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PubMed2006

Spectroscopic properties of Nd3+ doped transparent oxyfluoride glass ceramics.

In this paper, the spectroscopic properties of Nd(3+) doped transparent oxyfluoride glass ceramics containing LaF(3) nano-crystals were systematically studied. The formation and distribution of LaF(3) nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd-Ofelt theory, the intensity parameters Omega(t) (t=2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd(3+) were evaluated. Particularly, the effect of Nd(3+) doping level on them was discussed. With the increase of Nd(3+) concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4 micros, 78.3% and 1.86 x 10(-20)cm(2) to 214.7 micros, 39.9% and 1.52 x 10(-20)cm(2), respectively. The comparative study of Nd(3+) spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06 microm emission.

Ceramics↗
PubMed2006

Plastic containers and the whole-blood clotting test: glass remains the best option.

This is the first study to identify normal whole-blood clotting times in various plastic containers and to identify the effect of the addition of various concentrations of Pseudechis australis (Mulga snake) venom on the clotting time in glass and plastic. Polycarbonate was identified as a potential alternative to glass as a testing container owing to a whole-blood clotting time within acceptable limits for a bedside test (mean 29.5 min) and equivalent performance to glass in the presence of P. australis venom. Other plastic containers (such as polypropylene and polyethylene) were found to be unsuitable owing to very prolonged clotting times (>60 min) or impaired performance in the presence of venom. Overall, owing to the variation between the performance of different plastics and the difficulty in differentiating between them, plastic containers cannot be recommended as an alternative to glass when performing the whole-blood clotting test for envenomed patients.

Analysis of Variance↗
PubMed2004

Composite materials based on wastes of flat glass processing.

Glass mirrors scrap and poly (vinyl) butiral waste (PVB) obtained from flat glass processing plants were investigated as raw materials to produce composites. The emphasis was on studying the influence of milled glass mirror waste contents on properties of composites produced with PVB. The characterization involved: elongation under rupture, water absorption, tensile strength and elastic modulus tests. The results showed that the composite containing 10 wt% of filler powder had the best properties among the compositions studied. The influence of the time of exposure in humid atmosphere on the composite properties was investigated. It was found that the admixture of PVB iso-propanol solution to the scrap of glass mirrors during milling provided stabilization of the properties of the composites produced.

Glass↗
PubMed1993

Kinetics of specific and nonspecific adhesion of red blood cells on glass.

Fixed spherical human red blood cells suspended in 17% sucrose were allowed to adhere on either clean glass surfaces or glass surfaces preincubated with antibodies specific to a certain blood group antigen. The adhesion experiments were performed in an impinging jet apparatus, in which the cells are subjected to stagnation point flow. The objective of this study was to compare the efficiencies of nonspecific and specific (antigen-antibody mediated) adhesion of red blood cells on glass surfaces. The efficiency was defined as the ratio of the experimental adhesion rate to that calculated based on numerical solutions of the mass transfer equation, taking into account hydrodynamic interactions as well as colloidal forces. The efficiency for nonspecific adhesion was nearly unity at flow rates lower than 85 microliter/s (corresponding to a wall shear rate, Gw, of 30 s-1 at a radial distance of 110 microns from the stagnation point). The values of efficiency dropped at higher flow rates, due to an increase in the tangential force. The critical deposition concentration is found to occur at 120-150 mM NaCl, which is consistent with the theoretically predicted values. At low salt concentrations, the experimental values are higher than the theoretical ones. Similar discrepancies have been found in many colloidal systems. Introducing steric repulsion by adsorbing a layer of albumin molecules on the glass completely prevents nonspecific adhesion at flow rates below 60 microliter/s (Gw congruent to 15 s-1). The efficiency of specific adhesion depends both on the concentration of antibody molecules on the surface and the flow rate. Normal red cells adhere more readily through antigen-antibody bonds than fixed cells. Fixed spherical cells have a higher adhesion efficiency than fixed biconcave ones.

Antibodies↗
PubMed1975

Controlled pore glass chromatography of protein-sodium dodecyl sulphate complexes.

