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Objective To analyze the effect of the molecular weight and viscosity of silicone rubber on the release of fluorouracil implants.Methods According to GN/T21863-2008standard and Chinese Pharmacopoeia, the molecular weight and viscosity of different batches silicone rubber were tested, number average molecular weight, molecular weight distribution and viscosity were recorded, which as Xvariables.20different silicone rubber samples were produced by same preparation process, and WS1- (X-103) -2005Zwere used to test the release of each sample, which as Yvariable.Minitab 16software was used to determine the key quality parameters of silicon rubber by multiple regression analysis.Results Number average molecular weight and viscosity were the key quality parameters of silicon rubber, P＜0.05, molecular weight distribution was not the key quality parameter of silicon rubber, P＞0.05;The linear regression equation was:Y=-0.3+3.76 X1+0.267 X3.ConclusionNumber average molecular weight and viscosity of silicone rubber were the key factors affecting the quality parameters of fluorouracil implants releasing, thus strictly control treatment should been implemented on the two quality parameters during production process, for reducing the effect of silicone rubber on the quality stability of the product maximally.
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Objective@#The objective of this study was to compare the early clinical effects of zirconia all⁃ceramic crowns using two different impression methods. Zirconia ceramic crowns were produced using digital models based on either a silicone rubber impression perfusion model in vitro or a 3D mouth scanner.@*Methods @#A total of 50 patients with a planned restoration of the first permanent molar with zirconia all⁃ceramic crowns after root canal therapy were se⁃ lected and randomly divided into two groups: a digital impression by intraoral 3D scanning group and a digital impres⁃ sion by extraoral scanning after silicone rubber impression group. Zirconia all⁃ceramic crowns were created by CAD/ CAM in both groups. Marginal adaptation, proximal contact, and occlusal contact were compared between groups. @*Results@#There was no significant difference between the two groups in marginal adaptation (P > 0.05). For proximal con⁃ tact and occlusal contact, no significant differences regarding the number of cases for the criteria of level A and level B were found between two groups (P > 0.05), while the misfit value in level B was smaller in the first group than in the second group (P < 0.05). @*Conclusion@#Zirconia all⁃ceramic crowns with intraoral 3D scanning show excellent early clinical performance.
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Objective: To compare the effects of ordinary nylon toothbrush,bamboo fiber toothbrush and silicone rubber toothbrush. Methods: 30 and 156 college students were respectively included by the enrolment criterion and were respectively divided into 3 groups. Tooth brushes with the same specification and with the 3 materials were respectively used in the 3 goups with the same methods. Plaque index(PI) (n = 10) was examined before and 1 month after use of the brushes; gingival index(GI) was examined(n = 52) before,1 and 3 month after use of the brushes. Results: 1 month after use of the brushes full mouth PI removal rate(n = 10) and GI reduction(n = 52) were not statistically different among the 3 group(between each 2 groups,P＞ 0. 05). 3 months after use of the brushes GI reduction of the silicone rubber toothbrush group was more than that of ordinary nylon toothbrush and bamboo charcoal toothbrush groups(P ＜ 0. 05). Conclusion: Plaque removal efficiency of the 3 kinds of toothbrush is similar. The silicone rubber toothbrush is more effective for gigiva health than ordinary nylon toothbrush and bamboo charcoal toothbrush.
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To prepare the intrauterine slow release silicone rubber bar made of Panax notoginseng and Rubia cordifolia, and finish its preliminary evaluation of in vitro releasing properties. The open mill method was used for plasticating of silicone rubber. The process parameters of the silicone rubber and drugs mixing were optimized by orthogonal test. The parameters of silicone rubber vulcanization was optimized by single factor test. The preliminary evaluation of in vitro release performance of the silicone rubber bar was conducted with ginsenoside Rg₁, ginsenoside Rb₁, notoginsenoside R₁, purpurin and rubimaillin as the indexes. The results showed that optimum technologic parameters for silicone rubber and drugs mixing：the roller spacing 2 mm; speed ratio 1∶1.2; front roller temperature 55-60 ℃; rear roll temperature 50-55 ℃; and mixing time 20 min. The optimum parameters for silicone rubber vulcanization：temperature 90 ℃, and time 60 min. The studies on release process in vitro revealed that the release process of silicone rubber bar was in line with the Higuchi equations. After 90 days, the cumulative release of ginsenoside Rg₁, ginsenoside Rb₁ and notoginsenoside R₁ was 46.7%, and the cumulative release of purpurin and rubimaillin was 51.9%. The preparation method can be applied to the preparation of silicone rubber bar, with slow release characteristics.
