Photobiomodulation Reduces the Cytokine Storm Syndrome Associated with COVID-19 in the Zebrafish Model.

Although the exact mechanism of the pathogenesis of coronavirus SARS-CoV-2 (COVID-19) is not fully understood, oxidative stress and the release of pro-inflammatory cytokines have been highlighted as playing a vital role in the pathogenesis of the disease. In this sense, alternative treatments are needed to reduce the level of inflammation caused by COVID-19. Therefore, this study aimed to investigate the potential effect of red photobiomodulation (PBM) as an attractive therapy to downregulate the cytokine storm caused by COVID-19 in a zebrafish model. RT-qPCR analyses and protein-protein interaction prediction among SARS-CoV-2 and Danio rerio proteins showed that recombinant Spike protein (rSpike) was responsible for generating systemic inflammatory processes with significantly increased levels of pro-inflammatory (il1b, il6, tnfa, and nfkbiab), oxidative stress (romo1) and energy metabolism (slc2a1a and coa1) mRNA markers, with a pattern similar to those observed in COVID-19 cases in humans. On the other hand, PBM treatment was able to decrease the mRNA levels of these pro-inflammatory and oxidative stress markers compared with rSpike in various tissues, promoting an anti-inflammatory response. Conversely, PBM promotes cellular and tissue repair of injured tissues and significantly increases the survival rate of rSpike-inoculated individuals. Additionally, metabolomics analysis showed that the most-impacted metabolic pathways between PBM and the rSpike treated groups were related to steroid metabolism, immune system, and lipid metabolism. Together, our findings suggest that the inflammatory process is an incisive feature of COVID-19 and red PBM can be used as a novel therapeutic agent for COVID-19 by regulating the inflammatory response. Nevertheless, the need for more clinical trials remains, and there is a significant gap to overcome before clinical trials can commence.

Effect of chitosan solutions with or without fluoride on the protection against dentin erosion in vitro.

The aim of this study was to assess the protective effect of experimental solutions containing chitosan at different viscosities with or without fluoride (TiF4 /NaF) on dentin loss in vitro. Bovine dentin samples (n = 15) were prepared and allocated to one of the following treatments: (i) 0.5% chitosan (500 mPas); (ii) 0.5% chitosan (2,000 mPas); (iii) 0.042% NaF and 0.049% TiF4 ; (iv) as (iii) with addition of 0.5% chitosan (500 mPas); (v) as (iii) with addition of 0.5% chitosan (2,000 mPas); (vi) commercial solution with SnCl2 /AmF/NaF (positive control); or (vii) deionized water (negative control). The samples were submitted to pH cycling for 7 d (0.1% citric acid, 4 × 90 s d-1 ). The treatment was applied once a day for 30 s. The dentin loss was quantified using a contact profilometer. Three samples per group were evaluated using scanning electron microscopy. The dentin loss (µm) was submitted to anova and Tukey's test for differences between treatments. Among the treatments tested, only chitosan 500 mPas was able to statistically significantly reduce the dentin loss compared to the negative control, being similar to the positive control. TiF4 /NaF, whether with or without chitosan, had no protective effect. Chitosan 500 mPas and SnCl2 /AmF/NaF solutions have comparable protective effect against dentin erosion in vitro.

Mechanism of Action of TiF4 on Dental Enamel Surface: SEM/EDX, KOH-Soluble F, and X-Ray Diffraction Analysis.

This in vitro study aimed to evaluate the action of TiF4 on sound and carious bovine and human enamel. Sound (S) and pre-demineralised (DE) bovine and human (primary and permanent) enamel samples were treated with TiF4 (pH 1.0) or NaF varnishes (pH 5.0), containing 0.95, 1.95, or 2.45% F for 12 h. The enamel surfaces were analysed using SEM-EDX (scanning electron microscopy/energy-dispersive X-ray spectroscopy) (n = 10, 5 S and 5 DE) and KOH-soluble fluoride was quantified (n = 20, 10 S and 10 DE). Hydroxyapatite powder produced by precipitation method was treated with the corresponding fluoride solutions for 1 min (n = 2). The formed compounds were detected using X-ray diffraction (XRD). All TiF4 varnishes produced a coating layer rich in Ti and F on all types of enamel surface, with micro-cracks in its extension. TiF4 (1.95 and 2.45% F) provided higher fluoride deposition than NaF, especially for bovine enamel (p < 0.0001). It also induced a higher fluoride deposition on DE samples compared to S samples (p < 0.0001), except for primary enamel. The Ti content was higher for bovine and human primary enamel than human permanent enamel, with some differences between S and DE. The XRD analysis showed that TiF4 induced the formation of new compounds such as CaF2, TiO2, and Ti(HPO4)2·H2O. In conclusion, TiF4 (>0.95% F) interacts better, when compared to NaF, with bovine and human primary enamel than with human permanent enamel. TiF4 provoked higher F deposition compared to NaF. Carious enamel showed higher F uptake than sound enamel by TiF4 application, while Ti uptake was dependent on the enamel condition and origin.

