Striae of Retzius

Brownish lines, the striae of Retzius, develop as a result of a change in the growth process.

Occasional darker striae or grooves of Retzius result from systemic disturbances in the human body.

Consequently, the line of Retzius appears broader and much more prominent, often presenting a brownish colour under the microscope.

The neonatal line is the darkest band, which represents the disrupted enamel formation due to the stress of being born.

The striae of Retzius often extends from the Dental-enamel junction to the outer surface, ending in shallow pits known as perikymata.

Tooth of a Paranthropus robustus with striae of Retzius visible on the left side
Striae of Retzius visible on the lower incisors of a 26-year-old patient.
The terminations of striae of Retzius in a canine, called perikymata. (Visible in the picture's high resolution)