Change in the geometry of positive- and negative-powered soft contact lenses during wear.

Contact lens wear causes mutual interactions between the ocular surface and the lens, which may affect comfort as well as vision. The aim of this study was to examine deformations in modern positive- and negative-powered silicone hydrogel soft contact lenses (SiH SCLs) after 7 days of continuous wear. This pre-post interventional study included 64 eyes: 42 eyes with myopia of -3.00 D and 22 eyes with hyperopia of +3.00 D. All patients underwent general ophthalmic examination, corneal topography/tomography, total corneal and epithelial thickness mapping, and specular microscopy before and after the wearing period. SiH SCLs made of senofilcon A were worn continuously for 7 days on all eligible eyes. The geometry of the new and used lenses was measured 3 to 6 minutes after removal in two perpendicular planes using a custom-made swept source optical coherence tomography (SS-OCT) system for in vitro measurements. The anterior and posterior radii of curvature decreased in -3.00 D lenses in two perpendicular planes. This effect correlated significantly with average keratometry of the cornea. Sagittal lens height was lower in +3.00 D lens after wear, which correlated moderately with the corneal sagittal height. A significant decrease in central corneal epithelial thickness was observed after wearing +3.0 D lenses. In conclusion, SiH SCLs made of senofilcon A undergo minor deformations after 7-day continuous wear. Geometry modifications are different for -3.00 D and +3.00 D lenses, and they imitate the shape of the anterior eye surface. These geometric changes are accompanied by a decrease in the central thickness of corneal epithelium after +3.00 D lens wear.

Effectiveness of silver alloy-coated silicone urinary catheters in patients with acute traumatic cervical spinal cord injury: Results of a quality improvement initiative.

Patients with acute traumatic cervical spinal cord injury (ATCSCI) have an increased risk of catheter-associated urinary tract infection (CAUTI). The effectiveness of silver alloy-coated silicone urinary catheters (SACC) in preventing CAUTI in ATCSCI is unknown and was the objective of this study. We performed a quality improvement initiative in an attempt to reduce CAUTI in patients undergoing spine surgery at a single quaternary center. Prior to July 2015, all patients received a latex indwelling catheter (LIC). All patients with ATCSCI with limited hand function (AIS A,B, or C) received a SACC. Incidence of CAUTI, microbiology, duration of infection, antibiotic susceptibility, and catheter-associated adverse events were recorded prospectively. We studied 3081 consecutive patients over the three years, of whom 302 (9.8%) had ATCSCI; 63% of ATCSCI patients were ASIA Impairment Scale (AIS) A or B. The overall rate of CAUTI was 19% (585/3081), and was 38% (116/302) in patients with ATCSCI. Of 178 ATCSCI patients with LIC, 100 (56%) developed a CAUTI compared with 28 of 124 (23%) patients with SACC (p < 0.05). Poly-microbial and gram-positive infection was more common in LIC than in SACC (p < 0.05). Median duration of infection was 9 days in SACC group and 12 days in LIC group (p = 0.08). Resistance to trimethoprim (p < 0.001) and ciprofloxacin (p < 0.05) were more common in LIC group. There was no difference in catheter-associated adverse events or length of stay between the groups. This quality improvement initiative illustrates the effectiveness of antiseptic silver alloy-coated silicone urinary catheters in patients with ATCSCI. In our population, the use of SACC reduces the incidence and the complexity of CAUTI.

The utility of 3D-printed airway stents to improve treatment strategies for central airway obstructions.

Airway stents are commonly used in the management of patients suffering from central airway obstruction (CAO). CAO may occur directly from airway strictures, obstructing airway cancers, airway fistulas or tracheobronchomalacia, resulting from the weakening and dynamic collapse of the airway wall. Current airway stents are constructed from biocompatible medical-grade silicone or from a nickel-titanium (nitinol) alloy with fixed geometry. The stents are inserted via the mouth during a bronchoscopic procedure. Existing stents have many shortcomings including the development of obstructing granulation tissue in the weeks and months following placement, mucous build up within the stent, and cough. Furthermore, airway stents are expensive and, if improperly sized for a given airway, may be easily dislodged (stent migration). Currently, in Australia, it is estimated that approximately 12,000 patients will develop CAO annually, many of whom will require airway stenting intervention. Of all stenting procedures, the rate of failure is currently reported to be at 22%. With a growing incidence of lung cancer prevalence globally, the need for updating airway stent technology is now greater than ever and personalizing stents using 3D-printing technology may offer the best chance of addressing many of the current limitations in stent design. This review article will assess what represents the gold standard in stent manufacture with regards to treatment of tracheobronchial CAO, the challenges of current airway stents, and outlines the necessity and challenges of incorporating 3D-printing technology into personalizing airway stents today.

