Although effective methods are known for prevention & management of dental caries ,it is a major problem affecting mankind ,in that its manifestations persist throughout life despite treatment .There are practically no geographic areas in the world whose inhabitants do not exhibit some evidence of dental caries. It effects the persons of both genders in all socio-economic strata & every age group. Subjects who never develop carious lesions are designated caries-free & no satisfactory explanation is given. Many investigators have studied various aspects of dental caries for century. Despite this, many aspects of etiology & pathophysiology of caries are still obscure & efforts at prevention have only been partially successful.