The University of Medicine in Debrecen hosted a significant event July 14-17. 1970. The 17th Congress of the European ORganisation for CAries Research (ORCA) was held here to pay tribute to the scientific activity of Professor Péter Adler, the lieder of the Stomatology Clinic in Debrecen. He achieved significant results in fluoride research and celebrated his 60th birthday that year. About 200 registered participants came from all over the world, of which 32 were locals. Of the 48 lectures, 5 were held by Hungarians (2 from Debrecen). The entire editorial board of the notable journal Caries Research was also present. This  international congress was the first event of local dentistry to be held in a socialist country and even decades later many well-known  researchers recalled the pleasant days of Debrecen.