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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Anticipatory Electromyogram-Torque Estimation and Effect of Whitening Bandwidth

Koirala, Kishor 23 April 2013 (has links)
The electromyogram has numerous applications in engineering and science. One specific application is to model a system for the torque generated by the elbow joint. This application has been long studied and applied in controller designs for artificial prosthetics limbs. Previous research had shown that nonlinear and multiple channel whitened EMG signal models gave the best EMG to torque estimates compared to linear un-whitened models. This thesis describes the methodologies for predicting the torque into the future up to 1 second. Four specific types of finite impulse response models (linear and nonlinear, single channel un-whitened and multi-channel whitened) are compared based on the EMG-based predicted torque and the actual torque. The errors were measured as the difference between actual and predicted torque. It was observed that the error was mostly constant at the minimum error value between 0 and 80 ms for all four models, with the lowest error being 5.48 % maximum voluntary contraction (MVC) flexion. Further comparison was performed between different lower order models and a Butterworth second order model for predicting torque ahead in time. Such models are common in the literature. This thesis separately investigates the effect of band limiting the whitened EMG signal and using the advanced EMG processors for estimating the torque. Whitened EMG data were passed through a low pass filter with selectable cutoff frequency from 2048 Hz down to 20 Hz to limit the whitened band width. It was observed that the error was not significantly different for bandwidths down to approximately 400-600 Hz, grew gradually as the band width further decreased to 200 Hz, beyond which the error increased sharply. It can be inferred that for this particular study consisting of lower contraction levels, there is no significant power usable for whitening in the EMG signal at higher frequencies, providing an opportunity for lower sampling rate, effective noise suppression, better signal to noise ratio and implementation of low cost electrodes. This research work lead to two conference paper publications at the 2013 IEEE 39th Annual Northeast Bioengineering Conference. Two journal papers are in the writing and preparation stage which will be submitted after their completion.
2

Advanced Electromyogram Signal Processing with an Emphasis on Simplified, Near-Optimal Whitening

Wang, He 22 November 2019 (has links)
Estimates of the time-varying standard deviation of the surface EMG signal (EMGσ) are extensively used in the field of EMG-torque estimation. The use of a whitening filter can substantially improve the accuracy of EMGσ estimation by removing the signal correlation and increasing the statistical bandwidth. However, a subject-specific whitening filter which is calibrated to each subject, is quite complex and inconvenient. To solve this problem, we first calibrated a 60th-order “Universal” FIR whitening filter by using the ensemble mean of the inverse of the square root of the power spectral density (PSD) of the noise-free EMG signal. Pre-existing data from elbow contraction of 64 subjects, providing 512 recording trials were used. The test error on an EMG-torque task based on the “Universal” FIR whitening filter had a mean error of 4.80% maximum voluntary contraction (MVC) with a standard deviation of 2.03% MVC. Meanwhile the subject-specific whitening filter had performance of 4.84±1.98% MVC (both have a whitening band limit at 600 Hz). These two methods had no statistical difference. Furthermore, a 2nd-order IIR whitening filter was designed based on the magnitude response of the “Universal” FIR whitening filter, via the differential evolution algorithm. The performance of this IIR whitening filter was very similar to the FIR filter, with a performance of 4.81±2.12% MVC. A statistical test showed that these two methods had no significant difference either. Additionally, a complete theory of EMG in additive measured noise contraction modeling is described. Results show that subtracting the variance of whitened noise by computing the root difference of the square (RDS) is the correct way to remove noise from the EMG signal.
3

Race matters: race, telenovela representation, and discourse in contemporary Brazil

