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At least 397 records · Page 22Linked to original sources
PubMed1999

Wettability of silicone rubber maxillofacial prosthetic materials.

STATEMENT OF PROBLEM: Maxillofacial prosthetic materials that contact skin or mucosa should have good wettability. A material that is easily wetted will form a superior lubricating layer between the supporting tissues and, thus, reduce friction and patient discomfort. The surface energy of a maxillofacial prosthetic material will give an indication of the amount of energy available for adhesion and of the susceptibility of the material to bacterial adhesion. PURPOSE: This study evaluated the wettability and surface energies of a range of commercially available silicone rubber maxillofacial prosthetic materials. MATERIAL AND METHODS: Contact angles and surface energies were measured by using a dynamic contact angle measuring technique. Four commonly used silicone maxillofacial materials were tested and their properties compared with those of an acrylic resin denture base material and a widely used denture soft lining material. RESULTS: There were no significant differences in the wettability of the silicone rubber materials. All materials were significantly less wetted than the denture acrylic resin material. There were no significant differences in the surface energies of the silicone rubber materials, but all were significantly lower than denture acrylic resin material. CONCLUSIONS: The Cahn dynamic contact angle analyzer was a quick and reproducible method for determining the contact angles and surface energies of maxillofacial materials. Further work is needed to improve the wettability of silicone rubber materials used for maxillofacial prostheses, thus, reducing their potential to produce friction with tissues.

Acrylic Resins↗
PubMed2001

Pregnancy after tubal sterilization with silicone rubber band and spring clip application.

OBJECTIVE: To determine risk factors for pregnancy after tubal sterilization with silicone rubber bands or spring clips. METHODS: A total of 3329 women sterilized using silicone rubber bands and 1595 women sterilized using spring clips were followed for up to 14 years as part of a prospective cohort study conducted in medical centers in nine US cities. We assessed the risk of pregnancy by cumulative life-table probabilities and proportional hazards analysis. RESULTS: The risk of pregnancy for women who had silicone rubber band application differed by location of band application and study site. The 10-year cumulative probabilities of pregnancy varied from a low of 0.0 per 1000 procedures at one study site to a high of 42.5 per 1000 procedures in the four combined sites in which fewer than 100 procedures per site were performed. The risk of pregnancy for women who had spring clip application varied by location of clip application, study site, race or ethnicity, tubal disease, and history of abdominal or pelvic surgery. The probabilities across study sites ranged from 7.1 per 1000 procedures at 10 years to 78.0 per 1000 procedures at 5 years (follow-up was limited to 5 years at that site). CONCLUSION: The 10-year cumulative probability of pregnancy after silicone rubber band and spring clip application is low but varies substantially by both clinical and demographic characteristics.

Adult↗
PubMed2004

[Contact urticaria to natural rubber latex in childhood and associated atopic symptoms: a study of 27 patients aged under 15 years].

BACKGROUND: Although natural rubber latex hypersensitivity is considered as a major problem in adult, it may be still misdiagnosed in childhood. PATIENTS AND METHOD: We collected 27 observations of natural rubber latex contact urticaria in children under 15 Years of age, 21 of them aged under 8. RESULTS: All of them where atopic and 19 out of 27 presented with other association paroxystic signs of immediate hypersensitivity, that were lately related to latex allergy (i. e. asthma, rhinitis, conjunctivitis, fainting). Cross-allergy to food allergens was present in 33 p. 100. Average level of specific IgE to natural rubber latex was 21.7 kU/l. One to 4 Years follow up confirmed the benefit of latex eviction on urticaria as well as on associated symptoms. It led to the early detection of ficus allergy in 4 of them. DISCUSSION: This series confirms that atopy is at high risk for natural rubber latex allergy in children. These data suggest that atopic children are exposed too early to latex devices such as pacifiers, toodles of latex toys. Contact urticaria in children must be considered as a possible marker of other respiratory or general symptoms that may have been misconsidered under other etiologies.

Adolescent↗
PubMed1989

Follow-up study of reconstructed auricle in microtia: comparison of the results of the rib cartilage framework and the silicone rubber framework methods.