Developing High Performance GaP/Si Heterojunction Solar Cells.

To improve the efficiency of Si-based solar cells beyond their Shockley-Queisser limit, the optimal path is to integrate them with III-V-based solar cells. In this work, we present high performance GaP/Si heterojunction solar cells with a high Si minority-carrier lifetime and high crystal quality of epitaxial GaP layers. It is shown that by applying phosphorus (P)-diffusion layers into the Si substrate and a SiNx layer, the Si minority-carrier lifetime can be well-maintained during the GaP growth in the molecular beam epitaxy (MBE). By controlling the growth conditions, the high crystal quality of GaP was grown on the P-rich Si surface. The film quality is characterized by atomic force microscopy and high-resolution x-ray diffraction. In addition, MoOx was implemented as a hole-selective contact that led to a significant increase in the short-circuit current density. The achieved high device performance of the GaP/Si heterojunction solar cells establishes a path for further enhancement of the performance of Si-based photovoltaic devices.

Mechanical fatigue resistance of an implantable branched lead system for a distributed set of longitudinal intrafascicular electrodes.

OBJECTIVE: A neural interface system has been developed that consists of an implantable stimulator/recorder can with a 15-electrode lead that trifurcates into three bundles of five individual wire longitudinal intrafascicular electrodes. This work evaluated the mechanical fatigue resistance of the branched lead and distributed electrode system under conditions designed to mimic anticipated strain profiles that would be observed after implantation in the human upper arm. APPROACH: Custom test setups and procedures were developed to apply linear or angular strain at four critical stress riser points on the lead and electrode system. Each test was performed to evaluate fatigue under a high repetition/low amplitude paradigm designed to test the effects of arm movement on the leads during activities such as walking, or under a low repetition/high amplitude paradigm designed to test the effects of more strenuous upper arm activities. The tests were performed on representative samples of the implantable lead system for human use. The specimens were fabricated using procedures equivalent to those that will be used during production of human-use implants. Electrical and visual inspections of all test specimens were performed before and after the testing procedures to assess lead integrity. MAIN RESULTS: Measurements obtained before and after applying repetitive strain indicated that all test specimens retained electrical continuity and that electrical impedance remained well below pre-specified thresholds for detection of breakage. Visual inspection under a microscope at 10× magnification did not reveal any signs of damage to the wires or silicone sheathing at the stress riser points. SIGNIFICANCE: These results demonstrate that the branched lead of this implantable neural interface system has sufficient mechanical fatigue resistance to withstand strain profiles anticipated when the system is implanted in an arm. The novel test setups and paradigms may be useful in testing other lead systems.

Mamoplastia redutora com utilização de implantes de mamários / Reduction mammoplasty with the use of breast implants

Introdução: A evolução das técnicas de mamoplastia redutora contribuiu para tornar a cirurgia mais segura e, portanto, mais aceita pela comunidade médica. Contudo, em algumas pacientes, a estética final permanecia insatisfatória, principalmente, por resultar em mamas flácidas e sem projeção. Para alcançar melhores resultados, iniciou-se o uso do implante de mama em conjunto com a mamoplastia redutora. Ao agregar o melhor das duas técnicas, é possível obter bons resultados e a satisfação do paciente. O objetivo deste estudo é avaliar o resultado das cirurgias de mamoplastia redutora com a inclusão de implantes de silicone. Métodos: Para o desenvolvimento deste trabalho, foram selecionadas 15 pacientes, do sexo feminino, com idade entre 26 a 62 anos. Todas foram submetidas à mamoplastia redutora com inclusão imediata de implante mamário. Parâmetros, como assimetria da base mamária e volume da ressecção, foram avaliados. Após o sexto mês de pós-operatório, as pacientes responderam um questionário sobre o grau de satisfação do resultado final da cirurgia, que variou de insatisfeita, satisfeita e muito satisfeita. Resultados: Apesar de apresentar um paradoxo - retirar tecido mamário para colocar um implante de silicone -, a cirurgia para redução mamária com utilização implante consegue alcançar, com êxito, o objetivo de posicionar, adequadamente, as estruturas mamárias e de proporcionar maior durabilidade do resultado tanto na consistência quanto na projeção do cone mamário. Conclusão: Pode-se concluir que a técnica apresenta bons resultados na medida em que aumenta a durabilidade do resultado cirúrgico e a satisfação das pacientes.

