Phosphate Peak Research Articles

Efficacy and micro-characterization of pathophysiological events on caries-affected dentin treated with glass-ionomer cements

The aim of this study was to evaluate if mechanical cycling influences bioactivity and bond strength at the glass-ionomer cement-dentin interface, after load cycling. Microtensile bond strength (MTBS) was assessed with Ketac-Bond (conventional glass ionomer/GIC) or Vitrebond Plus (resin-modified/RMGIC), in sound dentin or in caries-affected dentin (CAD). Debonded dentin surfaces were studied by field emission scanning electron microscopy (FESEM), and remineralization was evaluated through nanohardness (Hi) and Young’s modulus (Ei), Raman spectroscopy, and Masson׳s trichrome staining technique. Load cycling did not affect MTBS, except when Ketac-Bond was applied on sound dentin, which attained 100% pretesting failures. Minerals precipitated in porous platforms. GIC promoted total occlusion of tubules, and RMGIC originated empty or partial occluded tubules. In sound dentin, load cycling produced an increase of the relative presence of crystalline minerals after using Ketac-Bond (Phosphate peak, from 18.04 up to 81.29cm−1 at hybrid layer, and from 19.28 up to 108.48cm−1 at the bottom of the hybrid layer; Carbonate peak, from 8.06 up to 15.43cm−1 at the hybrid layer, and from 7.22 up to 19.07cm−1 at the bottom of the hybrid layer). Vitrebond Plus, in sound dentin, attained opposite outcomes. In CAD treated with Ketac-Bond, the highest Hi (1.11GPa) and Ei (32.91GPa) values were obtained at the hybrid layer after load cycling. This GIC showed increased and immature mineral components (an average of 25.82 up to 30.55cm−1), higher frequencies of crosslinking (considering the pyridinium ring at hybrid layer, from 4.1 up to 6.86cm−1; at bottom of the hybrid layer, from 7.55 up to 8.58cm−1) and worst collagen quality (considering the ratio amide I/AGEs-pentosidine at the hybrid layer, from 0.89 up to 0.69cm−1; at the bottom of the hybrid layer, from 1.39 up to 1.29cm−1) after load cycling, at the interface of the CAD samples. Both Hi and Ei of CAD treated with RMGIC were not affected after load cycling, though phosphates, carbonates and crystallinity increased. The organic components showed a dissimilar crosslinking and an improvement of the nature of collagen. Trichrome staining showed lower signs of demineralization or exposed proteins after mechanical loading, though Vitrebond Plus exhibited a slight increment in red intensity at the interface. The null hypothesis to be tested is that bond strength, chemical bonding and mechanical performance of the tested ionomer-based cements would not be influenced by the application of load cycling on restorations of sound and caries-affected dentin substrates.

The hardness and chemical changes in demineralized primary dentin treated by fluoride and glass ionomer cement

Abstract Background Fluoride plays an important role in the control of dental caries. Aim To evaluate the chemical exchange between restoration of glass ionomer cement of high viscosity (GIC) and primary dentin with application of sodium fluoride (NaF) 2% through changes in hardness from uptake of calcium, phosphate and fluoride. Material and method Class I cavities were prepared in 40 sound primary molars, and the sample was divided into two groups (n=20) according to dentin condition: sound (1) and demineralized (2). Sub-groups (n=10) were formed to investigate the isolated action of the GIC or the association with NaF (F). This in vitro study examined the chemical exchange under two conditions, sound and demineralized dentin (pH cycling), to simulate the occurrence of mineral loss for the caries lesion. G1 and G2 received GIC restoration only; groups G1F and G2F received NaF before GIC restoration. The specimens were prepared for Knoop hardness test and micro-Raman spectroscopy. A two-way ANOVA test (α = 0.05) was used for statistical analysis. Micro-Raman data were qualitatively described. Result Increased hardness was observed in all the sites of direct contact with GIC in sound and demineralized dentin for all groups (p<0.001); no difference was observed in microhardness after application of NaF (p>0.05). In the evaluation of micro-Raman, direct contact between GIC and dentin for sound and demineralized dentin resulted in increased peaks of phosphate. Conclusion The exchange between GIC and demineralized dentin may induce changes of mechanical properties of the substrate, and uptake of mineral ions (phosphate) occurs without the influence of NaF.

