Bottom left
The bottom left portion of the IOTN ruler is used to measure reversed overjets. The method is similar to that described for the top left portion. However, this time the left hand side of the ruler is placed against the UPPER incisors, and the reading is recorded by seeing in which zone the lower incisors are.
ms = masticatory or speech difficulties present. Award the higher grade i.e 4 or 5.