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At least 235 records · Page 13Linked to original sources

PubMed2007

Histological biocompatibility of new, non-absorbable glaucoma deep sclerectomy implant.

We performed this study to compare the intrascleral biocompatibility of three materials: non-absorbable hydrogel contact lens polymer, non-absorbable silicone rubber, and absorbable cross-linked sodium hyaluronate. Intrascleral implantation of three different materials was performed in 13 healthy, pigmented rabbits. Implants of methacrylic hydrogel, silicone rubber, and cross-linked sodium hyaluronate were implanted in 10, 8, and 8 eyes, respectively. The animals were euthanized at 7, 30, 180, and 360 days post implantation. The eyes were enucleated and immediately fixed in 10% buffered formalin. Semithin sections were cut and stained with hematoxylin-eosin. Light microscope analysis of the specimens was performed. The least severe inflammatory reaction was observed with cross-linked sodium hyaluronate implants. The number of inflammatory cells in proximity to methacrylic hydrogel and silicone implants at all periods of follow up was similar. The thickest fibrous capsule was observed with silicone implants (average, 28.38 +/- 11.17 microm). This area was thinner with methacrylic hydrogel implants (average, 14.90 +/- 5.57 microm) and was thinnest around sodium hyaluronate implants (average, 7.21 +/- 2.33 microm). For each type of implant, the wall on the conjunctival side of the fibrous capsule was significantly thicker than the wall on the choiroidal side. The space between the implant, scleral flap, and bed was filled soon after surgery with connective tissue rich in vessels. In our study, cross-linked sodium hyaluronate had the highest intrascleral biocompatibility. Although the inflammatory responses of the sclera to methacrylic hydrogel and silicone rubber were similar in nature, a thicker fibrous capsule was generated around silicone implants.

Animals↗

PubMed2001

Free polymeric bioligands in aqueous two-phase affinity extractions of microbial xylanases and pullulanase.

Two reversibly soluble-insoluble polymers (viz. Eudragit S-100 and alginate) were used as free macroaffinity bioligands in polyethylene glycol (PEG)/salt two-phase systems for separation of enzymes. Incorporation of Eudragit S-100 and alginate in the PEG phase led to considerable selectivity in separation of microbial xylanases and pullulanase, respectively. Xylanase from Aspergillus niger was recovered 93% with 56-fold purification, whereas the enzyme from Trichoderma reesei and Bacillus amyloliquefaciens was obtained with 93% activity recovery (31-fold purification) and 90% activity recovery (32-fold purification), respectively. From Bacillus acidopullulyticus pullulanase, 85% enzyme activity recovery with 44-fold purification was obtained. The approach described here shows the potential of developing into a general approach for use of reversibly soluble-insoluble macroaffinity ligand in two-phase affinity extraction.

Alginates↗

PubMed1984

Effect of the dentin smeared layer on tensile strength of cemented posts.

The tensile strengths for post lengths of 4 and 7 mm were compared in vitro with 3 different cementing media. In one group, the post preparation was rinsed with 5.25% NaOCl and in the other with 17% EDTA followed by 5.25% NaOCl. The EDTA-NaOCl flush had a profound effect when unfilled resin was used to cement the posts. A 4 mm post cemented with resin in the EDTA-NaOCl group was one and one-half times as retentive as a 7 mm post cemented with zinc phosphate and twice as strong as the 7 mm post with polycarboxylate cement. The 7 mm post cemented with the resin after the EDTA-NaOCl rinse was twice as resistant to displacement as the 7 mm post cemented with zinc phosphate and three times stronger than the polycarboxylate cement.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2006

Floating hot-melt extruded tablets for gastroretentive controlled drug release system.

The purpose of this study was to investigate the influence of sodium bicarbonate on the physicochemical properties of controlled release hot-melt extruded (HME) tablets containing Eudragit RS PO and/or Eudragit E PO. Acetohydroxamic acid and chlorpheniramine maleate were used as model drugs. Sodium bicarbonate was incorporated into the tablet formulations and the drug release properties and buoyancy in media for HME tablets and directly compressed (DC) tablets were investigated. The HME tablets prepared from the powder blend containing both Eudragit RS PO and sodium bicarbonate exhibited sustained release properties and the tablets floated on the surface of the media for 24 h. The cross-sectional morphology of the HME tablets showed a porous structure since CO(2) gas was generated due to the thermal decomposition of sodium bicarbonate in the softened acrylic polymers at elevated temperature during the extrusion process. In contrast, all DC tablets prepared in this study showed no buoyancy and rapid drug release in the dissolution media. The drug release rate from floating HME tablets was controlled by both the incorporation of Eudragit E PO into the matrix tablet and the diameter of the die used in the extrusion equipment. The drug release profiles and buoyancy of the floating HME tablets were stable when stored at 40 degrees C/75%RH for 3 months.

