جستجوی مقالات مرتبط با کلیدواژه « glass » در نشریات گروه « پزشکی »

In the present study, we investigated the effect of two doses of atropine eye drops versus placebo on myopia progression in children and adolescents.

In this double‑blind, randomized clinical trial, 67 patients aged 6 to 18 years with myopia of ‑2 to ‑6 D were enrolled and randomized to receive a placebo eye drop, atropine 0.1%, or 0.01% ophthalmic solution (one drop per night for 6 months). All participants were followed‑up with for one year after the beginning of the study (at zero, one, three, six, and 12 months) and their spherical equivalent (SE), axial length (AL), anterior chamber depth (ACD), and far and near visual acuity (VA) and the eye drops side effects were recorded. A comparison among the groups was performed using SPSS software, version 24.0.

Spherical equivalent, AL, and ACD decreased and far VA improved in atropine groups to a greater extent than the placebo group (P < .05) at the 6‑month follow‑up. The most common side effects of atropine 0.1% eye drop included photophobia and decreased near VA. At the end of the study (six months after the cessation of atropine), a rebound effect was observed; this effect was especially severe in the 0.1% atropine group.

Atropine eye drops are effective for slowing down and preventing myopia progression. However, without long‑term treatment, they will have a rebound effect. A lower dose (0.01%) is suggested for reducing the side effects and rebound effects.

Low-density bulk metallic glass (BMG) with good structural characteristics has the potential of being used for structural radiation shielding purposes. This study was conducted on two new low-density titanium (Ti)-based BMGs (i.e., Ti32.8Zr30.2Ni5.3Cu9Be22.7 and Ti31.9Zr33.4Fe4Cu8.7Be22) to investigate their photon and fast neutron shielding capacities.

The mass attenuation coefficients, half-value layers, effective atomic numbers, and exposure buildup factors of the two BMGs were calculated at the photon energy values of 15 keV and 15 MeV. Computation of mass attenuation coefficients and effective atomic numbers was accomplished using the XCOM and auto-Zeff software, respectively. In addition, the geometric progression procedure-based computer code EXABCal was used for calculating the exposure buildup factors of BMG. The fast neutron removal cross-sections were also calculated for the two BMGs. The calculated photon and fast neutron shielding parameters for BMGs were compared with those of lead (Pb), heavy concrete, and some recently developed glass shielding materials and then analyzed according to their elemental compositions.

The results showed that though Pb had a better photon shielding capacity, Ti-BMG attenuated photons better than heavy concrete. Furthermore, BMG had a higher neutron removal cross-section, compared to heavy concrete and some recently developed glass shielding materials. The neutron removal cross-sections of Ti32.8Zr30.2Ni5.3Cu9Be22.7 and Ti31.9Zr33.4Fe4Cu8.7Be22 were obtained as 0.1663 and 0.1645 cm-1,respectively.

his study revealed that Ti-based BMG with high strength and low density have potential applications in high-radiation environments, particularly in nuclear engineering for source and structural shielding.

Ingestion of foreign bodies is common and conservative treatment can eliminated most particlesfrom the gastrointestinal tractunless peritoneal signs appear. A 22-year-old man presented to emergency department who had ingested glass particles of a crushed beverage bottle. He complained of epigastric and periumbilical pain. Physical examination did not revealany peritoneal signs. Abdominal X-ray showed stomach full of small glass particles. Conservative treatment, without any surgical intervention,resulted insafely eliminating glass particlesin this patient.

Statement of the Problem: The usage of glass ionomer cements (GICs) restorative materials are very limited due to lack of flexural strength and toughness.
The aim of this study was to investigate the effect of using a leucite glass on a range of mechanical and optical properties of commercially available conventional glass ionomer cement.
Ball milled 45μm leucite glass particles were incorporated into commercial conventional GIC, Ketac-Molar Easymix (KMEm). The characteristics of the powder particles were observed under scanning electron microscopy. The samples were made for each experimental group; KMEm and lucite- modified Ketac-Molar easy Mix (LMKMEm) according to manufacturer’s instruction then were collected in damp tissue and stored in incubator for 1 hour. The samples were divided into two groups, one stored in distilled water for 24 hours and the others for 1 week.10 samples were made for testing biaxial flexural strength after 1 day and 1 week, with a crosshead speed of 1mm/min, calculated in MPa. The hardness (Vickers hardness tester) of each experimental group was also tested. To evaluate optical properties, 3 samples were made for each experimental group and evaluated with a spectrophotometer. The setting time of modified GIC was measured with Gillmore machine.
The setting time in LMKMEm was 8 minutes. The mean biaxial flexural strength was LMKMEm/ 1day: 24.13±4.14 MPa, LMKMEm/ 1 week: 24.22±4.87 MPa KMEm/1day:28.87±6.31 MPa and KMEm/1 week: 26.65±5.82 MPa which were not statistically different from each other. The mean Vickers hardness was LMKMEm: 403±66 Mpa and KMEm: 358±22 MPa; though not statistically different from each other. The mean total transmittance (Tt) was LMKMEm: 15.9±0.7, KMEm: 22.3±1.2, the mean diffuse transmittance (Td) was LMKMEm: 12.2±0.5, KMEm: 18.0±0.5 which were statistically different from each other.
Leucite glass can be incorporated with a conventional GIC without interfering with setting time. Yet, it did not improve the mechanical and optical properties of the GIC.