Joyce, Samantha Nogueira 01 May 2010 (has links)
In Race Matters: Race, Telenovela Representation, and Discourse in Contemporary Brazil I investigate the primetime telenovela Duas Caras (2008), examining how different factors such as narrative, audience reaction, as well as media criticism and commentary played a dynamic role in creating a meta-discourse about race in contemporary Brazil. In a larger sense, I examine how the social discourse about contemporary race relations and racism in that country were circulated, constructed and reconstructed during the time the program aired. Additionally, I explore the role of the media, particularly the telenovela, in debunking the idea that Brazil is a racial democracy. Secondly, the research incorporates the Brazilian notion that telenovelas are "open texts", meaning they are co-authored by a variety of industrial, creative, cultural and social actors, into a methodological approach that expands the traditional idea of textual analysis. In addition to reading the telenovela text itself, this study investigates the production process, audience responses and broader media coverage. Thus, the public discourse about the telenovelas is a key part of the text itself.
4

The discourse anaylysis in the Internet--Take the Beauty Salon community for example

Yang, Jo-I 24 July 2008 (has links)
The standards of beauty always change in every generation in Taiwan, but there is only one standard still has strong impact on people, that is:¡¨ having white complexion¡¨. People say: ¡§A white complexion is powerful enough to hide seven faults.¡¨ The reason of ¡§whitening¡¨ is important because of the different powers which compete with each other to decide the meaning behind the discourse of ¡§whitening¡¨. The concept of ¡§Whitening¡¨ is from the promotion of beauty industry. What¡¦s more, this concept also made a strong impact through the media on people who live in Taiwan. Thus, to understand how the media delivery the ¡§whitening¡¨ concept is very important, especially through the most important media--- Internet in this generation. The main purpose of this research is to find out the process of developing the discourse of ¡§whitening¡¨ within the on-line Beauty Salon community and the context behind the discourse in Taiwan. Another purpose is to seek out the minority discourse which seldom appear within the mass media and also provide the ability of reflectivity thinking. The main structure of this research base on the critical concept of ¡§Knowledge/ Power¡¨ from the post-modern scholars: Gramsci, Foucault and the post-colonialism scholar---Said to discuss how the ¡§whitening¡¨ discourse is developed by the ¡§center¡¨(ex. doctor, expert and business ) and ¡§margin¡¨(ex.net pal)within the on-line beauty community. This research choose qualitative research method to do the context analysis in the most popular on-line community which is also the biggest BBS in Taiwan---¡§PTT ¡¨ and choose ¡§Beauty Salon¡¨ community within PTT as the research field. The results show that the ¡§Whitening ¡¨ discourse is a knowledge system within ¡§Beauty Salon¡¨ community and developed by the hierarchy relationship form doctors, skin-care experts, cosmetic businesses and cosmetic sales. What¡¦s more, the role of ¡§black skin¡¨ is ¡§the other¡¨ and has the inferiority within this knowledge system of whitening discourse. And the voice of supporting black skin also disappeared within Beauty Salon community. To compare with Beauty Salon community, there was another temporary skin-care on-line discussion bard founded by YAHOO in March 2008. And it has less limit and more open to express their opinions. This research found that there is the voice of supporting black skin appearing within this field and also using the strategy of different mimicry to ¡§write back¡¨ the discourse developed by majority. This research found that if there are only few powers to develop the discourse, the discourse will become one-dimension and hardly to see the different other opinion against the mainstream or the ¡§center¡¨ opinion. This also tells us that the limit of structure from the oligopoly powers in the Internet will expropriate people¡¦s chance and freedom to choose and contact the different voices, and this situation is worthy to reflect.
5

The Remineralization Potential of Nano-Hydroxyapatite in Hydrogen Peroxide Whitening Mouthwash

Mcdermott, Morgan Marie 26 April 2016 (has links)
No description available.
6

Avaliação clínica da efetividade de géis clareadores de baixa concentração no clareamento em consultório de dentes polpados, com e sem o emprego de fonte de luz híbrida e condicionamento ácido prévio do esmalte

