A moving liver phantom in an anthropomorphic thorax for SPECT MP imaging.

Cranio-caudal respiratory motion and liver activity cause a variety of complex myocardial perfusion (MP) artifacts, especially in the inferior myocardial wall, that may also mask cardiac defects. To assess and characterise such artifacts, an anthropomorphic thorax with moving thoracic phantoms can be utilised in SPECT MP imaging. In this study, a liver phantom was developed and anatomically added into an anthropomorphic phantom that also encloses an ECG beating cardiac phantom and breathing lungs' phantom. A cranio-caudal respiratory motion was also developed for the liver phantom and it was synchronised with the corresponding ones of the other thoracic phantoms. This continuous motion was further divided into isochronous dynamic respiratory phases, from end-exhalation to end-inspiration, to perform SPECT acquisitions in different respiratory phases. The new motions' parameters and settings were measured by mechanical means and also validated in a clinical environment by acquiring CT images and by using two imaging software packages. To demonstrate the new imaging capabilities of the phantom assembly, SPECT/CT MP acquisitions were performed and compared to previous phantom and patients studies. All thoracic phantoms can precisely perform physiological motions within the anthropomorphic thorax. The new capabilities of the phantom assembly allow to perform SPECT/CT MP acquisitions for different cardiac-liver activity ratios and cardiac-liver proximities in supine and, for first time, in prone position. Thus, MP artifacts can be characterised and motion correction can be performed due to these new capabilities. The impact of artifacts and motion correction on defect detection can be also investigated.

Correlation of local lightning activity with extra low frequency detector for Schumann Resonance measurements.

A dedicated extremely low frequency (ELF) detector has been constructed and used successfully for Schumann Resonance (SRs) measurements in N.W. Greece. The main objective of this work was to investigate the effect of local lightning activity on the signal of our ELF detector and consequently on the estimated SRs parameters, namely the power, the frequency and the quality factor of each mode. Therefore, several measurements were taken into account for the ELF signal continuously recorded and the lightning intensity in a specific range around the ELF detector. Additionally, a simple filtering technique was used, in order to reject the distorted SRs spectra. The statistical analysis performed showed a positive and statistically significant correlation between the lightning events and the recorded magnetic component of the ELF signal. It was found that local lightnings have a significant impact on the SRs measurements, and it is necessary to be removed from the background signal.

Assessment of genetic effects and pesticide exposure of farmers in NW Greece.

The present study aims at evaluating potential genotoxic and cytotoxic effects caused by the occupational exposure of farmers to pesticide mixtures in the Aitoloakarnania Prefecture (Greece). The aforementioned assessment was conducted through in vivo Cytokinesis Block Micronucleus assay (CBMN assay) in peripheral blood lymphocytes, in relation to chemical analysis of pesticide residues in blood samples. The exposure of the farmers' population studied to different combinations of pesticides induced significant differences in the frequencies of micronuclei (MN) compared to those of the control group. Furthermore, our results indicated a possible clastogenic and aneugenic effect of pesticides on the genetic material of the farmers exposed. Five pesticides (trifluralin, chlorpyriphos methyl, metolachlor, fenthion and dimethoate) and three metabolites (fenthion sulfone, fenthion sulfoxide and 4,4' DDE) were detected in the 62.5% of blood samples, with mean concentrations ranging from 0.4 ng/ml to 48 ng/ml. Since the farmers studied probably exhibit detectable levels of systematic exposure to the pesticides applied, continuous educational programs focused on the rational and safe use of pesticides, together with implementation of risk communication strategies among farmers are highly recommended.

Study of the variations in the Schumann resonances parameters measured in a southern Mediterranean environment.

Schumann resonances (SRs) provide a unique tool for exploring continuous and long-term monitoring of global environmental parameters, although their detection and study is a very complex task. This paper presents diurnal and seasonal variations of principal parameters, namely the resonance frequency, the Q-factor, and the power of SRs, in the North-South (NS) magnetic field component for the first five modes from Extra Low Frequency (ELF) measurements. These were acquired at the observation site located at Doliana, Kalpaki, in the Region of Epirus, North West Greece. These variations are the first ones reported for the principal parameters in the South Eastern Mediterranean area and correspond to the one-year measurement period from 2016 to 2017. The comparison with variations at several observations sites is also discussed. Moreover, correlation with global lighting centers, as well as local lightning activity, and SRs parameters variation is attempted.

Quantitative light-induced fluorescence to measure enamel remineralization in vitro.

