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At least 631 records · Page 35Linked to original sources
PubMed1993

Characterization of enamel and dentin surfaces after removal of temporary cement--study on removal of temporary cement.

Enamel and dentin surfaces of bovine teeth were characterized after mechanical and chemical removal of temporary cements. The surfaces were examined by scanning electron microscopy and X-ray microanalysis. Contact angles of distilled water were measured to monitor surface wettability. Mechanical removal with a dental probe did not completely remove all of the temporary cement from both enamel and dentin surfaces. These surfaces usually produced contact angles of distilled water greater than that on polished surfaces. Etching with thirty-seven percent phosphoric acid effectively removed the temporary cement that remained on enamel surfaces after mechanical removal but the etchant was not effective on dentin surfaces. Acid etching after mechanical removal of cement significantly decreased the contact angles of distilled water on enamel surfaces but the etchant only slightly improved contact angles of distilled water on dentin surfaces.

Acid Etching, Dental↗
PubMed1996

Contact angle of dentin bonding agents on the dentin surface.

Physical changes in the surface characteristics of dentin during bonding procedures were evaluated by measuring the contact angles of three standard liquids, to determine the surface free energy, and that of a commercially available dual cured dentin bonding agent dropped on the primed dentin surface. The commercial dentin bonding agent did not form a hemispherical shape on the ground dentin surface, probably because it penetrated into the smear layer due to the microcapillary effect. Not could the contact angle be measured on the dentin surfaces treated with any of four experimental primers, because the bonding agent rapidly spread over the primed dentin surface. It was concluded that the priming of the dentin surface after removing the smear layer served to increase the surface free energy and to improve the wettability of the bonding agent on the dentin.

Chemical Phenomena↗
PubMed2002

Surface properties and biocompatibility of nitrided titanium for abrasion resistant implant materials.

Corrosion, other related properties and biocompatibility of surface nitrided titanium were investigated to examine its possible use as an abrasion resistant implant material. The nitrided layer about 2 microm thick composed of TiN and Ti2N was formed on titanium by a gas nitriding method. The dissolved amount of titanium ion in SBF was as low as the detection limit of ICP, and that in the 1% lactic acid showed no significant difference from titanium. The tissue reaction of the cylindrical implant in soft tissue of rats showed no inflammation, and fine particles of 1 microm induced phagocytosis, which was similar to titanium. The implantation in the femor showed the new bone formed in direct contact with implants. All the results suggested that the wettability, corrosion resistance, S. mutans adhesion and biocompatibility were nearly equivalent to those of titanium. The surface of nitrided titanium was promising, with biocompatibility comparable with titanium, as an implant material such as for an abutment part of a dental implant, which requires high abrasion resistance.

Animals↗
PubMed1998

Platelet and cell interactions on gold sputter-deposited polymeric surfaces.

Surface treatment as gold sputter-deposited treatment onto various polymeric surfaces has been investigated to improve the cell-, tissue- and blood-compatibility. Surface treated samples were characterized by measurement of contact angle goniometer and electron spectroscopy for chemical analysis (ESCA). The contact angles on the gold-coated polymeric surfaces decreased from 95-65 degrees to around 50 degrees, i.e., increased hydrophilicity due to incorporation of gold thin layer. From the results of ESCA analysis of the modified polymeric surfaces, surface modification by the gold-sputter method was successfully performed. Morphology of the adhered platelets on the gold-coated polymeric surfaces showed lesser activating than control, and the number of adhered platelets surface modified samples decreased with decreasing water contact angle. Fibroblast cell adhesion and growth on the gold-coated polymeric surfaces were more active than those of control. It seems that surface wettability and surface chemistry of gold play important roles for platelet adhesion and cell adhesion, spreading and growth.

3T3 Cells↗
PubMedDate not supplied

Changes in water contact angles during the first phase of setting of dental impression materials.

