Lactic Acid Gel Research Articles

Functional properties of ultrasonically generated flaxseed oil-dairy emulsions

This study reports on the functional properties of 7% flaxseed oil/milk emulsion obtained by sonication (OM) using 20kHz ultrasound (US) at 176W for 1–8min in two different delivery formulae, viz., ready-to-drink (RTD) and lactic acid gel. The RTD emulsions showed no change in viscosity after sonication for up to 8min followed by storage up to a minimum of 9days at 4±2°C. Similarly, the oxidative stability of the RTD emulsion was studied by measuring the conjugated diene hydroperoxides (CD). The CD was unaffected after 8min of ultrasonic processing. The safety aspect of US processing was evaluated by measuring the formation of CD at different power levels. The functional properties of OM gels were evaluated by small and large scale deformation studies. The sonication process improved the gelation characteristics, viz., decreased gelation time, increased elastic nature, decreased syneresis and increased gel strength. The presence of finer sono-emulsified oil globules, stabilized by partially denatured whey proteins, contributed to the improvements in the gel structure in comparison to sonicated and unsonicated pasteurized homogenized skim milk (PHSM) gels. A sono-emulsification process of 5min followed by gelation for about 11min can produce gels of highest textural attibutes.

Solvent Exchange and Gelation Mechanism of Poly(l-lactic acid) Gel Formed by Complex Crystallization with Solvents

Abstract Poly(l-lactic acid) (PLLA) gels were formed by complex crystals (ε-crystals) with some solvents, such as N,N-dimethylformamide (DMF), and the solvent in the gel was exchanged to other solvents, such as water, by the immersion of the gel into the solvent. Although X-ray diffraction patterns of the gels indicated that the ε-crystals formed in DMF changed to α-crystals, the structure formed by spherulites observed by polarizing microscopy showed no change by the solvent exchange. The gelation mechanism was proposed based in the experimental data.

Positive effects of local therapy with a vaginal lactic acid gel on dysuria and E.coli bacteriuria question our current views on recurrent cystitis

We tested the effect of vaginally applied lactic acid gel on symptoms and bacteriuria in acutely exacerbated recurrent Eschericia coli cystitis. Carnoy fixed samples of the morning urine from 20 women with a history of recurrent E.coli cystitis were prospectively investigated for bacteriuria using fluorescence in situ hybridization (FISH). In 11/20 women with acute cystitis, the symptoms and bacteriuria were regressive with lactic acid gel treatment, without the need for antibiotic treatment. The complete regression of symptoms took between 1 week (7 women) and 4 weeks (4 women). In parallel with this regression, the microscopic shape of E.coli bacteria in these women changed from short rods to long curly filaments starting within the first days of therapy. The filamentous transformation affected 100% of the E.coli population in six women and at least 50% of E.coli population in five women and was not observed in urine samples from untreated women or in women without clinical response to lactic acid gel. This could not happen if the bladder was the origin of the infection. A number of recurrent and probably acute cystitis is a local vagino-urethritis caused by an adhesive invasive E.coli biofilm of the vaginal surface.

Relationship between fluorescence loss of QLF and depth of demineralization in an enamel erosion model

The purpose of this study was to assess the relationship between quantitative light-induced fluorescence (QLF) values and demineralization depths in an enamel erosion model in vitro. Flat labial enamel surfaces of bovine incisors were ground with 800-grit SiC and coated with nail varnish, but also leaving rectangular windows of enamel uncoated. Subsequently, they were immersed in a lactic acid gel (pH 5.0) for 0 to 7 weeks to make an enamel erosion model. Carious lesions thus induced were analyzed by QLF and the demineralization depths measured using SEM/ EDS method at the end of each period. A wide range of erosive lesions were produced with a steady increase in both demineralizing depth and fluorescence loss (DeltaF) over time. With this model, a good correlation was exhibited between each DeltaF value and the demineralization depth. Results of this study indicated that QLF could detect and quantify mineral loss under the eroded surface of the enamel erosion model.

Metronidazole with Lactacyd vaginal gel in bacterial vaginosis

To assess the efficacy and tolerability of lactic acid (Lactacyd vaginal gel; LVG) when given as an adjunct to metronidazole in the treatment of bacterial vaginosis (BV) among Filipino patients. A multicenter, open-labeled, controlled, randomized, three-arm comparative study on 90 women aged 18 years or over with clinically and microbiologically proven BV. The lactobacilli colony count significantly increased over time in all three arms. At day 14, growth of lactobacilli was significantly higher among patients in the lactic acid gel and combination treatment arms. Significant reduction of malodorous vaginal discharge (whiff test) and lowest recurrence of BV were noted in the metronidazole plus lactic acid gel arm. Regarding disappearance of signs of BV, there was significant decrease in the pH level and frequency of clue cell positive patients across time but was not significantly different across treatment groups. Only one patient (3%, 1/60) among those who received lactic acid gel complained of increased curd-like discharge. Six patients (10%, 6/60) who received metronidazole complained of epigastric pain/discomfort, dizziness and dyspnea. Lactic acid gel (LVG) is safe and as efficacious as metronidazole in the treatment of BV. There is evidence that LVG when combined with metronidazole is superior to metronidazole alone in promoting lactobacilli colonization. LVG as an adjunct to metronidazole, having the least number of recurrent BV, appears to result in better long-term treatment effect on bacterial vaginosis.