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Calcification of silicone rubber is a pathologic mineralization phenomenon which occurs on the surface after it is implanted in vivo,and there is no effective prevention method.The important process of calcification including these steps:phosphate ions combined with calcium ions to promote nucleating aggregation,slow increasing,fusion,and gradually form a larger accumulation of hydroxyapatite calcium.The research had been developed to the level of cells and genes,such as matrix Gla protein clusters is a calcification inhibitor of the tissues around silastic prosthesis.It is necessary to obtain a theoretical breakthrough in the aspect of organic template modulation of inorganic crystals.Silicone elastomer having its own local anti-calcification property had been paid more attention.Fully revealing the mechanism of calcification and calcification-resistant of silicone rubber will probably provide the basis for building a new anti-calcification material.
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Objective To explore mechanical property changes of methyl vinyl silicone rubber modified by ferric nanoparticles and its dispersed phase.Methods Mechanical properties such as Shore A hardness,tensile strength,elongation at break,tearing rate of permanent deformation and tearing strength of pre-prepared ironic nanoparticle enhanced silicone rubber and carbon-coated ferric particle reinforced silicone rubber were tested according to national standards.A thermal field emission scanning electron microscope (TFE-SEM) was used to investigate the morphology of both surface and fracture of the composite materials and to observe the dispersion of ferric nanoparticles in them.Results Mean values of Shore A hardness,tensile strength,elongation at break,tearing permanent deformation rate and tear strength of modified composites increased with the increasing amounts of ferric nanoparticles,however,when the quota of ironic nanoparticles in the composite formula were greater than 17 phr,carbon-coated ferric nanoparticles more than 19 phr,the mean values of tensile strength of two composites stopped increasing and presented the declining trend.When the quota of ferric nanoparticles in the formula exceeding 15 phr,the mean values of elongation at break and tear strength began to decrease in the formula ratio of silicone rubber/ferric nanoparticles up to 85:15,while the Shore A hardness of samples increased all the way.Ferric nanoparticles dispersed evenly on the surface of composites.Nanopowder aggregation in the fracture surface of both composites could be observed at the formula ratio of 85:15 of silicone rubber/iron nanoparticle and 87:13 of silicone rubber/carbon-coated iron specimen.Conclusion Effect of iron nanapareticles and carbon-coated ferric nanoparticles on the mechanical properties of the reinforced methyl vinyl silicone rubber depends on the nanoparticle size,additive amount and agglomeration.
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Silicone rubber with advantages of stable performance, easy-shaping, considerable product bene- fits, has been widely used in biomedical engineering field and health care industries. Nevertheless, the application of silicone rubber in biomedicine is still challenged by its inherent shortcomings. In biocompatibility aspects, disad- vantages of silicone rubber products need to be overcome, including.'hydrophobic surface, poor imaging compatibili- ty, and occurrence of calcification after long-term implantation in body. Experts from all over the world have been studying on means of modifications over the past few years and the researches mainly focus on increasing the surface wettability, enhancing the function of X-ray resistance, and anti-calcification pre-treating. Although initial results are encouraging, biocompatibility of medical silicone rubber is not yet satisfactory.
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Silicone has become one of the most commonly used biomaterials in modern medicine. There are three forms of silicone in medical use: silicone oil, gel, and rubber. Among these, silicone rubbers are used as heart valves, shunts, coatings on pacemakers and implants of cosmetic surgery. In tissues, silicone produces a range of histological reactions depending on the form of silicone. We report a case of a foreign body granuloma due to the prescence of silicone rubber inserted for nasal augmentation fifteen years previously, and review the complications of augmentation rhinoplasty using silicone implants.
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Materiais Biocompatíveis , Corpos Estranhos , Granuloma de Corpo Estranho , Valvas Cardíacas , História Moderna 1601- , Rinoplastia , Borracha , Elastômeros de Silicone , Óleos de Silicone , Pele , Cirurgia PlásticaRESUMO
Current materials used for maxillofacial prostheses are far from ideal,and how to develop a final prosthetics material is a significant topic in the research of maxillofacial prostheses.In this paper,some pertinent research of silicone elastomeric materials,such as mechanical properties and colorant are reviewed.