The inclusion of urea has been found to eliminate adsorption of protein-sodium dodecyl sulphate (SDS) complexes to controlled pore glass. Using buffer containing 6 M urea, 0.5% SDS and glass with pore diameter 12.3 nm, it is possible to determine protein molecular weights in the range 3500-12,000. Results with glass of larger pore diameter (25.5 nm) are similar to those reported in the absence of urea in the molecular-weight range 12,000-140,000. Controlled pore glass chromatography also permits the study of the relative importance of conformation free of charge effects for those proteins which deviate from the normal calibration curve for SDS-polyacrylamide gels.

Adsorption↗
PubMed1996

In vitro evaluation of antibacterial effects of photo-cured glass ionomer liners and dentin bonding agents during setting.

Two dentin bonding agents (Optibond and Syntac), an enamel bonding agent (Heliobond), and two photo-cured glass ionomer cements (Vitremer and Variglass VLC) and their inhibitory effects on bacterial growth during setting were examined. Cultures of eight bacterial species were used to test these materials, except for Vitremer glass ionomer cement, which was tested against only five species. The photo-cured glass ionomer cements and the Syntac dentin bonding system with glutaraldehyde demonstrated a significant inhibitory effect on the growth of several bacteria. Meanwhile, Variglass VLC glass ionomer cement did not exhibit this effect on Lactobacillus casei and Streptococcus sobrinus. Optibond light-cured dentin bonding agent, with fluoride and fillers in its composition, and Heliobond (negative control group) did not demonstrate any inhibitory effect.

Acrylates↗
PubMed1996

Clinical comparison of postoperative sensitivity for a glass ionomer and a zinc phosphate luting cement.

In 60 patients, 120 partial and full-coverage restorations were cemented on vital abutment teeth with either a glass ionomer or a zinc phosphate luting cement. A split-mouth design and a patient blind data acquisition protocol were used. During an average observation period of 17.3 months there were no differences between the two types of luting cements in regard to subjective and clinical parameters. A high incidence of postoperative hypersensitivity, which is often said to accompany the use of glass ionomer luting cements, was not observed. With the cementation method used in this study, the glass ionomer cement Ketac-Cem Maxicap was an acceptable alternative to conventional zinc phosphate cement. Capsule systems make the clinical handling of glass ionomer luting cements safe and easy and should be used routinely in dental practice.

Adult↗
PubMed1996

Dimensional accuracy and stability of polymethyl methacrylate reinforced with metal wire or with continuous glass fiber.

The aim of this study was to determine the dimensional accuracy and stability of denture base polymethyl methacrylate (PMMA), which was reinforced in various ways. Autopolymerizing PMMA and heat-cured PMMA were reinforced either with semicircular steel wire or with a prefabricated experimental reinforcement made of continuous E-glass fiber. Control specimens had no reinforcement. The width of each U-shaped test specimen was measured with a digital micrometer under a light microscope immediately after the test specimen was cured and when stored in water for 1, 2, 7, and 14 days. The results revealed that both the type of PMMA and the type of reinforcement affected the dimensional accuracy of the test specimens, especially after 7 and 14 days in water storage (p < 0.001). The greatest dimensional accuracy was found with the unreinforced test specimen made from autopolymerizing PMMA and with test specimens reinforced with the metal wire made from heat-cured PMMA. In terms of the width of the test specimens, the lowest dimensional accuracy was found in unreinforced and glass fiber reinforced specimens made from heat-cured PMMA. Storage in water did not affect the stability of the width (p > 0.1). The results suggest that the polymerization shrinkage of PMMA causes lower dimensional accuracy of the test specimens reinforced with glass fiber. This should be considered when glass-fiber reinforcement is used clinically.

Analysis of Variance↗
PubMed1998

The effect of glass fiber reinforcement on the fracture resistance of a provisional fixed partial denture.

