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One mechanism of action for the anticaries effect of topical fluoridation is through precipitation of CaF 2 . In this in vitro study energy-dispersive x-ray spectroscopy (EDX) is used as a semiquantitative method to detect enamel fluoride-precipitation under the influence of acidic and neutral pH-value and absence or presence of a salivary pellicle. Crowns of 30 human caries-free third molars were quartered into four specimens and the enamel surface ground flat and polished. Two specimens each were stored in human saliva (120 minutes pellicle formation). Teeth were randomly allocated into 6 treatment groups: NaF_a (experimental acidic sodium fluoride; 12500 ppmF − , pH 4.75); NaF_n (experimental neutral sodium fluoride; 12500 ppmF − , pH 7.0); GB_a (acidic gel base; 0 ppmF − , pH 4.75); GB_n (neutral gel base; 0 ppmF − , pH 7.0); AmF-NaF_a (experimental acidic amine/sodium fluoride; 12500 ppmF − , pH 4.75); EG_a (acidic amine/sodium fluoride; Elmex Geleé, CP-GABA GmbH; 12500 ppmF − , pH 4.75). Each gel was applied for 60 seconds to one specimen with and one specimen without pellicle. Two specimens served as controls (no gel, without/with pellicle). Atomic percent (At%) of O, F, Na, Mg, P, Ca was measured by EDX. ∆At% and Ca/P-ratios were calculated. EDX could semi-quantify superficial enamel fluoride-precipitation. Only specimens treated with acidic fluoride gels showed fluoride-precipitation, a salivary pellicle tended to decrease At%F.

Biofilm formation on the tooth surface is the root cause of dental caries and periodontal diseases. Streptococcus mutans is known to produce biofilm which is one of the primary causes of dental caries. Acid production and acid tolerance along with exopolysaccharide (EPS) formation are major virulence factors of S. mutans biofilm. In the current study, calcium fluoride nanoparticles (CaF 2 -NPs) were evaluated for their effect on the biofilm forming ability of S. mutans in vivo and in vitro. The in vitro studies revealed 89 % and 90 % reduction in biofilm formation and EPS production, respectively. Moreover, acid production and acid tolerance abilities of S. mutans were also reduced considerably in the presence of CaF 2 -NPs. Confocal laser scanning microscopy and transmission electron microscopy images were in accordance with the other results indicating inhibition of biofilm without affecting bacterial viability. The qRT-PCR gene expression analysis showed significant downregulation of various virulence genes ( vicR , gtfC , ftf , spaP , comDE ) associated with biofilm formation. Furthermore, CaF 2 -NPs were found to substantially decrease the caries in treated rat groups as compared to the untreated groups in in vivo studies. Scanning electron micrographs of rat’s teeth further validated our results. These findings suggest that the CaF 2 -NPs may be used as a potential antibiofilm applicant against S. mutans and may be applied as a topical agent to reduce dental caries.

This study evaluated the effect of Er,Cr:YSGG laser irradiation and professional fluoride application on enamel demineralization and on fluoride formation and retention. In a blind in vitro study, 264 human enamel slabs were distributed into 8 groups: G1 – untreated; G2 – treated with acidulated phosphate fluoride gel (APF gel, 1.23% F) for 4 min; G3, G4 and G5 – irradiated with Er,Cr:YSGG at 2.8, 5.6 and 8.5 J/cm 2 , respectively; G6, G7 and G8 – preirradiated with Er,Cr:YSGG at 2.8, 5.6 and 8.5 J/cm 2 , respectively, and subjected to APF gel application. Twenty slabs of each group were submitted to a pH-cycling regimen, and enamel demineralization was evaluated in 10 slabs of each group. In the other 10 slabs, CaF 2 -like material was determined. To evaluate F formed, 10 additional slabs of each group, not subjected to the pH cycling, were submitted to analysis of CaF 2 -like material and fluorapatite, while the other 3 slabs of each group were evaluated by scanning electron microscopy. The F content was also measured in all pH-cycling solutions. Laser at 8.5 J/cm 2 and APF treatment reduced enamel demineralization compared to the control (p < 0.05), but the combination of these treatments was not more efficient than their isolated effect. A higher concentration of retained CaF 2 -like material was found in laser groups followed by APF in comparison with the APF gel treatment group. The findings suggest that laser treatment at 8.5 J/cm 2 was able to decrease hardness loss, even though no additive effect with APF was observed. In addition, laser treatment increased the formation and retention of CaF 2 on dental enamel.

