A Synergistic New Approach Toward Enhanced Antibacterial Efficacy via Antimicrobial Peptide Immobilization on a Nitric Oxide-Releasing Surface.

Despite technological advancement, nosocomial infections are prevalent due to the rise of antibiotic resistance. A combinatorial approach with multimechanistic antibacterial activity is desired for an effective antibacterial medical device surface strategy. In this study, an antimicrobial peptide, nisin, is immobilized onto biomimetic nitric oxide (NO)-releasing medical-grade silicone rubber (SR) via mussel-inspired polydopamine (PDA) as a bonding agent to reduce the risk of infection. Immobilization of nisin on NO-releasing SR (SR-SNAP-Nisin) and the surface characteristics were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy and contact angle measurements. The NO release profile (7 days) and diffusion of SNAP from SR-SNAP-Nisin were quantified using chemiluminescence-based nitric oxide analyzers and UV-vis spectroscopy, respectively. Nisin quantification showed a greater affinity of nisin immobilization toward SNAP-doped SR. Matrix-assisted laser desorption/ionization mass spectrometry analysis on surface nisin leaching for 120 h under physiological conditions demonstrated the stability of nisin immobilization on PDA coatings. SR-SNAP-Nisin shows versatile in vitro anti-infection efficacy against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus in the planktonic and adhered states. Furthermore, the combination of NO and nisin has a superior ability to impair biofilm formation on polymer surfaces. SR-SNAP-Nisin leachates did not elicit cytotoxicity toward mouse fibroblast cells and human umbilical vein endothelial cells, indicating the biocompatibility of the material in vitro. The preventative and therapeutic potential of SR-SNAP-Nisin dictated by two bioactive agents may offer a promising antibacterial surface strategy.

Mimicking the Endothelium: Dual Action Heparinized Nitric Oxide Releasing Surface.

The management of thrombosis and bacterial infection is critical to ensure the functionality of medical devices. While administration of anticoagulants is the current antithrombotic clinical practice, a variety of complications, such as uncontrolled hemorrhages or heparin-induced thrombocytopenia, can occur. Additionally, infection rates remain a costly and deadly complication associated with use of these medical devices. It has been hypothesized that if a synthetic surface could mimic the biochemical mechanisms of the endothelium of blood vessels, thrombosis could be reduced, anticoagulant use could be avoided, and infection could be prevented. Herein, the interfacial biochemical effects of the endothelium were mimicked by altering the surface of medical grade silicone rubber (SR). Surface modification was accomplished via heparin surface immobilization (Hep) and the inclusion of a nitric oxide (NO) donor into the SR polymeric matrix to achieve synergistic effects (Hep-NO-SR). An in vitro bacteria adhesion study revealed that Hep-NO-SR exhibited a 99.46 ± 0.17% reduction in viable bacteria adhesion compared to SR. An in vitro platelet study revealed Hep-NO-SR reduced platelet adhesion by 84.12 ± 6.19% compared to SR, while not generating a cytotoxic response against fibroblast cells. In a 4 h extracorporeal circuit model without systemic anticoagulation, all Hep-NO-SR samples were able to maintain baseline platelet count and device patency; whereas 66% of SR samples clotted within the first 2 h of study. Results indicate that Hep-NO-SR creates a more hemocompatible and antibacterial surface by mimicking two key biochemical functions of the native endothelium.

Calibration of silicone rubber rods as passive samplers for pesticides at two different flow velocities: Modeling of sampling rates under water boundary layer and polymer control.

There is a need to determine time-weighted average concentrations of polar contaminants such as pesticides by passive sampling in environmental waters. Calibration data for silicone rubber-based passive samplers are lacking for this class of compounds. The calibration data, sampling rate (Rs ), and partition coefficient between silicone rubber and water (Ksw ) were precisely determined for 23 pesticides and 13 candidate performance reference compounds (PRCs) in a laboratory calibration system over 14 d for 2 water flow velocities, 5 and 20 cm s-1 . The results showed that an in situ exposure duration of 7 d left a silicone rubber rod passive sampler configuration in the linear or curvilinear uptake period for 19 of the pesticides studied. A change in the transport mechanism from polymer control to water boundary layer control was observed for pesticides with a log Ksw of approximately 3.3. The PRC candidates were not fully relevant to correct the impact of water flow velocity on Rs . We therefore propose an alternative method based on an overall resistance to mass transfer model to adjust Rs from laboratory experiments to in situ hydrodynamic conditions. We estimated diffusion coefficients (Ds ) and thickness of water boundary layer (δw ) as adjustable model parameters. Log Ds values ranged from -12.13 to -10.07 m2 s-1 . The estimated δw value showed a power function correlation with water flow velocity. Environ Toxicol Chem 2018;37:1208-1218. © 2017 SETAC.