PURPOSE: This study determined the load required to fracture a three-unit provisional fixed partial denture restoration, which had been reinforced with an experimental glass fiber reinforcement. MATERIAL AND METHODS: Provisional fixed partial dentures (n = 5) were fabricated from a resin of polyethyl methacrylate powder and n-butylmethacrylate liquid. The fixed partial dentures in the control group were unreinforced. In the other groups, the fixed partial dentures were reinforced either with one, two, or three unidirectional glass fiber reinforcements and one glass fiber weave reinforcement. The load was applied to the fixed partial dentures by a steel ball placed in the cavity in the middle fossa of the pontic tooth. A longitudinal section of the fixed partial denture was made to determine the position of the reinforcements. Means were compared by analysis of variance. RESULTS: The load required to fracture the unreinforced fixed partial denture was 614 N, while incorporation of one unidirectional reinforcement increased the load to 660 N, two reinforcements to 818 N, three reinforcements to 827 N, and three reinforcements with one weave reinforcement to 973 N. It was found that the unidirectional reinforcements were positioned on the side of the occlusal surface of the fixed partial denture, namely, the side of compression during loading. CONCLUSION: The results suggest that, even though the glass fiber reinforcements were positioned on the least favorable side of the fixed partial denture in terms of the physical properties of the materials, these reinforcements considerably increased the fracture resistance of the provisional fixed partial denture.

Analysis of Variance↗
PubMed1999

Effect of sandblasting and silicoating on bond strength of polymer-glass composite to cast titanium.

STATEMENT OF PROBLEM: There is little information regarding the mechanical and chemical retention of polymer-glass composite to cast titanium. PURPOSE: This study examined whether sandblasting in conjunction with silicoating improves the bond strength of the polymer-glass composite to cast titanium. MATERIALS AND METHODS: Disk patterns (10 mm in diameter, 2.5 mm thick) were cast with commercially pure titanium (CP Ti) and Type IV gold alloy. Three pretreatments were applied: 50 microm Al(2)O(3) sandblasting (50 SB), 250 microm Al(2)O(3) sandblasting (250 SB), and 600-grit SiC paper polishing (600 SiC). After surface preparation, the Siloc system (silicoating) was applied on the disks. The 50 SB specimens without Siloc system were also prepared as controls. Then sticky tape with a circular hole (4.76 mm diameter) was placed onto the disk to define the bonding area. Artglass (polymer-glass) opaque, dentin, and enamel composites were applied using Teflon matrices and then light-polymerized. Shear bond strength (n = 8) was determined at a crosshead speed of 5 mm/min. Results were analyzed statistically with 2-way ANOVA and the Tukey-Kramer test (alpha=.05). RESULTS: The Siloc system significantly (P <.05) improved the mean shear bond strength of Artglass to both metals in the 50 SB specimens. Statistical differences (P <.05) in shear bond strength were found among surface treatments for the silicoated CP Ti specimens, in which 250 SB specimens yielded the greatest bond strength. The Type IV specimens treated with Siloc system showed no significant differences in shear bond strength between the 50 SB and the 250 SB specimens. CONCLUSION: Sandblasting with coarser alumina particles in conjunction with silicoating significantly enhanced bond strength of polymer-glass composite to cast titanium.

Analysis of Variance↗
PubMed1999

Survival of Dicor glass-ceramic dental restorations over 14 years. Part II: effect of thickness of Dicor material and design of tooth preparation.

STATEMENT OF PROBLEM: The influence of different restorative design features on the long-term survival of Dicor glass-ceramic restorations is not well understood. PURPOSE: This study examined the relationship of different types of restorations and methods of preparation with the survival of Dicor glass-ceramic restorations functioning in vivo. MATERIAL AND METHODS: A total of 1444 Dicor glass-ceramic restorations were placed on the teeth of 417 adults. Failure was defined as a restoration that required remake because of material fracture. Survival of restorations of different types and with different methods of preparation was described by using Kaplan Meier survivor functions. Statistical significance between restoration type and preparation method was determined with the log rank test. RESULTS: Probability of survival of a typical partial coverage restoration was 92% at 11.3 years. There was no statistically significant difference between the survival of inlay or onlay restorations. For the 91 cores used for pulpless teeth, none failed over a total cumulative monitoring period of 419 years. There was no significant difference in survival of acid-etched Dicor restorations that were placed on shoulder or chamfer preparations. Thickness measured at the midpoint of the labial, lingual, mesial, distal, and midocclusal surfaces did not relate to risk of failure. CONCLUSIONS: The majority of Dicor glass-ceramic partial coverage inlay and onlay restorations and cores survived over time. Survival of restorations with either chamfer or shoulder preparations did not differ whether the restoration was acid-etched. Thickness of the restoration measured at the midaxial point of each surface did not relate to survival.