Michielin, Martha Beteghelli 08 May 2015 (has links)
O objetivo deste estudo clínico randomizado duplo cego boca-dividida foi avaliar, in vivo, a efetividade do condicionamento ácido prévio do esmalte e de géis clareadores a base de peróxido de hidrogênio (PH) de baixa concentração, associados a fontes de luz híbrida (LH), tendo como variáveis de reposta: sensibilidade dental, fluxo sanguíneo pulpar, grau de mudança e estabilidade de cor ao longo de 6 meses. Trinta e seis voluntários que se encaixaram nos critérios de inclusão e exclusão foram selecionados e randomizados em 3 grupos (n=12), de acordo com o protocolo clareador a ser utilizado. Dentro de cada grupo, um dos hemiarcos foi aleatoriamente selecionado para a realização do condicionamento ácido do esmalte, previamente a aplicação do gel clareador. Os géis que compunham os três protocolos clareadores foram: PH a 10% (experimental) associado a LH a base de LED violeta + laser de diodo (experimental); PH a 15% associado a LH a base de LED azul + laser de diodo; e PH a 35% sem ativação com fonte de luz. A sensibilidade foi avaliada com a escala VAS; a fluxometria pulpar, com o sistema Laser Doppler; e a cor pelo cálculo do ?E via espectrofotômetro. Os dados foram tratados pela análise de variância de medidas repetidas (ANOVA), Tukey e teste de Friedman (p<0,05). Com relação à sensibilidade, foram encontradas diferenças significativas na interação tempo e grupo, mas não com relação ao ácido. Quanto à vascularização pulpar, o efeito de grupo não foi rejeitado, sendo o grupo de PH a 35% o que apresentou as menores medianas para as variações percentuais, porém os efeitos de ácido e tempo não foram significativos. Quanto à cor, diferenças significantes foram encontradas entre os grupos, mas não com relação ao uso do ácido, sendo o PH a 35% o que promoveu maior aumento do ?E. Conclui-se assim que o condicionamento ácido não foi capaz de favorecer a efetividade do clareamento em função do grau de mudança e estabilidade de cor, bem como não aumentou a sensibilidade e o fluxo sanguíneo da polpa dental. A concentração dos agentes clareadores foi determinante para o grau de mudança de cor e demonstrou influenciar a sensibilidade e o fluxo sanguíneo pulpar. / The aim of this double blind split-mouth randomized clinical study was to evaluate, in vivo, the effectiveness of prior acid etching on enamel and low concentration bleaching gels based on hydrogen peroxide (HP) associated with hybrid light (HL) sources, having as response variables: dental sensitivity, dental pulp vascularization and degree of color change and stability over 6 months. Thirty-six volunteers in agreement with the inclusion and exclusion criteria were selected and randomly divided into 3 groups (n = 12) according to the bleaching protocol to be used. Within each group, one of the sides was randomly selected for the execution of acid etching prior to the gel application. The three bleaching gels were: 10% HP (experimental) associated with HL-based violet LED/laser (experimental); 15% HP associated with HL-based blue LED/laser; and 35% HP without light activation. Sensitivity was evaluated with the VAS scale; pulp flowmetry by the use of the Laser Doppler system; and efficacy was evaluated by calculating the ?E via a spectrophotometer. Data were analyzed by analysis of variance for repeated measures (ANOVA), Tukeys and Friedman tests (p<0.05). Regarding sensitivity, significant differences were found in the interaction between the application time and group but not regarding etching. For dental pulp flowmetry, the group effect was not rejected, where the 35% HP showed the lowest medians for the percentile variations, but the effects of etching and time were not significant. For color, significant differences were found between the groups, but not between the sides with and without acid etching, where the 35% HP gel promoted the highest increase in ?E. It is therefore concluded that the etching was not able to favor the effectiveness of whitening due to color variation and stability, as well as not increasing sensitivity or pulp blood flow. The concentration of bleaching agents determined the degree of color change and influenced the sensitivity and blood flow of the dental pulp.
7

