## 4 Discussion  
Fluoride treatment is the gold standard when it comes to caries prevention, and brushing with fluoridated toothpaste is at the core of a sound oral care routine. Much of the effectiveness of fluoride in preventing caries and helping maintain good oral health depends on its capacity to enhance the remineralization of dentin and enamel and subsequently inhibit demineralization due to increased acid resistance [5]. For remineralization to be effective, there should be a net mineral gain in the tooth structure, i.e., the degree of apatite deposition should outweigh the dissolution caused by plaque bacteria. Facilitating the right conditions to remineralize or repair early enamel defects such as sub-surface lesions (\"white spots\") may be complex, as it generally depends on ion diffusion through a more intact surface layer. A key aspect of reversing sub-surface demineralization is thus to clear the acid-producing plaque and allow saliva to contact the surface, which can neutralize the area and provide calcium and phosphate ions. If the saliva is supersaturated with calcium and phosphate, ions may then diffuse back into the lesion and remineralize partially demineralized crystals in a process that is accelerated in the presence of fluoride [26; 27]. To create conditions that favor remineralization, especially in areas subjected to repeated acid challenges or in cases of poor salivary flow, supplementing the saliva and the lesion surface with readily available calcium, phosphate, and fluoride ions is therefore crucial. Application of a successful remineralization therapy may often be sufficient to stop caries progression and repair early lesions, reducing the need for costly and irreversible restorations [26]. As  
Figure 4: SEM images of dentin surfaces and dentin tubules in cross-section: Top panel (**A–C**) shows appearance after treatment with blank formula (no particles); Middle panel (**D–F**) shows appearance after treatment with the ACMP formula; Bottom panel (**G–I**) shows appearance after treatment with the ACMFP formula. The left-hand panel (**A,D,G**) shows surfaces before the acid challenge, and the center panel (**B,E,H**) after the acid challenge. Cross-section images of dentin tubules beneath the treated surface are shown in the right-hand panel (**C,F,I**). such, there is evidently a need for the development of calcium phosphate technologies that can contribute to the remineralization process in an effective way. The ACMFP particles of the current study present an opportunity to deliver a single source vehicle of readily available calcium, phosphate, and fluoride ions for remineralization of carious lesions as well as exposed dentin tubules for the reduction of hypersensitivity. The particles may also be produced in a simple and cost-effective way. The unique spherical shape and sub-micron size of the particles make them especially suitable for dentin tubule occlusion, as they enable deep penetration and mineralization that can resist both abrasion and acid erosion. The prospect of having all key remineralization ions from a single source that is readily converted into fluoride-substituted hydroxyapatite could make products for preventive dentistry more effective and potentially safer, as excessive use of fluoride during tooth development may lead to fluorosis. The potential risk of fluorosis should not deter from the proper use of fluoride, however, as the benefits clearly outweigh the risks [3; 4; 5]. Nevertheless, the current findings demonstrate that the degree of fluoride inclusion in the particles and subsequent fluoride release can be adjusted without altering their characteristic features in terms of morphology and crystallinity (Figures 1 and 2), which effectively allows tailoring of the particles to suit a wide range of applications. The fluoride inclusion may be high to maximize the fluoride release and remineralization potential of the particles, or it can be optimized at a lower level to reduce overall fluoride exposure.