Statement of the Problem: The adhesion of resin-modified glass-ionomer (RMGI) to composite resin has a very important role in the durability of sandwich restorations. Hydroxyapatite is an excellent candidate as a filler material for improving the mechanical properties of glass ionomer cement.
The aim of this study was to assess the effect of adding micro- and nano-hydroxyapatite (HA) powder to RMGI on the shear bond strength (SBS) of nanofilled and silorane-based composite resins bonded to RMGI containing micro- and nano-HA.
Sixty cylindrical acrylic blocks containing a hole of 5.5×2.5 mm (diameter × height) were prepared and randomly divided into 6 groups as Group 1 with RMGI (Fuji II LC) plus Adper Single Bond/Z350 composite resin (5.5×3.5 mm diameter × height); Group 2 with RMGI containing 25 wt% of micro-HA plus Adper Single Bond/Z350 composite resin; Group3 with RMGI containing 25 wt% of nano-HA plus Adper Single Bond/Z350 composite resin; Group 4 with RMGI plus P90 System Adhesive/P90 Filtek composite resin (5.5×3.5 mm diameter × height); Group 5 with RMGI containing 25 wt% of micro-HA plus P90 System Adhesive/P90Filtek composite resin; and Group 6 with RMGI containing 25 wt% of nano-HA plus P90 System Adhesive/P90 Filtek composite resin. The specimens were stored in water (37° C, 1 week) and subjected to 1000 thermal cycles (5°C/55°C). SBS test was performed by using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed by two-way ANOVA and Tukey test (p There were significant differences between groups 1 and 4 (RMGI groups, p= 0.025), and groups 3 and 6 (RMGI nano-HA groups, p= 0.012). However, among Z350 and P90 specimens, no statistically significant difference was detected in the SBS values (p= 0.19, p= 0.083, respectively).
RMGI containing HA can improve the bond strength to methacrylate-based in comparison to silorane-based composite resins. Meanwhile, RMGI without HA has the best bond strength to silorane-based composite resins.

Background. This study evaluated the effect of two prophylaxis techniques on the marginal gap of CI V resin-modified glass-ionomer restorations.
Methods. Standard Cl V cavities were prepared on the buccal surfaces of 48 sound bovine mandibular incisors in this in vitro study. After restoration of the cavities with GC Fuji II LC resin-modified glass-ionomer, the samples were randomly assigned to 3 groups of 16. In group 1, the prophylactic procedures were carried out with rubber cup and pumice powder and in group 2 with air-powder polishing device (APD). In group 3 (control), the samples did not undergo any prophylactic procedures. Then the marginal gaps were measured. Two-way ANOVA was used to compare marginal gaps at the occlusal and gingival margins between the groups. Post hoc Tukey test was used for two-by-two comparisons. Statistical significance was set at P Results. There were significant differences in the means of marginal gaps in terms of prophylactic techniques (P Conclusion. The prophylactic techniques used in this study had a negative effect on the marginal gaps of Cl V resin-modified glass-ionomer restorations.

Removal of enamel superficial layer during microabrasion treatments may adversely affect sealing ability of the restorative materials. The aim of this study was to measure the effect of different periods of enamel microabrasion on the microleakage of class V glass-ionomer restorations. This in vitro experimental study was conducted on 96 Class V cavities which had been prepared on the buccal and lingual surfaces of 48 sound human premolars. After conditioning with 10% polyacrylic acid (GC, Tokyo, Japan) one half of the cavities were restored with the conventional glass-ionomer (Fuji II GC, Tokyo, Japan) and another half with resin-modified glass-ionomer (Fuji II LC GC, Tokyo, Japan). Finishing and polishing were performed after 24 hours and the teeth incubated for 2 weeks (37°C and 100% humidity).Then the teeth were classified into eight groups (n=12). Microabrasion treatment was performed with Opulster (Ultradent product Inc, South Jordan, UT, USA) in 0(control no treatment), 60, 120 and 180 seconds. Then teeth were thermocycled between 5°C-55°C (×1000), immersed in 0.5% basic-fushin solution (24h) and sectioned longitudinally in bucco-lingual direction (n=192). Dye penetration was examined with stereomicroscope (×40). Microleakage scores were statistically analyzed by Kruskal-Wallis test while the paired comparisons were done using Mann-Whitney U test. The mean microleakage scores were significantly increased following increased microabrasion times in occlusal margin in FU II (p<0.009) and FU II LC (p<0.02) and in gingival margin in resin-modified glass-ionomer (p<0.04). In Fuji II restorations after microabrasion in occlusal margins, microleakage increased up to 120s but in gingival margins no significant difference were seen. In Fuji II LC restorations after microabrasion in occlusal margin, microleakage from 60s up to 180s was significantly increased. In gingival margin with increasing the time up to 180s microleakage increased.