Plastic surgery for microtia had achieved fairly consistent good results since TANZER (Plast. Reconstr. Surg. 23: 1-15, 1959) and recently the modified methods have become popular. The authors did plastic surgery of auricles with the rib cartilage framework method from 1968 until 1986, and with the silicone rubber framework method from 1975 until 1986, and observed each postoperative course for 2 to 10 years. The operative results and the merits and the demerits of each method are reported here. The subjects were 49 ears for the rib cartilage framework method (17 of the former period, 1968-1977, and 32 of the latter, 1978-1986), and 20 ears for the silicone rubber framework method. The operation was performed in 3 stages according to the modified Tanzer's method. The results of operations were subjectively assessed as "satisfied," "fairly satisfied," "a little unsatisfied," and "unsatisfied." The results were as follows: 1) in the rib cartilage framework method, there were 21 satisfied cases (43%), 17 fairly satisfied cases (35%), and 5 unsatisfied cases (10%); 2) there were 8 satisfied cases (40%), 5 fairly satisfied cases (25%), and 6 unsatisfied cases (30%) in the silicone rubber framework method. From the aspect of postoperative management, the rib cartilage framework method is now better but the authors expect the silicone rubber framework method will be improved and used more extensively in the future.

Cartilage↗
PubMed1997

In vitro biocompatibility of EPM and EPDM rubbers.

The in vitro toxicity of two EPDM rubbers (K 778 and K 4802) and one EPM rubber (K 740) was tested using human fibroblasts. The modulus of elasticity of each rubber was varied by exposure to different amounts of electron-beam radiation (0, 5 and 10 Mrad). The short-term in vitro toxicity was tested by culturing cells on polymer films. The long-term effect of ageing was simulated by growing fibroblasts in nutrient media prepared from extracts of heat-exposed materials. Cell cultures were studied both quantitatively and (ultra) structurally. Growth curves obtained in the toxicity test did not differ significantly from control values at any day of observation, and also showed that electron-beam radiation did not alter the biocompatibility. The same results were found for all but one material in the artificial ageing test. The number of cells in the K4802/10 Mrad extraction medium was decreased. Ultrastructurally no gross deviations from normal morphology were observed, either in the direct contact test or in the artificial ageing test. The most characteristic feature was a somewhat dilated endoplasmic reticulum. In summary, the in vitro biocompatibility of EPDM-rubbers as observed in this study is satisfactory and motivates further investigation of their biocompatibility in animal experiments.

Journal Article↗
PubMed2002

Allergenicity of natural rubber latex gloves.

The concentrations of proteins, allergens and rubber chemicals are essential parameters of the allergenicity of NRL gloves. To date, a standardized method has been given only for analysis of the protein concentration (DIN EN 455-3), and not for the concentrations of allergens and rubber chemicals. In the present study, we investigated 11 brands of surgical gloves currently available on the German market. Additionally 1 glove, not subjected to final leaching procedures, was added for comparison purposes. Protein concentrations were analysed by different methods in different laboratories. Allergen concentrations were assayed by prick tests in NRL-allergic volunteers and by RAST inhibition methods. Rubber chemicals were analysed by HPTLC and GC. The protein concentrations analysed by the Lowry method in the 2 laboratories gave concordant results, but the correlations between protein and allergen concentrations were low. The protein concentration analysed by HPLC correlated with the allergen concentration, and gave better information on the allergenicity of the gloves. The development of standardized methods for allergen analysis in the assessment routine is necessary, due to significant discrepancy between protein and allergen levels of some gloves. Thiurams were not found in any of the gloves, though carbamates were present in all gloves tested. Our data indicate that washing procedures have little or no effect on the concentration of rubber chemicals.

Adult↗
PubMed2005

The rubber hand illusion revisited: visuotactile integration and self-attribution.

Watching a rubber hand being stroked, while one's own unseen hand is synchronously stroked, may cause the rubber hand to be attributed to one's own body, to "feel like it's my hand." A behavioral measure of the rubber hand illusion (RHI) is a drift of the perceived position of one's own hand toward the rubber hand. The authors investigated (a) the influence of general body scheme representations on the RHI in Experiments 1 and 2 and (b) the necessary conditions of visuotactile stimulation underlying the RHI in Experiments 3 and 4. Overall, the results suggest that at the level of the process underlying the build up of the RHI, bottom-up processes of visuotactile correlation drive the illusion as a necessary, but not sufficient, condition. Conversely, at the level of the phenomenological content, the illusion is modulated by top-down influences originating from the representation of one's own body.

