Interaction of fluoride complexes derived from glass-ionomer cements with hydroxyapatite

A study has been undertaken of the interaction of complexed fluoride extracted from glass-ionomer dental cements with synthetic hydroxyapatite powder. Extracts were prepared from two commercial glass-ionomers (Fuji IX and ChemFlex) under both neutral and acidic conditions. They were analysed by ICP-OES and by fluoride-ion selective electrode with and without added TISAB to decomplex the fluoride. The pH of the acid extracts was 4, conditions under which fluoridecomplexes with protons as HF or HF2, it also complexes with aluminium, which was found to be present in higher amounts in the acid extracts. Fluoride was found to be almost completely complexed in acid extracts, but not in neutral extracts, which contained free fluoride ions. Exposure of these extracts to synthetic hydroxyapatite powder showed that fluoride was taken up rapidly (within 5 minutes), whether or not it was complexed. SEM (EDAX) study of recovered hydroxyapatite showed only minute traces of aluminium taken up under all conditions. This showed that aluminium interacts hardly at all with hydroxyapatite, and hence is probably not involved in the remineralisation process

Textural and structural properties of bioactive glasses in the system CaO-SiO2

Gel-derived CaO-SiO2 binary glasses of CaO mole fractions 0. 2, 0.3 and 0. 4 have been prepared and characterised. Pore diameter specific pore volume, skeletal density and porosity were found to increase with increasing CaO-content, whereas a concomitant decrease in specific surface area was observed. Si-29 NMR indicated that the 0.2 CaO mole fraction glass consisted of higly polymerized Q(4) and Q(3) silicate species, with some Q(2) units. With increasing CaO mole fraction, these silicate species became progressively depolymerised such that isolated SiO4 tetrahedra were detected within the 0.4 CaO glass matrix. Unusually, the glasses retained a proportion of Q(4) and Q(3) species as the CaO mole fraction was increased. All glass formulations exhibited in vitro bioactivity. The rate of hydroxyapatite precipitation followed the order 0.2 CaO > 0.4 CaO > > 0.3 CaO, an effect that is attributed to differences in the rate of dissolution of calcium from these glasses. This, in turn, appears to be dependent upon the proportion of Ca 21 participating in the formation of the glassy network

Interaction of fluoride complexes derived from glass-ionomer cements with hydroxyapatite

A study has been undertaken of the interaction of complexed fluoride extracted from glass-ionomer dental cements with synthetic hydroxyapatite powder. Extracts were prepared from two commercial glass-ionomers (Fuji IX and ChemFlex) under both neutral and acidic conditions. They were analysed by ICP-OES and by fluoride-ion selective electrode with and without added TISAB to decomplex the fluoride. The pH of the acid extracts was 4, conditions under which fluoride complexes with protons as HF or HF2-, it also complexes with aluminium, which was found to be present in higher amounts in the acid extracts. Fluoride was found to be almost completely complexed in acid extracts, but not in neutral extracts, which contained free fluoride ions. Exposure of these extracts to synthetic hydroxyapatite powder showed that fluoride was taken up rapidly (within 5 minutes), whether or not it was complexed SEM (EDAX) study of recovered hydroxyapatite showed only minute traces of aluminium taken up under all conditions. This showed that aluminium interacts hardly at all with hydroxyapatite, and hence is probably not involved in the remineralisation process

Release of antimicrobial compounds from a zinc oxide-chelate cement

This study examined the release of cetylpyridinium chloride and benzalkonium chloride from fatty acid chelate temporary dental cement and their antimicrobial effects. The cement was Cavex Temporary, and either cetylpyridinium chloride or benzalkonium chloride was added (1% or 5% by mass), incorporating into the base paste. Release of the additives was determined by reverse-phase high-performance liquid chromatography. Possible chemical interactions between the cement components and additives were examined by Fourier transform infrared (FTIR) spectroscopy. Antimicrobial effects were assessed by measuring the zone of inhibition around sample discs after 24 h in a Streptococcus mutans culture. FTIR spectroscopy showed no interaction with cement components. For both additives, release was by diffusion for approximately the first 6 hours, with equilibration after about 2 weeks. Diffusion coefficients were 1.76 m2 s½ to 8.05 × 10−12 m2 s½ and total release was 10.3 to 44.7% of additive loading. Zones of inhibition with additive were significantly larger than those for control discs. In conclusion, the antimicrobial properties of Cavex temporary cement are improved by the addition of the antimicrobial compounds cetylpyridium chloride and benzalkonium chloride, which are released by a diffusion process

