Dental index or indices can be considered as the main tool of epidemiological studies in dental diseases, to find out the incidence, prevalence and severity of the disease, based on which preventive programs are adopted for their control and prevention. An index is an expression of clinical observation in numerical values. It is used to describe the status of the individual or group with respect to a condition being measured. By using a number scale and a standardized method for interpreting observation of a condition, an index score can be more consistent and less subjective than a word description of that condition. Indices using various criteria have been developed to compare the extent and severity of disease. For example, dental caries is indexed by the number of teeth or surfaces with carious lesion and fillings. An index for dental fluorosis identifies very mild, mild, moderate or severe involvement of enamel ranging respectively from white spot visible only when a tooth is dry to marked brown stain with pitting.Various factors associated with gingivitis and periodontal diseases have been used in the development of indices.