ali doostmohammadi

Considering the importance of glass-ionomer cements (GICs) in dentistry and their poor mechanical properties, the aim of this study was to improve their mechanical properties by manufacturing a glass-ionomer‒carbon nanotube‒baghdadite nanocomposite by adding carbon nanotubes and baghdadite nanoparticles.
In the present experimental study, carbon nanotubes with 0.5 wt% and baghdadite nanoparticles in 1, 3 and 5 wt% were added to the cement component of a commercial glass-ionomer cement (Fuji ІІ GC) for preparing glass-ionomer‒carbon nanotube‒baghdadite nanocomposite. Then the mechanical properties of the samples were evaluated by the cold compressive strength (CCS), three-point flexural strength (FS) and diametral tensile strength (DTS) tests. In addition, the fractured sample surfaces were evaluated after the compressive strength test under a scanning electron microscope. Data were analyzed with one-way ANOVA at a significance level of p value Based on the results of mechanical tests, the composite containing 0.5 wt% of carbon nanotubes and 1 wt% of baghdadite nanoparticles exhibited the highest compressive strength, diametral tensile strength and flexural strength. In addition, SEM micrographs indicated a decrease in pores in the composite structure and a decrease in stress concentration and propagation of cracks, resulting in an increase in the mechanical strength of samples.
According to the results, the most appropriate sample for dental and orthopedic applications in load-bearing areas is glass-ionomer cement containing 0.5 wt% carbon nanotubes and 1 wt% baghdadite.

Musculoskeletal disorders depend on a variety of factors such as inappropriate body posture; heavy lifting; repetitive actions; and mental, physical, and organizational risk factors. The component manufacturing industry is one of the industries in which direct involvement of the worker in the production process is unavoidable. The present study was carried out with the aim of surveying the prevalence rate of musculoskeletal disorders and assessing the upper limb conditions in employees of a component manufacturing company affiliated to Iran Khodro.
Methods and Materials: This descriptive-analytical study was performed on 50 employees selected from 5 sections in 2016. In this study, Nordic questionnaire was used to determine the prevalence rate of musculoskeletal disorders and then to evaluate the incidence of musculoskeletal disorders.
The results of this study showed that the highest prevalence rates of musculoskeletal disorders in employees of component manufacturing industry during the last 12 months were 58.69, 52.17, and 41.28% in waistline, neck, and wrists, respectively.
Considering the high prevalence rate of musculoskeletal disorders in some of the employees in this industry, it is necessary to consider ergonomic issues, optimize workstations, use the mechanical methods for lifting and moving loads, design the standing-sitting work stations, contract with sports halls, gives overtime work, and design and construct ergonomic chairs.

This work aimed at manufacturing and characterizing of titanium scaffolds which is coated with Akermanite for using in bone tissue engineering. In order to creating titanium scaffolds, the primary titanium powder was prepared with spacer particle elements (sodium chloride). Akermanite coating was prepared through sol-gel method and applied on the scaffold. The prepared structure was evaluated using scanning electron microscopy (SEM). Coated scaffolds were evaluated after heat treatment by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). In terms of assessing the bioactivity of titanium scaffolds, the samples were immersed in simulated body fluid (SBF). Scanning electron microscopy images of the uncoated and coated titanium scaffolds was prepared after 3,7,14 and 21 days immersing in simulated body fluid (SBF); X-Ray Diffraction analysis (XRD) confirmed the peaks of Akermanite phase in coated samples. According to the results, our study showed that coating of Akermanite on Ti scaffold can increase the bioactivity of titanium scaffolds. The final conclusion of this study confirmed that titanium scaffolds coating with Akermanite will be a suitable and useful choice in bone tissue engineering.

Aim: Every year, a huge number of incidents of irreparable damage to personnel and industries occur, most of which are predictable with identifying hazards as well as risk assessment and control. Therefore, in order to prevent occupational accidents, the automotive industry is one of the top priorities for evaluating and identifying the hazards.
The purpose of this study is to identify, control and rank the hazards of actions and processes in the hazardous automotive industry. This descriptive-analytical study was carried out in 2017 in one unit of Iran Khodro Company by using FMEA method. Also to accurately assess the health risks and make decisions for corrective actions to prioritize hazard risks, Wiliam Fine and AHP (Analytical Hierarchy Process) methods were used, respectively.
Findings: In this research, a list of 301 risks in 7 units including cutting line, assembly line, prototyping and modification, manufacturing, packaging, quality control, laboratory, and repair and maintenance were provided. The results of FMEA method indicated that the highest risk priority number (RPN) is related to the risks of particle swirling in grinding operations (336). Moreover, based on the results of William Fine method, the exposure to noise in the Kissing & Wessich Sersim Strandbauft operation was rated at 540 and 500, respectively, with the highest risk of evaluation. The risk of exposure to noise (Kicking operation) with a relative weight of 0/1904 was ranked the first.
The results of the hazard analysis showed that the effect of noise pollution that leads to hearing impairment in the staff is very high.

