Although its prevalence has decreased dramatically in European countries, dental caries remains a burden for the society and especially for certain groups of the population. For example, 80% of the carious lesions are diagnosed in about 20% of the children. For years, the aetiology of this disease has been mainly related to environmental factors but recent data support the possibility of a human genetic contribution. Alteration of the post- eruptive enamel microstructure due to a mutation of a gene coding for a matrix protein could increase the susceptibility of the enamel to caries after tooth eruption. The main objective of this study will be to identify in young patients with severe caries incidence, the occurrence of mutations in several candidate genes which result in an alteration of the enamel microstructure that could explain the high caries susceptibility of the patient. With this aim, we will carry out a case- control multicentre European study on 250 young patients presenting several carious lesions and 160 young adults totally caries free. Patients with systemic or enamel pathologies such as amelogenesis imperfecta will not be included in the study. The study will consist of 2 visits, 1: inclusion and genetic test based on a salivary sample and 2: after 6 months, communication of the genetic test result to the patient and his parents. The main evaluation criteria will be the finding of a mutation on the candidates genes not resulting in an amelogenesis imperfecta phenotype but associated to a severe caries phenotype. If a direct relation between a mutation and a severe caries phenotype was shown, all the classical approaches, prevention protocols and treatments of caries would need to be reconsidered.