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At least 1,459 records · Page 81Linked to original sources
PubMed1998

White spot formation under orthodontic bands cemented with glass ionomer with or without Fluor Protector.

The purpose of this study was to determine whether an additional application of Fluor Protector before band cementation with glass ionomer cement reduces white spot formation compared with band cementation with glass ionomer cement. In the in vitro study, 80 premolars were divided in half, creating a control and a test group. All specimens were divided into four different groups to simulate different clinical situations and stored in a demineralizing solution to induce white spot formation. In the in vivo investigation, 18 orthodontic patients were incorporated in the study. One lower and one upper first molar band (randomly selected) were coated with Fluor Protector and then cemented with a glass ionomer cement (test group). The other two uncoated first molars were cemented with glass ionomer cement and served as the control group. The application of Fluor Protector in combination with Aquacem did not contribute to a reduction of white spot formation underneath molar bands compared with the use of Aquacem for banding.

Acrylic Resins↗
PubMed2005

Mortality and cancer incidence in Ontario glass fiber workers.

BACKGROUND: In a previous cohort study of glass fiber manufacturing, we found a significant increase in lung cancer. This study extends the follow-up period. METHODS: We conducted a historical prospective study of 2557 men employed in producing glass wool. We obtained work histories, causes and dates of death, and date and site of cancer diagnoses. We computed standardized mortality and incidence ratios (SMR, SIR). RESULTS: The overall SMR for lung cancer was 163 (95% CI = 118-221). The SMR did not vary consistently by duration of employment and time since first employment. However, plant workers with >20 years' employment and >40 years since first exposure had an SMR for lung cancer of 282 (95% CI = 113-582). The SMR dropped with later date of first exposure, but the trend was non-significant. There was an unexpected overall increase in kidney cancer incidence. DISCUSSION: The increase in lung cancer is greater than in other cohorts of glass fiber workers. Since exposure data are lacking from the early years of the plant, we cannot state if the excess was due to glass fibers, other work exposures or other reasons.

Adult↗
PubMed1988

Glass wool column filtration of human semen: relation to swim-up procedure and outcome of IVF.

The number and viability of spermatozoa recovered by glass wool column filtration and a swim-up procedure were compared using different types of ejaculates, such as normal, asthenozoospermic and very viscous oligozoospermic semen. The filtration procedure resulted in significantly (P less than 0.01) higher recovery of viable spermatozoa than the swim-up procedure from all types of ejaculates studied. Further, the spermatozoa from 50 (78.1%) of the 64 ejaculates filtered through glass wool column fertilized at least one intact human egg in an in-vitro fertilization (IVF) procedure. It is concluded that glass wool column filtration is superior to the swim-up procedure since it yields a higher recovery of viable spermatozoa that are potentially fertile. Therefore, the glass wool column filtration procedure used to prepare spermatozoa may be of benefit for IVF, intra-uterine insemination, in-vitro fertilization and GIFT (gamete intra-Fallopian transfer), especially in cases of poor quality semen.

Cell Separation↗
PubMed2006

Comparison on characteristics of radiophotoluminescent glass dosemeters and thermoluminescent dosemeters.

The radiophotoluminescent glass dosemeter (RPLGD) system is applicable for measurement of radiation dose of X rays and gamma rays by using radiophotoluminescent glass (silver-activated phosphate glass). When the radiophotoluminescent glass is exposed to ionizing radiation, stable luminescent centres are created. During pulsed ultraviolet laser excitation (337.1 nm) in the reader, the centres emit a radiation induced orange fluorescent light (600-700 nm). This phenomenon is called radiophotoluminescence. This study compared the RPLGD system with lithium fluoride (LiF) thermoluminescence dosimetry system and the results of the study revealed that the RPLGD had not only good basic characteristics for reproducibility of readout value, dose linearity, energy dependence and fading, but also infinite repeatable measurements and could be one of the most important radiation dose measurement instruments.

Computer Simulation↗
PubMed2006

Use of composites of topaz-glass as TSEE and TL dosemeters.