The aim of this study was to synthesis of glass ionomer-silk fiber composite and to evaluate the effect of adding natural degummed silk fiber on the mechanical properties of glass ionomer cement (GIC). For this purpose, natural degummed silk fibers with 1 mm in length and 13-16 µm in diameter were added to the ceramic component of a commercial glass ionomer cement in 1, 3 and 5 wt. %. Compressive strength (CS), three-point flexural strength (FS) and diametral tensile strength (DTS) of the prepared glass ionomer-silk fiber were measured. Analysis of variance (ANOVA) was used to compare the obtained results. Moreover, SEM technique was used for investigation of the surface morphology of as-prepared composite and fractured area. The results showed that the highest compressive strength, flexural strength and diametral tensile strength were obtained using 3, 3 and 5 wt. % of silk fiber, respectively. However, at 3 wt. % silk fiber, all three measures of strength exhibited a significant increase compared to the commercial GIC. Therefore, it can be suggested that the addition of 3 wt. % silk fiber to the ceramic component of GIC is desired for dental restorations and orthopedic implant applications, where the maximum strength in all three modes of loading would be beneficial.

Statement of Problem: In order to increase the performance of glass ionomer cement, it is reinforced with metal powders, short fibers, bioceramics and other materials. Fluoroapatite (Ca10 (PO4 )6 F2 ) is found in dental enamel and is usually used in dental materials due to its good chemical and physical properties.
In this study, the effects of the addition of synthesized fluoroapatite nanoceramic on the compressive strength and bioactivity of glass ionomer cement were investigated.
The synthesized fluoroapatite nanoceramic particles (~ 70 nm) were incorporated into as-prepared glass ionomer powder and were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Moreover, the compressive strength values of the modified glass ionomer cements with 0, 1, 3 and 5 wt% of fluoroapatite were evaluated.
Results showed that glass ionomer cement containing 3 wt% fluoroapatite nanoparticles exhibited the highest compressive strength (102.6± 4) compared to the other groups, including control group. Furthermore, FTIR and SEM investigations indicated that after soaking the glass ionomer cement- 3 wt% fluoroapatite composite in the simulated body fluid solution, the intensity of O-H, P-O and C-O absorption bands increased as a result of the formation of apatite layer on the surface of the sample, and the rather flat and homogeneous surface of the cement became more porous and inhomogeneous.
Addition of synthesized nano-fluoroapatite to as-prepared glass ionomer cement enhanced the compressive strength as well as nucleation of the calcium phosphate layer on the surface of the composite. This makes it a good candidate for dentistry and orthopedic applications.

Over the past decades, bioactive glass (BG) has been of a great interest in the bone regeneration field, due to its excellent biocompatibility, bioactivity and osteoconductivity. Herein, fabrication of bioactive glass as one-dimensional fibers by employing an Electrospinning process is reported. The Sol-Gel method was chosen considering the final fibers smoothness and homogeneity. Starting sol was prepared by mixing Tetraethyl orthosilicate (TEOS), Triethyl phosphate (TEP) and Calcium Nitrate Tetrahydrate as precursors in an adequate solvent. Fibers were obtained via electrospinning the mixture of different ratios of BG and polymer solutions. Biocompatible Poly(vinyl alcohol) (PVA) was used in order to investigate the polymer effect. Furthermore, electrospinning parameters such as voltage and working distance were examined. Following the heat treatment and depolymerization, X-ray diffractometery (XRD) was done. Besides, fibers morphology before and after calcination was observed in detail employing Optical Microscopy (OM) and Field Emission Scanning Electron Microscopy (FE-SEM). XRD patterns revealed the presence of bioactive glass. Results indicated that the fibers diameter and homogeneity were reduced after calcination showing an intensification as polymer increased.

This study aimed at preparing and characterizing fluor-hydroxyapatite (FHA) nanocrystals using the sol-gel process. Phosphorus pentoxide، calcium nitrate، and hexafluoro acid were used as the sources of phosphorus، calcium، and fluorine to achieve the stochiometric ratio of 5 for calcium to fluorine، and 1. 67 for calcium to phosphorus، respectively. In order to characterize and evaluate the properties of the particles، methods of elemental analysis (XRF)، phase analysis (XRD)، fourier transform infrared spectroscopy (FTIR)، scanning electron microscope (SEM)، and transmission electron microscope (TEM) were applied. The elemental analysis showed that the required oxides and elements deos exist in the compound in desired amounts. The results of XRD confirmed the structure of fluorapatite. The sizes of the crystallites estimated from XRD patterns using the Scherrer equation was about 40 nm. FTIR analysis proved the partial substitution of ion F with OH and the formation of fluorapatite. SEM and TEM images showed that the fluorapatite nanoparticles less than 50 nm were formed having spherical shapes. The results indicated that it is possible to prepare fluor-hydroxy apatite nanocrystals with desired composition and structure through sol-gel method.

