Morphometric study of extra-hepatic biliary pathways: study in human corpses / Estudio morfométrico de las vías biliares extrahepáticas: estudio en cadáveres humanos

SUMMARY: Adverse events (AE) contribute significantly to postoperative morbidities and comorbidities. Many AEs occur due to a lack of anatomical knowledge and its variants. Latrogenic bile duct injuries, for instance, represent a serious surgical complication of laparoscopic cholecystectomy. Anatomical knowledge for the identification and adequate drainage of all ducts is relevant and fundamental in order to avoid future errors. The objective of the study was to morphometrically analyze the bile ducts in adult human corpses. 13 livers were extracted from adult human corpses to obtain the ducts: choledochal, common hepatic and cystic. After morphological analysis, duct measurements (length and diameter) were continued using a digital caliper. The data obtained were tabulated in SPSS 21 program, performing descriptive analysis with mean and standard deviation. The averages of bile ducts were 61.05 (± 16.43) mm in length and 3.86 (± 0.72) mm in diameter. The cystic duct length and diameter averages were 33.59 (± 12.29) mm and 3.40 (± 0.79) mm, respectively. The common hepatic ducts had an average of 30.02 (± 7.19) mm in length and 3.74 (± 1.18) mm in diameter. The analyzed samples presented different values ?? from those already described in the literature, where the length of the cystic ducts was greater, while the length of the common hepatic ducts was numerically smaller. This work is very significant, as the morphometric variability of the bile ducts allows for varying morphological situations that can compromise the hepatobiliar physiology.

RESUMEN: Los eventos adversos (EA) contribuyen significativamente a las morbilidades y comorbilidades postoperatorias. Muchos EA se deben a la falta de conocimiento de la anatomía y sus variaciones. Por ejemplo, las lesiones iatrogénicas de las vías biliares representan una complicación quirúrgica grave de la colecistectomía laparoscópica. El conocimiento anatómico para la identificación y drenaje adecuado de todos los conductos es relevante y fundamental para evitar futuros errores. El objetivo del estudio fue analizar morfométricamente las vías biliares en cadáveres humanos adultos. Se extrajeron 13 hígados de cadáveres humanos adultos y se retiraron los conductos: colédoco, hepático común y cístico. Después del análisis morfológico, se continuó con las mediciones de los conductos (longitud y diámetro) utilizando un calibrador digital. Los datos fueron tabulados en el programa SPSS 21, mediante análisis descriptivos con media y desviación estándar. Los promedios de las vías biliares fueron de 61,05 (± 16,43) mm de longitud y 3,86 (± 0,72) mm de diámetro. Los promedios de longitud y diámetro del conducto cístico fueron 33,59 (± 12,29) mm y 3,40 (± 0,79) mm, respectivamente. Los conductos hepáticos comunes tenían un promedio de 30,02 (± 7,19) mm de longitud y 3,74 (± 1,18) mm de diámetro. Las muestras analizadas presentaron valores diferentes a los ya descritos en la literatura, donde la longitud de los conductos císticos era mayor, mientras que la longitud de los conductos hepáticos comunes fue numéricamente menor. Este trabajo es significativo, debido a que la variabilidad morfométrica de las vías biliares y permite identificar situaciones morfológicas que pueden comprometer la fisiología hapatobiliar.

Mycobacterium tuberculosis and Paracoccidioides brasiliensis Formation and Treatment of Mixed Biofilm In Vitro.