Acid Etching, Dental↗
PubMed1999

Effect of fluorosis on shear bond strength of glass ionomer-based restorative materials to dentin.

STATEMENT OF PROBLEM: Several studies have investigated the adhesion of glass ionomer-based restorative materials to nonfluorotic teeth, but there appears to be no information on the bond strength of these restorative materials to dentin in fluorotic teeth. PURPOSE: This study investigated the effect of dental fluorosis on the bond strength of Ketac-fil conventional glass ionomer cement, Vitremer resin-modified glass ionomer cement, and Dyract polyacid modified resin to dentin. MATERIAL AND METHODS: Ninety posterior teeth were classified according to the severity of fluorosis, by using the Thylstrup and Fejerskov index, TFI. The teeth were divided into 3 equal groups (TFI = 0,TFI = 1-3, TFI = 4+) of 30 teeth, which were again divided into 3 equal subgroups for testing each of the3 restorative materials. Occlusal surfaces of mounted teeth were ground flat to expose dentin. Cylindrical specimens (4 mm diameter and 4 mm high) of the restorative materials were bonded to the middle of the cleaned exposed dentin surfaces, according to the manufacturers' instructions. After storing the specimens in 100% humidity at 37 degrees C for 24 hours, shear bond strengths of the restorative materials were measured with an Instron testing machine at crosshead speed of 0.5 mm/min. RESULTS: Two-way analysis of variance and Tukey-B test revealed that Dyract had significantly higher shear bond strength to dentin than Ketac-fil or Vitremer cements, regardless of severity of fluorosis (P <.05). Furthermore, there was an inverse relationship between shear bond strength and the severity of fluorosis for each of the restorative materials. Cohesive mode of failure was most prevalent in nonfluorotic teeth (TFI = 0), especially with Ketac-fil cement, whereas Dyract cement had the greatest propensity for adhesive failure. CONCLUSION: Fluorosis reduces the shear bond strength of glass ionomer-based restorative materials to dentin.

Adhesiveness↗
PubMed1999

Flexural properties of acrylic resin polymers reinforced with unidirectional and woven glass fibers.

STATEMENT OF PROBLEM: Fiber-reinforced plastics for dental applications have been under development for some time. A major difficulty in using reinforcing fibers with multiphase acrylic resins, such as powderliquid resins, has been improper impregnation of fibers with the resin. PURPOSE: The aim of this study was to describe and test a novel system to use polymer-preimpregnated reinforcing fibers with commonly used multiphase acrylic resins. MATERIAL AND METHODS: Continuous unidirectional and woven preimpregnated glass fiber reinforcements (Stick and Stick Net) were used to reinforce heat-curing denture base and autopolymerizing denture base polymers. A temporary fixed partial denture polymer was also reinforced with Stick reinforcement material. Five test specimens were fabricated for unreinforced control groups and for Stick- and Stick Net-reinforced groups. A 3-point loading test was used to measure transverse strength and flexural modulus of the materials and ultimate strain at fracture was calculated. Cross-sections of test specimens were examined with a SEM to evaluate degree of impregnation of fibers with polymer matrix. Quantity of fibers in test specimens was determined by combustion analysis. RESULTS: Transverse strength of heat-curing denture base polymer was 76 MPa, Stick reinforcement increased it to 341 MPa, and flexural modulus increased from 2550 to 19086 MPa. Stick Net reinforcement increased transverse strength of heat-curing denture base polymer to 99 MPa and flexural modulus to 3530 MPa. Transverse strength of autopolymerizing denture base polymer was 71 MPa; Stick increased it to 466 MPa; and flexural modulus increased from 2418 to 16749 MPa. Stick Net increased the transverse strength of autopolymerizing denture base polymer to 96 MPa and flexural modulus to 3573 MPa. Transverse strength of temporary fixed partial denture polymer increased from 58 to 241 MPa and flexural modulus from 1711 to 7227 MPa. ANOVA showed that reinforcement type and polymer brand affected transverse strength and modulus (P <.001). Stick Net reinforcement increased the strain at fracture, whereas Stick reinforcement decreased the strain values. SEM examination revealed well-impregnated glass fibers with polymer matrix. Quantity of glass fibers varied from 6 to 28 vol-%, the lowest being with Stick Net reinforcement and the highest with Stick reinforcement. CONCLUSIONS: Novel glass fiber reinforcements may considerably enhance flexural properties of multiphase dental polymers, which is due to proper impregnation of fibers with polymer matrix. By using Stick or Stick Net reinforcement, the strain at fracture of the material can be modified.