The properties of the thermally stimulated exoelectron emission (TSEE) and thermoluminescent (TL) emission of topaz-glass composites were studied with the aim of using them as solid-state dosemeters. The TSEE response was studied as a function of radiation energy and as a function of absorbed dose. Topaz-glass composites presented a linear TL and TSEE response to dose within a range of 0.01-1 Gy. The topaz-glass composites presented higher TSEE peaks than topaz-Teflon pellets. In the dosimetry of radiotherapic fields normally the responses of the topaz-glass dosemeters are comparable to topaz-Teflon pellets. The results confirmed that these new dosemeters can be useful in monitoring the quality of the radiation sources. This dose mapping technique is particularly useful in investigating dose distribution throughout a planned target volume.

Computer Simulation↗
PubMed2004

A comparison of the in vitro retentive strength of glass-ionomer cement, zinc-phosphate cement, and mineral trioxide aggregate for the retention of prefabricated posts in bovine incisors.

The purpose of this study was to compare the retentive strength of zinc-phosphate cement, glass-ionomer cement, and mineral trioxide aggregate (MTA) cement in the retention of prefabricated posts. The root canals of 60 bovine incisors were prepared and obturated with warm gutta-percha. Post space was prepared, the smear layer removed, and posts were luted with zinc-phosphate cement, glass-ionomer cement, or MTA. The specimens were stored at 37 degrees C and 100% humidity for 2 weeks, and then subjected to increasing axial tensile forces by an Instron machine until bond failure occurred. Data were analyzed by a one-way ANOVA and a Tukey-Kramer multiple comparison test. The retentive strengths of zinc phosphate and glass-ionomer cements were statistically equivalent, and significantly greater than MTA (p < 0.001), which suggests that zinc phosphate or glass-ionomer cement may be superior to MTA when used as luting agents for posts in endodontically treated teeth.

Aluminum Compounds↗
PubMed2004

Glass and antimony electrodes for oesophageal pH monitoring in distressed infants: how different are they?

OBJECTIVE: Although antimony electrodes are by far the most popular for performing oesophageal pH monitoring, there are few data comparing the accuracy of glass and antimony electrodes. Therefore, we tested the accuracy of both electrodes in the prediction of oesophagitis. METHOD: pH monitoring using a glass electrode and an antimony electrode was performed in 60 distressed infants, aged between 1 and 6 months. An upper endoscopy with oesophageal biopsies was also performed in all infants. RESULTS: A reflux index (percentage of the total time with pH < 4.0) greater than 5% was considered to be abnormal and was found in 40/60 patients. Histological oesophagitis was present in 26/60 infants. The reflux index was > 5% with the glass electrode in 18/26 children with histological oesophagitis and with the antimony electrode in 10/26 children with histological oesophagitis. Histology of the oesophagus was normal in 22/40 children with abnormal pH monitoring. With the glass electrode, the mean reflux index in the group with oesophagitis was significantly higher than in the group with normal histology, although there was an important overlap. With the antimony electrode, the mean reflux indices in the groups with and without oesophagitis were not different. Regarding normal/abnormal, there was discordance in 35% of the pH studies. No reflux index could be related to a clinically useful sensitivity and specificity to predict oesophagitis. CONCLUSION: The reflux index does not accurately predict oesophagitis. Oesophageal pH monitoring and endoscopy provide complementary information.

Antimony↗
PubMed2005

Microhardness of composites in simulated root canals cured with light transmitting posts and glass-fiber reinforced composite posts.

The aim of this study was to evaluate the depth of cure of composite resin cured within simulated root canals by means of light-transmitting plastic posts, glass-fiber-reinforced composite posts, and conventional light curing method. Thirty black plastic cylinders measuring 15 mm in length and 4 mm in internal diameter were divided into three groups. The composite resin was packed into simulated canals. The light-transmitting plastic posts and glass-fiber-reinforced composite posts were inserted into simulated canals and light cured for 90 seconds. The control group was light cured directly. To ensure continual change of material properties by increasing the length of material, a surface microhardness test was done 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, and 14 mm from the light exposure surface. The results showed a significant increase in microhardness of composite resin (depth of cure) for both light-transmitting plastic posts and glass-fiber-reinforced composite posts compared with the control group. The microhardness of composite resin was also significantly higher with light-transmitting plastic posts than glass-fiber-reinforced composite posts after 8 mm.