Effect of an Experimental Paste with Hydroxyapatite Nanoparticles and Fluoride on Dental Demineralisation and Remineralisation in situ.

This study evaluated the effect of an experimental paste containing hydroxyapatite in nanoparticles (nano-HA)/fluoride on dental de-remineralisation in situ. Thirteen subjects took part in this crossover/randomised/double-blind study performed in 4 phases (14 days each). Four sound and 4 pre-demineralised specimens were worn intraorally at each phase corresponding to the following treatments: Nanop Plus (10% HA, 0.2% NaF, nano-HA/fluoride), MI Paste Plus (casein phosphopeptide-amorphous calcium phosphate, 0.2% NaF), F (0.2% NaF) and placebo. Two-hundred and forty enamel and 240 dentine specimens were selected by using surface microhardness; half of them were subjected to pre-demineralisation and the other half remained sound. Sound specimens were further exposed to severe cariogenic challenge (20% sucrose in biofilm) in situ, while pre-demineralised specimens were not. All specimens were exposed to fluoride dentifrice slurry 2×1 min/day. Thereafter, the treatments were done for 4 min. The de-remineralisation was quantified by transversal microradiography. The data were statistically analysed by repeated-measures ANOVA/Tukey's tests (p<0.05). Generally, no huge differences were found among the treatments. However, Nanop Plus was the only treatment able to significantly reduce dentine demineralisation (x0394;Z, integrated mineral loss) and to improve enamel remineralisation (x0394;x0394;Z, integrated mineral uptake) compared to placebo. No treatments were able to reduce enamel demineralisation, while for dentine remineralisation all treatments were similarly effective in improving x0394;x0394;Z compared to placebo. Nanop Plus seems to have a positive influence on dental de-remineralisation, which should be further confirmed.

Impact of experimental nano-HAP pastes on bovine enamel and dentin submitted to a pH cycling model.

This in vitro study evaluated the preventive potential of experimental pastes containing 10% and 20% hydroxyapatite nanoparticles (Nano-HAP), with or without fluoride, on dental demineralization. Bovine enamel (n=15) and root dentin (n=15) specimens were divided into 9 groups according to their surface hardness: control (without treatment), 20 Nanop paste (20% HAP), 20 Nanop paste plus (20% HAP + 0.2% NaF), 10 Nanop paste (10% HAP), 10 Nanop paste plus (10% HAP + 0.2% NaF), placebo paste (without fluoride and HAP), fluoride paste (0.2% NaF), MI paste (CPP-ACP, casein phosphopeptide-amorphous calcium phosphate), and MI paste plus (CPP-ACP + 0.2% NaF). Both MI pastes were included as commercial control products containing calcium phosphate. The specimens were treated with the pastes twice a day (1 min), before and after demineralization. The specimens were subjected to a pH-cycling model (demineralization-6-8 h/ remineralization-16-18 h a day) for 7 days. The dental subsurface demineralization was analyzed using cross-sectional hardness (kgf/mm 2 , depth 10-220 µm). Data were tested using repeated-measures two-way ANOVA and Bonferroni's test (p<0.05). The only treatment able to reduce the loss of enamel and dentin subsurface hardness was fluoride paste (0.2% NaF), which differed significantly from the control at 30- and 50-µm depth (p<0.0001). The other treatments were not different from each other or compared with the control. The experimental Nanop pastes, regardless of the addition of fluoride, were unable to reduce dental demineralization in vitro.

In situ effect of chewing gum containing CPP-ACP on the mineral precipitation of eroded bovine enamel-a surface hardness analysis.

