Reinforced Polymethyl Methacrylate Resin Using Grapheme Derivative For an “All-On-4” Implant- Supported Definitive Mandibular Prosthesis – A Case Report

Since the inception of implant dentistry, implant-supported metal-acrylic resin hybrid prostheses are the major prostheticdevices given to restore physiological and esthetic functions of oral tissues of edentulous or partially edentulous patients. Theclinical performance of the most commonly used acrylic resin in the fabrication of dentures, namely, polymethyl methacrylate(PMMA) resin determines its long-term deformation and wear resistance. However, its poor mechanical resistance to wearand tear poses a major setback. An attempt to incorporate graphene derivative with PMMA resin in prosthesis fabrication hasdemonstrated significant improvement in the mechanical strength as per literature. This case report presents rehabilitation ofedentulous mandibular jaw and also briefly states the properties of graphene and the polymerization process of the resin withthe graphene derivative.

The hydrophobicity and roughness of a nasoenteral tube surface influences the adhesion of a multi-drug resistant strain of Staphylococcus Aureus

In this study, we examined the physiochemical properties of nasoenteral feeding tubes made from two different types of polymer: silicone materials and polyurethane. The internal surfaces of the nasoenteral feeding tubes were analyzed for their hydrophobicity, roughness, microtopography, rupture-tension and ability to stretch. We also studied the adhesion of an isolated, multi-drug resistant strain of S. aureus to these polymers. The polyurethane nasoenteral tube, which was classified as hydrophilic, was more resistant to rupture-tension and stretching tests than the silicone tube, which was classified as hydrophobic. Additionally, the polyurethane tube had a rougher surface than the silicone tube. Approximately 1.0 log CFU.cm-2 of S. aureus cells adhered to the tubes and this number was not statistically different between the two types of surfaces (p > 0.05). In future studies, new polymers for nasoenteral feeding tubes should be tested for their ability to support bacterial growth. Bacterial adhesion to these polymers can easily be reduced through modification of the polymer's physicochemical surface characteristics.

Mechanical resistance of the modified stabilization method for the tibial tuberosity advancement technique: ex vivo experimental study in dogs / Resistência mecânica da técnica de avanço da tuberosidade tibial modificada: estudo experimental ex vivo em cães

The present study aimed to evaluate a modification of the stabilization method of the tibial tuberosity advancement technique (TTA), originally described for stabilization of the cranial cruciate deficient stifle. Ten adult mongrel dogs with weights ranging from 25 to 30kg were used. After euthanasia, the hind-limbs were divided into two groups: G1 - test (n=10), and G2 - control (n=10) represented by the contra lateral limb. The test group was submitted to the modified TTA technique, stabilized by one shaft screw in craniocaudal position and a titanium cage inserted at the osteotomy site. The position of the patellar tendon, 90º in relation to the tibial plateau, and the correct position of all implants were confirmed radiographically after surgery. Posteriorly, in both groups, limbs were harvested and tibias collected with their respectively patellar tendon insertion preserved for the mechanical resistance test. The fixation of the tibial tuberosity with a shaft screw and titanium cage resulted in resistance compatible with the normal physiological forces transferred to the hind-limbs during locomotion. The biomechanical tests confirmed the viability of the method performed for the tibial tuberosity fixation and support future clinical trials to validate the technique.

O presente estudo teve por objetivo avaliar a resistência mecânica do método de estabilização da técnica de avanço da tuberosidade tibial (TTA), originalmente descrita para tratamento da ruptura do ligamento cruzado cranial. Foram avaliados 10 cães, sem raça definida e com massa corporal entre 25 e 30kg. Após a eutanásia, os membros pélvicos foram divididos em dois grupos, sendo que G1 era o grupo teste (n=10) e G2 o controle (n=10), representado pelo membro contralateral. O grupo operado foi submetido à técnica de avanço da tuberosidade tibial (TTA) modificada, com emprego de um parafuso especial em posição craniocaudal e um espaçador de titânio inserido no local de osteotomia. O posicionamento do tendão patelar perpendicularmente ao platô tibial e o correto posicionamento dos implantes foi confirmado radiograficamente em todos os espécimes. Posteriormente, em ambos os grupos foram coletadas as tíbias, com preservação da inserção dos seus respectivos tendões patelares, para realização dos testes de resistência mecânica. A estabilização da tuberosidade tibial por parafuso especial em sentido craniocaudal e espaçador de titânio demonstrou resistência compatível com as forças fisiológicas tradicionalmente impostas ao membro pélvico durante a locomoção. Os testes biomecânicos confirmam a viabilidade do método de estabilização e sustentam estudos clínicos futuros para validação da técnica cirúrgica.