Effects of phosphate and citric acid on Pb adsorption by red soil colloids

There are abundant organic acids in rhizospheric soil, which may interfere in the reaction between phosphate and heavy metals. Effects of phosphate on Pb2+ adsorption by red soil colloids(Ultisol) were studied in the presence of citric acid (Cit) through batch equilibrium experiments, Zeta potential and X‐ray diffraction (XRD) analyses. Results showed that in the presence of different concentrations of phosphate (P), the peak‐like curves of Pb2+ sorption was moved up even disappeared. When the Langmuir equation was used to model isothermal adsorption curve of Pb2+, the adsorption reaction constant (K), the maximum adsorption quantity (Xm) of several treatments were both in a decreasing order of 1.0 mmol/L P > 1.0 mmol/L P + 0.5 mmol/L Cit > 0.5 mmol/L Cit. Under the influence of citric acid, the Pb2+ adsorption amount increased at pH < 4.5, and then decreased gradually with pH increase. The order of Zeta potential reduction was: 1 mmol/L P + 0.5 mmol/L Cit > 0.5 mmol/L Cit > 1 mmol/L P, which were different from that of the Pb2+ adsorption amount, suggesting that the adsorption of Pb2+ was not only an electrical adsorption in the presence of P. XRD patterns proved that occurrence of pyromorphite for the treatment with 1.0 mmol/L P addition, whereas no lead phosphate peak was detected in other treatments. The mechanism of Pb2+ adsorbed in red soil colloids with addition of phosphate was primary formation of pyromorphite‐like compounds. However, 0.5 mmol/L Cit inhibited the formation of pyromorphite. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 969–974, 2016

Electrosprayed calcium phosphate nano-carriers as therapeutic agents

Event Abstract Back to Event Electrosprayed calcium phosphate nano-carriers as therapeutic agents Yogeshwar Chakrapani1, 2, Sampath T. Kumar1, Kumary T. V2 and Deepa K. Raj2 1 Indian Institute of Technology Madras, Medical Materials Laboratory, India 2 Sree Chitra Tirunal Institute for Medical Sciences and Technology, Tissue Culture Laboratory, India Introduction: Calcium phosphate particles intended as bone fillers and drug delivery agents are gaining interest worldwide. Size of the particles becomes an important factor when they are intended to act as site specific delivery agents, for therapeutic purposes. Cellular uptake, velocity of drug carrier in physiological pathways and specificity towards binding of therapeutic molecules are some key parameters that are greatly influenced by particle size[1]. The aim of the current study was to produce calcium phosphate particles through a modified electrospraying process[2]; characterize them physicochemically, evaluate their cytocompatibility and to analyse the efficacy of the particles to act as drug delivery systems. Materials and Methods: Calcium nitrate tetrahydrate (CNt) and triethyl phosphite (TEP) were used as the calcium and phosphorous precursors with an aqueous solvent. Sols with the required Ca/P ratio (1.67 & 1.61) were prepared by adding CNt solution drop wise to the hydrolysed TEP solution. The obtained sols were aged and subsequently blended with a polyvinylalcohol solution. The solution was loaded into a 10ml syringe fitted with an 18G blunted needle. The tip to collector distance, flow rate and voltage were optimised for electrospraying. The as sprayed particles were dried overnight and then subjected to a controlled heating upto 500˚C. The particles obtained on heating 1day and 5days aged sols of 1.67 and 1.61 Ca/P ratio will be referred to as CaP167-1d, CaP167-5d, CaP161-1d and CaP161-5d respectively. Phase confirmation was done through X-ray diffraction (XRD). Stability of phases was tested by heating upto 900˚C. The particles size and morphology were analysed using transmission electron microscopy (TEM). In vitro biological evaluation of the particles were performed using L-929 and HOS cell lines. The drug delivering capacities of the particles were assessed using tetracycline as model drug. Results and Discussion: Figure 1 shows the results of XRD and TEM analysis. XRD patterns were matched with that of hydroxyapatite (JCPDS file no. 9-432). At 500˚C the patterns of all the particles are similar whereas on heating to 900˚C, CaP167-1d and 5d are the same while CaP161-1d and 5d develop peaks of β-tricalcium phosphate. From TEM imaging it is evident that increasing the aging time of sols has lead to an increase in the electrosprayed particle size. MTT assay confirms the non cytotoxic nature of the particles (Fig. 2a). Cell adhesion and proliferation on the surface of pelletized particles confirms the biocompatibility (Fig. 2b). Cellular uptake studies confirm the potential of the particles to act as therapeutic delivery agents. The loading and release profiles reveal that particles with a CaP ratio of 1.61 show a higher loading but a lesser release when compared to those with a CaP ratio of 1.67. Also smaller particles show a better loading and release profiles than their larger size counterparts. Conclusion: In conclusion, a modified electrospraying process has been used to produce HA and CDHA particles in different size regimes. The particles do not elicit any toxicity and are readily taken up by the cells. Thus,electrosprayed CaP particles with controllable sizes are valid candidates for targeted delivery of therapeutic agents.The process opens up avenues for producing other ceramic particles as well. Dr. H. K. Varma, Bioceramics Laboratory, SCTIMST