OBJECTIVES: Stimulation of salivary flow is considered a preventive strategy for dental erosion. Alternatively, products containing calcium phosphate, such as a complex of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), have also been tested against dental erosion. Therefore, this in situ study analyzed the effect of chewing gum containing CPP-ACP on the mineral precipitation of initial bovine enamel erosion lesions. METHODS: Twelve healthy adult subjects wore palatal appliances with two eroded bovine enamel samples. The erosion lesions were produced by immersion in 0.1% citric acid (pH 2.5) for 7 min. During three experimental crossover in situ phases (1 day each), the subjects chewed a type of gum, 3 times for 30 min, in each phase: with CPP-ACP (trident total), without CPP-ACP (trident), and no chewing gum (control). The Knoop surface microhardness was measured at baseline, after erosion in vitro and the mineral precipitation in situ. The differences in the degree of mineral precipitation were analyzed using repeated measures (RM-) ANOVA and post hoc Tukey's test (p<0.05). RESULTS: Significant differences were found among the remineralizing treatments (p<0.0001). Chewing gum (19% of microhardness recovery) improved the mineral precipitation compared to control (10%) and the addition of CPP-ACP into the gum promoted the best mineral precipitation effect (30%). CONCLUSIONS: Under this protocol, CPP-ACP chewing gum improved the mineral precipitation of eroded enamel. CLINICAL SIGNIFICANCE: Since the prevalence of dental erosion is steadily increasing, CPP-ACP chewing gum might be an important strategy to reduce the progression of initial erosion lesions.

Impact of Experimental Nano-HAP Pastes on Bovine Enamel and Dentin Submitted to a pH Cycling Model

This in vitro study evaluated the preventive potential of experimental pastes containing 10% and 20% hydroxyapatite nanoparticles (Nano-HAP), with or without fluoride, on dental demineralization. Bovine enamel (n=15) and root dentin (n=15) specimens were divided into 9 groups according to their surface hardness: control (without treatment), 20 Nanop paste (20% HAP), 20 Nanop paste plus (20% HAP + 0.2% NaF), 10 Nanop paste (10% HAP), 10 Nanop paste plus (10% HAP + 0.2% NaF), placebo paste (without fluoride and HAP), fluoride paste (0.2% NaF), MI paste (CPP-ACP, casein phosphopeptide-amorphous calcium phosphate), and MI paste plus (CPP-ACP + 0.2% NaF). Both MI pastes were included as commercial control products containing calcium phosphate. The specimens were treated with the pastes twice a day (1 min), before and after demineralization. The specimens were subjected to a pH-cycling model (demineralization–6-8 h/ remineralization-16-18 h a day) for 7 days. The dental subsurface demineralization was analyzed using cross-sectional hardness (kgf/mm 2 , depth 10-220 µm). Data were tested using repeated-measures two-way ANOVA and Bonferroni's test (p<0.05). The only treatment able to reduce the loss of enamel and dentin subsurface hardness was fluoride paste (0.2% NaF), which differed significantly from the control at 30- and 50-µm depth (p<0.0001). The other treatments were not different from each other or compared with the control. The experimental Nanop pastes, regardless of the addition of fluoride, were unable to reduce dental demineralization in vitro.

Este estudo in vitro avaliou o potencial de pastas experimentais contendo nanopartículas de hidroxiapatita a 10% e 20% (Nano-HAP), com ou sem fluoreto, na prevenção da desmineralização dentária. Espécimes de esmalte (n=15) e de dentina radicular (n=15) bovinos foram divididos em nove grupos de acordo com o valor de dureza superficial: controle (sem tratamento), pasta Nanop 20 (HAP 20%), pasta Nanop 20 plus (HAP 20% + NaF 0,2%), pasta Nanop 10 (HAP 10%), pasta Nanop 10 plus (HAP 10% + NaF 0,2%), pasta placebo (sem F e HAP), pasta fluoretada (NaF 0,2%), pasta MI (CPP-ACP, fosfopeptídio da caseína-fosfato de cálcio amorfo), e pasta MI plus (CPP-ACP + NaF 0,2%). As duas pastas MI foram inclusas como grupos controles comerciais contendo fosfato de cálcio. Os espécimes foram tratados com as pastas duas vezes ao dia (1 min), antes e após a desmineralização. Os espécimes foram submetidos a um modelo de ciclagem de pH (desmineralização 6-8 h/ remineralização 16-18 h por dia) durante sete dias. A desmineralização dentária de subsuperfície foi avaliada através da dureza longitudinal (kgf/mm 2 , profundidade de 10-220 µm). Os dados foram analisados utilizando ANOVA a dois critérios e teste de Bonferroni (p<0,05). O único tratamento capaz de reduzir a perda da dureza de subsuperfície do esmalte e da dentina foi a pasta fluoretada (NaF 0,2%), a qual diferiu significativamente do controle nas profundidades de 30 e 50 µm da superfície (p<0,0001). Os outros tratamentos não foram diferentes entre si ou quando comparados ao controle. As pastas experimentais Nanop, independentemente da presença de fluoreto, não foram capazes de reduzir a desmineralização dentária in vitro.