M Christopher Dean1, Louise Humphrey2, Alix Groom3, Brenna Hassett4. 1. Department of Earth Sciences, Centre for Human Evolution Research, Natural History Museum, Cromwell Road, London SW7 5BD, UK; Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK. Electronic address: ucgacrd@ucl.ac.uk. 2. Department of Earth Sciences, Centre for Human Evolution Research, Natural History Museum, Cromwell Road, London SW7 5BD, UK. 3. Bristol Bioresource Laboratories/MRC Integrative Epidemiology Unit, Population Health Sciences, Bristol Medical School, University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN, UK. 4. Department of Earth Sciences, Centre for Human Evolution Research, Natural History Museum, Cromwell Road, London SW7 5BD, UK; Institute of Archaeology, University College London, Gordon Square, London, WC1H 0PY, UK.
Abstract
OBJECTIVES: Deciduous canines are now used increasingly in archaeological and forensic studies to establish the time of birth and as a retrospective source of trace elements incorporated into enamel before and after birth. However, data on the variability of deciduous enamel formation times are scarce. Our objectives were to use daily incremental markings to estimate daily secretion rates, the timing of prenatal, postnatal and total enamel formation and any changes in enamel coverage or prism and stria orientation that occur during enamel formation. MATERIALS AND METHODS: Longitudinal ground sections of 81 deciduous canines were studied with transmitted light microscopy. High-resolution digital images were imported from an Olympus VS-120 virtual slide scanning system into a geographic information system (ArcGIS, ESRI USA) for quantitative and statistical analyses of linear, angular and area measurements of buccal enamel. RESULTS: Daily rates of enamel secretion close to the EDJ were faster than in permanent enamel (3.23 μm/day, SD = 0.54). Prism and stria angles subtended to the EDJ both increased through crown formation. Enamel coverage was low in the cusp and cervix but maximal ∼150 days after birth. The mean prenatal enamel formation time was 118 days (range 60-150, SD, 29.2, n = 24). The overall mean postnatal enamel formation time was 319 days (range 210-420, SD 50.6, n = 67). CONCLUSIONS: Daily enamel secretion rates compared well with previous studies of deciduous enamel, however, enamel extension rates in deciduous cuspal enamel were notably lower. The variability of both prenatal and postnatal deciduous enamel formation times was greater than previously reported.
OBJECTIVES: Deciduous canines are now used increasingly in archaeological and forensic studies to establish the time of birth and as a retrospective source of trace elements incorporated into enamel before and after birth. However, data on the variability of deciduous enamel formation times are scarce. Our objectives were to use daily incremental markings to estimate daily secretion rates, the timing of prenatal, postnatal and total enamel formation and any changes in enamel coverage or prism and stria orientation that occur during enamel formation. MATERIALS AND METHODS: Longitudinal ground sections of 81 deciduous canines were studied with transmitted light microscopy. High-resolution digital images were imported from an Olympus VS-120 virtual slide scanning system into a geographic information system (ArcGIS, ESRI USA) for quantitative and statistical analyses of linear, angular and area measurements of buccal enamel. RESULTS: Daily rates of enamel secretion close to the EDJ were faster than in permanent enamel (3.23 μm/day, SD = 0.54). Prism and stria angles subtended to the EDJ both increased through crown formation. Enamel coverage was low in the cusp and cervix but maximal ∼150 days after birth. The mean prenatal enamel formation time was 118 days (range 60-150, SD, 29.2, n = 24). The overall mean postnatal enamel formation time was 319 days (range 210-420, SD 50.6, n = 67). CONCLUSIONS: Daily enamel secretion rates compared well with previous studies of deciduous enamel, however, enamel extension rates in deciduous cuspal enamel were notably lower. The variability of both prenatal and postnatal deciduous enamel formation times was greater than previously reported.