Dental indices provide a quantitative method for measuring, scoring, and analyzing dental conditions in individuals and groups. An index describes the status of individuals or groups with respect to the condition being measured. Oral health surveys depend on dental indices, as do researchers and clinicians, to help in understanding trends and patient’s needs. In dentistry, indices are commonly used for measuring a patient’s periodontal status, dental indices can measure the amount of plaque and calculus present or not present in a patient’s mouth, the amount of bleeding present in the gingiva, the amount of tooth mobility present at a given time, the amount of fluorosis present, and the number of decayed, missing, or filled teeth present. Therefore it becomes important to have knowledge of different dental indices, their uses, advantage and limitations of each. With this objective this chapter explains what an index is and what are the properties and requisites of an ideal index. A detailed description of the indices commonly used in dentistry can help the reader in evaluation and monitoring the progress and maintenance of oral health of their patients in clinical practice along with their applications in clinical trials and epidemiological surveys.