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Micro-hardness evaluation of a micro-hybrid composite resin light cured with halogen light, light-emitting diode and argon ion laser

RODE, Katia M.; FREITAS, Patricia M. de; LLORET, Patricia R.; POWELL, Lynn G.; TURBINO, Miriam L.
Fonte: SPRINGER LONDON LTD Publicador: SPRINGER LONDON LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.66%
This in vitro study aimed to determine whether the micro-hardness of a composite resin is modified by the light units or by the thickness of the increment. Composite resin disks were divided into 15 groups (n = 5), according to the factors under study: composite resin thickness (0 mm, 1 mm, 2 mm , 3 mm and 4 mm) and light units. The light activation was performed with halogen light (HL) (40 s, 500 mW/cm(2)), argon ion laser (AL) (30 s, 600 mW/cm(2)) or light-emitting diode (LED) (30 s, 400 mW/cm(2)). Vickers micro-hardness tests were performed after 1 week and were carried out on the top surface (0 mm-control) and at different depths of the samples. Analysis of variance (ANOVA) and Tukey tests (P a parts per thousand currency signaEuro parts per thousand 0.05) revealed no statistically significant difference among the light units for the groups of 0 mm and 1 mm thickness. At 2 mm depth, the AL was not statistically different from the HL, but the latter showed higher micro-hardness values than the LED. In groups with 3 mm and 4 mm thickness, the HL also showed higher micro-hardness values than the groups activated by the AL and the LED. Only the HL presented satisfactory polymerization with 3 mm of thickness. With a 4 mm increment no light unit was able to promote satisfactory polymerization.; Sao Paulo Research Foundation/FAPESP[99/08433-4]; Sao Paulo Research Foundation/FAPESP[99/11408-1]

Effects of curing protocol and storage time on the micro-hardness of resin cements used to lute fiber-reinforced resin posts

Ramos, Marcelo Barbosa; Pegoraro, Thiago Amadei; Pegoraro, Luiz Fernando; Carvalho, Ricardo Marins
Fonte: UNIV SAO PAULO FAC ODONTOLOGIA BAURU; BAURU-SP Publicador: UNIV SAO PAULO FAC ODONTOLOGIA BAURU; BAURU-SP
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.59%
Objectives: To determine the micro-hardness profile of two dual cure resin cements (RelyX - U100 (R), 3M-ESPE and Panavia F 2.0 (R), Kuraray) used for cementing fiber-reinforced resin posts (Fibrekor (R) - Jeneric Pentron) under three different curing protocols and two water storage times. Material and methods: Sixty 16mm long bovine incisor roots were endodontically treated and prepared for cementation of the Fibrekor posts. The cements were mixed as instructed, dispensed in the canal, the posts were seated and the curing performed as follows: a) no light activation; b) light-activation immediately after seating the post, and; c) light-activation delayed 5 minutes after seating the post. The teeth were stored in water and retrieved for analysis after 7 days and 3 months. The roots were longitudinally sectioned and the microhardness was determined at the cervical, middle and apical regions along the cement line. The data was analyzed by the three-way ANOVA test (curing mode, storage time and thirds) for each cement. The Tukey test was used for the post-hoc analysis. Results: Light-activation resulted in a significant increase in the microhardness. This was more evident for the cervical region and for the Panavia cement. Storage in water for 3 months caused a reduction of the micro-hardness for both cements. The U100 cement showed less variation in the micro-hardness regardless of the curing protocol and storage time. Conclusions: The micro-hardness of the cements was affected by the curing and storage variables and were material-dependent.; FAPESP [07/02612-2]; CNPq [307510/2010-7]; CAPES (Brazil)

Influência das unidades fotoativadoras e do material restaurador indireto sobre a dureza de um cimento resinoso dual auto-adesivo e um cimento resinoso dual convencional por meio de teste de nanoendentação; Influence of curing units and restorative indirect material on hardness of a dual cure self-adhesive resin cement and dual cure conventional resin cement through nanoindentadion test

