MJDF Pharmacology & Pain Control 4 — Questions and Answers
Question 1: What is the mechanism by which tetracyclines are deposited in developing teeth?
- Chelate with calcium ions in calcifying tissues forming tetracycline-calcium orthophosphate complexes — permanent staining (Correct answer)
- Absorbed by enamel after eruption
- Deposited only in cementum
- Cause enamel hypoplasia without staining
Correct answer: Chelate with calcium ions in calcifying tissues forming tetracycline-calcium orthophosphate complexes — permanent staining
Tetracyclines chelate with calcium ions during mineralisation of dentine and enamel, forming permanent yellow-brown fluorescent complexes; contraindicated in children under 12 and during pregnancy.
Question 2: What drug is used to prevent dry socket (alveolar osteitis) in high-risk patients?
- Chlorhexidine mouthwash pre- and post-operatively; oxidised cellulose or resorbable gelatin sponge intra-socket (Correct answer)
- High-dose amoxicillin routinely
- Topical lidocaine gel
- Clindamycin prophylaxis
Correct answer: Chlorhexidine mouthwash pre- and post-operatively; oxidised cellulose or resorbable gelatin sponge intra-socket
Pre-operative chlorhexidine mouthwash (0.12–0.2%) and intra-socket placement of resorbable materials (oxidised cellulose, Alvogyl) reduce dry socket incidence in high-risk patients (smokers, previous dry socket, lower molars).
Question 3: What is the dental significance of patients taking bisphosphonates for osteoporosis?
- Risk of medication-related osteonecrosis of jaw (MRONJ) after invasive dental procedures — requires risk assessment before extraction (Correct answer)
- No dental significance
- Prevents alveolar bone loss — beneficial for periodontitis
- Reduces caries risk
Correct answer: Risk of medication-related osteonecrosis of jaw (MRONJ) after invasive dental procedures — requires risk assessment before extraction
Bisphosphonates (oral and particularly IV) impair bone remodelling; invasive dental procedures (extractions, implants, periodontal surgery) can trigger MRONJ, requiring MDT risk assessment and preventive strategies.
Question 4: What is the mechanism of action of fluoride in caries prevention?
- Incorporates into hydroxyapatite as fluorapatite (more acid-resistant), inhibits bacterial enolase, and enhances remineralisation (Correct answer)
- Kills all oral bacteria
- Acts as a pH buffer in saliva
- Whitens enamel through oxidation
Correct answer: Incorporates into hydroxyapatite as fluorapatite (more acid-resistant), inhibits bacterial enolase, and enhances remineralisation
Fluoride forms fluorapatite (less soluble at acid pH), inhibits bacterial glycolysis (enolase inhibition reducing acid production), and promotes remineralisation of early carious lesions.
Question 5: What drug class should be avoided in patients with aspirin-sensitive asthma (Samter's triad) requiring dental pain control?
- All NSAIDs (cross-sensitivity is common) (Correct answer)
- Opioids
- Paracetamol
- Antibiotics
Correct answer: All NSAIDs (cross-sensitivity is common)
Samter's triad (asthma, nasal polyps, aspirin sensitivity) involves COX-1 inhibition shifting arachidonic acid to leukotriene production; all NSAIDs carry cross-sensitivity risk and must be avoided, with paracetamol used instead.
Question 6: What is the principal mechanism of action of nitrous oxide in conscious sedation?
- Inhibits NMDA glutamate receptors and modulates endogenous opioid system, causing analgesia and anxiolysis (Correct answer)
- Direct GABA-A agonist like benzodiazepines
- Blocks sodium channels like local anaesthetics
- Inhibits MAO-A
Correct answer: Inhibits NMDA glutamate receptors and modulates endogenous opioid system, causing analgesia and anxiolysis
Nitrous oxide primarily inhibits NMDA receptors (reducing excitatory neurotransmission) and stimulates endogenous opioid release, producing analgesia, anxiolysis, and mild sedation without significant respiratory depression.
MJDF Pharmacology & Pain Control 4
What is the mechanism by which tetracyclines are deposited in developing teeth?