Deofix, N,N',N"-tris(dihydroxyphosphorylmethyl)-1,4,7-triazacyclononane, is a high-affinity, high-specificity chelator for first transition series cations such as iron, zinc, manganese, and copper. A 1% solution in 50% ethanol was found to be significantly better at reducing underarm malodor than a solution of 0.3% Triclosan in 50% ethanol. Compared to a 50% alcohol control, Deofix was found to produce a significant reduction in malodor for at least 48 hours. Deofix appears to work by reducing the concentration of first transition series metal ions below the levels needed for microbial cell reproduction and by inhibiting oxidative processes by interfering with catalytic formation of free radicals. Deofix has very low levels of toxicity when measured via a number of screening techniques.
A reliable high-performance liquid chromatography (HPLC) method was developed for the simultaneous determination of 13 dye intermediates, including benzenediamines, aminophenols, benzenediols, naphthalenediol, and diaminopyridine, in oxidative hair dyes. Samples were extracted with 50% ethanol by adding sodium dithionite to prevent oxidation. The influences of buffer type, buffer pH, ion-pair reagent, and elution gradient were studied. A C18 column with aqueous compatibility and acetonitrile-citric acid mobile phase system (pH 2.6) with sodium 1-octanesulfonate as ion-pair reagent were selected for the separation of target compounds. Detection was performed by a diode array detector, (DAD) and two different wavelengths (280 and 331 nm) were used for quantification. Results showed that 13 dye intermediates got good separation within 25 min. The detection limits of these compounds were in the range of 0.2-2 mg/l. The calibration curves were linear within 2-500 mg/l with 0.999 as a typical correlation coefficient. The recoveries of target compounds in hair dyes ranged from 81.7% to 102.0% with four addition levels. The method described was validated by five different laboratories and successfully applied to the analysis of commercial oxidative hair dyes.
The 21-day cumulative irritation test for assessing the irritancy of topical products and chemicals is a venerable procedure that appears to have become the gold standard for manufacturers. Berger and Bowman in 1982 (1) showed that reducing the exposure to 14 days was less traumatic to the volunteers, less costly, less arduous, and did not affect reliability or the capacity to place the test agents in the proper rank order of irritancy. In the current study we compared (a) the 21-day cumulative irritation test, (b) the 14-day cumulative irritation test, and (c) the 14-day test with every-other-day patching. Additionally, ten-day, seven-day and four-day data from the 21-day test were compared. Forty-one subjects completed this study of six test materials. Two sets of patches were applied to each subject' lower back. One set had 21 consecutive applications of the test articles. The second set was applied, and removal of the test articles occurred Monday, Wednesday, and Friday for 14 days. The 21-day test fully differentiated the test materials from each other. Using only the first 14 days of the 21-day test also fully differentiated the test materials. Every-other-day patching rank ordered the test materials the same as the everyday patching, but full differentiation of the test materials was not obtained. We conclude that the 14-day cumulative irritancy test is as reliable and sensitive as the 21-day test, along with the obvious advantages in time, cost, and minimization of trauma to the test subjects.
Sixteen UV filters were simultaneously analyzed using the high-performance liquid chromatographic method. They were drometrizole (USAN Drometrizole), 4-methylbenzylidene camphor (USAN Enzacamene), menthyl anthranilate (USAN Menthyl anthranilate), benzophenone-3 (USAN Oxybenzone), benzophenone-8 (USAN Dioxybenzone), butyl methoxydibenzoylmethane (USAN Avobenzone), ethylhexyl triazone (USAN Octyl triazone), octocrylene (USAN Octocrylene), ethylhexyl dimethyl p-aminobenzoic acid (USAN Padimate O), ethylhexyl methoxycinnamate (USAN Octinoxate), p-aminobenzoic acid (USAN Aminobenzoic acid), 2-phenylbenzimidazole-5-sulfonic acid (USAN Ensulizole), isoamyl p-methoxycinnamate (USAN Amiloxate), and recent UV filters such as diethylhexyl butamidotriazone (USAN Iscotrizinol), methylene bis-benzotriazolyl tetramethylbutylphenol (USAN Bisoctrizole), and terephthalylidene dicamphor sulfonic acid (USAN Ecamsule). Separation of the UV filters was carried out in a C(18) column with a gradient of methanol-phosphate buffer, and the UV detection was at 300, 320, or 360 nm without any interference. The limits of detection were between 0.08 and 1.94 μg/ml, and the limits of quantitation were between 0.24 and 5.89 μg/ml. The extracting solvent for the UV filters was methanol, except for ethylhexyl triazone and methylene bis-benzotriazolyl tetramethylbutylphenol, which were prepared with tetrahydrofuran. The recoveries from spiked samples were between 94.90% and 116.54%, depending on the matrixes used. The developed method was applied to 23 sunscreens obtained from local markets, and the results were acceptable to their own criteria and to maximum authorized concentrations. Consequently, these results would provide a simple extracting method and a simultaneous determination for various UV filters, which can improve the quality control process as well as the environmental monitoring of sunscreens.
