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.
Department of Earth Sciences, Centre for Human Evolution Research, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
Arch Oral Biol. 2020 Jun;114:104719. doi: 10.1016/j.archoralbio.2020.104719. Epub 2020 Apr 19.
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.
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.
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).
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.
现在越来越多地在考古学和法医学研究中使用乳齿来确定出生时间，并作为出生前后纳入釉质的微量元素的回溯来源。然而，关于乳齿釉质形成时间可变性的数据很少。我们的目的是使用每日增量标记来估计每日分泌率、产前、产后和总釉质形成的时间，以及在釉质形成过程中发生的釉质覆盖或棱柱和条纹方向的任何变化。
对 81 颗乳齿的纵向磨片进行了研究，使用透射光显微镜进行观察。从 Olympus VS-120 虚拟载玻片扫描系统导入高分辨率数字图像到地理信息系统 (ArcGIS，美国 ESRI) 中，用于对颊侧釉质的线性、角度和面积测量进行定量和统计分析。
接近 EDJ 的釉质分泌每日速率比永久性釉质快（3.23μm/天，SD=0.54）。在牙冠形成过程中，棱柱和条纹角度都向 EDJ 增加。釉质覆盖在牙尖和颈区较低，但在出生后约 150 天达到最大值。平均产前釉质形成时间为 118 天（范围 60-150，SD 29.2，n=24）。总的产后釉质形成时间平均为 319 天（范围 210-420，SD 50.6，n=67）。
每日釉质分泌率与以前对乳齿釉质的研究相比，结果相近，但乳齿牙尖釉质的釉质延伸率明显较低。产前和产后乳齿釉质形成时间的可变性都比以前报道的要大。