SIMONI (Smart Integrated Monitoring) as a novel bioanalytical strategy for water quality assessment: Part II-field feasibility survey.

Because it is impossible to chemically analyze all relevant micropollutants, the implementation of bioanalytical tools is essential to estimate ecological risks of chemical mixtures in regular water-monitoring programs. The first tier of the Smart Integrated Monitoring (SIMONI) strategy, which was described in part I, is based on the combination of passive sampling and bioanalytical measurements. Bioassay responses are compared with effect-based trigger values (EBT), and an overall SIMONI score on all bioassay data was designed to indicate environmental risks. The present study is focused on analyzing the feasibility of the hazard identification tier by evaluating results of 45 field campaigns at sites with different pollution profiles near the city of Amsterdam. A Daphnia assay was performed in situ, while silicon rubber or polar organic chemical integrative sampler (POCIS) extracts were tested with 4 nonspecific (daphnids, algae, bacteria, and cell culture) and 10 specific (9 Chemical Activated Luciferase Gene Expression [CALUX] assays and antibiotics scan) bioassays. Sensitivity analyses demonstrated the relevance of 2 classification variables in the SIMONI score formula on all bioanalytical data. The model indicated increased risks for the ecosystem at surface waters in greenhouse areas and undiluted wastewater-treatment plant (WWTP) effluents. The choice of testing specific bioassays on either polar or nonpolar passive sampling extracts is cost-effective and still provided meaningful insights on micropollutant risks. Statistical analyses revealed that the model provides a relevant overall impact assessment based on bioassay responses. Data analyses on the chemically determined mixture toxic pressure and bioanalytical methods provided similar insights in relative risk ranking of water bodies. The SIMONI combination of passive sampling and bioanalytical testing appears to be a feasible strategy to identify chemical hazards. Environ Toxicol Chem 2017;36:2400-2416. © 2017 SETAC.

Cytotoxicity of soft denture lining materials depending on their component types.

PURPOSE: To evaluate the difference in cytotoxicity of soft denture lining materials depending on their component types. MATERIALS AND METHODS: Ten commercially available soft denture lining materials (SDLM) consisting of five silicone-based materials and five acrylic-based materials were evaluated. For the MTT test, cured SDLM samples were extracted in a culture medium for 24 hours, and L-929 cells were incubated in the extracted medium for 24 hours. Cell viability was determined using a microplate reader and compared with those of the negative control, which were cultured in a culture medium without test material. Agar overlay test was performed for the cured SDLM samples according to International Organization for Standardization (ISO) 7405. RESULTS: Among silicone-based lining materials, GC Reline Soft, Mollosil plus, and Dentusil showed a cell viability of 107.2% ± 4.5%, 102.3% ± 2.84%, and 93.0% ± 8.0%, respectively, compared with the control. Mucopren and Sofreliner Tough displayed significantly lower cell viability (86.4% ± 10.3% and 81.5% ± 4.3%,respectively) compared with the control (P < .05). Among acrylic-based materials, Kooliner, Visco-gel, Soft liner, Dura Base, and Coe-Soft displayed cell viability of 99.2% ± 14.6%, 93.1% ± 9.5%, 89.1% ± 9.8%, 87.6% ± 7.9%, and 75.9% ± 15.7%, respectively, compared with the control. Dura Base and Coe-Soft displayed significantly lower cell viability compared to the control. However, for all tested materials, cell viability exceeded the requirement limit of 70% specified in ISO 10993-5. In the agar overlay test, all five silicone-based materials and acrylic-based Kooliner were ranked as "noncytotoxic." However, Visco-gel was ranked as "mildly cytotoxic," and Soft liner, Coe-Soft, and Dura Base were ranked as "moderately cytotoxic." CONCLUSION: When an acrylic-based soft denture lining material is used, the possibility of a cytotoxic effect should be considered.

Biomechanical properties of nano-TiO(2) addition to a medical silicone elastomer: the effect of artificial ageing.

