Preliminary insights into enamel formation in a human tooth from Dong Son Metal Period Northern Vietnam

Human dental enamel forms in a regular fashion, producing incremental and periodic layers that can be studied microstructurally. Long-period lines, known as striae of Retzius, are used by histologists to reconstruct dental growth and development in modern and ancient human populations. Here we report first and preliminary insights into enamel formation rates in an ancient human upper third molar representing a Dong Son Metal Age (c. 2000 BP) sample from northern Vietnam. Nine Retzius lines (RL) from the lateral enamel on the mesiobuccal paracone cusp were measured in a thin section to estimate the average Retzius periodicity (RP) between two adjacent RL’s. The average RL thickness was then analysed using daily secretion rates that range from 3.5 to 4.5 µm. The average RL thickness measured approximately 34.95 µm. The RP for this tooth lay between 7.77 and 9.99 days which suggests a single RP value that lies between 8 to 10 days. Our estimate of RP for this ancient Vietnamese individual’s tooth is higher when compared to data available for modern Chinese and Chinese-Singaporean populations. However, the RP for this individual from northern Vietnam lies within the range of RP’s between 6 to 12 days for modern human permanent teeth. Ongoing research will aim to source more dental samples to expand the RP dataset.