# Assessment of Fluoride-Releasing Materials in Remineralization of Adjacent Demineralized Enamel
## 4 Discussion
The null hypothesis of this study was rejected in terms of LD because there was a significant difference in the percentage change in LD of the adjacent demineralized proximal-enamel surface between EQ and FZ and CN and FZ, investigated by using micro-CT. This could be attributed to the presence of soluble fluoride in which ion exchange can readily occur not only on the materials' surface but also possibly at a short distance from the materials. Several studies have proved the ability of enamel adjacent to glass ionomer and alkasite restoration to uptake fluoride and resist demineralization [19; 20; 28; 29; 34]. Furthermore, our study found that CN demonstrated a lesser trend in assisting enamel caries remineralization compared to GICs. These results may be supported by several comparative studies evaluating ion release and the recharge of ion-leaching restorative materials, which discovered that GICs released fluoride ions at a higher rate than CN [35; 36; 37]. On the other hand, a recent study by [PERSON] and [PERSON] in 2022 reported that CN increased the surface microhardness recovery of adjacent enamel caries more than EQ and FZ, respectively [15]. This difference from our results may be because they used a self-cured mode of CN which releases more fluoride ions than the light-cured mode we used. Concurrently, CN provided the highest calcium ion release and the greatest phosphate ion recharge compared to other ion-leaching restorative materials [29; 35]. In this study, SEM-EDX was performed on some specimens to confirm our primary outcome. The SEM images illustrated mineral precipitation on the surfaces of adjacent demineralized enamel. The levels of Ca and P ions on demineralized enamel surfaces reflect the restorative materials' ability to remineralize and promote hydroxyapatite formation on adjacent demineralized enamel lesions. Therefore, the percentage weight of Ca and P ions, along with the Ca/P ratio derived from EDX analysis, supported our MD results. Specifically, the demineralized enamel adjacent to FJ exhibited greater remineralization compared to EQ, CN, and FZ. The higher Ca/P ratio, indicating a greater propensity for mineral uptake in the adjacent demineralized proximal enamel and a reduced risk of secondary caries, has potential implications for the selection of proximal restorative materials. This is particularly important for patients with a high caries risk. Additionally, we observed a similar Ca/P ratio between EQ and CN, which aligns with a previous study [19]. However, the Ca/P ratio for both EQ and CN in our study was lower, which may be attributed to differences in the composition of remineralization and demineralization solutions or the curing method of CN used in our study. The results from Raman mapping may indicate that CN encouraged a high level of fluorapatite precipitation on the adjacent demineralized enamel. This could be attributed to the fact that CN released both fluoride and calcium, which were essential for promoting suitable conditions of fluorapatite precipitation [35; 38]. The release of calcium from CN was also at much higher levels than from FJ and EQ [36; 39]. The high mineralizing potential of CN was also confirmed by previous studies [40; 41; 42]. Furthermore, the Raman spectra exhibited a prominent peak at 960 cm\({}^{-1}\), indicating the presence of the phosphate group. This phosphate is likely derived from the remineralization solution. The limitations of this study include the use of acetic acid to create proximal demineralized enamel lesions, resulting in erosive-like lesions that differ from natural carious lesions and do not typically occur in interproximal areas. Furthermore, this study employed an in vitro design that cannot fully replicate the actual clinical environment of the oral cavity. Consequently, this model may have limited clinical relevance. Additionally, the MD investigation focused only on the deepest part of the demineralized enamel lesion.