Co-infection of Mycobacterium tuberculosis and Paracoccidioides brasiliensis, present in 20% in Latin America, is a public health problem due to a lack of adequate diagnosis. These microorganisms are capable of forming biofilms, mainly in immunocompromised patients, which can lead to death due to the lack of effective treatment for both diseases. The present research aims to show for the first time the formation of mixed biofilms of M. tuberculosis and P. brasiliensis (Pb18) in vitro, as well as to evaluate the action of 3'hydroxychalcone (3'chalc) -loaded nanoemulsion (NE) (NE3'chalc) against monospecies and mixed biofilms, the formation of mixed biofilms of M. tuberculosis H37Rv (ATCC 27294), 40Rv (clinical strains) and P. brasiliensis (Pb18) (ATCC 32069), and the first condition of formation (H37Rv +Pb18) and (40Rv + Pb18) and second condition of formation (Pb18 + H37Rv) with 45 days of total formation time under both conditions. The results of mixed biofilms (H37Rv + Pb18) and (40Rv + Pb18), showed an organized network of M. tuberculosis bacilli in which P. brasiliensis yeasts are connected with a highly extracellular polysaccharide matrix. The (Pb18 + H37Rv) showed a dense biofilm with an apparent predominance of P. brasiliensis and fragments of M. tuberculosis. PCR assays confirmed the presence of the microorganisms involved in this formation. The characterization of NE and NE3'chalc displayed sizes from 145.00 ± 1.05 and 151.25 ± 0.60, a polydispersity index (PDI) from 0.20± 0.01 to 0.16± 0.01, and zeta potential -58.20 ± 0.92 mV and -56.10 ± 0.71 mV, respectively. The atomic force microscopy (AFM) results showed lamellar structures characteristic of NE. The minimum inhibitory concentration (MIC) values of 3'hidroxychalcone (3'chalc) range from 0.97- 7.8 µg/mL and NE3'chalc from 0.24 - 3.9 µg/mL improved the antibacterial activity when compared with 3'chalc-free, no cytotoxicity. Antibiofilm assays proved the efficacy of 3'chalc-free incorporation in NE. These findings contribute to a greater understanding of the formation of M. tuberculosis and P. brasiliensis in the mixed biofilm. In addition, the findings present a new possible NE3'chalc treatment alternative for the mixed biofilms of these microorganisms, with a high degree of relevance due to the lack of other treatments for these comorbidities.

Graphene Oxide Theranostic Effect: Conjugation of Photothermal and Photodynamic Therapies Based on an in vivo Demonstration.

INTRODUCTION: Cancer is the second leading cause of death globally and is responsible, where about 1 in 6 deaths in the world. Therefore, there is a need to develop effective antitumor agents that are targeted only to the specific site of the tumor to improve the efficiency of cancer diagnosis and treatment and, consequently, limit the unwanted systemic side effects currently obtained by the use of chemotherapeutic agents. In this context, due to its unique physical and chemical properties of graphene oxide (GO), it has attracted interest in biomedicine for cancer therapy. METHODS: In this study, we report the in vivo application of nanocomposites based on Graphene Oxide (nc-GO) with surface modified with PEG-folic acid, Rhodamine B and Indocyanine Green. In addition to displaying red fluorescence spectra Rhodamine B as the fluorescent label), in vivo experiments were performed using nc-GO to apply Photodynamic Therapy (PDT) and Photothermal Therapy (PTT) in the treatment of Ehrlich tumors in mice using NIR light (808 nm 1.8 W/cm2). RESULTS: This study based on fluorescence images was performed in the tumor in order to obtain the highest concentration of nc-GO in the tumor as a function of time (time after intraperitoneal injection). The time obtained was used for the efficient treatment of the tumor by PDT/PTT. DISCUSSION: The current study shows an example of successful using nc-GO nanocomposites as a theranostic nanomedicine to perform simultaneously in vivo fluorescence diagnostic as well as combined PDT-PTT effects for cancer treatments.

Epitope spreading toward wild-type melanocyte-lineage antigens rescues suboptimal immune checkpoint blockade responses.