Kuguimiya, Rosiane Nogueira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/12/2013 PT
Relevância na Pesquisa
46.51%
O objetivo deste estudo foi avaliar a dureza de um cimento resinoso dual autoadesivo (RelyX U200) e um cimento resinoso dual convencional (RelyX ARC) fotoativados sob materiais restauradores indiretos, utilizando unidades fotoativadoras com diferentes comprimentos de ondas (LED Elipar Freelight 2, LED Bluephase, Laser AccuCure 3000TM), por meio de teste de nanoendentação. Para a obtenção dos espécimes foram utilizados incisivos bovinos que após profilaxia, foram submetidos a cortes no limite amelo-cementário para a separação da porção coronária. Após inclusão, os espécimes foram submetidos ao desgaste para exposição de dentina e padronização do substrato. Para simular clinicamente restaurações indiretas foram confeccionadas peças em cerâmica IPS e.max® Press (Ivoclar Vivadent) e em resina composta indireta SR Adoro (Ivoclar Vivadent) que foram cimentadas nas superfícies dentinárias. Os espécimes foram seccionados longitudinalmente em baixa velocidade e constante irrigação e polidos em politriz. Foi estabelecido um grupo controle positivo, no qual o cimento foi fotoativado sem a interposição de material restaurador indireto e um grupo controle negativo, no qual, após a cimentação do material restaurador indireto...

Hardness evaluation, stoichiometry and grain size of titanium nitride obtained with plasma nitriding on Ti-6AI-4V samples

Vasconcellos, Marcos Antonio Zen; Lima, Saulo Cordeiro; Hinrichs, Ruth
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
46.44%
Titanium nitride films were formed on the surface of Ti-6Al-4V discs by plasma nitriding (glow discharge) in different N2:H2 atmospheres at several substrate temperatures. In this study the influence of the process parameters on dynamic micro-hardness were investigated. Grain sizes of the nitride films, determined with X-Ray Diffraction, were related to the nitriding parameters. TiNx stoichiometry was determined with Nuclear Reaction Analysis and showed a correlation to substrate temperature during the nitriding process. Micro-hardness measurements were taken on the nitrided surfaces. Grain sizes increased for a particular gas composition of 60%N2+40%H2 where hardness was lowest.

Efeito dos elementos estranhos (foreign íons) sobre a microdureza Vickers das fases cristalinas em clínqueres co-processados

Souza, Vládia Cristina Gonçalves de; Koppe, Jair Carlos; Costa, Joao Felipe Coimbra Leite
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
POR
Relevância na Pesquisa
46.52%
Esse trabalho determina o valor médio de microdureza Vickers dos componentes cristalinos do clínquer e estima o efeito dos elementos estranhos (menores) e da composição mineralógica sobre os resultados de microdureza. Para isto, foi coletado um número signifi cativo de amostras sobre a correia de alimentação de moinhos de clínqueres em onze fornos co-processadores no Brasil. Os resultados mostram que a microdureza varia de acordo com o tipo de impurezas e sua distribuição. Também, o conteúdo mineralógico e a razão alumina/ferro desempenham um papel importante.; This study determines the average value of Vickers micro-hardness of the clinker crystalline compounds and evaluates the effect of foreign ions and mineralogical composition on the micro-hardness results. A signifi cant number of samples were collected from the feed-conveyor belt of the clinker ball mill at eleven co-processing kilns in Brazil. The results show that the micro-hardness varies according to the type of impurities and their distribution. Also, the mineralogical content and alumina/iron ratio play an important role.

Soldagem em laminas finas de hastelloy c-276 por laser pulsado Nd:YAG

Munekata, Ricardo Mitsuo
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 103 f. : il.
POR
Relevância na Pesquisa
46.23%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Engenharia Mecânica - FEIS; O presente trabalho estudou a influência da energia do pulso de soldagem, no caso processo laser de Nd:YAG operando no modo pulsado, na soldagem de duas lâminas finas com 100 μm de Hastelloy C-276, utilizado no revestimento de sensores que trabalham em ambiente corrosivo da indústria sucroalcooleira, química petroquímica e alimentícia. Utilizou-se energia de pulso de 1,0 Joule a 2,25 Joules, com incremento de 0,25 Joules com a velocidade de soldagem de (ν) taxa de repetição (Rr) fixas de 525mm/min e 39Hz respectivamente e largura temporal de 4 ms. As soldas foram realizadas com proteção gasosa de argônio. Foram realizadas análises macrográficas e micrográficas das juntas soldadas, através de secções transversais das mesmas e ensaios de microdureza Vickers e ensaio de tração. Os resultados obtidos mostraram que o controle da energia do pulso, em processo de soldagem por laser de lâminas finas é de fundamental importância para a geração de juntas soldadas livres de descontinuidades. Os parâmetros geométricos da junta soldada, tais como largura do cordão, largura de união e profundidade do cordão...

