Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2006. / Includes bibliographical references (p. 43-46).

Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2007. / Dr. J. David Frost, Committee Chair ; Dr. G. Wayne Clough, Committee Co-Chair ; Dr. William F. Marcuson III, Committee Member ; Dr. Paul W. Mayne, Committee Member ; Dr. Susan Burns, Committee Member.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Electrical engineers have responded to the increasing demand for circuit speed and functionality by reducing transistor feature size and increasing on-chip transistor density. Consequently, interconnect density, both on-chip and the system level is also increasing. Increasing circuit speed translates into shorter clock cycles and signals with faster edge rates, which have multi-GHz bandwidth. Densely packed parallel interconnects will cause signal integrity problems not only due to the increase in crosstalk noise but also due to the intrinsic low pass filter characteristics of the interconnects. The lossy nature of the interconnects is also going to increase due to metal surface roughness at higher frequencies, which will further degrade the signal quality at the receiver input. Embedded Patterned Layer (EPL), which is a patterned floating metal layer between a signal trace and its return path shows promise in reducing far-end crosstalk (FEXT). EPL also allows designers to modify the characteristic impedance of interconnects by varying the different physical parameters of the EPL. This dissertation analyzes the effect of EPL on conductor backed coplanar waveguides (CB-CPW). CB-CPWs excite higher order modes at high frequencies, so work was done to understand the effect of different ground via fence parameters in suppressing the higher modes which helps increase the interconnect bandwidth. A CB-CPW with ground via fence is called a grounded coplanar waveguide (GCPW). A very basic lumped element model transmission line model was developed to account for the effect of floating metals near a transmission line. This model was then used to explain the effect of EPL on a GCPW with large bandwidth. EPL reduces the characteristic impedance of the transmission line. Engineers can then design narrow high impedance transmission lines and use EPL to reduce the impedance to a desired value. This also allows reduction in crosstalk by increasing the spacing between the transmission lines. The EPL also reduced the differential impedance of a grounded conductor backed edge coupled coplanar waveguide, when it was used for differential signaling. Care must be taken to make sure that the EPL is symmetric to both the legs of the differential pair to avoid differential to common mode energy conversion, which can cause electromagnetic interference (EMI) problems. EPL reduced FEXT while increasing near-end crosstalk (NEXT), when the coupled transmission line system was used for single ended signaling. Finally, a statistical method for modeling transmission line metal surface roughness in three dimensional (3D) full wave electromagnetic solvers was developed to account for increased attenuation in transmission lines, at high frequencies, due to metal surface roughness.

A doença cárie pode ser tratada com tratamento preventivo e ou tratamento restaurador. Para o tratamento preventivo, pode-se lançar mão da utilização do flúor, sendo sua utilização bastante difundida na Odontologia como eficaz método de promoção de saúde bucal. Já para o tratamento restaurador, utilizam-se materiais restauradores, sendo os compósitos odontológicos umas das principais escolhas entre os materiais restauradores estéticos usados na Odontologia. O objetivo deste estudo foi avaliar a ação de soluções fluoretadas na estabilidade de cor, rugosidade de superfície e análise qualitativa por microscopia eletrônica por varredura de compósitos odontológicos. Após confecção e polimento, os corpos de prova foram imersos em água destilada (controle), flúor fosfato acidulado (1,23%), gel fluoretado neutro (2%) e solução de flúor para bochechos diário (0,05%) por períodos de simulação correspondentes a 1 a 5 anos de uso clínico da solução fluoretada. Foram realizadas leituras de cor (&Delta;E), rugosidade de superfície (Ra) e microscopia