Zulia Hasratiningsih

Basic Properties of PMMA Reinforced Using Ceramics Particles of ZrO2-Al2O3-SiO2 Coated with Two Types of Coupling Agents

In this study, novel composites materials composed of polymethyl methacrylate (PMMA) reinforced ZrO2-Al2O3-SiO2 filler system were developed. Zirconia-alumina-silica filler system were synthesized through sol-gel technique. Chitosan and trimethoxypropilsilane (TMPS) were used to modify the composites system. The resulting composites material were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and hardness test. SEM images displayed the composites particles in nanometer size with minor agglomeration. The XRD results revealed the presence of cubic and tetragonal phase of zirconia and also monoclinic silica phases in the composites system. These crystallographic characteristic could affect the mechanical properties of the composites. The hardness value for un-modified composites was 15.27 ± 0.25 VHN and for TMPS 19.43 ± 1.89 VHN and chitosan modification 18.75 ± 2.05 VHN, respectively. Therefore, these novel composites materials composed of PMMA reinforced filler system of zirconia-alumina-silica would provide the potential to apply in dental technology.

Hardness Evaluation of Dental Composite with Ceramic Fillers

In this study, new dental composites materials were developed. The two composites systems composed of zirconia (ZrO2), alumina (Al2O3) and silica (SiO2) (composites A) and zirconia (ZrO2), calcium (CaO), and silica (SiO2) (composites B) were synthesized through sol-gel method. These two systems were combined with urethane dimethacrylate and tetraethylene glycol dimethacrylate with 1% chitosan as coupling agent to build up the dental composites material. The resulting composites were subject to evaluation by microvickers hardness test and X-ray diffraction. The microvickers hardness test revealed that the hardness value for composites A and B were 24.48 and 21.9 VHN, respectively. Furthermore, the data were submitted to t-test (α=0,01) and it showed t count of both samples was 0,871 which means between the -t1-½α< t <t1-½α thus showing statistically the same average hardness value of both samples. Eventually, the new dental composites could be anticipated to apply in dental composites filler. The hardness results support the XRD result revealed that tetragonal crystal phase will help the transformation toughening mechanism and cubical crystal phase of zirconium dioxide. Both of the crystal phases were formed to stabilize the zirconia.

Surface Characterization of Dental Porcelain Made from Sumatera Natural Sand

This research reported hardness and porosity morphology results on five different sintering temperatures as surface characterization of dental porcelain made from Sumateran natural sand mixture composition to prevent excessive wear. Porosity morphology was characterized with JEOL Scanning Electron Microscope (SEM), while the average hardness of each 5 different indented areas was performed with 1000 gr load for 15 seconds using Zwick Roell Vickers Hardness Tester. The result of this study shows that the higher sintering temperature correlates to higher hardness number. SEM analysis indicate less porosity appear in the samples sintered in higher temperature. By modifying the mixture, this study has significantly lowered the hardness number results compared to our previous research samples yielded 936,06 VHN. It can be concluded that positive correlation between higher temperature and hardness emerged from the surface characterization results of the dental porcelain made from Sumatera natural sand. In contrasts the porosity appear to be less developed in higher temperature. However, cracks and pores followed the indentation as in common ceramic products. Further improvement is needed with finding the optimum temperature of desired hardness number and predictable porosity, which resemble tooth enamel.

Sintering Temperature Effect on Hardness of Self-Synthetisized Porcelain Made from Natural Sumatran Sand without Kaolin

Dental porcelain is one of the indirect restoration material with excellent aesthetic properties,on the other hand porcelain hardness frequently causing excessive wear of antagonist teeth. This study aiming to evaluate the effect of sintering temperature on the self-synthesized porcelain hardness. In this experiment, 25 porcelain samples were synthesized using Sumatran sand from Pangaribuan and Belitung regions, with the composition of 65 wt% Pangaribuan feldspar, 25 wt% Belitung silica and 10 wt% potassium salt. The samples were sintered in five different temperatures, which were 1110°C (A), 1120°C (B), 1130°C (C), 1140°C (D), and 1150°C (E). These samples were then invested on 5cm diameter resin each. The hardness was tested using Zwick Roell ZHμ Micro Vickers with 900 gram load for 15 seconds in 5 different indented areas for each sample. The result shows average hardness of 435.8 VHN (A), 461.0 VHN (B), 472.0 VHN (C), 487.6 VHN (D), and 528.7 VHN (E), which were increasing as the sintering temperature increased. Statistic result shows that sintering temperature significantly affected the hardness value of the porcelain (p value < 0.05). In conclusion sintering temperature affects the hardness of self-synthesized porcelain made from Sumatran natural sand without kaolin, although the average hardness of self-synthesized porcelain is still higher than average hardness of teeth enamel.