PURPOSE: The purpose of this investigation was to examine the changes in wettability of dental impression materials during setting. This study compared the properties of the initial water contact of two different dental impression materials and their subsequent development during polymerization. MATERIALS AND METHODS: Two dental impression materials (Impregum Penta Soft and Aquasil) with different chemical compositions (polyether and polyvinyl siloxane, respectively) were investigated with respect to their changing wetting properties by time-resolved static contact angle measurements. Ten sets of measurements each were taken over a period of 400 seconds with 150 points of data each; the first pictures were used for further characterization of the initial interaction. RESULTS: With 73 degrees, Impregum Penta Soft exhibited a significantly lower contact angle, which stayed lower during the process of setting, compared to the silicone-based material. The initial interaction of the droplet showed a repulsive interaction of Aquasil with the water droplet. CONCLUSION: Impregum Penta Soft showed a more hydrophilic behavior during the process of setting compared to Aquasil and can therefore be expected to exhibit better flow properties. The method of time-resolved static contact angle measurements is a well-suited analytic instrument to monitor temporally changing wetting phenomena.

Dental Impression Materials↗
PubMed1992

Principles of adhesion.

Understanding interfacial phenomena has been of direct relevance and practical benefit to extending the use of dental adhesives. Both surface physics, which describes properties of the inorganic materials' interfacial zones from their actual phase boundaries toward the bulk phases of the solids, and surface chemistry, which describes phenomena at the solid/biological interface and beyond it into the variable organic environment, have been important. High-energy materials include solids that are very hard, have high melting points, strong intermolecular forces, and basically crystalline structures, such as dental enamel. Low-energy materials, such as dentinal collagen, salivary films, and the organic resins of restorative materials, are softer, lower melting, and have weaker intermolecular forces, poorer crystallinity, and surface energies generally less than 100 ergs/cm. It has been a properly renewed emphasis on wetting of dental surfaces and their modification by primer coats, displacing or mixing with water and adsorbed proteinaceous films, that has promoted the success of many recently developed fourth-generation dentin adhesives. Their improved wettability for biological phases correlates directly with their better infiltration and anchoring of composites.

Acid Etching, Dental↗
PubMed2005

Hydrophilic vinyl polysiloxane impression materials.

VPS impression materials that contain a surfactant cannot be considered as hydrophilic, rather they are probably less hydrophobic. More VPS products that contain surfactants are expected to be introduced to the market. It is yet to be proven that surfactant-containing VPS materials have a better wettability than polyether-based impression materials. The current data still indicates that polyethers are more hydrophilic. The less hydrophobic behavior of the surfactant-containing VPS may provide a significant advantage in clinical practice. Due to this advantage, the author suggests that clinicians using VPS as their preferred elastomeric impression material should consider switching to surfactant-containing VPS impression materials.

Dental Impression Materials↗
PubMed1994

Penetration of a dentin bonding agent into dentin.

PURPOSE: To examine how the priming agents of Scotchbond Multi-Purpose (SMP) influenced the wettability of collagen in the demineralized zone and hence the penetration and adaptation of its bonding monomers. MATERIALS AND METHODS: Freshly extracted bovine teeth were ground to dentin with SiC paper. SMP and Z100 resin were used. Shear bond testing was performed as well as scanning electron microscopic evaluation. RESULTS: In contrast to the manufacturer's instructions, a 26.3% increase in shear bond strength was obtained when a second coat of priming agent was applied. This increase was statistically significant at the 5% level of confidence. SEM examination of failed conventionally air dried (CAD) specimens showed the presence of voids in the demineralized layer. SEM examination of failed specimens prepared by a critical point drying (CPD) technique showed that these voids were filled with collagen fibrils. The CPD technique also clearly showed that collagen fibrils were incorporated in the unfilled resin. Although priming agents appear to facilitate the penetration of unfilled resin into the demineralized layer and the dentin tubules, areas of unincorporated collagen fibrils can be seen even after two or more applications of the priming agent.

Analysis of Variance↗
PubMedDate not supplied

Improving material properties by a simple gas-treatment procedure.

