Demarcated opacities are often seen in first permanent molars and frequently associated with affected incisors. When the enamel hypomineralization is present in one or more first permanent molars, the condition is classified as molar incisor hypomineralization (MIH). 1-5 The prevalence of MIH is examined in several studies worldwide, and prevalence between 2.4% and 44% have been reported. 6 The studies were, however, carried out under un-standardized examination settings, including, for example, different classification systems, different light sources, and tooth drying protocols. Altogether, this might possibly explain the wide variation. A previous population-based study from Denmark among 647 6-to 8-year-old children with fully erupted first permanent molars showed that 37.3% (95% CI: 33.6%-41.0%) had