Introduction: Advances in reduction mammoplasty techniques have contributed to make surgery safer and more acceptable to the medical community. However, in some patients, the aesthetic outcome remains unsatisfactory, mainly because of flaccid breasts and lack of projection. To achieve optimal results, the use of breast implants in conjunction with reduction mammoplasty was initiated. By combining the best of both techniques, it is possible to obtain good results and patient satisfaction. The objective of this study is to evaluate the results of reduction mammoplasty with insertion of silicone implants. Methods: For this study, 15 female patients aged 26 to 62 years were selected. All underwent reduction mammoplasty with immediate insertion of breast implants. Parameters such as asymmetry of the breast base and resection volume were evaluated. After the sixth postoperative month, patients reported their degree of satisfaction with the final surgery result, as dissatisfied, satisfied, or very satisfied. Results: Although presenting a paradox-removing breast tissue to place a silicone implant-breast reduction surgery with the use of implants can successfully achieve the aim of proper positioning of breast structures and providing higher durability of results, both in breast consistency and in the projection of the breast cone. Conclusions: The technique achieved good results by increasing the durability of the surgical result and patient satisfaction.

Measuring the modulus of silicone hydrogel contact lenses.

PURPOSE: The purpose of this study is to demonstrate a novel method for measuring the modulus of contact lenses in their as-received, variable-thickness form and to determine whether modulus varies with location within commercial lenses and whether it is dependent on lens geometry and temperature. METHODS: The thickness profiles of lenses having powers from -8 diopters (D) to +4 D were measured using a Rehder electronic thickness gauge. Strip-shaped specimens having a width of 5.5 mm were then cut from the lenses. Graphite particles were sprinkled on the specimen surface so that its motions could be tracked using digital image-correlation techniques. The specimens were mounted in a BioTester test system using BioRakes (rather than clamps) and stretched uniaxially until all parts of the lens between the attachment points had elongated by at least 10%. This procedure allowed local modulus values to be determined at 110 locations over the surface of each lens and any property variations within the lenses to be characterized. Tests were performed at 5, 23, and 37°C. RESULTS: Material modulus was found to be essentially constant within any given lens and was independent of the optical power of the lens. Young's Modulus values ranged from 0.3 to 1.9 MPa, depending on the lens manufacturer and product, and some lens materials showed a decrease in modulus with temperature. For the materials tested, those with lower water content had a tendency to exhibit higher moduli. CONCLUSIONS: Testing of the kind reported here is important for assessing the efficacy of current and proposed contact lens materials and designs, especially if such designs make use of variable properties to enhance function or fit.

Randomized controlled clinical study on the accuracy of two-stage putty-and-wash impression materials.

PURPOSE: The accuracy of dental impression taking is one major factor influencing the fit of crowns and fixed partial dentures. The aim of this study was to determine the accuracy of three-dimensional (3-D) tooth surface and subgingival tooth surface reproduction using three different silicone materials and the two-stage putty-and-wash technique. MATERIALS AND METHODS: From 24 probands, three impressions each were taken with Express STD Putty/Wash (3M ESPE), Optosil/Xantopren L (Heraeus Kulzer), and an experimental ultralight body/putty material (3M ESPE) in a randomized order. The preliminary impression was cut according to established procedures for the two-stage putty-and-wash technique. Master casts were manufactured with a standardized procedure and optically digitized. The 3-D accuracy was analyzed with a computer-aided procedure. The Express STD putty-and-wash impressions were used as a reference. Linear models were used for the statistical analysis. RESULTS: Mean deviations of 27.0 microm and -23.6 microm were found for Optosil/Xantopren L and 26.5 microm and -22.6 microm for the experimental material when analyzing 3-D surface reproduction. The tooth surface (buccal/oral) significantly influenced the accuracy of the surface reproduction. Optosil/Xantopren L showed a more complete reproduction of the subgingival tooth surface than either the experimental or reference materials. CONCLUSION: The accuracy of the 3-D tooth surface reproduction as well as the reproduction of the subgingival tooth surface was not favorably influenced when the ultralight wash material was used with established cutting procedures for the preliminary impression.