Synthèse chimio-enzymatique de thioglycoconjugués ayant des applications cosmétiques / Chemo-enzymatic synthesis of thioglyconconjugates for cosmetic applications

Peyrot, Cédric 16 November 2017 (has links)
Face à l’apparition croissante de troubles pigmentaires liés à l’exposition aux UV, le développement de nouveaux actifs blanchissants représente un enjeu majeur pour l’industrie cosmétique. De plus en plus de consommateurs s’orientent vers des produits eco-responsables, il devient urgent de développer de nouvelles méthodes de biocatalyse pour accéder à des antipigmentants. Certains glycosides, comme l’arbutine présentent des propriétés blanchissantes qui restent toutefois limitées face à l’hydrolyse rapide de la liaison O-glycosidique. L’enjeu du projet consiste à synthétiser des analogues de cette molécule en série thioglycosidique. En effet, cette liaison permet une plus grande stabilité vis à vis de l’hydrolyse. La mutation d’une glycosidase native issue de dictyoglomus thermophilum a permis d’accéder à une thioglycoligase. Cette dernière permet d’obtenir par catalyse enzymatique des analogues de l’arbutine. Six composés en série S- et O-glycosidique ont pu être synthétisés et testés en tant qu’agents dépigmentants. La méthodologie de synthèse a ensuite été appliquée pour l’obtention de thioglycolipides. Ces molécules sont connues pour leurs propriétés hydrogélifiantes permettant d’accéder à des matériaux thermoreversibles. Cinq molécules ont été identifiées en tant qu’agents hydrogélifiants. Les propriétés rhéologiques, thermiques et structurales ont été caractérisées mettant en évidence des différences significatives parmi les composés. Enfin les résultats préliminaires sur la formulation d’un produit à la fois antipigmentant et texturant s’avèrent prometteurs pour la validation d’un concept de matériau intelligent pour l’industrie cosmétique. / Considering the increasing appearance of pigmentation disorders caused by UV exposure, the development of new whitening agents is a major challenge for the cosmetics industry. Consumers are turning to ecoresponsible products, it is urgent to develop new methods of biocatalysis for the access to new depigmenting agents. Some glycosides, such as arbutin, have whitening properties which are still limited because of therapid hydrolysis of the O-glycosidic bond. The challenge of this project is synthesize analogues of this molecule in thioglycoside series. Endeed, this bond allows a greater stability against the hydrolysis. The mutation of anative glycosidase to dictyoglomus thermophilum gives access to a thioglycoligase. This makes possible the enzymatic synthesis of arbutine analogues. Six molécules were synthesized and tested as depigmenting agents. The synthesis methodology was then applied to the preparation of thioglycolipids. These moleculesare known for their hydrogellating properties allowing access to thermoreversible materials. Five molecules have been identified as hydrogellating agents. The rheological, thermal and structural properties have been characterized and showed significant differences depending of the compound structure. Lastly, the preliminary results on the formulation of a product that is both antipigmenting and texturizing are promising for the validation of an smart material concept for the cosmetic industry.
8

Optimal Electromyogram Modeling and Processing During Active Contractions and Rest

