This paper reviews and analyzes the modifications of silicone rubber, containing nanometer material tilling, plasma surface modification, surface grafting, mixture with bioactive substrates and bionic coating. At last, the author shows the prospect for the future development of silicone rubber modification.
Equipment and Supplies ; Humans ; Silicone Elastomers ; chemistry

OBJECTIVES: This work aimed to synthesize a novel injectable alginate impression material and evaluate its accuracy. METHODS: Certain proportions of sodium alginate, trisodium phosphate dodecahydrate, potassium fluorotitanate, diatomaceous earth, and other ingredients were dissolved in water and mixed evenly with a planetary centrifugal mixer to obtain a certain viscosity base paste. Certain proportions of calcium sulfate hemihydrate, magnesium oxide, glycerin, and polyethylene glycol (PEG) 400 were mixed evenly with a planetary centrifugal mixer to obtain the reactor paste with the same viscosity as the base paste. The base and reactor pastes were poured into a two-cylinder cartridge at a 2∶1 volume ratio. A gun device was used to accomplish mixing by compressing materials into a mixing tip. The samples were divided into three groups: injectable alginate impression materials (IA group) as the experimental group, and Jeltrate alginate impression materials (JA group) and Silagum-putty/light addition silicone rubber impression materials (SI group) as the two control groups. RESULTS: Scanning electron microscopy (SEM) showed that the injectable alginate impression materials had a denser structure and fewer bubbles than the commercial alginate impression material. The accuracy of the three kinds of impression materials was evaluated by 3D image superposition. The deviations between the three test group models and the standard model (trueness) were 49.58 μm±1.453 μm (IA group), 54.75 μm±7.264 μm (JA group), and 30.92 μm±1.013 μm (SI group). The deviations of the models within each test group (precision) were 85.79 μm±8.191 μm (IA group), 97.65 μm±11.060 μm (JA group), and 56.51 μm±4.995 μm (SI group). Significant differences in trueness and precision were found among the three kinds of impression materials (P<0.05). CONCLUSIONS The accuracy of the new injectable alginate impression material was better than that of the traditional powder-type alginate impression material but worse than that of the addition silicone rubber impression materials. The novel injec-table alginate impression material demonstrated good operation performance and impression accuracy, showing broad application prospect.
Alginates/chemistry* ; Silicone Elastomers/chemistry* ; Dental Impression Materials/chemistry* ; Powders

OBJECTIVETo evaluate the dimensional stability and detail reproduction of five additional silicone impression materials after autoclave sterilization.

METHODSImpressions were made on the ISO 4823 standard mold containing several marking lines, in five kinds of additional silicone. All the impressions were sterilized by high temperature and pressure (135 °C, 212.8 kPa) for 25 min. Linear measurements of pre-sterilization and post-sterilization were made with a measuring microscope. Statistical analysis utilized single-factor analysis with pair-wise comparison of mean values when appropriate. Hypothesis testing was conducted at alpha = 0.05.

RESULTSNo significant difference was found between the pre-sterilization and post-sterilization conditions for all locations, and all the absolute valuse of linear rate of change less than 8%. All the sterilization by the autoclave did not affect the surfuce detail reproduction of the 5 impression materials.

CONCLUSIONSThe dimensional stability and detail reproduction of the five additional silicone impression materials in the study was unaffected by autoclave sterilization.

Dental Impression Materials ; chemistry ; Dental Models ; Hot Temperature ; Materials Testing ; Microscopy ; Polyvinyls ; chemistry ; Silicone Elastomers ; chemistry ; Siloxanes ; chemistry ; Sterilization ; methods

Skin frictional properties of four kinds of prosthetic materials in common use have been researched. Experiments are carried out on residual limb and on normal tibia. Surface roughness and the hydrophobic/hydrophilic of the skin and materials are also tested. Under normal load 0.3 N and 0.7 N, the friction coefficient of silicon rubber and skin has the maximum value among all the materials due to the surface property of silicon rubber (containing oil). There is remarkable difference in friction coefficient between normal skin and amputee skin when they are in contact with silicon rubber (P<0.05). Other materials show "the higher the hydrophobia tendency of surface, the lower the friction coefficient". There are no significant differences (P>0.05) in friction coefficient between amputee skin and normal skin when they are in contact with all materials under normal load 8 N.
Acrylates ; chemistry ; Artificial Limbs ; adverse effects ; classification ; Friction ; physiology ; Humans ; Hydrophobic and Hydrophilic Interactions ; Materials Testing ; Polyethylene ; chemistry ; Silicone Elastomers ; chemistry ; Skin Physiological Phenomena ; Touch ; physiology

This study taking gestodene (GEST) as a model, investigated the factors affecting reservoir-type intravaginal ring (IVR)'s drug release. This paper reported a gestodene intravaginal ring of reservoir design, comprising a gestodene silicone elastomer core encased in a non-medicated silicone sheath, separately manufactured by reaction injection moulding at 80 degrees C and heating vulcanization at 130 degrees C is reported. The test investigated the factors affecting drug release through a single variable method, taking the drug release rates of 21 days as standards. When changing the thickness of the controlling sheath outside, the ratio of the first day of drug release and mean daily release (MDR), named the relatively burst effect, is closing to 1 with the thickness of controlling sheath increasing, while the 1.25 mm sheath corresponding to 1.04 controlled the burst release effectively; a positive correlation (r = 0.992 2) existed between the average drug release (Q/t) and drug loading (A) within a certain range. The C6-165 controlling sheath with high solubility of GEST is easier to achieve controlled release of the drug; GEST crystalline power is more effective to implement controlled release of drugs among difficent states of the drug. A 1/4 fractional segment core gives a relatively burst effect of 1.76, while the 1/1 and 1/2 are 1.93 and 1.87 separately, at the same drug loading, concluding that use of a fractional segment core would allow development of a suitable GEST reservoir IVR. In summary, GEST reservoir-type IVR could be adjusted by the thickness of controlling sheath, the loading of drug, the material properties of controlling sheath, the dispersion state of drug, the additive composition and structure of intravaginal ring, to control the drug release behavior and achieve the desired drug release rate.
Administration, Intravaginal ; Contraceptive Agents, Female ; administration & dosage ; Contraceptive Devices, Female ; Delayed-Action Preparations ; Drug Delivery Systems ; methods ; Norpregnenes ; administration & dosage ; chemistry ; Silicone Elastomers ; chemistry ; Solubility

OBJECTIVEThe aim of this paper is to introduce the clinical and laboratory procedures of fabricating silicone gingival epithesis and evaluate the long-term effects of the epithesis.

METHODSFlexible gingival epithesises were fabricated by the same way of fabricating partial denture, and their effects were evaluated in 31 patients by following up for 8-20 months.

RESULTSPatients' responses to appearance showed that their esthetic appearance had been much improved in all of the patients and the comfort and retention of their epithesises varied from good to excellent in almost all the patients. Discoloration of the epithesises was noticed by the patients within ten months in average. Doctors' examination confirmed patients' responses, and caries was detected at the necks of teeth covered by epithesises and slight gingivititis was discovered in the area under the epithesises in two cases.

CONCLUSIONFlexible gingival epithesis is a simple and effective method for correcting gingival recession, and the fabrication is simple and don't need special equipment. However, discoloration of the epithesis remains a problem.

Adult ; Denture, Partial, Removable ; standards ; Esthetics, Dental ; Female ; Gingival Recession ; therapy ; Humans ; Male ; Materials Testing ; Middle Aged ; Periodontal Prosthesis ; Silicone Elastomers ; chemistry