Health examination is not complete without the oral health assessment. The presence of quantifying the disease prevalence, incidence and related factors is an important operation, one that is necessary to the eventual improvement of dental public health. The study of diseases occurrence and severity has to be quantitatively and qualitatively measured which is called as index or indices or indexes which is very important tool in the branch of dental public health and in study of epidemiology. Measuring oral diseases in a population however requires a more standardized and objective approach to the oral examination of group members. Epidemiological studies require that disease to be measured quantitatively.