answer

FSRH updated guidance (2019): non-enzyme-inducing antibiotics (amoxicillin, metronidazole, etc.) do not significantly reduce OCP efficacy. Only enzyme inducers (rifampicin, some anticonvulsants) require additional contraceptive precautions.

Question 3

What is chlorhexidine's mechanism of action and why is it used in dentistry?

Accepted Answer

Cationic bisbiguanide that binds to bacterial cell membranes, disrupting integrity at bactericidal concentrations — used as antimicrobial mouthwash, irrigation, and periodontal gel

Answer

Chlorhexidine binds to negatively charged bacterial cell walls, disrupting membrane permeability. At low concentrations it is bacteriostatic; at higher concentrations bactericidal. It has broad-spectrum activity and substantivity (binds to oral surfaces, releasing slowly).

Question 4

A patient with a known penicillin allergy (anaphylaxis) requires a dental antibiotic. Which antibiotic should be avoided?

Accepted Answer

All cephalosporins (due to cross-reactivity risk — approximately 1–2% with true anaphylaxis history, though generally amoxicillin is clearly contraindicated)

Answer

In a patient with confirmed anaphylactic penicillin allergy: amoxicillin (penicillin) and cephalosporins (cross-reactivity ~1–2%) should be avoided. Safe alternatives for dental infections include metronidazole, clarithromycin, or clindamycin.

Question 5

What is the rationale for prescribing dexamethasone before lower third molar surgery?

Accepted Answer

Prophylactic corticosteroid reduces post-operative trismus, swelling, and pain by suppressing inflammatory mediators before surgical trauma occurs

Answer

Pre-operative dexamethasone (4–8 mg IM or IV) reduces post-surgical trismus, facial swelling, and pain by pre-emptively suppressing the inflammatory cascade. It is used in third molar surgery and other oral surgical procedures.

ORE Part 1 Practice Test

ORE Part 1 Practice Test

ORE Part 1 Pharmacology in Dentistry 4