Antibacterial Polysiloxane Polymers and Coatings for Cochlear Implants.

Within this study, new materials were synthesized and characterized based on polysiloxane modified with different ratios of N-acetyl-l-cysteine (NAC) and crosslinked via UV-assisted thiol-ene addition, in order to obtain efficient membranes able to resist bacterial adherence and biofilm formation. These membranes were subjected to in vitro testing for microbial adherence against S. pneumoniae using standardized tests. WISTAR rats were implanted for 4 weeks with crosslinked siloxane samples without and with NAC. A set of physical characterization methods was employed to assess the chemical structure and morphological aspects of the new synthetized materials before and after contact with the microbiological medium.

Bis-(3-amino-2-pyridine) diselenide improves psychiatric disorders -atopic dermatitis comorbidity by regulating inflammatory and oxidative status in mice.

Suppressive effect of bis (3-amino-2-pyridine) diselenide (BAPD) on psychiatric disorders - atopic dermatitis (AD) comorbidity in mice was investigated. To sensitize the animals, 2,4-dinitrochlorobenzene (DNCB) was applied to their dorsal skin on days 1-3. Mice were challenged with DNCB on their ears and dorsal skin on days 14, 17, 20, 23, 26, and 29. BAPD and Dexamethasone were administered to the animals, from days 14-29, and skin severity scores and behavioral tests were determined. Oxidative stress and inflammatory parameters were evaluated on the dorsal skin of mice. Na+, K+-ATPase activity and corticosterone levels were determined in hippocampus/cerebral cortex and plasma of mice, respectively. BAPD improved cutaneous damage, scratching behavior, inflammatory and oxidative stress markers. BAPD showed anxiolytic- and antidepressant-like effects and restored Na+, K+-ATPase activity and corticosterone levels. The present study was performed using female mice due the susceptibility for this disease. But, the evaluation of AD model in male mice would help to verify whether the male gender has the same predisposition to present this pathology. Our data demonstrated the suppressive effect of BAPD on psychiatric disorders - AD comorbidity by regulating inflammatory and oxidative status in mice.

Efficacy and tolerability of an investigational nitric oxide-releasing topical gel in patients with molluscum contagiosum: A randomized clinical trial.

BACKGROUND: Although a variety of ablative, topical, and systemic therapies are used for molluscum contagiosum (MC), none has been well studied or approved by the US Food and Drug Administration. OBJECTIVES: To compare the efficacy and tolerability of topical SB206 (berdazimer sodium gel coadministered with hydrogel) with vehicle. METHODS: A 12-week, phase 2, multicenter, randomized, double-blind, vehicle-controlled clinical trial of topical SB206. RESULTS: A total of 256 patients (mean age, approximately 7 years) participated. Of patients who completed 12 weeks of treatment (n = 217), all MC lesions cleared in 20.0% of patients who received vehicle compared with 13.2%, 41.0%, and 35.1% of patients treated with twice daily SB206 4%, 8%, and 12%, respectively, and 41.9% of patients treated with once daily SB206 12%. Application-site erythema occurred in 10.6% of patients treated with SB206. Application-site reactions were the most common adverse events leading to treatment discontinuation, affecting 2 patients (approximately 4%) in each of the SB206 4%, 8%, and 12% twice daily groups and 0 patients in the vehicle or SB206 12% once daily groups. LIMITATIONS: A larger study is needed to confirm the efficacy of SB206 12% once daily and provide additional safety assessments. CONCLUSION: Of the doses studied, SB206 12% applied once daily provided the best balance between MC lesion clearance and tolerability for evaluation in a larger study.

Comparison of Cuspal Deflection and Microleakage of Premolar Teeth restored with Three Restorative Materials.