eletrônica de varredura previamente e posteriormente a cada ano de ciclagem com as soluções fluoretadas estudadas. Após análise estatística (3-way ANOVA com medidas repetidas Bonferroni nível de significância em p<0.05), observou-se que todos os compósitos estudados apresentaram discreta alteração de cor, dentro do limite clinicamente aceitável (&Delta;E<3,3), sendo crescente de acordo com os anos de simulação clínica de 1 até 5 anos. Quanto à rugosidade, observou-se um padrão de comportamento não homogêneo, sendo, após 5 anos de simulação de uso clínico das soluções fluoretadas, menor que a rugosidade de superfície necessária para causar um aumento da retenção de biofilme dentário (Ra>0,2 &mu;m) para todos os compósitos analisados. A análise das fotomicrografias demonstrou o aparecimento de pequenas depressões na superfície das amostras e penetração de água (solvente) no interior dos compósitos diretos. Conclui-se que a alteração de cor dos compósitos foi clinicamente aceitável e a alteração de rugosidade de superfície não é clinicamente significante após imersão em todas as soluções fluoretadas e tempos estudados. / Dental caries can be treated with preventive treatment or restorative treatment. For preventive treatment, we can resort to the use of fluoride, and its widespread use in Dentistry as an effective method of promoting oral health. As for the restorative treatment, are used restorative materials, dental composites are one of the first choices among the materials used in aesthetic restorative dentistry. The aim of this study was to evaluate the effect of fluoride solution in color stability, surface roughness and qualitative analysis by scanning electron microscopy of dental composites. After preparation and polishing, the specimens were immersed in distilled water (control), acidulated phosphate fluoride (1.23%), neutral sodium fluoride gel (2%) and fluoride mouthwashes for daily (0.05%) for periods simulation corresponding to 1 to 5 years of clinical use of fluoride solution. Readings were taken in color (&Delta;E), surface roughness (Ra) and scanning electron microscopy before and after each year of cycling with the fluoride solution studied. After statistical analysis (3-way repeated measures ANOVA - Bonferroni - a significance level of p<0.05), was observed that all the composites studied showed a slight color change, within clinically acceptable (&Delta;E<3.3), being increased according to the years of clinical simulation from 1 to 5 years. As for the roughness, there was a pattern of behavior is not homogeneous, and, after five years of simulated clinical use of fluoride solution, smaller than the surface roughness required to cause an increased retention of dental plaque (Ra>0.2 &mu;m) for all composites analyzed. The analysis of the photomicrographs showed the appearance of small depressions on the surface and penetration of water (solvent) within the direct composites. We conclude that the color change of the composites was clinically acceptable and the surface roughness change is not clinically significant after immersion in all fluoride solution and times studied.

Made available in DSpace on 2014-06-11T19:28:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-11Bitstream added on 2014-06-13T20:37:54Z : No. of bitstreams: 1 pereira_pc_me_sjc.pdf: 1955962 bytes, checksum: 199a3b76eadceaedbf2923a8f9d4c65f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste estudo foi avaliar o efeito da vitrificação e do polimento na rugosidade superficial e formação in situ de biofilme dentário inicial, após simulação da escovação, em cerâmica policristalina de zircônia parcialmente estabilizada por ítrio (Cercon® Zirconia, Dentsply Ceramco). Amostras foram divididas em: (C) controle – sem tratamento; (V) vitrificadas; (PS) polidas com pontas de silicone diamantadas. Metade das amostras foi submetida à simulação de escovação (400.000 ciclos). Análises da rugosidade superficial (Ra e Rz) foram realizadas antes e após os tratamentos superficiais e escovação. Dez voluntários selecionados com adequado padrão de higiene bucal receberam dispositivos oclusais individualizados para a fixação das amostras na face vestibular. Após 8 horas em ambiente bucal, as amostras foram removidas do