Fluorite (CaF 2 ) leaching and weathering (30 days) were conducted to measure fluoride dissolution in semiarid endemic soil and controlled synthetic solutions, and determining the main chemical species involved in these processes via atomic force microscopy (AFM), X-ray diffraction (XRD) and Scanning electron microscopy (SEM–EDS). Ecological health response in this system was assessed exposing Allium cepa bulbs to 10, 50, 100, 450, 550 and 950 mg CaF 2  kg −1 soil to determine genotoxic damage, protein and systemic fluorine concentrations. Results indicated 3 cycles of passive-active fluorite dissolution enabling fluoride concentrations up to 164 mg L −1 under endemic conditions; however, highest fluoride dissolution was 780 mg L −1 for synthetic sulfates solution. Cyclic behavior was associated with the formation of ultrafine-sized calcite (CaCO 3 )-like compounds. Fluorine concentrations ranged from 5 to 300 mg kg −1 in vegetable tissue. The electrophoretic profiles revealed changes in the protein expression after 7, 15 and 25 days of exposure. Genotoxic damage rate was 50, 82 and 42% for these exposures (950 mg CaF 2  kg −1 soil). The dose‒response curves of the normalized total protein content revealed the kinetics vegetable health damage rates for only 7 and 25 days. This behavior was best adjusted for only 7 days. These findings exhibited characteristics for initial damage and adaptation-recovery stage after 15 days. Environmental implications of these findings were further discussed. Graphical abstract

The anticaries effect of professional fluoride (F) application has been attributed to calcium-fluoride-like deposits (CaF2) formed on enamel, but this has not been clearly demonstrated. We hypothesized that CaF2 formed on plaque-free enamel by F application would reduce enamel demineralization due to the increase of F availability in fluid of subsequently formed plaque. We created distinct levels of CaF2 on enamel to evaluate a dose-response effect. Enamel blocks were mounted in contact with a S. mutans test plaque and used in situ by 10 volunteers. F released to the fluid phase of this substrate (“plaque fluid”) was measured before a cariogenic challenge. “Plaque fluid” F concentration was highly correlated to the enamel CaF2 concentration (r = 0.96, p < 0.001) and to consequent enamel demineralization (r = −0.75, p < 0.001). The results suggest that F released to plaque fluid from CaF2 formed on enamel may play a significant role in the anticaries effect of professionally applied F agents.

This study explored the feasibility of fluoride removal from simulated semiconductor industry wastewater and its recovery as calcium fluoride using fluidized bed crystallization. The continuous reactor showed the best performance (>90% fluoride removal and >95% crystallization efficiency) at a calcium-to-fluoride ratio of 0.6 within the first 40 days of continuous operation. The resulting particle size increased by more than double during this time, along with a 36% increase in the seed bed height, indicating the deposition of CaF2 onto the silica seed. The SEM-EDX analysis showed the size and shape of the crystals formed, along with the presence of a high amount of Ca-F ions. The purity of the CaF2 crystals was determined to be 91.1% though ICP-OES analysis. Following the continuous experiment, different process improvement strategies were explored. The addition of an excess amount of calcium resulted in the removal of an additional 6% of the fluoride; however, compared to this single-stage process, a two-stage approach was found to be a better strategy to achieve a low effluent concentration of fluoride. The fluoride removal reached 94% with this two-stage approach under the optimum conditions of 4 + 1 h HRT combinations and a [Ca2+]/[F−] ratio of 0.55 and 0.7 for the two reactors, respectively. CFD simulation showed the impact of the inlet diameter, bottom-angle shape, and width-to-height ratio of the reactor on the mixing inside the reactor and the possibility of further improvement in the reactor performance by optimizing the FBR configuration.