UNLABELLED: The aim of this study was to compare the ability of quantitative light-induced fluorescence (QLF) and surface microhardness (SMH) to measure the remineralization of enamel subsurface lesions, using a pH-cycling model including treatment with 0-ppm, 550-ppm or 1,100-ppm sodium fluoride (NaF) dentifrices. METHODS: Subsurface lesions were created in human enamel specimens (n = 36) and exposed to a remineralization pH-cycling model for 14 days. The pH-cycling model was performed in an automated system where specimens were subjected to a demineralizing solution for 20 min and treatment for 1 min and were then remineralized for 7 h 39 min, 3 times daily. The treatments consisted of 3 NaF, silica-containing dentifrices (0 ppm F; 550 ppm F; 1,100 ppm F). The outcome variables were: change from baseline in surface hardness and percentage change from baseline in fluorescence. An ANCOVA explored differences between different treatment groups (at the p < 0.05 level). Associations between QLF and SMH were evaluated using Spearman's correlation coefficient. RESULTS: The percentage SMH changes were 14.9 ± 2.1%, 56.6 ± 9.6% and 103.9 ± 14.6% for the 0-, 550- and 1,100-ppm F dentifrices, respectively. The percentage fluorescence changes were 15.6 ± 7.1%, 59.8 ± 11.9% and 85 ± 13.2%, respectively. The differences between all pairwise comparisons were statistically significant for both methods (p = 0.001). QLF correlated with SMH (r = 0.67). CONCLUSIONS: Both the SMH and QLF methods demonstrated a significant F dose response for toothpaste in this in vitro remineralization model, and both methods were able to distinguish treatments with different F levels.

In situ clinical effects of new dentifrices containing 1.5% arginine and fluoride on enamel de- and remineralization and plaque metabolism.