Augmentation of wear-protective coatings for non-ferrous alloys by the addition of Cr and Ni elements

Antipas,Georgios S. E.
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 EN
Relevância na Pesquisa
46.47%
A number of Al-, Mg- and Ti-base alloys were preconditioned by oxidation via Plasma-electrolytic oxidation (PEO) followed by the addition of Cr and Ni elements in the coating pores by chemical precipitation and a final stage of mechanical treatment. The overall effect was a combination of hardness and resistance to wear. PEO voltage level was found to be a factor decisive for the oxide layer thickness and level of porosity. In turn the latter two factors appeared to act upon the degree of hardening corundum to alumina fraction in the layer and the degree of Cr/Ni penetration into the oxide layer itself. The optimum condition of increased micro-hardness and high resistance to wear was achieved for an AlCu4Mg2 alloy of extended oxide layer thickness and intermediate levels of open porosity. Similarly good wear results were obtained for a Be60AlMg2 alloy of particularly low micro-hardness but of sufficiently high porosity in order to accommodate the Cr/Ni intake.

Combined Micro-Hardness and Eddy Currents Applied to the Study of Steel Decarburizing

Mercier,D.; Chicot,D.
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 EN
Relevância na Pesquisa
66.51%
Carbon is the most important element going in the steels composition since it largely contributes to their mechanical performance. During the heat treatment of steels, a part of atoms of carbon could be removed from the superficial zone of the steel, which is the result of the atmospheric oxygen attraction by forming gaseous carbon monoxide. This phenomenon, called decarburizing, can change microstructure in a large extent and, as a result, mechanical properties of the steel. This could lead to unsuitable properties for the service life of mechanical parts. In order to prevent such part from breaking in service, it is necessary to know the affected zone by the decarburizing process. For this purpose, the most used technique is a visual observation by optical microscopy of a cross section of the material. This technique is often associated to the hardness profile obtained by Vickers or Knoop indentations in the same section. Depending on the material and on the specimen preparation, some discrepancies are often observed between the two informations. On the other hand, these techniques require a long preparation and cautious interpretation. Then we propose here to use eddy current testing, which is widely employed to detect fatigue cracks...

Hardness evaluation, stoichiometry and grain size of titanium nitride films obtained with plasma nitriding on Ti-6Al-4V samples

Vasconcellos,Marcos Antonio Zen; Lima,Saulo Cordeiro; Hinrichs,Ruth
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
Relevância na Pesquisa
46.44%
Titanium nitride films were formed on the surface of Ti-6Al-4V discs by plasma nitriding (glow discharge) in different N2:H2 atmospheres at several substrate temperatures. In this study the influence of the process parameters on dynamic micro-hardness were investigated. Grain sizes of the nitride films, determined with X-Ray Diffraction, were related to the nitriding parameters. TiNx stoichiometry was determined with Nuclear Reaction Analysis and showed a correlation to substrate temperature during the nitriding process. Micro-hardness measurements were taken on the nitrided surfaces. Grain sizes increased for a particular gas composition of 60%N2+40%H2 where hardness was lowest.

Effects of curing protocol and storage time on the micro-hardness of resin cements used to lute fiber-reinforced resin posts

Ramos,Marcelo Barbosa; Pegoraro,Thiago Amadei; Pegoraro,Luiz Fernando; Carvalho,Ricardo Marins
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2012 EN
Relevância na Pesquisa
46.59%
OBJECTIVES: To determine the micro-hardness profile of two dual cure resin cements (RelyX - U100®, 3M-eSPe and Panavia F 2.0®, Kuraray) used for cementing fiberreinforced resin posts (Fibrekor® - Jeneric Pentron) under three different curing protocols and two water storage times. MATERIAL AND METHODS: Sixty 16mm long bovine incisor roots were endodontically treated and prepared for cementation of the Fibrekor posts. The cements were mixed as instructed, dispensed in the canal, the posts were seated and the curing performed as follows: a) no light activation; b) light-activation immediately after seating the post, and; c) light-activation delayed 5 minutes after seating the post. The teeth were stored in water and retrieved for analysis after 7 days and 3 months. The roots were longitudinally sectioned and the microhardness was determined at the cervical, middle and apical regions along the cement line. The data was analyzed by the three-way ANOVA test (curing mode, storage time and thirds) for each cement. The Tukey test was used for the post-hoc analysis. RESULTS: Light-activation resulted in a significant increase in the microhardness. This was more evident for the cervical region and for the Panavia cement. Storage in water for 3 months caused a reduction of the micro-hardness for both cements. The U100 cement showed less variation in the micro-hardness regardless of the curing protocol and storage time. CONCLUSIONS: The micro-hardness of the cements was affected by the curing and storage variables and were material-dependent.