Analysis of Variance↗
PubMed2005

Evaluation of the flexural strength of carbon fiber-, quartz fiber-, and glass fiber-based posts.

This study investigated the flexural strength of eight fiber posts (one carbon fiber, one carbon/quartz fiber, one opaque quartz fiber, two translucent quartz fiber, and three glass fiber posts). Eighty fiber posts were used and divided into eight groups (n = 10): G1: C-POST (Bisco); G2: AESTHETI-POST (Bisco); G3: AESTHETI-PLUS (Bisco); G4: LIGHT-POST (Bisco); G5: D.T. LIGHT-POST (Bisco); G6: PARAPOST WHITE (Coltene); G7: FIBERKOR (Pentron); G8: REFORPOST (Angelus). All of the samples were tested using the three-point bending test. The averages obtained were submitted to the ANOVA and to Tukey's test (p < 0.05). The mean values (MPa) of the groups AESTHETI-POST-carbon/quartz fiber post (Bisco) and AESTHETI-PLUS-quartz fiber post (Bisco) were statistically similar and higher than the mean values of the other groups. The mean values of the groups C-POST-carbon fiber post (Bisco), LIGHT-POST-translucent quartz fiber post (Bisco), D.T. LIGHT-POST-double tapered translucent quartz fiber post (Bisco), PARAPOST WHITE-glass fiber post (Coltene) and FIBREKOR--glass fiber post (Pentron) were similar and higher than the group REFORPOST-glass fiber post (Angelus).

Analysis of Variance↗
PubMed2004

Glass foreign body in the spinal canal of a child: case report and review of the literature.

Retained foreign bodies pose a risk to the patient from the perspective of potential morbidity. We describe a previously healthy 8-year-old boy with head and back trauma from a glass picture frame that fell off the wall. He sustained a closed head injury and a back laceration several centimeters lateral to the spine. A persistent drainage from the back laceration contained glucose and protein levels consistent with cerebral spinal fluid. A foreign body was easily visible on subsequent plain radiograph. The glass foreign body was removed by neurosurgeons after computed tomography and magnetic resonance imaging clarified the exact location of the glass fragment. Physicians should have a low threshold for obtaining plain radiographs in patients with glass foreign bodies and consider that projectiles may rest some distance from the laceration site.

Accidents, Home↗
PubMed2001

The effects of glass fiber reinforcement at different concentrations on the transverse strength, deflection and modulus of elasticity of a provisional fixed partial denture resin.

This study focused on some mechanical properties such as the transverse strength, maximal deflection and modulus of elasticity of a resin reinforced with untreated, chopped form glass fibers at different concentrations. A Teflon mould was used to prepare four groups of specimens. The specimens were prepared with different concentrations of the glass fiber to the mass of the powder/liquid mix (0.5, 1, 1.5%), and a mix without fiber was used as the control group. All the specimens were subjected to transverse testing with a cross-head speed of 5 mm/min. The load to fracture for each specimen with the maximum deflection at the point of loading in a three-point load test was recorded. The transverse strength of 0.5% fiber concentration was 54.45 MPa. The lowest value was 49.67 MPa for the 1% fiber concentration. The highest mean strength was for the specimens reinforced with 0.5% glass fiber. This mean was higher than for the mean of the control "without fiber" specimens. The specimens demonstrated an insignificant decrease in the transverse strength and the maximum deflection when the fiber concentration was increased. The inclusion of 1% glass fiber reduced the transverse strength, although the result was not statistically significant.

Denture Repair↗
PubMedDate not supplied

Image-based stained glass.