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Augmentation rhinoplasty is one of the most popular aesthetic procedure in Asians. Numerous alloplastic implants have been used until now, but no accurate comparative analysis about the implant materials has been reported yet. This study in animal model was designed to determine the safety and effectiveness of various implant materials in augmentation rhinoplasty. The 15 x 15 x 2 mm sized square shaped plate of Gore-Tex(R), silicone rubber, and 15 x 15 x 1.5 mm sized Medpor(R) were implanted under panniculus carnosus of the abdomen wall of rat. And tissue specimens including the implant and surrounding soft tissue were obtained by en bloc excision in 6 months after implantation. The implants were estimated in weight and volume, and also the specimens were examined grossly and microscopically. The results revealed that increase of average weight 26.9%, decrease of average volume 55.4% in Gore-Tex(R) implant, increase of each average weight and volume 62.6%, 8.7% in Medpor(R) implant and very slight increase of both average weight and volume 4.7%, 1.1% in silicone rubber implant. Grossly, the Gore-Tex(R) was deformed, Medpor(R) was strongly adherent to surrounding soft tissue and the silicone rubber was well encapsulated and easily peeled off. Microscopically, silicone rubber showed foreign body reaction slightly and there were no inflammatory responses in all alloplastic implants. In our study, silicone rubber showed very proper alloplastic features for augmentation rhinoplasty due to causing no inflammatory response, no physical change, and no deformity.
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Animais , Humanos , Ratos , Abdome , Povo Asiático , Anormalidades Congênitas , Reação a Corpo Estranho , Modelos Animais , Rinoplastia , Elastômeros de SiliconeRESUMO
Objective To prepare complex material—hydroxyapatite/silicone rubber (HA/SR) used in filling parenchyma and to measure and analyse its mechanical properties, looking for proper proportion of material. Methods The complex material was mixed based on different proportion (the HA/SR mass ratio of 23%, 33.3% and 41%), and its respective properties were tested according to national standard and performed statistical analysis. Results With the increasing proportion of hydroxyapatite in complex material, the rigidity of complex material enhanced gradually, but the mechanical property decreased. Conclusion If the HA/SR mass ratio was 23% to 33.3%, the mechanical properties of complex material are equal to that of pure SR. If the HA/SR mass ratio was over 41%, the mechanical properties of complex material decrease so that the complex material can not be used in filling.
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ObjectiveAfter performed the silicone-rubber membrane implantation in rabbits, we investigated the efficacy and security of the silicone-rubber membrane implant through observed intraocular pressure, bleb and morphologic result. MethodsForty rabbits were divided into 4 groups by randomized fashiones. Each group consisted of 10 rabbits. Subscleroflapectomy and the silicone membrane implantation were operated in one eye of each rabbit. And the other eye was only performed subscleroflapectomy, which be controlled eye. The change of intraocular pressure, bleb were observed postoperatively. And every eye for histopathologic examination. ResultsThe lasted time of lower intraocular pressure and filtration bleb in implanted eyes were longer than controlled eyes in two groups. Light microscope revealed that patent drainage tract and bite site could be seen in cilicone membrafe implant eyes. The activity and regularity of fibroblast proliferation in implanted eyes and controlled eyes were similarly. The excessive expression of fibroblast proliferation was not excit ed by silicone membrane. ConclusionIt is characterized by safely, effectively and operate simply that silicone membrane implant drainage surgery act as a new drainage surgery.
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Permanent vascular access is a prerequisite for successful treatment of patients with chronic hemodialysis. Although a number of strategies including native and synthetic arterio-venous fistulae are performed to create vascular access, they are often not available due to peripheral vascular diseases which are common in patients with diabetes and elderly patients. So, in spite of technical advance, vascular access for hemodialysis remains a significant problem confronting the nephrologists. Recently, Permcath(R) (double lumen silicone rubber catheter) has been introduced and can provide temporary access in patients whose native fistulas have not yet matured and permanent access in patients who have difficulty in creating a arterio-venous fistula. We investigated the availability and the clinical outcome of use of Permcath(R) as temporary or permanent vascular access. Total 16 catheters were placed in 14 patients who were admitted in Chung-Ang University Hospital between April, 1993 to March, 1996. Clinical course of the patients and outcome of the catheters were observed, retrospectively. The mean age of the 14 patients was 56 9 (39-67) years. The indications were exhausted peripheral access, poor vascular system for conventional access operation, and limited life expectancy. The median survival of the catheters was 80 weeks with a range of one week to 113 weeks. The one-year actuarial catheter survival rate was 67% and 44% at 2 year. The most common complication during use of Permcath(R) was infection, occurred in 5 patients (31.2%). The 5 catheters were removed because of complications of catheter such as infection or malfunction. We suggest that the Permcath(R) is a safe and durable temporary vascular access for patients with poor vascular system anticipating a long duration for arterio-venous fistula maturation and permanent access for patients who have exhausted peripheral access sites.