This study aimed to evaluate dental adhesives containing different concentrations of zinc oxide nanoparticles (ZnO-NPs) for their use in the treatment of dental fluorosis, observe the interaction of the adhesive on healthy enamel surfaces and with mild and moderate fluorosis, measure the adhesive strength and fluorosis, and determine the phosphorus (P) and calcium (Ca) content on these surfaces, as a reference for the potential use of this adhesive with ZnO-NPs for dental fluorosis treatment. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were used to characterise the ZnO-NPs and analyse the weight percentages of P and Ca in the enamel using X-ray energy dispersive spectroscopy (EDS) and the adhesive strength using a universal mechanical testing machine. FESEM characterisation revealed that the ZnO-NPs were less than 100 nm in size, with quasi-spherical and hexagonal prism shapes. The synthesis of the ZnO-NPs was confirmed by TEM, revealing their hexagonal crystalline structure. The adhesive strength by the universal mechanical testing machine showed that the adhesive with a 3% wt. concentration of ZnO-NPs was better in the three groups of teeth, showing higher adhesive strength in teeth with mild (15.15 MPa) and moderate (12.76 MPa) fluorosis surfaces, and was even higher than that in healthy teeth (9.65 MPa). EDS analysis showed that teeth with mild and moderate fluorosis had the highest weight percentages of P and Ca, but there were no statistically significant differences compared to healthy teeth and teeth treated with adhesives. Lay description: This study focused on testing a new dental adhesive containing small particles called ZnO nanoparticles (ZnO-NPs). This study aimed to demonstrate whether this adhesive with ZnO-NPs could be useful for treating dental fluorosis by improving its adhesion to teeth. One of the first objectives was to determine whether the dental adhesive could adhere better to teeth affected by mild or moderate fluorosis than to healthy teeth by measuring whether the levels of two important elements for healthy teeth, calcium (Ca) and phosphorus (P), were affected by the adhesive. The size and shape of the small particles and teeth with mild or moderate fluorosis were observed using scanning electron microscopy. The nanoparticles were small (< 100 nm) and had specific quasi-spherical and hexagonal prismatic shapes. More damage to the enamel was observed in teeth with mild or moderate fluorosis than in healthy teeth. The adhesive strength test demonstrated that the dental adhesive with 3% ZnO-NPs had the best adhesion on all healthy conditions of teeth. It was particularly effective in teeth with mild or moderate fluorosis. Finally, the evaluation of the levels of P and Ca on the enamel showed that teeth with fluorosis had higher levels of these elements, but using the dental adhesive with ZnO-NPs did not change the levels of these elements significantly because the adhesive avoided greater detachment because of greater adhesion to these surfaces. In conclusion, adding these small particles to dental adhesives could be an option for treating teeth affected by fluorosis. It stuck well and did not affect the levels of the important elements in the teeth.

Keywords: ZnO nanoparticles; adhesion; dental fluorosis; electron microscopy; green synthesis.

© 2024 The Author(s). Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.

这项研究旨在评估含不同浓度氧化锌纳米颗粒（ZnO-NPs）的牙科粘合剂在治疗牙齿氟斑病中的应用，观察粘合剂在健康牙釉质表面以及轻度和中度氟斑病表面的作用效果，测量粘合强度及氟斑程度，并确定这些表面上磷（P）和钙（Ca）含量作为参考，以评估这种含ZnO-NPs的粘合剂用于治疗牙齿氟斑病的可能性。使用透射电子显微镜（TEM）和场发射扫描电子显微镜（FESEM）对ZnO-NPs进行表征，并通过X射线能量散射光谱（EDS）测量牙釉质中P和Ca的重量百分比，以及使用万能机械测试机测定粘合强度。FESEM 表征显示 ZnO-NPs 小于 100 nm，在准球形和六角棱柱形状之间变化。TEM 确认了 ZnO-NPs 的合成，并揭示其具有六方晶体结构。通过万能机械测试机测定粘合强度表明，含3%重量浓度的ZnO-NPs的粘合剂在三个牙齿组中的性能更佳，在轻度（15.15 MPa）和中度（12.76 MPa）氟斑病表面显示出更高的粘合强度，并且甚至高于健康牙釉质的粘合强度（9.65 MPa）。EDS 分析显示，轻度和中度氟斑病牙齿具有最高的P和Ca重量百分比，但与健康牙齿及使用粘合剂处理后的牙齿相比并无统计学显著差异。

通俗描述：这项研究关注测试一种含有名为ZnO纳米颗粒（ZnO-NPs）的新型牙科粘合剂。本研究旨在证明这种含ZnO-NPs的粘合剂是否有助于治疗氟斑病，通过提高其与患轻度或中度氟斑病牙齿的附着性来实现。其中一个目标是确定该牙科粘合剂是否比在健康牙齿上更好地附着于受轻度或中度氟斑病影响的牙齿，并测量对维持健康牙齿所必需的两种重要元素——钙（Ca）和磷（P）水平的影响情况。通过扫描电子显微镜观察了这些小颗粒以及轻度或中度氟斑病牙齿的大小与形状。纳米颗粒非常小（< 100 nm），具有特定准球形及六角棱柱状结构。在受轻度或中度氟斑病影响的牙齿上发现有更多对牙釉质的损伤，相比健康牙齿而言。粘合强度测试表明含3% ZnO-NPs的牙科粘合剂在所有健康条件下都具有最佳附着力，在患轻度或中度氟斑病的牙齿表面表现尤为出色。最后，评估了牙釉质上的P和Ca水平显示，受氟斑病影响的牙齿有更高的这些元素含量，但使用含ZnO-NPs的粘合剂并没有显著改变这些元素的水平，因为该粘合剂避免了更大程度的脱落从而提高了附着力。总之，将这种小颗粒添加到牙科粘合剂中可能是治疗受氟斑病影响的牙齿的一种选择。它附着良好且未对牙齿中的重要元素含量产生影响。

关键词：ZnO纳米颗粒；粘合性；牙齿氟斑病；电子显微镜；绿色合成。