Acrylic Resins↗
PubMed2001

Retrospective assessment of historic radon concentrations in Norwegian dwellings by measuring glass implanted Po-210--an international field intercomparison.

The first Norwegian study of historic radon concentrations in 17 dwellings in the high radon areas in Norway has been conducted as part of an international field intercomparison during 1998. The retrospective radon concentration is estimated via measurements of Po-210, the long-lived decay product of Rn-222 implanted in glass surfaces of objects like pictures, mirrors, cabinet-glass, etc. the method called 'surface trap'. Three different surface trap techniques to assess the implanted Po-210 activity and two different procedures to estimate retro radon from Po-210 data were used. The Po-210 and the retrospectively estimated radon results agree reasonably well over a wide range of concentrations. Historic radon concentrations were also estimated from analysis of a smaller number of 'volume trap' samples (pieces of spongy materials), and the results compared to those from 'surface traps'. The retro radon results correlate with contemporary radon results with a correlation coefficient of 0.877. To evaluate uncertainty in Po-210 measurements due to varying position on the glass a study of spatial homogeneity of three sample glasses was conducted and variations between 12% and 18% were found.

Air Pollution, Indoor↗
PubMed1999

Histological evaluation of repair using a bioresorbable membrane beneath a resin-modified glass ionomer after mechanical furcation perforation in dogs' teeth.

Resorbable barriers have been shown both clinically and histologically to produce favorable periodontal regenerative outcomes. The purpose of the present study was to evaluate the histological response to one such resorbable barrier (Atrisorb) when used as a matrix under a resin-modified glass ionomer (RMGI) sealant in the repair of furcation perforations in experimental animals. After anesthesia, pulp extirpation and filling of radicular canals with zinc oxide-eugenol cement, furcal perforations were made in 30 lower premolar (P2, P3, and P4) teeth of labrador dogs with a 1 mm diameter round bur in a conventional handpiece. The perforated teeth were randomly divided into two groups of 15 teeth. Group 1 teeth were treated with RMGI alone and group 2 with the resorbable barrier under RMGI. Six teeth without perforations served as negative controls. Pulp chambers of all teeth were filled with RMGI cement. Animals were sacrificed after 3 months. The teeth and the surrounding structures were processed for light microscopy. There were no differences found between results for glass ionomer alone and barrier with glass ionomer. The conclusion of this study is that placement of a resorbable barrier at the pulp chamber aspect of a furcation perforation did not result in superior healing, compared with the use of resin-modified glass ionomer alone.

Absorbable Implants↗
PubMed2000

Effect of furnace type and ceramming heat treatment conditions on the biaxial flexural strength of a canasite glass-ceramic.

OBJECTIVE: To assess the effect of different heat treatment conditions when using two different furnace types on the biaxial flexural strength (BFS) of a fluorcanasite castable glass-ceramic. METHODS: Two furnace types, one a programmable furnace (PF), the other a dental laboratory burnout furnace (DLF), were used with various ceramming times to determine their effect on the BFS of a fluorcanasite castable glass-ceramic. The glass-ceramic material was cast to produce discs of 12 mm diameter and 2 mm thickness using the lost wax casting process (n = 80). After casting, both furnace types were used to ceram the discs. Half the discs were not de-vested from the casting ring before ceramming but cerammed in situ (DLF) and half were de-vested before ceramming (PF). All the discs were given a nucleation heat treatment at 520 degrees C for 1 h and then cerammed at 860 degrees C using four heat soak times (0.5, 1, 2 and 3 h). The DLF furnace had a rate of climb of 13 degrees C/min and the PF furnace had a rate of climb of 5 degrees C/min to 520 degrees C and 3 degrees C/min to 860 degrees C. After ceramming the discs were de-vested and the BFS determined using a Lloyd 2000R tester. RESULTS: The maximum BFS values seen for both furnace types were almost identical (280 MPa), but were achieved at different heat soak times (1 h DLF, and 2 h PF). The only significant differences in BFS values for the two furnaces were between the 0.5 and 2 h heat soak times (p < or = 0.05). Individual differences were seen between results obtained from each furnace type/heat soak times evaluated (p < or = 0.05). SIGNIFICANCE: Already available dental laboratory burnout furnaces can be used to ceram fluorcanasite glass-ceramic castings to the same BFS values as more expensive and slower specialist programmable furnaces.

