Alva Edy Tontowi

Porous Hydroxyapatite–Zirconia Composites Prepared by Powder Deposition and Pressureless Sintering

In the present study, hydroxyapatite was synthesized from local gypsum by microwave-hydrothermal method. Different percentage amounts of zirconia (0, 20, 30 and 40 wt.%) and poly-methyl methacrylate (40, 50 and 60 wt.%) mixed with hydroxyapatite (HA) for six hours. These powder mixture were deposited using deposition machine to produce specimens. These specimens were sintered at a temperature of 140°C with holding time for 1 hour into the green parts. These green parts were sintered at temperature of 1450°C with holding time for 2 hours. This process produces porous hydroxyapatite-zirconia composites with porosity between 62.76-73.92 percent. These composites were examined by XRD, XRF, SEM-EDX, BET analysis and compressive strength testing. Compressive strength of porous hidroxyapatite-zirconia composite decreased from 3.706 to 0.039 MPa when percentage amounts of zirconia increased up to 40 wt.%. This caused by several factors i.e. increased porosity, grain zirconia cracked, zirconia reacted with HA to produce CaZrO3, β-TCP and α-TCP, HA matrix cracks because of the phase change of tetragonal-zirconia into monoclinic-zirconia.

The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth

Synthetic hydroxyapatite (HA) has been widely used and developed as the material for bone substitute in medical applications. The addition of zirconia is needed to improve the strength of hydroxyapatite as the bone substitute. One of the drawbacks in the use of biomedical materials is the occurrence of biomaterial-centred infections. The recent method of limiting the presence of microorganism on biomaterials is by providing biomaterial-bound metal-containing compositions. In this case, S. epidermidis is the most common infectious organism in biomedical-centred infection. Objective. This study was designed to evaluate the effect of zirconia concentrations in hydroxyapatite on the growth of S. epidermidis. Methods and Materials. The subjects of this study were twenty hydroxyapatite discs, divided into four groups in which one was the control and the other three were the treatment groups. Zirconia powder with the concentrations of 20%, 30%, and 40% was added into the three different treatment groups. Scanning electron microscope analysis was performed according to the hydroxyapatite and hydroxyapatite-zirconia specimens. All discs were immersed into S. epidermidis culture for 24 hours and later on they were soaked into a medium of PBS. The cultured medium was spread on mannitol salt agar. After incubation for 24 hours at 37°C , the number of colonies was measured with colony counter. Data obtained were analyzed using the ANOVA followed by the pairwise comparison. Result. The statistical analysis showed that different concentrations of zirconia powder significantly influenced the number of S. epidermidis colony (P < 0.05) . Conclusion. The addition of zirconia into hydroxyapatite affected the growth of S. epidermidis. Hydroxyapatite with 20% zirconia proved to be an effective concentration to inhibit the growth of S. epidermidis colony.

Tensile Strength Test of Photo Biocomposites for Application in Biomedical Materials

The aim of this research is to perform the tensile strength of photo biocomposite materials. This material consist of hydroxyapatite (HA) as a filler, tri [ethylene glycol] dimethacrilate as a matrix, shellac as a coupling agent and camphorquinone as a photoinitiator. Four ingredients then were used to two mixtures. The first mixture was mixing of TEGDMA and camphorquinone and the second was shellac coated HA. Two of mixtures were mixed to be one solution and was stirred in magnetic stirrer for 1 hour. The solution then was poured into the mold of tensile strength (10 x 10 x 3 mm) and was activated with visible blue light 410 – 500 nm for 40 seconds in order to be polimerization processes. The irradiation process was done with a maximum thickness 1 mm so that the irradiation process was done 3 times (layer by layer processing). The results of tensile strength test showed that the tensile strength would decrease with the addition of HA or would increase by the addition of TEGDMA. The highest tensile strength was obtained at HA/TEGDMA ratio of 20/80%. This material could be used as a bone substitute materials.

Preparation of Porous Hydroxyapatite as Synthetic Scaffold Using Powder Deposition and Sintering and Cytotoxicity Evaluation

This study prepared porous hydroxyapatite (porous HA) as synthetic scaffold and find out chemical properties, porosity, compressive strength and cytotoxicity properties. Porous HA was prepared by powder deposition and sintering from HA-PMMA mixed powder. Porous HA characterizations were conducted by XRD, XRF, SEM-EDX and mercury porosimetry analysis. In vitro cytotoxicity testing of porous HA was conducted by MTT method using vero cells. Porous HA has porosity on the interval 62.79 to 69.67% and compressive strength on the interval 1.53 to 3.71 MPa. Optimal porous HA has porosity is 62.79% with compressive strength is 3.71 MPa. Mercury porosimetry analysis showed that optimal porous HA has interconnective porosity up to 88.25% with pore size on the interval 0.05-355 μm and median pore is 52.64 μm. There was no significantly difference in the death percentage of vero cells caused HA powder and optimal porous HA (p= 0.158) but concentration of optimal porous HA were significantly effect on the percentage of vero cells death (p=0.003).

Study on X-ray diffraction, infra-red spectroscopy, and microstructure of CoHA-Gelatin-PVA biocomposite

The aim of this study was characterization of Biocomposite CoHA-Gelatin-PVA. CoHA (Calcite Omya Hydroxyapatite was obtained from local material by synthesizing local calcite, while gelatin and PVA was commercial from Merck. The composite was prepared by blending powder of CoHA, gelatin, and PVA with weight ratios of 1∶1∶0.15. This blended powder composite was then mixed with distilled water with various solid loading of 5, 15, and 25% w/v. Next, it was cooled at freezer prior freeze drying to build a porous block composite. Characterization was carried out by XRD, FTIR, and SEM. The results showed that the composite block has micropore size &#60;10 and macropore up to 300 µm. Results showed that the HA-gelatin-PVA can be synthesized into porous biocomposites, which has the potential for bone graft. The biocomposite has low cristallyne structure and there is a complex network structure of HA-gelatin-PVA. Biocomposites have a macropore up to 300 µm and micropore up to &#60;10 µm.

