## 3 Results
### General Characteristics of the Included Studies  
The overarching objective of the included studies was to assess the fluoride release capabilities of various dental materials, encompassing glass-ionomer cements [17; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47], resin-based composites [34; 38; 40; 41; 45; 47], giomers [33; 36; 40; 45], bioactive glass [35], and composures [48] under different conditions. These conditions included the application of surface coatings [17; 32; 37; 40; 43; 44; 46; 53], bonding agents [38; 40; 41; 46; 47; 48], fluoride varnishes or concentrated gels [32; 33; 34; 35; 39; 45], nail varnishes [49; 50], and resin liners [51]. Additionally, two studies aimed to assess the reabsorption capabilities and the impact of fluoride release [17; 34]. Methods varied across studies but typically involved preparing in vitro samples of dental materials under study conditions. Twenty-two studies utilized molds [17; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 46; 47; 48; 49; 50; 51; 52; 53], applying different surface coatings, and then immersing them to create an experimental medium in solutions that simulated various oral environments, including the effects of brushing, saliva substitutes, and varying pH levels.  
Various types of solutions were utilized, such as deionized water [17; 32; 34; 35; 37; 38; 39; 41; 43; 46; 48; 49; 51; 52; 53] in eighteen studies, synthetic saliva [33; 39; 47] in three studies, acetate buffer [43; 51] and remineralizing solution [47; 50] in two studies, and lactic acid solution [36], deionized water containing hydroxyapatite [39], maleic acid-KOH buffer [48], 5% sucrose solution [47], and amine fluoride gel [47] in one study each. Techniques for fluoride measurement commonly included the use of ion-selective electrodes [17; 32; 33; 34; 35; 37; 38; 39; 41; 43; 45; 46; 47; 48; 49; 51; 52; 53] in twenty studies, ion analyzers [32; 33; 34; 35; 38; 41; 43; 45; 49; 52] in twelve studies, pH meters [17; 37; 51; 53] in four studies, and gas-liquid chromatography in one study [50]. In twenty-two studies [17; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52], there were hours/days cycles of multiple checkups.  
Notably, in twenty articles [17; 32; 33; 34; 35; 36; 38; 39; 40; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53], the materials were used according to the manufacturer's instructions.  
The results revealed a broad spectrum of fluoride release behaviors influenced by material composition, surface coating, and environmental conditions. Overall, uncoated samples exhibited higher fluoride release compared to coated samples across all cases [17; 32; 33; 34; 35; 32; 36; 37; 38; 39; 50; 51; 52; 53]. Glass-ionomer cements typically exhibited higher fluoride release compared to other materials [33; 34; 38; 40; 41; 46; 49]. Surface coatings, such as varnishes and resins, generally reduced fluoride release, although the extent of reduction varied depending on the material and type of coating. The initial fluoride release was typically higher but decreased over time. Additionally, studies explored fluoride recharging abilities and the impact of external fluoride sources, such as toothpaste and varnish, revealing their potential to enhance fluoride release from dental materials [33; 34] (see Supplementary Table S1).