A 6-year-old presents with diffuse white and brown mottling of permanent incisors but normal growth and TSH. Parents report frequent swallowing of fluoride toothpaste during early childhood. What is the most likely diagnosis and appropriate immediate counseling?

• A. Vitamin C deficiency presenting with enamel mottling; prescribe high-dose vitamin C and recommend increased citrus intake.
• B. Dental fluorosis from excessive early-life fluoride exposure; counsel parents to supervise brushing, use pea-sized toothpaste, and avoid swallowing topical fluoride products in young children.
• C. Congenital hypothyroidism causing enamel defects; start levothyroxine immediately and refer for urgent neonatal metabolic workup.
• D. Early childhood caries indicating current active infection; immediate extraction of affected teeth is required and fluoride should be stopped entirely.

Answer: (B)