Although immune checkpoint inhibitors (ICIs), such as anti-programmed cell death protein-1 (PD-1), can deliver durable antitumor effects, most patients with cancer fail to respond. Recent studies suggest that ICI efficacy correlates with a higher load of tumor-specific neoantigens and development of vitiligo in patients with melanoma. Here, we report that patients with low melanoma neoantigen burdens who responded to ICI had tumors with higher expression of pigmentation-related genes. Moreover, expansion of peripheral blood CD8+ T cell populations specific for melanocyte antigens was observed only in patients who responded to anti-PD-1 therapy, suggesting that ICI can promote breakdown of tolerance toward tumor-lineage self-antigens. In a mouse model of poorly immunogenic melanomas, spreading of epitope recognition toward wild-type melanocyte antigens was associated with markedly improved anti-PD-1 efficacy in two independent approaches: introduction of neoantigens by ultraviolet (UV) B radiation mutagenesis or the therapeutic combination of ablative fractional photothermolysis plus imiquimod. Complete responses against UV mutation-bearing tumors after anti-PD-1 resulted in protection from subsequent engraftment of melanomas lacking any shared neoantigens, as well as pancreatic adenocarcinomas forcibly overexpressing melanocyte-lineage antigens. Our data demonstrate that somatic mutations are sufficient to provoke strong antitumor responses after checkpoint blockade, but long-term responses are not restricted to these putative neoantigens. Epitope spreading toward T cell recognition of wild-type tumor-lineage self-antigens represents a common pathway for successful response to ICI, which can be evoked in neoantigen-deficient tumors by combination therapy with ablative fractional photothermolysis and imiquimod.

Multilayered iron oxide/reduced graphene oxide nanocomposite electrode for voltammetric sensing of bisphenol-A in lake water and thermal paper samples.

A multilayered iron oxide/reduced graphene oxide (ION-RGO) nanocomposite electrode is reported for the voltammetric sensing of bisphenol-A (BPA). Structural characterizations reveal the nanocomposite features RGO sheets decorated with nanometric spherical ION in a mixture of maghemite and magnetite phases. ITO substrate modified with the ION-RGO multilayered film exhibits strong electrocatalytic effect toward BPA oxidation, which is made possible by Fe(III) catalysts generated at the ION's surface after scanning the electrode potential from below 0 V (vs Ag/AgCl) and followed by the RGO phase conducting the transferred electrons. Under optimized differential pulse voltammetry conditions, the proposed sensor shows three linear working ranges 0.09-1.17 (r2 = 0.999), 1.17-3.81 (r2 = 0.995) and 3.81-8.20 (r2 = 0.998), with the highest sensitivity equaling 7.76 µA cm-2/µmol L-1 and the lowest limit of detection of 15 nmol L-1. A single electrode can be used for at least twenty consecutive runs loosing less than 15% of sensitivity, whereas electrodes fabricated in different bacthes exhibit almost identical perfomances. Determination of BPA in a thermal paper sample shows no difference (at 95% confidence level) between the proposed sensor and HPLC/UV. The sensor is neither influenced by the matrix composition nor by other emerging contaminants.

Synthesis and Characterization of Nanostructured Lipid Nanocarriers for Enhanced Sun Protection Factor of Octyl p-methoxycinnamate.

Sunlight is important to health, but higher exposure to radiation causes early aging of the skin and skin damage that can lead to skin cancers. This study aimed at producing a stable octyl p-methoxycinnamate (OMC)-loaded nanostructured lipid carrier (NLC) sunscreen, which can help in the photoprotective effect. NLC was produced by emulsification-sonication method and these systems were composed of myristyl myristate (MM), caprylic capric triglyceride (CCT), Tween® 80 (TW), and soybean phosphatidylcholine (SP) and characterized by dynamic light scattering (DLS), zeta potential (ZP) measurement, atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and in vitro release studies. Pre-formulation studies were performed changing TW concentrations and no differences were found at concentrations of 1.0 and 2.0%. Two selected formulations were designed and showed an average size of 91.5-131.7, polydispersity index > 0.2, and a negative value of ZP. AFM presented a sphere-like morphology and SEM showed ability to form a thin film. DSC exhibited that the incorporation of OMC promoted reduction of enthalpy due to formation of a more amorphous structure. Drug release shows up to 55.74% and 30.57%, and this difference could be related to the presence of SP in this formulation that promoted a more amorphous structure; the release mechanism study indicated Fickian diffusion and relaxation. Sun protection factor (SPF) evaluation was performed using NLC and presented values around 40, considerably higher than those observed in the literature. The developed formulations provide a beneficial alternative to conventional sunscreen formulations.