Self-etching zinc-doped adhesives improve the potential of caries-affected dentin to be functionally remineralized.

The aim of this study was to evaluate if mechanical cycling influences bioactivity at the resin-carious dentin interface after bonding with Zn-doped self-etching adhesives. Caries-affected dentin surfaces were bonded with: Clearfil SE bond (SEB), and 10 wt. % ZnO nanoparticles or 2 wt. % ZnCl2 were added into the SEB primer or bonding components. Bonded interfaces were stored during 24 h and then tested or submitted to mechanical loading. Microtensile bond strength was assessed. Debonded dentin surfaces were studied by field emission scanning electron microscopy. Remineralization of the bonded interfaces was evaluated through nanohardness (Hi) and Young's modulus (Ei), Raman spectroscopy/cluster analysis, and Masson's trichrome staining technique. New precipitation of minerals composed of zinc-base salts and multiple Zn-rich phosphate deposits was observed in samples infiltrated with the Zn-doped adhesives. At the hybrid layer, specimens treated with ZnO incorporated in the primer (SEB·P-ZnO), after load cycling, attained the highest Ei and Hi. Load cycling increased Ei at the bottom of the hybrid layer when both, SEB undoped and SEB with ZnCl2 included in the bonding (SEB·Bd-ZnCl2), were used. ZnO incorporated in the primer promoted an increase in height of the phosphate and carbonate peaks, crystallinity, relative mineral concentration, and lower collagen crosslinking. ZnCl2 included in the bonding attained similar results, but relative mineral concentration decreased, associated to higher crosslinking and restricted collagen maturation. In general, a substantial restoration of the mechanical properties of caries-affected dentin substrata occurred when SEB-Zn doped adhesives were used and load cycled was applied, leading to functional and biochemical remineralization.

Dental Enamel Quality and Black Tooth Stain: A New Approach and Explanation by using Raman and AFM Techniques

This contribution takes in account investigation of dental enamel regarding “quality” of hydroxyapatite material involved in the mineralization process. Areas damaged by black stain were investigated in order to evaluate changes in chemical composition as compared to those of healthy dental enamel.Different sectors on tooth surfaces were analyzed using micro-Raman spectroscopy. The integral areas of ν1 (960 cm−1) phosphate peak as well as of B-type carbonate peak ν2 (1070 cm−1) were obtained to investigate structural differences between the specimens (healthy/unhealthy enamel tooth and different sectors on unhealthy surface tooth). A complete list of chemical specimens involved in chemical processes on dental enamel surface was obtained by Energy Dispersive x-rays (EDX) investigation.It was noticed that mineralized carbonate peak at 1070 cm−1 decreased significantly for unhealthy tooth enamel or spots areas (as fluorite groups), suggesting that carbonate ions are easily dissolved in the presence of fluoride.The present study is confirming an organic origin for the dental “black stain.” The “black stain” is the result of a complex generation process from the damaged enamel, thus explaining their reappearance after the mechanical removing. A possible model for the “black stain” generation process is advanced.

