Molar Incisor Hypomineralization (MIH)

Molar Incisor Hypomineralization (MIH) is a qualitative developmental enamel defect of systemic origin affecting one to four permanent first molars, frequently with associated permanent incisor involvement. Prevalence ranges 10-20% globally with significant geographic variability. The condition arises from disturbance of ameloblast function during the maturation phase of enamel development, occurring in the first three years of life. Affected enamel demonstrates reduced mineral content (10-20% lower than normal), increased porosity, altered protein content, and reduced mechanical properties.

Etiology is multifactorial and incompletely understood; proposed contributors include pre-, peri-, and postnatal complications (hypoxia, prematurity, low birth weight), childhood illness in the first three years (high fever, recurrent respiratory infections, otitis media, asthma), antibiotic use (especially amoxicillin), environmental toxins (dioxins, bisphenol A), and breastfeeding patterns. Genetic predisposition with polymorphisms in enamel matrix genes has been identified.

Clinical presentation includes demarcated opacities (white-cream, yellow, or yellow-brown) with intact surface enamel initially; in more severe cases, post-eruptive enamel breakdown (PEB) creates atypical caries-like lesions, often with rapid extension into dentin. Affected molars exhibit hypersensitivity to thermal stimuli and during toothbrushing, anesthesia is often inadequate (high pulpal pain threshold concerns), and dental anxiety is common. Management is graded by severity: mild (desensitization with CPP-ACP, fluoride varnish, resin infiltration), moderate (preventive resin restorations, glass ionomer, composite), severe (full coverage with stainless steel crown in children, full crown later, or extraction with orthodontic management for first molars at appropriate skeletal age 8-9 years).