This prospective, multi-centre clinical study has been designed to assess the safety and performance of the Calcivis System. The device under evaluation comprises a hand-held customized intra-oral camera which takes images of a lesion on a tooth surface immediately before and after application of a disclosing solution which contains a bioluminescent photo-protein. The photo-protein detects free calcium ions on the tooth surface and produces a light signal if the caries lesion is active.