The Effect Of Poly(methyl Methacrylate) Surface Treatments On The Adhesion Of Silicone-based Resilient Denture Liners.

Different surface treatment protocols of poly(methyl methacrylate) have been proposed to improve the adhesion of silicone-based resilient denture liners to poly(methyl methacrylate) surfaces. The purpose of this study was to evaluate the effect of different poly(methyl methacrylate) surface treatments on the adhesion of silicone-based resilient denture liners. Poly(methyl methacrylate) specimens were prepared and divided into 4 treatment groups: no treatment (control), methyl methacrylate for 180 seconds, acetone for 30 seconds, and ethyl acetate for 60 seconds. Poly(methyl methacrylate) disks (30.0 × 5.0 mm; n = 10) were evaluated regarding surface roughness and surface free energy. To evaluate tensile bond strength, the resilient material was applied between 2 treated poly(methyl methacrylate) bars (60.0 × 5.0 × 5.0 mm; n = 20 for each group) to form a 2-mm-thick layer. Data were analyzed by 1-way ANOVA and the Tukey honestly significant difference tests (α = .05). A Pearson correlation test verified the influence of surface properties on tensile bond strength. Failure type was assessed, and the poly(methyl methacrylate) surface treatment modifications were visualized with scanning electron microscopy. The surface roughness was increased (P < .05) by methyl methacrylate treatment. For the acetone and ethyl acetate groups, the surface free energy decreased (P < .05). The tensile bond strength was higher for the methyl methacrylate and ethyl acetate groups (P < .05). No correlation was found regarding surface properties and tensile bond strength. Specimens treated with acetone and methyl methacrylate presented a cleaner surface, whereas the ethyl acetate treatment produced a porous topography. The methyl methacrylate and ethyl acetate surface treatment protocols improved the adhesion of a silicone-based resilient denture liner to poly(methyl methacrylate).

The use of a graphite-silicone rubber composite electrode in the determination of rutin in pharmaceutical formulation

The possibility of using a graphite silicone-rubber composite electrode (GSR) in a differential pulse voltammetric(DPV) procedure for rutin (vitamin P) determination is described. Cyclic voltammograms of rutin presented a reversible pair of oxidation/reduction peaks respectively at 0.411 and 0.390 V (vs. SCE) at the GSR surface in Britton-Robinson(B-R) buffer solution pH 4.0. In DPV after optimization of conditions, an oxidation peak at 0.370 V (vs. SCE) was used to quantitative determination of rutin in B-R buffer solution pH 4.0. In this case a linear dynamic range of 5.0×10-8 to 50.0×10-8 mol L-1 was observed with a detection limit of 1.8×10-8 mol L-1 for the analyte. Recoveries from 94 to 113% were observed. The electrode surface was renewed by polishing after each determination, with a repeatability of 1.09 ± 0.06 µA (n = 10) peak current. Rutin was determined in a pharmaceutical formulation using the proposed electrode and the results agreed with those from an official method within 95% confidence level.

Breast phantom with silicone implant for evaluation in conventional mammography

With the increased incidence of cancer and a similarly increased number of surgeries for insertion of silicone breast implants, it is necessary to assess the effect of such material within the breast tissue, particularly in mammography, because of the reduction in the power of breast cancer diagnosis. In this work, we introduce a breast phantom with silicone implants in order to evaluate the influence of the implant on the visibility of the main mammographic findings: fibers, microcalcifications and tumor masses. In this proposed phantom, the breast tissue was simulated using gel paraffin. In the optical density of phantom mammograms with implants, a reduction in breast tissue visibility was seen corresponding to 23% when compared to a phantom without silicone implants. This poor visibility was due to the X-ray beam scattering on silicone material; this effect produced a loss of visibility in the areas adjacent to the implant. It is expected that the proposed phantom model may be used as a device for the establishment of a technical standard for these types of procedures.