Propriedades mecânicas do cimento ósseo e da poliuretana de mamona com e sem catalisador / Mechanical properties of bone cement and castor oil-based polyurethane with and without a catalyst

Avaliou-se o comportamento mecânico do polímero de mamona, tendo por variáveis o tempo de produção e a presença de catalisador, e utilizando como padrão comparativo o cimento ósseo (polimetilmetacrilato). Foram estabelecidos três grupos experimentais, de acordo com o tipo de corpo de prova (cilindro ou barra) e polímero utilizado, que foram posteriormente subdivididos em subgrupos conforme o tempo após produção, ou seja, 24, 48 e 72 horas. O ensaio de compressão analisou a carga máxima e a tensão e o ensaio de dobramento estudou o módulo de dobramento e a resistência. Estatisticamente não houve diferenças nos valores de resistência à compressão ou ao dobramento às 24, 48 e 72 horas após a produção do polimetilmetacrilato e da poliuretana, com ou sem catalisador. A poliuretana com catalisador foi a mais resistente nos ensaios de compressão, apresentando módulo de dobramento semelhante ao do polimetilmetacrilato e resistência ao dobramento superior à da poliuretana sem catalisador. Conclui-se que: o tempo não alterou as propriedades mecânicas dos compósitos avaliados; o catalisador melhorou o desempenho mecânico da poliuretana de mamona; na resistência mecânica à compressão, a poliuretana com catalisador suportou mais carga que o polimetilmetacrilato.

The mechanical properties of castor oil-based polyurethane was evaluated considering post-production time and the presence of a catalyst as variables and using bone cement (polymethylmetacrylate) as a comparative pattern. According to proof body type (cylinders or bars) and the used polymer, three experimental groups were established. Such groups were later subdivided according to post-production time, namely, 24, 48, and 72 hours. A compression assay analyzed maximum load and tension, and a folding assay evaluated the folding module and resistance. There were no statistical differences in the values for resistance to compression or folding at 24, 48, and 72 hours after the production of polymethylmetacrylate and polyurethane with or without a catalyst. Castor oil-based polyurethane with a catalyst showed to be the most resistant during the compression assays as its folding module was similar to that of polymethylmetacrylate, and its folding resistance was higher than that of polyurethane without a catalyst. In conclusion, time did not change the mechanical properties of the evaluated composites; the catalyst improved the mechanical performance of castor oil-based polyurethane; castor oil-based polyurethane with a catalyst supported more load during the assay for mechanical resistance to compression than did polymethylmetacrylate.

Relação da compactação do solo com a cultura do amendoim / Relationship of soil compaction with peanut crop

O objetivo deste trabalho foi determinar o intervalo hídrico ótimo e sua relação com odesenvolvimento e a produtividade de duas cultivares de amendoim (IAC Tatu ST e IAC 886) em função da compactação, em um Latossolo Vermelho de textura média. Os tratamentos foram constituídos por cinco níveis de compactação, realizados com o tráfego de tratores, com o solo no conteúdo de água retida na capacidade de campo (0,01 MPa). O delineamento experimental foi o inteiramente casualizado, com quatro repetições. Foram coletadas amostras indeformadasnas camadas de 0,02?0,05, 0,08?0,11 e 0,15?0,18 m, para determinação da resistência do solo à penetração (RP), porosidade, retenção de água, densidade do solo (Ds) e do intervalo hídrico ótimo (IHO). O desenvolvimento do amendoim foi avaliado através da altura das plantas, números de ramos, massa seca da parte aérea e produtividade em casca (PC). A PC decresceu linearmente com o aumento da compactação do solo, nas duas cultivares. O IHO diminuiu com o aumentoda compactação, pela RP, até atingir a Dsc de 1,40 Mg m-3, valor próximo a Ds de 1,32 Mg m-3 a partir da qual a PC das duas cultivares decresceu no campo.(AU)

The aim of this work was to determine the least limiting water range and its relation with peanut yield and development in two cultivars (IAC Tatu ST and IAC 886) according to the compaction levels of a medium texture Haplustox soil. The treatments were composed by five compaction levels made with tractor traffic, on a soil at the capacity (0.01 MPa). The completely randomized design with four replications was used. Undisturbed soil samples were collected in the layers of 0.02-0.05, 0.08-0.11 and 0.15-0.18 m for determination of soil resistance to penetration (RP), porosity, water retention, bulk density and least limiting water range. The peanut development was evaluated by plant height, number of branches, plant dry matter and yield. The peanut yield decreased linearly with higher soil compaction, in both cultivars. The least limiting water range decreased with higher compaction by resistance to penetration, till reach the critical bulk density (Ds) of 1.40 Mg m-3. This value is close to 1.32 Mg m-3 from which the peanut yield in both cultivars decreased. (AU)