dispositivo e avaliadas em MEV (n=5) e MCVL (n=10). A análise em MEV foi realizada por meio da seleção aleatória de cinco campos (20 x 25 μm) para cada amostra para análise descritiva do material celular/acelular depositado e da topografia superficial. Para análise em MCVL, foram captadas imagens em lentes ópticas com aumento de 10 x/ 0.3 para visualização de toda a amostra e aumento de 63 x/ 0.3 (imagens 3D com secções ópticas de 0,8 μm) para análise de biovolume e espessura média de biofilme. O software COMSTAT quantificou as imagens obtidas em MCVL. Os dados obtidos de rugosidade (μm) foram submetidos à Análise de Variância (dois fatores) e teste de Dunnett (5%). Biovolume e espessura de biofilme foram analisados pelo teste de Kruskal-Wallis e Mann-Whitney. O grupo V apresentou maiores valores de rugosidade superficial, espessura média e biovolume de biofilme, em presença de escovação simulada. O fator escovação não foi preponderante para o aumento da rugosidade superficial. Houve correlação significativa entre... / The aim of this study was to evaluate the effect of the glaze and polishing in the surface roughness and early dental biofilm formation, after toothbrushing simulation, in tetragonal zirconium polycrystal stabilized with yttrium ceramics (Cercon® Zirconia, Dentsply Ceramco). Ceramics samples were divided in three groups: control - not glazed (C); glazed (G); polishing with diamonds silica tip (ST). Half samples was submitted to toothbrushing simulation (400.000 cycles). Analyses of surface roughness (Ra and Rz) were carried before and after the superficial treatments and toothbrushing. Ten volunteers selected with high level of oral hygiene were selected for this study. Oral devices covering the crowns of the upper premolars and molars were fabricated for each participant and ceramic samples were fixed on the vestibular zones of the devices. After 8 hours in situ, the samples were removed from device and analyzed in SEM (n=5) and CLSM (n=10). To SEM analysis was selected means of the random election of five fields (20 x 25 μm) for each sample for descriptive analysis of the deposited cellular material/to acelular and the superficial topography. For analysis in CLSM were used for architecture visualization and lenses of 63x/0.13 for COMSTAT analysis and quantification. The resulting sets of confocal optical sections were collected by microscopy software as stacks of images 3-D images were obtained for analysis of biovolume and average thickness of biofilm. The data of surface roughness (μm) were submitted to analysis of variance (two factors) and Dunnett’s test (5%). Biovolume and mean thickness biofilm were analyzed by Kruskal-Wallis and Mann-Whitney’s test. The G Group presented greaters values of surface roughness, average thickness and biovolume of biofilm, in toothbrushing presence... (Complete abstract click electronic access below)

Depuis de nombreuses années, l'industrie microélectronique s'est engagée dans une course à l'augmentation des performances et à la diminution des coûts de ses dispositifs grâce à la miniaturisation de ces derniers. La génération de ces structures de petites dimensions repose essentiellement sur l'étape de lithographie. Dans cette optique, plusieurs techniques de lithographie nouvelle génération (NGL) sont en cours de développement afin de pouvoir répondre aux besoins de l'industrie pour les nœuds technologiques inférieurs à 20 nm. Parmi elles, les solutions de lithographie à faisceaux d'électrons multiples semblent très prometteuses grâce à leur écriture directe sans masque (ML2), ainsi que leur coût et encombrement réduits. Le CEA-LETI s'est associé à l'entreprise Mapper Lithography basée aux Pays-Bas afin d'aider au développement d'une technologie de lithographie électronique à faisceaux d'électrons multiples basse énergie (d'énergie 5 keV). Les travaux de thèse de ce manuscrit visent à contribuer au développement de cette technologie qui pourrait à terme permettre de réaliser des dispositifs CMOS pour les nœuds technologiques actuels et futurs. L'intégration d'une nouvelle technique de lithographie dans l'industrie repose sur 3 grands critères du procédé lithographique, la production horaire (sensibilité), la résolution (taille minimale des