Influência do número de refundições da liga Ni-Cr-Mo-Ti sobre as propriedades de próteses metalocerâmicas

A frequently encountered difficulty in oral prosthetics is associated with the loss of metallic alloys during the melting stage of the production of metal-ceramic replacement systems. Remelting such materials could impar their use in oral rehabilitation due to loss in esthetics, as well as in the chemical, physical, electrochemical and mechanical properties. Nowadays, the Ni-Cr-Mo-Ti alloy is widely used in metal-ceramic systems. Manufacturers state that this material can be remelted without significant alterations in its behavior, however little has been established as to the changes in the performance of this alloy after successive remelting, which is common practice in oral prosthetics. Therefore, the objective of this study was to evaluate possible changes in the esthetics and associated properties of metalceramic samples consisting of Ni-Cr-Mo-Ti and dental porcelain. Three to five remelting steps were carried out. The results revealed that Ni-Cr-Mo-Ti can be safely used even after three remelting steps. Further remelting significantly affect the characteristics of the alloys and should not be recommended for the manufacture of metal-ceramic systems

Caracterização Microestrutural e Tribocorrosiva de Sistemas Metalocerâmicos Odontológicos do Tipo Ni-Cr/Porcelana E Ni-Cr/Ti/Porcelana

The partial fixed prosthodontics restoration is used to rehabilitate form and function of partial or total compromised teeth, having to remain permanently joined to remainder tooth. The most useful material on prosthodontics is the feldspar porcelain, commercialized as aluminosilicate powders. Dental porcelains are presented with limited mechanical properties to rehabilitate extensive spaces. The association with Ni-Cr metallic systems (metal-ceramic system) allows that the metallic substructure compensates the fragile porcelain nature, preserving the thermal insulation and aesthetics desirable, as well as reducing the possibility of cracking during matication efforts. Cohesive flaws by low mechanical strength connect the metallic substructure to the oral environment, characterized by a electrolytic solution (saliva), by aggressive temperature, pH cyclic changes and mechanical requests. This process results on ionic liberation that could promote allergic or inflammatory responses, and/or clinical degradation of ceramometal system. The aim of this study was to evaluate the presence of an intermediate titanium layer on the microscopic fracture behavior of porcelains on ceramometal systems. Plasma deposition of titanium films result in regular passivating oxide layers which act as barriers to protect the metallic substrate against the hazardous effects of corrosive saliva. Tribocorrosion tests were performed to simulate the oral environment and mechanical stress, making it possible the early detection of crack formation and growth on metal-ceramic systems, which estimate the adherence between the compounds of this system. Plain samples consisting of dental feldspar porcelain deposited either onto metallic substrates or titanium films were fired and characterized by scanning electron microscopy. The result showed that the titanium film improved the adherence of the system compared to conventional metal-ceramic interfaces, thus holding crack propagation

Obtenção de uma porcelana dielétrica a partir de matérias-primas do Rio Grande do Norte

The dielectric porcelain is usually obtained by mixing various raw materials proportions and is used in the production of electronic equipment for various applications, from capacitors of high and low Power to insulators for low, medium, high and extra high voltage, which are used in distribution lines and transmission of electricity.This work was directed to the s tudy of technological properties of technic porcelain, made from raw materials extracted from pegmatites found in the regions of Seridó and the Alto Oeste of Rio Grande do Norte, which are made of kaolin, quartz and feldspar, abundant and high quality in these regions. The technic ceramics were obtained by mixing in appropriate levels, kaolin, feldspar, quartz and clay, the last item from a pottery in the city of Sao Gonçalo do Amarante, Rio Grande do Norte. During the development the following characterizations correlated to raw materials were made: laser particle sizing, x-ray diffraction, DTA and TG. The compositions studied were formed by uniaxial pressing at a pressure of 50 MPa and sintered at temperatures ranging from 1150 to 1350ºC and levels (times) of sintering between 30, 60, 90 and 120 minutes. The characterization of the samples were taken from the analysis of weight loss, linear shrinkage, porosity, stoneware curve, bulk density, flexural strength of three points, SEM and X-ray diffraction, TMA, Dielectric and cross Resistivity. The studied materials can be employed in producing the objects used in electrical engineering such as: insulators for low, medium and high-voltage electrical systems, command devices, bushing insulation for transformers, power capacitors, spark plugs, receptacles for fluorescent and incandescent light bulbs and others

Efeito das variáveis laboratoriais protéticas na adesão da porcelana com ligas de níquel-cromo