Wang, Haopeng 19 April 2019 (has links)
The standard deviation of surface EMG (EMGσ) is often related to muscle force; the accuracy of EMGσ estimation is valuable for many application areas such as clinical biomechanics, prostheses control and sports medicine. Numerous researchers have developed methods to optimize EMGσ estimation. Whitening the EMG signal has been proved to improve the statistical efficiency of EMGσ estimation, but conventional linear whitening filters fail at low contraction level. An adaptive whitening filter was proposed by Clancy and Farry[14]. This technique has a better performance than prior whitening methods, however, the adaptive whitening filter needs to be calibrated each time electrodes are applied, which increase the complexity of the implementation. We designed a universal whitening filter which can omit most calibration steps for the adaptive whitening filter in future use. We used the ensemble mean of the power spectrum of 512 EMG recordings to form a general shape of a fixed whitening filter that can applied on any EMG signal. The test error on an EMG-torque task based on universal whitening over 512 subjects had a mean error of 4.80% maximum voluntary contraction (MVC) and standard deviation (std) of 2.03% MVC, compared with an original adaptive whitening filter error of 4.84±1.98% MVC. Additionally, the rest contraction modeling hasn’t received enough attention. Existing RMS estimates of EMGσ subtract noise in either the amplitude or power domain. These procedures have never been modeled analytically. We show that power domain noise subtraction is optimal. But rest contractions which are processed using power domain noise subtraction only estimate a zero-valued EMGσ approximately 50% of the time, which is undesirable in prosthesis-control. The prosthesis has a 50% possibility to slowly drift based on the current RMS estimator. We propose a new estimator to improve the zero-amplitude estimation probability during rest. We used 512 rest contraction recordings to validate the probability distribution of rest EMG signal showing that it only has 1.6% difference compared with Gaussian distribution. We also evaluated the percent of zero-valued EMGσ estimates using power domain noise subtraction and our new estimator, matching experimental findings to the theoretic predictions.
9

Estudo clínico randomizado, duplo-cego da percepção da cor e satisfação e sensibilidade em pacientes submetidos a clareamento dental / Double-blind, randomized, clinical trial of color perception and satisfaction in patients undergoing dental bleaching

