美国西北大学Derk Joester研究小组在研究中取得进展。他们揭示了人类牙釉质微晶中的化学梯度。这一研究成果在线发表在2020年7月1日的《自然》上。
使用原子级定量成像和相关光谱学，研究人员发现羟基磷灰石（Ca5（PO4）3（OH））的纳米级微晶是釉质的基本组成部分，它包含两个富含镁的纳米层，侧翼是富含钠、氟和碳酸根离子的核。该三明治芯被具有较低替代缺陷浓度的壳包围。基于密度泛函理论计算和X射线衍射数据模型预测，研究发现残余应力是由化学梯度产生的，这与微晶核在酸性介质中优先溶解相一致。
此外，应力可能会影响釉质的机械弹性。这两个额外的层次结构提示了一种可能的新模型，用于在牙釉质形成过程中对晶体生长进行生物学控制，并暗示了牙齿发育过程中生物标记物的保存意义。
研究人员表示，牙釉质是牙齿的主要组成部分，经过数多年进化，其已经能承受很大的咀嚼力、抗机械疲劳并能适应磨损。由发育缺陷或蛀牙（龋齿）引起的功能受损和牙釉质损失影响健康和生活质量，并给社会带来相关的问题。尽管在过去的十年中，人们对牙釉质的形成（牙釉质生成）和成熟牙釉质的功能特性有了一定的了解，但尝试修复这种损伤或在体外合成这种材料却只取得了有限的进展。部分原因是釉质的高度分层结构以及化学梯度引起的其他复杂性。
附：英文原文
Title: Chemical gradients in human enamel crystallites
Author: Karen A. DeRocher, Paul J. M. Smeets, Berit H. Goodge, Michael J. Zachman, Prasanna V. Balachandran, Linus Stegbauer, Michael J. Cohen, Lyle M. Gordon, James M. Rondinelli, Lena F. Kourkoutis, Derk Joester
Issue&Volume: 2020-07-01
Abstract: Dental enamel is a principal component of teeth1, and has evolved to bear large chewing forces, resist mechanical fatigue and withstand wear over decades2. Functional impairment and loss of dental enamel, caused by developmental defects or tooth decay (caries), affect health and quality of life, with associated costs to society3. Although the past decade has seen progress in our understanding of enamel formation (amelogenesis) and the functional properties of mature enamel, attempts to repair lesions in this material or to synthesize it in vitro have had limited success4,5,6. This is partly due to the highly hierarchical structure of enamel and additional complexities arising from chemical gradients7,8,9. Here we show, using atomic-scale quantitative imaging and correlative spectroscopies, that the nanoscale crystallites of hydroxylapatite (Ca5(PO4)3(OH)), which are the fundamental building blocks of enamel, comprise two nanometric layers enriched in magnesium flanking a core rich in sodium, fluoride and carbonate ions; this sandwich core is surrounded by a shell with lower concentration of substitutional defects. A mechanical model based on density functional theory calculations and X-ray diffraction data predicts that residual stresses arise because of the chemical gradients, in agreement with preferential dissolution of the crystallite core in acidic media. Furthermore, stresses may affect the mechanical resilience of enamel. The two additional layers of hierarchy suggest a possible new model for biological control over crystal growth during amelogenesis, and hint at implications for the preservation of biomarkers during tooth development.
DOI: 10.1038/s41586-020-2433-3
Source: https://www.nature.com/articles/s41586-020-2433-3
Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
官方网址：http://www.nature.com/
投稿链接：http://www.nature.com/authors/submit_manuscript.html
本期文章：《自然》：Online/在线发表
