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PubMed1995

An innovative method of cushioning metal clamp jaws during rubber dam isolation.

Competent rubber dam use increases both operating speed and treatment quality. In many instances, however, the application of rubber dam clamps may cause immediate and/or postoperative discomfort, and some dentists continue to use this as a "justifiable" excuse for not employing rubber dam. This paper reviews the iatrogenic potential of metal rubber dam clamps, and introduces a new cushioning technique that makes use of light-cured provisional material.

Acrylic Resins↗

PubMed1993

[Reproductive dysfunction and oncologic diseases in women employed in the rubber manufacturing industry].

The study covered analysis of reproductive function, incidence of chronical diseases and gynecologic malignancies in rubber female workers. Hazardous work conditions of rubber production were reported to afflict reproductive function promoting gynecologic diseases and to change the structure of oncologic morbidity. Female workers exposed to occupational hazards of rubber production show some long-term effects of the exposure such as reliably increased reproductive impairments. Mechanism of such impairments may be connected with endocrine disbalance especially with estrogen deficit. As a result of it the changed ratio breast/uterus and ovary cancers is found among female rubber workers in comparison with the general population.

Adult↗

PubMed1993

A comparison of CO2 laser ignition of the Xomed, plastic, and rubber endotracheal tubes.

The combustibility of Xomed LaserShield endotracheal tubes was compared to that of polyvinylchloride (PVC) and rubber endotracheal tubes at 15, 17, and 20 watts (W) of power from a CO2 laser. Oxygen, 5.0 L/min, flowed through the tubes during the investigation. The laser was aimed perpendicularly at the shaft of the endotracheal tube under study and actuated until an intraluminal fire occurred. The times to blow torch combustion of the PVC tubes were 1.7, 1.8, and 1.5 s at 15, 17, and 20 W, respectively. For the Xomed tube, the times to combustion were 85.9, 42.5, and 20.3 s at 15, 17, and 20 W, respectively. Intraluminal (blow torch) fires of the rubber endotracheal tubes occurred after 24.5, 25.4, and 21.9 s at 15, 17, and 20 W. The times to combustion of the PVC and Xomed tubes were significantly different at 15 and 17 W. The times to intraluminal combustion of the rubber tubes were significantly different from those of the Xomed tubes only at 15 W. We conclude that the Xomed tube does not offer consistently better resistance to laser-induced combustion than the PVC or rubber endotracheal tubes tested.

Fires↗

PubMed1997

An immediate (type I) hypersensitivity reaction during placement of a dental rubber dam.

A dental student developed swelling of the lips and peri-oral urticaria, immediately after placement of a dental rubber dam during a chairside demonstration of clinical dentistry. A provisional diagnosis of a Type I hypersensitivity reaction to natural rubber latex was made and an appointment organised for specialist investigations. The student reported an atopic history and allergy to peanuts. A Radioallergosorbent Test (RAST), to measure Ig-E antibodies to latex, was positive. The dental student was given advice concerning the avoidance of natural rubber latex. Dental staff must be aware of potentially serious reactions to natural rubber latex in the dental surgery.

Adult↗

PubMed1999

Direct analysis of oligomeric tackifying resins in rubber compounds by automatic thermal desorption gas chromatography/mass spectrometry

Two analytical methods, automatic thermal desorption gas chromatography/mass spectrometry (ATD-GC/MS) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), were applied as direct methods for the analysis of oligomeric tackifying resins in a vulcanized rubber. The ATD-GC/MS method, based on discontinuous volatile extraction, was found to be an effective means for direct analysis of the oligomeric tackifying resins contained in a vulcanized rubber. The oligomeric tackifying resins, such as t-octylphenolformaldehyde (TOPF) resin, rosin-modified terpene resin, and cashew resin, could be directly analyzed in vulcanized rubber by ATD-GC/MS. Much simpler total ion chromatograms were obtained by ATD-GC/MS than by flash pyrolysis with a Curie-point pyrolyzer, permitting much easier interpretation. Ions at m/z 206, 135, and 107 were fingerprints in the characteristic mass spectra obtained by ATD-GC/MS for TOPF resin in the vulcanized rubber. 1H-Indene, styrene, and isolongifolene were observed as their characteristic mass spectra in the pyrolyzate of the rosin-modified terpene resin. From the cashew resin, phenol, 3-methylphenol, and 4-(1,1,3, 3-tetramethylbutyl)phenol were obtained as the characteristic pyrolyzates by discontinuous thermal extraction via ATD-GC/MS. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