Nishida, Alexander Cassandri 20 September 2016 (has links)
O clareamento dentário é a maneira mais conservadora e barata de melhorar a satisfação dos pacientes com o seu sorriso. Entretanto existem poucos estudos que correlacionam a eficácia clareadora com a satisfação dos pacientes e a maneira como eles percebem a mudança das cores. OBJETIVO: Investigar a relação entre mudança de cor e satisfação e a percepção da mudança de cor pelos pacientes e operador treinado comparado a um método instrumental. MATERIAIS E MÉTODOS: Uma pesquisa clínica randomizada duplo-cega foi conduzida com 100 pacientes que atendiam os critérios de inclusão e exclusão. Eles foram divididos em 5 grupos randomizados: Peróxido de hidrogênio 4%, peróxido de carbamida 15%, peróxido de carbamida 16%, Peróxido de carbamida 16% experimental e placebo. Foi tomada a cor base dos dentes através de tomadas objetivas com Vita Easyshade e subjetivas com a escala Vita BleachGuide 3D. Eles foram submetidos à terapia clareadora recebendo uma seringa de gel clareador por semana durante 3 semanas e preencheram avaliação sobre sua sensibilidade e avaliações sobre satisfação e percepção de mudança de cor. Foi um total de 11 visitas por paciente: entrevista inicial e triagem, moldagem e profilaxia, tomada de cor e entrega de clareador, controles de 7, 14, 21, 30, 60, 90, 120 e 180 dias. Nos retornos todas as etapas de tomada e controle de cor pelo paciente e pelo mesmo operador treinado, objetiva e subjetiva foram repetidas. RESULTADOS maiores valores de ?E* na sem 1, ANOVA mostrou que eles foram diferentes entre si (P=0.001), valor que não se repete a partir da segunda semana na análise entre os grupo (P=0.275). Maiores ?E* foram os géis à base de peróxido de carbamida (PC15, PC16 e PC16EX). ?E* Final foi maior no grupo PC15, PC16 e PC16EX e esses 3 grupos foram estatísticamente semelhantes. Os menores valores foram para o grupo placebo que não foi semelhante a nenhum outro grupo e nem entre os tempos. A análise de variância entre os 5 grupos mostrou diferenças para percepção cega (p=0.001), percepção orientada (p=0.001), e expectativa (p=0.603. Fica claro que a satisfação do paciente é crescente em todos os grupos da primeira a terceira semana de terapia. A ordem de satisfação dos pacientes foi PC15, PC16EX, PC16, PH4 e PLAC. No último período representado, terceira semana ao fim do acompanhamento de 6 meses, verificamos que a satisfação diminui no período pós-terapia, principalmente para o grupo PLAC e para o grupo PC16EX. Mesmo o grupo PLAC (que representa o placebo) também teve satisfação crescente. No arco inferior os maiores resultados para sensibilidade ficaram também com PH4, PC15 e PC16..CONCLUSÕES: Os clareadores baseados em peróxido de carbamida tiverem as maiores variações de cor, sendo os mais efetivos. Em comparação ao paciente, o operador treinado tem uma capacidade de avaliação de cor mais próxima dos valores aferidos instrumentalmente. A satisfação do paciente aumenta com todos os grupos, inclusive o placebo, porém declina no período pós terapia. Os pacientes tendem a enxergar os dentes mais escuros do que realmente são e criam expectativas por cores mais claras. Todos os grupos causaram sensibilidade, inclusive o placebo, semelhantes para maxila e mandíbula. / Tooth whitening is the most conservative and inexpensive way to improve patient satisfaction with your smile. However there are few studies that correlate the whitening efficacy with patient satisfaction and how they perceive the change of colors. To investigate the relationship between color change and satisfaction and perception of color change by patients and trained operator compared to an instrumental method. MATERIALS AND METHODS: A double-blind randomized clinical trial was conducted with 100 patients who met the inclusion and exclusion criteria. They were divided into five randomized groups: Hydrogen peroxide 4%, 15% carbamide peroxide, 16% carbamide peroxide, 16% carbamide experimental and placebo. It was made the base color of the teeth through objective taken with Vita Easyshade and subjective with the Vita BleachGuide 3D scale. They underwent therapy Clarifying getting a whitening gel syringe per week for 3 weeks and completed evaluation of its sensitivity and reviews of satisfaction and perception of color change. There were a total of 11 visits per patient: initial interview and sorting, forming and prophylaxis, making color and delivery bleaching 7 controls 14, 21, 30, 60, 90, 120 and 180 days. In returns all steps taken and color control by the patient and by the same trained operator, objective and subjective were repeated. RESULTS larger ?E * values in no 1, ANOVA showed that they were different (P = 0.001), a figure that is not repeated from the second week on the analysis of the group (P = 0.275). Larger ?E * the gels were carbamide peroxide-based (PC15, PC16 and PC16EX). ?E * Final was higher in the group PC15, PC16 and PC16EX and these 3 groups were statistically similar. The lowest values were for the placebo group was not similar to any other group or between the times. Analysis of variance among the five groups showed differences to blind perception (p = 0.001), oriented perception (p = 0.001) and expectation (p = 0.603. It is clear that patient satisfaction is increasing in all of the first groups third week of therapy. the order of patient satisfaction was PC15, PC16EX, PC16, PH4 and PLAC. in the latter represented period, the third week after the 6-month follow-up, we found that satisfaction decreases in the post therapy period, mainly for PLAC group and the group PC16EX Even the PLAC group (representing placebo) also had increasing satisfaction in the lower arch greater results for sensitivity were also PH4, PC15 and PC16..CONCLUSÕES: carbamide peroxide have the greater color variations, the most effective being. compared to the patient, the trained operator has a capacity assessment of the closest color of the measured values instrumentally. patient satisfaction increases with all the groups, including the placebo, but declines in the period post therapy. Patients tend to see the darker teeth than they really are and create expectations for lighter colors. All groups sensitivity caused, including placebo, similar to maxilla and mandible.
10

Avaliação clínica da efetividade de géis clareadores de baixa concentração no clareamento em consultório de dentes polpados, com e sem o emprego de fonte de luz híbrida e condicionamento ácido prévio do esmalte

