Fluoride therapy in otosclerosis acts by which mechanism?

• A Inhibition of osteoclast-mediated bone resorption at the otic capsule
• B Stimulation of stapes footplate remineralisation
• C Anti-inflammatory effect reducing cochlear endolymph pressure
• D Conversion of active spongiotic bone into dense fluorapatite, reducing enzymatic breakdown ✓

Explanation

Sodium fluoride therapy in otosclerosis works by substituting fluoride ions for hydroxyl groups in hydroxyapatite, forming the harder and more stable fluorapatite crystal. This reduces the solubility and enzymatic susceptibility of the otic capsule bone, converting the active spongiotic (vascular) otosclerotic foci into a denser, less active state. It does not reverse existing fixation but may slow progression and reduce cochlear damage. CT of the petrous bone showing a 'double ring' or halo sign of demineralisation around the cochlea (cochlear otosclerosis) is an indication.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.