Pharmacology · patient case question
Bisphosphonates exert their effect primarily on which cell?
Patient case: Bisphosphonates and a Diastema
Patient: 67-year-old female
Chief Complaint: “I've always hated the gap between my front teeth. Can it be closed?”
Background: Osteoporosis, on oral alendronate for four years. Tooth #8 was root treated eight years ago.
Medications: Alendronate 70 mg weekly, calcium, vitamin D
Vital Signs: BP 134/78 mmHg · HR 70 bpm · RR 16 · T 98.4°F
Findings: A 2.5 mm midline diastema between #8 and #9. Tooth #8 is root treated with an intact but discoloured crown; #9 is vital and unrestored. Periodontium is healthy with no bone loss.
Show answer and explanation
Correct answer: A. Osteoclasts
- A. CORRECT. Bisphosphonates bind avidly to hydroxyapatite and are taken up by OSTEOCLASTS during bone resorption. Nitrogen-containing bisphosphonates then inhibit farnesyl pyrophosphate synthase in the mevalonate pathway, which prevents prenylation of the small GTPases the osteoclast needs to maintain its ruffled border and cytoskeleton. The osteoclast loses function and undergoes apoptosis. Resorption falls, bone density rises — and remodelling is suppressed, which is why the jaws, with their high turnover, become vulnerable.
- B. Fibroblasts produce connective tissue matrix and are not the target.
- C. Odontoblasts form dentine and are unrelated.
- D. Osteoblasts build bone. They are affected indirectly through the coupling of resorption and formation, but they are not the target. Anabolic agents such as teriparatide act on the osteoblast lineage.
Note: Bisphosphonates have a half-life in bone measured in YEARS — often more than ten. This is why stopping the drug before an extraction ('drug holiday') has limited and debated benefit, and why the exposure history matters more than current use.