RESUMO Objetivo: O objetivo do presente estudo foi avaliar o efeito da aplicação do laser Yd:YAG sobre a superfície metálica da base de braquetes ortodônticos, a resistência da colagem ao cisalhamento (RU) e os locais das falhas nas interfaces adesivas. Métodos: Os braquetes foram divididos em dois grupos, de acordo com o tipo de base: OP (One Piece - monobloco, base jateada) e OPL (One Piece - monobloco, base irradiada a laser). Foram selecionados 40 incisivos bovinos hígidos para a colagem de braquetes na superfície do esmalte. Os testes de RU foram realizados por meio de uma máquina de ensaio universal EMIC DL1000. O Índice de Adesivo Remanescente (ARI) e a caracterização das superfícies foram realizados empregando-se estereomicroscópio e microscópio eletrônico de varredura (MEV). O teste t de Student foi aplicado para comparar a RU entre os dois grupos (p< 0,05). O ARI foi avaliado por meio da análise de Frequência e teste do Qui-quadrado. Resultados: O grupo OPL obteve maiores valores de RU (p<0,001) do que o grupo OP (43,95 MPa e 34,81 MPa, respectivamente), e o ARI obteve diferença significativa (p<0,001) entre os grupos OPL (ARI 0 = 100%) e OP (ARI 0 = 15%). A análise proveniente do MEV mostrou alta interação adesiva entre a resina e a superfície metálica da base irradiada pelo feixe de laser. Conclusões: A irradiação com laser Yd:YAG sobre a superfície da base de braquetes metálicos aumentou os valores da RU, demonstrando que as falhas adesivas ocorreram na interface esmalte/adesivo. O uso de braquetes modificados com irradiação a laser pode ser adotado como alternativa aos braquetes com bases convencionais nos casos em que uma maior retentividade for requerida para reduzir as falhas de adesividade.

ABSTRACT Objective: The purpose of this study was to evaluate the effect of the Yd:YAG laser irradiation on orthodontic bracket base surface. Shear bond strength (SBS) values and sites of the bonding failure interfaces were quantified. Methods: Brackets were divided into two groups: OP (One Piece - integral sandblast base) and OPL (One Piece - laser irradiation). The brackets were randomly bonded on an intact enamel surface of 40 bovine incisors. The SBS tests were carry out using a universal test machine. A stereomicroscopy was used to evaluate the adhesive remnant index (ARI), and surface characterization was performed by scanning electron microscopy (SEM). Student’s t-test was used to compare the SBS between the two groups (p< 0.05). Frequencies and chi-square analysis were applied to evaluate the ARI scores. Results: OPL group showed higher value (p< 0.001) of SBS than OP group (43.95 MPa and 34.81 MPa, respectively). ARI showed significant difference (p< 0.001) between OPL group (ARI 0 = 100%) and OP group (ARI 0 = 15%). SEM showed a higher affinity between the adhesive and the irradiated laser base surface. Conclusions: Yd:YAG laser irradiation on bracket base increased SBS values, showing that bonding failure occurs at the enamel/adhesive interface. Laser-etched bracket base may be used instead of conventional bases in cases where higher adhesion is required, reducing bracket-bonding failure.

Extensive data reported the influence of the physicochemical properties on the bacterial adhesion in biomaterials, of which surface roughness of titanium (Ti) can dictates methicillin-resistant Staphylococcus aureus (MRSA) adhesion to orthopedic implants. Herein, we investigated the influence of the Yb:YAG laser texturing of titanium-15molybdenum (TiMo-L) surface on the MRSA (ATCC #33591) cells adhesion and viability. The physicochemical properties and antibacterial performance of TiMo-L were compared to samples of laser-irradiated pure titanium (Ti-L). Polished samples (Ti-P and TiMo-P) were used as controls. Laser textured surfaces presented a high degree of hydrophilicity, an irregular-shaped cavity and a typical microstructured pattern, compared to the polished substrates. The laser irradiation reduced the peaks of molybdenum (Mo) in the surface of Ti-15Mo alloy, which is explained, at least in part, by the difference between the melting point of Ti (1.668 ºC) and Mo (2.623 ºC). Laser texturing raised the MRSA cells viability and statistically increased the bacterial adhesion to pure Ti (P < 0.01; Wilcoxon-Signed rank test) and Ti-15Mo alloy (P < 0.001; Paired t test). The TiMo-L surface was significantly less susceptible to MRSA cell adhesion compared to Ti-L substrate (P < 0.001; Paired t test).