Radiotherapy effect on nano-mechanical properties and chemical composition of enamel and dentine

ObjectiveTo understand radiotherapy-induced dental lesions characterized by enamel loss or delamination near the dentine–enamel junction (DEJ), this study evaluated enamel and dentine nano-mechanical properties and chemical composition before and after simulated oral cancer radiotherapy. DesignSections from seven non-carious third molars were exposed to 2Gy fractions, 5 days/week for 7 weeks for a total of 70Gy. Nanoindentation was used to evaluate Young's modulus, while Raman microspectroscopy was used to measure protein/mineral ratios, carbonate/phosphate ratios, and phosphate peak width. All measures were completed prior to and following radiation at the same four buccal and lingual sites 500 and 30μm from the DEJ in enamel and dentine (E-500, E-30, D-30 and D-500). ResultsThe elastic modulus of enamel and dentine was significantly increased (P≤0.05) following radiation. Based on Raman spectroscopic analysis, there was a significant decrease in the protein to mineral ratio (2931/430cm−1) following radiation at all sites tested except at D-500, while the carbonate to phosphate ratio (1070/960cm−1) increased at E-30 and decreased at D-500. Finally, phosphate peak width as measured by FWHM at 960cm−1 significantly decreased at both D-30 and D-500 following radiation. ConclusionsSimulated radiotherapy produced an increase in the stiffness of enamel and dentine near the DEJ. Increased stiffness is speculated to be the result of the radiation-induced decrease in the protein content, with the percent reduction much greater in the enamel sites. Such changes in mechanical properties and chemical composition could potentially contribute to DEJ biomechanical failure leading to enamel delamination that occurs post-radiotherapy. However, other analyses are required for a better understanding of radiotherapy-induced effects on tooth structure to improve preventive and restorative treatments for oral cancer patients.

Synthesis of the lead-calcium HAP solid solutions

A series of lead-calcium hydroxylapatite solid solution was synthesized by the precipitation method. Characterization by various means confirmed the forming of the continuous solid solution over a whole Pb/(Pb+Ca) mole fraction range. An obvious deviation of both a and c lattice parameters from Vegard’s rule was observed. The solids of XPb = 0–0.51 were typically prism crystals with hexagonal pyramid as a termination (particle size 50–100 nm); those of XPb = 0.61–0.69 were the typical hexagonal columnar crystals with pinacoid or hexagonal pyramid as termination, which elongated along c axis (particle size 200–600 nm); those of XPb = 0.80–1.00 were the typical prism crystals with hexagonal pyramid as termination (particle size 2–20 μm). The phosphate peak area for the symmetric P-O stretching decreased with increasing Pb/(Pb + Ca) ratio and disappeared as the Pb/(Pb + Ca) ratio > 0.61, and two phosphate peaks of the P-O stretching were diminished with the increase in XPb. These variations could be caused by a slight tendency of larger Pb2+ to prefer the M(II) sites and smaller Ca2+ to occupy the M(I) sites in the apatite structure.

Comparison of the Chemical Composition of Subchondral Trabecular Bone of Medial Femoral Condyle between with Advanced Osteoarthritis and without Osteoarthritis

BackgroundThe purpose of this study is to investigate differences of chemical composition between subchondral bone in advanced osteoarthritic (OA) and non-OA distal femur.MethodsTwenty femurs were harvested, respectively. The subchondral trabeculae were obtained from the middle of medial articular surface of distal femurs. A 10 mm diameter cylindrical saw was used to harvest. Raman spectroscopy, a non-destructive technique, was employed to determine the chemical information of the trabecular bones in the human distal femurs.ResultsThe maximum intensity of the phosphate peak was 2,376.51±954.6 for the non-OA group and 1,936.3±831.75 for the OA group. The maximum intensity of the phosphate peak observed between the two groups was significantly different (P=0.017). The maximum intensity of the amide I peak were 474.17±253.42 for the nonOA group and 261.91±205.61 for the OA group. The maximum intensity of the amide I peak were significantly different between the two groups (P=0.042). Also, among other chemical and matrix components (Hydroxyproline,Carbonate, Amide IIIdisordered;ordered, and CH2), the spectrums showed similar significant differences in the intensity (P=0.027, P=0.014, P=0.012; P=0.038, P=0.029). Area integration were performed to determine disorder in collagen's secondary structure via amide III (alpha helix/random coil). The value of the alpha helix to random coil band area are significantly different (P=0.021) and result showing that there was a trend toward higher collagen maturity for the nonosteoarthritic bone specimens.ConclusionsThe result suggested that OA may affect the chemical compositions of trabecular bone, and such distinctive chemical information may be.