Algorithms↗

PubMed1976

Mucopolysaccharide complexes in the fibrous tissue surrounding hydrophilic polymers in subcutaneous implantation.

The biocompatibility of three types of hydrophilic poly-(glycol methacrylate) gels--homogeneous, microporous and macroporous--was investigated in an experimental subcutaneous implantation. The occurrence of mucopolysaccharide complexes formed by both hyaluronic acid and chondroitine sulphates was examined in the fibrous tissue which surrounds the implant and penetrates into it in the case of a macroporous polymer. In an early stage of investigation hyaluronic acid prevails, but with proceeding collagenization the chondroitine sulphate part becomes predominant.

Animals↗

PubMed2003

Studies on gynaecological hydrophilic lactic acid preparations, part 6: use of Eudragit E-100 as lactic acid carrier in intravaginal tablets.

Hydrophilic intravaginal tablets based on methylcellulose and containing lactic acid component with Eudragit E-100 undergo swelling in standard conditions. A high flow-limit of the gel that originates from the tablets as well as its dynamic viscosity should allow for the durable dosage form in the vagina. By choosing a 1:1 ratio of lactic acid to Eudragit E-100, it is possible to obtain tablets disintegrating into a gelform at physiological range of 3.8-4.4. An increase in the amount of lactic acid in the complex in relation to the polymer up to 2:1 and 3:1 ratios results in gels with a lower pH. These gels possess an acid reserve that might be ableto neutralise the excess of alkali present in severe vaginal infections.

Administration, Intravaginal↗

PubMed1994

Effect of filler content of restorative resins on retentive strength to acid-conditioned enamel.

In this in vitro study the retentive strength of enamel, either conventionally etched with a phosphoric acid gel or conditioned with an oxalic acid containing etching agent, was investigated. Five experimental restorative resins with filler contents between 0 and 78% by weight were polymerized on the etched enamel surfaces. In spite of the pronounced micromorphological differences of the patterns generated with the two etching agents, the bond strengths mediated were very similar. Application of an intermediate low-viscous or adhesive resin had no influence on bond strength. Exponential relationships were found between the filler content of the resins on the one hand and their flexural moduli and flexural strengths on the other. Significant exponential relations were also demonstrated between filler content and bond strength to the etched enamel surface. The linear relationship between mechanical properties of the resins and their bond strengths to etched enamel indicates that debonding occurred by cohesive failure in resin.

Acid Etching, Dental↗

PubMed1998

Carbodi-imide coupling of enzymes to the reversibly soluble insoluble polymer Eudragit S-100.

The coupling of proteins and enzymes to soluble-insoluble polymers by carbodi-imide can be performed by using numerous variations of the protocol. This protocol has been investigated for the coupling of five different enzymes, namely wheatgerm acid phosphatase, beta-glucosidase, beta-galactosidase, trypsin and xylanase, to an enteric methacrylate polymer Eudragit S-100. The following results were found. (1) The activity of the bioconjugate was critically dependent on the physical state of the polymer and the pH of the coupling reaction. For example, in the case of wheatgerm acid phosphatase, the activity of the bioconjugate was 49% when coupling was performed at pH 7.2 and 67% when coupling was performed at pH 4. 5. With beta-galactosidase the corresponding values were 57% and 23% and with beta-glucosidase they were 57% and 52% respectively. (2) In some cases, such as beta-glucosidase and beta-galactosidase, it might be necessary to remove excess carbodi-imide before the addition of the enzyme to the activated matrix. (3) In most of the cases investigated, a sig-nificant amount of the enzyme (more than 90%) could be bound to the matrix merely by adsorption. (4) More importantly, after the carbodi-imide coupling procedure, a sufficient fraction of the bound enzyme could be eluted off the matrix, indicating that this was merely adsorbed and not covalently coupled.

Acid Phosphatase↗

PubMed1982

Inhibition of mitochondrial substrate anion translocators by a synthetic amphipathic polyanion.

