Journal of Advanced Materials in Engineering (Esteghlal)

---

---

Tarnish and Corrosion behavior of three Commercial dental amalgams namely Am.1, Am.2, Am.3, have been investigated by utilizing in vitro tests. The corrosion and/or dissolution rate of the three dental amalgams were studied in 0.9 wt% NaCl Solution, artificial saliva and Ringer's solution. Potentiodynamic polarization technique was employed to study cathodic and anodic polarization behavior, from which the corrosion potentials and corrosion current densities were calculated. The corrosion potential and the corrosion current density of each amalgam was found to be affected by the nature of electrolyte used, as well as the Pre-immersion time. However, the order of corrosion potentials and corrosion current densities of the three dental amalgams examined, was found to be independent of the electrolyte used.

---

Hydroxyapatite coatings have been used on metallic substrates in a variety of applications, including modifying the surface of human implants, bone osseointegration and biological fixation. In this paper, the effects of various kinds of metallic substrate on clinical and pathological results of in vivo tests are presented. Four kinds of endodontic implants i.e, stainless steel, cobalt base alloy, plasma sprayed hydroxyapatite coated stainless steel, plasma sprayed hydroxyapatite coated cobalt base alloy were prapared and implanted in mandibular canine of cats. After a healing period of 4 months, investigation by SEM and histopathological interpretation and evaluation showed significant differences in tissue response and osseointegration between coated and non-coated metallic implants. It was concluded that the results were affected by the kind of metallic substrate . Keywords: Hydroxyapatite coating, Dental endodontic implant, Osseointegration, Corrosion, Stainless steel, Cobalt base alloy

---

The presence of defects in cold mercerizing of cotton goods led to the creation of a new method, called hot mercerizing in which caustic soda solution is used at a high temperature. Hot mercerizing is successfully used in cotton blended with some other fibers. In cotton/polyester blend fabrics, this treatment serves a dual purpose: subjectively, it imparts a silklike soft handle to the polyester and brings about mercerizing of the cotton. In this work, the mercerizing operation with caustic soda solution was performed on a 65/35 polyester/cotton fabric in sixteen different temperatures (from 15°C to 90°C), in two states: with tension and without tension. Finally, the effect of temperature of treatment on some properties of fabric such as tensile properties, weight loss, and shrinkage have been studied. Alkali treatment cause weight loss in cotton/polyester blend fabrics, the main part of the weight loss attributed to the polyester component of the blend. Increasing temperature leads to a corresponding increased in weight loss. The resulting weight loss leads to more yarn release and consequently, to the improvement of the drape and soft handle in the fabric. However, it decreases the tensile strength and causes weakness of the fabric, therefore, an optimum of temperature must be considered. In the alkali treatment, the internal stresses in the fabric can be released. Release of tension in the fabric causes shrinkage, particularly in the warp direction. The effect of tension on properties of cotton/polyester blend fabric is not considerable in alkali treatment.

---

The cross-stream migration of a deformable drop in two-dimensional Poiseuille flow at finite Reynolds numbers is studied numerically. In the limit of a small Reynolds number (<1), the motion of the drop depends strongly on the ratio of the viscosity of the drop fluid to the viscosity of the suspending fluid. For a viscosity ratio 0.125, the drop moves toward the centre of the channe while for the ratio 1.0, it moves away from the centre until halted by wall repulsion. The rate of migration increases with the deformability of the drop. At higher Reynolds numbers (5-50), the drop either moves to an equilibrium lateral position about halfway between the centerline and the wall according to the so-called Segre-Silberberg effect or undergoes oscillatory motions. The steady-state position depends only weakly on the various physical parameters of the flow but the length of the transient oscillations increases as Reynolds number is raised, the density of the drop is increased, or the viscosity of the drop is decreased. Once the Reynolds number is high enough, the oscillations appear to persist forever and no steady state is observed. The numerical results are in good agreement with experimental observations, especially for drops that reach steady-state lateral position.

---

The objective of this study was to synthesize glass ionomer–forsterite nanocomposite and study the effect of incorporating forsterite nanoparticles to the ceramic part of glass ionomer cement in order to improve mechanical properties and bioactivity. So, Forsterite nanoparticles were made by the sol-gel process using different weight percentages added to the ceramic part of commercial GIC (Fuji II GC). X-ray diffraction (XRD) was used in order to characterize and determine grain size of the produced forsterite nanopowder. In order to study the mechanical properties of the produced glass ionomer cement-forsterite nanocomposite, the compressive strength (CS), three-point flexural strength (FS) and diametral tensile strength (DTS) of specimens were measured. Statistical analysis was done by one Way ANOVA and differences were considered significant if P‹0.05. The morphology of fracture surface of specimens was studied using scanning electron microscopy (SEM) technique. Bioactivity of specimens was investigated by Fourier transitioned-infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The results of XRD analysis confirmed the nanocrystalline and pure forsterite synthesis. According to the mechanical properties measurements, the optimum weight percentages of forsterite nanoparticles for enhancement of CS, FS, and DTS were obtained equal to 3, 1 and 1 wt.%, respectively. Statistical analysis showed that the differences between all the groups were significant (P<0.05). SEM images and results of the ICP-OES and FTIR tests confirmed the bioactivity of the nanocomposite. Glass ionomer-forsterite nanocomposite containing 1 to 3 wt.%-forsterite nanoparticles can be a suitable candidate for dentistry and orthopedic applications due to the improvement of mechanical properties and bioactivity.

---

In recent years the use of nanomaterials in bone tissue engineering scaffold has been considered due to its imitating the structure of natural bone tissue which contains a nanocomposite structure mixed with a three-dimensional matrix. In the meantime, Polycaprol actone has been used as a bio-polymer in bone tissue engineering applications as a scaffold. The aim of this study is to develop porous scaffolds made of polycaprol actone/layered double hydroxide biocomposite, with appropriate mechanical, bioactive and biological properties, for bone tissue engineering application. The nanocomposite scaffolds were fabricated by the particulate leaching method and freeze-drying method. In this study, MG63 cells (osteosarcoma) was investigated for cellular study. Energy dispersive X-ray analysis confirmed uniform distribution of ceramic phase in polycaprol actone matrix. The results of mechanical tests showed the increase in young’s modulus after addition of ceramic phase. The microscopic investigations demonstrated that the pores generated after addition of ceramic phase and the average size of pores was as large as 100-600μm. Also by the addition of LDH, the hydrophilicity of PCL increased but the rate of hydroxyapatite formation was delayed due to presence of magnesium ions. The cell culture experiments confirmed the attachment and proliferation of cells on the scaffolds. The results showed that the fabricated scaffolds have the potential to be used in cancellous bone tissue engineering.