The clinical success of sandwich technique depends on the strength of resin-modified glass ionomer cement (RMGIC) bonding to both dentin and resin composite. Therefore, the shear bond strength (SBS) of resin composite bonded to RMGIC utilizing different resin adhesives versus a GIC-based adhesive was compared. In this in vitro study, 84 holes (5×2 mm) were prepared in acrylic blocks, randomly divided into seven groups (n=12) and filled with RMGIC (Light-Cured Universal Restorative, GC). In the Group I; no adhesive was applied on the RMGIC. In the Group II, non-etched and Group III was etched with phosphoric acid. In groups II and III, after rinsing, etch-and-rinse adhesive (OptiBond Solo Plus); in the Group IV; a two-step self-etch adhesive (OptiBond XTR) and in Group V; a one-step self-etch (OptiBond All-in-One) were applied on the cement surfaces. Group VI; a GIC-based adhesive (Fuji Bond LC) was painted over the cement surface and cured. Group VII; the GIC-based adhesive was brushed over RMGIC followed by the placement of resin composite and co-cured. Afterward; resin composite (Point 4) cylinders were placed on the treated cement surfaces. The specimens were placed in 100% humidity at 37 ± 1°C and thermo cycled. The shear bond test was performed at a cross-head speed of 1 mm/min and calculated in MPa; the specimens were examined to determine mode of failure. The results were analyzed using one-way ANOVA and Tukey test. The maximum (24.62±3.70 MPa) and minimum (18.15±3.38 MPa) SBS mean values were recorded for OptiBond XTR adhesive and the control group, respectively. The pairwise comparisons showed no significant differences between the groups that bonded with different adhesives. The adhesive failure was the most common failure mode observed. This study suggests that GIC-based adhesive could be applied over RMGIC as co-cure technique for sandwich restorations in lieu of employing the resin adhesives

Glass and quartz fiber posts are used in restoration of structurally compromised roots. Accessory fiber posts are recently introduced to enhance the fiber post adaptation. This study evaluated the effectiveness of glass versus quartz accessory fiber posts. In this experimental study, 40 mandibular premolar roots with similar dimension (radius of 3.5 ± 0.2 mm and length of 13 ± 0.5 mm) were selected and their root canals were flared until 1.5 mm of dentin wall remained. They were randomly assigned to four groups (n = 10) and restored as follows: Exacto glass fiber post (EX), Exacto glass fiber post + 2 Reforpin accessories (EXR), D. T. Light quartz fiber post (DT), and D. T. Light quartz fiber post + 2 Fibercone accessories (DTF). All posts were cemented with Duo-Link resin cement and the cores were built with the particulate filler composite. Following 1-week water storage, specimens were subjected to fracture loads in a universal testing machine. The maximum loads and failure modes were recorded and analyzed with the two-way analysis of variance (ANOVA) and Fisher’s exact tests (a = 0.05). The mean fracture resistance values (N) were 402.8 (EX), 378.4 (EXR), 400.1 (DT), and 348.5 (DTF). Two-way ANOVA test showed neither reinforcing method (P = 0.094), nor post composition (P = 0.462) had statistically significant differences on fracture resistance of the structurally compromised premolar teeth. Fisher’s exact test also demonstrated no statistically significant difference regarding two variables (P = 0.695). Core fracture was the most common failure mode (62.5%). Glass and quartz fiber posts with or without accessories restored the weakened premolar roots equally.

Materials used in the body, especially the materials used in various oral cavity regions should be stable and passive without any interactions with the body tissues or fluids. Dental amalgam, c omposite resins and dental cements are the materials of choice with such properties. The first attempts to produce active materials, which could interact with the human body tissues and fluids were prompted by the concept that fluoride-releasing materials exert useful effects in the body. The concept of using the “smart” materials in dentistry has attracted a lot of attention in recent years. Conventional glass-ionomer (GI) cements have a large number of applications in dentistry. They are biocompatible with the dental pulp to some extent. GI is predominantly used as cements in dentistry; however, they have some disadvantages, the most important of which is lack of adequate strength and toughness. In an attempt to improve the mechanical properties of the conventional GI, resin-modified glass-ionomers have been marketed, with hydrophilic monomers, such as hydroxyethyl methacrylated (HEMA). Some recent studies have evaluated GI with bioactive glass in its structure to validate the claims that such a combination will improve tooth bioactivity, regeneration capacity and restoration. There is ever-increasing interest in the application of bioactive materials in the dental field in an attempt to remineralize affected dentin. The aim of this review article is to evaluate these materials and their characteristics and applications.