Antifungal activity of 2'-hydroxychalcone loaded in nanoemulsion against Paracoccidioides spp.

Aim: This study aimed to evaluate the activity of 2'-hydroxychalcone-loaded in nanoemulsion (NLS + 2'chalc), the cytotoxic effect and toxicity against Paracoccidioides brasiliensis and Paracoccidioides lutzii using a zebrafish model. Materials & methods: Preparation and physical-chemical characterization of nanoemulsion (NLS) and NLS + 2'chalc were performed. MIC and minimum fungicide concentration, cytotoxicity and toxicity were also evaluated in the Danio rerio model. Results: NLS + 2'chalc showed fungicidal activity against Paracoccidioides spp. without cytotoxicity in MRC5 and HepG2 lines. It also had high selectivity index values and no toxicity in the zebrafish model based on MIC values. Conclusion: NLS + 2'chalc is a potential new alternative treatment for paracoccidioidomycosis.

Enhanced mobility and controlled transparency in multilayered reduced graphene oxide quantum dots: a charge transport study.

Reduced graphene oxide (rGO) layers are known to be significantly conductive along the basal plane throughout delocalized sp2 domains. Defects present in rGO implies in disordered systems with numerous localized sites, resulting in a charge transport governed mainly by a 2D variable range hopping (VRH) mechanism. These characteristics are observed even in multilayered rGO since the through-plane conduction is expected to be insubstantial. Here, we report on the multilayer assembly of functionalized rGO quantum dots (GQDs) presenting 3D VRH transport that endows elevated charge carrier mobility, ca âˆ¼ 236 cm2 V-1 s-1. Polyelectrolyte-wrapped GQDs were assembled by layer-by-layer technique (LbL), ensuring molecular level thickness control for the formed nanostructures, along with the adjustment of the film transparency (up to 92% in the visible region). The small size and the random distribution of GQDs in the LbL structure are believed to overcome the translational disorder in multilayered films, contributing to a 3D interlayer conduction that enhances the electronic properties. Such high-mobility, transparency-tunable films assembled by a cost-effective method possess interesting features and wide applicability in optoelectronics.

Graphene Oxide Mediated Broad-Spectrum Antibacterial Based on Bimodal Action of Photodynamic and Photothermal Effects.

Graphene oxide (GO) with their interesting properties including thermal and electrical conductivity and antibacterial characteristics have many promising applications in medicine. The prevalence of resistant bacteria is considered a public health problem worldwide, herein, GO has been used as a broad spectrum selective antibacterial agent based on the photothermal therapy (PTT)/photodynamic therapy (PDT) effect. The preparation, characterization, determination of photophysical properties of two different sizes of GO is described. In vitro light dose and concentration-dependent studies were performed using Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria based on the PTT/PDT effect used ultra-low doses (65 mW cm-2) of 630 nm light, to achieve efficient bacterial decontamination. The results show that GO and nanographene oxide (nGO) can sensitize the formation of 1O2 and allow a temperature rise of 55°C to 60°C together nGO and GO to exert combined PTT/PDT effect in the disinfection of gram-positive S. aureus and gram-negative E. coli bacteria. A complete elimination of S. aureus and E. coli bacteria based on GO and nGO is obtained by using a dose of 43-47 J cm-2 for high concentration used in this study, and a dose of around 70 J cm-2 for low dose of GO and nGO. The presence of high concentrations of GO allows the bacterial population of S. aureus and E. coli to be more sensitive to the use of PDT/PTT and the efficiency of S. aureus and E. coli bacteria disinfection in the presence of GO is similar to that of nGO. In human neonatal dermal fibroblast, HDFs, no significant alteration to cell viability was promoted by GO, but in nGO is observed a mild damage in the HDFs cells independent of nGO concentration and light exposure. The unique properties of GO and nGO may be useful for the clinical treatment of disinfection of broad-spectrum antimicrobials. The antibacterial results of PTT and PDT using GO in gram-positive and gram-negative bacteria, using low dose light, allow us to conclude that GO and nGO can be used in dermatologic infections, since the effect on human dermal fibroblasts of this treatment is low compared to the antibacterial effect.

