Fractographic principles applied to Y-TZP mechanical behavior analysis.

The purpose of this study was to evaluate the use of fractography principles to determine the fracture toughness of Y-TZP dental ceramic in which KIc was measured fractographically using controlled-flaw beam bending techniques and to correlate the flaw distribution with the mechanical properties. The Y-TZP blocks studied were: Zirconia Zirklein (ZZ); Zirconcad (ZCA); IPS e.max ZirCad (ZMAX); and In Ceram YZ (ZYZ). Samples were prepared (16mm×4mm×2mm) according to ISO 6872 specifications and subjected to three-point bending at a crosshead speed of 0.5mm/min. Weibull probability curves (95% confidence bounds) were calculated and a contour plot with the Weibull modulus (m) versus characteristic strength (σ0) was used to examine the differences among groups. The fractured surface of each specimen was inspected in a scanning electron microscope (SEM) for qualitative and quantitative fractographic analysis. The critical defect size (c) and fracture toughness (KIc) were estimated. The fractured surfaces of the samples from all groups showed similar fractographic characteristics, except ZCA showed pores and defects. Fracture toughness and the flexural strength values were not different among the groups except for ZCA. The characteristic strength (p<0.05) of ZZ (η=920.4) was higher than the ZCA (η=651.1) and similar to the ZMAX (η=983.6) and ZYZ (η=1054.8). By means of quantitative and qualitative fractographic analysis, this study showed fracture toughness and strength that could be correlated to the observable microstructural features of the evaluated zirconia polycrystalline ceramics.

Application of Micro-Raman Spectroscopy to the Study of Yttria-Stabilized Tetragonal Zirconia Polycrystal (Y-TZP) Phase Transformation.

The aim of this study was to perform micro-Raman spectroscopy as an alternative and nondestructive method to identify the phase transformation of zirconia after mechanical stress. The groups evaluated were experimental zirconia, zirconcad, IPS e.max ZirCad, and In Ceram YZ. Ten specimens were constructed for each group (n = 30) and subjected to a three-point bending test with a crosshead speed of 0.5 mm/min. The fractured surfaces were analyzed by micro-Raman spectroscopy. The laser power was kept at 10 mW, and scanning was performed in three regions of the fractured surface: (i) near the source of the failure (region of tensile stress), (ii) central to the fractured surface, and (iii) far from the source of failure. All materials showed the characteristic bands of tetragonal and monoclinic phases of zirconia. All zirconia studied showed a monoclinic phase in the tensile stress region. Micro-Raman spectroscopy was effective in detecting the presence of crystalline phases in polycrystals ceramics.

Orthodontic treatment finishing with minimally invasive resin composite veneers / Finalização de tratamento ortodôntico facetas de resina composta minimamente invasivas

Anatomic alterations caused by incisal guide wear, even when small, can cause the aspect of an aged smile. The objective of this clinical case is to reporta highly conservative esthetic treatment performed through the association of in-office bleaching andresin composite veneers. In-office bleaching was performed with 35% hydrogen peroxide, and in the following week, minimal invasive resin composite veneers were installed on the upper incisors and canines. In the next appointment, finishing and polishing were performed with abrasive discs and silicon carbide brushes. The results were considered highly satisfactory, establishing a younger aspectof the patient’s smile. Resin composite veneers are still an excellent alternative for esthetic reanatomizationof anterior teeth, capable of generating optimal results with low costs and time...

Alterações anatômicas causadas pelo desgaste da guia incisal, mesmo quando pequeno, podem causar um aspecto de um sorriso envelhecido. O objetivo deste caso clínico é reportar uma tratamento estético altamente conservativo realizado por meio da associação de clareamento em consultório e facetas de resina composta. O clareamento em consultório foi realizado com peróxido de hidrogênio a 35%,e na semana seguinte, facetas de resina composta minimamente invasivas foram instaladas nos incisivos e caninos superiores. Na próxima consulta, acabamento e polimento foram realizados com discos abrasivos e escova de carbeto de silício. Os resultados foram considerados altamente satisfatórios, estabelecendo um aspecto jovial ao sorriso da paciente. Facetas de resinas compostas são ainda uma excelente alternativa para reanatomização estética dos dentes anteriores, capazes de gerar resultados ótimos com baixo custo e tempo...