Numerous strategies have been proposed to evaluate melanosome transfer. Methods allowing quantitative measurements of this transfer in human normal cellular models, however, are very few and often require extremely specialized devices that are expensive and difficult to use. As a part of the melanosome-specific membrane-bound glycoprotein, Pmel 17 is released from the melanosome membrane by ectodomain shedding. We reasoned, therefore, that it should be possible to evaluate melanosome transfer by quantifying this "soluble" Pmel 17. The Pmel 17 ELISA assay developed permits a detection of 10 to 1000 ng/ml of this glycoprotein in human normal melanocyte-keratinocyte co-culture media. As expected, niacinamide, a well-known melanosome transfer inhibitor, significantly reduced the Pmel 17 quantities found in the culture media. This validated our experimental design. We then used our model to show that a whitening cosmetic active compound, i.e., an Alaria esculenta extract, can (at least in part) enable a significant decrease in the melanosome transfer to produce a lightening effect without affecting melanin production. This research provides a simple and efficient method to quantify melanosome transfer in a human normal co-culture model. It is a particularly useful tool with which to facilitate the development of new active whitening compounds.
D&C red no. 17 is approved for use in externally applied drug and cosmetic applications, in amounts consistent with good manufacturing practice. Concerns about the safety of the color additive (1-[4-phenylazophenylazo]-2-napthol (PAN) is the primary color constituent) have been raised due to potential metabolic cleavage of PAN to yield 4-aminoazobenzene. (14)C-PAN was applied in a commercially available suntan vehicle containing D&C red no. 17 to viable porcine and non-viable (cadaver) human skin in flow-through diffusion cells. At the end of 24 h, unabsorbed material was removed from the skin and some cells were allowed to continue for an additional 48 h. In human skin, 0.07% and 0.17% of the applied dose were absorbed into the receptor fluid after 24 and 72 h, respectively. At the end of 24 h, 12.5% of the applied dose remained in the skin, which did not decrease at 72 h. When PAN was applied to viable porcine skin for 24 h, 0.3% of the applied dose was absorbed and 12.7% remained in the skin. Additional studies to simulate short-term exposure were completed with PAN applied to the skin for only 15 min, and absorption was determined for 24 and 72 h. These studies in human cadaver skin found 0.02% and 0.08% of the applied dose in the receptor fluid after 24 and 72 h, respectively. Viable porcine skin studies with the 15-min application resulted in receptor fluid values of 0.1% of the applied dose after 24 h. Lipophilic receptor fluids composed of the non-ionic surfactant Volpo 20 at wt% concentrations of 1%, 3%, or 6% in water did not increase partitioning of PAN from the skin into the receptor fluid. No metabolism of PAN was found in viable porcine skin when examined by HPLC. In conclusion, skin absorption of PAN from a commercially available suntan product was low.
J. Cosmet. Sci., 60, 509–518 (September/October 2009)
The effect of the anteiso-branch moiety of 18-MEA (18-methyleicosanic acid) to create a persistent hydrophobicity of alkaline-color-treated weathered hair treated with 18-MEA/SPDA (stearoxypropyldimethylamine) was investigated by comparing a straight-chain fatty acid (n-heneicosanoic acid, n-HEA) and an iso-branch fatty acid (19-methyleicosanic acid, 19-MEA) with the anteiso-branch fatty acid (18-MEA), using dynamic contact angle measurements, quantification of 18-MEA by LC/MS, and temperature controlled atomic force microscopy (AFM). The dynamic contact angle measurements indicated that the anteiso-branch moiety of 18-MEA is critical for the creation of a persistent hydrophobicity to alkaline-color-treated weathered hair. The temperature-controlled AFM investigations revealed that the anteiso-branch moiety of 18-MEA in the 18-MEA/SPDA system produces a persistent hydrophobicity to alkaline-color-treated weathered hair by providing higher fluidity to the upper region of the 18-MEA/SPDA layer.
