# Assessment of Fluoride-Releasing Materials in Remineralization of Adjacent Demineralized Enamel
## 4 Discussion  
Dental caries is a process of alternating demineralization and remineralization that results directly from acid challenge from dietary cycles and remineralization from oral saliva. The present in vitro study aimed to mimic the behavior of the oral environment in daily life. pH cycling was utilized as it can provide a sufficient amount of calcium and phosphate ions for remineralization [23], and fluoride-containing toothpaste was regularly used to encourage enamel remineralization. Each day, the restorative materials and the artificially demineralized proximal enamel were subjected to a pH cycling regimen consisting of three dietary cycles, exposure to artificial saliva, and immersion twice in fluoride toothpaste. Fluoride-releasing restorative materials have excellent potential in dental caries prevention. The placement of a proximal restoration in the treatment of dental caries changes the local environment from cariogenic to non-cariogenic, not only for the treated tooth but also for the proximal surface of the adjacent tooth. To enable the exchange of fluoride with the HA of enamel, prolonged fluoride release and close restorative contact with the tooth surfaces are required [24]. In this study, mounting teeth in proximal tight contact emulated a maximum natural contact area. Uncoated GICs were used because the interproximal area cannot be coated in clinical situations, and a study showed that uncoated GICs released more fluoride than coated ones [25]. Furthermore, light-cured CN was used in this study, even though the ability of light-curing alkasite restorative material to release ions has been shown to slightly decrease due to photopolymerization [18]. The present study found that all the materials can reduce the LD of adjacent demineralized proximal enamel, and only fluoride-releasing materials provided a significant reduction in LD compared to their baselines. EQ exhibited a significantly higher percentage reduction in LD than FZ. This result corresponds to previous studies using polarized-light photomicrographs that showed that GICs decreased adjacent enamel LD more than a resin composite [26; 27; 28]. Moreover, our findings demonstrated a comparable percentage reduction in LD between CN and GICs (EQ, F). Additionally, CN exhibited a significantly higher percentage reduction in LD compared to FZ. These results support the findings of [PERSON] et al. and [PERSON] et al., who reported that CN and GICs significantly inhibit the demineralization of enamel caries adjacent to restorations and more effectively reduce lesion depth compared to resin composites [29; 30]. This effect may be due to CN's ability to release fluoride and calcium ions, which assist in the remineralization process [31]. A previous study indicated that CN can continuously release these ions for up to 28 days, at concentrations 300-400 times higher than those found in resin composites [32]. However, FZ also showed a reduced LD. These may be explained by the fluoride toothpaste and artificial saliva we used, containing adequate fluoride, calcium, and phosphate ions that play an important role in enhancing the remineralization process. The baseline MD of adjacent demineralized proximal enamel in our study was approximately 1500 mgHA/cm\({}^{3}\), which is comparable to the values reported by a previously published study [33]. After pH cycling, the MD of these demineralized enamel samples increased significantly in all material groups when compared to their baselines. These results imply that the pH cycling conducted in this study represents a remineralization model, which is also confirmed by our LD results. Although not statistically significant, a greater increase in the percentage change in MD was observed in the fluoride-releasing material groups compared to FZ. In contrast, a previous long-term study demonstrated that GICs had a significantly greater MD change than resin composites [21]. Therefore, a longer experimental period would be suggested.