A synthetic polyanion (a copolymer of methacrylate, maleate, and styrene in 1:2:3 proportion with an average molecular weight of 10,000 dalton) inhibits the tricarboxylate, oxoglutarate, dicarboxylate, and adenine nucleotide translocators of rat liver mitochondria. The activity versus inhibitor concentration curves are sigmoidal. The inhibition of the oxoglutarate and tricarboxylate translocators by the polyanion is competitive, while that of the adenine nucleotide translocator is of mixed-type. The K1 values of the polyanion are the following: for oxoglutarate translocator 4.0 microM, tricarboxylate translocator 1.2 microM, and adenine nucleotide translocator 1.3 microM with ADP and 0.9 microM with ATP. It is suggested that the polyanion acts primarily by increasing the negative charge of the inner membrane at the outer surface, and the sensitivity of the translocators toward the polyanion depends on the number of negative charges of their substrates.

Adenine Nucleotides↗

PubMed2001

Molecular recognition by indoleacetic acid-imprinted polymers--effects of 2-hydroxyethyl methacrylate content.

Molecularly imprinted polymers for indole-acetic acid were prepared by co-polymerizing N,N-dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate. The dependence of the affinity and selectivity of the imprinted polymers on HEMA content was evaluated chromatographically. The affinity was improved by increasing the HEMA content; the selectivity of the imprinted polymer was best when the HEMA content was approximately 30%, irrespective of monomer content.

Biosensing Techniques↗

PubMed2006

A randomized controlled trial of the effectiveness of a one-step conditioning agent in sealant placement: 6-month results.

AIM: The objectives of this study were: to compare the retention of fissure sealants (sealants) placed on occlusal surfaces following the use of a self-etching priming agent and traditional acid etch; to compare the caries incidence of occlusal surfaces sealed using the two techniques; and to compare the ease of placement of sealant following the use of the two techniques, as assessed by subjects and operators. DESIGN: The study took the form of a randomized controlled trial conducted in UK National Health Service community dental service and dental hospital clinics. Sixty subjects were recruited to this study by seven dental professionals who placed sealants on lower permanent molar pairs. The technique used for enamel preparation prior to sealant placement on the right and left side of the lower arch was randomized. On one side of the lower arch, Xeno III was used to prepare the occlusal enamel, and on the other, phosphoric acid etch together with Prime & Bond was used. Opaque Delton was used to seal all surfaces. Subjects were blinded to the techniques used. The subjects and operators recorded their impressions of the techniques used on individual questionnaires. RESULTS: Forty-six (77%) of the 60 subjects were reviewed by the principal researcher after 6 months. The retention of the acid-etch group was significantly superior (P < 0.01), as was the caries preventive effect (P < 0.01). Subjects tended to report that placement of sealants was easier following enamel preparation with Xeno III (P = 0.085), and in the opinion of the operators, sealants were significantly easier to place when using Xeno III (P = 0.016). CONCLUSIONS: In view of the findings of this investigation, best practice for the placement of sealants remains enamel preparation with acid etch and the use of an intermediate bonding layer.

Acid Etching, Dental↗

PubMed1984

An SEM study of posts cemented with an unfilled resin.

Post preparations in two groups of endodontically treated anterior teeth were completed. In Group I, the preparation was rinsed with 2 ml of 5.25% NaOCL. In Group II, the preparation was rinsed with 1 ml of 17% EDTA, followed by 1 ml of 5.25% NaOCl. A plastic post was fitted and cemented with an unfilled resin. After polymerization, the teeth were decalcified in 5% nitric acid. The decalcified structured was dissolved away with 5.25% NaOCl, leaving a model of the cemented post. This was examined by SEM to determine the extent of resin penetration into the dentinal tubules. In Group I, most of the post was smooth, and there was penetration only in small, random areas. In Group II, there was penetration into the tubules the full length and circumference of the post. Such penetration provides a very strong mechanical lock that enhances the tensile strength of the cemented post. Removing the smeared layer and then cementing a post with a Bis-GMA resin results in greatly increased tensile strength, even with shorter posts.

Bisphenol A-Glycidyl Methacrylate↗

PubMedDate not supplied

Shear strength of sealants placed with non-rinse conditioning compared to a conventional acid etch-rinse technique.