The metalceramic crowns are usually used in dentistry because they provide a resistant structure due to its metallic base and its aesthetics from the porcelain that recovers this structure. To manufacture these crowns, a series of stages should be accomplished in the prosthetic laboratories, and many variables can influence its success. Changes in these variables cause alterations in the metallic alloy and in the porcelain, so, as consequence, in the adhesion between them. The composition of the metal alloy can be modified by recasting alloys, a common practice in some prosthetic laboratories. The aim of this paper is to make a systematic study investigating metalceramic crowns as well as analyzing the effect of recasting Ni-Cr alloys. Another variable which can influence the mechanism of metalceramic union is the temperature used in firing porcelain procedure. Each porcelain has to be fired in a fixed temperature which is determined by the manufacturer and its change can cause serious damages. This research simulate situations that may occur on laboratory procedures and observe their consequences in the quality of the metalceramic union. A scanning eletron microscopy and an optic microscopy were accomplish to analyse the metal-ceramic interface. No differences have been found when remelting alloys were used. The microhardness were similar in Ni-Cr alloys casted once, twice and three times. A wettability test was accomplished using a software developed at the Laboratório de Processamento de Materiais por Plasma, on the Universidade Federal do Rio Grande do Norte. No differences were found in the contact angle between the solid surface (metallic substratum) and the tangencial plane to the liquid surface (opaque). To analyse if the temperature of porcelain firing procedure could influence the contact area between metal and porcelain, a variation in its final temperature was achieve from 980° to 955°C. Once more, no differences have been found

Liberação de cálcio e magnésio por cápsulas porosas de porcelana usadas na extração de solução do solo

O uso de cápsulas porosas para extração de solução do solo é interessante por ser um ensaio não-destrutivo. Entretanto, persistem dúvidas sobre a liberação de íons da própria cápsula, que podem contaminar a solução extraída. Foram realizados testes na Faculdade de Ciências Agronômicas/UNESP, Botucatu (SP), com o objetivo de verificar a liberação de Ca e de Mg por cápsulas porosas de porcelana. No primeiro, foram empregados quatro tratamentos: T1 - lavagem das cápsulas com água destilada, forçando sua passagem pelas cápsulas, utilizando uma bomba a vácuo; T2 - lavagem das cápsulas com HCl 0,1 mol L-1, forçando sua passagem pelas cápsulas, utilizando uma bomba a vácuo; T3 - lavagem das cápsulas com água destilada, sem vácuo, e T4 - lavagem das cápsulas com HCl 0,1 mol L-1, sem vácuo, em um tempo de imersão de 24 h (para T3 e T4). No segundo teste, as cápsulas tratadas com HCl 0,1 mol L-1 no primeiro teste foram lavadas com água destilada novamente e deixadas de molho em água destilada e deionizada durante 45 min. Após estes procedimentos, as cápsulas foram imersas em água destilada, tomando-se alícotas desta solução para determinação de pH e dos teores de Ca e Mg após contato com as cápsulas por 0; 0,5; 1,0; 2,0; 4,0 e 24 h. Cada tratamento teve quatro repetições. Não se observou liberação significativa de Ca e Mg das cápsulas porosas para a solução, quando foram preparadas utilizando-se da passagem de HCl 0,1 mol L-1 a vácuo e água destilada, e deixadas, a seguir, em água destilada e deionizada durante 4 h.

Avaliação da eficácia de selante ionomérico modificado por resina e escovação dentária na preservação de cárie oclusal

The purpose of this study was to evaluate the effectiveness during a twelve-month period, of resin-modified glass ionomer (Vitremer@) used as fissure sealants compared to supervised teeth brushing in the prevention of oclusal caries in permarient molars of pubIlc school children from 5 to 7 years of age. A total of 91 children participated in the study, being randomly divided up into three groups of investigation: group with sealant (n=31), group of supervised brushing (m=30), and control gorup (n=30). After 12 months, a total of 28.5% of tosses in the sample of 26 children was registered, and although there wasn t a significant diference between these losses and the groups studles (p = 0.6355), there was a considerable reduction in the sample. The results showed that none of the independentIy studied variables (present caries experience, biofilm, bleeding, sealant retention, position of the tooth in the arch, and sex) interfered in the final results, and that there was no significant difference between applying the sealant in question, perfornling supervised dental brushing, or not intervening at alI (p=0.542). These results could have been a consequence of the limitations found alI through the study, especially relating to the losses occurred because of school evasion, transfer, or because of the accident in the Marise Paiva Municipal School, Keeping students away for approximately one semester, so tht a new reseach had to be developed sos as to better clarify the effects among the treatments done there

Avaliação clínica e radiográfica das complicações técnicas em próteses sobre implantes

