Phosphate Intensity Research Articles

Human “barcode”: Link between phosphate intensity changes in human enamel and light microscopy record of accentuated lines

Disruption of metabolic processes during human enamel mineralization may result in the appearance of accentuated lines in enamel. These accentuated lines in the enamel relate to stress events that were experienced and overcome in early ontogenetic phases. Accentuated lines are visible in transmitted light microscopy as dark areas. However, their appearance is variable even within single tooth. The objective of this study is to analyze the distribution of phosphate in human enamel with a focus on accentuated stress lines by Raman microscopy. Transmitted light microscopy and Raman microscopy records of 15 human teeth (11 samples from archaeological excavations, 4 from recent population) were compared, using visual evaluation and statistical methods (correlation of pixel light intensities in the microscopic images). The data obtained by Raman microscopy suggests a relationship between low phosphate content (signal at 960 cm−1) and accentuated stress lines in human enamel.

Chitosan improves the durability of resin-dentin interface with etch-and-rinse or self-etch adhesive systems.

Degradation of the dentin-resin interface can occur due to hydrolysis of exposed collagen, resulting in reduced bond strength. This study assessed the effect of dentin treatment with chitosan combined with an etch-and-rinse or self-etch adhesive system on improvement of bond strength and preservation of the interface durability. Methodology Enamel was removed from 80 molars and the teeth were divided into two groups: without chitosan (control) or with 2.5% chitosan gel (1 min). They were further subdivided into two subgroups according to the adhesive system: etch-and-rinse or self-etch. Dentin was restored using a composite resin. Half of the specimens from each restored group were subjected to interface aging and the remaining specimens were used for immediate analysis. The specimens were sectioned and subjected to microtensile bond strength (µTBS) test (n=10), chemical composition testing using Fourier-transform infrared (FTIR) spectroscopy (n=4) and energy-dispersive spectroscopy (EDS) (n=5), and morphological analysis of the adhesive interface using scanning electron microscopy (SEM) (n=5). Data were analyzed using three-way ANOVA.Results Chitosan improved the µTBS of the adhesive interface when compared with the control group (p=0.004). No significant differences were observed in dentin adhesion between the adhesive systems (p=0.652). Immediate µTBS was not significantly different from that after 6 months (p=0.274). EDS and SEM did not show significant differences in the chemical and structural composition of the specimens. FTIR showed a decrease in the intensity of phosphate and carbonate bands after using chitosan.Conclusions Dentin treatment with chitosan combined with an etch-and-rinse or self-etch adhesive system improved the immediate and preserved the 6-month bond strength of the adhesive interface.

Effects of residues of triple superphosphate on the quantity-intensity relationships of fresh phosphate in some soils from Brazil and Colombia

Isotopic exchange of phosphate was investigated in soils which had received 0–176 kg P ha−1 as triple superphosphate in the field. The soils were kaolinitic oxisols from near Manaus, Brazil, and Pescador, Colombia, and an allophanic andept with much organic matter from Popayan, Colombia. When fresh phosphate was added to these soils in the laboratory the residues of triple superphosphate decreased the intensity of phosphate in the liquid phase that was associated with a specific quantity of exchangeable phosphate. However, residues of triple superphosphate increased phosphate taken up by maize at Manaus. Residues did not cause this effect in soils from Colombia in which the major minerals were halloysite and imogolite. The cause of the anomalous results in kaolinitic soils may be that in the field, during long contact between soil and phosphate, the latter penetrated into the mineral crystal so that, although it maintained adequate concentration for crops, exchange of the residues was slower in the laboratory than exchange of the fresh phosphate that was added for the measurements. In the andept the effect may have been caused by strong sorption of fertilizer phosphate onto hydrous oxides of aluminium released from organic matter by lime. The results indicated that although short term exchange data may be useful to differentiate phosphate sorption characteristics in untreated soils they may not, at least in some soils, represent long term behaviour of phosphate residues in relation to phosphate taken up by crops.

Effects of initial phosphate intensity and sorption or buffering capacity of soil on fertilizer requirements of different crops grown in pots or in the field

SummaryRates of added P required for maximum yields of ryegrass grown in pots and of field tobacco and maize were related to functions of P intensity (I) and capacity (AQ/AI, or C) in soils. It was found that log I alone was negatively correlated with optimum fertilizer for ryegrass and tobacco, but not for maize. Capacity alone had little relationship with P requirements of tobacco but was significantly correlated, although having opposite effects, with those of ryegrass (positive) and maize (negative). Optimum fertilizer rates for all crops were best accounted for by multiple regressions including intensity and a capacity term together, using log C when P requirements were increased (ryegrass in pots, R2 = 0.94) or √C when they were decreased by increasing capacity (field tobacco, R2= 0.96; and maize, R2 = 0.98). Inclusion of both capacity terms with log I in regression was of no advantage with ryegrass and tobacco, but with maize all three terms contributed significantly to the correlation, log C tending to increase and √C to decrease fertilizer needs.

Experiments on the effects of phosphate applied to a Buganda soil: II. Field experiments on the response curve to triple superphosphate

SUMMARYA sigmoid curve for response to superphosphate has been demonstrated in field experiments in a Buganda red clay loam. There was evidence that the curve was abnormal; with small dressings of triple superphosphate yield of cotton and beans, and their phosphorus uptake, were decreased, but these characters were increased with larger dressings. Heavy dressings, from 4 to 16 cwt triple superphosphate, increased yield of these crops. Similar effects were observed with maize during growth and maturity was advanced, but final yield of grain was not affected by applied phosphate. The suggestion is made that in a long growing period the maize was able to absorb adequate phosphorus, even though the phosphate intensity in the soil was low, to achieve its potential yield.