The use of computational chemistry techniques via molecular modeling software provides additional support to the hair surface model by Negri et al. (1) and refines the thickness of the 18-methyl eicosanoic acid (18-MEA) lipid layer attached by thioester linkages to an ultra-high-sulfur protein (UHSP) at 1.08 ± 0.2 nm. This value compares favorably to the thickness of that same layer from X-ray photoelectron spectroscopy (XPS) measurements by Ward et al. (2) at 1.00 ± 0.5 nm on Soxhlet-extracted wool. The model clarifies that the results of Ward et al. via XPS are not an artifact of high vacuum (3), but due to relaxation of the 18-MEA structure onto the wool protein backbone as suggested by Zahn et al. (4). In this molecular model, 18-MEA is attached to beta sheets of an UHSP via thioester linkages as suggested by Negri et al. in their 1993 study (15) and by earlier work by Evans et al. (5). The beta sheets of this model provide an intersheet spacing of 0.7 nm and a beta sheet density of 1.42 g/cm(3) compared with Allworden membrane fractions that varied from 1.39 to 1.54 g/cm(3) (6).
The effects of the removal of 18-MEA on the dynamic contact angle (advancing contact angle and receding contact angle) and friction force (friction force microscopy (FFM)) were examined in the present study. Chemically untreated hair tresses formed more finely ordered bundles, with the fibers aligned more parallel to each other, in the wet state, and lying flat and aligned parallel to each other in the dry state. Hair tresses in which 18-MEA had been removed by potassium t-butoxide treatment formed coarser tangled bundles and were aligned in a disorderly manner in the wet state, causing the hair to become entangled and disorderly in the dry state. This was because the 18-MEA-removed hair fibers adhered to each other and were not easy to realign in the wet state. The distorted part of the bundle dried faster and the tress shape was eventually fixed in the entangled shape. One role of 18-MEA is to allow hair fibers to lie flat and parallel with respect to each other in the wet state by providing relatively high receding contact angles and low surface friction. Hair alignment in the dry state is directly affected by hair alignment in the wet environment, particularly in the case of damaged hair.
J. Cosmet. Sci., 60, 31–44 (January/February 2009)
A technology for the deposition of a persistent hydrophobicity to alkaline-color-treated weathered hair surfaces using 18-MEA (18-methyleicosanoic acid) is presented. Two approaches were examined in order to make 18-MEA bind tightly to the alkaline-color-treated weathered hair surface. One was to apply 18-MEA as an acid form and the other was to apply 18-MEA as a salt or complex. It was found that the combination of 18-MEA with specific cationic surfactants [stearoxypropyldimethylamine (SPDA) and docosyldimethylamine (DSDA)] makes the alkaline-color-treated weathered hair surface hydrophobic and that its hydrophobicity is maintained even after shampooing. Characterization of adsorbed layers of 18-MEA/SPDA on a mica surface, as a possible hydrophilic surface model, was performed using atomic force microscopy (AFM) and angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The results revealed that 18-MEA/SPDA formed a layer with high wear resistance, with an alkyl chain, the hydrophobic moiety, oriented at an angle of around 25° to the air interface.
Various methods for the determination of kojic acid (KA), a skin-whitening agent, have been reported by high-performance liquid chromatography (HPLC). In this study, the concentration of KA in a skin-whitening cosmetic was analyzed by HPLC with ultraviolet detection (380 nm) after pre-column derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) in order to improve the sensitivity. The HPLC column was 150 mm x 3.0 mm i.d., containing 5 microm particles of C18 packing material. The mobile phase was prepared by the addition of acetonitrile (550 ml) to 450 ml of Milli-Q water containing trifluoroacetic acid (0.1 v/v%). The samples were eluted from the column at room temperature at a flow rate of 0.35 ml/min. The retention time of NBD-KA was 7.8 min. A standard curve was obtained after derivatization with NBD-F in borate buffer (pH 9.0) at 40 degrees C for 7 min. The calibration plot was linear, in the range of 0.25-5 microg/ml with an r2 value of 0.9982, and the lower limit of detection was 0.06 microg/ml (at a signal-to-noise ratio of 3:1; absolute amount of 0.4 ng/20 microl injection). The coefficient of variation was less than 9.6%. It was found that the amount of KA in a skin-whitening cosmetic was 237 +/- 14 microg/ml (range: 219-255 microg/ml). Recovery in addition-recovery tests was within the range of 83.4% to 98.1%.