structures réalisées) et la rugosité de ligne. La rugosité de ligne est devenue l'un des paramètres les plus critiques limitant à l'heure actuelle la miniaturisation et pour cause cette dernière impacte de manière négative les performances des dispositifs. Alors que l'ITRS préconise une rugosité de ligne inférieure à 1.7 nm pour les futurs nœuds technologiques inférieurs à 20 nm, les lithographies actuelles ne permettent pas d'obtenir des rugosités inférieures à 4-5 nm. Les travaux de cette thèse visent la minimisation de la rugosité de ligne de résine imprimée par lithographie électronique en proposant des stratégies alternatives d'écriture ou en modifiant les empilements de matériaux sous-jacents la résine, ou encore par l'introduction de traitements post-lithographiques tels que des recuits thermiques ou des traitements plasma. Les études ont montré qu'en combinant une stratégie d'écriture et un traitement plasma à base de dihydrogène une réduction de 41% du LWR pouvait être obtenue. / For decades, the growth of the Semiconductor Industry (SI) has been driven by the paramount need for faster devices at a controlled cost primarily due to the shrinkage of chip transistors. The performances of future CMOS technology generations still rely on the decrease of the device dimensions. However, the photolithography is, today, the limiting factor for pattern miniaturization and the technology has been at a standstill since the development of 193-nm water-based immersion lithography. Moreover, another parameter limiting further semiconductor scaling is the transistor gate linewidth roughness (LWR), i.e. the standard deviation of the gate critical dimension (CD) along the line. The LWR needs to be controlled at the nanometer range to ensure good electrical performances of the future CMOS device. The lithography step is again identified as the root cause of the gate LWR. Indeed, the significant LWR (4-5 nm) of the patterns printed by photolithography is transferred into the gate during the subsequent plasma etching steps, resulting in a final gate LWR far above the sub-2 nm LWR targeted for the sub-20 nm technological nodes. In order to continue scaling down feature sizes of devices, the semiconductor industry is waiting for the maturity of next generation lithographies (NGL). Among NGL, one can find the promising mask-less direct-write techniques (ML2) in which multiple electron beam lithography (multibeam lithography) is regarded as a serious candidate for providing high resolution structures at a low cost. The firm MAPPER Lithography, associated with CEA-LETI is working on the development of such a technology. The aim of this work is to contribute to the development of a low energy (5 keV) multibeam technology and to focus on the improvement of the LWR of the printed patterns. Several process parameters have been investigated to decrease the LWR: the effect of a specific writing strategy, the influence of the under layers and the introduction of post-lithographic treatments such as plasma treatments or thermal annealing. This work has shown that by combining a biased writing strategy with H2 plasma treatment, a 41% LWR decrease could be obtained. Although this performance is still above the ITRS requirements, this work opens the pace for LWR optimization with multi-beam lithography.

Neste trabalho foram investigadas as influências de alguns dos principais fatores do torneamento sobre o acabamento da superfície, rugosidade, tensões residuais e microdureza em um conjunto de amostras. Foram analisadas barras de aço ABNT 1045 torneadas e utilizou-se a técnica de planejamento de experimentos (DoE) para formar trinta e duas diferentes combinações de fatores, analisar suas interações e sua influência no acabamento de cada amostra. Os fatores de usinagem investigados foram: (1) avanço, (2) velocidade de corte, (3) raio de quina, (4) ângulo de saída e (5) posição axial. Analises fatoriais foi avaliaram a influência dos cinco fatores na rugosidade média (Ra) e a eficácia de cada conjunto de fatores em obter o acabamento alvo (Ir). Utilizou-se a técnica de difração de raios-X para medir as tensões residuais em sete das dezesseis amostras. As tensões foram medidas na superfície e em profundidades de 5, 10, 