We present a method of restyling an image so that it approximates the visual appearance of a work of stained glass. To this end, we develop a novel approach which involves image warping, segmentation, querying, and colorization along with texture synthesis. In our method, a given input image is first segmented. Each segment is subsequently transformed to match real segments of stained glass queried from a database of image exemplars. By using real sources of stained glass, our method produces high quality results in this nascent area of nonphotorealistic rendering. The generation of the stained glass requires only modest amounts of user interaction. This interaction is facilitated with a unique region-merging tool.

Algorithms↗
PubMed2002

Dynamics of green fluorescent protein mutant2 in solution, on spin-coated glasses, and encapsulated in wet silica gels.

Single-molecule experiments are performed by investigating spectroscopic properties of molecules either diffusing in and out of the observation volume or fixed in space by different immobilization procedures. To evaluate the effect of immobilization methods on the structural and dynamic properties of proteins, a highly fluorescent mutant of the green fluorescent protein, GFPmut2, was spectroscopically characterized in bulk solutions, dispersed on etched glasses, and encapsulated in wet, nanoporous silica gels. The emission spectrum, the fluorescence lifetimes, the anisotropy, and the rotational correlation time of GFPmut2, encapsulated in silica gels, are very similar to those obtained in solution. This finding indicates that the gel matrix does not alter the protein conformation and dynamics. In contrast, the fluorescence lifetimes of GFPmut2 on glasses are two-to fourfold higher and the fluorescence anisotropy decays yield almost no phase shifts. This indicates that the interaction of the protein with the bare glass surface induces a significant structural perturbation and severely restricts the rotational motion. Single molecules of GFPmut2 on glasses or in silica gels, identified by confocal image analysis, show a significant stability to illumination with bleaching times of the order of 90 and 60 sec, respectively. Overall, these data indicate that silica gels represent an ideal matrix for following biologically relevant events at a single molecule level.

Anisotropy↗
PubMed1996

Fissure sealing with a light-cured resin-reinforced glass-ionomer cement (Vitrebond) compared with a resin sealant.

The aims of the present study were to evaluate the retention and caries-preventive effect of a single application of a light-cured resin-reinforced glass-ionomer cement (Vitrebond) in pits and fissures of newly erupted permanent first and second molars, when compared with a single application of a resin-based sealant (Concise White Sealant) during a 3-year period. The study group comprised 73 pairs of contralateral newly erupted permanent first and second molars (136 fissure sites) in 53 children (29 girls, 24 boys). A split-mouth experimental design was used in which the two sealants were randomly allocated to one of the teeth within each pair. Acid etching was not used before application of the glass-ionomer cement. The sealed teeth were checked for retention and caries after 1, 6, 12, 24 and 36 months. The resin-based sealant was almost totally retained after 3 years (97%) and there was no caries in these teeth. The glass-ionomer cement was increasingly lost and could be observed in only 9% of the sealed sites after 3 years. Carious lesions developed in 10 (7.4%) sites (nine teeth, seven children). It was concluded that the resin-based sealant is superior to the glass-ionomer cement in preventing caries, and that the superior retention of the resin probably is an important factor for this.

Adolescent↗
PubMed1991

Bioactive glass particulate material as a filler for bone lesions.