PubMedDate not supplied

Evaluation of in vivo adsorption of blood elements onto hydrogel-coated silicone rubber by scanning electron microscopy and fourier transform infrared spectroscopy.

Three hydrogel formulations consisting of 2-hydroxyethyl methacrylate (HEMA) copolymerized with N-vinyl pyrrolidone (NVP) were incorporated into silicone rubber by irradiation-induced polymerization. These coatings were chosen to represent different degrees of hydrophilicity, and they changed the hydrophobic character of the silicone rubber surface to that of hydrophilic. These composite materials and the silicone rubber comparison material were used as femoral artery-to-vein (A-V) shunts and were removed at 15 min, an approximate time representative of an initial buildup stage of blood elements on test surfaces. Data obtained by scanning electron microscopy (SEM) were used to determine the type and amount of adhering blood cells and fibrin at the time interval described. One-half of each specimen was used for Fourier Transform Infrared (FT-IR) analysis to provide a direct comparison of the relative amounts of protein present on the silicone rubber and the three hydrogel composite samples. The combined SEM and FT-IR analyses were performed on A-V samples from three dogs. Differences in the response of blood to the surfaces were found by the combined SEM and FT-IR analyses. The more hydrophilic a hydrogel grafted surface, the less fibrin and cellular elements were seen deposited on it. This is not interpreted as an indication of less reactivity, but is more likely due to thrombus buildup and a degree of subsequent embolization (a tearing of sections of the platelet matting away from a surface, revealing an area that again can be covered.

Acrylates↗

PubMed2005

Reduced adherence of Candida to silane-treated silicone rubber.

Silicone rubber is widely used in the construction of medical devices that can provide an essential role in the treatment of human illness. However, subsequent microbial colonization of silicone rubber can result in clinical infection or device failure. The objective of this study was to determine the effectiveness of a novel silane-treated silicone rubber in inhibiting microbial adherence and material penetration. Test material was prepared by a combination of argon plasma discharge treatment and fluorinated silane coupling. Chemicophysical changes were then confirmed by X-ray photoelectron spectroscopy, contact-angle measurement, and atomic force microscopy. Two separate adherence assays and a material penetration assay assessed the performance of the new material against four strains of Candida species. Results showed a significant reduction (p < 0.01) of Candida albicans GDH 2346 adherence to silane-treated silicone compared with untreated controls. This reduction was still evident after the incorporation of saliva into the assay. Adherence inhibition also occurred with Candida tropicalis MMU and Candida krusei NCYC, although this was assay dependent. Reduced penetration of silane-treated silicone by Candida was evident when compared to untreated controls, plaster-processed silicone, and acrylic-processed silicone. To summarize, a novel silicone rubber material is described that inhibits both candidal adherence and material penetration. The clinical benefit and performance of this material remains to be determined.

Argon↗

PubMed1986

Permeation of mouse skin and silicone rubber membranes by phenols: relationship to in vitro partitioning.