Structural and composition of natural hydroxyapatite (HA) at different sintering temperatures

Hydroxyapatite (HA) is one of the most attractive biomaterials and widely used as a bone substitute due to its compositions are similar to the minerals in teeth and bones. Understanding of natural HA properties are useful in order to produces high quality of HA. In this paper, we report an easy and low cost method to extract the natural HA from femur cow bone and subsequently sintered at different temperature from 900 oC to 1300 oC. Structural, composition and surface morphology of natural Hydroxyapatite (HA) at different sintering temperatures (900 ̊ C, 1000 ̊ C, 1100 ̊ C, 1200°C and 1300 ̊ C) were discussed. The HA structural, composition and surface morphology were studied by using X-Ray Diffractometer (XRD), Fourier Transform Infrared (FTIR) and Scanning Electron Microscope (SEM), respectively. The results show the main HA phases were detected in the range of 31.72o - 31.82o (2Ө) for all sintered HA corresponding to 211 plane. The crystallite size of HA increases with sintering temperature from 900 ̊C to 1100 ̊C. Spectrums of FTIR revealed the existences of functional groups of carbonate (CO3 2-), phosphate (PO4 3-) and hydroxyl (OH-) peaks. SEM micrographs presented small and homogenous grains from 900°C to 1100°C. The grains look interconnected as sintering temperature increased at 1200°C and 1300°C. From this study, sintering process was found to be an easy and low cost method to produce natural HA from femur cow bones.

Masticatory function induced changes, at subnanostructural level, in proteins and mineral at the resin–dentine interface

ObjectiveThis study evaluated the ability of different in vitro mechanical loading tests to promote new mineral formation at the bonded dentine interfaces created with a two-step self-etching resin adhesive. MethodologyRestored teeth were divided in the following groups: (1) unloaded, load cycling with (2) sine waveform, (3) square waveform, and hold waveform for (4) 24h, and (5) 72h. Raman spectroscopy and cluster analysis were used to assess the resin–dentine interface. ResultsMechanical loading in CSEB-treated samples promoted a generalized increase of relative presence of minerals and ratio of phosphate peaks, except in square waveform, where the nature of collagen resulted damaged. Crystallinity of carbonate was higher than phosphate. The organic component showed, in general terms, an increase in crosslinking. Molecular orientation (α-helices) peaks augmented in all tests. Pentosidine vibration increases in all tests, except in hold 72h. Ratios amide I and II/CH2 incremented, in general. Non uniform parameters of Bis-GMA and adhesive penetration were encountered, as both increased at the bottom of the hybrid layer when loading square and hold 72h were applied. SignificanceFunctional remineralisation at the resin–dentine interface was attained after in vitro mechanical stimuli application. When loading in square waveform, the lowest vibrations to favor remineralisation were attained.

Synthesis and characterization of cadmium-calcium hydroxyapatite solid solutions

A series of cadmium-calcium hydroxyapatite solid solutions was prepared by an aqueous precipitation method. By various means, the characterizations confirmed the formation of continuous solid solutions over all ranges of Cd/(Cd+Ca) atomic ratio. In the results, both lattice parameters a and c display slight deviations from Vegard’s rule when the Cd/(Cd+Ca) atomic ratio is greater than 0.6. The particles change from smaller acicular to larger hexagonal columnar crystals as the Cd/(Cd+Ca) atomic ratio increases from 0–0.60 to 0.60–1.00. The area of the phosphate peak for symmetric P-O stretching decreases with the increase in Cd/(Cd+Ca) atomic ratio, and the peak disappears when the Cd/(Cd+Ca) atomic ratio is greater than 0.6; the two phosphate peaks of P-O stretching gradually merge together for the Cd/(Cd+Ca) atomic ratio near 0.60. These variations can be explained by a slight tendency of larger Cd ions to occupy M(2) sites and smaller Ca ions to prefer M(1) sites in the structure.