OBJECTIVES: The aim of this study was to evaluate the effect of TiO2 nanoparticles on the mechanical and anti-ageing properties of a medical silicone elastomer and to assess the biocompatibility of this novel combination. METHODS: TiO2 (P25, Degussa, Germany) nanoparticles were mixed with the silicone elastomer (MDX4-4210, Dow Corning, USA) at 2%, 4%, and 6% (w/w) using silicone fluid as diluent (Q7-9180, Dow Corning, USA). Blank silicone elastomer served as the control material. The physical properties and biocompatibility of the composites were examined. The tensile strength was tested for 0% and 6% (w/w) before and after artificial ageing. SEM analysis was performed. RESULTS: TiO2 nanoparticles improved the tensile strength and Shore A hardness of the silicone elastomer (P<0.05). However, a decrease in the elongation at break and tear strength was found for the 6% (w/w) composite (P<0.05). All the ageing methods had no effect on the tensile strength of the 6% (w/w) composite (P>0.05), but thermal ageing significantly decreased the tensile strength of the control group (P<0.05). Cellular viability assays indicated that the composite exhibited biocompatibility. CONCLUSIONS: We obtained a promising restorative material which yields favourable physical and anti-ageing properties and is biocompatible in our in vitro cellular studies.

[Cytotoxicity of a new type silicone rubber for maxillofacial prosthesis: an in vitro evaluation].

This study evaluated the cytotoxicity of a new type silicone rubber for maxillofacial prosthesis, which was developed by the present authors. According to the GB/T16886. 5- 2003, the samples were prepared and tested with cell counting kit-8 (CCK-8) assay, the relative growth rate (RGR) was calculated, and morphology of L929 cells were observed by scanning electron microscope and phase contrast microscope. The results showed that RGR of L929 cells were 91.65% (24 h), 87.03% (48 h), 87.30% (72 h), respectively, and the level of cytotoxicity was grade 1. The L929 cells showed typical fusiform shape and their morphology did not changed significantly after 24 h, 48 h and 72 h. These data indicated that the newly-developed silicone rubber material, as a maxillofacial prosthesis material, should be a safe biomaterial.

Cytotoxicity of hard and soft denture lining materials.

The cytotoxicity of nine soft and hard lining materials (Mollosil Plus, Ufi Gel SC, Visco-gel, Molloplast-B, GC Tissue Conditioner, Vertex Rapid Simplified, GC Reline Hard, Vertex Self-Curing, Ufi Gel hard C) was evaluated using human gingival fibroblasts (HGFs). Twelve disk samples per lining material were prepared and incubated for 24, 48, 72, and 96 h. Cytotoxicity of each lining material's extract on cultured HGFs was measured using XTT assay. Data were analyzed using one-way ANOVA, post hoc Dunnett's T3 and Bonferroni tests at a significance level of p<0.05. At all incubation periods, all the hard lining materials (Vertex-SC, GC Reline Hard, Vertex-RS, and Ufi Gel hard C) showed cell viability higher than 90%. Among the soft lining materials, although there were no significant differences in cell viability among the different incubation periods for each lining material (p>0.05), autopolymerized acrylic-based GC Tissue Conditioner showed significantly lower cell viability than the other soft lining materials at each incubation period. Among the hard lining materials, there were no significant differences both among the materials and across all incubation periods for each lining material (p>0.05). In conclusion, all soft and hard liners exhibited good biocompatibility regardless of incubation time, except for GC Tissue Conditioner.

Effect of water storage and heat treatment on the cytotoxicity of soft liners.

OBJECTIVE: To evaluate the effect of water storage time on the cytotoxicity of soft liners. METHODS: Sample discs of soft liners Dentusoft, Dentuflex, Trusoft, Ufi-Gel-P and denture base acrylic resin Lucitone-550 were prepared and divided into four groups: GN: No treatment, G24: Stored in water at 37°C for 24 h; G48: Stored in water at 37°C for 48 h, GHW: Immersed in water at 55°C for 10 min. To analyse the cytotoxic effect, three samples of each group were placed in tubes with Dubelcco's Modified Eagle Mediums and incubated at 37°C for 24 h. During this period, the toxic substances were leached to the culture medium. The cytotoxicity was analysed quantitatively by the incorporation of radioactivity (3)H-thymidine checking the number of viable cells (synthesis of DNA). The data were statistically analysed using two-way anova and Tukey's honestly significant difference tests (α = 0.05). RESULTS: Treatments did not reduce the cytotoxicity effect of the soft liners (p > 0.05). It was found that Ufi-Gel-P had a non-cytotoxic effect, Trusoft had a slightly cytotoxic effect, Dentuflex had a moderated cytotoxic effect, Dentusoft alternated between slightly and non-cytotoxic effect, and Lucitone-550 had non-cytotoxic effect when stored in water for 48 h. CONCLUSION: The effect of water storage and the heat treatment did not reduce the cytotoxicity of the soft liners.

