To evaluate the erosion preventive effect of 38 % silver diamine fluoride (SDF) solution in enamel and dentin of human permanent teeth.
Ninety enamel and ninety dentin blocks were prepared from permanent molars and allocated into three groups. Gp-SDF received a one-off application of 38 % SDF solution. Gp-SNF received a one-off application of a solution containing 800 ppm stannous chloride and 500 ppm fluoride. Gp-DW received a one-off application of deionized water. The blocks were submitted to acid challenge at pH 3.2, 2 min, 5 times/day for 7 days. All blocks were immersed in human saliva between cycles for one hour. The crystal characteristics, percentage of surface microhardness loss (%SMHL), surface loss, and elemental analysis and surface morphology were examined by X-ray diffraction (XRD), microhardness test, non-contact profilometry, and energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM), respectively. Data of%SMHL and surface loss were analyzed by one-way ANOVA.
XRD spectra revealed that fluorapatite and silver compounds formed in Gp-SDF, while fluorapatite and stannous compounds formed in Gp-SNF. Gp-DW presented only hydroxyapatite. The median (interquartile range) of%SMHL in Gp-SDF, Gp-SNF and Gp-DW were 27.86(3.66), 43.41(2.45), and 46.40(3.54) in enamel (p< 0.001), and 14.21(1.57), 27.99(1.95), and 33.18(1.73) in dentin, respectively (p < 0.001). The mean (standard deviation, μm) of surface loss of Gp-SDF, Gp-SNF, and Gp-DW were 2.81(0.59), 4.28(0.67), and 4.63(0.64) in enamel (p < 0.001) and 4.13(0.69), 6.04(0.61), and 7.72(0.66) in dentin, respectively (p < 0.001). SEM images exhibited less enamel corruption and more dentinal tubular occlusion in Gp-SDF compared to Gp-SNF and Gp-DW. EDS analysis showed silver was detected in Gp-SDF while stannous was detected in the dentin block of Gp-SNF.
38 % SDF yielded superior results in protecting enamel and dentin blocks from dental erosion compared to SNF and DW.
Topical application of 38 % SDF is effective in preventing dental erosion in human enamel and dentin.

The chitin and chitosan biopolymers are extremely valuable because of their numerous industrial and pharmacological uses. Chitin and chitosan were extracted from the exoskeleton of Periplaneta americana (cockroaches) and termites using various acid and alkali techniques. The extraction process involves an initial demineralization step, during which integument dry powder was subjected to 500 mL (2.07 mol/L) of concentrated HCl at 100 degrees Celsius for 30 min, followed by meticulous rinsing with distilled water to restore the pH to its baseline. Deproteinization was conducted at 80 degrees Celsius using 500 mL (1 mol/L) of NaOH solution, which was repeated for 24 h. A total of 250 mL (0.06 mol/L) of NaOH was added at 100 degrees Celsius for 4 h to obtain chitosan, followed by extensive washing and subsequent drying. FTIR analysis was used to identify the functional groups in Periplaneta americana and termites. The crystallinity of these biopolymers, which have a face-centered cubic structure, was determined by X-ray diffraction analysis. This study assessed the analgesic properties of chitin and chitosan via an acetic-acid-induced writhing test in mice, revealing a significant reduction in writhing behavior following the chitin and chitosan extract. Notably, chitin exhibits the highest degree of analgesic activity compared to chitosan. Both chitin and chitosan show anti-inflammatory effects, with chitosan absorbing proton ions at sites of inflammation, while chitin effectively inhibits ear edema and elicits an analgesic response in mice. Furthermore, the present study revealed antipyretic activity, with termite chitin demonstrating the most significant effect at a concentration of 500 µL/mL, followed by chitosan and chitin at 100 µL/mL. These findings indicate the potential of using chitin and chitosan derived from termites and Periplaneta americana as natural anti-inflammatory compounds, implying prospective uses in anti-inflammatory, antipyretic, and analgesic capabilities.

