Influence of Epoxy Resin Curing Kinetics on the Mechanical Properties of Carbon Fiber Composites.

In this study, the kinetic parameters belonging to the cross-linking process of a modified epoxy resin, Aerotuf 275-34™, were investigated. Resin curing kinetics are crucial to understanding the structure-property-processing relationship for manufacturing high-performance carbon-fiber-reinforced polymer composites (CFRPCs). The parameters were obtained using differential scanning calorimetry (DSC) measurements and the Flynn-Wall-Ozawa, Kissinger, Borchardt-Daniels, and Friedman approaches. The DSC thermograms show two exothermic peaks that were deconvoluted as two separate reactions that follow autocatalytic models. Furthermore, the mechanical properties of produced carbon fiber/Aerotuf 275-34™ laminates using thermosetting polymers such as epoxies, phenolics, and cyanate esters were evaluated as a function of the conversion degree, and a close correlation was found between the degree of curing and the ultimate tensile strength (UTS). We found that when the composite material is cured at 160 °C for 15 min, it reaches a conversion degree of 0.97 and a UTS value that accounts for 95% of the maximum value obtained at 200 °C (180 MPa). Thus, the application of such processing conditions could be enough to achieve good mechanical properties of the composite laminates. These results suggest the possibility for the development of strategies towards manufacturing high-performance materials based on the modified epoxy resin (Aerotuf 275-34™) through the curing process.

A comparative evaluation of the sealing ability of two calcium silicate based sealers and a resin epoxy-based sealer through scanning electron microscopy and bond strength: an in vitro study

Aim: this study aimed to compare the sealing ability of two types of commercially available calcium silicate bioceramic based root canal sealers and a resin based root canal sealer. Methods: Twenty one single-rooted teeth were used, samples (n= 21) were randomly divided into three groups according to the sealer used (group A; ADSEAL, group B; Wellroot, group C; Ceraseal). Roots were then cleaved longitudinally in the labiolingual direction; all samples were then sectioned at three, six, and nine mm from the root tip. The penetration of sealers into the dentinal tubules was examined at 1000x with a scanning electron microscope. Data were tested for normality using Shapiro Wilk test. ANOVA test was used for analyzing normally distributed data followed by Bonferroni post hoc test for pair-wise comparison. Significance level p≤0.001. Results: groups B and C showed better sealing ability than group A in all the three sections. The coronal section showed higher sealing ability than the middle section followed by the apical section in the three tested groups. Conclusion: it can be concluded that both calcium silicate-based sealers had better sealing ability and higher bond strength than the resin epoxy- based sealer

Synthesis and characterization of a new methacrylate monomer derived from the cashew nut shell liquid (CNSL) and its effect on dentinal tubular occlusion.

OBJECTIVE: The aim of this study was to synthesize, to characterize and to evaluate the effects on tubular occlusion of new monomer derived from cashew nut shell liquid (CNSL), also studying the effects of acid challenge (AC) on dentin surfaces treated with desensitizers. METHODS: The intermediary cardanol-epoxy (CNE) was synthesized through epoxidation of CNSL, followed by synthesis of cardanol-methacrylate-epoxy (CNME) through methacryloyl chloride esterification. Products were purified through chromatography column and characterized by Fourier transform infrared spectrometry and nuclear magnetic resonance. Resinous dentin desensitizers were formulated containing either unsaturated cardanol (CNU), CNE or CNME. Dentin disks were divided into seven groups: SL - Smear-layer, EDTA - EDTA-treated only, GLUMA - Gluma Desensitizer, OCB - One Coat Bond, CNU - CNU desensitizer, CNE - CNE desensitizer and CNME - CNME desensitizer. Dentinal fluid rate (DFF) was obtained using a Flodec equipment and tubular occlusion employing a scanning electron microscope (SEM), before and after AC. Data of DFF were submitted to two-way ANOVA and Tukey's test (p<0.05). RESULTS: GLUMA showed the lower reduction in DFF when compared to the other products, which were statistically similar. Even after AC, CNME presented the most homogenous and occluded surface, while CNE and CNU were partially removed, GLUMA was completely removed and OCB keep an occluded, but irregular surface. SIGNIFICANCE: CNME showed a great reduction of DFF and a homogenous occluded surface, suggesting that it may be a suitable and acid-resistant treatment option for dentine hypersensitivity.