Remineralization of mechanical loaded resin–dentin interface: a transitional and synchronized multistep process

This study evaluated the ability of different in vitro mechanical loading tests to promote new mineral formation at bonded dentin interfaces. This research demonstrated a sequential transition in the dentin remineralizing procedure through the analysis of the mineral and matrix gradients. Mechanical loading in phosphoric acid (PA)-treated samples promoted a generalized increases in relative presence of minerals, crystallinity, ratio of phosphate peaks and a decrease in the gradient of mineral content. The organic component showed, in general terms, an increase in crosslinking. [Formula: see text]-helices incremented in sine and square waveform loading. In EDTA+SB specimens, the relative mineral concentration incremented when loading in hold, in general. Nonuniform parameters of Bis-GMA and adhesive penetration were encountered in both groups. PA+SB promoted the highest dentin mineralization degree when loading in square, based on the increase in the relative presence of minerals and crystallinity. EDTA+SB produced any advance crystallographic maturity at the interface. High crosslinking parameters and conformational changes in proteins in PA-treated specimens indicated, indirectly, that the first remineralization is intrafibrillar.

Polycarboxylated microfillers incorporated into light-curable resin-based dental adhesives evoke remineralization at the mineral-depleted dentin

This study aimed at evaluating the remineralizing properties of three experimental light-curable resin-based dental adhesives containing tailored polycarboxylated microfillers. A co-monomers blend was firstly formulated and then mixed with each of the following microfillers: polycarboxylated bioactive glass (PBAG), polycarboxylated calcium silicates (PCS), and polycarboxylated calcium silicates-doped brushite (PDP). The three experimental and a filler-free control resins were applied onto 10% orthophosphoric acid treated dentin discs and light cured. The specimens were soaked in artificial saliva (AS) for 3, 7, and 14 days. Dentin mineral variation was monitored using attenuated total reflection-Fourier transform infrared (ATR-FTIR) and Raman spectroscopy. Confocal laser scanning microscopy (CLSM) was employed to observe the ultra-morphology/nanoleakage along the resin–dentin interface. The bonding ability and the durability of the resin–dentin bonds were investigated through microtensile bond strength (μTBS) test. ATR-FTIR and Raman showed a significant increase of the mineral matrix area ratio and phosphate peak intensity in specimens treated with the experimental resins within 14 days (p < 0.05). No significant increment of minerals was found in untreated specimens or specimens treated using the control filler-free resin (p > 0.05). Dentin treated using PBAG or PCS exhibited higher level of remineralization than the specimens in PDP group. CLSM showed reduction in nanoleakage, although the remineralization of the hybrid layer induced a significant drop in the μTBS after 3-month storage (p < 0.05). The experimental resin-based dental adhesives containing bioactive microfillers remineralize the resin–dentin interfaces when in intimate contact with biological fluids.

Enamel white spot lesions can remineralise using bio-active glass and polyacrylic acid-modified bio-active glass powders