A simple, easy-to-use, room-temperature gas-treatment procedure improves the surface and bulk physical, chemical, and electrical properties of materials in a number of applications. Water wettability and a number of dielectric properties of various polymers, thin metal films, and porous carbon-based cathodes can be markedly changed by exposure for a few minutes to this gas treatment. This inexpensive technique can be used to chemically modify surface, and even bulk, electrical and physical properties of materials. These changes can then improve device performance. The technique can be easily inserted into ordinary manufacturing procedures.

Biocompatible Materials↗
PubMed1993

Introduction to plasma glow discharge treatment of dental implants.

As more practitioners are using implants in their practice, more questions have arisen regarding the use of these devices. One very important factor is the type of bone-implant interface obtained. The more inert and stable over time the metal is, the more we can control the overall success of the implant. Plasma glow discharge treatment is an ideal technique to increase the wettability of the metal and to insure a sound bone-implant interface. This article is an introduction to the use of plasma glow discharge treatment on dental implants.

Corrosion↗
PubMed1996

Two applications of transmucosal milled ceramic in implantology: preliminary clinical examples.

Two new implant systems, the Compound Implant and the TFM coping/abutment, are based on the association of titanium in the infrabony portion and a dense milled ceramic in the transgingival portion. The coating of zirconium ceramic on the transmucosal collar of the Compound Implant is particularly indicated for a single-stage surgical implant technique. The isolating properties and the high wettability of this material favor gingival healing and reduce the accumulation of plaque; the esthetic collar permits a supragingival or juxtagingival cervical margin favoring plaque control and minimizing the consequences of tissue remodeling. The hardness of the ceramic also allows it to undergo conventional prophylaxis with ultrasonic scalers without alteration of its surface quality. In addition to the above-mentioned advantages, the TFM coping/abutment, an implant-prosthesis connector in alumina ceramic, for use in a two-stage technique, provides electrogalvanic isolation of the implant, and personalized abutment preparation allows for simplified fabrication of an implant-supported prosthesis.

Biocompatible Materials↗
PubMed1997

Interaction of activated leukocytes with polymeric microspheres.

Three types of polymeric particles with different surface wettabilities, i.e., poly(methylmethacrylate) (PMMA), poly(methylmethacrylate-hydroxyethylmethacrylate) (P(MMA/HEMA)) and poly(methylmethacrylate)/poly(vinyl alcohol) PMMA/PVAL with a diameter of 1.5 microm were produced in this study These particles were incubated with blood samples obtained both from three patients undergoing cardiopulmonary bypass. In the blood samples taken before the bypass operations, there was considerable phagocytosis and/or adhesion of the PMMA particles, i.e., 14+/-4 particles per monocyte and 11+/-3 particles per neutrophil. While there was almost no phagocytosis and/or adhesion of the P(MMA/HEMA) and PMMA/PVAL particles. In the blood samples which were taken during bypass operations, phagocytosis and/or adhesion of PMMA microspheres increased significantly. The P(MMA/HEMA) and/or PMMA/PVAL particles adhered, or were even phagocytosed by the activated leukocytes in this case. Leukocytes activated during the bypass operations gradually returned to normal in about 24 h.

Cardiopulmonary Bypass↗
PubMed1997

Cell and platelet adhesions on plasma glow discharge-treated poly(lactide-co-glycolide).

Surface treatment, such as plasma glow discharge treatment, onto poly(lactide-co-glycolide) (PLGA) has been investigated to improve the cell-, tissue- and blood-compatibility. Surface-treated samples were characterized by measurement with a contact angle goniometer and electron spectroscopy for chemical analysis (ESCA). The contact angles on the plasma-treated PLGA surfaces decreased with increasing plasma exposure time from 92 degrees to about 30 degrees, i.e., increased hydrophilicity. From the results of ESCA analysis of plasma-treated films, the incorporation of oxygen molecules into plasma onto the PLGA surface was observed. Cell adhesion and growth on plasma-treated PLGA surfaces were more active than on the control. Furthermore, the maximum adhesion and growth of cells in moderate hydrophilicity were investigated. Morphology of the adhered platelets on the plasma-treated PLGA surface showed less activity than on the control, and the number of adhered platelets on the plasma-exposed PLGA sample decreased with decreasing water contact angle. It seems that surface wettability of PLGA plays an important role in cell adhesion, spreading and growth, and platelet adhesion.