This study aimed to investigate the antibiofilm and remineralising effects of peptide GAPI on artificial dentin caries. After creating artificial carious lesions, eighty dentine blocks were randomly assigned for treatment twice daily with GAPI (GAPI group) or deionised water (control group). Both groups underwent a 7-day biochemical cycle. Scanning electron microscopy (SEM) showed S. mutans with damaged structures that partially covered the dentine in the GAPI group. The dead-live ratios for the GAPI and control groups were 0.77 ± 0.13 and 0.37 ± 0.09 (p < 0.001). The log colony-forming units for the GAPI and control groups were 7.45 ± 0.32 and 8.74 ± 0.50 (p < 0.001), respectively. The lesion depths for the GAPI and control groups were 151 ± 18 µm and 214 ± 15 µm (p < 0.001), respectively. The mineral losses for the GAPI and control groups were 0.91 ± 0.07 gHAcm-3 and 1.01 ± 0.07 gHAcm-3 (p = 0.01), respectively. The hydrogen-to-amide I ratios for the GAPI and control groups were 2.92 ± 0.82 and 1.83 ± 0.73 (p = 0.014), respectively. SEM micrographs revealed fewer exposed dentine collagen fibres in the GAPI group compared to those in the control group. Furthermore, X-ray diffraction (XRD) patterns indicated that the hydroxyapatite in the GAPI group was more crystallised than that in the control group. This study demonstrated GAPI\'s antibiofilm and remineralising effects on artificial dentin caries.

The in vitro demineralization of bone tissue is used for simulating the osteoporosis related bone loss. This way would be helpful in observations of bone apatite dissolution in microstructural level and may give significant input for understanding crystal-chemistry of bone resorption. In the case of cortical bone, demineralization occurs inhomogeneously, with the formation of a superficial demineralized layer and a transition zone with a gradient of concentration and structural characteristics perpendicular to the reaction advance front. Changes in the microstructural parameters of the bone mineral in this interface zone are of great interest for understanding the resorptive processes in the bone associated with osteoporosis. In this work, the SEM-EDX method was used to estimate the sizes of the demineralized and interface layers in the cortical bone during stepwise demineralization in HCl water solution; the general patterns of changes in the concentrations of Ca, P, and Cl in these layers were established. The calculations of the effective penetration depth of X-rays in diffraction mode for the intact and partially demineralized cortical bone were performed. It is shown that the use of CoKα radiation (instead of the usual CuKα) ensures the depth of probing within the interface zone, which allows to adequately assess the microstructural parameters (crystallite sizes and lattice microdeformations) of altered bioapatite in the zone of its interaction with an acid agent. A nonmonotonic change in the average size of crystallites and microdeformations of the apatite lattice was revealed during acid demineralization of the bone. Using asymmetric XRD geometry, the evidence was obtained that the affected mineral of the transition zone does not contain other crystalline phases except for weakly crystallized apatite. For the first time, the depth-controlled XRD analysis was applied to such a complex (surface-gradient) object as partially demineralized cortical bone. Additionally, we propose a rapid, averaging, and non-destructive method for estimating the depth of the reaction front dividing the demineralized and non-demineralized portions of the bone by XRD. The consistency of XRD and SEM-EDX data on the thickness values of the demineralized layer is shown.

BACKGROUND: Tooth bleaching imparts whitening effects along with adverse effects such as increased tooth sensitivity and enamel surface changes. Herein, we employed optical coherence tomography (OCT), a nondestructive optical detection technique, for evaluation of tooth enamel after treatment with peroxide-based bleaching agents.
METHODS: Fifteen enamel samples were bleached using 38% acidic hydrogen peroxide-based bleach, subjected to OCT scanning, and then cross-sectioned and imaged under polarized light microscopy (PLM) and transverse microradiography (TMR). OCT cross-sectional images were compared with PLM and TMR. The depth and severity of demineralization produced in the bleached enamel were measured by OCT, PLM, and TMR. Comparison between the three techniques was performed using Kruskal-Wallis H non-parametric test and Pearson correlation.
RESULTS: In comparison with PLM and TMR, OCT clearly detected the changes in the enamel surface after hydrogen peroxide bleaching. Significant correlations (p<0.05) were observed in lesion depth between OCT and PLM (r=0.820), OCT and TMR (r=0.822), and TMR and PLM (r=0.861). There was no statistically significant difference in demineralization depth values measured by OCT, PLM, and TMR (p>0.05).
CONCLUSIONS: OCT can allow real-time, non-invasive imaging of artificially bleached tooth models and automatically measure the early changes in the enamel lesion structure upon exposure to hydrogen peroxide-based bleaching agents.