Cytotoxicity of orthodontic separating elastics.

BACKGROUND: Separating elastics may be cytotoxic to the interdental gingival tissues. Both latex and non-latex separating elastics are widely used and both types should be biocompatible. OBJECTIVE: To determine if latex and non-latex orthodontic separating elastics are cytotoxic. METHODS: The cytotoxicity of natural latex (Groups A, D and O) and non-latex (Group M) orthodontic separating elastics were determined by incubating 15 elastics of each type in Eagle's essential medium (MEM), removing the supernatant after 24, 48, 72 and 168 hours and adding it to cultures of L-929 mouse fibroblasts in growth medium (MEM plus glutamine, garamicine, fungizone, sodium bicarbonate, buffered saline and foetal calf serum). To verify the cell response in extreme situations, three additional groups were included: Group CC (cell control), consisting of L-929 cells not exposed to supernatants from the maintenance medium with the elastics; Group C+ (positive control), consisting of Tween 80; Group C- (negative control), consisting of phosphate buffered saline solution. The positive and negative controls were incubated in MEM maintenance medium for 24, 48, 72 and 168 hours and the extracted elutes were added to L-929 line cells incubated in the growth medium. The viability of the cells was determined with neutral red (dye-uptake method) at 24, 48, 72 and 168 hours. The data were analysed with the analysis of variance (ANOVA) and Tukey's multiple comparison test. The significance level was p < or = 0.05. RESULTS: The elastics in Groups A, D and O induced greater cell lysis at 72 hours compared to the other experimental times. There were statistically significant differences between the cytotoxicity of the elastics in Groups A, D and O in relation to Group CC for experimental times of 24, 48, 72 and 168 hours (p > 0.05). There was not, however, a statistically significant difference between Groups D and CC at 24 hours. CONCLUSION: The latex and non-latex orthodontic separating elastics tested were considered to be biocompatible.

Effects of a hindered amine light stabilizer and a UV light absorber used in maxillofacial elastomers on human gingival epithelial cells and fibroblasts.

STATEMENT OF PROBLEM: Ultraviolet light absorber (UVA) and hindered amine light stabilizer (HALS) retard sun-induced pigment degradation in silicone elastomeric maxillofacial prostheses. HALS inhibits polymer degradation and UVA dissipates UV radiation. Their effects on oral cells are unknown. PURPOSE: The purpose of this study was to evaluate the effects of UVA and HALS on membrane integrity, viability, and proliferation of human gingival fibroblasts and epithelial cells. MATERIAL AND METHODS: Tinuvin 123 (HALS) and Tinuvin 213 (UVA) were assessed for cytotoxicity, individually and in a 1:1 ratio (used in elastomers; HALS/UVA). The cells were exposed to HALS, UVA, or HALS/UVA (or control media containing only the diluent), and colorimetric assays measured membrane damage, viability, and proliferation. The data (% cytotoxicity or % control) were analyzed using 3-way cross-classified fixed effects ANOVA (alpha=.05). RESULTS: HALS did not negatively affect either cell type. UVA or HALS/UVA (>or= approximately 0.004%) decreased viability by >or=90% in both cell lines; lower concentrations decreased activity in epithelial cells while increasing it in fibroblasts. UVA or HALS/UVA damaged membranes of both cell lines, but epithelial cells were more resistant. UVA or HALS/UVA inhibited proliferation of both cell types similarly. There was a slight synergistic effect of HALS and UVA on membrane damage in both cell lines, but generally not on other parameters. CONCLUSIONS: Although it is unknown if HALS or UVA leaches from silicone elastomers in vivo, these data suggest that relative resistance of epithelial cells to UVA-induced membrane damage, and UVA's stimulation of fibroblast viability at some concentrations, might provide some protective effect.

Silicone rubber nipples: effects of sesame-oil extract on reproduction in mice.

