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PubMed1995

Bond strengths of glass ionomers using a dentin adhesive.

PURPOSE: To determine the effect of All-Bond 2 adhesive on the shear bond strengths to dentin of Fuji II LC, Photac-Fil, and Vitremer. MATERIALS AND METHODS: The occlusal surfaces of 60 extracted human third molars were ground flat to expose dentin and were polished to 600 grit. The teeth were randomly assigned to six groups (n = 10). In three groups, dentin was treated using the conditioner or primer recommended by the manufacturer. In the remaining groups, dentin was treated with All-Bond 2 etchant, primer, and adhesive. Restorative materials were applied to the treated surfaces in gelatin capsule matrices and were light-cured. Specimens were thermocycled, and shear bond strengths were determined using a materials testing machine. RESULTS: The use of All-Bond 2 improved the mean bond strength of Photac-Fil from 1.7 to 8.7 MPa, but decreased the bond strength of Vitremer from 7.3 to 5.5 MPa. The bond strengths of Fuji II LC were 7.5 and 7.9 MPa, with and without the use of All-Bond 2, respectively. ANOVA and Duncan's multiple range test showed that only the difference for Photac-Fil was statistically significant.

Composite Resins↗

PubMed1998

Flow-cytometric analysis of leukocyte activation induced by polyethylene-terephthalate with and without pyrolytic carbon coating.

Leukocyte activation is one test for the evaluation of blood-materials interaction. The expression of adhesion molecules analyzed by flow cytometry provides a simple method to evaluate leukocyte activation by biomaterials: any change in these molecules can be predictive of the inflammatory activity of the materials. In this study the contact between leukocytes and uncoated polyethylene terephthalate or pyrolytic carbon-coated polyethylene terephthalate (PET and PET-PC, respectively) was inspected by analyzing whether the expression of some adhesion molecules involved in leukocyte activation, namely LFA-1 (CD11a/ CD18), Mac-1/CR3 (CD11b/CD18), and LECAM-1 (CD62L) can be modified. By flow cytometry expression of the adhesion molecules can be studied separately on lymphocytes and myeloid cells. The materials tested reduced the total numbers of both leukocytes and neutrophils, although not significantly. Neither PET nor PET-PC changed the expression of the adhesion molecules in lymphocytes: this suggests that no specific immune response is stimulated. On the contrary, statistically significant changes were observed for monocytes and granulocytes: the percentage of cells expressing Mac-1 and the density of such antigens on cell membranes increased while the percentage of LECAM-1 positive cells decreased. Similar changes were observed when the cells underwent the inflammatory stimulus provided by an in vitro challenge with bacterial endotoxin. Our results demonstrated that polyethylene terephthalate activates leukocytes by modifying the expression in neutrophils of the molecules involved in the early phase of the inflammatory response. Even after coating PET with pyrolytic carbon, the ability of this material to activate circulating leukocytes was maintained.

Biocompatible Materials↗

PubMed2004

Physical properties of different composites.

The purpose of this study was to determine the flexural strength (FS), flexural modulus (FM), depth of cure (DC), polymerization shrinkage (PS), and microhardness (VH) of the following composites: Two packable composites--Filtek P-60 and Solitaire 2; One ion-releasing composite--riston AT; and Two hybrid composites--Charisma and Filtek Z-250. Data of the different tests conducted were obtained as follows: FS and FM data were determined with a universal-testing machine; Polymerization shrinkage was determined using the apparatus of Watts and Cash; Depth of cure was measured with a micrometer (Mitotuyo, UK); and Microhardness was measured with a Shimadzu Microhardness tester (500 g, 15 seconds). All data of the different tests were statistically analyzed by one-way variance analysis (ANOVA), which yielded the following results: Filtek Z-250 showed the statistically highest flexural strength and modulus values. Solitaire 2 exhibited the highest shrinkage, while the volumetric shrinkage results of Filtek Z-250 and Filtek P-60 ranked the lowest. For depth of cure, there were no statistically significant differences among all materials tested (p<0.05). Microhardness results revealed the following tendency: Filtek Z-250 = Filtek P-60 > Ariston AT = Solitaire 2 = Charisma.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1989

Residual stress in several ceramometal systems.