20, 50 e 75 μm com auxílio de ataque eletrolítico. Por fim foi realizada análise metalográfica da superfície usinada e perfil de microdureza. Os resultados mostraram que o avanço e o raio de quina possuem elevado efeito padronizado em ambas as análises. Porém, para ambos, enquanto que a aplicação de um menor avanço (ou maior raio de quina) produziu superfícies com baixo Ra, por outro lado também prejudicou a eficácia do torneamento pois contribuiu para obtenção de rugosidade significativamente maior que a teórica. Já o fator velocidade de corte quando teve seu valor elevado foi benéfico ao processo em ambas as análises. Não foi encontrada relevância da região de medição da rugosidade sobre Ra. As tensões residuais sofreram elevada influência dos fatores avanço e velocidade de corte, enquanto o ângulo de saída e o raio de quina mostraram pequeno efeito. A qualidade do acabamento da superfície, regular ou irregular, apresentou relação direta com o mecanismo de geração das tensões residuais. O perfil de microdureza medido mostrou valores de dureza elevados nas amostras com superfície regular e em regiões com maior tensão residual. / This paper investigated the influence of some of the main turning parameters in surface finishing, roughness, residual stress and microhardness of turning samples. Design of experiments (DoE) approach controlled the machining factors of the 0.45%C (ABNT 1045) steel bars samples. DoE also were applied to organize a total of thirty-two parameters combination, analyze its interactions and influences in each sample’s surface finish. Machining parameters investigated were: (1) feed rate, (2) cutting speed, (3) nose radius, (4) rake angle and (5) region of roughness measurement. Factorial analysis evaluated the influence of those five parameters in the average roughness (Ra) and the accuracy of each parameters combination to achieve the expected surface finish (Ir). The X-ray diffraction technique was used to measure the residual stresses in seven out of sixteen samples. The tensions were measured at their surface and at depths of 5, 10, 20, 50 and 75 μm by means of electrochemical material removal. In addition metallographic analysis of the machined surface and microhardness profile were conducted. Results showed that parameters as feed rate and nose radius have strong standardized effect in both factorial analysis. Results shown that reduction of the feed rate (or increase in nose radius) were able to produce lower roughness average (Ra) but, on the other hand, it also contribute to generate a surface roughness significant higher than theoretical roughness. The increase in cutting speed was beneficial to both, achieving a lower roughness average and improving process accuracy. The region of roughness measurement was found not significant to influence Ra. The residual stresses were strongly influenced by the feed rate and cutting speed factors, while the rake angle and nose radius showed small effect. The quality of the surface finish, regular or irregular, was directly related to residual stresses generation mechanism. The microhardness profile shown higher microhardness in samples with regular surface finish and in depths with higher residual stress.

O estudo de usinabilidade de um material é muito importante para a determinação das características de fabricação por usinagem. Este estudo se aplica ao aço inoxidável martensítico AISI 420 C endurecido, usado na fabricação de peças de alta precisão, instrumentos cirúrgicos, eixos, turbinas e cutelaria. Deste modo, realizaram-se investigações utilizando corpos de prova endurecidos (têmpera e revenimento) com durezas de (48  1) e (53  2) HRC no torneamento a seco utilizando ferramentas de metal-duro classe ISO S com grãos extrafinos e revestimento PVD. Para estes corpos de prova variaram-se a velocidade de corte e o avanço e avaliaram-se as forças de usinagem e as tensões residuais geradas na peça. Para o material com 53 HRC, também foram analisadas a vida da ferramenta e a rugosidade. Na análise dos resultados obtidos para o material com 48 HRC, as tensões residuais tornaram-se menos compressivas (circunferencial) e mais trativas (axial) com o aumento do avanço. Além disso, os menores valores de tensão residual foram gerados