Microscopically, perikymata (Greek plural of περικύμα, perikyma) are the pits around the long prisms of tooth enamel. They indicate the places where enamel-producing cells used to make contact with neighboring cells and are the result of normal enamel apposition.
Grossly, perikymata are incremental growth lines that appear on the surface of enamel as a series of grooves. Each perikyma is thought to take approx. 8–10 days to form and thus the count of perikymata may be used to assess how long a tooth crown took to form. They may disappear as the enamel wears over a period of time.
They are thought to indicate the termination of striae of Retzius at the surface of enamel. They can be found on all teeth, but are usually the easiest to notice on canines.