Widowati Siswomihardjo

Biofilm Formation on Dental Restorative and Implant Materials

Biomaterials for the restoration of oral function are prone to biofilm formation, affecting oral health. Oral bacteria adhere to hydrophobic and hydrophilic surfaces, but due to fluctuating shear, little biofilm accumulates on hydrophobic surfaces in vivo. More biofilm accumulates on rough than on smooth surfaces. Oral biofilms mostly consist of multiple bacterial strains, but Candida species are found on acrylic dentures. Biofilms on gold and amalgam in vivo are thick and fully covering, but barely viable. Biofilms on ceramics are thin and highly viable. Biofilms on composites and glass-ionomer cements cause surface deterioration, which enhances biofilm formation again. Residual monomer release from composites influences biofilm growth in vitro, but effects in vivo are less pronounced, probably due to the large volume of saliva into which compounds are released and its continuous refreshment. Similarly, conflicting results have been reported on effects of fluoride release from glass-ionomer cements. Finally, biomaterial-associated infection of implants and devices elsewhere in the body is compared with oral biofilm formation. Biomaterial modifications to discourage biofilm formation on implants and devices are critically discussed for possible applications in dentistry. It is concluded that, for dental applications, antimicrobial coatings killing bacteria upon contact are more promising than antimicrobial-releasing coatings.

Immediate repair bond strengths of microhybrid, nanohybrid and nanofilled composites after different surface treatments

OBJECTIVES To evaluate immediate repair bond strengths and failure types of resin composites with and without surface conditioning and characterize the interacting composite surfaces by their surface composition and roughness. METHODS Microhybrid, nanohybrid and nanofilled resin composites were photo-polymerized and assigned to four groups: (1) no conditioning (Control), (2) no conditioning, polymerized against a Mylar strip (Control, with strip), (3) intermediate adhesive resin (IAR) application, and (4) chair-side silica coating, silanization and intermediate resin application (SC). Resin composites, similar as their substrates, were adhered onto the substrates. Shear force was applied to the interface in a universal testing machine and failure types were evaluated under light microscopy. Surface characterization was done by contact angle measurements, X-ray photoelectron spectroscopy, scanning electron and atomic force microscopy. RESULTS Significant effects of the resin composite type and surface conditioning were observed. Conditioning the composites with their IARs does not result in significant improvements in bond strength compared to the control with strip (bond strengths between 14.5 and 20.0 MPa). SC increased the bond strength in all composites except TE by an average 8.9 MPa, while in all composites the surface roughness increased from 7 to 384 microm. Failure types in this group were exclusively cohesive. Physico-chemical modelling of the composite surfaces showed that the surfaces were dominated by the resin matrix, with a major increase in silica-coverage after SC for all composites. CONCLUSION Intermediate adhesive resin conditioning did not improve the composite-to-composite immediate repair strength. Silica coating and silanization followed by its corresponding IAR, strongly increased repair bond strengths and provided exclusively cohesive failures in the substrate in all composites.

Effect of Biofilm on the Repair Bond Strengths of Composites

Composite restorations degrade during wear, but it is unknown how wear affects the composite surface and influences composite-to-composite bonding in minimally invasive repair. Here, it is hypothesized that in vitro exposure of composites to oral biofilm yields clinically relevant degradation of composite surfaces, and its influence on composite-to-composite bonding is determined. Biofilms on composite surfaces in vitro increased their roughness and decreased filler particle exposure, except for a microhybrid composite, similar to effects of clinical wear in palatal appliances. Failure shear stresses after intermediate-adhesive-resin application were significantly lower after aging by in vitro exposure to biofilms, while silica-coating maintained the same failure stress levels as in non-aged composites. Failure modes were predominantly cohesive after silica-coating, while intermediate-adhesive-resin application yielded more adhesive failure. It is concluded that in vitro exposure to oral biofilm is a clinically relevant aging condition, and that silica-coating is to be preferred for the repair of aged composites.

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.