utilizando menor avanço com maior velocidade de corte. Nos ensaios para o material a 53 HRC, o tempo de vida da ferramenta ficou entre 100 e 350 min para as condições ensaiadas. Os desgastes de flanco e entalhe foram evidenciados em todas as situações. O flanco da ferramenta também apresentou adesão de material da peça em todas as condições. Ao analisar os insertos em seu fim de vida, constatou-se que os mecanismos de desgastes predominantes foram a abrasão e o atrittion. Nas condições mais severas, a superfície da ferramenta exibiu trincas mecânicas e a camada subsuperficial da peça apresentou modificações microestruturais. Os perfis e os parâmetros de rugosidade registrados foram afetados pelo desgaste ao longo da vida da ferramenta. Com relação às tensões residuais circunferenciais geradas com a ferramenta nova, estas foram, em sua maioria, tensões de compressão. Com a progressão do desgaste de flanco, houve um aumento dos valores das tensões (de compressivas para menos compressivas ou até mesmo trativas). Já para as tensões axiais, os valores mostraram a tendência de se manterem compressivos. Observou-se para os perfis de tensões analisados que as tensões residuais foram compressivas e dependeram da profundidade da camada subsuperficial. Portanto, dentro das condições estudadas, conclui-se que peças de AISI 420 C endurecido podem ser fabricadas por torneamento de acabamento com ferramentas de metal-duro, permitindo obter vida longa para a ferramenta de corte, baixos valores de rugosidade, bem como valores de tensão residual compressiva, que são dados de usinabilidade importantes para esse material. / The study of the material’s machinability is very important for the determination of important machining properties. This logic applies to hardened martensitic stainless steel AISI 420 C used in the manufacture of high precision parts, surgical instruments, shafts, turbines and cutlery. In this way, investigations were carried out using hardened workpieces (quenching and tempering) with hardness of (48  1) and (53  2 HRC) in dry turning using ISO-S grade carbide tools with extra-fine grains and PVD coating. For these workpieces, the cutting speed and the feed rate were varied and the machining forces and the residual stresses generated in the part were evaluated. For the material with 53 HRC, the tool-life and the surface roughness were also analyzed. In the analysis of the results obtained for the material with 48 HRC, residual stresses become less compressive (circumferential direction) and more tensile (axial direction) with increasing feed-rate. Moreover, smaller values of residual stress were generated using lower feed-rate at higher cutting speed. In the tests for the material at 53 HRC, the tool-life was between 100 and 350 min for the conditions tested. Flank and notch wear were evidenced in all situations. The flank face of the tool also showed adhesion of the workpiece material under all cutting conditions. When analyzing the inserts at their end of life, it was verified that the main mechanisms of tool wear were abrasion and attrition. In addition, under the most severe cutting conditions, the flank face of the tool exhibited mechanical cracks and the subsurface layer of the workpieces presented microstructural modifications. The registered profiles and roughness parameters were affected by wear during the tool-life. With respect to the circumferential residual stresses generated with the fresh tool, these were mostly compressive stresses. With the progression of tool flank wear, there was an increase in the values of the residual stress (from compressive to less compressive or even tractive). For the axial residual stresses, the values showed a tendency to remain compressive. It was observed for the residual stress profiles analyzed that the residual stresses were compressive and depended on the depth of subsurface layer. Therefore, within the cutting conditions considered, it can be concluded that hardened martensitic stainless steel AISI 420 C parts can be manufactured by finishing turning with carbide tools, allowing long tool-life, low surface roughness values, as well as compressive residual stress values, which are important machinability information for this material.