Development of seismic risk microzonation map for Semarang due to Semarang fault earthquake scenarios with maximum magnitude 6.9 Mw

Research on seismic microzonation of Semarang is still ongoing. The first seismic microzonation research for this area was performed on 2015. Seismic microzonation map was developed by implementing deterministic 1-D site response analysis at 190 boring locations. Lasem fault was considered to be the main earthquake source which taken into account for seismic microzonation research of Semarang. The second research for developing seismic microzonation map was performed on 2016. Following the research conducted by Team for Updating Seismic Hazard Maps of Indonesia 2016, Rawapening Fault, Ungaran Fault, Weleri Fault, Demak Fault and Semarang Fault are five new shallow crustal fault earthquake sources identified in this research. This paper presents the development of seismic risk microzonation map caused by Semarang fault earthquake scenarios with maximum 6.9 Mw. Deterministic 1-D site response analysis was performed at 288 boring locations for developing seismic risk microzonation map. This research was performed by implementing response spectral matching and site propagation analysis. Due to inadequate data caused by Semarang fault earthquake, response spectral matching was implemented in this research to obtain modified acceleration time histories. All acceleration time histories were developed from five different earthquakes with magnitude 6.05 – 6.9 Mw and maximum epicentre distance 15 Km.

Comparison of Design Method for Making Composite of (PMMA/HA/Sericin)

Biomaterial components (PMMA/HA/Sericin) are composite biomaterial that have complemented each other, which HA is able to improve the mechanical properties, biocompatible and osteoconductivity. PMMA has the ability biocompatible with human tissue and easy manipulated, while sericin can improve cell viability. Analysis of the composite composition is important to do more in depth, but the design method in the analysis of research also has significant impact in generating research output and prediction output. Analysis of the design method to determine the method of designing the optimal research was needed. This research used 3 factors: Poly methyl methacrylate (PMMA) powder (with concentration of 40% to 60%), Hydroxyapatite (HA) powder (with concentration of 10% to 25%) and Sericin (with concentration of 0.16% to 0.32%). This research is done to identify the effect of individual components of the composite and analyze the design method to obtain the best of diametral tensile strength (DTS) with a small error. The result of two methods was found that the 2k factorial design method give higher DTS (PHS401032 = 25.49MPa) than that of Taguchi method (PHS601532 = 24.82MPa). The error of 2k Factorial design method between validation and model prediction is 0.27%, which smaller than Taguchi method (7.45%).

Characteristic and factors of competitive maritime industry clusters in Indonesia

Indonesia is situated in the strategic position between two oceans therefore is identified as a maritime state. The fact opens big opportunity to build a competitive maritime industry. However, potential factors to boost the competitive maritime industry still need to be explored. The objective of this paper is then to determine the main characteristics and potential factors of competitive maritime industry cluster. Qualitative analysis based on literature review has been carried out in two aspects. First, benchmarking analysis conducted to distinguish the most relevant factors of maritime clusters in several countries in Europe (Norway, Spain, South West of England) and Asia (China, South Korea, Malaysia). Seven key dimensions are used for this benchmarking. Secondly, the competitiveness of maritime clusters in Indonesia was diagnosed through a reconceptualization of Porters Diamond model. There were four interlinked of advanced factors in and between companies within clusters, which can be influenced in a proactive way by government.

Mechanical behaviour of biophotocomposite materials: An experimentally validated micromechanics model for tensile strength

The aim of this study is to compare tensile strength by experimentally and micromechanically model mathematic. The tensile strength of materials can be predicted by both tensile strengths of matrix and reinforcement constituent. These biocomposite materials consist of hydroxyapatite (HA) as a filler, Tri[ethylene glycol] dimethacrilate (TEGDMA (Sigma-Aldrich)) monomer as a matrix, glass fibers as a reinforcement, shellac as a coupling agent and camphorquinone (Sigma Aldrich) as a photoinitiator. The elements of a composites constituents have known Rule of Mixtures. The result of this study shows that the tensile strength of a composite can be predicted by calculating the tensile strength of its constituent materials. The values of the prediction tensile strength were between of HA’s tensile strength; glass fibres tensile strength and matrix’s tensile strength. The tensile strength of the materials was significantly influenced by adding the glass fibre.

Composite of [HA/PMMA] for 3D-printer material application

Synthetic hydroxyapatite (HA) and polymethylmethacrylate (PMMA) are among biomaterials that individually has been used in bone defect restoration. Pure HA powder is bioactive and biocompatible material, but it was difficult to be shaped into certain geometry as needed in many cases of restoration. While, PMMA may cause necrosis at the bone-cement interface due to the heat released during polymerization. In shaping technology, a 3D Printer technology is capable to cope a complex geometry and shape, but it is recently only dedicated for the non-medical application. In this study, HA was composed with PMMA to form biocomposite that potentially applicable as a feeder material of the 3D Printer. PMMA powder was blended with various concentration of MMA liquid (40, 45, 50, 55 and 60% v/w) to form PMMA pasta. This pasta was then composed of HA (powder) in various ratios (10, 20 and 30% w/w) and cast into a specimen mold. Tests were performed to observe diametral tensile strength and solidification time relevant ...