The evaluation criteria of the cases treated with dental implants are based on clinical and radiographic tests. In this context it is important to conduct research to determine prognosis of different types of prosthetic rehabilitation and determination of the main problems affecting this type of treatment. Thus, the objective of this study was to assess the prosthetic conditions of individuals rehabilitated with implant-supported prosthesis. In this cross-sectional study 153 patients were treated, accounting for a sample of 509 implants. The failures were observed by clinical and radiographic examination. The results showed that the fracture (0.2%) loss (0.4%) and loosening of the screws (3.3%) were failures are less frequent. The fracture structures as the resin (12.4%), porcelain (5.5%) and metallic (1.5%), loss of resin that covers the screw (23.8%) and loss of retention overdentures on implants (18.6%) had a higher occurrence. The failure of adaptation between the abutment and the implant (6.9%) and especially between the prosthesis and the abutment (25.4%) had a high prevalence and, when related to other parameters showed a significant association, particularly with the cemented prosthesis (OR = 6.79). It can be concluded that to minimize the appearance of failures, protocols must be observed from diagnosis to the settlement and control of prostheses on implants, particularly with respect to technical steps of the making of the prosthesis and care in radiographic evaluating the fit between their components

Bolton freeware: aplicativo de avaliação de discrepância de massa dentária desenvolvido pelo programa de pós-graduação em odontologia/UFRN

The calculation of tooth mass discrepancy, essential for good planning and a proper orthodontic finishing, when performed manually, besides being laborious, requires considerable time consumption. The aim of this study was to develop and test Bolton Freeware, a software for analysis of the tooth mass discrepancy of Bolton, aiming to minimize the consumption of time in a less onerous way. The digital analysis of the software was done by means of two-dimensional scanning of plaster study models and compared to manual evaluation (gold standard), using 75 pairs of stone plaster study models divided into two groups according to the magnitude of the Curve of Spee (group I from 0 to 2 mm, group II greater than 2 to 3mm). All the models had permanent dentition and were in perfect condition. The manual evaluation was performed with a digital caliper and a calculator, and the time required to perform the analysis for both methods was recorded and compared. In addition, the software was evaluated by orthodontists regarding its use, by means of questionnaires developed specifically for this purpose. Calibration was performed prior to manual analysis, and excellent levels of inter-rater agreement were achieved, with ICC > 0.75 and r > 0.9 for total and anterior proportion. It was observed in the evaluation of error of the digital method that some teeth showed a significant systematic error, being the highest measured at 0.08 mm. The analysis of total tooth mass discrepancy performed by Bolton Freeware, for those cases in which the curve of Spee is mild and moderate, differ from manual analysis, on average, 0.09 mm and 0.07 mm respectively, for each tooth evaluated, with r> 0, 8 for total and anterior proportion. According to the specificity and sensitivity test, Bolton Freeware has an improved ability to detect true negatives, i.e. the presence of discrepancy. The Bolton analysis digitally performed was faster, with an average difference of time consumed to perform the analysis of Bolton between the two methods of approximately 6 minutes. Most experts interviewed (93%) approved the usability of the software

Técnicas radiográficas intra e extrabucal na avaliação dentária de cães com doença periodontal

Foram avaliadas as técnicas radiográficas dentárias intra (TIB) e extrabucal (TEB) em 50 cães com doença periodontal, no intuito de padronizar os procedimentos de diagnóstico dessa síndrome. A TIB revelou que 16 animais não apresentaram lesões ósseas visíveis, enquanto a TEB apontou que 39 pacientes foram negativos para as mesmas lesões. em resumo, a TIB foi mais eficaz na detecção de sinais radiográficos, especialmente as chamadas lesões finas, que a TEB, sendo a técnica de escolha na síndrome periodontal.

Prevalência de oclusopatias e comparação entre a Classificação de Angle e o Índice de Estética Dentária em escolares do interior do estado de São Paulo - Brasil

INTRODUÇÃO: as oclusopatias estão entre os principais problemas de saúde bucal em todo o mundo, juntamente com a cárie dentária e a doença periodontal, e vários índices têm sido utilizados para registrá-las. OBJETIVOS: verificar a prevalência de oclusopatias utilizando a Classificação de Angle e o Índice de Estética Dentária (DAI), sua severidade e a necessidade de tratamento ortodôntico registradas pelo DAI, e comparar os resultados de ambos os índices, visando correlacionar o padrão dos dados coletados e a viabilidade de utilizá-los de forma conjunta. MÉTODOS: a amostra consistiu de 734 escolares com idade de 12 anos, de ambos os sexos, da rede pública do município de Lins/SP. Foram realizados exames nos pátios das escolas com utilização de sondas IPC a olho nu. RESULTADOS: pela Classificação de Angle, encontrou-se 33,24% das crianças com oclusão normal e 66,76% com má oclusão. Pelo DAI, observou-se que 65,26% das crianças apresentavam-se sem anormalidades ou com más oclusões leves. A má oclusão definida esteve presente em 12,81%, a má oclusão severa foi observada em 10,90% e a muito severa ou incapacitante em 11,03%. A maioria das crianças (70,57%) apresentou relação molar normal, e o overjet maxilar anterior foi a alteração mais frequentemente observada. No cruzamento dos índices houve semelhanças e divergências. CONCLUSÃO: o DAI não foi sensível a alguns problemas de oclusão detectados pela Classificação de Angle, e a recíproca foi verdadeira, demonstrando que ambos os índices possuem pontos distintos na detecção das oclusopatias, podendo ser utilizados de forma reciprocamente complementar.