Efficacy of a polyurethane dressing versus a soft silicone sheet on hypertrophic scars.

OBJECTIVE: To compare the efficacy and safety of a polyurethane dressing with a silicone sheet in the treatment of hypertrophic scars. METHOD: Sixty patients participated in this intra-individual 12-week clinical trial. Each scar was divided into two areas, to which the polyurethane dressing and the silicone sheet were randomly allocated. The primary outcome measure was the percentage change in the overall scar index (SI) between baseline and week 12. Secondary outcome measures included changes in skin redness, objectively measured by chromametry, and patients views on the aesthetic outcome of treatment. RESULTS: Both therapies achieved favourable results for all of the above outcome measures. Results were comparable for the primary outcome measure: 29.4% versus 33.7% for the silicone sheet and polyurethane product respectively. The decrease in the overall SI was significantly more pronounced for the polyurethane product after week 4 (5.6% versus 15.8% for the silicone sheet; p<0.0001) and week 8 (20.2% versus 27.1%; p=0.012). CONCLUSION: Both regimens were associated with a significant reduction in the clinical signs of hypertrophic scars over 12 weeks of treatment. The polyurethane dressing demonstrated a significantly more pronounced reduction in severity of these clinical signs after four and eight weeks of treatment and was better tolerated than the silicone sheet. l DECLARATION OF INTEREST: This study was funded by Beiersdorf AG. proDERM is an independent research company, and none of the authors have an interest in the sponsors commercial activities.

The effect of the environment on the mechanical properties of medical grade silicones.

Silicone spacers have been in use as replacement joints in the human hand for over 30 years. Since they were first used there has been a number of designs all of which have had problems with fracture. This may be due to a defect in the material caused during implantation, or by bony intrusions within the arthritic hand after implantation. The aim of this research was to investigate the effect of the environment on the mechanical properties of medical grade silicones used for human implantation. The materials were subjected to static tensile testing after various forms of ageing. The environmental conditions included temperatures of 37 and 80 degrees C and the environments of Ringer's solution, distilled water, and air. The environmental conditions employed resulted in reduced mechanical strength with ageing time of the silicones. This research supports the view that failure of silicone implants in the hand could be partly attributed to the effects of environmental ageing of the material.

Accuracy of stone casts obtained by different impression materials.

Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a partially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p < or = .05), presenting smaller discrepancies. However, condensation silicone was similar (p > or = .05) to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials.

Accuracy of stone casts obtained by different impression materials

Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a partially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p < .05), presenting smaller discrepancies. However, condensation silicone was similar (p > .05) to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials.

Interferência na reação de polimerização das siliconas de adição pelo contato direto ou indireto com luvas de látex / The interference in polimerization reaction of adittion silicones through direct or indirect contact with latex gloves

O objetivo deste estudo foi determinar quais marcas comerciais de luvas de látex apresentavam algum tipo de reação química impeditiva da polimerização completa das siliconas de adição (pasta densa e leve) pelo contato direto e indireto. Foi avalida a reação, de viscosidade leve e pesada, em contato direto com dez marcas comerciais de luvas de látex nacionais. A maior parte das luvas de látex testadas inibiu a polimerização da silicona de adição. Isso comprova que as siliconas de adição não devem entrar em contato com luvas de látex durante os procedimentos clínicos para evitar que sofram alterações das suas propriedades físico-químicas

A study to compare a new self-adherent soft silicone dressing with a self-adherent polymer dressing in stage II pressure ulcers.

