Characterization of short-period and long-period incremental markings in porcine enamel and dentine-Results of a fluorochrome labelling study in wild boar and domestic pigs.

Mammalian dental hard tissues exhibit incremental markings that reflect the periodic variation of appositional growth rates. In order to use these markings to characterize dental growth processes and to infer life-history traits, an unequivocal identification of their periodicities is required. We performed a fluorochrome labelling study on forming enamel and dentine in molar teeth of wild boar and domestic pigs to establish the periodicity and temporal correspondence of incremental markings in enamel and dentine. The dominant incremental markings in enamel (laminations) and dentine (von Ebner lines) recorded in the pig teeth are of a daily nature. In addition, long-period incremental markings with a periodicity of 2 days were recorded in enamel (striae of Retzius) and dentine (Andresen lines). The 2-day growth rhythm was also expressed at the lateral crown surface, as evidenced by the pattern of perikymata. In enamel, also markings with a sub-daily periodicity, representing an ultradian growth rhythm, were observed. Our study provides experimental evidence for the periodicity of incremental markings in porcine enamel and dentine. The findings correct previous misconceptions on incremental markings in dental hard tissues of pigs and other ungulates that had led to erroneous conclusions regarding crown formation parameters.