3T3 Cells↗
PubMed1998

Amniotic membrane transplantation with or without limbal allografts for corneal surface reconstruction in patients with limbal stem cell deficiency.

OBJECTIVE: To examine whether amniotic membrane transplantation (AMT), in preparing the perilimbal stroma, enhances the success of allograft limbal transplantation (ALT). METHODS: Thirty-one eyes of 26 consecutive patients had cytologically proven limbal deficiency resulting from chemical burns (14 eyes); Stevens-Johnson syndrome, toxic epidermal necrolysis, or pseudopemphigoid (5 eyes); contact lens-induced keratopathy (3 eyes); aniridia (3 eyes); multiple surgical procedures (2 eyes); atopy (2 eyes); or an unknown cause (2 eyes). Based on the severity of limbal deficiency, group A (mild), comprising 10 eyes, received AMT alone; group B (moderate), comprising 7 eyes, received AMT and ALT; and group C (severe), comprising 14 eyes, received AMT, ALT, and penetrating keratoplasty. All patients except those in group A received continuous oral cyclosporine. RESULTS: Except for the 2 eyes with atopy, all amniotic membrane-covered surfaces showed rapid epithelialization (in 2 to 4 weeks) and reduced inflammation, vascularization, and scarring, and the surfaces became smooth and wettable. For the mean follow-up period of 15.4 months, 25 (83%) of 30 eyes showed visual improvement, consisting of 6 or more lines (13 eyes), 4 to 5 lines (6 eyes), or 1 to 3 lines (6 eyes). Visual improvement decreased with the severity of limbal deficiency from 8 (100%) of 8 eyes in group A to 5 (71%) of 7 eyes in group B and 11 (79%) of 14 eyes in group C. In group C, corneal graft rejection occurred in 9 (64%) of 14 eyes, and reversible early limbal allograft rejection was noted in 3 (14%) of 21 eyes of groups B and C. CONCLUSIONS: For partial limbal deficiency with superficial involvement, AMT alone is sufficient and hence superior to ALT because there is no need to administer cyclosporine. For total limbal deficiency, additional ALT is needed, and AMT helps reconstruct the perilimbal stroma, with reduced inflammation and vascularization, which collectively may enhance the success of ALT.

Adult↗
PubMed1999

Biocatalytic nerve agent detoxification in fire fighting foams.

Current events across the globe necessitate rapid technological advances to combat the epidemic of nerve agent chemical weapons. Biocatalysis has emerged as a viable tool in the detoxification of organophosphorus neurotoxins, such as the chemical weapons VX and sarin. Efficient detoxification of contaminated equipment, machinery, and soils are of principal concern. This study describes the incorporation of a biocatalyst (organophosphorus hydrolase, E.C. 3.1.8.1) into conventional formulations of fire fighting foam. The capacity of fire fighting foams to decrease volatilization of contained contaminants, increase surface wettability, and control the rate of enzyme delivery to large areas makes them useful vehicles for enzyme application at surfaces. The performance of enzyme containing foams has been shown to be not only reproducible but also predictable. An empirical model provides reasonable estimations for the amounts of achievable surface decontamination as a function of the important parameters of the system. Theoretical modeling illustrates that the enzyme-containing foam is capable of extracting agent from the surface and is catalytically active at the foam-surface interface and throughout the foam itself. Biocatalytic foam has proven to be an effective, "environmentally friendly" means of surface and soil decontamination.

Aryldialkylphosphatase↗
PubMed1996

Preparation and characterization of high-surface-area polymer substrates for microcalorimetry.