Adult↗
PubMed1996

Delayed and immediate orofacial reactions following contact with rubber gloves during dental treatment.

Allergic reactions during or after dental examination are uncommon. However, such reactions may be serious and distressing. Allergy to local anaesthetics and dental materials may be considered, but reactions to rubber in gloves worn by the dentist should be remembered. Two patients are reported who experienced symptoms following contact with rubber gloves worn by their dentists, with skin tests subsequently showing an allergic reaction to glove constituents, and in one case latex. With the increasing use of rubber gloves by dental and medical personnel, reactions in sensitised patients are likely to become more common. In patients with a history of symptoms related to dental work, it is important to remember delayed and immediate reactions to rubber.

Dermatitis, Allergic Contact↗
PubMed1990

Laticifer-specific gene expression in Hevea brasiliensis (rubber tree).

Natural rubber, cis-1,4-polyisoprene, is obtained from a colloidal fluid called latex, which represents the cytoplasmic content of the laticifers of the rubber tree (Hevea brasiliensis). We have developed a method of extracting translatable mRNA from freshly tapped latex. Analysis of in vitro translation products of latex mRNA showed that the encoded polypeptides are very different from those of leaf mRNA and these differences are visible in the protein profiles of latex and leaf as well. Northern blot analysis demonstrated that laticifer RNA is 20- to 100-fold enriched in transcripts encoding enzymes involved in rubber biosynthesis. Plant defense genes encoding chitinases, pathogenesis-related protein, phenylalanine ammonia-lyase, chalcone synthase, chalcone isomerase, cinnamyl alcohol dehydrogenase, and 5-enolpyruvylshikimate-3-phosphate synthase show a 10- to 50-fold higher expression in laticifers than in leaves, indicating the probable response of rubber trees to tapping and ethylene treatment. Photosynthetic genes encoding ribulose-bisphosphate carboxylase small subunit and chlorophyll a/b-binding protein are not expressed at a detectable level in laticifers. In contrast, genes encoding two hydrolytic enzymes, cellulase and polygalacturonase, are more highly expressed in laticifers than in leaves. Transcripts for the cytoplasmic form of glutamine synthase are preferentially expressed in laticifers, whereas those for the chloroplastic form of the same enzyme are present mainly in leaves. Control experiments demonstrated that beta-ATPase, actin, and ubiquitin are equally expressed in laticifers and leaves. Therefore, the differences in specific transcript abundance between laticifers and leaves are due to differential expression of the genes for these transcripts in the laticifers.

Journal Article↗
PubMed2006

Clinical field testing of vulcanized rubber feet for trans-tibial amputees in tropical low-income countries.

In a prospective, controlled study, 186 prosthetic rubber feet of different designs were fitted to amputees with trans-tibial prostheses. There were 158 amputees available for follow-up. The amputee compliance was good and 89% were satisfied with their device. After 18 months of use one VI-Solid rubber foot from VVAF in Cambodia had failed, as compared to 11% failures with the same foot with a heel cavity, 3% with the EB-1 sandwich construction from POF in Vietnam, all performing significantly better than the 62% encountered with the vulcanized rubber foot from ICRC in Cambodia; the latter representing half of the feet failing in amputees walking bare-footed. Nearly all failures were located at the foot-sole or the keel. The failure rate was 20% for the HI-Cambodia foot after 12 months. After 24 months of use, still only one VI-Solid rubber foot had failed and this foot design was found superior to the others in regard of durability.

Adolescent↗
PubMed2000

Left tactile extinction following visual stimulation of a rubber hand.

In close analogy with neurophysiological findings in monkeys, neuropsychological studies have shown that the human brain constructs visual maps of space surrounding different body parts. In right-brain-damaged patients with tactile extinction, the existence of a visual peripersonal space centred on the hand has been demonstrated by showing that cross-modal visual-tactile extinction is segregated mainly in the space near the hand. That is, tactile stimuli on the contralesional hand are extinguished more consistently by visual stimuli presented near the ipsilesional hand than those presented far from it. Here, we report the first evidence in humans that this hand-centred visual peripersonal space can be coded in relation to a seen rubber replica of the hand, as if it were a real hand. In patients with left tactile extinction, a visual stimulus presented near a seen right rubber hand induced strong cross-modal visual-tactile extinction, similar to that obtained by presenting the same visual stimulus near the patient's right hand. Critically, this specific cross-modal effect was evident when subjects saw the rubber hand as having a plausible posture relative to their own body (i.e. when it was aligned with the subject's right shoulder). In contrast, cross-modal extinction was strongly reduced when the seen rubber hand was arranged in an implausible posture (i. e. misaligned with respect to the subject's right shoulder). We suggest that this phenomenon is due to the dominance of vision over proprioception: the system coding peripersonal space can be 'deceived' by the vision of a fake hand, provided that its appearance looks plausible with respect to the subject's body.