AIM: This study aimed to assess cuspal deflection and micro-leakage of mesio-occluso-distal (MOD) cavities in premolar teeth restored with three different tooth-colored restorative materials to determine the effect of polymerization shrinkage stress over time. MATERIALS AND METHODS: The MOD cavities (4 mm depth) were prepared in 30 sound human maxillary premolars. The teeth were randomly divided into three groups (n = 10). The teeth were then restored with Filtek P60 (group I), X-tra fil (group II), and Admira Fusion x-tra (group III). Cuspal deflection was assessed after 5 minutes, 24 hours, 48 hours, and 7 days by measuring the intercuspal distance. After restoring the teeth, they were subjected to 1,000 thermal cycles and were then immersed in 2% methylene blue for 24 hours. After vertical section of teeth, they were observed under a stereomicroscope to assess micro-leakage. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's honest significant difference (HSD) post hoc test. Friedman test was used to compare different time points in each group and nonparametric Mann-Whitney test was applied to assess microleakage (a < 0.05). RESULTS: The mean cuspal deflection was significantly different in the three groups (p < 0.001). The highest deflection was noted in Filtek P60 (14.8 ± 1.9) and the lowest was noted in Admira Fusion x-tra (7.4 ± 1.4 µm). Cuspal deflection significantly decreased after 7 days, but did not return to the baseline value. Admira Fusion x-tra showed significantly less deflection after 7 days (p < 0.001), but the other two groups were the same (p = 0.3). Microleakage was not significantly different among the three groups (p > 0.05). CONCLUSION: The lowest cuspal deflection was noted in Admira Fusion x-tra, although marginal microleakage was not significantly different among the groups. CLINICAL SIGNIFICANCE: As the lowest cusp deflection was noted in Admira Fusion x-tra, this restorative material can be suitable for esthetic restoration of extensive posterior cavities.

Effects of chlorine-based and quaternary ammonium-based disinfectants on the wettability of a polyvinyl siloxane impression material.

STATEMENT OF PROBLEM: Polyvinyl siloxane (PVS) impression materials must be cold disinfected before cast pouring to prevent cross-contamination among personnel and patients. However, disinfection may affect the ability of PVS impression materials to provide bubble-free stone surfaces because of the removal of surfactants. PURPOSE: The purpose of this in vitro study was to compare the water contact angles of a PVS impression material treated with either a quaternary ammonium-based (QAB) (DisCide Ultra) or a chlorine-based (CLB) (Dispatch) disinfectant for various exposure times. No disinfection and acetone-immersed (total surfactant removal) specimens were used as positive and negative controls. An additional purpose was to measure changes in the contact angles of the disinfected PVS impression material after applying a topical wetting agent. MATERIAL AND METHODS: Flat and disk-shaped PVS specimens (n=5/test condition) were fabricated and subsequently exposed to disinfectants for different times (1 minute, 5 minutes, 30 minutes, 6 hours, and 24 hours). After disinfection, the contact angle with distilled water was determined over a 3-minute period using dynamic contact analysis. The same contact angle measurements were repeated after a wetting agent was applied to the previously disinfected specimens. Contact angles were statistically compared using 2-way ANOVA. The Sidak post hoc test was used to perform pairwise simple contrast and effect comparisons (α=.05). RESULTS: The contact angle increased directly with disinfectant contact time. For the CLB product, the contact angle after 30-minute disinfection was not significantly different from that of 1 minute disinfection (P>.05). For the QAB product, exceeding 5-minutes of disinfection resulted in a significantly greater contact angle (P<.001). The application of a wetting agent made the disinfected PVS specimens less hydrophobic. CONCLUSIONS: A QAB disinfectant product is more effective at removing surfactant than a CLB disinfectant product. Therefore, a CLB disinfectant provides more working time and control. A wetting agent can reduce the hydrophobicity of a disinfected impression material if the duration of cold disinfection is less than 6 hours.

Technique to verify the accuracy of a definitive cast before the fabrication of a fixed dental prosthesis.

This report describes a straightforward technique for verifying the accuracy of a definitive cast by using a maximal intercuspation record fabricated from polyvinyl siloxane occlusal registration material. This precise verification method detects inaccurate casts before the dental prosthesis is fabricated, thus saving chairside and laboratory time while reducing the number of costly prosthesis remakes.

Characterization and Mechanism for the Protection of Photolytic Decomposition of N-Halamine Siloxane Coatings by Titanium Dioxide.

N-Halamine antibacterial materials have superior inactivation activities due to oxidative chlorine species. However, N-Cl bonds and bonds between N-halamine and substrates often decompose rapidly under UV irradiation, leading to unrecoverable loss of antimicrobial activity. In this study, titanium dioxide was covalently bonded onto N-halamine siloxane poly[5,5-dimethyl-3-(3'-triethoxysilylpropyl)hydantoin] (PSPH) via a sol-gel process. Experimental testing of the chlorinated cotton fabrics treated with TiO2/PSPH demonstrated that the residual oxidative chlorine in cotton-TiO2/PSPH-Cl was still effective for inactivating bacteria after 50 washing cycles and under UV light irradiation for 24 h. Quantum mechanical calculations found that TiO2 improves the UV stability of the PSPH-Cl system by increasing the activation barrier of the C-Si scission reaction responsible for the loss of the biocidal hydantoin moiety. SEM, XPS and FTIR spectra were used to characterize the coated cotton samples. Cotton-TiO2/PSPH-Cl samples exhibited good antibacterial activity against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895). The storage stability and washing stability of treated cotton fabrics were also investigated.

