Dental caries is the disease of civilization is affecting mankind since the dawn of the time. Caries has also been noted in the fossil remains of pithecanthropous erectus and homo rhodesiensis, early ancestors of man. Dental caries is one of the most common chronic infectious diseases in the world. There are three major hypothesis for the etiology of dental caries, the specific plaque hypothesis, the non specific plaque hypothesis, and the ecological plaque hypothesis. The specific plaque hypothesis has proposed that only a specific species such as streptococcus mutans, on the other hand non specific plaque hypothesis maintains the caries in the outcome of overall activity of the total plaque microflora.rnThe ecological plaque hypothesis suggests that caries is a result of Shift in balance of the resident microflora driven by changes in local environmental changes. rnDiagnostic microbiology rn1. Clinical request and provision of clinical informationrn2. Collection and transport of appropriate specimenrn3. Laboratory analysisrn4. Interpretation of the microbiology report and use of the information