Evaluation of the physicochemical properties of silicone- and epoxy resin-based root canal sealers

Abstract To assess the physicochemical properties of AH Plus, GuttaFlow 2, GuttaFlow BioSeal, and MM Seal, five samples of each root canal sealer were evaluated to determine their setting time (ST), dimensional change (DC), solubility (SL), flow (FL), and radiopacity (RD) according to American National Standards Institute/American Dental Association (ANSI/ADA) Specification 57. The distilled and deionized water obtained from the SL test were subjected to atomic absorption spectrometry to observe the presence of Ca2+, K+, and Na+ ions. Statistical analysis was performed by using one-way ANOVA and Tukey-Kramer tests (p < 0.05). The following results were obtained: ST (min) (AH Plus 463.6 ± 13.22; GuttaFlow 2 24.35 ± 2.78; GuttaFlow Bioseal 17.4 ± 0.55; MM Seal 47.60 ± 4.39), DC (%) (AH Plus 0.06 ± 0.12; GuttaFlow 2 −26.06 ± 1.24; GuttaFlow Bioseal 2.10 ± 1.47; MM Seal 8.47 ± 2.41), SL (%) (AH Plus 0.41 ± 0.21; GuttaFlow 2 5.13 ± 4.11; GuttaFlow Bioseal 3.03 ± 1.05; MM Seal 0.94 ± 0.17), FL (mm) (AH Plus 36.42 ± 0.40; GuttaFlow 2 36.44 ± 0.05; GuttaFlow Bioseal 35.4 ± 0.03; MM Seal 52.75 ± 0.60), and RD (mmAl) (AH Plus 7.52 ± 1.59; GuttaFlow 2 6.85 ± 0.14; GuttaFlow Bioseal 7.02 ± 0.18; MM Seal 3.32 ± 0.90). ST, DC, SL, FL, and RD showed statistical differences among the root canal sealers (p < 0.05). As AH Plus showed the lowest DC and SL values (p < 0.05), the findings indicate that this sample is the only sealer conforming to ANSI/ADA standards.

Sealing ability of MTA, CPM, and MBPc as root-end filling materials: a bacterial leakage study

ABSTRACT Objectives To evaluate the sealing ability of three root-end filling materials (white MTA, CPM, and MBPc) using an Enterococcus faecalis leakage model. Material and Methods Seventy single-root extracted human teeth were instrumented and root-ends were resected to prepare 3 mm depth cavities. Root-end preparations were filled with white MTA, CPM, and MBPc cements. Enterococcus faecalis was coronally introduced and the apical portion was immersed in BHI culture medium with phenol red indicator. The bacterial leakage was monitored every 24 h for 4 weeks. The statistical analysis was performed using the Wilcoxon-Gehan test (p<0.05). Results All cements showed bacterial leakage after 24 hours, except for the negative control group. The MBPc showed significantly less bacterial leakage compared with the MTA group (p<0.05). No significant differences were found between the CPM and the other groups. Conclusions The epoxy resin-based cement MBPc had lower bacterial leakage compared with the calcium silicate-based cements MTA and CPM.

Efeitos do Bisfenol A (BPA) na infertilidade masculina e feminina revisão literária / Effects of bisphenol A (BPA) on male and female infertility a literature review

Bisphenol A (BPA) is found in polycarbonate plastics, epoxy resins and wastewater. Therefore, this compound readily comes into contact with humans. The objective of this work is to review the recent literature (2010 to 2014) on possible detrimental effects of BPA to human fertility and health in both sexes. The review indicated that BPA causes adverse infertility effects on men and women, besides posing environmental risks. We concluded that new public policy on its use and effects is needed.(AU)