Residual stress caused by a mismatch of alloy-porcelain thermal contraction can contribute to clinical failure of a ceramometal restoration. This investigation assessed thermal compatibility of three ceramometal alloys and two opaque porcelains. Thermal expansions of the alloys and porcelains were measured by using a straight push-rod dilatometer. Porcelain glass transition temperatures and expansion values were derived from length-versus-temperature curves. Residual stress states in alloy-porcelain pairs were assessed by comparing expansion values of the components at the porcelain glass transition temperatures. Above that temperature the porcelain viscosity is low and stress relief is possible, whereas below the glass transition the porcelain acts as a stress-supporting solid. Expansion values were in general agreement and glass transition temperatures were slightly lower than values previously reported for similar materials. Alloy-porcelain thermal compatibility for the materials tested appeared more dependent on the opaque porcelain than the alloy.

Chemical Phenomena↗

PubMed2003

Fluoride release from orthodontic cements-effect of specimen surface area and depth.

OBJECTIVE: The aims of this in vitro study were firstly to compare fluoride release from a disc model of two orthodontic cements with various surfaces varnished, reducing the surface area by 25, 50 and 75%; secondly, to measure the fluoride release from previously exhausted discs of the same cements following removal of various depths of surface material. METHODS: Forty discs of each cement, Fuji Ortho LC and Ultra Band-Lok, (6mm diameter by 3mm) were divided into two groups of 20 discs each. For each material, the first group was divided further into four groups of five discs, one group acting as control, while the other three groups were varnished reducing the surface area by 25, 50 and 75%, respectively. The second group was exhausted initially over a 60 day pre-experimental period and was subsequently divided into four groups of five discs, one group acting as control. The other three groups had material ground from one of the flat surfaces, to depths of 10, 100 or 1000 microm, to reveal a fresh surface. In both studies, the discs were immersed either daily (up to day 20) or twice weekly (up to day 60) in fresh 2ml aliquots of deionised water. The fluoride concentration in the deionised water was measured at the end of the experimental period. RESULTS: For each cement, the relationship between the cumulative fluoride release and the percentage of the surface covered was clearly non linear at both 5 and 60 days. Fuji Ortho LC proved to release significantly greater amounts of fluoride at both 5 days and 60 days compared with Ultra Band-Lok. The results for Ultra Band-Lok were also significant when compared to the control group, but significantly less fluoride was released when compared with Fuji Ortho LC. When comparing the 25 and 50% covered discs, the amount of fluoride released was not significantly different for both cements. Furthermore, the relationship between fluoride release and depth was clearly non linear for both cements. CONCLUSIONS: For the materials tested in this study, reducing the surface area of the discs did not reduce the cumulative fluoride release in a linear fashion. In addition, the previously exhausted discs began to release fluoride again, but this fell to concentrations similar to the control discs after the initial 5-day period for both cements. This suggests that further traces of previously unreleased fluoride had become available from the subsurface of these cements. The pattern of fluoride release was similar for all models tested.

Acrylic Resins↗

PubMed2005

Decontamination assessment of Bacillus anthracis, Bacillus subtilis, and Geobacillus stearothermophilus spores on indoor surfaces using a hydrogen peroxide gas generator.

AIMS: To evaluate the decontamination of Bacillus anthracis, Bacillus subtilis, and Geobacillus stearothermophilus spores on indoor surface materials using hydrogen peroxide gas. METHODS AND RESULTS: Bacillus anthracis, B. subtilis, and G. stearothermophilus spores were dried on seven types of indoor surfaces and exposed to > or =1000 ppm hydrogen peroxide gas for 20 min. Hydrogen peroxide exposure significantly decreased viable B. anthracis, B. subtilis, and G. stearothermophilus spores on all test materials except G. stearothermophilus on industrial carpet. Significant differences were observed when comparing the reduction in viable spores of B. anthracis with both surrogates. The effectiveness of gaseous hydrogen peroxide on the growth of biological indicators and spore strips was evaluated in parallel as a qualitative assessment of decontamination. At 1 and 7 days postexposure, decontaminated biological indicators and spore strips exhibited no growth, while the nondecontaminated samples displayed growth. CONCLUSIONS: Significant differences in decontamination efficacy of hydrogen peroxide gas on porous and nonporous surfaces were observed when comparing the mean log reduction in B. anthracis spores with B. subtilis and G. stearothermophilus spores. SIGNIFICANCE AND IMPACT OF THE STUDY: These results provide comparative information for the decontamination of B. anthracis spores with surrogates on indoor surfaces using hydrogen peroxide gas.

Bacillaceae↗

PubMed2003

Comparison of bioactive glass, mineral trioxide aggregate, ferric sulfate, and formocresol as pulpotomy agents in rat molar.