Hinokitiol, a potent, broad-spectrum antibacterial agent, is a component of various personal care products. In this study, the concentration of hinokitiol in skin lotion was analyzed by means of high-performance liquid chromatography-ultraviolet detection (380 nm) after precolumn derivatization with 4-fluoro-7-nitro-2,1, 3-benzoxadiazole (NBD-F). A standard curve was obtained after derivatization of the authentic compound with NBD-F in borate buffer (pH 9.0) at 60°C for 10 min. The retention time of NBD-hinokitiol was 7.2 min. The calibration plot was linear in the range of 0.2 to 4 mg/ml with an r2 value of 0.9985, and the lower limit of detection was 0.05 μg/ml (at a signal-to-noise ratio of 3, absolute amount of 0.33 ng/20 μl injection). The coefficient of variation was less than 9.4%. It was found that the amount of hinokitiol in the tested skin lotion was 194 ± 14 μg/ml (range: 180-212 μg/ml). Recovery in addition-recovery tests was within the range of 84.5% to 98.0%. This system is simple, sensitive, and convenient, and should be suitable for routine quality assessment of personal care products containing hinokitiol.
The application of surface specific x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) will be shown to be an effective means for the elucidation of hair fiber surface chemistry and structure. Example studies of bleaching and fiber conditioning treatments are discussed. The bleached fiber surface is found to become more hydrophilic due to the loss of the naturally occurring hydrocarbon overlayer and oxidation of surface functional groups as a result of bleaching. Comparison between generic bleaching regimens illustrates the importance of increased pH and the presence of surfactant for effective treatment. Adsorption of conditioning diester quat and dimethicone molecules reintroduces a hydrophobic like surface layer on the hair fiber. Spectroscopic data indicated a segregated adsorption structure of the chemically different conditioning molecules. Electron microscope images of the conditioned hair shows a smooth uniform surface.
Literature dealing with the mechanisms of hair breakage in combing and brushing published so far has been reviewed as a background for the critical evaluation of the method and data analysis of the paper "Statistical Analysis of Hair Breakage. II" by Evans and Park (1). Accumulated knowledge about hair breakage in these grooming processes indicates that hair breakage in combing and brushing results from tangling, looping, knotting, and impact loading. Fatiguing, though responsible for some weakening of the fiber in the grooming process, it is unlikely to be a significant factor in hair breakage in combing and brushing.
In previous studies, 4-hydroxy-5-methyl-3[2H]-furanone (HMF) was shown to have potent antioxidative and antimelanogenic effects, suggesting its potential use as a depigmenting agent. The present study investigated its mechanism of action on murine melanoma B16F10 cells stimulated by theophylline, an activator of the cyclic AMP/protein kinase A signaling leading to tyrosinase gene expression. When the cells were stimulated with theophylline, there were dose-dependent increases in cellular tyrosinase protein content and melanin formation, as expected. HMF inhibited the theophylline-stimulated melanin formation as effectively as arbutin, one of the most widely used depigmenting agents in cosmetics. HMF appeared to reduce tyrosinase mRNA and protein content in the cells stimulated by theophylline, indicating it inhibited tyrosinase gene expression. HMF also effectively inhibited tyrosinase-catalyzed melanin formation from dihydroxyphenylalanine in the cells as well as in vitro. Therefore, the antimelanogenic effects of HMF were best explained by a dual mechanism inhibiting tyrosinase gene expression and the enzyme activity of pre-existing tyrosinase.
This in vitro study was performed to elucidate the reaction mechanism of sodium fluoride (NaF), which is added to tooth-bleaching agents to lessen the adverse effect of hydrogen peroxide (H2O2) on teeth. Both hydroxyapatite (HAP) and dihydrated dicalcium phosphate (DCPD), model substances for dental hard tissues, dissolved easily in a simple H2O2 solution. In the H2O2/NaF solutions, however, fluorine compounds that could not be identified by X-ray diffraction (XRD) due to the smallness of the products were formed on the surface of the HAP. X-ray photoelectron spectroscopy (XPS) studies demonstrated that fluoridated hydroxyapatite (FHAP) was formed on HAP, and that calcium fluoride (CaF2) formation was accelerated by increasing the concentrations of fluorine and H2O2 along with the partial dissolution of HAP. In H2O2/NaF solution, DCPD also transformed easily to FHAP and CaF2, which are favorable to the remineralization process on the tooth surface. Thus, the mechanism of NaF was elucidated, and its use together with H2O2 for tooth bleaching was proved to be effective. Methodologically, the XPS two-dimensional plot made it possible for the first time to directly estimate the ratio of FHAP and CaF2 in the reaction products, in contrast to the conventional wet-analytical method, which is simply based on the difference in solubility of the two components.