Aged↗
PubMed1999

Silicone rubber microangiography of injured acute spinal cord after treatment with methylprednisolone and vitamin E in rats.

STUDY DESIGN: An experimental study of changes in the microvasculature of the injured spinal cord that occur with methylprednisolone and vitamin E treatment. OBJECTIVE: To determine the effect of treatment with the methylprednisolone and vitamin E on the microvasculature of the traumatized spinal cord. SUMMARY OF BACKGROUND DATA: Silicon rubber microangiography provided an excellent three-dimensional method for defining the distribution of vasculature in untreated and treated rats after injury. Therefore, silicone rubber microangiography was helpful for elucidating the pathophysiology of posttraumatic ischemia and hemorrhages in the spinal cord. METHODS: In this study, 30 adult rats underwent laminectomy between C7 and T2 followed by extradural spinal cord clipping to produce the compression injury. A control group of 10 rats was left untreated, and 10 rats were treated with methylprednisolone (30 mg/kg bolus and 5.4 mg per hour for 24 hours). Another 10 rats were treated with methylprednisolone and vitamin E (100 U/kg per day). The animals were killed 4, 24, or 48 hours after injury. Silicon rubber microangiography was performed after injury to assess the vasculature of rats' spinal cord. Spinal cord injury causes rapid elevation of noradrenalin, adrenaline, and dopamine. Venous blood samples were taken from all animals before the silicone rubber microangiography was performed. RESULTS: The compression of the spinal cord followed by postinjury treatment with the methylprednisolone and combination methylprednisolone and vitamin E resulted in a ischemic area smaller than that in the untreated group. Adrenaline, noradrenalin, and dopamine levels were less than those in the untreated group. CONCLUSIONS: Findings showed that the addition of vitamin E to the methylprednisolone treatment made no difference in the extent of the ischemic area as compared with methylprednisolone treatment given alone. However, the statistical analysis did not show a significant difference between the treated and untreated groups.

Angiography↗
PubMed1997

Compression stockings and rubber floor mats: do they benefit workers with chronic venous insufficiency and a standing profession?

Chronic venous insufficiency (CVI) is a burden to many workers, especially to those with a standing profession. Preventive measures are seldom taken. A quasirandomized parallel group trial was performed in 114 male workers with CVI and a standing profession. For 3 months, class II compression stockings or rubber floor mats were used vs controls. Outcome measures were diurnal volume changes (leg swelling) and complaints of the lower legs. With the stockings, a significant decrease in complaints was found, as well as a significant decrease in leg swelling. Rubber mats were often not suitable for hygienic and safety reasons. The decrease in complaints in the group using rubber mats was less pronounced, and leg swelling did not differ from that of the control group. Compression stockings appeared to be superior to rubber mats with regard to applicability, diminishing subjective complaints, and decrease of diurnal leg swelling.

Analysis of Variance↗
PubMed1989

A multicentre randomized trial comparing delivery with a silicone rubber cup and rigid metal vacuum extractor cups.

A total of 258 women requiring assisted delivery where vacuum extraction was thought to be suitable were randomly allocated to delivery with a new silicone rubber cup or metal vacuum extractor cups. There was a tendency for the silicone rubber cup to effect delivery more quickly and to cause less scalp trauma, but to fail to effect delivery on more occasions than metal cups. However, none of these differences was statistically significant. There were no statistically significant differences in the rates of birth canal trauma, maternal blood loss, or neonatal jaundice. The silicone rubber cup produced a cosmetically more acceptable chignon than the metal cups. The introduction of vacuum extractors with silicone rubber cups into obstetric units should be encouraged.