Assessment of the impact of the addition of nanoparticles on the properties of glass–ionomer cements

The aim of the study was to evaluate the effects of incorporation of Al2O3, ZrO2 and TiO2 nanoparticles into glass–ionomer cements (GICs). Two different GICs were used in the study. Four groups were prepared for each material: the control group (without nanoparticles) and three groups modified by the incorporation of nanoparticles at 2, 5 or 10 wt %, respectively. Cements were mixed and placed in moulds (4 mm × 6 mm); after setting, the samples were stored in saline (one day and one week). Compressive strengths were measured and the morphology of the fractured surfaces was analyzed by scanning electron microscopy. The elements released into the storage solutions were determined by Inductively coupled plasma-optical emission spectrometry (ICP-OES). Addition of nanoparticles was found to alter the appearance of cements as examined by scanning electron microscopy. Compressive strength increased with the addition of ZrO2 and especially TiO2 nanoparticles, whereas the addition of Al2O3 nanoparticles generally weakened the cements. The ion release profile of the modified cements was the same in all cases. The addition of Al2O3, ZrO2 and TiO2 nanoparticles into GICs is beneficial, since it leads to reduction of the microscopic voids in the set cement. Of these, the use of ZrO2 and TiO2 nanoparticles also led to increased compressive strength. Nanoparticles did not release detectable levels of ions (Al, Zr or Ti), which makes them suitable for clinical use

Component release and mechanical properties of endodontic sealers following incorporation of antimicrobial agents

Root canal sealers with antimicrobial activity are highly beneficial; therefore, their antimicrobial properties could be improved by incorporation of antimicrobial agents. In the present study, the release of the quaternary ammonium compounds from endodontic sealers admixed with either benzalkonium chloride (BC) or cetylpyridinium chloride (CPC) at loadings of 2% wt was monitored. The effect of these additives on the compressive strengths and their release from the sealers was determined after 1 and 4 weeks. All of the materials studied were found to be capable of releasing antimicrobial additive in useful quantities. The release of CPC occurred to a statistically significant greater extent than BC for all materials. The addition of both BC and CPC generally decreased the compressive strength of all the endodontic sealers, with the exception of CPC in AH Plus, where the compressive strength was significantly increased. This suggests that, for these endodontic sealers, the antimicrobial additives alter the setting chemistry. AH Plus is an epoxy-based material cured with an amine, and in this case the increase in compressive strength with CPC is attributed to an enhanced cure reaction with this system. In all other cases, the additive inhibited the cure reaction to a greater or lesser extent

Kinetics of ion release from a conventional glass-ionomer cement

Release kinetics for sodium, silicon, aluminium, calcium and phosphorus from conventional glass-ionomer dental cement has been studied in neutral and acid conditions. Specimens (6 mm height × 4 mm diameter) were made from AquaCem (Dentsply, Konstanz, Germany), 6 per experiment. They were matured (37 °C, 1 h), then placed in 5 cm3 storage solution at 20–22 °C. In the first experiment, deionised water, changed daily for 28 days, was used. In the second, deionised water, changed monthlyfor 21 months, was used. In the third, lactic acid (20 mmol dm−3, pH: 2.7 ± 0.1), changed monthly for 21 months was used. After storage each solution was analyzed by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Results showed that in neutral conditions, no calcium was released, but in acid, significant amounts were released. The other elements (Na, Al, Si and P) were released in neutral as well as acid conditions, with greater amounts in acid. More frequent changes of water gave greater release. In neutral conditions, release over 21 months followed the equation: [E]c = [E]1t/(t + t½) + β√t ([E] c is the cumulative release of the element). In acid conditions, this became: [E]c = [E]1t/(t + t½) + αt. Hence release of all elements was shown to occur in two steps, a rapid initial one (half-life: 12–18 h) and a longer second one. In neutral conditions, the longer step involves diffusion; in acid it involves erosion. These patterns influence the material’s bioactivity