The preparation and characterization of high-surface-area polymeric substrates suitable for the microcalorimetry of protein adsorption are described. High-surface-area polystyrene, poly(styrene-co-butyl methacrylate) and poly(styrene-co-allyl alcohol) were prepared by adsorbing polymer from solution onto fumed silica. Verification of adsorption of polystyrene by silica was determined by noting peak shifts of the surface silanol group in the infrared. The amount of polymer adsorbed was determined from adsorption isotherms. The minimum thickness of polystyrene required to mask silicon oxide properties was found to be that thickness at which contact angles became constant, about 35 A. Polymer densities were measured. Water contact angles on each polymer surface indicate that poly(styrene-co-allyl alcohol) has the surface most wettable by water. Polymer-water interfacial energies were estimated from pendant drop results and a harmonic mean equation along with contact angles. Two methods were used to estimate the polar and dispersion components of the three polymers. Both methods predicted polystyrene to have the highest interfacial energy against water, and one method predicted poly(styrene-co-allyl alcohol) to have the lowest. A Wilhelmy plate study verified the change in interfacial properties as a function of contact time with water. A study of the heats of adsorption of lysozyme by each substrate using a modified Tien-Calvet microcalorimeter demonstrated the suitability of the substrates for microcalorimetry.

Adsorption↗
PubMed1996

Wear testing of materials and surfaces for total knee replacement.

A simple wear test was investigated for evaluating the wear and damage of material pairs when used in total knee replacement. The test consisted of an axially loaded metallic femoral indentor and a reciprocating ultrahigh molecular weight polyethylene (UHMWPE) flat disk that represented the tibial component. A number of variables were studied including the effect of conformity by varying the radii of the femoral surface, distilled water or serum as a lubricant, different femoral materials, and different types of UHMWPE. In general, the different morphologies of the surface wear of the UHMWPE were similar to those seen on retrieved total knee replacements. Increased conformity with a cylindrical indentor gave a reduced wear rate initially, compared with that of the lower conformity spherical indentor. However, the wear rates were similar subsequent to this initial wearing in phase. Transfer films of UHMWPE were observed on the cobalt-chrome indentors for both serum and distilled water lubrication, although this film was more extensive for distilled water. The lowest wear rate was observed when oxidized zirconium was used on the femoral side, which was attributed to greater wettability, surface hardness, and immunity to oxidative wear. Tests using cobalt-chrome femoral cylinders and different grades of UHMWPE showed different wear rates. Of these PEs, GUR 415 showed less wear than both RCH 1000 and UHMWPE containing numerous fusion defects. For the latter, wear was attributed to a fatigue mechanism, although in most cases it was associated with surface phenomena rather than subsurface cracking. However, in some specimens of UHMWPE subsurface crack propagations occurred with defects. The test method is discussed in relation to its applicability to the evaluation and comparison of bearing materials and surfaces, with particular application to total knee replacements.

Alloys↗
PubMed1998

Platelet adhesion onto chargeable functional group gradient surfaces.

Functional group gradients were prepared on low-density polyethylene (PE) sheets. The surface density of grafted functional groups was gradually changed along the sample length by way of corona discharge treatment with gradually increasing power following graft copolymerization of acrylic acid (AA), sodium p-styrene sulfonate (NaSS), or N,N-dimethyl aminopropyl acrylamide (DMAPAA). AA and NaSS are negatively chargeable and DMAPAA is positively chargeable in phosphate-buffered saline or plasma solution at pH 7.3-7.4. The prepared functional group gradient surfaces were characterized by measurement of the water contact angle, by electron spectroscopy for chemical analysis, and by Fourier transform infrared spectroscopy in the attenuated total reflectance mode. All these measurements indicated that the functional groups were grafted onto the PE surfaces with gradually increasing density. The platelets adhered to the functional group gradient surfaces along the sample length were counted and observed by scanning electron microscopy. It was observed that the platelet adhesion to the gradient surfaces decreased gradually with the increasing surface density of functional groups. This may be related to the hydrophilicity of the surfaces. The DMAPAA-grafted surface showed a large amount of platelet adhesion, probably due to its positive charge character, while the AA-grafted surface, which is charged negatively, showed poor platelet adhesion. However, the NaSS-grafted surface, which is also charged negatively, showed a relatively large amount of platelet adhesion. This may be associated with the existence of an aromatic ring close to the ionizable group in NaSS. It seems that surface functional groups and their charge character, as well as wettability, play important roles for platelet adhesion.

Acrylates↗