The present study compared the shearing strength of a non-rinse conditioning (NRC) compomer sealant to that of a conventional sealant. Thirty molars and premolars were sectioned longitudinally. The resulting halves were divided into 4 groups. Cylinders of sealants were bonded to the sections using a gelatin capsule as a matrix, as follows: Group A (n = 15) NRC + Prime & Bond + Dyract Seal; Group B (n = 15) same as group A but with phosphoric acid and rinse; Group C (n = 15) conventional phosphoric acid + Helioseal; Group D (n = 15) NRC + Helioseal. After immersing the specimens in water for 7 days, the samples were mounted on the Instron testing machine at a 20 mm/min crosshead speed. The results were subjected to ANOVA with Scheffe test, with a significant level of .05. No shearing strength values could be obtained for the specimens of group D. Some cylinders separated from the enamel while still immersed in the water, and in others the adhesion was too low, and no readings could be observed. For all groups, failure occurred at the sealant-enamel interface. The mean value for group A was 5.33 MPa, significantly less than that of groups B 9.12 MPa and C 9.63 MPa (p < 0.006). No significant difference of the mean shear strength was evident between groups B and C. No rinse conditioning with Dyract Seal led to a considerably lower bond strength value than Dyract Seal and Helioseal with phosphoric acid and rinsing.

Acid Etching, Dental↗

PubMed2002

In vitro evaluation of the effect of a surfactant-containing experimental acid gel on sealant microleakage.

OBJECTIVE: The purpose of this study was to compare the effects of experimentally derived surfactant-containing acid gel with those of different surface-conditioning agents on microleakage of unfilled and filled sealants applied to permanent teeth following noninvasive and invasive procedures. METHOD AND MATERIALS: Four main groups of surface-conditioning agents (NRC; NRC + Prime&Bond NT; Email Preparator Blue; and experimental acid gel) were subdivided into 16 subgroups (n = 8). Subgroups were designed according to the surface preparation procedures applied (noninvasive and invasive) and fissure sealants used (Helioseal and Helioseal F). After application of the test materials, the specimens were subjected to thermocycling and then immersed in 0.5% basic fuchsin dye. Following sectioning, specimens were examined under a stereomicroscope and microleakage scores were assigned. RESULTS: Subgroups 9 (Email Preparator Blue + Helioseal), 11 (invasive + Email Preparator Blue + Helioseal), 13 (experimental acid gel + Helioseal), and 15 (invasive + experimental acid gel + Helioseal) showed no microleakage. The differences between those subgroups and subgroups 1 (NRC + Helioseal), 2 (NRC + Helioseal F), 3 (invasive + NRC + Helioseal), 4 (invasive + NRC + Helioseal F), 5 (NRC + Prime&Bond NT + Helioseal), and 6 (NRC + Prime&Bond NT + Helioseal F) were statistically significant. CONCLUSION: Email Preparator Blue and surfactant-containing experimental acid gel, combined with an invasive/noninvasive surface preparation procedure and Helioseal, significantly prevented microleakage.

Acid Etching, Dental↗

PubMedDate not supplied

Effects of different preparation techniques on the microleakage of compomer and resin fissure sealants.

PURPOSE: The aim of this study was to compare the microleakage of a compomer and resin sealant in vitro using different surface preparation techniques. METHODS: Microleakage of a compomer (Dyract Seal, DeTrey) and a resin sealant (Helioseal F, Vivadent) was investigated on 125 intact third molars. Materials and the surface preparation techniques were: Group 1--phosphoric acid (37%)+Helioseal F; Group 2--AlO2 air abrasion+Helioseal F; Group 3--nonrinse conditioner (NRC)+Prime&Bond+Dyract Seal; Group 4--phosphoric acid+Dyract Seal; Group 5--AlO2 air abrasion+Dyract Seal. RESULTS: Pretreatment with phosphoric acid produced the lowest microleakage scores when applied with compomer and resin fissure sealants and there was no statistical difference (P>.05). CONCLUSIONS: Compomer sealant used with a nonrinse conditioner (NRC) was not as successful as pretreatment with phosphoric acid etching, whereas AlO2 air abrasion pretreatment was ineffective in preventing microleakage in both sealants.

Acid Etching, Dental↗

PubMedDate not supplied

Bond strength and SEM observation of CO2 laser irradiated dentin, bonded with simplified-step adhesives.