Magnetic studies of layer-by-layer assembled polyvinyl alcohol/iron oxide nanofilms.

This study reports on investigation of the magnetic properties of layer-by-layer (LbL) assembled nanofilms comprising polyvinyl alcohol (PVA) and citrate-coated magnetite (cit-MAG) nanoparticles deposited onto silicon (SF sample) and glass (GF sample) substrates. DC magnetization measurements were performed over the temperature range of 4 K to 300 K, in the applied magnetic field range of ±60 kOe. The magnetic data of the as-synthesized cit-MAG nanoparticles (F sample) are also collected for comparison. The three as-fabricated samples reveal perfect superparamagnetic (SPM) behavior only around room temperature; at temperatures lower than 200 K the SPM scaling is not observed and all samples behave as interacting superparamagnetic (ISPM) materials. The evolution from the ISPM to the SPM regime is marked by a steady decrease in the hysteretic properties of all samples, with the temperature-dependence of the coercivity decreasing slower than the T1/2 behavior predicted for non-interacting superparamagnetic particles. The modified Bloch's law used to assess information on nanoparticles' surface spins gives the Bloch's exponent close to 2 (for the F and SF samples) and close to 1 (for the GF sample). Interestingly, the surface spin freezing temperature (Tf) is 8 ± 1 K for all samples. The magnetic behavior of all three samples can be described within the model picture of a core-shell structure for the cit-MAG nanoparticles; the core comprising magnetically-ordered spins whereas the shell behaving as a spin-glass-like system. However, the contribution of the shell magnetism to the effective magnetic properties is much more evident in the GF sample in which magnetic dipole-dipole interaction is three-times weaker than in the SF sample and two times weaker than in the F sample. In contrast, the strong magnetic dipole-dipole interaction in the SF sample affects the surface spins, hindering the onset of magnetically-ordered regions in the nanoparticle's shell, making the surface magnetism contribution negligible. The LbL-fabricated nanofilms herein reported and the presented analysis of their magnetic properties we envisage can support the engineering of magnetic nanofilms for multiple applications.

Poly(allylamine hydrochloride) (PAH) and Bovine Serum Albumin (BSA) Protein Nanostructured as Layer-by-Layer Thin Films.

In this work it was studied the production of nanostructured thin films containing alternating layers of poly(allylamine hydrochloride) (PAH) and bovine serum albumin protein (BSA). It was studied the adsorption processes of these materials onto solid surfaces, which included adsorption kinetics and film growth studies by using UV-Vis spectroscopy. The film morphology, thickness and roughness were studied by using atomic force microscopy (AFM). The AFM results showed that the film presented a globular-like surface morphology and a thickness within the nanoscale, which could be controlled by the number of deposited layers. The roughness and thickness of the film depend on the number of deposited bilayers, where the film roughness increased for films with a number of bilayers up to five, after which the film roughness remained almost constant. This is an indicative that the adsorption and growth processes might occur under two different mechanisms, first under the influence of the substrate (films containing up to five bilayers of PAH/BSA), and second under the influence of the film previously deposited (films containing more than five bilayers of PAH/BSA), respectively.

Charge carrier transport in defective reduced graphene oxide as quantum dots and nanoplatelets in multilayer films.