Bond strength and Raman analysis of the zirconia-feldspathic porcelain interface.

STATEMENT OF PROBLEM: Zirconia has the best mechanical properties of the available ceramic systems. However, the stability of the zirconia-feldspathic porcelain interface may be jeopardized by the presence of the chipping and debonding of the feldspathic porcelain. PURPOSE: The purpose of this study is to evaluate the shear bond strength of 3 cold isostatic pressed zirconia materials and a feldspathic veneer by analyzing their interface with micro-Raman spectroscopy. MATERIAL AND METHODS: The test groups were experimental zirconia, Zirkonzahn zirconia, and Schuetz zirconia. Blocks of partially sintered zirconia were cut into disks (n=20) and then veneered with a feldspathic porcelain. Half of the specimens from each group (n=10) were incubated in 37°C water for 24 hours, and the other half were thermocycled. All the specimens were then subjected to shear testing. The fractured areas were analyzed with optical stereomicroscopy and classified as adhesive, cohesive, or an adhesive-cohesive failure. Spectral patterns were examined to detect bands related to the zirconia and feldspathic porcelain phases. The shear strength data were submitted to 2-way ANOVA. RESULTS: No significant differences in shear bond strength were observed among the 3 groups, regardless of whether or not the specimens were thermocycled. Adhesive failures were the most prevalent types of failure (70%). Raman spectra were clearly distinguished for all the materials, which showed the presence of tetragonal and monoclinic phases. CONCLUSIONS: The controlled production of the experimental zirconia did not influence the results of the bond strength. Raman analysis suggested a process of interdiffusion by the presence of peaks associated with the zirconia and feldspathic ceramics.

Bonding to bleached enamel treated with 10% sodium bicarbonate: a one-year follow-up / Restaurações adesivas em esmalte clareado tratado com solução de bicarbonato de sódio a 10% - 1 ano de avaliação clínica

Objective: The aim of this case report is to present the 1-year follow-up of composite resin restorations performed on imediate bleached enamel. Clinical considerations: The presence of residual oxygen after bleaching may be responsible for inhibiting the polymerization of the monomers present in the adhesive systems, leading to the failure of the restorative procedure. The use of antioxidants, especially the 10% sodium bicarbonate solution (SB), could be a fast and practical alternative to improve the bond strength of these restorations. Patient with high aesthetic demands submitted to the office bleaching with hydrogen peroxide 35% received restorative procedure performed immediately after bleaching. After unsatisfactory resin composite restorations removal, the antioxidant SB was applied and the restorative procedure performed.After one year, the clinical performance of the restorations were successful, showing no signs of failure nor infiltration. Conclusions: The use of the 10% sodium bicarbonate in bleached enamel seems to be a viable alternative for clinical practice, however a large number of restorations of longitudinal researches will be need for corroborate this technique...

Objetivo: O objetivo desse relato de caso clínico é apresentar o acompanhamento de 1 ano de restaurações de resina composta realizadas em esmalte dentário recém-clareado. Considerações clínicas: A presença de oxigénio residual após o clareamento dentário pode ser responsável pela inibição da polimerização dos monômeros presentes nos sistemas adesivos, que pode acarretar em falha do processo restaurador. A utilização de antioxidantes, especialmente a solução de bicarbonato de sódio a 10% (SB), pode ser uma alternativa rápida e prática para melhorar a resistência de união destas restaurações. Em um paciente com alta exigência estética submetido ao clareamento de consultório com peróxido de hidrogénio a 35% foi realizado o procedimento restaurador imediatamente após o clareamento dentário. Após a remoção das restaurações insatisfatórias de resina composta, o antioxidante SB foi aplicado e o procedimento restaurador realizado imediatamente. Após um ano, o desempenho clínico das restaurações de resina composta foram adequadas, não mostrando sinais de falhas nem de infiltração marginal. Conclusões: O uso da solução de bicarbonato de sódio a 10% no esmalte clareado se mostrou uma alternativa viável e prática, contudo um maior número de estudos longitudinais é necessário afim de corroborar com a técnica utilizada neste caso clínico...