Plasma Nitriding of 90CrMoV8 Tool Steel for the Enhancement of Hardness and Corrosion Resistance

NOUVEAU, Corinne; STEYER, Philippe; MOHAN RAO, Kumar Ram; LAGADRILLERE, Denis
Fonte: Elsevier Publicador: Elsevier
EN
Relevância na Pesquisa
46.29%
The aim of the study is to apply a plasma nitriding process to the 90CrMoV8 steel commonly employed in wood machining, and to determine its efficiency to improve both mechanical and electrochemical properties of the surface. Treatments were performed at a constant N2:H2 gas mixture and by varying the temperature and process duration. The structural and morphological properties of nitrided layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS microanalyses. Surface hardening and hardness profiles were evaluated by micro hardness measurements. To simulate the woodmachining conditions, electrochemical tests were carried out with an oak wood electrolyte with the purpose of understanding the effects of the nitriding treatment on the corrosion resistance of the tool in operation. X-ray diffraction analyses revealed the presence of both γ′ (Fe4N) and ε (Fe2–3N) nitrides with a predominance of the ε phase. Moreover, α-Fe (110), γ′ and ε diffraction peaks were shifted to lower angles suggesting the development of compressive stresses in the post nitrided steel. As a result, it was shown that nitriding allowed a significant hardening of steel with hardness values higher than 1200 HV. The diffusion layers were always composed of an outer compound layer and a hardened bulk layer which thickness was half of the total diffusion layer one.No white layer was observed. Similarly...

Evaluation of the micro-hardness and fracture toughness of amorphous and partially crystallized 3CaO center dot P2O5-SiO2-MgO bioglasses

Daguano, Juliana K. M. F.; Suzuki, Paulo A.; Strecker, Kurt; Fernandes, Maria H. F. V.; Santos, Claudinei
Fonte: ELSEVIER SCIENCE SA; LAUSANNE Publicador: ELSEVIER SCIENCE SA; LAUSANNE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.58%
In this work, the effect of the indentation load on the results of hardness and fracture toughness, determined by Vickers micro-hardness measurements, of some glasses and glass-ceramics has been investigated. Furthermore, in order to verify the effect of crystallinity on the results, glasses of composition 52.75 wt.% 3CaO center dot P2O5, 30 wt.% SiO2 and 17.25 wt.% MgO were fused at 1600 degrees C for 4 h and annealed at 700 degrees C for 2h, and further heat-treated at 700, 775, 800 and 900 degrees C for 4h. The obtained materials were analyzed by high resolution X-ray diffraction, HRXRD, to determine the crystallization degree in function of the heat-treatment temperature. The hardness of the different specimens was determined by Vickers' micro-hardness measurements under various loads. It has been observed that with increasing crystallization of the materials their hardness increased. Furthermore, it has been possible to verify the so-called indentation size effect (ISE), i.e. hardness decreases as the indentation depth, under higher loads, increases. This effect has been more pronounced in the glass-ceramic samples. Fracture toughness has been determined by the crack length induced by the Vickers indentations and relating them to the applied loads. Glass materials presented a fracture pattern with characteristics of cleavage...

Effect of a multi-layer infection control barrier on the micro-hardness of a composite resin

Hwang,In-Nam; Hong,Sung-Ok; Lee,Bin-Na; Hwang,Yun-Chan; Oh,Won-Mann; Chang,Hoon-Sang
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2012 EN
Relevância na Pesquisa
56.71%
OBJECTIVE: The aim of this study was to evaluate the effect of multiple layers of an infection control barrier on the micro-hardness of a composite resin. MATERIAL AND METHODS: One, two, four, and eight layers of an infection control barrier were used to cover the light guides of a high-power light emitting diode (LeD) light curing unit (LCU) and a low-power halogen LCU. The composite specimens were photopolymerized with the LCUs and the barriers, and the micro-hardness of the upper and lower surfaces was measured (n=10). The hardness ratio was calculated by dividing the bottom surface hardness of the experimental groups by the irradiated surface hardness of the control groups. The data was analyzed by two-way ANOVA and Tukey's HSD test. RESULTS: The micro-hardness of the composite specimens photopolymerized with the LED LCU decreased significantly in the four- and eight-layer groups of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. The hardness ratio of the composite specimens was <80% in the eight-layer group. The micro-hardness of the composite specimens photopolymerized with the halogen LCU decreased significantly in the eight-layer group of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. However...