This study investigated the possibility of using ethylenediaminetetraacetic acid functionalized silica nanoparticles (EDTA-SiO2) as a dentin-conditioning agent using etch-and-rinse technique to promote the durability of dentin bonding.
The SiO2-EDTA were synthesized by N- [(3- trimethoxysilyl) propyl] ethylenediamine triacetic acid (EDTA-TMS) and SiO2 (50 nm), then characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The capacity of SiO2-EDTA to chelate calcium ions from dentin was examined by inductively coupled plasma-optic emission spectrometry (ICP-OES). The dentin surfaces conditioned with SiO2-EDTA were detected by field emission scanning electron microscopy (SEM), TEM and microhardness testing. For dentin bonding, dentin surfaces were adopted wet- or dry-bonding technique and bonded with adhesive (AdperTM Single Bond2) and applied composite resin (Filtek Z350) on them. The durability of dentin bonding was evaluated by mircotensile bond strength test, in-situ zymography and nanoleakage testing.
FTIR, TGA and XPS results showed that SiO2-EDTA contained N element and carboxyl groups. SEM, TEM and microhardness results indicated that SiO2-EDTA group created extrafibrillar demineralization and retained more intrafibrillar minerals within dentin surface. In the dentin bonding experiment, SiO2-EDTA group achieved acceptable bond strength, and reduced the activity of matrix metalloproteinase and nanoleakage along bonding interface.
It was possible to generate a feasible dentin conditioning agent (SiO2-EDTA), which could create dentin extrafibrillar demineralization and improve dentin bond durability.
This study introduces a new dentin conditioning scheme based on SiO2-EDTA to create extrafibrillar demineralization for dentin bonding. This strategy has the potential to be used in clinic to promote the life of restoration bonding.

The aim of this study was to design and optimize a cold atmospheric plasma (CAP) device that could be applied in an oral environment and to study its effects on plaque biofilm metabolism and regrowth, as well as microbial flora composition and enamel demineralization.
CAP was obtained through a dielectric barrier discharge device; the optical properties were analyzed using emission spectroscopy. The electrochemical analysis of plasma devices includes voltametric characteristic curves and Lissajous. The Streptococcus mutans (UA159) and saliva biofilms were treated in vitro, and the effects of CAP on biofilm metabolism were investigated using MTT and lactate dehydrogenase assays. The duration of antibacterial activity on biofilms was examined, scanning electron microscopy was used to observe the morphology of biofilms, and 16S rRNA sequencing was used to explore the influence of CAP on the microbial flora composition of saliva biofilms. An in vitro model of biofilm-enamel demineralization was designed, and the effect of CAP on enamel demineralization was evaluated by micro surface hardness and micro-CT analysis.
CAP had antibacterial proliferative ability toward Streptococcus mutans biofilms and saliva biofilms and was stronger than ultraviolet under the same tested conditions. After 24 h, the antibacterial effect disappeared, which proved the short-term timeliness of its bactericidal ability. CAP can inhibit the acid production of biofilms, and its inhibitory effect on saliva biofilms can be extended to 24 h. CAP had a strong ability to regulate the composition of plaque biofilms, especially for Lactococcus proliferation, a major acid-producing bacterium in microcosm biofilms. The CAP-treated enamels were more acid-tolerant than non-treated controls.
CAP had an explicit bactericidal effect on caries-related biofilms, which is a short-term antibacterial effect. It can inhibit the acid production of biofilms and has a downregulation effect on Lactococcus in saliva biofilms. CAP can help reduce demineralization of enamel.

OBJECTIVE: Dental caries is the most common chronic disease in humans, caused by the acid produced by the microflora in the mouth that dissolves the enamel minerals. Bioactive glass (BAG) has been used in various clinical applications due to its unique bioactive properties, such as bone graft substitutes and dental restorative composites. In this study, we introduce a novel bioactive glass-ceramic (NBGC) prepared through a sol-gel process under a water-free condition.
METHODS: The anti-demineralization and remineralization effects of NBGC were evaluated by comparing the measurements of bovine enamel surface morphology, surface roughness, surface micro-hardness, enamel elements, and mineral content before and after related treatments with a commercial BAG. The antibacterial effect was characterized by minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC).
RESULTS: Results showed that NBGC had greater acid resistance and remineralization potential compared to commercial BAG. The fast formation of a hydroxy carbonate apatite (HCA) layer suggests efficient bioactivity.
CONCLUSIONS: In addition to its antibacterial properties, NBGC shows promise as an ingredient in oral care products that can prevent demineralization and restore enamel.