Evaluation of various alloys for stent on platelet aggregation activity

Nowadays coronary artheroslerotic disease becomes a primary health problem due to its high morbidity and mortality rate. Such disease is related to the poor coronary blood flow quality. Coronary stent implantation is widely accepted to overcome the problem. There are various alloys available for stent commercially by different prices. This study was aimed to evaluate the various alloys for stent on platelet aggregation activity. The materials used under reseach were stainless-steel of SS 316L (Otocompo, Sweden) and cobalt-chromium of CoCr L605 (Remanium Star, Germany). Twenty eights alloys (14 SS 316L and 14 CoCr L605) were shaped as discs with 10 mm diameter and 2 mm thickness respectively. Venous blood was drawn from medial cubiti vein from 14 subjects of healthy people with neither established atherosclerotic disease nor risk factors. The drawn blood from each subject further be divided into three parts: one part was left without any induction (control), the other two parts were contacted to SS 316L and CoCr L605 respectively. Platelet aggregation activity in all of the samples were then calculated and analyzed by Anova. The result showed the average of platelet aggregation activity in percentage (%) were 89.96±17.93 (control), 80.16±22.04 (CoCr L605), and 80.91±20.68 (SS 316L). The Anova showed p>0.05. In conclusion, stainless-steel of SS 316L and cobalt-chromium of CoCr L605 did not affect platelet aggregation activity on healthy subject; therefore, both of the alloys were potential to be used as material choices for stent devices. Further research is needed to evaluate the effect of both alloys on atherosclerotic patients.

The effect of annealing temperature on the physical and mechanical properties of stainless steel 316L for stent application

A comparative study on mechanical properties and microstructure of 316L austenitic stainless steel annealed in different temperatures were presented. The objective of this study was to get the optimum annealing temperature for austenitic stainless steel 316L for stent application in coronary heart disease. Five groups of specimens (ASTM E8-2004) were annealed in the electric furnace (Ellite Thermal System Ltd., UK) at temperature 1000°C, 1050°C, 1100°C, 1150°C, and 1200°C using a heating rate of 5°C/min with 30 minutes holding time. The heat-treated austenitic stainless steel 316L was cooled to room temperature by slow furnace cooling then collected and characterized. The microstructure evolution of every sample was observed using SEM. The hardness of the sample was measured using Vickers micro hardness test. The universal testing machine was used to measure the tensile strength and elongation of every sample. The results shown that the biggest elongation of austenitic stainless steel 316L is obtained when the material is annealed at temperature between 1050 to 1150°C.

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).

The effect of sericin application over hydroxyapatite surface on osteoblast cells proliferation

Hydroxyapatite (HA) has been used clinically to treat bone defect. Modification of HA surface with respect to bone integration has been developed using treatments which have the potential to improve cells proliferation. Bombyx moris sericin, a polymer protein that has polar side groups, have been known to accelerate cells attachment and proliferation. The aim of this study was to investigate the effect of sericin application over HA surface on osteoblast cells proliferation. HA discs (10 mm in diameter, 3 mm thick) were sintered. Three concentration of sericin (0.01, 0.5, and 0.1%) were applied on HA surface. Water contact angle was measured to evaluate the hydrophilicity of the disc surface. The discs were then seeded with MC3T3E1 osteoblast cells for proliferation test. The data were analyzed by Anova and LSD. Contact angle measurement showed significant increases of the hydrophilicity on sericin-modified HA surface. The amount of cells proliferation on HA discs (1.40±0.26) was significantly difference (p&#60;0.05) with HA+sericin 0.01% (2.23±0.20), HA+sericin 0.5% (2.33±0.24), HA+sericin 0.1% (2.37±0.20). Variation of sericin concentrations applied over HA did not influence any significant difference on cells proliferation (p>0.05). The conclusion was sericin application over HA surface increased the amount of osteoblast cells proliferation. Concentration of sericin application over HA (0.01, 0.05, 0.1%) did not influence cells proliferation.