Preparation and characterization of zirconia-alumina system via solution and solid phase mixing method

Popularity of zirconia gained up after discovering the unique properties of zirconia called transformation toughening. Alumina is one of material used to stabilize tetragonal crystalline of zirconia in room temperature. In this study, zirconia-alumina systems have been developed in two ways mixing methods through sol-gel technique. First method was done by mixing both precursors of zirconia and alumina in the hydrolysis stage, while the second method was in the drying stage of the sol-gel technique. Phase of material was solution at hydrolisis stage and solid at drying stage. Zirconia-alumina system having the ratio 90:10 by weight (ZrO2:Al2O3). The mixture were calcined at temperature 900 °C for 2 hours. Samples were than characterized by X-Ray Diffraction to assign tetragonal crystallline of zirconia. Scanning Electron Microscope and Brunauer-Emmett-Teller characterization were conducted to observe morphology, particle size as well as surface area of samples. XRD characterization of solution phase mixin...

Mechanical Strength Properties of Injectable Carbonate Apatite Cement with Various Concentration of Sodium Carboxymethyl Cellulose

Mechanical strength is one of the key factors for clinical application of injectable carbonate apatite (CO3Ap) cement. Incorporation of polymeric additives into the mixing liquid of injectable bone cement has been known to improve cement injectability. The aim of this study is to determine whether incorporation of sodium carboxymethyl cellulose (Na CMC) into the mixing liquid would affect the diametral tensile strength (DTS) of injectable CO3Ap cement. In the present study, Na CMC, a polymeric additive and a cellulose derivative, was used to promote the injectability of CO3Ap cement. Three groups of CO3Ap cement samples consist of CaCO3 and CaHPO4 powder in each group were mixed with 0.5 %, 1%, and 2% Na CMC solution incorporated to 0.2 mol/L Na2HPO4 solution. As a control, powder mixed with 0.2 mol/L Na2HPO4 solution was used. Samples were kept in an incubator (37°C, 100% relative humidity, 24 hours). The mechanical strength properties were evaluated by diametral tensile strength (DTS). The average DTS of samples containing 0.5%, 1%, and 2% Na CMC were 3.19 MPa, 3.57 MPa, and 3.06 MPa, respectively. While the average DTS of the control group was 3.29 MPa. The groups containing Na CMC in all concentrations showed no statistical difference (p>0.05) on DTS compared to the control group. The injectability improved as the concentration of Na CMC increased. In conclusion, revealed that Na CMC does not affect the mechanical strength of CO3Ap cement. Therefore, it may be considered as an effective material to promote cement injectability. Further study of additives that can be used to promote the injectability of CO3Ap cement and enhance the mechanical strength awaits based on this initial finding.

Synthesis and Characterization of MgPSZ-PMMA Composite by Sol-Gel Modification and Direct Foaming Technique Using Egg Whites

This study prepared Magnesium-Partially Stabilized Zirconia (Mg-PSZ) filler synthesis and direct foaming technique using egg whites, and impregnated by PMMA. The results were evaluated systematically by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). XRD results denote that the powder sample of MgPSZ was successfully formed with various crystal size of tetragonal and monoclinic phase. SEM and TEM observations revealed that nanoparticles MgPSZ were in spherical and long rounded shapes. Furthermore, SEM observation revealed that the direct foaming method were also successful in the formation of porous structures which favourable for impregnation process by PMMA. The use of egg whites as a polymer precursor in both methods demonstrates that porous specimens contained nanosized, predominantly tetragonal, Mg-PSZ powders were successfully synthesized. This shall yield an interesting prospect towards cheap, reliable, and biocompatible product to resemble the modulus elasticity of dentin.