A collection of toothbrushes (nearly 5000 specimens), originally owned by Auschwitz-Birkenau concentration camp prisoners, after having been stored for over 60 years, has undergone a high degree of chemical deterioration. The firs step of this research was to establish the chemical nature of the material used to make them. This was celluloid. Results of natural aging included evaporation of the plasticizer camphor, as well as liberation of highly concentrated nitric acid. These phenomena caused the crumbling of the toothbrushes' material. In this work, methods of deacidification were developed, and reinforcement of the structure of the toothbrushes was carried out.