Bioactive glass (BAG) is often used as a filler material for repair of dental bone defects. Although there is evidence of osteogenic potential of this material, it is not clear yet whether the material exhibits potential for dentinogenesis. Hence, the aim of the present study was to evaluate BAG as a pulpotomy agent and to compare it with three commercially available pulpotomy agents such as formocresol (FC), ferric sulfate (FS), and mineral trioxide aggregate (MTA). Pulpotomies were performed in 80 maxillary first molars of Sprague Dawley rats, and pulp stumps were covered with BAG, FC, FS, and MTA. Histologic analysis was performed at 2 weeks and then at 4 weeks after treatment. Experimental samples were compared with contra-lateral normal maxillary first molars. At 2 weeks, BAG showed inflammatory changes in the pulp. After 4 weeks, some samples showed normal pulp histology, with evidence of vasodilation. At 2 weeks, MTA samples showed some acute inflammatory cells around the material with evidence of macrophages in the radicular pulp. Dentine bridge formation with normal pulp histology was a consistent finding at 2 and 4 weeks with MTA. Ferric sulfate showed moderate inflammation of pulp with widespread necrosis in coronal pulp at 2 and 4 weeks. Formocresol showed zones of atrophy, inflammation, and fibrosis. Fibrosis was more extensive at 4 weeks with evidence of calcification in certain samples. Among the materials tested, MTA performed ideally as a pulpotomy agent causing dentine bridge formation while simultaneously maintaining normal pulpal histology. It appeared that BAG induced an inflammatory response at 2 weeks with resolution of inflammation at 4 weeks.

Aluminum Compounds↗

PubMed2002

In vitro effects on MG63 osteoblast-like cells following contact with two roughness-differing fluorohydroxyapatite-coated titanium alloys.

The chances of integration between an implant and the surrounding bone tissue depend on the surface characteristics of the implant itself. Particularly, chemical composition and surface roughness of the material have emerged as crucial factors in affecting the behaviour of cells in contact with the material. Among various surfaces, calcium phosphate coatings seem to favour a rapid initial integration, but their dissolution by extracellular fluids raises some concern about the long-term stability at the bone-implant interface. Fluorinated apatites are known to be more stable than other ceramic coatings, but, at present, little is known on their effects on human cells. In this study, MG63 osteoblast-like cells were seeded onto two fluorohydroxyapatite (FHA)-coated titanium alloy (Ti6Al4V) materials differing in roughness, respectively, LR-FHA (Ra = 5.6 microm) and HR-FHA (Ra = 21.2 microm). Quantification of the cells in contact with the FHA-coated materials by conventional methods involved some technical difficulties, on which we report. Only the indirect esteem by the measure of total content of proteins and a procedure based on cell count, following a double enzymatic treatment to detach the cells, offered plain results, indicating no significant differences between cellular growth in contact with test materials and with plastic control. Differentiation and functionality of the cells were comparatively evaluated by analysis of alkaline phosphatase activity and osteocalcin production. As far as osteocalcin release is concerned, only slight variations were detected on FHA-coated materials in comparison with the control. Both types of coatings showed a significant increase in alkaline phosphatase activity with respect to the control, the roughest surface exhibiting a more prolonged effect on the time.

Alkaline Phosphatase↗

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↗

PubMed1992

Significantly improved peripheral intravenous catheter performance in neonates: insertion ease, dwell time, complication rate, and costs.

A prospective, randomized, controlled study was performed in neonates in an intensive care nursery to compare the performance of a peripheral intravenous catheter made of Aquavene material (test catheter) with that of a conventional peripheral catheter made of Teflon material (control catheter). Aquavene is a newly developed biomaterial that softens and expands on contact with body fluids. A total of 105 catheters (50 test and 55 control) were inserted in 63 neonates. The median time to a catheter-related complication was 3.60 days for the test catheters and 1.75 days for the control catheters (p = 0.0007). Infiltration rate for the test catheters was 56% as compared with 78% for the control catheters (p = 0.03). The test catheters provided fewer catheter-related complications (p = 0.006), with 34% of the test catheters reaching end of therapy as compared with 9% of the control catheters (p = 0.004). On average, 1.8 test catheters were used per insertion versus 2.3 control catheters (p = 0.08). The test catheters were rated easier to insert (p = 0.05), with a shorter time required for insertion. Because of improved performance, cost savings were realized with the test catheters after the first day of therapy, even though the per unit cost of the test catheter was greater. These data indicate that the test catheter, made of Aquavene material, is superior to the Teflon catheter for peripheral intravenous therapy in neonates.

Biocompatible Materials↗

PubMed2005

Hydroxyapatite promotes superior keratocyte adhesion and proliferation in comparison with current keratoprosthesis skirt materials.