Nesse trabalho, estudou-se a modificação da superfície da liga Ti-6Al-4V pela irradiação com feixe de laser Nd:YAG, variando o espaçamento da matriz e mantendo-se constantes os demais parâmetros. Após a irradiação, as amostras foram imersas na solução SBF (Simulated Body Fluid) por 7 dias a 37 ºC, para a nucleação e formação das apatitas. Após o recobrimento, essas amostras foram submetidas a um tratamento térmico a 600 ºC. Resultados de difração de raiosX indicaram a formação de uma mistura de fases contendo hidroxiapatita e fosfato tricálcico. Análises no infravermelho constataram a presença de estiramentos referentes à hidroxiapatita. As micrografias mostraram que diferentes espaçamentos da matriz proporcionaram a formação de diferentes morfologias. O espaçamento de 0,01 cm induziu a formação de microesferas características da fase hidroxiapatita, enquanto, para o espaçamento 0,02 cm, apenas um recobrimento não homogêneo foi obtido. Portanto, a utilização de laser na produção de superfícies ativas para a deposição de biocerâmicas mostrou-se viável, e o substrato após o recobrimento final possui potencial para aplicações na área de implantes dentários.

In this work, surface modification of the Ti-6Al-4V alloy by irradiation with a Nd:YAG laser beam was studied. The matrix spacing was varied and the other parameters were kept constant. After theirradiation, the samples were immersed into SBF solution (Simulated Body Fluid) for 7 days at 37 ° C for nucleation and formation of calcium phosphates. After this period, the samples were subjected to a heat treatment at 600 °C. X-ray diffraction results indicated the formation of a mixture of phases containing hydroxyapatite and tricalcium phosphate. Infrared analysis demonstrated the presence of bands related to hydroxyapatite. SEM micrographs showed that different matrix spacing used leads to the formation of different morphologies.The 0.01 cm spacing induced the formation of microspheres, characteristic of the hydroxyapatite phase, while for 0.02 cm spacing, only a non-homogeneous coating was obtained. Therefore, the use of laser in the production of active surfaces for deposition of bioceramics proved to be viable, and the final coating has potential for applications in the field of dental implants.

For decades the Hydroxyapatite (HA) was only bioceramic of calcium phosphate system used for bone replacement and regeneration, due to its similarity to the mineral phase of bones and teeth. Because its slow degradation, other calcium phosphate classified as biodegradable started to awaken interest, such as: amorphous calcium phosphate (ACP), octacalcium phosphate (OCP) and tricalcium phosphate (TCP). This work presents the evolution of the use of other calcium phosphates due to their better solubility than the HA, comparing their main physical-chemical and biological properties. Are also presented the main methods used to obtain bioceramic coatings on metal and polymer surfaces.

The purpose of the present study was to evaluate, using a biomechanical test, the force needed to remove implants with surface modification by laser (Nd:YAG) in comparison with implants with machined surfaces. Twenty-four rabbits received one implant with each surface treatment in the tibia, machined surface (MS) and laser-modified surface (LMS). After 4, 8 and 12 weeks of healing, the removal torque was measured by a torque gauge. The surfaces studied were analyzed according to their topography, chemical composition and roughness. The average removal torque in each period was 23.28, 24.0 and 33.85 Ncm for MS, and 33.0, 39.87 and 54.57 Ncm for LMS, respectively. The difference between the surfaces in all periods of evaluation was statistically significant (p < 0.05). Surface characterization showed that a deep and regular topography was provided by the laser conditioning, with a great quantity of oxygen ions when compared to the MS. The surface micro-topography analysis showed a statistical difference (p < 0.01) between the roughness of the LMS (Ra = 1.38 ± 0.23 μm) when compared to that of the MS (Ra = 0.33 ± 0.06 μm). Based on these results, it was possible to conclude that the LMS implants' physical-chemical properties increased bone-implant interaction when compared to the MS implants.