SILA-421 activity in vitro against rifampicin-susceptible and rifampicin-resistant Mycobacterium tuberculosis, and in vivo in a murine tuberculosis model.

Due to the emergence of multidrug-resistant and extensively drug-resistant tuberculosis (TB), there is an urgent need for new TB drugs or for compounds that improve the efficacy of currently used drugs. In this study, time-kill kinetics of SILA-421 as a single drug and in combination with isoniazid (INH), rifampicin (RIF), moxifloxacin (MXF) or amikacin (AMK) against Mycobacterium tuberculosis were assessed. Therapeutic efficacy in vivo in a mouse TB model was also studied. Further in vitro analysis was performed with a RIF-susceptible and RIF-resistant strains of M. tuberculosis. When used as a single drug, SILA-421 in vitro showed concentration-dependent and time-dependent bactericidal activity. SILA-421 also enhanced the activity of INH and RIF, resulting in synergy in the case of INH. Emergence of INH resistance following exposure to INH can be prevented by the addition SILA-421. SILA-421 had no additional value in combination with MXF or AMK. Furthermore, SILA-421 enhanced the activity of RIF towards a RIF-resistant strain and resulted in complete elimination of RIF-resistant mycobacteria. Unfortunately, in mice with TB induced by a Beijing genotype strain, addition of SILA-421 to an isoniazid-rifampicin-pyrazinamide regimen for 13 weeks did not result in enhanced therapeutic efficacy.

Use of a bite registration vinyl polysiloxane material to identify denture flange overextension and/or excessive border thickness in removable prosthodontics.

Vinyl polysiloxane (VPS) has multiple applications in prosthodontics. This article describes how a bite registration fast-set VPS material was used to identify length overextension and/or excessive border thickness of denture flanges. In addition, the advantages of VPS over conventional materials are presented.

Development and ultra-structure of an ultra-thin silicone epidermis of bioengineered alternative tissue.

Burn wound care today has a primary objective of temporary or permanent wound closure. Commercially available engineered alternative tissues have become a valuable adjunct to the treatment of burn injuries. Their constituents can be biological, alloplastic or a combination of both. Here the authors describe the aspects of the development of a siloxane epidermis for a collagen-glycosaminoglycan and for nylon-based artificial skin replacement products. A method to fabricate an ultra-thin epidermal equivalent is described. Pores, to allow the escape of wound exudate, were punched and a tri-filament nylon mesh or collagen scaffold was imbedded and silicone polymerisation followed at 120°C for 5 minutes. The ultra-structure of these bilaminates was assessed through scanning electron microscopy. An ultra-thin biomedical grade siloxane film was reliably created through precision coating on a pre-treated polyethylene terephthalate carrier.

Comparative evaluation of the effects of implant position, impression material, and tray type on implant impression accuracy.

PURPOSE: To evaluate the effect of implant position, impression, and tray material on the accuracy of implant impressions of edentulous arches with multiple implants. MATERIALS AND METHODS: Four experimental groups were produced; medium-viscosity polyvinyl siloxane (PVS) was used in 3 groups and polyether was used in 1 group. In PVS groups, different tray types were used; metal stock trays, custom acrylic tray, and full-arch perforated plastic trays. In polyether group, custom acrylic trays were used. The discrepancies in 3 dimensions were measured. RESULTS: The casts obtained exhibited small deviations (7.50-9.71 µm) from the master cast. There was no statistically significant difference between the polyether and PVS groups. Similarly, different tray materials did not produce any statistically significant discrepancies within the PVS groups. There was no significant difference among the groups when the accuracy of anterior implants were compared, but within-the-group comparisons showed that except group 1 (GR1), the posterior implants demonstrated more accuracy than anterior ones. CONCLUSIONS: Polyether and PVS can safely be used for the impressions of the edentulous arches with multiple implants and different tray types produce similar accuracy results.