O objetivo deste estudo foi avaliar in vitro o efeito do ácido cítrico líquido, ácido clorídrico na forma de gás e líquido na evolução do processo erosivo associado ou não a abrasão do tecido dentinário. Foram simuladas situações diárias que ocorrem na Doença do Refluxo Gastroesofágico (DRGE) e no consumo de alguns tipos de refrigerantes. O estudo foi fatorial 3 X 2 , tendo como fatores de estudo: exposição ao ácido em 3 níveis (ac. cítrico, ácido clorídrico na forma líquida e gasosa), abrasão em 2 níveis (sem e com escovação), o tempo foi analisado individualmente por ácido empregado para verificar a evolução do processo erosivo. Foram obtidos 60 espécimes de dentina (3 X 3 mm) a partir do terço cervical da raiz de incisivos bovinos, que foram isolados com resina composta, exceto a face a ser exposta aos desafios erosivos, que foi lixada e polida para planificar a superfície e remoção do cemento, metade desta face foi isolada com fita de silicone adesivo (controle). Os espécimes foram aleatoriamente divididos em 6 subgrupos (n=10). Foi realizado desafio erosivo com HCl líquido, 0,6%, pH=2; com gás do HCl , pH=2 ambos a 37ºC e com ácido cítrico líquido, 0,3%, pH=2,7, com temperatura ambiente (22ºC). A exposição foi de 20 segundos para os desafios com ácido clorídrico e por 5 minutos para o ácido cítrico em cada ciclo, repetidos 6 vezes. Após cada desafio erosivo, os corpos de prova ficaram imersos em saliva artificial por 1 hora, a 37°C, realizada ou não a abrasão e, em seguida, foram obtidas as imagens para as análises de perfil de desgaste, rugosidade de superfície, área, número e tamanho dos túbulos dentinários expostos. A abrasão foi realizada com escova elétrica por 10s e 200gf com dentifrício. Os dados foram submetidos aos testes ANOVA e Tukey (p<0,05). Pode-se observar que os ácidos cítrico e clorídrico (liquido) promoveu maior desgaste (p<0,05) do que o gás. A rugosidade foi mais intensa no ácido cítrico (p<0,05). Na morfologia da dentina o ácido clorídrico foi que promoveu maiores alterações (p<0,05) O fator tempo foi semelhante para todos os grupos e a escovação reduziu a rugosidade. Pode-se concluir que os diferentes ácidos promoveram um processo erosivo distinto, sendo que o gás de ácido clorídrico promoveu menor desgaste e o ácido cítrico, a maior rugosidade e o ácido clorídrico líquido promoveu maior alteração morfológica dos túbulos dentinários. / The aim of this study was to evaluate in vitro the effect of liquid citric acid, hydrochloric acid in the form of gas and liquid in the evolution of erosion with or without abrasion of the dentin. Everyday situations were simulated occurring in Gastroesophageal Reflux Disease (GERD) and use of some types of soft drinks. The study was a factorial 3 x 2, with the study of factors: acid exposure in three levels (citric acid, hydrochloric acid in liquid and gaseous form), abrasion on two levels (with and without brushing), the time was analyzed individually by acid used to verify the evolution of erosion. There were obtained 60 samples of dentin (3 x 3 mm) from the cervical third of bovine incisors roots, which were lined with composite resin except the side to be exposed to erosive challenges, which was sanded and polished to plan surface and removal of cement, half of the face was covered with silicone adhesive tape (control). The specimens were randomly divided into 6 subgroups (n = 10). Erosive challenge was performed with liquid HCl, pH = 2; with gas HCl, 0,6%, pH = 2 both at 37°C and with liquid citric acid, 0,3%, pH 2.7, room temperature (22 ° C). Exposure was for 20 seconds with hydrochloric acid and challenges for 5 minutes to citric acid at each cycle, repeated 6 times. After each erosive challenge, the samples were immersed in artificial saliva for 1 hour at 37 ° C, performing or not the abrasion and then take the images to the wear profile analysis, surface roughness were obtained area , number and size of exposed dentinal tubules. The abrasion was performed with electric brush for 10 seconds and 200gf with toothpaste. The data were submitted to ANOVA and Tukey test (p <0.05). The time factor was similar in all groups and brushing reduced roughness. It can be seen that citric and hydrochloric acid (liquid) promoted increased wear (p <0.05) than the gas. The roughness was more intense citric acid (p <0.05). The morphology of the dentin hydrochloric acid was to the highest changes (p <0.05). The time factor was similar in all groups and brushing reduced roughness. It can be concluded that the different acids promoted a distinct erosion process, wherein hydrochloric acid gas promoted less wear and citric acid greater roughness and liquid hydrochloric acid promoted greater morphological changes of dentinal tubules