O bisfenol A (BPA) encontra-se em plásticos policarbonatos, resinas epóxi e águas residuais. Portanto, esse composto tem contato com o ser humano. Para verificar sua possível ação prejudicial à saúde, o presente trabalho tem como objetivo analisar a literatura sobre seus efeitos na fertilidade em ambos os sexos. Após uma revisão da literatura presente em sites de artigos científicos, selecionando artigos recentes do ano de 2010 até 2014, o presente estudo indicou que o BPA causa efeitos adversos de infertilidade no homem e na mulher, além de acarretar riscos ao meio ambiente. Permitindo-se concluir que existe a necessidade de novas políticas públicas sobre seu uso e novos estudos sobre seus efeitos.(AU)

Efeitos do Bisfenol A (BPA) na infertilidade masculina e feminina revisão literária / Effects of bisphenol A (BPA) on male and female infertility a literature review

Bisphenol A (BPA) is found in polycarbonate plastics, epoxy resins and wastewater. Therefore, this compound readily comes into contact with humans. The objective of this work is to review the recent literature (2010 to 2014) on possible detrimental effects of BPA to human fertility and health in both sexes. The review indicated that BPA causes adverse infertility effects on men and women, besides posing environmental risks. We concluded that new public policy on its use and effects is needed.

O bisfenol A (BPA) encontra-se em plásticos policarbonatos, resinas epóxi e águas residuais. Portanto, esse composto tem contato com o ser humano. Para verificar sua possível ação prejudicial à saúde, o presente trabalho tem como objetivo analisar a literatura sobre seus efeitos na fertilidade em ambos os sexos. Após uma revisão da literatura presente em sites de artigos científicos, selecionando artigos recentes do ano de 2010 até 2014, o presente estudo indicou que o BPA causa efeitos adversos de infertilidade no homem e na mulher, além de acarretar riscos ao meio ambiente. Permitindo-se concluir que existe a necessidade de novas políticas públicas sobre seu uso e novos estudos sobre seus efeitos.

Bisphenol A: review on its use in the food packaging, exposure and toxicity / Bisfenol A: o uso em embalagens para alimentos, exposição e toxicidade - uma Revisão

Bisphenol A is an industrial compound produced in large scale around the world. This product is used for manufacturing the synthetic polymers, including epoxy resins, which are applied for varnishing the both internal and external parts of food cans, and also for producing the polycarbonate applied on baby bottles and bottles of water. Other less significant applications are the production of polyvinyl chloride (PVC), to manufacture the thermal paper, polyurethane, polyamide, flame retardant, and to prepare the dental sealants and resins. Bisphenol A is considered as an endocrine disruptor that interferes with the production, release, transport, metabolism, binding or elimination of natural hormones responsible for maintaining balance and regulation of development processes. Among the various routes of human exposure to bisphenol A, the dietary exposure is especially worrisome as it potentially reaches higher number of persons in the different age groups, besides, it may occur during long periods in low doses and without being detected. This review aimed at addressing the routes of exposure to bisphenol A, its toxicity and the legislations concerning their limits to ensure the human health integrity(AU)

O bisfenol A é um composto industrial produzido em larga escala em todo o mundo, sendo utilizado para produzir polímeros sintéticos, inclusive as resinas epóxi, que são empregadas no envernizamento interno e externo de latas de alimentos, e na produção de policarbonato com aplicações em mamadeiras e garrafões de água. Outras aplicações menos significativas são a produção de policloreto de vinila (PVC), manufatura de papel térmico, poliuretano, poliamida e de produto para retardamento de chama, bem como na preparação de selantes e resinas dentárias. O bisfenol A é considerado como disruptor endócrino que interfere na produção, liberação, transporte, metabolismo, ligação ou eliminação dos hormônios naturais, responsáveis pela manutenção do equilíbrio e regulação dos processos de desenvolvimento. Dentre as várias vias de exposição humana ao bisfenol A, a exposição alimentar é a mais preocupante por atingir potencialmente um maior número de pessoas, em diversas faixas etárias, e que pode ocorrer durante longos períodos em pequenas doses e sem serem detectadas. Na presente revisão foram abordadas as vias de exposição ao bisfenol A, sua toxicidade e as legislações quanto aos limites para garantir a saúde humana(AU)

