This is a caries index. The prevalence of caries in a population can be defined using DMFT. Careful examination with a mirror and probe is carried out to find small carious lesions. It is prudent to carefully check for tooth colored fillings to arrive at the accurate picture. Each tooth is assigned a score and all the scores are indicated in boxes on a DMFT chart.
0: No caries present. Fluorotic areas, and those with hard white lesions are to be ignored.
1: Caries is present. If the crown is affected, the crown is assigned the score of 1. If the root is affected then the root is assigned 1. Where the crown is entirely destroyed by decay but the root is present, the crown and root both are given a score of 1.
2: Filled teeth with secondary caries.
3: Filled teeth without caries. If a tooth is crowned because of a previous carious lesion, it is given a score of 3. If however a crown is present as an abutment or for aesthetic reasons, it is scored as 7.
4: A tooth missing because of decay. Only crowns are recorded as 4. The roots of such missing teeth are designated a 7 or 9.
5: A tooth missing for any reason other than decay.
6: Teeth on which sealant has been placed.
7: Tooth which is a part of a fixed bridge. It is also used to denote a root replaced by an implant. Teeth that have been restored by bridge pontics are scored 4 or 5. The roots of such teeth are scored as 9.
8: This is used for a space where the permanent tooth is unerupted but the primary tooth is not present. In case of a root, the surface of which is not visible in the mouth, the root is assigned an 8.
9: A tooth which cannot be scored because of reasons such as orthodontic treatment. It also applies to the root of a tooth which has been extracted. The crowns of such extracted teeth will be assigned a 4 or a 5.
To arrive at score the total number of carious, missing or filled teeth are calculated. For primary teeth the index is called ‘deft’ or ‘defs’ (decayed extracted filled)