With regard to the increase of human life expectancy, interest for topical treatments aimed to counteract skin aging is still growing. Hence, research for bioactive compounds able to stimulate skin fibroblast activity is an attractive topic. Having previously described the effects of a new methanol yeast extract on growth and metabolic activity of Saccharomyces cerevisiae, we studied its effects on 3T3 fibroblasts to evaluate its potential antiaging property. This investigation demonstrates that this extract increases proliferation as well as migration of 3T3 cells and decreases their entrance in senescence and apoptosis phases. Altogether, these results open new perspectives for the formulation of innovative antiaging topical treatments.
In 2009, the U.S. Food and Drug Administration (FDA) published lead (Pb) content results from a small survey of 20 tube lipsticks with red shades using a validated inductively coupled plasma-mass spectrometric (ICP-MS) method developed by FDA chemists. The study was prompted by a media report suggesting that potential exposure to lead from lipsticks under conditions of ordinary use might be harmful. The FDA has since investigated the lead content of tube lipsticks by conducting an expanded survey that included a variety of shades and manufacturers, at varying prices. The purposes of the expanded survey were to ascertain the levels of lead in lipsticks sold on the U.S. market, to identify any categories of lipstick with elevated levels of lead, and to compare the results to those from the initial small survey. Four hundred lipsticks available on the U.S. market in the spring of 2010 were tested for total lead content using the FDA's validated method. The analyses were performed by a private laboratory contracted by the FDA. The maximum lead level found was 7.19 mg Pb/kg. Thirteen of the 400 lipsticks were found to contain levels greater than 3.06 mg Pb/kg, the highest amount found in the initial survey. The average lead concentration found in the expanded survey was 1.11 mg Pb/kg, which was very close to the average of 1.07 mg Pb/kg found in the initial survey. Some statistically significant associations between lead level and parent company were found. The contract requirements, testing procedures, and findings from the expanded survey are described here.
Our goal was to study the effect of Gp₄G on skin tissues and unravel its intracellular action mechanisms. The effects of Gp₄G formulation, a liposomic solution of Artemia salina extract, on several epidermal, depmal, and hair follicle structures were quantified. A 50% increase in hair length and a 30% increase in the number of papilla cells were explained by the changes in the telogen/anagen hair follicle phases. Increasing skin blood vessels and fibroblast activation modified collagen arrangement in dermal tissues. Imunohistochemical staining revealed expressive increases of versican (VER) deposition in the treated animals (68%). Hela and fibroblast cells were used as in vitro models. Gp₄G enters both cell lines, with a hyperbolic saturation profile inducing an increase in the viabilities of Hela and fibroblast cells. Intracellular ATP and other nucleotides were quantified in Hela cells showing a 38% increase in intracellular ATP concentration and increases in the intracellular concentration of tri- , di- , and monophosphate nucleosides, changing the usual quasi-equilibrium state of nucleotide concentrations. We propose that this change in nucleotide equilibrium affects several biochemical pathways and explains the cell and tissue activations observed experimentally.
It would be useful to develop a surrogate for animal skin, which could be use to predict flux through human skin. The fluxes (and physicochemical properties) of sunscreens and other compounds from propylene glycol (PG):water (AQ), 30:70, through human skin have previously been reported. We measured the fluxes of several of those sunscreens and other compounds from PG:AQ, 30:70, through silicone membrane and fit both sets of data to the Roberts-Sloan (RS) equation to determine any similarities. For both sets of data, the fluxes were directly dependent on their solubilities in a lipid solvent [octanol (OCT), in this case] and in a polar solvent (PG:AQ, 30:70, or AQ in this case) and inversely on their molecular weights. The fit of the experimental (EXP) fluxes through human skin in vivo to RS was excellent: r2 = 0.92 if the vehicle (VEH) PG:AQ, 30:70 was the polar solvent (RS1) or r2 = 0.97 if water was the polar solvent (RS2). The fit of the EXP fluxes through silicone membrane to RS was good: r2 = 0.80 if the VEH PG:AQ, 30:70, was the polar solvent (RS1) or r2 = 0.81 if water was the polar solvent (RS2). The correlations between their EXP fluxes through human skin in vivo and their EXP fluxes through silicone membrane were good (r2 = 0.85). In addition, the correlation between EXP fluxes from PG:AQ, 30:70, through human skin in vivo and their fluxes calculated from the coefficients of the fit of solubilities, molecular weights and fluxes from water through silicone membranes from a previous n = 22 database to RS was even better (r2 = 0.94). These results suggest that flux through human skin can be calculated from flux through a silicone membrane.