Mechanical behavior of NiCr and NiCrTi alloys for implant prosthetic components / Comportamento Mecânico de ligas NiCr e NiCrTi utilizados para componentes protéticos de implantes

Objective: The aim of this study was to evaluate the tensile and hardness mechanical properties, as well as the composition and microstructure of three different alloys used for implant prosthestic components casting. Methods: The alloys were divided into three groups: Tilite (Tilite), Vera (Verabond) and Malloy (DanCeramalloy). For the tensile test, the specimens (n = 10) of each group were evaluated in “alter” form and the maximum load fracture, the deformation at maximum load and Young´s modulus were determined. The data was subjected to one-way ANOVA and Turkey’s test. For the hardness test, five discs from each group were evaluated for Vickers hardness. The data was analyzed using multiple regression ANOVA followed by the Turkey’s test. The significance level was set at 5% (α = 0.05). The composition and microstructure was determined through analysis of two specimens from each group by metallographic analysis (MEV/EED). Results: With regards to maximum load tensile, the deformation and the Young´s Modulus the three alloys evaluated were statistically similar. Regarding hardness, Tilite showed significant higher values than the others alloys. Conclusion: All the examined alloys can be used in implant prosthetic components and the presence of the element Ti did not influence the mechanical behavior of the alloy

Objetivo: O objetivo deste estudo foi avaliar as propriedades mecânicas de tensão e dureza, assim com a composição e microestrutura de três diferentes ligas utilizadas em componentes protéticos de implantes. Métodos: As ligas foram divididas em três grupos: Tilite (Tilite), Vera (Verabond) e Malloy (DanCeramalloy). Para o teste de tensão, os espécimes (n = 10) de cada grupo foram avaliados em forma modificada e a força máxima de fratura, a deformação em carga máxima e o módulo de Young foram determinados. Os dados foram submetidos ao teste ANOVA a um fator e teste de Tukey. Cinco discos de cada grupo foram avaliados para o teste de dureza Vickers. Os dados foram analisados utilizando o teste ANOVA de regressão múltipla, seguido do teste de Tukey. O nível de significância adotado foi de 5% (α = 0,05). A composição e microestrutura foram determinados em dois espécimes de cada grupo por meio de análise metalográfica (MEV/EED). Resultados: Não houve diferenças estatísticas entre as três ligas estudadas em relação à força de tensão máxima, à deformação e ao modulo Young. Em relação à dureza, Tilite mostrou valores estatisticamente superiores em comparação às outras ligas. Conclusão: Todas as ligas examinadas podem ser utilizados em componentes protéticos de implantes e a presença do elemento Titânio não influenciou o comportamento das ligas.

Microabrasion technique for enamel with fluorosis: a case report utilizing two distinct pastes / Técnicas de microabrasão no esmalte com fluorose: relato de caso clínico utilizando duas diferentes pastas

A técnica de microabrasão do esmalte é considerada uma alternativa conservadora e efetiva para remoção de manchas e irregularidades superficiais do esmalte e diferentes pastas podem ser usadas para essa finalidade. Objetivo: O objetivo desse estudo foi comparar a eficácia da técnica de microabrasão do esmalte com fluorose utilizando duas diferentes pastas. Material e Métodos: Paciente, gênero feminino, 18 anos de idade, foi submetida ao tratamento de microabrasão do esmalte, sendo que na arcada superior direita foi manipulada e aplicada a pasta à base de pedra-pomes (SSWhite) e ácido fosfórico a 37% (Alpha Etch, DFL) na proporção de 1:1 e na arcada superior esquerda uma pasta à base de ácido hidroclorídrico a 6,6% e óxido de silício (Micropol, DMC Equipamentos Ltda). Nas duas hemi-arcadas foi realizado o mesmo protocolo clínico por três vezes, sendo que a aplicação da pasta foi de 1 mm de espessura e a realização da microabrasão se deu por fricção mecânica com taça de borracha acoplada em baixa rotação por 10 s. Em seguida os dentes foram polidos com disco de feltro e pasta diamantada e aplicado flúor tópico APF 1,23% por 3 min. Resultados: Os resultados clínicos foram similares em ambas arcadas, independente da pasta utilizada. O sucesso na remoção de manchas no esmalte está dieretamente relacionada com o correto diagnóstico e a precisa indicação da técnica de microabrasão. Conclusões: Foi possível concluir que a as duas diferentes pastas utilizadas para a microabrasão do esmalte foram efetivas na remoção de machas intrínsecas por fluorose com resultados similares e com o restabelecimento estético dos dentes envolvidos.