Use of an Inflatable Silicone Balloon Improves the Success Rate of Bladder Autoaugmentation at Long-Term Followup

Purpose: Most groups have reported disappointing results with autoaugmentation or detrusor myectomy for low capacity/compliance neuropathic bladders. Failure may be due to an ischemic diverticulum or mucosal shrinkage. We investigated whether a Silimed (R) silicone balloon placed in the bladder after autoaugmentation could prevent these problems, improving surgical results. Materials and Methods: We compared the results of standard bladder autoaugmentation in 12 children (group 1) with those in 10 (group 2) who underwent the same surgery using a bladder conformer. The conformer was a silicone balloon filled with saline that remained in the bladder for 2 weeks. All patients had a neuropathic bladder with poor capacity and compliance, resulting in urinary leakage between catheterizations. Preoperative and postoperative evaluation included a voiding diary, ultrasound, voiding cystourethrogram and urodynamics. Results: In group 1 only 1 patient became dry, 4 had little improvement in continence, 4 remained unchanged and 3 became worse. In group 2, 6 patients (60%) become continent without medication, 2 (20%) become continent with oxybutynin and 2 remained unchanged. Bladder capacity and compliance did not change significantly in group 1. However, in group 2 capacity changed from a mean of 140 to 240 ml and mean +/- SD compliance increased from 15.6 +/- 16.8 to 34.3 +/- 22.8 ml/cm H(2)O (p = 0.02). Conclusions: The inflatable balloon improved our long-term results of bladder auto-augmentation. A larger series may be necessary to confirm procedure efficacy and safety.

Characterization of Superparamagnetic Iron Oxide Coated with Silicone Used as Contrast Agent for Magnetic Resonance Image for the Gastrointestinal Tract

The present work is a report of the characterization of superparamagnetic iron oxide nanoparticles coated with silicone used as a contrast agent in magnetic resonance imaging of the gastrointestinal tract. The hydrodynamic size of the contrast agent is 281.2 rim, where it was determined by transmission electron microscopy and a Fe(3)O(4) crystalline structure was identified by X-ray diffraction, also confirmed by Mossbauer Spectroscopy. The blocking temperature of 190 K was determined from magnetic measurements based on the Zero Field Cooled and Field Cooled methods. The hysteresis loops were measured at different temperatures below and above the blocking temperature. Ferromagnetic resonance analysis indicated the superparamagnetic nature of the nanoparticles and a strong temperature dependence of the peak-to-peak linewidth Delta H(pp), giromagnetic factor g, number of spins N(S) and relaxation time T(2) were observed. This behavior can be attributed to an increase in the superexchange interaction.

Anal Incontinence Improvement After Silicone Injection May Be Related to Restoration of Sphincter Asymmetry

Background. This study aimed to evaluate manometric parameters that may explain improvement in anal incontinence using a silicone bulking agent. Methods. Incontinent patients having internal sphincter defects were prospectively selected and injected with a silicone bulking agent. Manometry and endoanal ultrasound were performed before and 3 months after injections. Twenty continent healthy volunteers were used only for manometric comparison. Results. Thirty-five patients (28 females; mean age 60.3 years) and 20 controls entered this study. Patients had lower resting and squeeze pressures compared with controls (P<.05). Length of the high-pressure zone increased from 1 to 1.7 cm postinjection (P=.002). Asymmetry index showed a significant change postinjection (P<.001). Conclusion. Despite considerable clinical improvement, no significant increase in manometric pressures was noted posttreatment. There was significant improvement in both high-pressure zone and asymmetry index, and these findings may explain the mechanism of action of the bulking agent injected.