Processo de reparo em feridas de extração dentária em camundongos tratados com o complexo Symphytum officinale e Calendula officinallis

Medicamentos homeopáticos como o Symphytum officinalle e a Calendula officinallis são dotados de propriedades anti-sépticas, antiinflamatória, cicatrizantes e também agem como promotores da consolidação de fraturas ósseas. Neste trabalho, uniram-se esses dois medicamentos similares em um complexo para verificar o seu efeito no reparo em feridas de extração dentária em camundongos. O complexo Symphytum officinalle e Calendula officinallis nas potências de 6CH e 3CH, respectivamente, foi ministrado por via oral ao grupo tratado durante 5 dias antes e após a extração do incisivo superior direito. No grupo controle, administraram-se 5ml de álcool etílico a 70% diluídos em 30 ml de soro fisiológico. Após a proservação, os animais foram sacrificados, a maxila direita separada da esquerda, fixada e processada para inclusão em parafina. Após a microtomia, os cortes obtidos foram corados pela H/E. A análise histológica mostrou que, tanto no grupo controle como no tratado, o alvéolo dentário estava preenchido por tecido de granulação e tecido ósseo neoformado, com graus variáveis de maturação, rico em osteócitos. No entanto, nos animais tratados, o processo de reparo em feridas após extração dentária do incisivo superior direito mostrou um avanço progressivo de neoformação óssea mais acentuado quando comparado ao grupo controle, em tempos equivalentes. Estes resultados enfatizam as propriedades biológicas do complexo Symphytum officinalle e Calendula officinallis e sua possível utilização como recurso terapêutico na Odontologia.

Investigação da Interface Metal-Porcelana da Liga Ni-Cr-Mo Soldada a LASER

The interface formed between the metal and the porcelain of a LASER welded Ni-Cr-Mo alloy was studied. The characterization was carried out through optical microscopy, scanning electron microscopy, X-ray dispersive spectroscopy-EDS and mechanical testing by three-point flexion test-TPE in the region LASER welded with and without the porcelain. The porcelain adhesion with the alloy alone is possible after the oxidation of the metallic surface and subsequent application of an adhesive called opaco. The applied porcelain, on the base metal and fusion zone presented some distinct behaviors. After the TPF test the base metal presented fractures while that in the fusion zone was completely gone. One noticed that the region submitted to the LASER welding showed less porcelain adhesion than the region of the base metal due to the microestructural refinement of the fusion zone. These results can be evidenced by the EDS of the studied regions. The TPF had demonstrated that the Ni-Cr-Mo alloy submitted to the LASER welding, undergone significant alterations in its mechanical properties after the application of the porcelain.

Prevalência de fluorose dentária em escolares de Marinópolis, São Paulo

O objetivo deste estudo foi determinar a freqüência e severidade da fluorose dentária em escolares de 5 a 12 e de 15 anos de idade da cidade de Marinópolis, São Paulo, Brasil, com o propósito de se obter um banco de dados-base inicial para o monitoramento da fluorose dentária nesta população. Foram envolvidos todos os escolares de ambos os sexos, nas idades citadas, matriculados nas instituições de ensino da referida cidade e tendo como pré-requisito a condição de residirem em Marinópolis desde o nascimento, totalizando 320 escolares. Os exames foram realizados por um examinador previamente calibrado para a aplicação do Índice de Dean. de acordo com os resultados, a prevalência de fluorose dentária no grupo estudado foi de 17,2%; no entanto, considerando apenas os graus de fluorose que determinam comprometimento estético (leve, moderado e severo), o percentual foi de 7,19%. O grau predominante foi o muito leve (10,0%) seguido pelos graus leve (5,3%), moderado (1,3%) e severo (0,6%). Conclui-se que a fluorose dentária na população estudada não se constitui em problema de amplas dimensões; estudos posteriores, contudo, são necessários, a fim de identificar as causas da presença de casos de fluorose moderada e severa.

IgA anti-Streptococcus mutans em crianças com e sem cárie dentária

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)