The technique of enamel microabrasion is considered an aesthetic alternative conservative and effective for stain removal or surface irregularities of the enamel and different materials or pastes can be used for this purpose Objetives: The objective of this study was to compare the efficiency of the technique of enamel microabrasion using two different pastes at removing hypoplastic stains by fluorosis. Methods: The female patient, 18 years, was submitted to enamel microabrasion, and in the right half of the maxilla was manipulated in the proportion of 1:1 by volume a paste of pumice (SSWhite) and 37% phosphoric acid (Etch Alpha, DFL), and in the left half of the maxilla used paste based on hydrochloric acid and 6.6% silicon carbide (Micropol, DMC Equipment Ltd.). In both hemi-arches was performed the same clinical protocol and repeated three times, by the application of 1.0 mm thickness of paste and realized the enamel microabrasion through mechanical friction with rubber cup at low speed for 10 s. Then, the teeth were polished with felt disc and diamond paste, and topical fluoride APF 1.23% for 3 min was applied. Results: The clinical outcome was similar for both hemi-arches, regardless of the used technique. The success in removing stains on tooth enamel is directly related to a correct diagnosis and accurate indication of microabrasion technique. Conclusions: It can be concluded that the two pastes used in the enamel microabrasion were effective for removing intrinsic stains from fluorosis, with similar results and with the re-establishment of aesthetics of the teeth involved.

Propriedades mecânicas e caracterização intrínseca de zircônia experimental para uso em sistemas CAD/CAM / Mechanical and intrinsic characterization of an experimental zirconia composition

O objetivo deste estudo foi avaliar as propriedades mecânicas e as características intrínsecas de uma zircônia tetragonal policristalina parcialmente estabilizada por ítria (Y-TZP) experimental comparada a outras três Y-TZPs comercialmente disponíveis, a partir de blocos para sistema CAD/CAM. Os grupos foram: Y-TZP Experimental (ZE), Zirconcad (ZCA), IPS e.max ZirCad (ZMAX) e In Ceram YZ (ZYZ). Resistência flexural: 120 espécimes foram construídos para cada grupo (n=30) e submetidos ao ensaio de flexão em três pontos com velocidade de 0,5mm/min, de acordo com a ISO 6872. ANOVA a um critério foi utilizada para análise de diferenças significantes entre os grupos (α=0,05). Para a caracterização da resistência e longevidade dos materiais estudados, utilizou-se a análise estatística de Weibull por meio de dois parâmetros: o módulo de Weibull (m) e a resistência característica (δ0). Análise Fractográfica: a superfície da fratura dos espécimes foi analisada pelo microscópio eletrônico de varredura (MEV) sendo que o tamanho do defeito crítico (c) e a tenacidade à fratura (KIC) foi estimado por análise fractográfica quantitativa e sua caracterização por meio de análise fractográfica qualitativa. Espectroscopia Micro Raman: as fases da estrutura cristalina das diferentes Y-TZP foram identificadas por meio da detecção das bandas características. Houve diferença significativa (p <0,05) na resistência à flexão entre ZCA, que apresentou os menores valores, em comparação com ZE, ZMAX e ZYZ, que, por sua vez, foram semelhantes entre si. As superfícies fraturadas de todos os espécimes apresentaram marcas fractográficas características, sendo observada na superfície de ZCA uma maior quantidade de defeitos. Os valores de tenacidade à fratura de ZE foram significantemente diferente apenas para ZCA. Todos os materiais apresentaram as bandas características das fases tetragonal e monoclínica da Y-TZP. ZE mostrou-se semelhante em suas propriedades mecânicas e microestrutura às ZMAX...

