Barnard Petrina, McFarlane Gina, Deter Chris, Loch Carolina, Mahoney Patrick
School of Anthropology and Conservation, University of Kent, Canterbury, UK; School of Chemistry and Forensic Sciences, University of Kent, Canterbury, UK.
School of Anthropology and Conservation, University of Kent, Canterbury, UK.
Arch Oral Biol. 2025 Mar;171:106164. doi: 10.1016/j.archoralbio.2024.106164. Epub 2024 Dec 17.
Enamel laminations are closely spaced incremental lines that run parallel to Retzius lines or the developing enamel surface. Here, the timing of enamel laminations is calculated for naturally exfoliated deciduous molars (n = 111) from three modern-day populations (Aotearoa New Zealand, Britain and Canada).
Teeth were sectioned using standard histological methods and examined using a high-powered microscope. Mean daily secretion rates (DSR) were calculated for the outer enamel of each molar in cuspal, lateral and cervical enamel regions. These DSRs were used to determine the periodicity of enamel growth across laminations in each region. Lamination periodicity was compared between populations and sexes, and within molars to assess the relationship between lamination periodicity and the angle between laminations and the outer surface.
Laminations were present in 57 % of all molars (n = 63 out of n = 111). Their presence did not vary between populations or by sex. A mean two-day periodicity was observed in cuspal and lateral outer enamel sampling regions. A mean one-day periodicity was observed in the cervical outer enamel. The angle of laminations relative to the outermost surface of the enamel was significantly related to the presence of laminations.
A two-day periodicity for laminations indicates that this incremental marking is not a reliable proxy for a circadian 24-hour rhythm in human deciduous molars. The orientation of laminations was similar to Retzius lines but differed to the orientation of cross-striations.
釉质层纹是与芮氏线或发育中的釉质表面平行的紧密排列的增量线。在此，对来自三个现代人群（新西兰、英国和加拿大）的自然脱落的乳牙磨牙（n = 111）的釉质层纹形成时间进行了计算。
采用标准组织学方法对牙齿进行切片，并使用高倍显微镜进行检查。计算每颗磨牙牙尖、侧面和颈部釉质区域外层釉质的平均每日分泌率（DSR）。这些DSR用于确定每个区域跨层纹的釉质生长周期。比较了不同人群和性别的层纹周期，并在磨牙内部进行比较，以评估层纹周期与层纹和外表面之间角度的关系。
所有磨牙中有57%（n = 111中的63颗）存在层纹。其存在在不同人群或性别之间没有差异。在牙尖和侧面外层釉质采样区域观察到平均两天的周期。在颈部外层釉质观察到平均一天的周期。层纹相对于釉质最外表面的角度与层纹的存在显著相关。
层纹的两天周期表明，这种增量标记并非人类乳牙磨牙昼夜24小时节律的可靠替代指标。层纹的方向与芮氏线相似，但与横纹的方向不同。
