Hydroxyapatite nanoparticles (nano-HAP) are receiving considerable attention for dental applications, and their adhesion to enamel is well established. However, there are no reports concerning the effects of HAP on other dental materials, and most of the studies in this field are based on in vitro designs, neglecting the salivary pellicle-apatite interactions. Thus, this in situ pilot study aims to evaluate the effects of three hydroxyapatite-based solutions and their interactions with different dental material surfaces under oral conditions. Hence, two volunteers carried intraoral splints with mounted samples from enamel and from three dental materials: titanium, ceramics, and polymethyl-methacrylate (PMMA). Three HAP watery solutions (5%) were prepared with different shapes and sizes of nano-HAP (HAP I, HAP II, HAP III). After 3 min of pellicle formation, 10 ml rinse was performed during 30 sec. Rinsing with water served as control. Samples were accessed immediately after rinsing, 30 min and 2 h after rinsing. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the particles, and SEM evaluated the pellicle-HAP interactions. SEM and TEM results showed a high variation in the size range of the particles applied. A heterogeneous HAP layer was present after 2 h on enamel, titanium, ceramics, and PMMA surfaces under oral conditions. Bridge-like structures were visible between the nano-HAP and the pellicle formed on enamel, titanium, and PMMA surfaces. In conclusion, nano-HAP can adhere not only to enamel but also to artificial dental surfaces under oral conditions. The experiment showed that the acquired pellicle act as a bridge between the nano-HAP and the materials' surface.

中文翻译：

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口腔条件下羟基磷灰石纳米颗粒与牙科材料的粘附

羟基磷灰石纳米颗粒（nano-HAP）在牙科应用中受到了相当大的关注，并且它们对牙釉质的附着力已经很好地建立起来。然而，目前还没有关于HAP对其他牙科材料影响的报道，该领域的研究大多基于体外设计，忽略了唾液薄膜-磷灰石的相互作用。因此，这项原位试点研究旨在评估三种基于羟基磷灰石的溶液的效果及其在口腔条件下与不同牙科材料表面的相互作用。因此，两名志愿者携带口腔内夹板，其中装有来自牙釉质和三种牙科材料的样品：钛、陶瓷和聚甲基丙烯酸甲酯 (PMMA)。制备了具有不同形状和尺寸的纳米 HAP（HAP I、HAP II、HAP III）的三种 HAP 水溶液（5%）。薄膜形成 3 分钟后，在 30 秒内进行 10 毫升冲洗。用水冲洗作为对照。冲洗后立即、冲洗后 30 分钟和 2 小时访问样品。使用扫描电子显微镜 (SEM) 和透射电子显微镜 (TEM) 来表征颗粒，SEM 评估薄膜-HAP 相互作用。SEM 和 TEM 结果显示所应用颗粒的尺寸范围变化很​​大。在口腔条件下，牙釉质、钛、陶瓷和 PMMA 表面 2 小时后会出现异质 HAP 层。在纳米 HAP 和在搪瓷、钛和 PMMA 表面上形成的薄膜之间可以看到桥状结构。总之，纳米HAP不仅可以粘附在牙釉质上，还可以粘附在口腔条件下的人造牙齿表面上。