Effect of veneering materials and curing methods on resin cement knoop hardness

Tango,Rubens Nisie; Sinhoreti,Mário Alexandre Coelho; Correr,Américo Bortolazzo; Correr-Sobrinho,Lourenço; Consani,Rafael Leonardo Xediek
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 EN
Relevância na Pesquisa
46.37%
This study evaluated the Knoop hardness of Enforce resin cement activated by the either chemical/physical or physical mode, and light cured directly and through ceramic (HeraCeram) or composite resin (Artglass). Light curing were performed with either conventional halogen light (QTH; XL2500) for 40 s or xenon plasma arc (PAC; Apollo 95E) for 3 s. Bovine incisors had their buccal surfaces flattened and hybridized. On these surfaces a mold was seated and filled with cement. A 1.5-mm-thick disc of the veneering material was seated over this set for light curing. After storage (24 h/37ºC), specimens (n=10) were sectioned for hardness (KHN) measurements in a micro-hardness tester (50 gf load/ 15 s). Data were submitted to ANOVA and Tukey's test (alpha=0.05). It was observed that the dual cure mode yielded higher hardness compared to the physical mode alone, except for direct light curing with the QTH unit and through Artglass. Higher hardness was observed with QTH compared to PAC, except for Artglass/dual groups, in which similar hardness means were obtained. Low KHN means were obtained with PAC for both Artglass and HeraCeram. It may be concluded that the hardness of resin cements may be influenced by the presence of an indirect restorative material and the type of light-curing unit.

Effects of curing protocol and storage time on the micro-hardness of resin cements used to lute fiber-reinforced resin posts

Ramos, Marcelo Barbosa; Pegoraro, Thiago Amadei; Pegoraro, Luiz Fernando; Carvalho, Ricardo Marins
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/10/2012 ENG
Relevância na Pesquisa
46.59%
OBJECTIVES: To determine the micro-hardness profile of two dual cure resin cements (RelyX - U100®, 3M-eSPe and Panavia F 2.0®, Kuraray) used for cementing fiberreinforced resin posts (Fibrekor® - Jeneric Pentron) under three different curing protocols and two water storage times. MATERIAL AND METHODS: Sixty 16mm long bovine incisor roots were endodontically treated and prepared for cementation of the Fibrekor posts. The cements were mixed as instructed, dispensed in the canal, the posts were seated and the curing performed as follows: a) no light activation; b) light-activation immediately after seating the post, and; c) light-activation delayed 5 minutes after seating the post. The teeth were stored in water and retrieved for analysis after 7 days and 3 months. The roots were longitudinally sectioned and the microhardness was determined at the cervical, middle and apical regions along the cement line. The data was analyzed by the three-way ANOVA test (curing mode, storage time and thirds) for each cement. The Tukey test was used for the post-hoc analysis. RESULTS: Light-activation resulted in a significant increase in the microhardness. This was more evident for the cervical region and for the Panavia cement. Storage in water for 3 months caused a reduction of the micro-hardness for both cements. The U100 cement showed less variation in the micro-hardness regardless of the curing protocol and storage time. CONCLUSIONS: The micro-hardness of the cements was affected by the curing and storage variables and were material-dependent.

Effect of a multi-layer infection control barrier on the micro-hardness of a composite resin

Hwang, In-Nam; Hong, Sung-Ok; Lee, Bin-Na; Hwang, Yun-Chan; Oh, Won-Mann; Chang, Hoon-Sang
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/10/2012 ENG
Relevância na Pesquisa
56.64%
OBJECTIVE: The aim of this study was to evaluate the effect of multiple layers of an infection control barrier on the micro-hardness of a composite resin. MATERIAL AND METHODS: One, two, four, and eight layers of an infection control barrier were used to cover the light guides of a high-power light emitting diode (LeD) light curing unit (LCU) and a low-power halogen LCU. The composite specimens were photopolymerized with the LCUs and the barriers, and the micro-hardness of the upper and lower surfaces was measured (n=10). The hardness ratio was calculated by dividing the bottom surface hardness of the experimental groups by the irradiated surface hardness of the control groups. The data was analyzed by two-way ANOVA and Tukey's HSD test. RESULTS: The micro-hardness of the composite specimens photopolymerized with the LED LCU decreased significantly in the four- and eight-layer groups of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. The hardness ratio of the composite specimens was