The most important limitation of glass ionomer cements (GICs) is the weak mechanical properties. Our previous research showed that higher mechanical properties could be achieved by addition of forsterite (Mg2SiO4) nanoparticles to ceramic part of GIC. The objective of the present study was to fabricate a glass ionomer- Mg2SiO4 nanocomposite and to evaluate the effect of addition of Mg2SiO4 nanoparticles on bioactivity and fluoride release behavior of prepared nanocomposite. Forsterite nanoparticles were made by sol-gel process. X-ray diffraction (XRD) technique was used in order to phase structure characterization and determination of grain size of Mg2SiO4 nanopowder. Nanocomposite was fabricated via adding 3wt.% of Mg2SiO4 nanoparticles to ceramic part of commercial GIC (Fuji II GC). Fluoride ion release and bioactivity of nanocomposite were measured using the artificial saliva and simulated body fluid (SBF), respectively. Bioactivity of specimens was investigated by Fourier transitioned-infrared spectroscopy (FTIR), scanning electronmicroscopy (SEM), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and registration of the changes in pH of soaking solution at the soaking period. Statistical analysis was carried out by one Way analysis of variance and differences were considered significant if P < 0.05. The results of XRD analysis confirmed that nanocrystalline and pure Mg2SiO4 powder was obtained. Fluoride ion release evaluation showed that the values of released fluoride ions from nanocomposite are somewhat less than Fuji II GC. SEM images, pH changes of the SBF and results of the ICP-OES and FTIR tests confirmed the bioactivity of the nanocomposite. Statistical analysis showed that the differences between the results of all groups were significant (P < 0.05). Glass ionomer- Mg2SiO4 nanocomposite could be a good candidate for dentistry and orthopedic applications, through of desirable fluoride ion release and bioactivity.

Glass-ionomer cements (GICs) are one of the most important restorative materials in dentistry. Similarly, hydroxyapatite (HA) is of the most well known bioceramics. The aim of this study was to prepare a type of glass-ionomer cement with nano-particles of hydroxyapatite to improve GIC bioactivity and compressive strength. Natural HA particles were extracted from animal bone. The ceramic component of GIC was produced by melting and characterized. HA particles were incorporated into the cement component of GI at 1, 3, 5 and 7 weight percentages. Bioactivity and compressive strength of GIC\HA composite were evaluated in a simulated body fluid (SBF). One-way ANOVA was used for data analysis (n = 3). The results of characterization tests confirmed the production of GIC using the melting technique. Amorphous and glassy structure of GIC powder and its proper chemical composition were verified by characterization tests. The results of soaking test in SBF showed increased bioactivity of GIC/HA composite. Finally, the results of compressive tests showed that incorporating HA up to 5 wt% would not decrease the compressive strength of GIC. GIC/HA nano-composite with 5 wt% of HA was the most appropriate sample regarding its bioactivity and mechanical properties for dental applications. Introducing this novel nano-composite can play an important role in improving the properties of glass-ionomer cements.

Reduced time and appropriate bond strength of brackets is one of the most important aspects of orthodontic treatments. Prolonged halogen light curing for bonding of brackets is undesirable, so the purpose of this study was to compare the shear bond strength of brackets bonded with halogen light and plasma arc system.Materials and Mehods: This was an experimental in vitro study. A total of 60 intact premolar teeth were collected and divided into four groups. Stainless steel orthodontic brackets were bonded to them. In groups 1 and 2, curing was done using halogen light given for 20 seconds from two and four angles. In groups 3 and 4, curing was carried out using the plasma arc system for 6 seconds from two and four angles. The shear bond strength was recorded by Instron. The statistics of ANOVA, Tukey’s test, and T-test were used in data analysis. There was a statistically significant difference in shear bond strength among the four groups (P = 0.043) and between group 1 with group 2 (P = 0.035). Yet, there was no statistically significant difference between brackets bonded with plasma arc and those bonded with halogen light or between the two groups of plasma arc. Using the plasma arc system is superior to other methods due to reduced curing time. Also, since in using the halogen light system, an increase in curing periods from different angles resulted in a significant increase in shear bond strength; it is advisable to apply the halogen light from different angles.