The aim of this study was to evaluate the mechanical properties and the intrinsic characteristics of an experimental yttrium tetragonal zirconia partially stabilized (Y-TZP) compared the other three Y-TZPs commercially available starting block for CAD/CAM system. The groups were: Experimental Zirconia (ZE), Zirconcad (ZCA), IPS e.max ZirCad (ZMAX) and In Ceram YZ (ZYZ). Flexural strength: 120 specimens were constructed for each group (n=30) and subjected to bending test at three points crosshead speed of 0.5mm/min, according to ISO 6872. ANOVA test was used to analyze significant differences between groups (α=0.05). To characterize the strength and longevity of the materials, the Weibull statistical analysis by two parameters were used: the Weibull modulus (m) and the characteristic strength (δ0). Fractographic analyzes: the fracture surface of the specimens was analyzed by scanning electron microscope (SEM) and the size of the critical defect (c) and fracture toughness (KIC) was estimated by quantitative fractographic analysis and characterization through qualitative analysis. Micro Raman spectroscopy: phases of crystalline structures of different Y-TZP were identified by detecting the characteristic bands. Statistically significant (p <0.05) in flexural strength between ZCA, which had the lowest values compared with ZE, ZMAX and ZYZ, which in turn were similar. The fractured surfaces of all specimens showed similar fractographics characteristics and values of fracture toughness for ZE were significant difference only for ZCA. All materials showed the characteristic bands of tetragonal and monoclinic phases of zirconia. ZE were similar in its mechanical properties and intrinsic, which suggests that material capable of being used for the system CAD/CAM and applied clinically as framework.

Effect of thermo-mechanical load cycling on silorane-based composite restorations.

The aim of this study was to compare the formation of marginal gaps after thermo-mechanical load cycling, between siloranebased and methacrylate-based restorations. Standardized class II cavities were made in 10 permanent human third molars that were restored with the adhesive system Clearfil SE Bond+composite Filtek Z-350 (Methacrylates) and with the composite bonding Filtek P90+P90 (Siloranes), respectively. After 24 h of storage in 100% humidity at 37°C, the restoration margins were stained, photographed, and evaluated. The gap length was calculated as the percentage of the total length of the margins. Thereafter, the specimens were tested by a thermo-mechanical machine and the marginal gap formation of the specimens was re-evaluated. The results were expressed as percentages of gaps and were submitted to a Mann Whitney test at 5% level of significance. Methacrylates showed a statistically significant higher percentage of gaps than Siloranes, both before and after cycling.

Remodelação do tecido ósseo peri-implantar e apoptose / Peri-implantar bone tissue remodeling and apoptosis

O processo de remodelação óssea requer aaposição óssea por osteoblastos e a reabsorçãopor osteoclastos. Mecanismos de açãoinfluenciam o equilíbrio celular em contínua remodelaçãoóssea e grande parte das pesquisas direcionou-se para o estudo de fatores capazes de modularas funções. O normal processo de neoformação eadaptação óssea dependem do funcionamento deambos os tipos celulares. O osteoblasto é a célulamais importante nesse processo de reparação durantea osseointegração e o sucesso do tratamentodepende da sua adesão e proliferação. A maiorquota de responsabilidade da plasticidade do tecidoósseo cabe aos osteoclastos que respondema estímulos que promovem reabsorção da matrizinorgânica e liberação de componentes constituintes.Proteínas existentes no interior dososteoclastos atuam como mecanismo de inibiçãosobre as armas de autodestruição ouapoptose. Os processos de morte celular podemser classificados de acordo com suas característicasmorfológicas e bioquímicas em apoptose ou necrose.Na apoptose, não há o derramamento do conteúdocelular como ocorre na necrose e, por estarazão, não existe reação inflamatória.

The process of bone remodeling requires theaffixing by osteoblasts and bone resorptionby osteoclasts. Mechanisms of action influencethe cellular balance continuous remodelingand most of the research directed to thestudy of factors that modulate the functions.Normal process of neoformation and boneadaptation depends on the functioning ofboth cell types. The osteoblast cell is moreimportant in this repair process during osseointegrationand the success of treatmentdepends on the adhesion and proliferation.The largest share of the responsibility of theplasticity of bone tissue is up to osteoclastswhich respond to stimuli that promote reabsorptionof inorganic matrix and release ofcomponents constituents. Proteins withinthe existing osteoclasts act as a mechanismof inhibition on weapons of destruction orapoptosis. The processes of cell death can beclassified according to their morphologicaland biochemical characteristics: apoptosis ornecrosis. In apoptosis, there is no spillage ofthe contents as in cell necrosis and thereforethere is no inflammatory reaction.