The osseointegrated titanium implants are reliable and safe alternatives to treatments for long periods of time. For surface modification, thermal aspersion of TiO2 was used. The samples with and without TiO2 were treated with NaOH and SBF in order to obtain a layer of HA. Characterization was done by SEM and FTIR. The images of HA obtained by SEM show a uniform morphology and a porous structure with spherical particles. The IR spectra show that the surface of Ticp/ TiO2 is more favorable for the HA deposit, as can be seen by the increase of the crystalline structure and the very intense and defined bands of the OH group of HA that is verified about 3571 and 630 cm-1. Thus the Ticp/ TiO2 surface presents a satisfactory nucleation of HA when compared to Ticp.

The crystallization of hydroxyapatite (HA) in aqueous solution can be described by the mechanism ACP -> OCP -> HA. In this work, it was studied the influence of K+, Mg2+, SO4(2-) and CO3(2-) ions in the formation of ACP and in its conversion to OCP, using biomimetic coatings on metallic substrates of commercially pure titanium (Ti c.p.). The results showed that Mg2+ and CO3(2-) ions favored both the formation of ACP and its conversion to OCP. Differently, K+ and SO4(2-) ions did not influence the formation of ACP and, consequently, interfered in the conversion to OCP.

OBJETIVO: Estudar a superfície de implantes osseointegráveis utilizando discos de titânio irradiados com feixe de laser. MÉTODOS: A amostra foi irradiada com feixes de laser de alta intensidade (Nd-YAG), posteriormente depositado hidróxiapatita e submetido a tratamento térmico. Foi analisada sob MEV (Microscópio Eletrônico de Varredura) e realizada análise morfológica qualitativa com microfotografias em vários aumentos. RESULTADOS: A superfície irradiada com laser apresentou deformidade superficial e característica isomórfica; a aplicação de hidroxiapatita pelo método de biomimético aumentou quantitativamente a área da superfície de titânio. CONCLUSÃO: A deposição de hidroxiapatita apresentou melhor característica isomórfica e aumento quantitativo da área superficial estudada, a amostra demonstrou características não encontradas nos implantes disposto no mercado.

PURPOSE: The aim of this study was to analyse the surface of titanium implants using disc irradiated with lasers. METHODS: Titanium discs were irradiated with laser high insensitive (Nd-YAG), deposited durapatite and used thermal treatment. Sample received qualitative morphological analyse trough micrographics with many size in SEM (Scanning Electron Microscopy). RESULTS: Surface laser irradiation shows roughness and isomorphic characteristic. The durapatite amplified the titanium surface area by method biomimetic. CONCLUSION: The surface treatment presented more deposition of durapatite, roughness on the surface, better isomorphic characteristic and increase quantitative in titanium surface area, samples shows rugous, roughness and homogeneity there is not found in the implants available at the market.

Commercial purity titanium (cp-Ti), and some of its alloys are important materials in the medical field because of their excellent biocompatibility and mechanical properties. Recently a simple chemical method to induce bioactivity in these inert metallic materials was reported. In this work, the biomimetic chemical process has been used to modify the surface of cp-Ti with the formation of a deposit layer of apatite (a calcium phosphate compound). The main purpose was to study the influence of heat treatment on changes in crystallinity in the deposited phases. X-ray diffraction analysis and scanning electron microscopy showed that the apatite coatings heat treated between 400 and 600 °C were less crystalline, similar to biological apatites. Upon heat treatment at temperatures above 700 °C, the apatite coatings appeared more crystalline, and were a mixture of hydroxyapatite, octacalcium phosphate and magnesium phosphate.

Among the copper sulphides, chalcopyrite (CuFeS2), covellite (CuS) and chalcocite (Cu2S) are the most important source of minerals for copper mining industry. The acknowledge of behaviour of these sulphides related with bacterial leaching process are essential for optimization procedures. Despite of its importance, covellite has not deserved much interest of researchers regarding this matter. In this work it was studied the oxidation of covellite by the chemolithotrophic bacterium Thiobacillus ferrooxidans by using electrochemical techniques, such as open circuit potentials with the time and cyclic voltammetry. The experiments were carried out in acid medium (pH 1.8), containing or not Fe2+ as additional energy source, and in different periods of incubation; chemical controls were run in parallel. The results showed that a sulphur layer is formed spontaneously due the acid attack, covering the sulphide in the initial phase of incubation, blocking the sulphide oxidation. However, the bacterium was capable to oxidize this sulphur layer. In the presence of Fe2+ as supplemental energy source, the corrosion process was facilitated, because ocurred an indirect oxidation of covellite by Fe3+, which was produced by T. ferrooxidans oxidation of the Fe2+ added in the medium.