AIM: Published clinical series suggest the osteoodontokeratoprosthesis (OOKP) may have a lower extrusion rate than current synthetic keratoprostheses. The OOKP is anchored in the eye wall by autologous tooth. The authors' aim was to compare adhesion, proliferation, and morphology for telomerase transformed keratocytes seeded on calcium hydroxyapatite (the principal mineral constituent of tooth) and materials used in the anchoring elements of commercially available synthetic keratoprostheses. METHODS: Test materials were hydroxyapatite, polytetrafluoroethylene (PTFE), polyhydroxyethyl methacrylate (HEMA), and glass (control). Cell adhesion and viability were quantified at 4 hours, 24 hours, and 1 week using a calcein-AM/EthD-1 viability/cytotoxicity assay. Focal contact expression and cytoskeletal organisation were studied at 24 hours by confocal microscopy with immunoflourescent labelling. Further studies of cell morphology were performed using light and scanning electron microscopy. RESULTS: Live cell counts were significantly greater on hydroxyapatite surfaces at each time point (p<0.04). Dead cell counts were significantly higher for PTFE at 7 days (p<0.002). ss(1) integrin expression was highest on hydroxyapatite. Adhesion structures were well expressed in flat, spread out keratocytes on both HA and glass. Keratocytes tended to be thinner and spindle shaped on PTFE. The relatively few keratocytes visible on HEMA test surfaces were rounded and poorly adherent. CONCLUSIONS: Keratocyte adhesion, spreading, and viability on hydroxyapatite test surfaces is superior to that seen on PTFE and HEMA. Improving the initial cell adhesion environment in the skirt element of keratoprostheses may enhance tissue integration and reduce device failure rates.

Biocompatible Materials↗

PubMed1995

A new temporary soft lining material.

The viscoelastic properties of a new light-activated temporary denture soft lining material have been monitored in vitro using a force/distance probe. Its baseline behaviour was characteristic of an elastic material and its compliance considerably less than that of both a short-term and a long-term soft lining material which were used as controls. Sample thickness had no appreciable effect on this compliance. These results suggest that the new product is likely to be perceived as being significantly harder by a patient. Twenty-four weeks' immersion in distilled water had no significant effect on either the compliance or elasticity of the test material and would suggest an improved durability when compared to other conventional short-term resilient denture lining materials, albeit at the expense of compliance.

Compliance↗

PubMed2004

Comparison of the dimensional accuracy of injection-molded denture base materials to that of conventional pressure-pack acrylic resin.

PURPOSE: This study compared the linear dimensional changes of 3 injection-molded denture base materials to that of conventionally processed polymethylmethacrylate (PMMA) resin. MATERIALS AND METHODS: An impression of an aluminum maxillary edentulous arch was made with a condensation silicone impression material (Denture Elasticon) to fabricate a gypsum master cast that was replicated as a silicone mold. A maxillary complete denture with acrylic teeth was waxed to full contour on the master cast and replicated to make 40 wax dentures. ERA attachments cast in metal (Rexillium) with indices milled into the centers were waxed into 3 positions in each denture for recording dimensional measurements of the wax denture. Ten dentures were allocated to each of 4 groups; Group 1 was processed using conventionally processed PMMA (Microlon), Group 2 used injection-molded PMMA (SR-lvocap), Group 3 employed injection-molded nylon (Valplast), and Group 4 used injection-molded styrene (Northern). All processed specimens were stored at room temperature (25 degrees C, ambient humidity) for 1 week (while still on the master cast) before anteroposterior and cross-arch measurements were made using the ERA reference points with a digital caliper. After separation from the master cast and following water storage at 37 degrees C for 7 days additional measurements were made. RESULTS: An analysis of the results showed that the effect of processing was not the same for the 3 dimensions studied, regardless of which dimension was considered (p < 0.0001). The pattern of dimensional changes associated with the material type was not the same between the wax and processing stages as it was for the change between the processing and decasting stages (p < 0.0001). CONCLUSIONS: Processing the denture base materials produced unequal deformation in different dimensions (anterior-posterior and cross-arch). Each material tested also responded differently to the processing stages.

Acrylic Resins↗

PubMed1994

A comparison of the compressive strength of calcium hydroxide based lining materials.

This in vitro study investigated the compressive strength of five commercially available calcium hydroxide based lining materials and a resin bonded zinc oxide/eugenol material under varying conditions of temperature and relative humidity and at various ++time intervals after mixing. The results of the study showed that the calcium hydroxide liners could be consistently ranked in order with Dycal most frequently having the highest and either Life or Renew having the lowest compressive strength at all time intervals examined. Under simulated clinical conditions all the materials tested with the exception of Life and Renew had sufficient compressive strength 3 minutes after mixing to withstand the force of amalgam condensation.

