Dental erosion is a widespread dental hard tissue disease, characterized by tooth surface dissolution caused by non-bacterial acids [1]. The main causes of dental erosion are the extrinsic acids from excessive consumption of acidic beverages or intrinsic acids induced by regurgitating or vomiting [2], [3], [4]. The global prevalence ranges from 30 % to 50 % in primary dentition and 20 % to 45 % in permanent dentition [5]. The incidence of dental erosion has drastically increased in children and adults in recent years [1,6].

As the hard tissue loss caused by dental erosion is irreversible and treatment for it can be complex, preventive measures should be taken in the early stages of the disease [2,7]. Unfortunately, most dental erosion patients remain asymptomatic and lack patient awareness until the disease progresses to an advanced stage [7]. Advanced dental erosion leads to loss of tooth structure, dentin hypersensitivity, loss of masticatory function and poor aesthetics [2,7]. In addition, the restorative treatments for advanced dental erosion could be expensive, challenging, and complex [6,7]. Therefore, developing cost-effective preventive strategies to prevent dental erosion is imperative [2,6].

Fluoride is currently the most common topical anti-erosive agent [6,8]. Fluoride can be classified as conventional monovalent fluoride and polyvalent fluoride [6,9,10]. Fluoride prevents dental erosion by forming a protective layer and modifies hydroxyapatite into fluorapatite on the tooth surface [8], [9], [10]. Furthermore, the fluoride modifies proteins in salivary pellicle and increases the thickness of an electron-dense basal layer in the salivary pellicle [9,11,12]. However, the protective effects of fluoride on dental erosion are inconsistent and inconclusive [6,13]. There is also controversy about conventional monovalent fluoride as an anti-erosive agent due to its short retention time after application, instability, and low bioavailability in the oral cavity [13,14].

Silver diamine fluoride (SDF) is a polyvalent fluoride with metal cations that can potentially prevent dental erosion [8,15]. The World Health Organization listed SDF as essential medicines that is safe and effective for oral disease treatment [16]. The commonly used 38 % SDF solution contains a fluoride concentration of 44,800 ppm and a silver concentration of 253,900 ppm [8,17,18]. Previous studies found SDF induced the formation of a protective barrier comprised of a calcium fluoride-like layer (CaF2), silver chloride (AgCl) and metallic silver on the tooth surface [15,19]. SDF was also found to react with hydroxyapatite to form fluorapatite crystals and increased enamel microhardness [15,19]. Moreover, SDF is a matrix metalloproteinases (MMPs) inhibitor which maintains a demineralized organic matrix (DOM) to delay dentin erosion [8,20].

Although SDF shows promise as an anti-erosive agent, there is currently limited research on its effectiveness in managing dental erosion [8]. Only a few laboratory studies investigated the protective effect of SDF on dental erosion [19,21]. Ainoosah et al. found that SDF was effective in reducing erosion in bovine enamel [19], while Cunha et al. reported that 10 % SDF inhibited phosphorus release due to erosion in human primary enamel [21]. Moreover, Suresh et al. reported 38 % SDF reduced human primary enamel microhardness loss against pediatric liquid medicament [22]. The enamel in primary teeth is more susceptible to dental erosion due to lessened mineralization and smaller thickness compared to those in permanent teeth [21,22]. None of the previous studies involving human permanent tooth samples. Therefore, this in vitro study aimed to evaluate the effectiveness of 38 % SDF solution on preventing dental erosion in the enamel and dentin of human permanent teeth. The null hypothesis is that there are no differences in the preventive effects between SDF and experimental agents (stannous chloride-containing fluoride solution) on dental erosion.