Frequency, location, and direction of the lateral, secondary, and accessory canals.

Observation of 1,140 transparent teeth of adult humans was made to verify the frequency, location, and direction of the accessory, secondary, and lateral canals located at the radicular-apical area, at the body of the root, and in the base of the root. In 27.4% of the teeth studied, some type of ramification was observed; these ramifications were usually located in the apical area of the root. The premolars and molars showed the greatest variety of ramifications.