Analysis of Variance↗
PubMed2001

Interfacial shear strengths of dental resin-glass fibers by the microbond test.

OBJECTIVES: The aim of this study was to investigate the feasibility of using the microbond test (MBT) to probe the durability of the bond between a polymerized dental resin with differently silanized E-glass fibers. METHODS: The E-glass fibers were silanized with equivalent amounts of two types of acrylic-silane coupling agents: 3-methacryloxypropyltrimethoxysilane (MPTMS) and 10-methacryloxydecyltrimethoxysilane (MDTMS), a more hydrophobic silane coupling agent than MPTMS. Unsilanized E-glass fibers were used as the control. Microdroplets of a photo-activated dental resin were applied on the fiber and photocured with visible light irradiation (470 nm). Subsequently, the specimens were tested in shear after 24h storage in air at 23 degrees C or water at 60 degrees C. RESULTS: The mean interfacial shear strength (tau) and the standard deviation in MPa for the three systems in 23 degrees C in air (n>7) were: 33.8(10.1), 33.7(8.9) and 15.3(4.2) for the MPTMS silanized, MDTMS silanized, and unsilanized fibers, respectively. When the three types of fibers were first exposed to 60 degrees C water for 24h prior to having the microdroplets of the resin bonded to them, the strength values of the MDTMS silanized fibers and the control fibers remained essentially unchanged at (n> or =7) 31.8(7.7) and 17.5(4.9)MPa respectively; the MPTMS specimens showed a significant decrease to 15.8(4.8)MPa. Similar trends were observed when the fibers had microdroplets of the resin bonded to them prior to aqueous exposure. SIGNIFICANCE: These results indicate that the microbond test has the sensitivity to measure changes at the interface between polymerized dental resins and variously silanized E-glass fibers. It appears that surface modification of the fibers with the more hydrophobic silane coupling agent MDTMS promotes enhanced resistance to degradation from exposure to water. The microbond test has the potential for studying dental adhesion involving small bonded areas under a variety of conditions with different adhesive systems and substrates.

Composite Resins↗
PubMed2002

Effect of encapsulation on the fluoride release from conventional glass ionomers.

OBJECTIVES: The aim of the present study is to investigate the effect of the type of encapsulation and the batch on the fluoride release of conventionally setting glass ionomer cements Ketac-Fil and Fuji Cap II. METHODS: Three capsule types were selected: the capsules of Ketac-Fil and Fuji Cap II, and standard capsules. Six individual series of five cylindrical specimens were made from fresh mixes and leached at 37 degrees C with 25 ml distilled water up to 56 days. A second series of five specimens per formulation in original capsules was made from fresh mixes of another batch. The fluoride concentration was determined by means of a fluoride-ion selective electrode. RESULTS: The fluoride release profiles of a given glass ionomer formulation generally run parallel regardless of the type of encapsulation. When the amounts of fluoride released within the specific formulation were compared as a function of the capsule type, statistically significant differences were only found for Ketac-Fil. Comparing the amounts of fluoride released by different batches of a given glass ionomer formulation, statistically significant differences were only found for Fuji Cap II. SIGNIFICANCE: The type of encapsulation may affect the fluoride release of a given glass ionomer formulation quantitatively, but not qualitatively. Apparently, different batches of the same formulation may result in different amounts of fluoride released.

Analysis of Variance↗