Bisoniana XCIII. Growth layers in tooth cement and dentine of European bison and its hybrids with domestic cattle

Abstract

For checking the possibility of age determination from histological structure of teeth, the structure of cement and dentine of incisors was studied in European bisons, Bison boaasus, (n=29) and hybrids of bison with cattle (n=9) and cattle (n=3). The number of cement layers was related to the known age of the animals. It was found that the number of primary incremental lines in the cement on the lingual surface of the incisor agreed with the age of the tooth. The formation of layers on the labial surface of the teeth older than 7 years progresses irregularly. The readability of cement layers in bison is poor, in hybrids it is slightly better, and in cattle it is good. Due to this, counting of layers by independent investigators gives a low agreement of estimates (in bisons and hybrids about 30%). Repeated counting produced an agreement between the number of incremental lines and age. Thus for an estimation of the number of cement layers a proper part of a tooth should be chosen and some experience must be gained. Layers of secondary dentine were well visible in the part adjacent to pulp cavity, but its line at the site of meeting of the primary dentine is not distinct. This makes impossible estimation of age of the studied animals by th s method. No relationship was noted between the structure of cement layers and environment where the animals were living (closed reserves, forest), pregnancy and lactation. The pattern of the first incremental line enable the estimation of animal birth season.