Pressure ulcers are common among elderly nursing home residents. To be effective in managing these wounds, a dressing should maintain a moist environment, facilitate healing, absorb exudate, remain in place for a number of days, and prevent trauma to the surrounding skin. An 8-week, open, randomized, multicenter, controlled study was conducted to compare the effects of a new self-adherent soft silicone dressing and a self-adherent hydropolymer dressing on Stage II pressure ulcers. Thirty-eight (38) residents participated in the study. Eighteen residents (mean age 83.8 years, range 74.9 to 95.1 years) were randomized to wound management with a soft silicone dressing, and the ulcers of 20 residents (mean age 82.5 years, range 66.4 to 91.9 years) were managed with a hydropolymer dressing. Wound healing, wound and surrounding skin characteristics, and ease of dressing removal were measured and documented. During the study, eight (44%) ulcers in the soft silicone group and 10 (50%) in the hydropolymer dressing group healed. Both dressings were changed approximately once a week and no differences in signs of inflammation, amount of exudate and odor, or incidence of leakage were observed. Damage to the surrounding skin, maceration, and dressing removal difficulties were less common with the soft silicone dressing. Differences in tissue damage between the two dressings were significant during weeks 1, 2, and 3 (P < 0.05). Studies with a larger sample size are needed to confirm these findings.

Variability in the properties of silicone gel breast implants.

Several generations of silicone gel breast implants have been produced by implant manufacturers. The primary material usually viewed as the base material in the manufacture of implants is polydimethylsiloxane. Polymeric reactions are notorious for their variability and nonuniformity. The elastomer used in different types of implants can have vastly different properties. Furthermore, the material properties associated with a particular type of implant can vary considerably from one lot to the next. Considering the various designs, styles, and manufacturing techniques associated with silicone gel implants, knowledge of the original properties of the implants before implantation is important in determining the effects of aging in vivo. This study was conducted to investigate differences in key mechanical and chemical properties of silicone gel breast implant materials. The two types of implants chosen for analysis were Silastic I and Silastic II control implants. Material property data were determined for both types of controls and significant differences were found in their values. Lot-to-lot variability was also investigated and found to be significant.

Prospective comparative evaluation of stapled versus transected silastic ring gastric bypass: 6-year follow-up.

BACKGROUND: The effect of transecting vs. stapling the stomach in continuity in the banded gastric bypass (GBP) operation was studied. METHOD: 50 patients, 25 in each group, were enrolled into a prospective study to determine if transecting the stomach vs. stapling it in continuity in performing GBP for obesity decreases the incidence of gastro-gastric fistula formation without increased morbidity. RESULTS: The patient profiles in the 2 groups were very similar. The peri-operative complications included 1 splenic capsular injury in each group, controlled without a splenectomy. There was 1 anastomotic leak in the stapled and 1 bleeding from the cut edge of the bypassed stomach in the transected group, both requiring re-operations in the immediate postoperative period. There was no peri-operative mortality. The percent follow-up after 6 years was 80% and 88% in the stapled and transected groups respectively. The incidence of late complications of solid food intolerance, ventral incisional hernia, cholelithiasis and small bowel obstruction was similar in both groups. There were 8 gastro-gastric fistulas in the stapled group and 1 in the transected group. The reduction in body mass index and percent excess weight loss (66%) were similar in both groups. CONCLUSION: The incidence of gastro-gastric fistula may be reduced in GBP procedures by transecting the stomach as opposed to stapling it in continuity, without an increase in morbidity or mortality or any loss in the effectiveness of the operation.

Biomechanical performance of silicone and latex external condom catheters.

Standard in vivo biomechanical performance tests and a pilot clinical study of latex external condom catheters (ECCs) and silicone ECCs demonstrated the superior performance of the silicone ECC over that of the latex ECC. The silicone ECC has a self-adhesive that binds more securely to human skin than the self-adhesive of latex ECC. In addition, the moisture vapor transmission through silicone is significantly greater than through latex. The aggressive self-adhesive of the silicone ECC significantly reduced ECC catheter pop-off compared to that of latex ECC. Silicone ECC removal can be facilitated by the application of a warm, wet cloth to the exterior surface of the silicone ECC, which significantly reduces its self-adhesive force. Constant, gentle traction is then applied to the silicone catheter outlet end to achieve atraumatic silicone ECC removal. On the basis of the results of these standardized tests and pilot study, the silicone ECC is recommended for incontinent men without obstructive uropathy.