The authors investigated a type of silicone rubber (SR) nipple for toxicity, caused by chemical migrants, on reproduction and pregnancy outcomes. They followed an extraction method (set forth in the 20th revised edition of the United States Pharmacopeia) in which sesame oil was a vehicle. They prepared the extract daily and administered it orally (50 ml/kg of body weight) into pregnant Swiss albino mice from gestation Day 0 until delivery. They gave a control group of mice the pure vehicle that was subjected to the same conditions. The authors recorded pregnancy weight gain, gestation period, litter size, stillbirths, and offspring sex ratio. They performed an enzyme-linked immunosorbent assay for pregnancy hormones (progesterone, estradiol, and prolactin) for each trimester and monitored birth weight, growth rate, and sex hormone levels (follicle-stimulating hormone, luteinizing hormone, and estradiol in females; testosterone in males) in offspring. The authors detected SR-extractable chemicals by means of gas chromatography and mass spectrometry. The decrease in weight gain from Day 6 of gestation until delivery and the shortness in the gestation period were significant in dams (p< or = .05). Newly born pups demonstrated a significantly (p < or = .05) lower body weight that continued with age, and this became highly significant (p< or = .01) from Day 6. Blood hormone levels in dams and offspring indicated no significance. In conclusion, the studied SR nipples indicated leachability, which could affect reproduction, without a manifest endocrine modulation.

Mechanical and biological comparison of latex and silicone rubber bands.

Latex rubber bands are routinely used to supply orthodontic force. However, because the incidence of allergic reactions to latex is rising, the use of nonlatex alternatives is increasing, and assessing the mechanical properties of the replacement products is becoming more important. The purposes of this study were to compare the mechanical properties of latex and silicone orthodontic rubber bands through static testing under dry and wet conditions, and to compare their biologic (cytotoxic) properties. Three brands of latex and 1 brand of silicone rubber bands were tested. When extended to 300% of the lumen diameter, the silicone group had an initial force equal to 83% of the product specifications; this was the lowest of the 4 groups. All 4 brands showed notable amounts of force degradation at the 300% extension when subjected to saliva immersion; this approximated a 30% force decay over 2 days. The latex bands all followed a similar pattern of force degradation, whereas the silicone bands showed a greater increase in force decay as the extension length increased. The silicone bands were less cytotoxic than 2 of the 3 types of latex. Although the silicone bands showed the least discrepancy of force degradation between air and saliva conditions, the amount of the force decay was the greatest. Therefore, great improvements in the physical properties of the silicone band are required before they can be considered an acceptable replacement for latex.

Development and characterization of an infection inhibiting urinary catheter.

Catheter associated bacturia is common in hospitals and nursing homes. The objective of this study was to develop an infection inhibiting urinary catheter for prolonged use. Methods were established to add chlorhexidine digluconate (CHG) to a silicone elastomer and to compression mold the material to form a urinary catheter. CHG was randomly dispersed in the elastomer to be released through elution. Samples of the material, with CHG concentrations ranging from 1 to 4% by weight, were tested for in vitro release characteristics over a 28 day period and for in vivo toxicity over a 7 day period. Release profiles followed a common pattern for each concentration: an initial peak during the first 24 hours was followed by a subsequent decline. CHG amounts released into the saline medium were directly related to the CHG concentration of the samples; 4% samples released the largest amounts and 1% samples released the least amounts. Both 3% and 4% CHG by weight samples released measurable amounts of CHG throughout the entire observation period, whereas 1% CHG by weight samples were depleted after 9 days, and 2% CHG by weight samples were depleted after 19 days. No samples were found to be toxic during in vivo evaluations. These studies suggest that CHG bearing silicone rubber urinary catheters could resist surface colonization and infection for extended periods without toxicity.

The chick chorioallantoic membrane as a novel in vivo model for the testing of biomaterials.

Current in vivo models for testing biomaterials are time and labor intensive as well as expensive. This article describes a new approach for testing biomaterials in vivo using the chorioallantoic membrane (CAM) of the developing chicken embryo, as an alternative to the traditional mammalian models. Fertilized chicken eggs were incubated for 4 days, at which time a small window was cut in the shell of the egg. After 1 week of incubation, the CAM received several test materials, including the endotoxin LPS, a cotton thread and a Silastic tubing. One day and 1 week later, the tissue response to the test materials was assessed using gross, histological, and scanning electron microscope evaluations. The inflammatory response of the chorioallantoic membrane to biomaterials was fully characterized and found to be similar to that of the mammalian response and was also seen to vary according to test materials. We also found that the structure and geometry of the test materials greatly influenced the incorporation of the samples in the CAM. The similarity of the tissue response of the CAM with the mammalian models, plus the low cost, simplicity, and possibility to continuously visualize the test site through the shell window make this animal model particularly attractive for the rapid in vivo screening of biomaterials.