ObjectiveTo evaluate the potential of bio-active glass (BAG) powder and BAG containing polyacrylic acid (PAA-BAG) to remineralise enamel white spot lesions (WSL). Methods32 human enamel samples with artificial WSLs were assigned to 4 experimental groups (n=8); (a) BAG slurry, (b) PAA-BAG slurry, (c) “standardised” remineralisation solution (positive control) and (d) de-ionised water (negative control). Mechanical properties of enamel were assessed using surface and cross-section Knoop microhardness. Micro-Raman spectroscopy in StreamLine™ scan mode was used to scan lesion cross-sections. The intensity of the Raman phosphate peak at 959cm−1 was fitted and measured producing depth profiles analysed using a double-step fitting function. A further 20 samples (n=5) were used to obtain 3D images of surfaces using non-contact white light profilometry permitting measurement of lesion step height in relation to the sound enamel reference level, and to scan the lesion surface using scanning electron microscopy (SEM). Data were analysed statistically using one-way ANOVA with Tukey's HSD post-hoc tests. ResultsBAG, PAA-BAG and the remineralisation solution exhibited statistically significantly higher surface and cross-section Knoop microhardness compared to the negative control. Micro-Raman spectroscopy detected significantly higher phosphate content within the treated groups compared to the negative control group. Lesions’ depth was not significantly reduced. SEM images revealed mineral depositions, with different sizes and shapes, within BAG, PAA-BAG and the positive control groups. ConclusionBAG and PAA-BAG surface treatments enhance enamel WSL remineralisation, assessed by the resultant improved mechanical properties, higher phosphate content and morphological changes within the artificial lesions.

Phosphocreatine resynthesis during recovery in different muscles of the exercising leg by 31P‐MRS

To investigate the high-energy phosphate metabolism by (31) P-nuclear magnetic resonance spectroscopy during off-transition of exercise in different muscle groups, such as calf muscles and biceps femoris muscles, seven male long-distance runners (LDR) and nine untrained males (UT) performed both submaximal constant and incremental exercises. The relative exercise intensity was set at 60% of the maximal work rate (60%W max) during both knee flexion and plantar flexion submaximal constant load exercises. The relative areas under the inorganic phosphate (Pi ) and phosphocreatine (PCr) peaks were determined. During the 5-min recovery following the 60%W max, the time constant for the PCr off-kinetics was significantly faster in the plantar flexion (LDR: 17.3 ± 3.6 s, UT: 26.7 ± 6.7 s) than in the knee flexion (LDR: 29.7 ± 4.7 s, UT: 42.7 ± 2.8 s, P < 0.05). In addition, a significantly faster PCr off-kinetics was observed in LDR than in UT for both exercises. The ratio of Pi to PCr (Pi /PCr) during exercise was significantly lower during the plantar flexion than during the knee flexion (P < 0.01). These findings indicated that the calf muscles had relatively higher potential for oxidative capacity than that of biceps femoris muscles with an association of training status.

Exercise efficiency is reduced by mitochondrial uncoupling in the elderly

A reduction in exercise efficiency accompanies ageing in humans. Here we evaluated the impact of changes in the contractile-coupling and mitochondrial-coupling efficiencies on the reduction in exercise efficiency in the elderly. Nine adult (mean, 38.8 years old) and 40 elderly subjects (mean, 68.8 years old) performed a cycle ergometer test to measure O2 uptake and leg power output up to the aerobic limit ( ). Reduced leg power output per unit O2 uptake was reflected in a drop in delta efficiency (εD) from 0.27 ± 0.01 (mean ± SEM) in adults to 0.22 ± 0.01 in the elderly group. Similar declines with age were apparent for both the leg power output at and the ATP generation capacity (ATPmax) determined in vivo using (31)P magnetic resonance spectroscopy. These similar declines resulted in unchanged contractile-coupling efficiency values (εC) in the adult (0.50 ± 0.05) versus the elderly group (0.58 ± 0.04) and agreed with independent measures of muscle contractile-coupling efficiency in human quadriceps (0.5). The mitochondrial-coupling efficiency calculated from the ratio of delta to contractile-coupling efficiencies in the adults (εD/εC = 0.58 ± 0.08) corresponded to values for well-coupled mitochondria (0.6); however, εD/εC was significantly lower in the elderly subjects (0.44 ± 0.03). Conversion of ATPmax per mitochondrial volume (ATPmax/Vv[mt,f]) reported in these groups into thermodynamic units confirmed this drop in mitochondrial-coupling efficiency from 0.57 ± 0.08 in adults to 0.41 ± 0.03 in elderly subjects. Thus, two independent methods revealed that reduced mitochondrial-coupling efficiency was a key part of the drop in exercise efficiency in these elderly subjects and may be an important part of the loss of exercise performance with age.