Is exercise/physical activity effective at reducing symptoms of post-traumatic stress disorder in adults — a systematic review

Background: Exercise has been used to manage symptoms of post-traumatic stress disorder (PTSD). The effect of exercise on PTSD outcomes has been previously explored in several studies. However, it still remains unclear what type of exercise/physical activity, intensity and duration is most effective for reducing symptoms of PTSD. A systematic review was conducted to determine which forms of exercise or physical activity have the greatest effect on PTSD outcome scores including an evaluation of exercise frequency and volume. Methods: The following electronic databases were systematically searched from January 1980 to June 2021: MEDLINE, PsycINFO, PubMed and Web of Science. Inclusion criteria were studies investigating adults aged 18 or over, reporting the effect of exercise and physical activities on PTSD symptom outcome scores. Two reviewers independently extracted information on study characteristics, exposure and outcomes. In total of 3,217 articles were screened and 23 full text articles further assessed, with 13 RCT's included in the review, covering seven exercise/physical activity interventions. The study protocol was registered prospectively with PROSPERO (CRD42021255131). Results: Thirteen studies from four countries involving a total of 531 patients were selected for inclusion. Individual forms of exercise/physical activity examined showed some effect on reducing PTSD symptoms but combined exercises (resistance training, aerobic, strength and yoga) administered over a 12 week period, three times a week for 30–60 min showed greater effects on PTSD symptoms. Conclusion: The limited evidence suggests that a combined exercise intervention has the best evidence for a having a beneficial effect on PTSD symptoms. Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=255131

Epilepsy in adults with mitochondrial disease: A cohort study.

OBJECTIVE: The aim of this work was to determine the prevalence and progression of epilepsy in adult patients with mitochondrial disease. METHODS: We prospectively recruited a cohort of 182 consecutive adult patients attending a specialized mitochondrial disease clinic in Newcastle upon Tyne between January 1, 2005 and January 1, 2008. We then followed this cohort over a 7-year period, recording primary outcome measures of occurrence of first seizure, status epilepticus, stroke-like episode, and death. RESULTS: Overall prevalence of epilepsy in the cohort was 23.1%. Mean age of epilepsy onset was 29.4 years. Prevalence varied widely between genotypes, with several genotypes having no cases of epilepsy, a prevalence of 34.9% in the most common genotype (m.3243A>G mutation), and 92.3% in the m.8344A>G mutation. Among the cohort as a whole, focal seizures, with or without progression to bilateral convulsive seizures, was the most common seizure type. Conversely, all of the patients with the m.8344A>G mutation and epilepsy experienced myoclonic seizures. Patients with the m.3243A>G mutation remain at high risk of developing stroke-like episodes (1.16% per year). However, although the standardized mortality ratio for the entire cohort was high (2.86), this ratio did not differ significantly between patients with epilepsy (2.96) and those without (2.83). INTERPRETATION: Epilepsy is a common manifestation of mitochondrial disease. It develops early in the disease and, in the case of the m.3243A>G mutation, often presents in the context of a stroke-like episode or status epilepticus. However, epilepsy does not itself appear to contribute to the increased mortality in mitochondrial disease

Optomechanical design of TMT NFIRAOS Subsystems at INO

The adaptive optics system for the Thirty Meter Telescope (TMT) is the Narrow-Field InfraRed Adaptive Optics System (NFIRAOS). Recently, INO has been involved in the optomechanical design of several subsystems of NFIRAOS, including the Instrument Selection Mirror (ISM), the NFIRAOS Beamsplitters (NBS), and the NFIRAOS Source Simulator system (NSS) comprising the Focal Plane Mask (FPM), the Laser Guide Star (LGS) sources, and the Natural Guide Star (NGS) sources. This paper presents an overview of these subsystems and the optomechanical design approaches used to meet the optical performance requirements under environmental constraints