There is presently alarming rate of increase in the prevalence of dental caries in developing countries! A variety of microbial factors have been associated with dental caries activity. Lactobacilli, however seem to be..? Dental caries is a multi factorial disease in which there is an interaction between three principal factors, a. or decay . All the factor must be present and must interact with each other for dental caries develop. Varies observation indicate that a causal relationship between Streptococcus Mutants and the development of the early carious lesion of enamel. In addition a, fourth factor time, must be consider. It is similar to the Greek word ker meaning death. The word caries is derived from latin, meaning ?rot. Dental caries is defined as an infectious microbiologic disease of the teeth that results in localized dissolution and destruction of calcified tissue. A susceptible Host tissue (b) Micro flora with a cariogenic potential (c) A suitable local substrate.