Spectroscopic and Mechanical Studies on the Fe-based Amorphous Alloy 2605SA1

Cabral-Prieto,Agustín; Contreras-Vite,Juan Antonio; García-Sosa,Irma; Nava,Noel; García-Santibáñez,Federico
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2010 EN
Relevância na Pesquisa
46.49%
The Vickers micro-hardness of this alloy was unusually dependent on the heat treatment from 300 to 634K, inferring important micro-structural changes and the presence of amorphous grains before its phase transition. Once the alloy is crystallized, the micro-hardness is characteristic of a brittle alloy, the main problem of these alloys. Within the amorphous state, other properties like free-volume, magnetic states and Fe-Fe distances were followed by PALS and MS, respectively, to analyze those micro-structural changes, thermally induced, which are of paramount interest to understand their brittleness problem.

The effect of three whitening oral rinses on enamel micro-hardness

Potgieter,E; Osman,Y; Grobler,SR
Fonte: SciELO África do Sul Publicador: SciELO África do Sul
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em // EN
Relevância na Pesquisa
66.64%
The purpose of this study was to determine the effect on human enamel micro-hardness of three over-the-counter whitening oral rinses available in South Africa. Enamel fragments were gathered into three groups of 15 each. One group was exposed to Colgate Plax Whitening Blancheur, the second group to White Glo 2 in 1 and the third to Plus White, in each case for periods recommended by the respective manufacturers. Surface micro-hardness of all groups was measured before and after a 14 day treatment period. pH levels of the oral rinses were also determined with a combination pH electrode. Pre- and post- treatment data were analysed by the Wilcoxon Signed Rank Sum Test. According to the micro-hardness values no significant (p>0.05) enamel damage was found as a result of treatment. However, it was observed that Colgate Plax and White Glo decreased the enamel hardness, an early sign of enamel damage, while Plus White showed a small increase in hardness. The three whitening oral rinses on the South African market do not damage the tooth enamel significantly when used as recommended by the manufacturers. However, extending the contact period and increasing the frequency of application might lead to damage of enamel.

Microhardness and morphological changes induced by Nd: Yag laser on dental enamel: an in vitro study

Bedini,Rossella; Manzon,Licia; Fratto,Giovanni; Pecci,Raffaella
Fonte: Istituto Superiore di Sanità Publicador: Istituto Superiore di Sanità
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 EN
Relevância na Pesquisa
46.33%
The aim of this work was a scanning electron microscopy (SEM) evaluation of the hardness and morphological changes of enamel irradiated by neodymium: yttrium aluminium garnet (Nd:YAG) laser with different energy levels. Twenty-eight human teeth samples were divided into 4 groups: control, where enamel surface was not lased, and 3 test treated with 3 different levels of energy power 0.6, 1.2 and 2.4 Watt, respectively. In each group, 5 samples underwent Vickers microhardness test and 2 samples were processed for SEM. No significant differences between treated and non treated samples were found by micro-hardness test. However, by SEM, test samples showed a rougher enamel surface than control. Specifically, the 0.6 Watt treated samples showed vertical scratches and glass-like areas, while in the other 2 groups enamel surface was covered by craters and cracks. These findings suggest that enamel should be lased at a low energy level to preserve its integrity and reduce demineralization, and thus for dental caries prevention purposes; while high energy level creates a retentive surface suitable for sealant or composite anchorage.

; Determination of root dentin and cementum micro hardness

Cirano, Fabiano Ribeiro; Romito, Giuseppe Alexandre; Todescan, José Hildebrando
Fonte: UNICAMP/FOP Publicador: UNICAMP/FOP
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ;
Publicado em 13/11/2015 ENG
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66.64%
; Vickers micro hardness was assessed on root dentin and cementum in 30 canines obtained from the Periodontics Discipline tooth bank. Crown and cervical portion of the root were discarded by a transverse section situated 3mm, apically, from the cemento-enamel junction on the buccal surface, thus obtaining the root specimen. On root dentin, mean micro hardness values were obtained for 3 regions: (DR1) from 0.05 to 0.1 mm of the cemento dentin junction – 30.64 VHN; (DR2) from 0.3 to 0.5 mm of the cemento dentin junction – 56.92 VHN and (DR3) from 0.8 to 1.0 mm of the cemento dentin junction – 32.70 VHN. After statistical analysis (Variance Analysis test, p < 0,05), we conclude that micro hardness at the DR2 region was statistically greater than that at the DR3 region which was, in turn, greater than that at the DR1 region. The mean micro hardness of cementum was 19.70 VHN.