The aim of this work was evaluating of zirconia nanoparticles’ effect on physical and mechanical properties of dental glass ionomer cements (GICs). Ceramic part of GIC was prepared using melting method and zirconia nanoparticles were added to GIC in 1, 3 and 5 weight percent. Characterization tests and compressive strength evaluation of nanocomposite samples were carried out. The XRD results showed that the prepared ceramic part of GIC was completely amorphous and can be used as the matrix of composite. The result of XRF showed that the chemical composition of ceramic part of GIC was similar to expected composition. Also the results of mechanical properties determination analysis showed that the addition of zirconia nanoparticles to GIC could improve the compressive strength. The maximum of this strength obtained using 1% wt of GIC in zirconia composite. Increasing the nanoparticles content resulted in decrease of compressive strength but the strength of composite with any composition was more than the strength of control sample. According to the results of this study, the most proper composite was the one containing1%wt zirconia nanoparticles.

Bioactive bioceramics have been regarded by researchers in recent years. Bioglass and Hydroxyapatite (HA) are the examples of these bioactive bioceramics. Production and characterization of nano bioglass and HA for bone repair applications were the purpose of this study. Nano bioglass and HA were produced and the particles shape and size were characterized by X-ray flurescence (XRF). The bioactivity of the particles of HA and nano bioglass and combination of the two were tested، by introducing them into the cavities formed in rabbit''s Tibia. The incorporation and bone induction of these 3 different paricles in bone were evaluated by radiography and also histopathology of the resected specimens. The characterized tests confirmed that nano bioglass and natural HA were produced with desired composition. The radiographic and histopathologic evaluation illustrated good bioactivity of nano-size bioglass، HA and HA-bioglass composite، leading to restoration of bone defects after 4 to 6 weeks. It was also observed that bioactivity of HA-bioglass composite was superior to bioglass and HA used singularly. The osteoconductivty of HA and osteoinductivity of bioglass combined as a composite lead to excellent bioactivity and good response in the hard bony tissue.

The aim of this work was preparation, development and characterization of bioactive glass coating by sol–gel technique for improvement of biocompatibility of 316L stainless steel implant used in dentistry and orthopaedic surgery. Bioglass powder was made by sol–gel technique and thermal properties of the prepared powder were studied using differential thermal analysis (DTA). The prepared bioglass powder was immersed in the simulated body fluid (SBF) solution. Fourier transform infrared spectroscopy (FTIR) was utilized to recognize and confirm of the formation of apatite layer on prepared bioglass powder. Bioactive bioglass coating was performed on 316L stainless steel (SS) substrate by the sol–gel technique. Structural characterization techniques including XRD, SEM and EDX were used to investigate the microstructure and morphology of the coating. Electrochemical potentiodynamic polarization tests were performed in two different types of physiological solutions at 37 ◦C in order to determine and compare the corrosion behavior of the bioglass coated SS and uncoated specimens as an indication of biocompatibility. The formation of apatite layer confirmed the bioactivity of the bioglass powder and tests revealed that all the films signs of bioactivity. It was also found that at sintering temperatures above 900 ◦C, crystalline phase Ca2SiO4 was formed. Crack-free and homogeneous bioglass coatings were obtained with no observable defects. The bioglass coating also improved corrosion resistance of the 316L SS substrates such as the corrosion current density of coated samples in comparison with pristine samples was decreased.It was concluded that the sol–gel bioglass coating can improve the corrosion behavior of dental and orthopedic metallic implants and two goals including improvement of biocompatibility and bone osteointegration can be obtained simultaneously.

Due to its ability in bonding with hard and soft tissue, healing and repairing of the bone, and proper replacing of the ossicles in middle ear, bioactive glass has come into considera­tion. The aim of this work was preparation, development and characterization of nanopowder bioactive glass obtained by the sol-gel technique. Bioglass powder was made by sol-gel technique and the presence of desired ele­ments is tested by X-ray fluorescence analysis. Trans Electronic Microscopic (TEM) technique was used to evaluate the powders shape and size. The prepared bioglass powder was immersed in the simu­lated body fluid solution for 30 days. Fourier transform infrared (FTIR) spectroscopy was util­ized to recognize and to confirm the formation of apatite layer on prepared bioglass powder. (XRD) as a structural characterization technique was used to investigate the microstructure. The glass powder size was less than 100 nanometers. The formation of apatite layer con­firmed the bioactivity of the bioglass powder and tests revealed that all the films had the signs of bioactiv­ity. It was also found that at sintering temperatures above 900 ºC, crystalline phase Ca2SiO4 was formed. The sol-gel nanopowder bioglass can be used as a replacement for small bones such as ossi­cles in middle ear, and it leads to bone osteointegration and growth of the surrounding tissue.