Efeito da aplicação de carga em coroas de diferentes materiais, confeccionadas sobre implantes unitários curtos e com diferentes diâmetros nas deformações da crista óssea: análise in vitro e in silico / Effect of the load application on crowns of different materials made on short unitary implants with different diameters in bone crest deformations: in vitro and in silico analysis

O intuito deste estudo in vitro e in silico, foi analisar as microdeformações, geradas pela aplicação de carga vertical, sobre coroas de 3 tipos de materiais restauradores diferentes (Zircônia, Dissilicato de Lítio e Cromo Cobalto), que foram selecionadas, através da biblioteca do software SMART DENT/Exocad (Darmstadt - Germany) e confeccionadas, através da tecnologia cad/cam, suportadas por implantes curtos (8mm), conexão cone morse, com diversos diâmetros (3,5 mm; 4,0 mm e 5,0 mm). Os implantes foram instalados 2mm infraósseo para análise através de elementos finitos e da extensometria. Foram confeccionados 3 blocos de poliuretano: bloco 1 (grupo experimento) no qual foi colocado um implante Titamax CM Neodent 3,5 X 08 mm, bloco 2 (grupo controle) no qual foi colocado um implante titamax CM Neodent 4,0 X 08 mm e bloco 3 (grupo controle) no qual foi colocado um implante titamax CM Neodent 5,0 X 08 mm. Pilares protéticos retos (Base de Titânio 4,5 - Neodent) foram instalados sobre os respectivos implantes sendo instalados 4 extensômetros, na região superior dos blocos ao redor dos implantes. Foi aplicada uma carga vertical de 300N ao redor da abertura de acesso do parafuso protético das coroas. Para a análise por elementos finitos (FEA), o mesmo bloco foi modelado e analisado sob a mesma carga de 300N. Os valores de tensão e deformação foram analisados quanto à correlação com a extensometria. A estatística inferencial consistiu no teste de análise de variância de Friedmann, um fator efeito fixo. Para o nível de significância, foi escolhido o valor convencional de 5%. Os resultados demonstraram haver diferença estatística significante para o fator diâmetro (p = 0,0001) no qual os implantes, com 3,5 mm de diâmetro apresentaram os maiores picos de microdeformações. Quando se analisa o material restaurador, observa-se que não houve diferenças estatísticas significativas (p = 0,783). Dentro das limitações deste estudo, pode-se concluir que a utilização de implantes unitários, curtos e estreitos com conexão cone morse instalados 2 mm infraósseo, são uma opção viável para reabilitações em regiões posteriores independente do material restaurador escolhido(AU)

The aim of this in vitro and in silico study was to analyze the microdeformations generated by the application of vertical load on crowns of 3 different types of restorative materials (Zirconia, Lithium Dissilicate and Cobalt Chromium) that were selected through the software library SMART DENT / Exocad (Darmstadt - Germany), and made using cad / cam technology, supported by short implants (8 mm), cone morse connection with various diameters (3.5 mm, 4.0 mm and 5.0 mm). These were installed 2 mm subcrestal for finite element analysis and extensometry. Three blocks of polyurethane were made; block 1 (experimental group) in which a Titamax CM Neodent 3.5 X 08 mm implant, block 2 (control group) was implanted in which a CM Neodent 4.0 X 08 mm titamax and block 3 (control group) were implanted in which an implant was placed titamax CM Neodent 5.0 X 08 mm. Straight prosthetic abutments (Titanium Base 4.5 - Neodent) were installed on the respective implants and 4 extensometers were installed, in the upper region of the blocks around the implants. A vertical load of 300N was applied around the access opening of the crown prosthetic screw. For the finite element analysis (FEA), the same block was modeled and analyzed under the same 300N load. The stress and strain values were analyzed for correlation with extensometry. The inferential statistics consisted of Friedmann's analysis of variance, a fixed effect factor. For the level of significance, the conventional value of 5% was chosen. The results showed a statistically significant difference for the diameter factor (p = 0.0001) where 3.5 mm diameter implants presented the highest peaks of microdeformations. When analyzing the restorative material, we observed that there were no significant statistical differences (p = 0.783). Within the limitations of this study, we can conclude that the use of short, narrow unit implants with cone morse connection installed 2 mm subcrestal are a viable option for rehabilitation in posterior regions independent of the restorative material chosen(AU)

Toxicology of wear particles of cobalt-chromium alloy metal-on-metal hip implants Part II: Importance of physicochemical properties and dose in animal and in vitro studies as a basis for risk assessment.

The objective of the Part II analysis was to evaluate animal and in vitro toxicology studies of CoCr particles with respect to their physicochemistry and dose relevance to metal-on-metal (MoM) implant patients as derived from Part I. In the various toxicology studies, physicochemical characteristics were infrequently considered and administered doses were orders of magnitude higher than what occurs in patients. Co was consistently shown to rapidly release from CoCr particles for distribution and elimination from the body. CoCr micron sized particles appear more biopersistent in vivo resulting in inflammatory responses that are not seen with similar mass concentrations of nanoparticles. We conclude, that in an attempt to obtain data for a complete risk assessment, future studies need to focus on physicochemical characteristics of nano and micron sized particles and on doses and dose metrics relevant to those generated in patients or in properly conducted hip simulator studies.

Genotoxicity of fixation devices analyzed by the frequencies of sister chromatid exchange.