Dentin barrier test with transfected bovine pulp-derived cells.

Growth kinetics of SV40 large T-antigen-transfected bovine pulp-derived cells on dentin were investigated. These cells were used in a dentin barrier test device, and the system was evaluated by testing a set of dental filling materials. Cells (120 cells/mm2) were seeded on dentin slices and incubated for up to 21 days. Cell proliferation was recorded using MTT assay. For cytotoxicity tests 3500 cells/mm2 were seeded on dentin discs, which were then incorporated into the dentin barrier test device. After 72 h preincubation test materials were applied. After a 24 h exposure with or without perfusion of the pulpal part of the test device, cell survival was evaluated using MTT assay. The cells revealed similar growth kinetics on dentin slices and on tissue culture plates. In cytotoxicity tests the cells were more sensitive toward the test materials than previously used three-dimensional cultures of human foreskin fibroblasts and as anticipated from clinical experience. Further improvement is expected by using three-dimensional cultures of pulp-derived cells.

Influence of long term silicone implantation on type II collagen induced arthritis in mice.

OBJECTIVES: The use of silicone implants in cosmetic and reconstructive surgery has been implicated in the development of autoimmune connective tissue diseases. Previous investigation of the influence of short-term silicone implantation using an experimental model of rheumatoid arthritis revealed no adverse influence upon disease despite the generation of autoantibodies against silicone bound proteins. This study was designed to examine the influence of long term implantation of different forms of silicone in collagen induced arthritis. METHODS: DBA/1 mice were surgically implanted with silicone elastomers, gel or oil nine months before immunisation with type II collagen emulsified in Freund's incomplete adjuvant. The incidence and severity of arthritis, antibodies to type II collagen, and serum cytokines were assessed and compared with sham implanted mice. Silicone implants were recovered, and autoantibodies to silicone bound proteins evaluated in arthritic and non-arthritic mice. RESULTS: Immunisation with CII/FIA resulted in a 30% arthritis incidence in sham implanted DBA/1 mice. Long term silicone implantation resulted in an increased incidence of arthritis, with a significant increase of 90% arthritis in animals implanted with silicone elastomers. Animals implanted with silicone elastomer also developed foreign body sarcomas during the study. Serum concentrations of interleukin 10 were increased in mice implanted with elastomers and immunised with CII/FIA, while interleukin 5 concentrations were significantly diminished in these mice. The production of autoantibodies to autologous silicone bound proteins, including anti-type I collagen antibody, was also attributed to the implantation of either silicone gel or silicone elastomer in type II collagen immunised animals. CONCLUSIONS: These data suggest that long term silicone implantation results in both the production of autoantibodies to connective tissue antigens and increased susceptibility to an experimental model of autoimmune disease.

[Comparative analysis of tissue reaction to acrylic resin materials in studies on Wistar strain rats]. / Analiza porównawcza reakcji tkankowej na tworzywa akrylowe w badaniach na szczurach szczepu Wistar.

