Physical Properties of Fluorosis Bone: Critical Comments

In 1976 Franke and co-workers reported a study of the physical properties of bone from patients who had been exposed to fluorine for many years.¹ In addition the ash from a rib and an iliac crest was examined and found to contain considerable amounts of fluorine. In the mechanical tests, determinations were made of the fracture load and bending strength of complete bones or parts of bones, and of the fracture load per unit of area and the modulus of elasticity of cylindrical test bodies made from bone specimens.     

Effect of silver and fluoride ions on enamel demineralization: a quantitative study using micro-computed tomography

Background: This study aimed to investigate the effect of silver and fluoride ions on demineralization of enamel. Methods: The coronal parts of 40 extracted sound premolars were prepared into tooth blocks. An unvarnished occlusal surface window (OW) and a flat buccal/lingual surface window (FW) were created for each tooth by covering all other surfaces with an acid‐resistant varnish. These blocks were randomly allocated into four groups of 10 blocks each and immersed in respective solutions for 5 minutes: Group 1 – 2.36 M silver fluoride; Group 2 – 2.36 M potassium fluoride; Group 3 – 2.36 M silver nitrate; and Group 4 – deionized water. After 7‐day immersion in a buffered demineralization solution at pH 4.4, micro‐CT scans were taken. Results: Mean lesion depth in the FW area for tooth blocks in AgF, KF, AgNO₃ and control groups were 0 μm, 3.3 ± 10.3 μm, 156.3 ± 30.8 μm, and 173.6 ± 48.6 μm, respectively (p < 0.001). The difference in mean lesion depth between the AgNO₃ and control groups was not statistically significant (p > 0.05). Similar OW and FW lesions were observed in tooth blocks in the AgNO₃ and control groups. Conclusions: Topical application of a 2.36 M fluoride solution can inhibit demineralization of enamel while topical application of silver ions has little effect.     

Clinical evaluation of diamine silver fluoride/potassium iodide as a dentine desensitizing agent. A pilot study

Background: The aim of the present study was to compare the efficacy of an experimental diamine silver fluoride/potassium iodide product with an oxalic acid‐based preparation in reducing dentine hypersensitivity. Methods: The study was conducted as a double‐blind, randomized clinical trial. A total of 19 subjects with dentine hypersensitivity on both sides of their upper arch were selected. The most sensitive tooth in each quadrant was identified and received a cold stimulus. The response was recorded on a visual analogue scale (VAS). The tooth thus selected was treated with one of the treatment agents. One week later the level of dentine sensitivity was assessed. Participants were also asked for their subjective assessment of treatment effects. Results: The mean difference between VAS at baseline and seven days for teeth treated with diamine silver fluoride/potassium iodide was greater than that for teeth treated with the oxalic acid‐based preparation (p = 0.0134). The subjects’ subjective assessment of changes in dentine hypersensitivity indicated that more obtained relief with the diamine silver fluoride/potassium iodide treatment (p = 0.0129). Conclusions: It was concluded that an experimental diamine silver fluoride/potassium iodide product has potential as a treatment for dentine hypersensitivity.     

Cellular magnesium acquisition: an anomaly in embryonic cation homeostasis

The intracellular dominance of magnesium ion makes clinical assessment difficult despite the critical role of Mg(++) in many key functions of cells and enzymes. There is general consensus that serum Mg(++) levels are not representative of the growing number of conditions for which magnesium is known to be important. There is no consensus method or sample source for testing for clinical purposes. High intracellular Mg(++) in vertebrate embryos results in part from interactions of cations which influence cell membrane transport systems. These are functionally competent from the earliest stages, at least transiently held over from the unfertilized ovum. Kinetic studies with radiotracer cations, osmolar variations, media lacking one or more of the four biological cations, Na(+), Mg(++), K(+), and Ca(++), and metabolic poison 0.05 mEq/L NaF, demonstrated that: (1) all four cations influence the behavior of the others, and (2) energy is required for uptake and efflux on different time scales, some against gradient. Na(+) uptake is energy dependent against an efflux gradient. The rate of K(+) loss is equal with or without fluoride, suggesting a lack of an energy requirement at these stages. Ca(++) efflux took twice as long in the presence of fluoride, likely due in part to intracellular binding. Mg(++) is anomalous in that early teleost vertebrate embryos have an intracellular content exceeding the surrounding sea water, an isolated unaffected yolk compartment, and a clear requirement for energy for both uptake and efflux. The physiological, pathological, and therapeutic roles of magnesium are poorly understood. This will change: (1) when (28)Mg is once again generally available at a reasonable cost for both basic research and clinical assessment, and (2) when serum or plasma levels are determined simultaneously with intracellular values, preferably as part of complete four cation profiles. Atomic absorption spectrophotometry, energy-dispersive x-ray analysis, and inductively coupled plasma emission spectroscopy on sublingual mucosal and peripheral blood samples are potential methods of value for coordinated assessments.     