BACKGROUND: Metal alloys utilized in the management of jaw fractures may exert genotoxic effects. Our purpose was to compare the genotoxicity of intermaxillary fixation devices containing nickel and chromium to that of titanium miniplates utilized in treatment of jaw fractures through the analysis of sister chromatid exchange. METHODS: In this prospective study, in a total of 28 non-smoker patients (10 females, 18 males; mean age 33.43±10.76; range 15 to 60 years) with jaw fractures, 14 were treated with intermaxillary fixation by administration of nickel-chromium wire and arch bar and 14 with titanium miniplates to investigate the genotoxicity of different metal alloys. The outcome variable was the frequency of sister chromatide exchange in peripheral lymphoctyes, determined through the analysis of venous blood samples obtained preoperatively and 4 to 6 weeks postoperatively. RESULTS: The frequency of the average sister chromatid exchange was found to be significantly higher in patients treated with the nickel-chromium intermaxillary fixation devices than those treated by titanium miniplates (1.29±0.29 vs. 0.46±0.39, p<0.001). CONCLUSION: Although titanium miniplate osteosynthesis is an invasive technique in comparison with the nickel-chromium-containing intermaxillary fixation devices, titanium seems to exert less genotoxic effect than the nickel-chromium alloy. However, this finding should be supported in clinical studies with a larger sampling size.

Safety and efficacy of cobalt chromium alloy based sirolimus-eluting stent with bioabsorbable polymer in porcine model.

BACKGROUND: First generation drug-eluting stents (DESs) were based on 316L stainless steel and coated with a permanent polymer. The vessel wall of these DESs was inflammatory and late in-stent thrombosis was reported. Hence, cobalt chromium based DES coated with a bioabsorbable polymer was an alternate choice. METHODS: Cobalt chromium based DES with bioabsorbable polymer (Simrex stent) as well as control stents (Polymer stent and EXCEL(TM) stent) were implanted into porcine arteries. At a designated time, angiography, quantitative coronary angiography (QCA) analysis, histomorphometry, and electron-microscopical follow-up were performed. RESULTS: A total of 98 stents of all the three groups were harvested. At week 24, percent diameter stenosis (%DS), late loss (LL), and percent area stenosis (%AS) of Simrex was (12.9 ± 0.4)%, (0.35 ± 0.02) mm, and (24.5 ± 4.2)%, respectively, without significant difference in comparison to commercialized EXCEL(TM) stent. Slight inflammatory reaction was seen around the stent strut of Simrex, just as in the other two groups. Electron-microscopical follow-up suggested that it might take 4 - 12 weeks for Simrex to complete its re-endothelialization process. CONCLUSIONS: Cobalt chromium based, bioabsorbable polymer coated sirolimus-eluting stent showed excellent biocompatibility. During 24 weeks observation in porcine model, it was proved that this novel DES system successfully inhibited neointima hyperplasia and decreased in-stent stenosis. It is feasible to launch a clinical evaluation to improve the current prognosis of DES implantation.

Clinical and angiographic outcomes after treatment of de novo coronary stenoses with a novel platinum chromium thin-strut stent: primary results of the PERSEUS (Prospective Evaluation in a Randomized Trial of the Safety and Efficacy of the Use of the TAXUS Element Paclitaxel-Eluting Coronary Stent System) trial.

OBJECTIVES: The aim of this study was to evaluate the safety and efficacy of the novel platinum chromium TAXUS Element paclitaxel-eluting stent (PES) compared with the TAXUS Express PES (Boston Scientific, Natick, Massachusetts) in treating coronary artery stenoses. BACKGROUND: The TAXUS Element is a novel thin-strut (81 microm), platinum chromium alloy PES designed to improve radial strength, radiopacity, and deliverability, while safely providing comparable restenosis benefit compared with a previous-generation PES. METHODS: The PERSEUS (Prospective Evaluation in a Randomized Trial of the Safety and Efficacy of the Use of the TAXUS Element Paclitaxel-Eluting Coronary Stent System) Workhorse (WH) trial is a prospective, randomized (3:1), controlled, multicenter study of the TAXUS Element (vs. TAXUS Express) PES for the treatment of de novo coronary atherosclerotic lesionsor=2.75 to

Retençäo de grampos circunferenciais de próteses parciais removíveis em funçäo de tipos de liga, grampos, dentes e número de ciclos de flexäo / Retention of removable partial denture clasps as related to alloy, type of clasps, teeth, and flexural cycling

A pesquisa teve a finalidade de determinar a força de retençäo de grampos circunferenciais para próteses parciais removíveis. Foram usados: 4 ligas de metais básicos(3 de Co-Cr e 1 de i-Cr); grampo padräo e extra (mais fino); dente pré-molar e molar, e determinaçöes, no início e nos subsequentes ciclos (x 1000: l, 5, 15, 25), de colocaçäo dos grampos em máquina automática. Feitos os grampos, foram obtidas as medidas iniciais, o que se repetia após cada período de ciclos. Grampos que näo tinham se fraturado no período anterior, mas estavam sem retençäo, foram ajustados. Os resultados permitiram concluir que: 1) sem ajuste de grampos: as ligas apresentaram diferentes retençöes com o grampo padräo; três ligas apresentaram maior retençäo com o dente molar; a retençäo diminuiu um pouco até 1.000 ciclos, após os quais houve pouca queda; 2) com ajuste de grampos; estes perderam, por período de ciclos, 11 vezes mais retençäo do que os sem ajuste

Revestimentos fosfatados: estudo da desadaptaçäo marginal / Phosphated investments: marginal fit accuracy

Foi estudada a desadaptaçäo marginal em pontes fixas esquemáticas, fundidas em liga de níquel-cromo quando usados diferentes revestimentos de sílico-fosfato em concentraçöes de 50 por cento, 75 por cento e 100 por cento de líquido especial, utilizando-se ou näo anel de fundiçäo. Os resultados demonstraram que os fatores revestimento e concentraçäo de líquido especial foram significativos e que a utilizaçäo ou näo de anel de fundiçäo näo influiu na contraçäo metálica