The paper discusses the influence of sintering temperature on the microstructure and strength of hydroxyapatite ceramics prepared using the extrusion process. The average pore diameters observed were in the range of approximately 150mm to 300mm whereas the compaction strength was found to be around 120-160 MPa.
Hydroxyapatite, (HA; Ca1O(PO4)6(OH)2) has been successfully applied in medical and dental applications for several years due to its excellent biocompatibility. The usage of HA in Malaysia, however, is limited due to the lack of availability. Therefore the aim of this work is to produce HA materials from both pure chemicals and from Malaysian natural limestone precursors, and to compare their bulk properties. However, parts of Malaysian natural limestone deposits actually consist of a combination of Ca(OH)2 and CaCO3. In order to utilise the limestone to produce HA material, the combination of these commercially pure chemicals as HA precursors should still work. In order to test this hypothesis, two HAs were produced by wet synthesis technique utilising (a) combination of Ca(OH)2 + CaCO3 from pure commercial chemicals [WCC] and (b) a local natural limestone [WL] precursors. The HAs produced; WCC and WL, were compacted into discs and sintered at 1250 degrees C. The characterisations and evaluations conducted were XRD, SEM-EDX, FTIR and shrinkage factor. The results indicate that WL gives slightly better bulk properties compared to WCC.
In attempt to discover a small active compound that could promote adipogenesis, we investigated the ability of cinnamon (Cinnamomum zeylanicum) extracts to stimulate 3T3-L1 preadipocytes, In this study, we designed an experiment by replacing insulin with cinnamon extracts. The differentiated of 3T3-L1 adipocytes were monitored using oil red O staining method. Induction of adipocyte formation by cinnamtannin B1 or water extract gave the similar effects to insulin activity in adipogenesis.
Hydroxyapatite (HA) has been earmarked as suitable for implantation within the human of its chemical makeup to human bone. In this paper, HA powders were synthesized via the precipitation method where phosphoric acid (H3PO4) was titrated into calcium hydroxide solution [Ca(OH)2]. Two parameters such as temperature and stirring rate were identified as factors that influenced the amount and purity of HA powder. Phase identification of the synthesized powder was done using X-Ray Diffraction (XRD). The results show that HA phase can be synthesized from this titration process of Ca(OH)2 and H3PO4 with yield amount of HA powder around 45 - 61 grams but with less than hundred percent purity. In order to study the effect of heat treatment to HA crystals structure, HA powder was calcined at 850 degrees C for 2 hours. It's found that the degree of crystallinity increases after calcination because of lattice expansion when the materials were heated at higher temperature
This study was designed to evaluate the ability of natural coral implant to provide an environment for marrow cells to differentiate into osteoblasts and function suitable for mineralized tissue formation. DNA content, alkaline phosptatase (ALP) activity, calcium (Ca) content and mineralized nodules, were measured at day 3, day 7 and day 14, in rat bone marrow stromal cells cultured with coral discs glass discs, while cells alone and coral disc alone were cultured as control. DNA content, ALP activity, Ca content measurements showed no difference between coral, glass and cells groups at 3 day which were higher than control (coral disc alone), but there were higher measurement at day 7 and 14 in the cell cultured on coral than on glass discs, control cells and control coral discs. Mineralized nodules formation (both in area and number) was more predominant on the coral surface than in control groups. These results showed that natural coral implant provided excellent and favorable situation for marrow cell to differentiate to osteoblasts, lead to large amount of mineralized tissue formation on coral surface. This in vitro result could explain the rapid bone bonding of coral in vivo.
The strategy used to generate tissue-engineered bone construct, in view of future clinical application is presented here. Osteoprogenitor cells from periosteum of consenting scoliosis patients were isolated. Growth factors viz TGF-B2, bFGF and IGF-1 were used in concert to increase cell proliferation during in vitro cell expansion. Porous tricalcium phosphate (TCP)-hydroxyapatite (HA) scaffold was used as the scaffold to form 3D bone construct. We found that the addition of growth factors, greatly increased cell growth by 2 to 7 fold. TCP/HA proved to be the ideal scaffold for cell attachment and proliferation. Hence, this model will be further carried out on animal trial.
The appearance of dental porcelains is comparable to natural teeth. This study discusses the effect of Y2O3 addition to the fluorescent property of dental porcelains. The composition of dental porcelains contained Y2O3 as the fluorescent agent and base frit. The combinations of Y2O3 added consist of a series with 0.5, 1.0, 1.5, 2.0 and 2.5 wt% respectively, based on the total composition. In the extreme condition, fluorescent agents are added from 5.0 up to 10.0 wt%. In order to enhance the fluorescent property of dental porcelains, an opacifiying agent, cerium oxide (CeO2) was also added to dental porcelains composition. The fluorescent property was determined using Spectroline EF-1400C/F that emits 240 nm wavelength ultraviolet light. The microstructure was examined by Scanning Electron Microscope (SEM). The result shows that, the fluorescent properties displayed are similar to natural teeth when subjected to ultraviolet light. SEM micrograph was able to show the fluorescent agent dispersed in glass phase. Increasing additions of Y2O3 gave the fluorescent properties near to natural teeth.