Graphene is a breakthrough 2D material due to its unique mechanical, electrical, and thermal properties, with considerable responsiveness in real applications. However, the coverage of large areas with pristine graphene is a challenge and graphene derivatives have been alternatively exploited to produce hybrid and composite materials that allow for new developments, considering also the handling of large areas using distinct methodologies. For electronic applications there is significant interest in the investigation of the electrical properties of graphene derivatives and related composites to determine whether the characteristic 2D charge transport of pristine graphene is preserved. Here, we report a systematic study of the charge transport mechanisms of reduced graphene oxide chemically functionalized with sodium polystyrene sulfonate (PSS), named as GPSS. GPSS was produced either as quantum dots (QDs) or nanoplatelets (NPLs), being further nanostructured with poly(diallyldimethylammonium chloride) through the layer-by-layer (LbL) assembly to produce graphene nanocomposites with molecular level control. Current-voltage (I-V) measurements indicated a meticulous growth of the LbL nanostructures onto gold interdigitated electrodes (IDEs), with a space-charge-limited current dominated by a Mott-variable range hopping mechanism. A 2D intra-planar conduction within the GPSS nanostructure was observed, which resulted in effective charge carrier mobility (µ) of 4.7 cm2 V-1 s-1 for the QDs and 34.7 cm2 V-1 s-1 for the NPLs. The LbL assemblies together with the dimension of the materials (QDs or NPLs) were favorably used for the fine tuning and control of the charge carrier mobility inside the LbL nanostructures. Such 2D charge conduction mechanism and high µ values inside an interlocked multilayered assembly containing graphene-based nanocomposites are of great interest for organic devices and functionalization of interfaces.

Effective transcutaneous immunization using a combination of iontophoresis and nanoparticles.

Needle-free immunization strategies have been sought for years. Transcutaneous immunization using electroporation has been studied, but the high electrical voltage that must be applied may be painful and cause irreversible cell damage. The application of a weak electric field, such as in iontophoresis, has never been attempted. The aim of this work was to verify the potential of employing iontophoresis for transcutaneous immunization using ovalbumin (OVA) as a model antigen. To target the antigen presenting cells that are located in the viable epidermis, a vaccine formulation composed of OVA-loaded liposomes and silver nanoparticles (NPAg) was developed. In vitro cathodal iontophoresis of the OVA-liposomes associated with NPAg increased OVA penetration into the viable epidermis by 92-fold in comparison to passive delivery. In vivo, transcutaneous immunization with a suitable combination of liposome and iontophoresis induced the production of antibodies, differentiation of immune-competent cells and appeared to present an alternative strategy for needle-free vaccination.

Accelerated Sonochemical Extraction of Cellulose Nanowhiskers.

Studies on sonochemical hydrolysis of cellulose have been suggested as an alternative route to obtaining cellulose nanoparticles. In this work, the potential use of acid hydrolysis assisted by sonication to obtain cellulose whiskers was studied. Parameters such as acid concentration, hydrolysis time and temperature were investigated to evaluate their effect on the morphological properties of the nanowhiskers, as compared to the conventional extraction process by acid hydrolysis with mechanical stirring. Morphology and degree of crystallinity of the nanowhiskers were studied by atomic force microscopy (AFM) and X-ray diffraction (XRD). Results indicated that the extraction time was reduced from about 45 min to less than 3 min using the same acid concentration and temperature used in conventional acid hydrolysis treatment. Likewise, it was possible, within the range of 30 min, to extract whiskers at room temperature or using half the concentration of acid by raising the temperature to about 80 degrees C. These are promising results towards a more economically viable and ecologically friendly extraction procedure used to obtain cellulose nanowhiskers, since both extraction time and acid concentration, used in nanowhisker extraction, were significantly reduced by replacing mechanical with sonochemical stirring.

