A 17-year-old patient, recently incarcerated for methamphetamine use, presents with blue-gray discoloration of multiple permanent teeth that does not correspond to carious lesions. What is the most likely cause of the discoloration?

Minocycline, a tetracycline-class antibiotic commonly prescribed for acne and frequently used in correctional facilities, can cause blue-gray to green-gray discoloration of teeth in adolescents and young adults even after tooth development is complete. Unlike classic tetracycline staining (which occurs during tooth formation, ages 0–8), minocycline deposits in already-formed teeth and bone, causing discoloration of the crown and root. The discoloration is irreversible and is caused by minocycline oxidation products forming complexes with iron in the dental tubules. Methamphetamine causes rampant caries ('meth mouth') but not this type of diffuse intrinsic discoloration.