A 19-year-old patient presents with blue-gray discoloration of the incisal three-quarters of all teeth. History reveals use of minocycline during childhood and current use of amphetamine (Adderall). What is the MOST likely cause?

Correct answer: C. Minocycline use during tooth development

• A. Tobacco causes extrinsic brown/black staining, not the described intrinsic blue-gray discoloration.
• B. Amphetamine use can cause 'meth mouth' (severe decay) but does not cause intrinsic blue-gray tooth discoloration.
• C. Correct. Minocycline (a tetracycline-class antibiotic) causes tooth staining when taken during tooth development. Unlike tetracycline (which causes yellow-gray banding at the dentinoenamel junction), minocycline causes blue-gray staining in the incisal portions of teeth. The discoloration is due to minocycline chelating calcium ions in mineralizing dentin.
• D. Amelogenesis imperfecta affects enamel formation and causes diffuse enamel hypoplasia or hypomineralization — not the specific blue-gray incisal pattern described.