Neuroprotective effects of oral lamotrigine administration on rabbit retinas after pars plana vitrectomy and silicone oil injection

Purpose: To investigate potential retinal neuroprotective effects of oral lamotrigine in rabbits after pars plana vitrectomy (PPV) and intravitreal silicone oil injection (SOI). Methods: Twelve New Zealand rabbits (weight, 2.0-2.5 kg) underwent PPV with SOI on the right eye. For 30 days postoperatively, 6 rabbits received a daily oral dose of lamotrigine (25 mg/kg), and 6 rabbits received a daily oral dose of water. The animals were killed 30 days after surgery. All retinas were processed histologically, immunostained using glial fibrillary acidic protein (GFAP), and analyzed by fluorescence microscopy. Retina sections from all groups were analyzed by TUNEL for the presence of apoptosis and stained with hematoxylin-eosin for morphologic analysis and retina cell density measurements in each layer using a Zeiss Axiophot microscope and KS 400 software. Results: Retinas from water-operated eyes showed a significant decrease in cell density associated with cell death compared with retinas from water-control eyes; cell density was reduced by 56% in the outer nuclear layer (ONL), 49% in the inner nuclear layer (INL), and 64% in the ganglion cell layer (GCL). Lamotrigine-operated retinas showed a reduction in cell death when compared with water-operated retinas; cell death was reduced by 52% in the ONL, 25% in the INL, and 56% in the GCL. Water-operated retinas showed TUNEL-positive cells and GFAP immunofluorescence throughout Muller cell processes; lamotrigine-operated retinas showed no TUNEL-positive cells and decreased GFAP staining when compared with water-operated retinas. Conclusions: PPV with SOI was associated with apoptosis of retinal cells and activation of glial cells in rabbit eyes. Oral lamotrigine administration provided protection against these effects.

Silicone implant for chin augmentation mimicking a low-grade liposarcoma

The silicone implant has been widely used in facial aesthetic surgery for chin augmentation. A case of a 71-year-old woman with a lesion in the anterior mandibular region detected by radiographies and suggestive of benign soft tissue tumor is presented. The patient denied previous surgical intervention in the mental area. A biopsy was performed and initially interpreted as low-grade liposarcoma. After an immunohistochemistry study showing CD-68-positive cells and complementary information regarding a silicone implant for chin augmentation, the definitive diagnosis was silicone granuloma. This case reinforces that silicone implant in the mandibular region can be misdiagnosed as malignant tumor and the correct diagnosis is heavily dependent on close collaboration between clinician and pathologist in order to avoid unnecessary surgical intervention. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: e21-e23)

Probing the effect of vehicles on topical delivery: Understanding the basic relationship between solvent and solute penetration using silicone membranes

Purpose. In the present study we examined the relationship between solvent uptake into a model membrane (silicone) with the physical properties of the solvents (e.g., solubility parameter, melting point, molecular weight) and its potential predictability. We then assessed the subsequent topical penetration and retention kinetics of hydrocortisone from various solvents to define whether modifications to either solute diffusivity or partitioning were dominant in increasing permeability through solvent-modified membranes. Methods. Membrane sorption of solvents was determined from weight differences following immersion in individual solvents, corrected for differences in density. Permeability and retention kinetics of H-3-hydrocortisone, applied as saturated solutions in the various solvents, were determined over 48 h in horizontal Franz-type glass diffusion cells. Results. Solvent sorption into the membrane could be related to differences in solubility parameters, MW and hydrogen bonding (r(2) = 0.76). The actual and predicted volume of solvent sorbed into the membrane was also found to be linearly related to Log hydrocortisone flux, with changes in both diffusivity and partitioning of hydrocortisone observed for the different solvent vehicles. Conclusions. A simple structure-based predictive model can be applied to the sorption of solvents into silicone membranes. Changes in solute diffusivity and partitioning appeared to contribute to the increased hydrocortisone flux observed with the various solvent vehicles. The application of this predictive model to the more complex skin membrane remains to be determined.

Electrorheological characterization of dispersions in silicone oil of encapsulated liquid crystal 4-n-penthyl-4 '-cyanobiphenyl in polyvinyl alcohol and in silica

The electrorheological (ER) effect is known as the change in the apparent viscosity upon the application of an external electric field perpendicular to the flow direction. In this work we present the electrorheological behaviour of suspensions in silicone oil of two different dispersed phases: foams of liquid crystal 4-n-penthyl-4'-cyanobiphenyl (5CB) encapsulated in polyvinyl alcohol (PVA) and nano/microspheres of 5CB encapsulated in silica. We will present the viscosity curves under the application of an electric field ranging between 0 and 3 kV mm(-1). The ER effect was observed for the suspensions of 5CB/PVA but not in the case of 5CB/silica. For the case of the suspensions of 5CB/PVA, the effect of the viscosity of the continuum phase and the concentration of the dispersed phase was analysed, showing that the enhancement of the viscosity of the suspension increases with the concentration, as expected, however the continuum phase viscosity has no significant effect, at least in the investigated viscosity range.