Martha Beteghelli Michielin 08 May 2015 (has links)
O objetivo deste estudo clínico randomizado duplo cego boca-dividida foi avaliar, in vivo, a efetividade do condicionamento ácido prévio do esmalte e de géis clareadores a base de peróxido de hidrogênio (PH) de baixa concentração, associados a fontes de luz híbrida (LH), tendo como variáveis de reposta: sensibilidade dental, fluxo sanguíneo pulpar, grau de mudança e estabilidade de cor ao longo de 6 meses. Trinta e seis voluntários que se encaixaram nos critérios de inclusão e exclusão foram selecionados e randomizados em 3 grupos (n=12), de acordo com o protocolo clareador a ser utilizado. Dentro de cada grupo, um dos hemiarcos foi aleatoriamente selecionado para a realização do condicionamento ácido do esmalte, previamente a aplicação do gel clareador. Os géis que compunham os três protocolos clareadores foram: PH a 10% (experimental) associado a LH a base de LED violeta + laser de diodo (experimental); PH a 15% associado a LH a base de LED azul + laser de diodo; e PH a 35% sem ativação com fonte de luz. A sensibilidade foi avaliada com a escala VAS; a fluxometria pulpar, com o sistema Laser Doppler; e a cor pelo cálculo do ?E via espectrofotômetro. Os dados foram tratados pela análise de variância de medidas repetidas (ANOVA), Tukey e teste de Friedman (p<0,05). Com relação à sensibilidade, foram encontradas diferenças significativas na interação tempo e grupo, mas não com relação ao ácido. Quanto à vascularização pulpar, o efeito de grupo não foi rejeitado, sendo o grupo de PH a 35% o que apresentou as menores medianas para as variações percentuais, porém os efeitos de ácido e tempo não foram significativos. Quanto à cor, diferenças significantes foram encontradas entre os grupos, mas não com relação ao uso do ácido, sendo o PH a 35% o que promoveu maior aumento do ?E. Conclui-se assim que o condicionamento ácido não foi capaz de favorecer a efetividade do clareamento em função do grau de mudança e estabilidade de cor, bem como não aumentou a sensibilidade e o fluxo sanguíneo da polpa dental. A concentração dos agentes clareadores foi determinante para o grau de mudança de cor e demonstrou influenciar a sensibilidade e o fluxo sanguíneo pulpar. / The aim of this double blind split-mouth randomized clinical study was to evaluate, in vivo, the effectiveness of prior acid etching on enamel and low concentration bleaching gels based on hydrogen peroxide (HP) associated with hybrid light (HL) sources, having as response variables: dental sensitivity, dental pulp vascularization and degree of color change and stability over 6 months. Thirty-six volunteers in agreement with the inclusion and exclusion criteria were selected and randomly divided into 3 groups (n = 12) according to the bleaching protocol to be used. Within each group, one of the sides was randomly selected for the execution of acid etching prior to the gel application. The three bleaching gels were: 10% HP (experimental) associated with HL-based violet LED/laser (experimental); 15% HP associated with HL-based blue LED/laser; and 35% HP without light activation. Sensitivity was evaluated with the VAS scale; pulp flowmetry by the use of the Laser Doppler system; and efficacy was evaluated by calculating the ?E via a spectrophotometer. Data were analyzed by analysis of variance for repeated measures (ANOVA), Tukeys and Friedman tests (p<0.05). Regarding sensitivity, significant differences were found in the interaction between the application time and group but not regarding etching. For dental pulp flowmetry, the group effect was not rejected, where the 35% HP showed the lowest medians for the percentile variations, but the effects of etching and time were not significant. For color, significant differences were found between the groups, but not between the sides with and without acid etching, where the 35% HP gel promoted the highest increase in ?E. It is therefore concluded that the etching was not able to favor the effectiveness of whitening due to color variation and stability, as well as not increasing sensitivity or pulp blood flow. The concentration of bleaching agents determined the degree of color change and influenced the sensitivity and blood flow of the dental pulp.

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