Dental caries represents one of the most prevalent diseases worldwide, characteristic of the growth of dental plaque and demineralization of tooth enamel. Current medications for eradication of dental plaques and prevention of demineralization suffer from several limitations to overcome, calling for novel strategies with great potency in eliminating cariogenic bacteria and dental plaque that forms, as well as in inhibiting the demineralization of enamel, into an integrated system. Considering the potency of photodynamic therapy in bacteria inactivation and the composition of enamel, we herein report that the novel photodynamic nano hydroxyapatite (nHAP), named Ce6 @QCS/nHAP, was useful for this purpose. Ce6 @QCS/nHAP, comprised of quaternary chitosan (QCS)-coated nHAP loaded with chlorin e6 (Ce6), exhibited good biocompatibility and non-compromised photodynamic activity. In vitro studies revealed that Ce6 @QCS/nHAP could effectively associate with cariogenic Streptococcus mutans (S. mutans), leading to a significant antibacterial effect through photodynamic killing and physical inactivation against the planktonic microbe. Three-dimensional fluorescence imaging suggested that Ce6 @QCS/nHAP exhibited a superior S. mutans biofilm penetration capacity to free Ce6, resulting in effective dental plaque eradiation when light irradiation was applied. The number of surviving bacteria in biofilm was at least 2.8 log units lower in the Ce6 @QCS/nHAP group compared to that in the free Ce6 group. Further, in the S. mutans biofilm-infected artificial tooth model, treatment with Ce6 @QCS/nHAP also resulted in the significant prevention of hydroxyapatite disks from demineralization, with lower percentage of fragmentation and weight loss These data suggest that our photodynamic nanosystem can effectively eradicate dental plaque while also significantly protecting artificial tooth from demineralization, opening up new possibilities in treating bacterium-associated dental caries.

OBJECTIVE: To investigate the effects of novel bioactive glasses (BG) including PSC with high phosphorus component and FBG with fluorine-doped element on promoting remineralization of artificial dentin caries.
METHODS: (1) BGs were used in this study as follows: PSC (10.8%P2O5-54.2%SiO2-35.0%CaO, mol.%) were synthesized using phytic acid as the phosphorus precursor through sol-gel method. FBG (6.1%P2O5-37.0%SiO2-53.9%CaO-3.0%CaF2, mol.%) and 45S5(6.0%P2O5-45.0%SiO2-24.5%CaO-24.5%Na2O, mol.%) were synthesized by traditional melt method. (2) The above BGs were soaked in simulated body fluid (SBF) for 24 hours. Then X-ray diffraction (XRD) was used to analyze the formation of hydroxyapatite (HA) crystals. (3) Prepared 1 mm thick dentin slices were soaked in 17% ethylene diamine tetraacetic acid (EDTA) for 1 week to demineralize the dentin. Then the dentin slices treated by BG were soaked in SBF for 1 week. Field emission scanning electron micro-scopy (FE-SEM) was used to observe the surface morphology of the dentin slices. (4) Four cavities were prepared to 1 mm depth in each 2 mm thick dentin slice, then were treated with lactic acid for 2 weeks to form the artificial dentin caries. Wax, mineral trioxide aggregate (MTA), PSC and FBG were used to fill four cavities as blank control group, MTA group, PSC group and FBG group respectively. Then the spe-cimens were soaked in SBF for 4 weeks. The changes of depth and density of demineralized dentin were analyzed using Micro-CT before filling and after 2 and 4 weeks filling.
RESULTS: (1) PSC and FBG promoted mineral formation on the surfaces of the demineralized dentin. And the speed was faster and crystallinity was higher in PSC group than the FBG and 45S5 groups. (2) The increased mineral density of artificial dentin caries in PSC group were (185.98 ± 55.66) mg/cm3 and (213.64 ± 36.01) mg/cm3 2 and 4 weeks after filling respectively, which were significantly higher than the control group [(20.38 ± 7.55) mg/cm3, P=0.006; (36.46 ± 10.79) mg/cm3, P=0.001]. At meanwhile, PSC group was also higher than MTA group [(57.29 ± 10.09) mg/cm3; (111.02 ± 22.06) mg/cm3], and it had statistical difference (P=0.015; P=0.006). The depth of remineralized dentin in PSC group were (40.0 ± 16.9) μm and (54.5 ± 17.8) μm 2 and 4 weeks respectively, which were also statistically different from the control group (P =0.010;P=0.001). There were no statistical differences between the control group and MTA group. The above effects of FBG group were between PSC and MTA.
CONCLUSIONS: PSC has advantages in the speed, quality and depth of mineral deposition in the demineralized layer of artificial dentin caries. It would be expected to be an ideal material to promote the remineralization of dentin caries.