Cheese molars (MIH: molar incisor hypomineralisation) can be recognized not only by their colour abnormalities but also by their hypersensitivity. Clinical management of these teeth may become challenging by the chronic hypersensitivity, which makes various steps of a treatment, such as pain control or light curing of any type of composite restorations, difficult or even impossible, despite profound local anesthesia. Hypersensitivity can be detected by the clinician based on the patient's statements or reaction. On the other hand, colours and structural abnormalities can be easily assessed by visual inspection. The aim of this study is to determine the relationship between hypersensitivity and the colour of the enamel defect on young first permanent molars. A correlation between colour of the defect and hypersensitivity could enable early prognosis leading to preventive measures in order to delay, amplify or even avoid the onset of the symptoms. Children diagnosed with MIH on their first permanent molars of different severity are matched to children with sound molars. They are identified by the annual school dental check-up and are invited to take part in the study. The children will be invited to the university dental clinic via letter for the first appointment. Upon parental consent, the teeth will be photographed and scanned as well as investigated for hypersensitivity through a gentle air blast.