Characterizing and Identifying Incipient Carious Lesions in Dental Enamel Using Micro-Raman Spectroscopy

Early detection of dental caries is vital if improved patient outcomes are to be achieved by reversal of the demineralization process. Current techniques used by dentists for identifying carious lesions are effective in identifying more advanced lesions, but do not have sufficient sensitivity and specificity to detect them at the earliest stages. This study focused on characterizing the growth of incipient carious lesions in vitro using micro-Raman spectroscopy. The incipient carious lesions were grown on the buccal faces of human molars by controlled exposure to lactic acid. Lesions were cross-sectioned to expose the subsurface body of the lesion and then examined using micro-Raman spectroscopy. The intensity of the phosphate peaks in the Raman spectra was found to differ significantly between healthy enamel and the demineralized region of the lesions. The sensitivity of the phosphate peaks to the degree of demineralization was observed by taking a series of spectra over the cross section of the lesions. This revealed that the body of the lesion is highly demineralized, but in a narrow surface region (up to 10 µm) there is little demineralization. All the phosphate peaks were found to be sensitive to the degree of demineralization; however, changes in the intensity of the pronounced phosphate peak at 961 cm^–1 offer the most promise for identifying lesions. The results indicate that micro-Raman spectroscopy has both the sensitivity and selectivity to identify incipient carious lesions, but the presence of a surface layer with a relatively high mineral content could complicate the analysis.

Appraisal of gastropod shell as calcium ion source for phosphate removal and recovery in calcium phosphate minerals crystallization procedure

On the basis of the perspective of wastes recycling and minimization of cost of phosphate removal via the chemical precipitation procedure, the present studies evaluated the ability of waste biogenic Gastropod shell to serve as a source of Ca2+ ion in the removal and recovery of phosphate in calcium phosphate mineral (CPM) crystallization procedure. Phosphate removal efficiency values >99% was achieved when 2g of snail shell was used in water of phosphate concentrations ranging between 25 and 1000mg/L. pH and ionic strength exhibited no influence on the phosphate removal efficiency. Concomitant removal of phosphate and organic matter revealed that phosphate removal efficiency was not impacted but the magnitude of the organics removed increased with increase in the organic load. Kinetic analysis showed that second order kinetic model gave a better description of the process. XRD analysis of the derived sludge showed the crystallinity and peaks synonymous with the presence of whitlockite, hydroxyapatite and calcium phosphate hydrate. The FTIR of the sludge showed the disappearance of some naturally occurring functional groups and the appearance of phosphate peaks which confirmed the formation of CPM.

The Distribution of Carbonate in Enamel and its Correlation with Structure and Mechanical Properties.

The correlation of carbonate content with enamel microstructure (chemical and crystal structure) and mechanical properties was evaluated via linear mapping analyses using Raman microspectroscopy and nanoindentation. Mappings started at the outer enamel surface and ended in the inner enamel near the dentin-enamel junction (DEJ) in lingual and buccal cervical and cuspal regions. The carbonate peak intensity at 1070 cm-1 gradually increased from outer to inner enamel. Moreover, the phosphate peak width, as measured by the full width at half maximum (FWHM) of the peak at 960 cm-1, also increased, going from ~9 cm-1 in outer enamel to ~13 cm-1 in enamel adjacent to the DEJ, indicating a decrease in the degree of crystallinity of hydroxyapatite from outer to inner enamel. In contrast, Young's modulus decreased from 119±12 to 80±19 GPa across outer to inner enamel with a concomitant decrease in enamel hardness from 5.9±1.4 to 3.5±1.3 GPa. There were also significant correlations between carbonate content and associated crystallinity with mechanical properties. As carbonate content increased, there was an associated decrease in crystallinity and both of these changes correlated with decreased modulus and hardness. Collectively, these results suggest that enamel carbonate content and the associated change in the crystal structure of hydroxyapatite, i.e. degree of crystallinity, may have a direct effect on enamel mechanical properties. The combination of Raman microspectroscopy and nanoindentation proved to be an effective approach for evaluating the microstructure of enamel and its associated properties.