OBJECTIVE: The primary objective of the three studies reported in this paper was to evaluate the effects of new dentifrices containing 1.5% arginine, an insoluble calcium compound, and fluoride for their ability to promote remineralization of demineralized enamel, and to prevent mineral loss from sound enamel specimens. A secondary objective was to determine the effects on plaque metabolism with respect to the conversion of arginine to ammonia and sucrose to lactic acid. METHODS: In Study 1, an intraoral remineralization/demineralization clinical model was used to assess the ability to promote remineralization of enamel of two dentifrices containing 1.5% arginine and 1450 ppm fluoride, as sodium monofluorophosphate (MFP), relative to a positive control with dicalcium phosphate dihydrate (Dical) and 1450 ppm fluoride, and a negative control with Dical and 250 ppm fluoride. One of the arginine-containing dentifrices contained Dical, and the other contained calcium carbonate as the source of insoluble calcium. Microradiography and image analysis were used to measure mineral changes. The study used a double-blind crossover design with a two-week treatment period. Each treatment period was preceded by a one-week washout period. Each product was used twice a day for two weeks. In the two other studies, the ability of dentifrices containing 1.5% arginine and fluoride to prevent demineralization of sound enamel blocks was assessed using an intraoral demineralization/remineralization clinical model and a double-blind crossover design with a five-day treatment period. A one-week minimum washout period preceded each treatment phase. Microhardness was used to assess mineral changes. Cariogenic challenges were administered by dipping each intraoral retainer into a 10% sucrose solution four times per day. Each product was used twice per day during the treatment period. Plaque was harvested from the specimens to measure the ability of the plaque to convert arginine to ammonia (Studies 2 and 3) and sucrose to lactic acid (Study 3) at the end of each treatment period. In Study 2, a dentifrice containing 1.5% arginine, Dical, and 1450 ppm fluoride as MFP was compared to a matched positive control containing 1450 ppm fluoride and to a matched negative control containing 250 ppm fluoride. In Study 3, a dentifrice containing 1.5% arginine, calcium carbonate, and 1000 ppm fluoride as MFP was compared to a matched positive control containing 1000 ppm fluoride and to a matched negative control containing 0 ppm fluoride. RESULTS: In Study 1, the percent mineral changes were +18.64, +16.77, +4.08, and -24.95 for the 1.5% arginine/Dical/1450 ppm fluoride, the 1.5% arginine/calcium carbonate/1450 ppm fluoride, the positive control, and negative control dentifrices, respectively. Study validation was successfully achieved by showing that the positive control was statistically significantly better that the negative control in promoting remineralization (p = 0.0001). The two arginine-containing test products were statistically significantly better than the positive control (p < 0.05). No significant difference was observed in efficacy between the two arginine-containing products, indicating that efficacy in promoting remineralization was independent of the choice of Dical or calcium carbonate as the source of insoluble calcium. In Study 2, the percent demineralization values were -8.50, +1.67, and +12.64 for the 1.5% arginine/Dical/1450 ppm fluoride, the positive control, and negative control dentifrices, respectively. Study validation was successfully achieved by showing that the positive control was statistically significantly better at preventing demineralization than the negative control (p < 0.0001). The arginine-containing dentifrice was shown to be statistically significantly better at preventing enamel demineralization than the positive control (p < 0.0001). Plaque metabolism measures for plaque exposed to the three treatments gave the following values for ammonia production after an arginine-sucrose challenge, expressed in nanomoles per milligram plaque: 162.7; 105.4; and 115.9 for the 1.5% arginine/Dical/1450 ppm fluoride, positive control, and negative control dentifrices, respectively. No statistically significant differences were observed between the three treatments, but the arginine-based dentifrice showed directionally higher ammonia production than both the positive and negative controls In Study 3, the percent demineralization values were +1.16, +4.96, and +15.34, for the 1.5% arginine/calcium carbonate/1 000 ppm fluoride, the positive control, and negative control dentifrices, respectively. Study validation was successfully achieved by showing that the positive control was statistically significantly better at preventing demineralization than the negative control (p < 0.0001). The arginine-containing dentifrice was shown to be statistically significantly better at preventing enamel demineralization than the positive control (p < 0.05). Plaque metabolism measures for plaque exposed to the three treatments gave the following values for ammonia production after an arginine-sucrose challenge, expressed in nanomoles per milligram plaque: 99.6; 56.2; and 42.2 for the 1.5% arginine/calcium carbonate/1000 ppm fluoride, the positive control, and negative control dentifrices, respectively. Plaque treated with the arginine- containing dentifrice produced significantly more ammonia than the positive and negative control dentifrices (p < 0.05). No significant difference in ammonia production was observed between the two controls. Lactic acid production after a sucrose challenge gave the following values, expressed as nanomoles per milligram plaque: 4.06; 5.12; and 4.64 for the 1.5% arginine/calcium carbonate/1000 ppm fluoride, the positive control, and negative control dentifrices, respectively. No significant difference was observed between the three treatments, but the arginine-based treatment showed directionally lower lactic acid production. RESULTS: The results of these three studies show that dentifrices containing 1.5% arginine, an insoluble calcium compound, and fluoride have a significantly improved ability to promote remineralization and prevent demineralization of enamel relative to dentifrices containing the same level of fluoride alone. Two different sources of insoluble calcium were evaluated, Dical and calcium carbonate. Dentifrices with Dical and with calcium carbonate, each in combination with 1.5% arginine and fluoride, provided superior efficacy as compared to matched dentifrices with fluoride alone, and the two products demonstrated comparable efficacy in promoting remineralization. The results of these studies demonstrate that the addition of 1.5% arginine to Dical-and calcium carbonate-based fluoride dentifrices provides superior efficacy in preventing demineralization and promoting remineralization, and, further, indicate that he arginine-containing dentifrices enhance the ability of plaque to metabolize arginine to ammonia.

Development of an enhanced anticaries efficacy dual component dentifrice containing sodium fluoride and dicalcium phosphate dihydrate.

A dual-chamber dentifrice, which contains sodium fluoride (NaF) in one component and dicalcium phosphate dihydrate (dical) in the other, has been developed. The dentifrice is packaged in a dual-chamber tube and is formulated to deliver 1100 ppm F. A series of studies consisting of in vitro fluoride uptake, in vivo calcium labeling, intraoral remineralization-demineralization, and animal caries studies were performed to support the improved anticaries efficacy of this product in comparison to a sodium fluoride/silica dentifrice (NaF/silica). An in vitro fluoride uptake study comparing 1100 ppm F NaF/dical dentifrice to 1100 ppm F NaF/silica showed that NaF/dical delivered significantly more fluoride than NaF/silica, 3.72 +/- 0.36 micrograms/cm2 versus 2.41 +/- 0.10 micrograms/cm2. A 6-day in vivo brushing study with a 44Ca labeled NaF/dical dentifrice showed that calcium from dical penetrated demineralized enamel and was present in plaque up to 18 hrs since the last brushing. An intra-oral remineralization-demineralization study was performed to evaluate NaF/dical's ability to promote remineralization in comparison to three silica-based dentifrices containing 0, 250, and 1100 ppm F as NaF. The percent mineral changes after treatment were +20.44 +/- 17.14 for NaF/dical, +9.27 +/- 19.53 for 1100 ppm NaF/silica, -1.43 +/- 20.57 for 250 ppm NaF/silica, and -12.36 +/- 32.76 for 0 ppm F/silica. A statistical analysis showed that the dual-chamber NaF/dical dentifrice was significantly more effective than the 1100 ppm NaF/silica dentifrice at promoting remineralization. A rat caries study was performed to evaluate NaF/dical ability to prevent caries in comparison to 1100 ppm F NaF/silica, 250 ppm F NaF/silica, silica, and dical dentifrices. The mean smooth surface caries scores were 1.6 +/- 2.8 for NaF/dical, 5.5 +/- 6.2 for 1100 ppm F NaF/silica, 10.6 +/- 6.2 for 250 ppm F NaF/silica, 13.7 +/- 4.7 for 0 ppm F/silica, and 9.5 +/- 7.8 0 ppm F/dical. A statistical analysis showed that the the dual-chamber NaF/dical dentifrice was superior to all other treatments tested in preventing caries in rats. The dical dentifrice was significantly superior to the silica dentifrice in preventing caries, which indicates that dical alone exhibits anticaries efficacy. In conclusion, individual and cumulative results from the fluoride uptake, intra-oral remineralization-demineralization, and rat caries studies from the dual chamber NaF/dical dentifrice support the improved anticaries efficacy of this product.