A discrepancy has been noted in the relationship between the relative skin permeabilities of phenols and their lipophilicities as expressed in commonly used octanol:water partition coefficients (PCoctanol:water). The lack of correlation between partitioning and permeability is seen with the nitrophenols, particularly 4-nitrophenol. In the present study, the permeability coefficients-of 4-nitrophenol and several other phenols through skin and a model lipophilic membrane made of silicone rubber were found to be independent of concentration, ruling out concentration-dependent molecular aggregation as the cause of the partitioning-permeability incongruity. An unexpectedly low permeation rate was observed for the diffusion of 4-nitrophenol through the synthetic, silicone rubber membrane, confirming the anomalous position of this phenol in permeability relative to the octanol:water partitioning scale. However, when oil:water (o/w) partition coefficients for the phenolic compounds based on either n-hexane, CH2Cl2, CHCl3, or silicone rubber as the water immiscible phase are used, permeability coefficients for the skin and the synthetic membrane followed expected permeation-partitioning dependencies. On this basis, it appears that PCoctanol:water does not properly reflect the lipophilicity of the phenols with respect to partitioning into skin and silicone rubber during mass transfer.

Animals↗

PubMed1986

A case of blue rubber bleb nevus syndrome with familial onset.

We experienced a case of blue rubber bleb nevus syndrome with familial onset. The patient was a 32-year-old male with a gallstone and many bluish rubber bleb-like hemangiomas on the skin. He suffered from repeated rectal bleeding and underwent a sigmoidectomy at age 17. Gastrointestinal hemangiomas were recognized in the esophagus, stomach, ileum and colon. An angiogram revealed multiple small poolings in the liver, suggesting the presence of hemangiomas. During the cholecystectomy, surgeons noted the presence of hemangiomas on the surface of the liver, serosa of the small intestine and retroperitoneum. Out of 73 blood relatives, 24 also had bluish skin hemangiomas, suggesting them to be inherited by an autosomal dominant trait. More than sixty cases of this syndrome had been reported in the world, eight of which had family histories of skin lesions. However, in only three cases, including our own, was the presence of skin and gastrointestinal hemangiomas recognized. Because the clinical indications for diagnosis of blue rubber bleb nevus syndrome consist of minimal to massive bleeding from the gastrointestinal tract, the possibility that this syndrome is present should be considered when diagnosing a bleeding patient with multiple bluish rubber bleb-like skin lesions, in addition to taking a detailed family history.

Adult↗

PubMed1997

A new method for in vivo evaluation of biofilms on surface-modified silicone rubber voice prostheses.

A new method is presented that permits a rapid and accurate in vivo evaluation of biofilm formation on surface-modified silicone rubber voice prostheses. The method is based on partial modification of a Groningen button voice prosthesis by exposing half of the prosthesis to an argon plasma. This results in one side of the prosthesis becoming hydrophilic while leaving the unmodified side hydrophobic as a control. Modified prostheses were placed in patients for an evaluation period of approximately 4 weeks. Despite making the silicone rubber surface hydrophilic, biofilm formation was stimulated when compared to unmodified, hydrophobic silicone rubber. Findings show that biofilm formation on voice prostheses is influenced by hydrophobicity of a silicone rubber surface. The method of partial surface modification used was seen to be suitable for demonstrating such influences regardless of nutrition and other variations in the patient's lifestyle. Microbiological analysis of the biofilms on both sides of the prosthesis valve did not show any changes in microbial composition, with Candida albicans, streptococci and staphylococci being the most commonly isolated strains.

Biofilms↗

PubMed2000

Inhibition of uropathogenic biofilm growth on silicone rubber in human urine by lactobacilli--a teleologic approach.

The ability of three Lactobacillus strains to inhibit the adhesion and growth of naturally occurring uropathogens on silicone rubber was investigated in human urine. The importance of biosurfactant production by Lactobacillus in discouraging uropathogen growth was determined in relation to the binding affinities of the lactobacilli for silicone rubber. L. fermentum B54 markedly inhibited uropathogen growth on the silicone rubber disks after 8 days for all five men included in the study, albeit to various extents ranging from 77% to 100%. In urine from women, however, this inhibition was less clear, as it was absent for two of the four women participating in this study. L. casei rhamnosus 36 completely discouraged uropathogen growth on the disks after 8 days for three of the four women, whereas its effect in urine from men was less pronounced (inhibition ranged from 48% to 100% and was absent for one man). L. casei rhamnosus ATCC 7469T was the least inhibitory Lactobacillus strain tested and inhibition was absent for a number of both male and female participants, possibly as a result of the low binding affinity of this strain for silicone rubber and of its inability to release biosurfactants. We conclude that the inhibition of uropathogen growth is dependent on the Lactobacillus strain involved, and for L. fermentum B54 it was demonstrated to be sex-related. Hence, inhibition must be considered a multifactorial process.