A study investigating the formation of artificial sub-surface enamel caries-like lesions in deciduous and permanent teeth in the presence and absence of fluoride

Objectives: Clinical and in situ studies have shown that caries formation and progression is faster in primary than in permanent teeth. Ambient levels of fluoride are also known to influence the processes of carious lesion formation. The aims were, firstly to investigate the incidence of artificial sub-surface caries lesion formation in the enamel of deciduous and permanent teeth in vitro. Secondly, to compare quantitatively the mineral content and distribution of these lesions and assess the possible influence of fluoride upon the lesion parameters. Methods: Twenty primary molars and 20 permanent premolars were randomly assigned to one of four experimental groups. Samples in each experimental group were immersed in a 0.05 M lactic acid gel (6% w/v hydroxyethyl cellulose, pH 4.5) either in the absence or presence of fluoride for 7 days. Subsequently, lesion parameters of mineral loss (vol.% μm) and lesion depth (μm) were assessed by transverse microradiography and image analysis. Results: No significant differences existed between the lesion parameters of permanent and primary teeth ( P=0.20). Irrespective of tooth type, lesion parameters were significantly reduced in samples demineralised in the presence of fluoride ( P≤0.002). Conclusions: Fluoride significantly reduces the severity of sub-surface caries lesions formed in vitro and in contrary to previous studies, there were no significant differences in lesions parameters between permanent and primary teeth.

Structure of dental glass-ionomer cements by confocal fluorescence microscopy and stereomicroscopy

The microstructure of four cements, setting by different mechanisms (acid–base, dual cure, triple cure), was studied. The porosity of unpolymerized materials was detected by stereomicroscopy. After polymerization and storage in water or lactic acid solution, the porosity, filler distribution and gel layer, which was formed at the filler/matrix interface of polymerized materials, were examined by confocal laser microscopy. For this purpose, the specimens were treated with fluorescent dye solution before the test. The results showed that hydrolytic degradation (pH 7) mainly involved the resin matrix, and the acid erosion (pH 3.5) involved the gel layer too. As regards the filler, materials with different setting mechanism released the glass particles in different times. The loss of the filler particles occurred quicker in acid–base setting cements, and slower in triple-cured material.

In vitro inhibition of enamel demineralization by a polymerizable amphiphilic film.

An amphiphilic coating is configured as a substantive film that has a tendency for an in-plane two-dimensional polymerization. This coating is hypothesized to protect enamel from in vitro acid decalcification, assessed through the following artificial caries model. Three regions on labial enamel of eight bovine incisors were treated with an acid resistant varnish (A), the amphiphilic coating (B), or left undisturbed (C), and the teeth were immersed for 3 wk in lactic acid gel. Mineral loss (deltaZ-value) was determined by a cross-sectional microhardness technique. deltaZ-values (mean +/- SD; volume percent mineral-microm) were: -4 +/- 24 (A), 29 +/- 69 (B), and 7,372 +/- 1,766 (C). deltaZ-value of the uncoated enamel (C) was significantly different from the other groups. Scanning electron microscopy showed enamel etched pattern from citric acid, and the coating firmly attached on enamel surface. This amphiphilic coating can inhibit enamel decalcification under the present experimental condition.

Histotomography studies of direct radiogenic dental enamel changes

The volume of literature on radiation-induced caries is still inconsistent as regards the state of the art. Our histotomographic studies have shown direct radiogenic effects on the dentoenamel junction (atrophy of the odontoblast processes). Whether there are direct effects of radiation on dental enamel is not yet known. Sound teeth (group 1, n = 10) were compared either with enamel specimens after high dose in vitro radiation (500-2500 Gy; group 2; n = 10) and after experimental enoral in situ irradiation (60 Gy; group 3; n = 20), or with teeth from patients after cancer radiotherapy (36 Gy; group 4; n = 20) and with teeth which had obviously decayed due to cancer radiotherapy (60 Gy; group 5; n = 20). Vestibular enamel surfaces of the teeth were exposed to identical in vitro demineralizations (lactic acid gel; pH = 5.0). Each of the samples was prospectively studied histologically by confocal laser scanning microscopy (CLSM) after 90, 180 and 270 min of acid interaction. Data were interpreted micromorphometrically (width of the demineralized area) and micromorphologically. The width of the demineralized area varies between the two in vivo irradiated groups of specimens (group 4: P < 0.01; group 5: P < 0.001) and the high dose in vitro irradiated teeth (P < 0.01) and is significantly different from the sound controls. The histological image of the demineralization in subsurface areas in the teeth of radiotherapy patients is characterized by a total loss of the prismatic structure (homogeneously, amorphous substance). Direct radiogenic effects at the dentoenamel junction have been described earlier. The additional information offered by this study is that there are significant micromorphometric differences in the demineralizing behaviour of irradiated enamel. Obviously, enamel is less resistant to acid attack after irradiation.

