The cold light probe ‘Goettingen’ with its specially polished surface was developed for the early detection of approximal caries. Clinical studies show that with the help of transillumination, more than twice as many carious defects were detected as with probes and mirrors. In comparison more dental caries were visible with fiber optics than with x-ray examinations, as studies by Prof. Dr. Pieper prove. The probe, together with an additional diagnostic probe on an LED basis, was further developed, and now offers the best possibility for mobile fields of application.