Adult↗

PubMed2004

Silicone rubber: an alternative for repair of articular cartilage defects.

Silicone-rubber implants were used to fill full-thickness articular cartilage in the trochlea area of the knee joint in rabbits, for the purpose of studying the long-term influence of silicone-rubber implant on surrounding articular cartilage. Forty eight weeks after surgery, the silicone rubbers were still fitted tightly into the defects; surrounding cartilage showed mild degeneration, better than the control group. Our results showed silicone-rubber implantation for repairing local articular cartilage defects can effectively delay the pathogenetic progression of osteoarthritis.

Animals↗

PubMed1998

Rubber band ligation of hemorrhoids: relapse as a function of time.

Rubber band ligation is a well established treatment of internal second-degree hemorrhoids. Up to now, the long-term results (> 5 years) of this method have not been assessed. The aim of this study was to determine the long-term success rate of rubber band ligation in patients with a first episode of second-degree hemorrhoids not responding to medical treatment (local cream with laxative). A total of 92 patients who were treated between 1979 and 1997 for second-degree hemorrhoids responded to a questionnaire. The need for complementary conservative (sclerotherapy, cryotherapy or rubber band ligation) or surgical treatment was considered indicative of relapse. The collected data were analyzed according to the Kaplan-Meier method. The average follow-up time was 5.6 years. There were 21 patients who suffered a relapse. The probability of successful treatment was 0.77 (range: 0.67-0.88) after 5 years and 0.68 (range: 0.5-0.86) after 10.6 years. We conclude that rubber band ligation represent an efficient long-term treatment for second-degree hemorrhoids. Approximately two thirds of the patients are cured after 5 years and more than a half after 10 years.

Female↗

PubMed1994

Plasma-induced graft copolymerization of HEMA onto silicone rubber and TPX film improving rabbit corneal epithelial cell attachment and growth.

A poly(2-hydroxyethyl methacrylate) (pHEMA)-grafted polymer film was prepared by plasma-induced graft copolymerization onto an elastic material, silicone rubber, and a plastic material, poly(4-methyl-1-pentene) (TPX). The control, Ar plasma-treated and pHEMA-grafted silicone rubber and TPX surfaces were characterized by ESCA, FTIR-ATR, SEM and contact angle techniques. ESCA verified the respective chemical shift of control and Ar plasma-treated films. The presence of the grafted pHEMA was also verified by ESCA. The introduction of pHEMA onto a hydrophobic support provided an adequate surface for rabbit corneal epithelium cell attachment and growth. Cell attachment and growth onto these surfaces were examined by light microscopy. Cell attachment onto the control and Ar plasma-treated surfaces was negligible, while improved attachment and growth of rabbit corneal epithelium cells was demonstrated on the pHEMA-grafted polymeric surface. At 72 h, the pHEMA-grafted silicone rubber surface attached and grew more cells as compared with those on a pHEMA-grafted TPX surface. The pHEMA-grafted silicone rubber surface demonstrated a confluent cell layer after 72 h.

Animals↗

PubMed2004

Depolymerization of beta-chitin to mono- and disaccharides by the serum fraction from the para rubber tree, Hevea brasiliensis.