Influence of root canal sealer on the radiographic appearance of filling voids in maxillary single-rooted teeth

OBJECTIVE: This study compared the influence of three epoxy resin-based sealers with distinct radiopacities on the observers' ability to detect root canal filling voids during radiographic analysis. MATERIAL AND METHODS: The root canals of 48 extracted maxillary canines were prepared and divided into three groups. Each group was laterally condensed with one sealer (AH Plus®, Acroseal® or a non-radiopaque sealer), and a longitudinal void was simulated in half of the specimens from each group (n=8). Buccolingual radiographs were obtained and randomly interpreted for voids by a radiologist and an endodontist in a blinded fashion. Teeth were cut and inspected under a microscope to confirm the position of void. Differences in sensitivity and specificity between groups and examiners were compared using the Fisher's Exact and McNemar tests, respectively (α=0.05). RESULTS: Significantly lower sensitivity levels (p<0.05) were observed in the coronal portion of fillings performed with both radiopaque sealers. Specificity values for Acroseal® were significantly higher (p<0.05) in the coronal and apical portions of fillings. CONCLUSIONS: The type of root canal sealer can affect the observers' ability to detect root canal filling voids during radiographic analysis of upper single-rooted teeth.

Influence of the casting material on the dimensional accuracy of dental dies

The purpose of this study was to evaluate the dimensional accuracy of different materials used in the confection of dies. Two stainless steel standard models were confected. One of the models, which was 2 mm larger than the other model, was used to provide a uniform relief for the two-step putty-wash impression technique. Thirty impressions were obtained using a polyvinyl siloxane impression material and randomly divided into three groups (n = 10) according to the type of casting material: type IV dental stone, commercially available epoxy resin (Tri-Epoxy), and industrial epoxy resin (Sikadur). After the setting/polymerization of the casting material, the dimensional stability was measured in terms of the height, diameter of the base and diameter of the top from the obtained dies and from the standard metal model using a profile projector. Results were analyzed by ANOVA and Dunnet test (α = 0.05). In the height values, no significant difference was observed between the groups, except for Sikadur casts, which showed lower mean values. The Tri-Epoxi group showed statistically lower mean base diameter values, compared with the other groups, and both epoxy resin groups showed statistically lower mean top diameter values, compared with that for the type IV dental stone group. We concluded that type IV gypsum and the commercially available epoxy resin showed similar behavior in most areas. The industrial epoxy resin did not show the same characteristics, although the diameter of the base obtained with it was similar to that obtained with type IV dental stone.

Avaliação histopatológica do reparo apical e periapical em dentes de cães com vitalidade pulpar, após tratamento de canais radiculares utilizando dois cimentos obturadores à base de resina epóxica. Análise do pH e concentração de cálcio total / Histopathological evaluation of the apical and periapical repair of dog's teeth with vital pulp after biomechanic preparation and root canal fillings using resin-based sealers. Analysis of pH and calcium concentration