The goal of this study was to evaluate the effectiveness of the toothpaste Tooth Mousse compared to conventional fluoride-based versions in the prevention of enamel and dentin demineralization. Human enamel and dentin samples (n = 120 each) were exposed to artificial demineralization at pH 4.92. During the demineralization process, the samples in the test groups were periodically treated with Tooth Mousse (TM) containing casein-phosphopeptide -amorphous-calcium-phosphate (CPP-ACP) and Tooth Mousse Plus (TMP) containing amorphous-calcium-fluoride-phosphate (CPP-ACPF) to evaluate their protective properties. Fluoride toothpastes containing 1400 ppm amine fluoride (AmF) and 1450 ppm sodium fluoride (NaF) were applied in the positive control groups. Treatment with distilled water (group C-W) or demineralization without treatment (group C-D) served as negative controls. After the demineralization and treatment process, all samples were cut longitudinally and lesion depths were determined at six locations using polarized light microscopy. In TM/TMP groups (enamel: 80/86 µm, dentin: 153/156 µm) lesion depths were significantly smaller compared to the negative control groups C-W/C-D (enamel: 99/111 µm, dentin: 163/166 µm). However, TM and TMP compared to the positive controls AmF/NaF (enamel: 58/63 µm, dentin: 87/109 µm) showed higher lesion depths. The application of TM/TMP (89%/78%) during demineralization led to a reduced number of severe lesions compared to the negative controls C-W/C-D (100%/95%). In this study we demonstrate that Tooth Mousse is less effective regarding prevention of enamel and dentin demineralization compared to fluoride containing toothpastes.

Secondary caries and biofilm accumulation remain major causes of failure in provisional crowns and restorations, highlighting the need for multifunctional resin coatings with antibacterial and remineralizing capabilities. This study aimed to develop a novel bioactive and antibacterial resin-based surface coating incorporating 10% dimethylaminododecyl methacrylate (DMADDM), 20% nanoparticles of amorphous calcium phosphate (NACP), and/or 20% calcium fluoride nanoparticles (nCaF2) within a urethane dimethacrylate/triethylene glycol divinylbenzyl ether (UDMA/TEG-DVBE) matrix. Coatings were evaluated for degree of conversion (DC), flow, shear bond strength, brushing wear resistance (10,000 cycles), and calcium (Ca), phosphate (PO4), and fluoride (F) ion release up to 70 days. All groups achieved clinically acceptable polymerization, with the lowest DC at 50%. NACP-containing coatings significantly increased shear bond strength to 18.3 ± 2.8 MPa, representing a ~170% increase compared with the experimental control (6.8 ± 2.1 MPa) and exceeding the ISO 10477 minimum threshold of 5 MPa. After brushing simulation, experimental coatings demonstrated low wear depth (0.93–1.19 µm), which was ~40% lower than the commercial control (1.85 ± 0.40 µm). Sustained ion release was achieved for 70 days, with 20% NACP-formula releasing 1.22 mmol/L Ca and 0.90 mmol/L PO4, while the dual NACP–nCaF2 formulation provided simultaneous Ca (0.62 mmol/L) and F (0.33 mmol/L) release. The developed coatings demonstrated promising physicochemical properties, bonding performance, wear resistance, and sustained remineralizing ion release, supporting their potential application as therapeutic surface coatings for provisional restorations.

This paper proposes the use of laser-assisted cutting technology to control the brittle–plastic transition of single-crystal CaF2 through local thermal softening, thereby suppressing its processing anisotropy. Nano-scratch experiments show that heating significantly increases the critical plastic cutting depth of each crystal plane and reduces the inter-plane differences. Based on this, laser-assisted ultra-precision turning was used to fabricate CaF2 optical microcavities with a surface roughness below 10 nm, achieving a maximum quality factor of ~7.79 × 107, and significantly reducing the performance differences among different crystal orientations. The research indicates that this method can effectively promote uniform plastic flow on each crystal plane, providing an effective approach for the high-performance and consistent fabrication of anisotropic brittle optical components.

Fluorite (CaF 2 ) sludge in this research was from a chip-producing industry with a CaF 2 content of about 88%. However, the sludge also contained about 1.82 wt% of sulfur in the form of sulfate which made it unsuitable for reuse as flux in iron smelting. This study focused on desulfurization of the sludge. Na 2 CO 3 and sodium D-gluconate were employed as replacement and chelating reagents respectively to replace sulfate with carbonate or transfer CaSO 4 into calcium D-gluconate. Results showed that, at a solid/liquid ratio of 30 g/L and molar ratio of Na 2 CO 3 :S of 1.2:1, after reaction of 4 h, the S content of CaF 2 sludge decreased from the original 1.82 wt% to around 0.10 wt%. For sodium D-gluconate, the optimal condition is solid/liquid ratio of 30 g/L, molar ratio of 2.0:1, and reaction time of 60 min. A desulfurization efficiency of more than 88.9% was achieved. S contents in the treated sludge dropped to 0.20 wt%. CaF 2 contents after desulfurization reached 95%. Characterization of sludge after desulfurization showed that desulfurization process did not significantly change the physical structure of CaF 2 particles. Results from this research provide two effective methods for potential recycle of CaF 2 sludge.