RESUMEN
The exploration of the relationship between the bearing of blood groups and caries susceptibility begins with an observation reported by Aitcheson and Carmichael[1] who reported a high percentage of blood group "O" and low percentage of blood group "A" in caries-resistant subjects and the converse in caries-rampant persons. Conflicting results have been obtained from a study of a large group of Chilean children. The study failed to demonstrate an association between ABO and MN blood groups and caries scores. Similar trend was also evident for the ABO an MN blood groups and caries scores relationship in a different age group[3,4 and 5]. On the other hand the study of O'Roark and Leyshon[6] in a group of young adults aged 15-16 year, showed that the MN blood group was associated significantly with increased caries activity. In the present study it was decided to overlook the accepted predisposing factors of dental caries and to investigate the relationship, if any, between blood mutations and dental caries among a group of young adult Egyptian population among whom caries is a less acute problem in comparison with the western populations