Analysis of the Early Stages and Evolution of Dental Enamel Erosion

Abstract The aim of this study was to evaluate by atomic force microscopy (AFM) the early phases and evolution of dental enamel erosion caused by hydrochloric acid exposure, simulating gastroesophageal reflux episodes. Polished bovine enamel slabs (4x4x2 mm) were selected and exposed to 0.1 mL of 0.01 M hydrochloric acid (pH=2) at 37 ?#61472;?#61616;C using five different exposure intervals (n=1): no acid exposure (control), 10 s, 20 s, 30 s and 40 s. The exposed area was analyzed by AFM in 3 regions to measure the roughness, surface area and morphological surface. The data were analyzed qualitatively. Roughness started as low as that of the control sample, Rrms=3.5 nm, and gradually increased at a rate of 0.3 nm/s, until reaching Rrms=12.5 nm at 30 s. After 40 s, the roughness presented increment of 0.40 nm only. Surface area (SA) increased until 20 s, and for longer exposures, the surface area was constant (at 30 s, SA=4.40 μm2 and at 40 s, SA=4.43 μm2). As regards surface morphology, the control sample presented smaller hydroxyapatite crystals (22 nm) and after 40 s the crystal size was approximately 60 nm. Short periods of exposure were sufficient to produce enamel demineralization in different patterns and the morphological structure was less affected by exposure to hydrochloric acid over 30 s.

Resumo O objetivo deste estudo foi avaliar os estágios iniciais e a evolução da erosão do esmalte dental causado pela exposição ao ácido clorídrico, simulando assim episódios de refluxo gastroesofágico, usando um microscópio de força atômica (AFM). Fragmentos de esmalte bovino planificados e polidos (4x4x2 mm) foram selecionados e exposto a 0,1 mL de ácido clorídrico 0,01 M (pH = 2) a 37 ?#61616;C, utilizando cinco intervalos diferentes de exposição: sem exposição ao ácido (controle) e 10 s, 20 s, 30 s e 40 s. Então, a área exposta foi analisada com AFM em 3 regiões diferentes para mensurar a rugosidade, a área da superfície e a morfologia superficial. Os dados foram analisados qualitativamente. Inicialmente, a rugosidade apresentou valor baixo como a amostra controle, Rrms=3,5 nm, e aumentou gradualmente a uma taxa de 0,3 nm/s, até Rrms= 12,5 nm a 30 s. Após 40 s, a rugosidade apresentou um incremento de apenas 0,40 nm. Área de superfície (SA) aumentou até 20 s, e para exposições mais longas, a área de superfície manteve-se constante (30 s, o SA=4,40 μm2, e em 40 s, a SA=4,43 μm2). Em relação à morfologia superficial, a amostra controle apresentou cristais de hidroxiapatita menores (22 nm), e após 40s o tamanho do cristal era de aproximadamente 60 nm. Períodos curtos de exposição foram suficientes para produzir a desmineralização do esmalte em diferentes padrões e a estrutura morfológica foi menos afetada pela exposição ao ácido clorídrico acima de 30 s.

Analysis of the Early Stages and Evolution of Dental Enamel Erosion.

The aim of this study was to evaluate by atomic force microscopy (AFM) the early phases and evolution of dental enamel erosion caused by hydrochloric acid exposure, simulating gastroesophageal reflux episodes. Polished bovine enamel slabs (4x4x2 mm) were selected and exposed to 0.1 mL of 0.01 M hydrochloric acid (pH=2) at 37 ?#61472;?#61616;C using five different exposure intervals (n=1): no acid exposure (control), 10 s, 20 s, 30 s and 40 s. The exposed area was analyzed by AFM in 3 regions to measure the roughness, surface area and morphological surface. The data were analyzed qualitatively. Roughness started as low as that of the control sample, Rrms=3.5 nm, and gradually increased at a rate of 0.3 nm/s, until reaching Rrms=12.5 nm at 30 s. After 40 s, the roughness presented increment of 0.40 nm only. Surface area (SA) increased until 20 s, and for longer exposures, the surface area was constant (at 30 s, SA=4.40 µm2 and at 40 s, SA=4.43 µm2). As regards surface morphology, the control sample presented smaller hydroxyapatite crystals (22 nm) and after 40 s the crystal size was approximately 60 nm. Short periods of exposure were sufficient to produce enamel demineralization in different patterns and the morphological structure was less affected by exposure to hydrochloric acid over 30 s.