Inhibitive effect of a resin-modified glass ionomer cement on remote enamel artificial caries.

Glass ionomer cements (GICs) demonstrate the inhibition of caries lesions formed immediately adjacent to the restoration. This in vitro study was conducted to evaluate the distance at which a resin-modified GIC is able to exert its cariostatic effect on artificial enamel lesions ('remote effect'). Resin-modified GIC or bis-GMA resin was applied on the cervical third of the labial surface of 10 paired halves of bovine incisors. Specimens were separately immersed for 3 weeks in lactic acid gel which was changed every other day to reduce fluoride accumulation. Artificial lesions were examined by the cross-sectional microhardness (MHN) method. Volume percent mineral, mineral loss (delta Z value) and change in mineral content (delta M) were computed for each MHN profile, performed at distances of 0.2, 0.5, 1.0, 2.0, 4.0 and 7.0 mm from the edge of the materials. delta Z values of the resin-modified GIC group were significantly lower than those of the bis-GMA control group at all remote sites (t test, p < 0.05). The delta M caused by resin-modified GIC was more pronounced within 1.0 mm from the material which suggested that the demineralization inhibition can be divided into the near effect (< 1.0 mm). In this in vitro study, resin-modified GIC provided caries resistance in bovine enamel located at a considerable distance from the margin of the material.

Mineral Distribution and Dimensional Changes in Human Dentin during Demineralization

Many bonding agents require the dentin surface to be acid-etched prior to being bonded. Understanding the stability and morphology of the etched dentin surface is important for improving bond strength and reliability in these systems. In this study, the atomic force microscope was used to quantify dimensional changes that occur to fully hydrated dentin during demineralization with a pH 4.0 lactic acid gel. A high-resolution microtomography instrument, the x-ray tomographic microscope, was also used to quantify the mineral density distribution in the dentin as a function of etching time. The intertubular dentin surface shrank by less than 0.5 microns during etching, while the peritubular dentin receded at an initially rapid linear rate. The dentin surface retained its initial morphology, although it was more porous with the removal of the peritubular dentin. Beneath the etched surface, there were three major zones characterized by mineral density differences. The first zone was a fully demineralized collagen layer, subjacent to which was a partially demineralized zone of roughly constant mineral density. Immediately following the partially mineralized layer was normal dentin. The presence of the partially mineralized layer could be explained in terms of different transport rates in the peritubular and intertubular dentin.

Structure of Artificial Enamel Lesions after Topical Applications of High-Concentration Sodium Fluoride Solution in vitro

A three-layer structure, including a columnar layer (CL), a buffer layer, and unaffected intact enamel, was successively formed from the outer to the inner part of artificial enamel lesions (AEL) by topical applications of a high-concentration acidic sodium fluoride solution (10,000 ppm, pH 5.6) in vitro. The AEL was produced in bovine enamel that was decalcified for 5 days in a lactic acid gel system. The morphological observations by using scanning electron microscopy showed that the CL was made of columnar deposits of small globules about 0.5 microns in diameter. It was observed for the first time that small globules filled the demineralized interprismatic regions in the buffer layer. The unaffected intact enamel was protected from further demineralization under the acidic condition. Structure and composition of the CL were investigated by using X-ray diffraction and X-ray photoelectron spectroscopy. In the CL the atomic ratio was Ca:P = 12.6 and Ca:F = 0.75, and the small globules were mainly a mixture of polycrystalline calcium fluoride and hydroxyapatite. For comparison, the sound enamel and the AEL attained by applications of 0 and 100 ppm acidic sodium fluoride solutions (pH 5.6) were also investigated. The formation mechanism of the three-layer structure and the related cariostatic effects are discussed.

Uptake of fluoride by sound and artificially carious enamel in vitro following application of topical sodium and amine fluorides

The aim of this investigation was to compare fluoride uptake and retention by sound and artificially carious enamel, after the topical application of a neutral sodium fluoride solution (NaF) or a commercial preparation containing aqueous amine fluorides (AF) 297 and 335 (Elmex Fluid, GABA International, Basel, Switzerland). Ten pairs of extracted premolars were used, one of each pair being treated with NaF and the other with AF. A lactic acid gel technique was used to produce artificial caries lesions on one-half of the buccal surface of the premolar crowns. Estimates at selected depths of pretreatment fluoride concentration, uptake and retention were made using a step-wise acid-etch sampling technique. AF produced much greater uptake than NaF, the difference being most marked in the deeper layers of the artificial lesions, suggesting that the amine fluorides had a strong affinity for demineralized enamel. After storage in normal saline for 1 week during which partial loss of the acquired fluoride occurred, the percentages retained ranged from 37 (NaF) to 65 per cent (AF). It was concluded that AF enhanced both uptake and retention of fluoride by (artificial) early enamel caries lesions.