Natural essential lavender oil was obtained by steam distillation from the flowering plants. The phase behavior of a system of natural lavender oil, distilled water, and two stabilizers was investigated. The stabilizers that were used were tetraethyleneglycol lauryl ether (Laureth 4) and polyoxyethylen (20) sorbitan mono-oleate (Tween 80). For the first system (water, lavender oil, Laureth 4), the phase diagram shows an area of lamellar liquid crystal formed along the water-Laureth 4 axis. It solubilized up to 12% per weight of the lavender oil. The system formed one isotropic solution. The phase diagram for the second system (water, lavender oil, Tween 80) shows a small area of hexagonal liquid crystal that solubilized a maximum of only 3% of the lavender oil. The system shows two isotropic phases. Evaporation studies were done for the isotropic solutions in both systems. The results provided essential information about the behavior of lavender oil during evaporation.
In this work we have explored capillary adhesion between hair fibers treated with different types of oils. With coconut, olive, and sunflower oils the capillary adhesion was found to decrease with time, but not with mineral oil. Application of heat reduced the capillary adhesion further for coconut and sunflower oils. Again, this was not observed with mineral oil. Based on an earlier study, where coconut oil was found to penetrate hair while mineral oil was unable to do so, it was hypothesized that the reduction in capillary adhesion resulted from the penetration of oil into the fiber, leaving a thinner oil film on the surface. Such a reduction in capillary adhesion can be explained by changes in Laplace pressure and in the areas of liquid bridges formed between the fibers. The thinning of oil films on the surface of hair has been confirmed independently by goniophotometric measurements on single hair fibers treated with coconut, sunflower, and mineral oils. Thick films of oil (thicker than approximately 0.5 microm) are known to mask the scale structure. As the oil is absorbed into the hair, the film thins with time and application of heat, and the scale structure reappears. This change can be conveniently determined by measuring the scale angle, using the well established goniophotometric protocol. The agreement between the two methods supports the concept that the reduction in capillary adhesion between hair fibers is most likely due to thinning of oil films by absorption of oil into the hair.
This study intends to present Bradford assay as an alternative to Lowry test to quantify hair damage during combing or brushing. The protocol involves collecting hair fragments that are chipped away from hair during these abrasive treatments and quantitatively measuring the amount of protein using an analytical procedure to detect low amounts of proteins. This protein determination method involves the binding of Coomassie Brilliant Blue G-250 to hair protein (keratin). It is quite rapid and sensitive and less prone to interferences as the standard Lowry procedure. The latter is subject to interference from compounds such as lipids, cationic surfactants and EDTA, which are ingredients commonly used in hair care formulations and may lead to a false positive result. These drawbacks should be eliminated when using the so called Bradford method for hair protein quantitation. Our studies showed reproducible results for human hair protein and the developed color was stable for up to one hour. The data also show that virgin hair releases less protein than bleached hair. The amount detected for the former after combing ranges from 0.875 to 1.03 mg/g of hair and 4.85 to 5.35 mg/g of hair for the latter.
Our purpose was to apply a radiometric method to an abrasiveness evaluation in samples of silica and calcium carbonate used as an abrasive in a dentifrice, to help in a prudent selection of materials by dentifrice producers. The results of RDA (radioactive dentin abrasion) abrasiveness indices obtained for these compounds varied from 136 to 19. The relative standard deviations of these RDA results varied from 5.9% to 11.8%, showing a good precision in the method. Also, the results obtained indicated that the abrasiveness indices increase with the particle size of the material. A comparison between different abrasives with similar particle sizes showed that silica presents higher RDA values than calcium carbonate.