Double-Blind Method↗
PubMed1998

Prevalence of natural rubber latex allergy (type I and type IV) in laboratory workers in The Netherlands.

The objective of the study was to study the prevalence of Type IV and Type I allergy to natural rubber latex (NRL) in a population at risk in the Netherlands. Laboratory workers regularly using gloves were invited to complete a questionnaire and to be tested. We performed patch tests with standard contact allergens, rubber additives, glove powder and pieces of 4 gloves; prick tests with inhalant allergens, glove extracts, glove powder and fruit extracts; and RASTs. Glove-related hand dermatitis was reported in 36.9% of the individuals interviewed. A positive patch test result for rubber additives was seen in only 6.6%. Glove-related urticaria, rhinoconjunctivitis and/or asthma were reported in 24.6% of all cases. Confirmation of an IgE-mediated reaction was achieved in 8.3% by prick test with glove extracts and 5.0% by RAST. No reaction to glove powder was noticed in patch testing or in prick testing. A high prevalence rate of glove-related symptoms and NRL Type I allergy was found in laboratory workers exposed to rubber gloves. Surprisingly, there was no co-existence of Type I and Type IV allergy in this population.

Adult↗
PubMed1985

Microbial degradation of natural rubber vulcanizates.

An actinomycete, Nocardia sp. strain 835A, grows well on unvulcanized natural rubber and synthetic isoprene rubber, but not on other types of synthetic rubber. Not only unvulcanized but also various kinds of vulcanized natural rubber products were more or less utilized by the organism as the sole source of carbon and energy. The thin film from a latex glove was rapidly degraded, and the weight loss reached 75% after a 2-week cultivation period. Oligomers with molecular weights from 10 to 10 were accumulated during microbial growth on the latex glove. The partially purified oligomers were examined by infrared and H nuclear magnetic resonance and C nuclear magnetic resonance spectroscopy, and the spectra were those expected of cis-1, 4-polyisoprene with the structure, OHC-CH(2)-[-CH(2)-C(-CH(3))=CH -CH(2)-](n)-CH(2)-C(=O)- CH(3), with average values of n of about 114 and 19 for the two oligomers.

Journal Article↗
PubMed1995

Isolation of microorganisms able to metabolize purified natural rubber.

Bacteria able to grow on purified natural rubber in the absence of other organic carbon sources were isolated from soil. Ten isolates reduced the weight of vulcanized rubber from latex gloves by >10% in 6 weeks. Scanning electron microscopy clearly revealed the ability of the microorganisms to colonize, penetrate, and dramatically alter the physical structure of the rubber. The rubber-metabolizing bacteria were identified on the basis of fatty acid profiles and cell wall characteristics. Seven isolates were strains of Streptomyces, two were strains of Amycolatopsis, and one was a strain of Nocardia.

Journal Article↗
PubMed1997

Comparison of soft tissue response in rabbits following laryngeal implantation with hydroxylapatite, silicone rubber, and Teflon.

This study evaluates the soft tissue response in rabbits following laryngeal implantation for medialization using hydroxylapatite prostheses, carved silicone rubber prostheses, and injectable Teflon. Sixteen rabbits underwent left recurrent laryngeal nerve section for denervation and laryngeal implantation with hydroxylapatite. At 1, 3, 6, and 12 months, 4 animals were painlessly sacrificed and processed for histology. Similarly, animals were implanted with carved silicone rubber prostheses or with Teflon injected through a flap in the thyroid lamina for comparison at 1, 3, and 6 months. In animals implanted with hydroxylapatite, histologic findings include limited acute inflammatory response, thin fibrous encapsulation, and osteogenesis in the region of the fenestra, with lamellar bone bridging the space between the implant and thyroid lamina. With silicone rubber prostheses, there is a limited inflammatory response and fibrous encapsulation of the implant without evidence of osteogenesis. Animals implanted with Teflon demonstrated a classic foreign body reaction with multinucleated giant cells, granuloma formation, and migration of Teflon into surrounding muscle. With respect to soft tissue response, both hydroxylapatite and silicone rubber are less reactive than Teflon. The osteogenesis observed in the presence of hydroxylapatite increases implant stability and minimizes the risk of migration. Conversely, the presence of bone growth may limit the reversibility of medialization procedures performed with hydroxylapatite.

Animals↗