Growth rates of accessory human enamel: a histological case study of a modern-day incisor from Northern England

Abstract

This study investigates enamel growth of a modern-day human upper first incisor (S197) possessing an accessory cusp. Growth rates collected from the accessory enamel are compared to data collected from the primary cusp and healthy incisors from the same population. Upper first incisors (n=12) and S197 were analysed using histological methods. Daily secretion rates (DSRs) were calculated for inner, mid, and outer regions of cuspal and lateral sites. Additional DSRs were calculated for equivalent regions of S197’s accessory cusp. S197’s primary cusp DSRs were significantly faster than the accessory cusp for all lateral regions, but significantly slower in the inner and mid cuspal regions. S197’s primary cusp DSRs were also significantly faster than the healthy incisor sample for all lateral regions, but significantly slower in the inner and mid cuspal regions. The DSRs of the healthy sample were significantly faster than those of S197’s accessory cusp for all lateral regions, but significantly slower in the inner cuspal region. This case study displays that human teeth possessing accessory cusps can present varying DSRs to healthy teeth of the same population, and that accessory enamel growth may not follow the same pattern of increasing DSRs along the length of enamel prisms.