A histological method that can be used to estimate the time taken to form the crown of a permanent tooth.

Teeth contain an incremental record of their growth in the form of periodic growth markings that are literally embodied within the structure of enamel. These can be revealed when ground sections of teeth are prepared for transmitted light microscopy. This chapter sets out one method for estimating the time taken to form the crowns of permanent teeth. First, the daily rates of enamel formation are estimated at three positions within the crown close to the enamel dentine junction (EDJ). Then a 200 μm length along an enamel prism that take ∼80 days to form is followed out from the EDJ at the dentine horn. From this point a line is then tracked back along the direction of the oblique striae of Retzius that are contained within enamel to a lower position further along the EDJ. This procedure is repeated until the cervix of the tooth is reached. The total time for enamel formation is estimated by summing the number of 80 day segments traced out.