Calcium-phosphate ceramic particulates are often used as filler material for enhanced repair of dental bone defects. Although evidence of bone ingrowth in the scaffold of these particles has been described, it is not observed consistently. Fibrous tissue often encapsulates these particles, which can subsequently become dispersed into the surrounding tissues or even exfoliated. The aim of the present study was to evaluate bioactive glass granules (Biogran) as a filler for osseous lesions, and to compare them with two commercially available Hydroxylapatite (HA) granules. The particulates were implanted in the jaws of five beagle dogs, resected and evaluated after 1, 2, 3, 6 and 12 months of implantation. Histological analysis revealed an improvement in repair of all the lesions. A massive osteoconductive bone growth was seen near the walls of the bony cavities, but in greater amounts around the bioactive glass granules than around the HA materials. On top of this massive growth a trabecular bone growth was observed in the centre of the bony cavities. These trabeculae were associated with the glass particles, which exhibited osteophilic properties, while fibrous tissue separated the bone tissue from the HA particles. The centres of many of the particles are excavated, and are subsequently filled by newly formed bone tissue. This internally formed bone tissue is not necessarily connected to the surrounding bone tissue, and functions as a nucleation site for further bone repair. For the mesenchymal cells within the eroded glass particles this inner environment acts as a stimulus to differentiate into osteoblasts and to start their osteogenetic potential. This phenomenon was not observed around the HA materials. If the latter were surrounded by fibrous tissue, disintegration of the surface by giant cells was observed.

Adhesiveness↗
PubMed1992

Bending strength of Fuji and Ketac glass ionomers after sonication.

Glass ionomer cements mixed by conventional methods contain voids that can decrease their overall strength. This study evaluated the effect of sonication on the reduction of air entrapment by measuring the bending strength in glass ionomer cements (Fujj-II and Ketac-fil). Glass ionomer cement was placed in identical-test vials and sonicated for 45s, 10s, or 0s. The bending strengths were measured (0.005 in min-1) after setting times of 1 or 2 weeks. Mean bending strengths (MPa +/- SD) for the 12 treatment both cements (P < 0.001) and sonication times (P < 0.001). The effect of setting time produced minimal increases in bending strength (P < 0.218). The sonication of freshly mixed glass ionomer cements is a possible solution for reducing voids to increase bending strength.

Analysis of Variance↗
PubMed1994

Adaptation to the cavity floor of the light-cured glass ionomer cement base under a composite restoration.

The study attempted to assess methods of prevention of the formation of a contraction gap in a cylindrical enamel and dentine cavity. The influence has been investigated of the tensile bond strength of cement/dentine and cement/composite resin and the direct tensile strength during setting of light-cured glass-ionomer cements. The interface between composite resin/cement and cement/dentine were viewed and photographed by replica techniques under an SEM (Scanning Electron Microscope). The most noticeable finding was that an enamel and dentine cavity applicated with light- and auto-cured glass-ionomer cement generally presented with a small construction gap at the tooth restoration interface. However, the light-cured glass-ionomer base (Vitrabond) exhibited significantly better tensile bond strength to dentine and resin performance than the conventional glass-ionomer tested. This study revealed that there was no clear relationship between the adhesion to dentine and the adaptation to the dentine cavity floor.

Bicuspid↗
PubMed2006

Effect of adhesive systems associated with resin-modified glass ionomer cements.

The bonding of resin-modified glass ionomer cements to dentin remains a challenge in clinical routine. In an attempt to improve this property, different materials and techniques have been proposed. This study investigated the shear bond strength of resin-modified glass ionomer cements (Vitremer, 3M/ESPE and Fuji II LC Improved, GC) to human dentin using two one-bottle adhesive systems (Prime & Bond 2.1, Dentsply and Single Bond, 3M/ESPE). The restored specimens were stored in deionized water for 24 h at 37 +/- 1 degrees C, and then the bonded surfaces were tested in shear strength using a Universal testing machine at a crosshead speed of 0.5 mm min(-1). Bond strength means were recorded and failure modes were assessed with a stereomicroscope at 40x magnification. Data were submitted to two-way anova and multiple comparisons were performed using a Tukey statistical test (P < 0.05). Fuji II LC Improved yielded higher bond strength (P < 0.05) than Vitremer in all experimental conditions. No statistically significant differences (P > 0.05) were observed among the proposed dentin surface treatments, although a slight decrease in bond strength was observed when phosphoric acid was used alone. Bond strengths of the resin-modified glass ionomer cements to dentin seemed to be more material-dependent than surface treatment-dependent. It may be concluded that the one-bottle adhesive systems tested in this study did not improve the bond strength of the resin-modified glass ionomer cements to dentin.

Acetone↗