Pyne Alice, Marks Will, M Picco Loren, G Dunton Peter, Ulcinas Arturas, E Barbour Michele, B Jones Siân, Gimzewski James, J Miles Mervyn
H.H. Wills Physics Laboratory, University of Bristol, UK.
Arch Histol Cytol. 2009;72(4-5):209-15. doi: 10.1679/aohc.72.209.
High-speed atomic force microscopy (HS AFM) in 'contact' mode was used to image at video rate the surfaces of both calcium hydroxyapatite samples, often used as artificial dental enamel in such experiments, and polished actual bovine dental enamel in both neutral and acidic aqueous environments. The image in each frame of the video of the sample was a few micrometers square, and the high-speed scan window was panned across the sample in real time to examine larger areas. Conventional AFM images of the same regions of the sample were also recorded before and after high-speed imaging. The ability of HS AFM to follow processes occurring in liquid on the timescale of a few seconds was employed to study the dissolution process of both hydroxyapatite and bovine enamel under acidic conditions. Buffered citric acid at pH values between 3.0 and 4.0 was observed to dissolve the surface layers of these samples. The movies recorded showed rapid dissolution of the bovine enamel in particular, which proceeded until the relatively small amount of acid available had been exhausted. A comparison was made with enamel samples that had been treated in fluoride solution (1 h in 300 ppm NaF, pH 7) prior to addition of the acid; the speed of dissolution for these samples was much less than that of the untreated samples. The HS AFM used an in-house designed and constructed high-speed flexure scan stage employing a push-pull piezo actuator arrangement. The HS AFM is able to follow the large changes in height (on the micrometer scale) that occur during the dissolution process.
在“接触”模式下，高速原子力显微镜（HS AFM）以视频速率对两种羟基磷灰石样品的表面进行成像，在这类实验中，羟基磷灰石样品常被用作人工牙釉质，同时还对处于中性和酸性水环境中的经过抛光的实际牛牙釉质进行成像。样品视频每一帧中的图像为几平方微米，高速扫描窗口实时扫过样品以检查更大区域。在高速成像前后，还记录了样品相同区域的传统原子力显微镜图像。利用HS AFM在几秒时间尺度上追踪液体中发生的过程的能力，研究了酸性条件下羟基磷灰石和牛牙釉质的溶解过程。观察到pH值在3.0至4.0之间的柠檬酸缓冲液会溶解这些样品的表层。所记录的视频显示，尤其是牛牙釉质的溶解速度很快，一直持续到可用的相对少量的酸耗尽。将其与在添加酸之前在氟化物溶液（300 ppm NaF，pH 7，处理1小时）中处理过的牙釉质样品进行了比较；这些样品的溶解速度远低于未处理的样品。HS AFM使用了内部设计和构建的高速挠曲扫描台，采用推挽式压电致动器装置。HS AFM能够追踪溶解过程中发生的高度上的大幅变化（微米尺度）。