The Ti-6Al-4V alloy used as biomaterial has been used over the last years. The literature shows controversies concerning the kind and the chemical composition of the film naturally and elctrochemically formed on the surface of the titanium alloy. The presente work studies the film composition before and after the electrochemical polarization tests using the x Ray photoelectron spectroscopy (XPS) technique. The results showed that the film naturally formed on the metallic surface is constituted of a variety of oxides which do not cover the whole surface of the metallic alloy and therefore, metallic Ti, Al and V can be found on the uncovered areas. The tests of XPS made after the polarization up to 4V (SCE) showed that the electrochemically formed film is constituted only of TiO2 and that the peak current observed around 1,5 V (SCE) is due to the oxidation of any kind of titanium oxide or the growth of the film.

Neste trabalho avaliou-se a resistência à corrosão em solução salina das fases presentes na microestrutura de amálgamas dentários comerciais: gama1-Ag2Hg3, o eutético Ag-Cu e gama2-Sn7-8Hg, empregando-se técnicas eletroquímicas de potencial a circuito aberto com o tempo, de polarização potenciodinâmica e de espectroscopia de impedância eletroquímica. As ligas metálicas em estudo já foram caracterizadas em um trabalho prévio, por meio de microscopia eletrônica de varredura e difratometria de raios X. A resistência à corrosão se origina da formação de filmes passivos na superfície metálica e parece estar determinada pela natureza rugosa e porosa das superfícies.

In this work, the corrosion resistance behavior of three of their phases presents in dental amalgam has been investigated: gamma1-Ag2Hg3 (the matrix phase in the microstructure), gamma2-Sn7-8Hg (the phase most susceptible to corrosion in the oral cavity, according to the literature) and Ag-Cu eutectic (the component of the more modern powder alloys, the objective being to reduce the quantity of gamma2-Sn7-8Hg formed during the amalgamation and in this way increase its corrosion resistance). Electrochemical measurements were carried out in 0,9% aqueous sodium chloride in order to simulate the aggressivity of the oral cavity, using open circuit potential measurements, polarization curves and electrochemical impedance. The corrosion resistance exhibited by alloys can be associated with formation of a corrosion layer and seems to be dominated by the presence of a porous layer in the surface.

Neste trabalho realizou-se um estudo de caracterização metalúrgica do amálgama dentário Dispersalloy produzido pela empresa Dentsply Ind. e Com. Ltda., por meio da análise da sua composição química, utilizando-se a técnica espectrofotométrica de absorção atômica, procedendo-se em seguida, a análise metalográfica, utilizando-se microscopia eletrônica de varredura. A seguir, foi realizado um estudo de resistência à corrosão, utilizando-se técnicas eletroquímicas tradicionais de polarização e espectroscopia de impedância, em meio e condições que simulam a agressividade do ambiente bucal. Para isto, as amostras foram obtidas pelo processo de amalgamação mecânica, método usualmente utilizado pelos dentistas no próprio consultório, para a preparação da restauração dentária. A liga comercial Dispersalloy, representante da categoria de amálgamas de alto teor de cobre, tipo fase dispersa, foi escolhida para este estudo por ser bastante comercializada nos mercados nacional e internacional e, também por ser uma liga metálica moderna, bastante estudada, mas que ainda sofre corrosão no meio bucal.

The corrosion of dental amalgam in aqueous media was interpreted by means of a.c. impedance techniques and anodic polarization. The Nyquist and Bode diagrams are influenced by the porous structure of the amalgams, the surface film formation and the adsorption of intermediates. In general, the impedance spectra are rather complex and very difficult to interpret. The Dispersalloy amalgam (high copper, dispersion type alloy) was characterized by scanning electron microscopy and energy dispersive X ray analysis. The chemistry analysis was determined by atomic absorption spectrophotometry. Although high copper amalgams as a group show superior physical properties and clinical performance to low copper amalgams, a high copper content does, not necessarily mean improved clinical performance. Neverthelless, they too, corrode in the mouth.