A study of the ability of an in situ remineralization model to differentiate between the effects of two fluoride dentifrices that produced significantly different clinical caries results.

The purpose of this study was to determine whether an in situ remineralization model was able to show a difference in the effects of two dentifrices of different fluoride concentrations and significantly different clinical efficacies. Three dentifrices were tested in a double-blind, cross-over study design. The products contained 0 ppm F, 250 ppm F, or 1000 ppm F from sodium fluoride and were formulated with a silica base according to the formulations used in a human caries trial (Koch et al., 1990). Nineteen subjects each carried three or four thin sections of enamel in their partial dentures. The thin sections, containing artificial caries lesions, were covered with a steel mesh to provide space for plaque formation and then brushed in situ three times daily with the dentifrices. Following the two-week treatment periods, the specimens were removed from the dentures and analyzed for changes in mineral content. The findings showed that the placebo dentifrice (0 ppm F) resulted in 56.8 +/- 74.3% demineralization, the 250-ppm-F dentifrice produced 12.9 +/- 41.3% demineralization, thereby showing partial caries protection, and the 1000-ppm-F dentifrice produced 17.3 +/- 32.1% remineralization. Linear regression analysis showed that the percent remineralization was significantly related to the fluoride concentration in the dentifrice (p less than 0.001). The 250-ppm-F dentifrice was also significantly less effective than the 100-ppm-F dentifrice (p = 0.04, one-tailed Fisher Protected LSD test). These findings are in accord with the human caries trial and support the use of the present in situ remineralization model for prediction of the anticaries efficacy of fluoride dentifrice products.

Findings from an in situ thin-section sandwich model for evaluating cariogenic and anti-cariogenic activity.

This report summarizes the findings from eight individual remineralization studies that used the thin-section sandwich model. This model uses thin sections of human enamel (or dentin) containing caries-like lesions sandwiched between sheets of thin plastic which are then implanted into the buccal surfaces of molars in removable partial mandibular dentures. Toothbrushing with a sodium fluoride-positive control dentifrice for two-week periods always produced positive remineralization of the lesions, and similar use of a placebo always produced mean mineral loss. In most studies, the difference was significant at p less than 0.01. However, variation among specimens placed within an individual mouth were often large and even included cases where one lesion gained mineral while a closely adjacent lesion lost mineral. Similarly, mean mineral changes produced by an individual subject were not consistent from study to study and ranged from net demineralization in one study to net remineralization in another study. Nevertheless, mean mineral changes from all eight studies showed that all subjects produced more remineralization than demineralization when using a sodium fluoride-positive control dentifrice. Data are presented showing remineralization of thin-section lesions from a number of other fluoride and non-fluoride dentifrices and mouthrinses and showing that a product with reduced anti-caries activity (as measured by several tests) also resulted in reduced remineralization by the thin-section model.

Remineralization and demineralization in situ from a triclosan/co-polymer/fluoride dentifrice.

An in situ study was conducted to evaluate the effect of a dentifrice containing 1100 ppm F (NaF) and triclosan, an anti-plaque agent, on remineralization of artificially-formed caries lesions in thin sections of human enamel. The thin sections were placed in mandibular partial dentures of 15 subjects and covered with a steel mesh to provide an area for plaque accumulation. The subjects brushed their teeth and dentures three times daily for two-week periods in a cross-over design, after which the specimens were removed and analyzed by quantitative microradiography for changes in mineral content. Results showed that lesions treated with the triclosan-fluoride product were remineralized 18.0 +/- 23.4% compared with 19.0 +/- 32.3% from a 1100-ppm F (NaF) positive control. Use of a placebo dentifrice resulted in 71.9% demineralization. The findings showed that triclosan neither enhanced nor interfered with the promotion of remineralization by fluoride.