Neuroprotective effect of gold nanoparticles composites in Parkinson's disease model

Parkinson’s disease (PD) is second most common neurodegenerative disorder worldwide. Although drugs and surgery can relieve the symptoms of PD, these therapies are incapable of fundamentally treating the disease. For PD patients, over-expression of α-synuclein (SNCA) leads to the death of dopaminergic neurons. This process can be prevented by suppressing SNCA over-expression through RNA interference. Here, we successfully synthesized gold nanoparticles (GNP) composites (CTS@GNP-pDNA-NGF) via the combination of electrostatic adsorption and photochemical immobilization, which could load plasmid DNA (pDNA) and target specific cell types. GNP was transfected into cells via endocytosis to inhibiting the apoptosis of PC12 cells and dopaminergic neurons. Simultaneously, GNP composites are also used in PD models in vivo, and it can successfully cross the blood-brain barrier by contents of GNP in the mice brain. In general, all the works demonstrated that GNP composites have good therapeutic effects for PD models in vitro and in vivo.     

The effect of fluoride on the structure,function, and proteome of intestinal epithelia

Fluoride exposure is widespread, with drinking water commonly containing natural and artificially added sources of the ion. Ingested fluoride undergoes absorption across the gastric and intestinal epithelia. Previous studies have reported adverse gastrointestinal effects with high levels of fluoride exposure. Here, we examined the effects of fluoride on the transepithelial ion transport and resistance of three intestinal epithelia. We used the Caco‐2 cell line as a model of human intestinal epithelium, and rat and mouse colonic epithelia for purposes of comparison. Fluoride caused a concentration‐dependent decline in forskolin‐induced Cl^– secretion and transepithelial resistance of Caco‐2 cell monolayers, with an IC₅₀ for fluoride of about 3 mM for both parameters. In the presence of 5 mM fluoride, transepithelial resistance fell exponentially with time, with a t_1/2 of about 7 hours. Subsequent imaging by immunofluorescence and scanning electron microscopy showed structural abnormalities in Caco‐2 cell monolayers exposed to fluoride. The Young's modulus of the epithelium was not affected by fluoride, although proteomic analysis revealed changes in expression of a number of proteins, particularly those involved in cell–cell adhesion. In line with its effects on Caco‐2 cell monolayers, fluoride, at 5 mM, also had profound effects on Cl^– secretion and transepithelial resistance of both rat and mouse colonic epithelia. Our results show that treatment with fluoride has major effects on the structure, function, and proteome of intestinal epithelia, but only at concentrations considerably higher than those likely to be encountered in vivo, when much lower fluoride doses are normally ingested on a chronic basis.     

Plaque and gingivitis in the elderly: a randomized, single-blind clinical trial on the outcome of intensified mechanical or antibacterial oral hygiene measures

OBJECTIVES: To study the outcome of intensified mechanical oral hygiene compared with the effect of an adjunctive antibacterial mouth rinse on plaque and gingivitis in elderly people. MATERIAL AND METHODS: In a randomized, single-blind, 6-month controlled clinical study, 106 subjects, 55 years or older, were divided into four groups: (I) Participants were instructed on improved mechanical oral hygiene, including interdental hygiene; (II) subjects used an antibacterial mouth rinse containing amine and stannous fluoride in addition to their usual oral hygiene practices; (III) both intensive mechanical and antibacterial measures were combined; and (IV) a control group with no specific regimen. Gingivitis and plaque were examined. RESULTS: After 6 months, both plaque and gingivitis scores were significantly lower than at baseline in all groups. Reductions in gingivitis differed significantly between the control group and all other groups but not between the three intervention groups. Only groups with improved mechanical oral hygiene showed significant improvements in plaque scores compared with control. CONCLUSIONS: Intensive mechanical oral hygiene resulted in greater plaque reduction than the combination of an antibacterial rinse and usual oral hygiene procedures. Gingivitis was reduced by both intensive oral hygiene and use of the amine/stannous fluoride rinse. Combining intensive mechanical oral hygiene with the antibacterial rinse did not result in further gingivitis reduction.     

Effect of chlorhexidine/thymol and fluoride varnishes on dental biofilm formation in vitro

This study evaluated the effect of chlorhexidine/thymol (CHX/T) and fluoride (F) varnishes on biofilm formation in vitro. Hydroxyapatite discs coated with varnish were first immersed in saline for 0, 3, 7 or 14 d, then immersed in pasteurized saliva. The discs were incubated for 20 h with a bacterial suspension containing Actinomyces naeslundii, Fusobacterium nucleatum, Streptococcus oralis, and Veillonella dispar. Uncoated discs were used as controls. Growth of bacteria on the discs was evaluated by culture and by scanning electron microscopy (SEM). Bacterial vitality was examined by fluorescence staining. In the CHX/T-treated group, bacterial accumulation was delayed, and the total number of bacteria was significantly lower than in the controls. In the F-treated group, the total number of bacteria did not differ from the control, although the number of S. oralis was lower. Bacterial vitality in the CHX/T and F groups did not differ from that in the controls. The total number of bacteria on the CHX/T-treated discs immersed in saline was significantly higher than that on the non-immersed discs. Biofilm development was inhibited by the CHX/T varnish but not by the F varnish. The effect of the CHX/T varnish decreased following the immersion of discs in saline.     

Effect of sodium fluoride in maternal and offspring rats and its amelioration

High fluoride content is known to cause dental and skeletal abnormalities. In addition, present review indicates that sodium fluoride consumption caused increased number of r=esorptions and dead foetuses. Various skeletal anomalies such as wavy ribs, presence of 14^th ribs, lacking 6^th sternebrae and incompete ossification of skull occur. All these changes could be due to oxidative stress caused by fluoride consumption. Fluoride-induced changes could be successfully ameliorated by cotreatment with vitamins and calcium.