The application of synchrotron radiation for non-destructive study of human enamel during in situ demineralisation was investigated. Enamel samples of freshly extracted caries free third molars were prepared. One sample (control) was directly examined using synchrotron micro computed tomography. The other samples were integrated into four removable intraoral mandibular appliances under gold-micromeshes. Each appliance was worn by a randomly chosen participant throughout day and night. The desired demineralisation was therefore generated in a natural way in the oral cavity by acid producing bacteria and consume of acid and carbohydrate containing food. The depth and grade of structural changes were quantified after either 21 or 29 days of exposition in the oral cavity. By using µCT-synchrotron radiation we were able to visualise and quantify initial and further progressed stages of demineralisation. The development of mineral loss was dependent on the exposing time of the samples in the oral cavity and the individual nutrition behaviour and salivary properties of the participants. Keywords: synchrotron radiation, enamel, demineralization, in situ