Calcium Hydroxide↗

PubMedDate not supplied

Shear bond strengths of resin-modified glass-ionomer restorative materials.

The purpose of this study was to evaluate the shear bond strength of resin-modified glass-ionomer restorative materials to dentin. The materials tested were Fuji II LC, Geristore, Photac-Fil, VariGlass VLC, and Vitremer. Ketac-Fil, a conventional glass ionomer, was used as the control. The occlusal surfaces of 60 extracted molars were ground flat in dentin using 600-grit silicon carbide abrasive paper. Dentin surfaces were treated according to manufacturers' instructions, and restorative materials were applied using gelatin capsule matrices. Shear bond strengths were determined after the specimens were thermocycled 500 times. Mean bond strengths of the resin-modified glass ionomers ranged from 1.4 MPa (Photac-Fil) to 12.3 MPa (Fuji II LC). Except for Photac-Fil, all values were significantly higher than the control. Pairwise comparisons between the means for Fuji II LC and Vitremer, Vitremer and Geristore, and Geristore and VariGlass were not significantly different.

Acrylic Resins↗

PubMed1995

Surface characteristics of polyether and addition silicone impression materials after long-term disinfection.

It has been demonstrated that short-term disinfection can affect the surface properties of impression materials. This study evaluated advancing contact angle, receding contact angle, inhibition and mass loss of a polyether impression materials, and two different viscosities of an addition silicone impression material after long-term immersion disinfection (18 hours). The brand names of the impression materials tested were Impregum F, Extrude Extra, and Extrude Wash, and all were tested by use of the Wilhelmy technique; first, for the nondisinfected state, which served as controls, and then after 1 and 18 hours of disinfection in a full-strength solution of acid glutaraldehyde. Weight changes before and after the disinfection process were also measured to detect weight loss and mass change over time. All materials exhibited some degree of inhibition. Polyether lost 0.4% mass in air, which indicated loss of a volatile component. Polyether and addition silicone were both relatively hydrophobic and could be disinfected with acid glutaraldehyde for up to 18 hours without affecting wettability.

Analysis of Variance↗

PubMed1997

Bond strengths of resin-modified glass ionomers and polyacid-modified resin composites to dentin.

PURPOSE: To measure the shear bond strength of two resin-modified glass ionomers (Vitremer and Fuji II LC) and two polyacid-modified resin composites (Compoglass and Dyract) when applied to dry dentin, dentin supplied with water pressure from the pulp, and after thermocycling. MATERIALS AND METHODS: Ninety six extracted third molars were used. The root portion was removed just below the cemento-enamel junction and the occlusal enamel was removed from the crown segment. An artificial root portion was made in Plexiglas, cemented to the crown segment and connected to a 36 cm. height water column. The tested materials were applied to the surface of dry dentin, dentin supplied with water pressure from the pulp, and after thermocycling. Shear bond strength was measured for the bonded specimens using an Instron at a crosshead speed of 0.5 mm/minute. RESULTS: There were no significant differences in bond strengths between Fuji II LC, Compoglass, and Dyract, which were significantly greater than that of Vitremer. The bond strengths of all materials were slightly increased or not affected by the presence of water pressure from the pulp. After thermocycling, the bond strengths of Fuji II LC, Compoglass, and Dyract were not significantly affected whereas those of Vitremer were significantly decreased.

Analysis of Variance↗

PubMed1994

Effects of different levels of direct current on early ligament healing in a rat model.

Electrical stimulation has been shown to enhance the repair of biological tissues such as bone and tendon. The objective of this study was to determine whether low level direct current enhances the early healing of injured medial collateral ligaments. Eighty-seven rats were divided into three groups on the basis of the level of current delivered. All underwent transection of the medial collateral ligament bilaterally. The experimental medial collateral ligaments received current (which varied by group), while the contralateral medial collateral ligaments (the controls), with identical electrodes, received no current. After 12 days, each ligament was tested biomechanically with use of a hydraulic materials testing machine. Group 1 (8.6 +/- 5.9 microA) showed statistically significant improvements in maximum rupture force, energy absorbed, stiffness, and laxity. The groups that had received lower levels of current did not show significant improvements. In this study, stimulation of 1-20 microA was the most effective level of direct current for the enhancement of early healing of the medial collateral ligament.

Animals↗