The first permanent molar (FPM) plays an essential role in the masticatory function by contributing to the implementation and the maintenance of the occlusion. However, it is considered as the most frequently affected and the earliest affected tooth by caries; 27.4% of the 6-8 years old children have developed at least one cavity on one of the four first permanent molars, according to a study conducted among 3276 school children in Casablanca .Therefore, the FPM should benefit from special vigilance on the part of the practitioner to ensure that any early carious lesion is intercepted. In addition, the FPM, due to its period of mineralization coinciding with early childhood diseases, can erupt with a structural abnormality. Molar incisor hypomineralization (MIH) is considered to be the most common defects observed on first permanent molars among children. A study conducted among 1077 children aged 7-10 years enrolled in schools in Casablanca showed that 7.9% of children were affected with MIH. About 84.7% of the children had the four molars affected. Children with HIM had a significantly higher prevalence of caries: 78.8 versus 33.5%.These structural abnormalities of the enamel must be carried out earlier to ensure that the coronary anatomy is the least compromised.