Dimensional stability of a novel polyvinyl siloxane impression technique

AIM: To introduce a modification of the reline impression technique (MRIT), and compare the dimensional changes of impressions obtained by MRIT and by conventional reline impression technique (CRIT). METHODS: An acrylic resin tablet was milled by a CAD-CAM system to simulate three abutments (A, B and C) with different distances among them. The abutments were molded using both impression techniques. For MRIT, before completing the putty silicone polymerization, the relieve procedure was made by compression and it was immediately repositioned to complete the polymerization. Impressions were stored dry at room temperature for different periods (immediately, 1 h, 2 days and 7 days). The distances were obtained by scanning. The differences between the impressions and their respective matrix reference measurements were calculated to determine the dimensional changes. Data were subjected to ANOVA and Tukey's test (p<0.05). RESULTS: For AB and BC distances, there was no statistically significant difference between CRIT and MRIT (p=0.0597 and p=0.2167, respectively). For AC, there was statistically significant difference between the techniques for the immediate storage time (p=0.006). In general, for CRIT the material showed expansion, while for MRIT it showed contraction. CONCLUSIONS: It was verified that the addition silicon impressions obtained by both impression techniques showed dimensional stability, except for the immediate time-point...

Clinical performance of ormocer, nanofilled, and nanoceramic resin composites in Class I and Class II restorations: a three-year evaluation.

PURPOSE: This prospective long-term clinical trial evaluated and compared the three-year clinical performance of an ormocer, a nanofilled, and a nanoceramic resin composite with that of a microhybrid composite placed in Class I and Class II cavities. METHODS: Forty patients, each with four Class I and II restorations under occlusion, were enrolled in this study. A total of 160 restorations were placed, 25% for each material, as follows: an ormocer-based composite, Admira; a nanofilled resin composite, Filtek Supreme XT; a nanoceramic resin composite, Ceram X; and a microhybrid resin composite, Tetric Ceram. A single operator placed all restorations according to the manufacturers' instructions. Immediately after placement the restorations were finished/polished. Clinical evaluation was performed at baseline and at yearly intervals after placement by two other independent examiners using modified US Public Health Service (USPHS) criteria. The changes in the USPHS parameters during the three-year period were analyzed with the Friedman test. Comparison of the baseline scores with those at the recall visits was made using the Wilcoxon signed rank test. The level of significance was set at p < 0.05. RESULTS: All materials showed only minor changes, and no differences were detected between their performance at baseline and after three years. Only two ormocer, one nanofilled, and one microhybrid restorations in molars failed because of loss of retention. Regarding the clinical performance, there were no statistically significant differences among the materials used (p>0.05). CONCLUSIONS: The ormocer, nanofilled, and nanoceramic composites provided acceptable clinical performance over a three-year period.

In vivo caprine model for osteomyelitis and evaluation of biofilm-resistant intramedullary nails.

Bone infection remains a formidable challenge to the medical field. The goal of the current study is to evaluate antibacterial coatings in vitro and to develop a large animal model to assess coated bone implants. A novel coating consisting of titanium oxide and siloxane polymer doped with silver was created by metal-organic methods. The coating was tested in vitro using rapid screening techniques to determine compositions which inhibited Staphylococcus aureus growth, while not affecting osteoblast viability. The coating was then applied to intramedullary nails and evaluated in vivo in a caprine model. In this pilot study, a fracture was created in the tibia of the goat, and Staphylococcus aureus was inoculated directly into the bone canal. The fractures were fixed by either coated (treated) or non-coated intramedullary nails (control) for 5 weeks. Clinical observations as well as microbiology, mechanical, radiology, and histology testing were used to compare the animals. The treated goat was able to walk using all four limbs after 5 weeks, while the control was unwilling to bear weight on the fixed leg. These results suggest the antimicrobial potential of the hybrid coating and the feasibility of the goat model for antimicrobial coated intramedullary implant evaluation.

Effects of two disiloxanes ALIS-409 and ALIS-421 on chemoprevention in model experiments.