Utilização do tubo em "T" de silicone para tratamento de um caso de leishmaniose tegumentar americana com traqueomalácia

Trata-se do relato de caso de leishmaniose tegumentar americana, no qual houve ocorrência de traqueomalâcia e insuficiência respiratória. A natureza da enfermidade, o estado geral do paciente e a longa extensão do segmento traqueal comprometido tornaram inviável a realização de ressecção e anastomose. Optou-se pelo emprego de tubo em "T" de silicone, que se mostrou útil, motivando divulgação dó procedimento.

Silicone moulding for pressure sore debridement.

The radicality of wound debridement is an important feature of the surgical treatment of pressure sores. Several methods such as injection of methylene blue or hydrogen peroxide have been proposed to facilitate and optimise the surgical debridement technique, but none of them proved to be sufficient. We present an innovative modification of the pseudo-tumour technique consisting in the injection of fluid silicone. Vulcanisation of the silicone leads to pressure-sore moulding, permitting a more radical and sterile excision. In a series of 10 paraplegic patients presenting with ischial pressure sores, silicone moulding was used to facilitate debridement. Radical en bloc debridement was achieved in all patients. After a minimal follow-up of 2 years, no complications and recurrences occurred. A three-dimensional (3D) analysis of the silicone prints objectified the pyramidal shape of ischial pressure sores. Our study showed that complete resection without capsular lesion can be easily achieved. Further, it allows the surgeon to analyse the shape and size of the resected defect, which might be helpful to select the appropriate defect coverage technique.

Artificial Feeding of Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae) through Silicone Membrane

An artificial feeding system was used where citrated bovine blood was offerred to male and female Amblyomma cajennense. Vestiges of blood, sweat, hair and exfoliated skin were used as phago-stimulants placed on the surface of the silicone membrane. The ticks were collected, as engorged nymphs, from naturally infested equines, with the ecdysis occurring in the laboratory. Four hundred ticks were used, 50% being female, at three to four weeks post-ecdysis. Vestiges of blood on the silicone membrane were the most efficient phago-stimulant and the association of vestiges of blood and sweat residue smears yielded better results compared to the other phago-stimulants used

Desenvolvimento de Rhodnius pictipes Stal, 1872 alimentado através de membrana de silicone e em camundongos (Hemiptera, Reduviidae, Triatominae)

Rhodnius pictipes (Hemiptera, Reduviidae) from Serra Norte, State of Pará, Brazil, aclimatized in an insectary at the Laboratório Nacional e Internacional de Referência em Taxonomia de Triatomíneos, Departamento de Entomologia, Instituto Oswaldo Cruz, were fed through a silicone membrane. In order to know the viability and the efficiency of this membrane compared with insects fed on mice, the number of bloodmeals taken, period of development of the five nymphal instars, longevity of adults, average amount of blood intake in each meal and percent of mortality were observed. A total of 310 insects, were used, comprising 50 nymphs of each instar, as well as 30 male and 30 female adults. Insects fed artificially had reduced minimal and maximal periods of development than the group fed on mice. The largest relative increase of body weight was observed in the 2nd instar followed by the 1st, and the amount of blood ingested increased during the development, to the 5th instar for both groups. There were no significant differences between the groups fed artificially and in vivo according to Tukey's test for p>0.05. The percent of mortality in the 1st instar was 18% for artificially fed and 16% for the group fed on mice; these percentages decreased as insects developed until the 4th instar, without mortality, returning to increase in the 5th instar. R. pictipes was shown to be easily adaptable to artificial feeding, and could be considered as an important and viable experimental model.