This study investigated, mechanically and morphologically, whether the dentin surface irradiated by CO2 laser could be a possible adherent when bonded with simplified-step adhesives. Buccal enamel and cementum of extracted human premolars were removed to expose a flat dentin surface. The dentin surfaces were irradiated continuously with CO2 laser at 1.0 W. Before bonding with either a single-bottle adhesive (Single Bond) or a self-etching priming system (Mega Bond), the irradiated dentin surface was treated as follows: no treatment, NaHCO3 powder abrasion and wet-grinding with 600-grit SiC paper. The treated dentin surfaces were bonded to resin composite with either of the two adhesives. Non-irradiated dentin surfaces were also used as control. Resin bonded specimens were stored in water at 37 degrees C for 24 hours and subjected to microtensile bond test. Additionally, to observe the resin/irradiated dentin interface, resin-bonded specimens were similarly prepared, sectioned into slabs, embedded in epoxy resin, polished with diamond pastes, sputter coated Au-Pd and examined with scanning electron microscopy (SEM). After SEM observation, the specimens were further polished with diamond paste to remove the Au-Pd sputter-coat, immersed in HCL and NaOCl and finally observed by SEM again. In the presence of carbonized dentin, microtensile bond strength drastically decreased but recovered to the control value by removing the carbonized dentin layer visually with SiC paper for both adhesive systems. However, the laser-affected dentin that remained on the bonded interface was easily dissolved with NaOCl and HCl.

Air Abrasion, Dental↗

PubMedDate not supplied

Influence of disinfectants on dentin bond strength of different adhesive systems.

The influence of water disinfectants used in dental unit waterlines on the dentin bonding of different adhesive systems was investigated by using push-out tests. Three hundred and twenty dentin disc specimens were prepared from caries-free human molars. In each specimen, a standardized conical cavity was prepared while cooling with water from a dental unit containing one of three different disinfectants (n=80 each group; A=control: water without disinfectant, B: Alpron neutral, C: Alpron mint, D: Dentosept P). Subsequent rinsing of the cavities was performed With the respective disinfectant. The cavities were filled with the following combinations of dentin adhesives and composites, resulting in 16 subgroups (n=20): Syntac Classic/Tetric Ceram, Clearfil Liner Bond 2V/Luxacore, OptiBond FL/Prodigy and Prime&Bond NT/Spectrum. After polishing the fillings, one half of each subgroup (n=10) was stored in water (37 degrees C) for 24 hours. The other half was stored in water (37 degrees C) for 180 days and additionally thermocycled (2000 cycles at 5/55 degrees C). The bond strength was then measured by push-out tests. Statistical analysis of the data was carried out using ANOVA and pairwise t-tests (Significance level p < or = 0.01). The disinfectants showed no significant influence on the loads required for debonding of Syntac Classic/Tetric Ceram, Clearfil Liner Bond 2V/Luxacore and OptiBond FL/Prodigy as compared to the controls. However, the use of disinfectants in the water supply of a dental unit decreased dentin bond strength in the specimens filled with Prime&Bond NT/Spectrum. Disinfectants in the water of dental unit waterlines may have an influence on dentin bonding, depending on the adhesive system used.

Amines↗

PubMed1982

Light and electron microscopic observations of glycogen in semi-thin sections employing GMA, Quetol 523 and methylmethacrylate.

The use of improved GMA-Quetol 523 or GMA-Quetol 523 methyl methacrylate (MMA) mixture as an infiltration medium for the histochemical demonstration of glycogen has been devised to facilitate embedding, sectioning and staining. An improved method of infiltration uses such mixtures with a double weight of QCU-1 as a catalyst. Since the double weight of catalyst prevents interference by bleeding of picric acid from tissue blocks into the resin mixtures, improved mixtures penetrate readily and completely into the tissue fixed in picric acid-formaldehyde-glutaraldehyde solution (PAFG). PAFG solution has been found suitable for the histochemical fixation of glycogen in semithin sections. In hepatocytes specific reaction products appeared a deep reddish-purple after periodic oxidation and Schiff's reaction (PAS reaction), which was lost in previous digestion by means of salivary deastase. Glycogen can be identified as a PAS positive area in semi-thin sections 0.2-0.3 micrometers thick under the light microscope. Identical reactions sites of such sections show a high contrast in electron microscopy without any staining by either heavy metals or osmium tetraoxide vapor. It was therefore demonstrated that total glycogen produced after PAS reaction was revealed distinctly with deep contrast precipitates. This method provides significant morphological data for the histochemical localization of glycogen.

Acrylates↗