Morpholino-disiloxane (ALIS-409) and piperazino-disiloxane (ALIS-421) compounds were developed as inhibitors of multidrug resistance of various types of cancer cells. In the present study, the effects of ALIS-409 and ALIS-421 compounds were investigated on cancer promotion and on co-existence of tumor and normal cells. The two compounds were evaluated for their inhibitory effects on Epstein-Barr virus immediate-early antigen (EBV-EA) expression induced by tetradecanoyl-phorbol-acetate (TPA) in Raji cell cultures. The method is known as a primary screening test for antitumor effect, below the (IC50) concentration. ALIS-409 was more effective in inhibiting EBV-EA (100 µg/ml) and tumor promotion, than ALIS-421, in the concentration range up to 1000 µg/ml. However, neither of the compounds were able to reduce tumor promotion significantly, expressed as inhibition of TPA-induced tumor antigen activation. Based on the in vitro results, the two disiloxanes were investigated in vivo for their effects on mouse skin tumors in a two-stage mouse skin carcinogenesis study. The application of dimethyl-benzanthracene (DMBA; 390 nmol) as a tumor initiator was followed by exposure to TPA (1.7 nmol/l) as a tumor promoter. The experiments showed that ALIS-409 at a concentration of 85 nmol/l had a weak EBV-EA inhibitory effect in vitro and a moderate antitumor activity, compared to the positive control of DMBA plus TPA-treated mice. Flow cytometry by differential staining demonstrated interactions in co-cultures of MCF7 breast cancer and MRC5 human lung fibroblasts. The growth rate of tumor cells in mixed populations of MCF7 breast cancer and MRC5 normal fibroblast cells was reduced in the presence of ALIS-409, as compared to the control non-treated cell populations. The two disiloxanes were moderately-effective in chemoprevention in DMBA-induced and TPA-promoted in vivo tumor formation. Authors suggest that the inhibition of tumor cell and fibroblast interaction by ALIS409 might have some perspective in the development of anti-stromal therapy.

Effectiveness of isopropyl myristate/cyclomethicone D5 solution of removing cuticular hydrocarbons from human head lice (Pediculus humanus capitis).

BACKGROUND: In the treatment of human head lice infestation, healthcare providers are increasingly concerned about lice becoming resistant to existing pesticide treatments. Traditional pesticides, used to control these pests, have a neurological mechanism of action. This publication describes a topical solution with a non-traditional mechanism of action, based on physical disruption of the wax layer that covers the cuticle of the louse exoskeleton. This topical solution has been shown clinically to cure 82% of patients with only a 10-minute treatment time, repeated once after 7 days. All insects, including human head lice, have a wax-covered exoskeleton. This wax, composed of hydrocarbons, provides the insect with protection against water loss and is therefore critical to its survival. When the protective wax is disrupted, water loss becomes uncontrollable and irreversible, leading to dehydration and death. A specific pattern of hydrocarbons has been found in all of the head louse cuticular wax studied. Iso-octane effectively removes these hydrocarbons from human head lice's cuticular wax. METHODS: A method of head louse cuticle wax extraction and analysis by gas chromatography was developed. Human head lice (Pediculus humanus capitis) were collected from infested patients and subjected to any of three extraction solvents comprising either the test product or one of two solvents introduced as controls. A gas chromatograph equipped with a flame ionization detector (GC/FID) was used to determine the presence of hydrocarbons in the three head lice extracts. RESULTS: In the study reported herein, the test product isopropyl myristate/cyclomethicone D5 (IPM/D5) was shown to perform comparably with iso-octane, effectively extracting the target hydrocarbons from the cuticular wax that coats the human head louse exoskeleton. CONCLUSIONS: Disruption of the integrity of the insect cuticle by removal of specific hydrocarbons found in the cuticular wax appears to offer a mechanism for killing lice without the likelihood of encountering genetic resistance.

A functional open-tray impression technique for implant-retained overdenture prostheses.

Several implant impression techniques with different materials have been described in the literature. Generally, border molding, functional, and final impressions have been made with 3 different materials, which makes the procedure technique-sensitive and time-consuming. A combination of open-tray and functional impression techniques is described in this technical report. Border molding and functional impression procedures are made at the same time using a vinyl polysiloxane impression material, which makes this technique a simple and time-efficient alternative for clinicians.

[External prosthesis for defects and deformations of middle zone of face with the use of silicone elastomers].

Home made siloxan material <> for making external face prosthesis was introduced into clinical practice. Original technique of making external face prosthesis for defects and deformations of middle zone of face based upon making individual prosthetics according to esthetic requirements of the patient was developed. Stable staining of the composition <> by nontoxic pigments of the <> brand with the possibility of repetitive color corrections of the ready external prosthesis let to achieve high esthetic and functional result.