Molar-incisor hypomineralisation: narrative review on etiology, epidemiology, diagnostics and treatment decision.

Molar-incisor hypomineralisation (MIH) is clinically defined as demarcated structural enamel defects affecting at least one first permanent molar with or without the involvement of incisors. It is foremost a qualitative developmental defect of systemic origin. The prevalence for MIH is estimated at 12.9% with significant differences between countries. Its etiology and pathogenesis are still not completely understood. Several environmental and medical causes have been suggested to alter enamel maturation. The hypomineralised enamel may collapse shortly after eruption and as a consequence caries lesions seem more likely to develop. Besides cavitation, hypersensitivity and/or pain are the hallmarks of clinical symptoms. Both are associated with increased dental anxiety and fear of children suffering from MIH. Consequently, patients' care and management are challenging and necessitates a large range of non-, micro- and invasive strategies. MIH might be mixed up with three different other types of developmental defects in the enamel: fluorosis, enamel hypoplasia, and amelogenesis imperfecta. Careful diagnostic differentiation should be made before starting any dental treatment. A recent published classification system links the severity of the lesion to a treatment need index. This index is based on four values regarding two key symptoms: hypersensitivity and post-eruptiv enamel breakdown (PEB). Without PEB sealing is strongly recommended in order to prevent caries. For hypersensitive teeth as well as those with PEB use of glass ionomer cement as an intermediate cover, but mainly composite resins are materials of choice. For improvement of aesthetically compromised MIH-incisors, the resin infiltration technique has been proposed.