The study takes up the issue of assessing rat tissue reaction to operatively inserted implants of different acrylic resin materials used in prosthetic dentistry. The materials subjected to analysis were polyacrylics: Vertex Soft, Vertex R.S., Vertex S.C., Superacryl and silicone material Molloplast B. The prolongation of life and the dynamic development of prosthetic treatment have caused removable dentures to be used longer and among more people. Polymerised acrylic resin material of these dentures is a potential pathogenic factor to the oral cavity mucosa which is in contact with it. As many as 20 to 70% of patients using removable acrylic dentures suffer from prosthetic stomatopathy. It is considered that the mucosa irritation may be caused by denture trauma, a mycotic infection or toxic action of some components of acrylic materials. Therefore the use of new generation acrylic materials in producing prosthetic dentures needs a precise assessment of undesirable local and systemic effects. A comparative analysis of the effect of correctly polymerised acrylic material on rat mucosa, parotid glands and lymphatic nodes was carried out. Systemic toxicity of these materials was assessed. Acrylic plates were prepared from the most often used acrylic resin materials in the Department of Prosthetic Dentistry PAM and a silicone material (these materials were polymerised precisely according to the producers instruction). Before implantation the plates underwent a thermodynamic analysis in order to ensure that the polymerisation process was carried out correctly and to determine thermal resistance of particular materials. Next sterile acrylic plates were implanted in rats under general anaesthesia. The animals were divided into 6 groups, 10 rats each. In four groups acrylic plates were implanted, in one group silicone material plates were implanted and it represented the comparative group, in one control group an incision of the buccal mucosa was made. The rats were observed during a period of 6 weeks, they were weighed every two weeks and no loss in body mass was noted (Tab. 1). After 6 weeks the rats were anaesthetised with ether and dissectioned. Biopsy specimens were taken from the buccal mucosa, porotid gland and lymphatic cervical nodes around the plates in order to make histological specimens. Blood samples were also taken to carry out blood cell counts and liver tests to determine eventual systemic toxicity of the studied acrylics. Histological specimens were stained with hematoxylin and eosin. In borne cases in order to precisely assess the intercellular substance other staining methods were used such as van Gieson, PAS and silvering of precollagen fibres on reticulum. Prepared specimens were assessed in a light microscope in magnification of 80 to 400. Basing on specimens of the control group an analysis of tissue reaction to the particular tested acrylic resin material was carried out. It was ascertained that the most irritative properties to the rat buccal mucosa were caused by self-cure acrylic material--Vertex S.C. This polymer caused in all rats in the tested group a reactive hypertrophy of cervical lymphatic nodes (Tab. 2 and Fig. 3). The least damaging effect on the surrounding tissues was caused by heat-cured acrylic resin material Superacryl (Fig. 4). The tested materials had no damaging effect on the rat parotid gland and did not have a toxic action on the internal organs.

Induction of type II collagen arthritis in the DA rat using silicone gels and oils as adjuvant.

The relative safety (or otherwise) of silicone gel filled breast implants remains a controversial issue. The Dark Agouti (DA) rat has been shown recently to have a high susceptibility for developing arthritis. This study determined the arthritogenic potential of silicone gel, silicone oil, and the low molecular weight octamethylcyclotetrasiloxane (D4), by either mixing it with bovine collagen II (BII) or by injecting silicone gel alone in DA rats. Three separate experiments were performed using 110 female DA rats with 10 rats per treatment group. The incidence of collagen induced arthritis was as follows: Experiment I (6 micrograms BII)- PBS = 0/10, silicone gel = 4/10, and IFA = 8/9; Experiment II (125 micrograms BII)- PBS = 0/10, silicone gel = 7/10, IFA = 10/10, 1,000 cs silicone oil = 3/10, D4 = 0/10, and 1% D4 in 1,000 cs silicone oil = 1/10; Experiment III (adjuvant alone)-IFA = 8/10, silicone gel = 0/10. Anti-BII antibodies were formed in most of the rats treated with either silicone gel or IFA mixed with BII and these groups of rats showed a positive DTH reaction. The PBS treated rats were negative for both anti-BII antibodies and DTH reaction. Silicone gel taken from a commercial breast implant thus is capable of mediating collagen induced arthritis in the DA rat. However, silicone gel alone does not appear to be arthritogenic.

Assessment of a model for measuring drug diffusion through implant-generated fibrous capsule membranes.

Fibrous tissue, which encapsulates subcutaneously implanted silastic, vinyl, polyurethane and Teflon discs in rats, has been isolated, characterized and tested for drug permeability in order to develop an in vitro model for determining the effect of this tissue on drug disposition from implant sites. With all materials, capsule tissue thickness and collagen content (approximately 59%) was consistent from 2 to 4 months after implantation. Silastic implants afforded the most consistent and usable tissue in terms of thickness and lack of vascularity, and these capsule membranes were used for determining the transport of three model compounds in an in vitro diffusion cell model. The rank ordering of permeability through these membranes was estrone (60.2 x 10(-6) cm s-1) > 3-O-methylglucose (18.7 x 10(-6) cm s-1) > dextran of molecular weight 70 000 (5.6 x 10(-6) cm s-1), which is consistent with expectations based on the molecular weights and partitioning behaviour of the model compounds. The results of these studies indicate that implant-generated encapsulating membranes can be successfully isolated and employed to study drug diffusion in an in vitro model, providing a direct assessment of the barrier properties of encapsulating membranes.