Evaluation of the effects of a pyrophosphate-fluoride anticalculus dentifrice on remineralization and fluoride uptake in situ.

Enamel slabs and thin sections with artificially formed caries lesions were placed in the removable dentures of 15 subjects who brushed them three times daily for 2 weeks with a 1.3% pyrophosphate/1,100 ppm F/1.5% Gantrez dentifrice, a 1,100-ppm F dentifrice without pyrophosphate or Gantrez, or a placebo dentifrice in a double-blind, crossover study. Analysis of the thin sections by quantitative microradiography showed that the pyrophosphate/F dentifrice remineralized the lesions 15.9% (p less than 0.05) and the fluoride dentifrice 11.2%, whereas the placebo produced 4.4% demineralization. Fluoride uptake by the enamel slabs was similar for both fluoride dentifrices and significantly greater from the placebo dentifrice (p less than 0.05). The findings suggest that the anticaries mechanisms of fluoride include not only the prevention of demineralization, but also the promotion of remineralization.

Effect of two sodium fluoride dentifrices on fluoride uptake and remineralization in situ.

Two dentifrices containing 1100 ppm F from sodium fluoride in silica bases were compared to a placebo dentifrice in an in situ remineralization and fluoride uptake study. Fifteen subjects brushed artificially-formed caries lesions in 60 thin enamel sections and 30 enamel blocks with each dentifrice in a double-blind, randomized, cross-over study design. Analysis of the thin sections by quantitative microradiography before and after exposure to toothbrushing showed that the fluoride dentifrices produced 18.3% and 7.1% remineralization whereas use of the placebo resulted in 10.3% demineralization. The differences between all three dentifrices were statistically significant. Fluoride concentrations at the surface of the lesion increased from approximately 700 ppm F in untreated specimens to approximately 1800 ppm F in specimens treated with either of the two fluoride dentifrices. These data suggest that formulation differences may affect the anticaries activity of a dentifrice without being reflected by fluoride deposition.

The effect of plaque thickness on progression of artificial caries lesion formation in situ.

Eighty thin enamel sections with artificially-formed caries lesions were implanted in the buccal surfaces of molars (in the removable partial dentures of ten subjects) and covered with a steel mesh for plaque accumulation to occur. The mesh was placed in contact with the enamel surface in half the lesions and 0.5 mm above the lesions in the other half, thus facilitating formation of thin and thick plaque samples. Following two-week use of a non-fluoride dentifrice, the lesions were analyzed for mineral change by quantitative microradiography. Significant mineral was lost from lesions in both groups, but the loss was twice as large in the thick-plaque group. These findings are important to in vivo remineralization models, since they show that plaque thickness should be controlled for minimization of variation.

The effects of 1% pyrophosphate and 0.02% sodium fluoride on artificial caries lesions in vivo.

We evaluated the potential of a pyrophosphate-fluoride solution to affect the remineralizing-demineralizing equilibrium, i.e., caries-inhibiting/-promoting effects on enamel in vivo. Fifteen subjects carried dentin blocks and enamel thin sections with artificial caries lesions in removable partial dentures for periods of two weeks, during which time they rinsed twice daily in a double-blind, randomized cross-over design with solutions containing (a) 90 ppm F, (b) 90 ppm F and 1% pyrophosphate, or (c) no active agents (placebo). A severe cariogenic challenge provided to the lesions by plaque under a stainless steel mesh cover resulted in the placebo-treated lesions losing 70.2% +/- 72.1% mineral. The pyrophosphate rinse with fluoride held the mineral loss to only 28.1 +/- 52.8%, while the fluoride rinse without pyrophosphate held the loss to 24.2 +/- 50.1%. The differences between the fluoride and placebo results were significant (p less than 0.01), but the difference between the two fluoride groups was not. A large amount of fluoride was deposited in the dentin lesions. In the surface layer, the concentration was increased from 1000 ppm F to more than 2300 ppm F by both fluoride treatments. The concentration of fluoride in both groups of fluoride-treated lesions further increased to more than 3500 ppm F in the approximate center of the lesion before declining in deeper layers toward the level found in the placebo-treated group. The findings from both mineral change and fluoride uptake phases of this study show that in the presence of 90 ppm F, 1% pyrophosphate did not promote demineralization of artificial caries lesions.