O objetivo do presente estudo foi o de avaliar comparativamente, dois cimentos obturadores de canal radicular à base de resina epóxica, AH Plus e Sealer Plus, através de duas diferentes metodologias. 1. Teste in vivo - Avaliação histopatológica em dentes de cães. Foram utilizados 36 canais radiculares de dentes pré-molares superiores e inferiores de 2 cães, com vitalidade pulpar, os quais, após o preparo biomecânico coadjuvado pela irrigação/aspiração e inundação com solução de hipoclorito de sódio a 1% (Líquido de Dakin), foram obturados pela técnica clássica complementada pela condensação lateral ativa, empregando os cimentos Sealer Plus (Grupo I) e AH Plus (Grupo II). Decorridos 90 dias após a obturação, os animais foram sacrificados por sobredose anestésica, as maxilas e mandíbulas removidas e fixadas em formol a 10%, durante 48 horas. Após processamento histológico de rotina, os cortes foram corados pela hematoxilina e eosina, pelo tricrômico de Mallory e Brown e Brenn. A análise histopatológica evidenciou que o cimento AH Plus, quanto à compatibilidade biológica, mostrou-se superior ao Sealer Plus, sendo o cimento que melhor permitiu a deposição de tecido mineralizado à nível apical, oferecendo um selamento quase completo na maioria dos casos, com infiltrado inflamatório ausente e quando presente era suave no tecido intersticial e/ou junto ao material obturador, assim como na região periapical. Já, com o cimento Sealer Plus, ocorreu predominantemente, selamento parcial, porém sempre acompanhado de infiltrado inflamatório de grau suave, no tecido intersticial, porém, mais concentrado, junto ao cimento obturador. Quando o material obturador era observado na região periapical, o infiltrado inflamatório apresentava-se, classificado como de grau moderado, concentrado próximo ao material e com reabsorção óssea alveolar. 2. Teste in vitro - Análise química. Com o objetivo de analisar o pH e liberação de cálcio total, por períodos que variaram de 0 a 5 dias, os cimentos endodônticos AH Plus e Sealer Plus, foram manipulados de acordo com as instruções dos fabricantes, e confeccionados os corpos -deprova, os quais foram pesados separadamente e colocados em água destilada, mantendo-se constante a relação massa/volume. Com relação ao pH, o cimento AH Plus ofereceu, após a reação de presa, um pH de 6,0, e logo em seguida, apresentou uma variação, tornando-se constante após 24 horas e com um pH alcalino de 7,5. Já o Sealer Plus, apresentou um pH crescente, até o 5o dia (pH =10,54). Com relação à liberação de cálcio total, os resultados obtidos mostram que o cimento Sealer Plus liberou uma grande quantidade de cálcio total, aos 5 dias (14,89 ppm), por ser mais solúvel que o AH Plus, que apresentou aos 5 dias, menor liberação de cálcio (0,144 ppm)

The scope of the present study was to evaluate comparativily, two root canal resin ­ based sealers - AH Plus and Sealer Plus through two different methodologies. 1. In vivo study ­ Histopathological evaluation in teeth of dogs. 36 root canals of lower and upper bicuspide teeth of 2 dogs with vital pulp, which after biomechanic preparation utilizing sodium hypochloride solution at 1% (Milton solution) were filling by classical technique complemented by active lateral condensation, using Sealer Plus (Group I) and AH Plus (Group II). 90 days after treatment, the animals were sacrificed by overdose anesthetical. After histopathological processing of routine, the sections were stained with hematoxiline and eosine, Mallory Trichromic and Brown and Brenn. The histopathological analysis had evidenced that the AH Plus sealer shows more biological compatibility in relation to the Sealer Plus being the sealer that shows more good deposition of mineralized tissue to the apical level, offering an almost full apical sealing in the majority of the cases, with infiltrated inflammatory absent and when present was mild in the interstitial tissue and/or together to the material sealer, as well as in the periapical region. With the Sealer Plus, partial apical sealing occurred, however always followed by infiltrated inflammatory of mild degree in the intersticial tissue, however, more concentrated, together to the filling material when in the periapical region, the inflammatory infiltrated was presented, classified as of moderate degree. 2. In vitro study - With the objective to analyze pH and clearing of total calcium by periods that had varied from 0 to the 5 days, the filling materials. AH Plus and Sealer Plus had been manipulated according to the manufacturers instructions. Samples of each sealer were prepared, which had been weighed separately and placed in distilled water, remaining at constant relation of mass/volume. In relation to the pH, the AH Plus sealer offered, after the reaction, one pH of 6.0, and soon after that, presented a variation, becoming constant after 24 hours and with pH alkaline of 7.5. Already the Sealer Plus, presented pH increasing, until 5 days (pH = 10.54). In relation to the clearing of total calcium, the results show that the Sealer Plus liberated a great amount of total calcium until 5 days (14.89 ppm), being more soluble than AH Plus, that offers until 5 days, minor calcium clearing (0.144 ppm)