The serum fraction of latex from Hevea brasiliensis, the para rubber tree, is known to contain an endo-chitinolytic enzyme, hevamine. Herein the activity of the rubber serum towards beta-chitin is investigated. The serum contained 6 mg/mL of protein and a chitinolytic activity of 18 mU permg of protein. The optimum ratio of enzyme to chitin was 0.22 mU/mg, and the optimum substrate concentration was 60 mg/mL. The optimum pH range was pH2-4, and the optimum temperature was 45 degrees C. At these conditions both (GlcNAc)2 and GlcNAc were produced in a molar ratio of approximately 2:1. The hydrolysis of 300 mg of chitin with 64 mU of the rubber serum for 8 days under the optimum conditions gave 39 mg of GlcNAc and 108 mg of (GlcNAc)2 as determined by HPLC. Mixing the rubber serum preparation with an Aspergillus niger pectinase preparation containing beta-N-acetylhexosaminidase can be used to produce almost exclusively the GlcNAc monomer in about 50% yield.

Aspergillus niger↗

PubMed2006

Silicone rubber mould cast polyethylmethacrylate-hydroxyapatite plate used for repairing a large skull defect.

INTRODUCTION: Reconstruction of the cranial vault is performed for various reasons and precise repair of the defect is important. A modified method of cranioplasty is presented using three-dimensional (3D) models and polyethylmethacrylate mixed with hydroxyapatite, cast in a silicone rubber mould. PATIENT AND METHOD: A large custom made cranial implant was produced using data acquired from 3D computer tomography, rapid prototyping and cast in a silicone rubber mould. This plate was then applied to a 53 year-old man who had undergone a decompressive fronto-parieto-temporo-occipital craniotomy. The bone flap had been lost due to infection. The cranioplasty was performed at 1 year after the initial operation. RESULTS: The cranial plate fitted precisely into the defect and needed no correction at the time of surgery. The stability of the reconstruction plate was increased by the presence of thin margins allowed by silicone rubber elasticity. No complications occurred and the final functional and aesthetic results were good. CONCLUSION: The use of 3D imaging and rapid prototyping allow precise repair of large skull defects, with good aesthetic and functional results. At the same time, silicone rubber moulds permit the production of very thin details needed not only for cosmetic reasons but for reconstruction plate stability as well.

Bone Plates↗

PubMed2006

Acoustic analysis of bound rubber formed in silica/SBR compounds.

The compressibility of the bound rubber around the silica particle was evaluated by an acoustic technique. The density and the longitudinal wave velocity of a silica/SBR compound were measured as a function of the silica content. The density increased linearly with the filler content. The longitudinal wave velocity was almost constant within the experimental error. The mass ratio of the bound rubber to the silica in the silica/SBR compounds was 1.08+/-0.03 kg kg(-1) which was measured by a thermal gravimetric analysis (TGA). The partial specific adiabatic compressibility of the silica was estimated as (0.1+/-0.5) x 10(-10) Pa(-1) on the basis of a three states model. The adiabatic compressibility of the bound rubbers in the silica/SBR compounds was (4.6+/-0.5) x 10(-10) Pa(-1). The compressibility was almost the same as that of the SBR, and the value was twice larger than the compressibility of the bound rubber formed in a CB/SBR composite.

Journal Article↗

PubMed1996

Hardness and shock absorption of silicone rubber for mouth guards.

Silicone rubbers have general properties that make them suitable for the fabrication of custom-made mouth guards. This study evaluated the shock absorption properties and Shore A hardness of several silicone rubbers and derived products, compared their values with those of materials commonly used for the manufacture of mouth guards, and correlated the shock absorption and transmission abilities of these different materials with their Shore hardness. Silicone rubbers absorb shock better than the materials currently used for custom-made mouth guards. In addition, to adapt mouth guards to particular sports, the properties of the silicone rubbers can be appropriately modified by the addition of oils or glass fiber reinforcement. Statistical analysis of hardness values and transmitted forces for the 27 materials tested indicates that the maximum transmitted force increases with hardness. However, this relationship is not linear, and departure from linearity is greatest for minimal and maximal hardness values.

Absorption↗