The standard bioglass composition GS45 as well as with excess silica GS50 or with the addition of 5% titanium oxide GS45+Ti5, were prepared by the polymeric route. The different glass components were added to the formed polymer. Firing at 700 degrees C gave an amorphous product with microporous texture that readily crystallizes out at 900 degrees C. The prepared materials were highly porous with two modes of pore system micro-pores and macro-pores with a size ranging between 100 microm to 0.006 microm and a porosity reaching 73%. The measured bulk density was between 0.36 to 1.1g/cm3. The fired material preserved the former structure of the polymer precursor. Biocompatibility was verified in vitro and vivo. IR of the specimens previously immersed in SBF revealed the formation of apatite like layer. While the histology sections of implants in rate femurs showed new bone tissue or bone trabeculae after 21 days.
Bone marrow stem cells (BMSC), known for its multipotency to differentiate into various mesenchymal cells such as chodrocyte, osteoblasts, adipocytes, etc, have been actively applied in tissue engineering. BMSC have been successfully isolated from bone marrow aspirate and bone marrow scraping from patients of various ages (13-56 years) with as little as 2ml to 5ml aspirate. BMSC isolated from our laboratory showed the presence of a heterogenous population that showed varying prevalence of surface antigens and the presence of telomerase activity albeit weak. Upon osteogenic induction, alkaline phosphatase activity and mineralization activity were observed.
Our objective is to determine the quality of tissue engineered human skin via immunostaining, RT-PCR and electron microscopy (SEM and TEM). Culture-expanded human keratinocytes and fibroblasts were used to construct bilayer tissue-engineered skin. The in vitro skin construct was cultured for 5 days and implanted on the dorsum of athymic mice for 30 days. Immunostaining of the in vivo skin construct appeared positive for monoclonal mouse anti-human cytokeratin, anti-human involucrin and anti-human collagen type I. RT-PCR analysis revealed loss of the expression for keratin type 1, 10 and 5 and re-expression of keratin type 14, the marker for basal keratinocytes cells in normal skin. SEM showed fibroblasts proliferating in the 5 days in vitro skin. TEM of the in vivo skin construct showed an active fibrocyte cell secreting dense collagen fibrils. We have successfully constructed bilayer tissue engineered human skin that has similar features to normal human skin.
Various proportions of chitosan/collagen films (70/30% to 95/05%) w/w were prepared and evaluated for its suitability as skin regenerating scaffold. Interactions between chitosan and collagen were studied using Fourier Transform Infrared spectroscopy (FTIR) and Differential Scanning Colorimetry (DSC). Scanning Electron Microscope (SEM) was used to investigate the morphology of the blend. Mechanical properties were evaluated using a Universal Testing Machine (UTM). The chitosan/collagen films were found to swell proportionally with time until it reaches equilibrium. FTIR spectroscopy indicated no chemical interaction between the components of the blends. DSC data indicated only one peak proving that these two materials are compatible at all proportions investigated. SEM micrographs also indicated good homogeneity between these two materials.
Among the various biomaterials available for tissue engineering and therapeutic applications, microbial polyhydroxyalkanoates (PHAs) offer the most diverse range of thermal and mechanical properties. Of particular interest are the PHAs that contain 4-hydroxybutyrate such as poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB) and poly(4-hydroxybutyrate) [P(4HB)]. These polyesters can only be synthesized by a few types of bacteria, among which Comamonas acidovorans has the most efficient metabolic pathways to channel 4HB monomers. The resulting polyesters are bioabsorbable and are being developed as a new biomaterial for medical applications. By controlling the molar ratio of the monomers, it is possible to produce materials that are as tough and elastic as rubber.
Linear polymers have been commonly used as dental composite. However the aim of this work is to use hyperbranched polymer in an attempt to produce dental composite. The reason is because the dendritic molecules have shown low viscosity at higher molecular weight compared to the linear counterparts. Therefore, this work attempts to substitute the linear polymer with as much of hyperbranched polymer in the dental composite that would pass the required ISO 4049:1998(E) "Dentistry - Resin-based filling material". Several formulations of dental composites were used, i.e. combinations of linear-linear and linear-hyperbranched polymers for comparison. Following this, physical and mechanical characterisation were conducted based on the ISO standards such as water sorption and water solubility. Other characterisation such as polymerisation shrinkage and Vickers hardness were also evaluated. It was found that different types of resins give different physical and mechanical properties. The maximum achievable hyperbranched polymer, which passes the required ISO standard, that can be incorporated in the linear polymer to form dental composite is 43% wt.
The aim of this study was to evaluate the effect of powder-to-liquid ratio on the glass transition temperature (Tg) and the tensile properties of denture base material prepared from poly (methyl methacrylate) (PMMA) and hydroxyapatite (HA) previously treated with 3-trimethoxysilylpropyl methacrylate (gamma-MPS). Specimens for mechanical testing were prepared by adding composites powder (PMMA, BPO and HA) to the monomer (MMA and EGDMA) followed by hand mixing as in dental laboratory description usage. The glass transition temperature was studied by using differential scanning calorimetry (DSC). It was observed that the tensile properties and the Tg were affected by the powder-to-liquid ratio. The mechanical characterization of the materials were performed by using single edge notch-tension (SEN-T) specimens; the fracture toughness was slightly higher in formulation which contained HA filler compared to commercial denture base material.
The effect of hemodialysis on the mechanical behavior of a cellulosic Hemophane ME-IOH and one Polysulfone type hollow fibers was investigated. Mechanical tests showed that the deformation of polysulfone type of hollow fibers is entirely different than that of the other dialyser for the samples used and unused in hemodialysis. All the samples exposed to the dialysis showed decreased in ductility. Fracture surface studies proved that there was some alignment on the fracture surface. XRD and DSC experiments revealed structural changes had occurred.