Side effects such as abrasion of the dental hard tissue have been frequently observed following the extensive use of mechanical cleansing. As promising antiseptics like chlorhexidine produces extrinsic dental staining on long term usage, there has been increasing interest and research generated towards chemically based stain removing agents. This invitro studyexamined whether some commercial oral hygiene products could inhibit chlorhexidine derived stain independent of any mechanical cleansing action. Perspex blocks were soaked in triplicate in chlorhexidine solution for 2 minutesand stain inhibition by these products was determined by further soaking the blocks in productl water slurries for 2 minutes and finally in tea solution for I hourly periods. The optical density (OD) of each specimen was determined at each hourly interval by spectrophotometry at 395 nm and the mean values obtained. At the end of the study, most of the products inhibited stain compared to water control and there was a variation in the stain inhibitingefficacyof the products. It is thus concluded that oral hygiene products like dentifricesand mouthrinses can inhibit chlorhexidine derived extrinsic dental stain to a variable degree through a chemical action by contained ingredients.
Standard prosthodontic procedures require five visits to construct a set of complete maxillary and mandibular dentures. Various attempts have been made to reduce these procedures to four or three appointments. However, most of these techniques require the use of visible light polymerized resin as the final denture base materials. Visible light-cured resin materials have inferior physical properties and biocompatibility problems as compared with heat cured polymethylmethacrylate. This paper describes a system of complete denture construction which requires three clinical appointments instead of the usual five visits. This system is made possible by using the VLC base/tray material as the preliminary impression material as well as the application of a new biometric wax occlusion rim. It retains the use of polymethylmethacrylate as the denture base material. This system also utilizes all the procedures used in the conventional five appointment system of complete denture construction.
PURPOSE: The impact strength and the flexural properties of denture base materials are of importance in predicting their clinical performance upon sudden loading. This study compares the impact and transverse strengths and the flexural modulus of three denture base polymers.
MATERIALS AND METHODS: The investigation included a relatively new microwave-polymerized polyurethane-based denture material processed by an injection-molding technique, a conventional microwave-polymerized denture material, and a heat-polymerized compression-molded poly(methyl methacrylate) (PMMA) denture material. Impact strength was determined using a Charpy-type impact tester. The transverse strength and the flexural modulus were assessed with a three-point bending test. The results were subjected to statistical analysis using a one-way analysis of variance and the Scheffé test for comparison.
RESULTS: The impact strength of the microwave-polymerized injection-molded polymer was 6.3 kl/m2, while its flexural strength was 66.2 MPa. These values were lower than those shown by the two compression-molded PMMA-based polymers. The differences were statistically significant. The flexural modulus of the new denture material was 2,832 MPa, which was higher than the conventional heat-polymerized polymer but was comparable to the other microwave-polymerized PMMA-based polymer. The difference in the flexural modulus was statistically significant.
CONCLUSION: In terms of the impact and flexural strengths, the new microwave-polymerized, injection-molded, polyurethane-based polymer offered no advantage over the existing heat- and microwave-polymerized PMMA-based denture base polymers. However, it has a rigidity comparable to that of the microwave-polymerized PMMA polymer.
Removal of the whole sternum for malignant tumours results in a large defect, causing severe deformity and possible paradoxical movements of the chest wall. The reconstruction of the resultant large defect of the chest wall is often complex and difficult. Commonly used materials include rib autograft, steel strus acrylic plate and various synthetic meshes such as Goretex or Marlex mesh, with a myocutaneous flap for coverage. A case of a 48-year-old man with sternal chondrosarcoma successfully treated with thoracoplasty using acrylic plate-marlex mesh combination following near total resection of sternum is reported.
This article describes a technique of constructing a set of maxillary and mandibular complete dentures in three visits instead of the usual five clinical appointments. This system of complete-denture construction is made possible because of the combined use of visible light-cured material as an impression tray and record base material, as well as the use of new biometric wax occlusion rims. Unlike some earlier techniques that use light-cured resin composites as the denture base materials, this method retains the use of heat-cured polymethylmethacrylate as the denture base material.
Hybrid organic-inorganic membranes were fabricated using sol-gel technique using PMMA and TEOS with 80/20 (w/w) ratio at various solvents. The thin membrane films were then characterized using DSC and TGA. From DSC analysis, the Tg value of the PMMA moieties in hybrids membranes was in the order H-15-Toluene < Pure PMMA < H-15-THF < H-15-DMF. Furthermore, from TGA analysis it was found that the hybrid membranes have higher thermal stability compared to pure PMMA, and the type of solvents used play an important role in their degradation behavior.
The aim of this study was to evaluate the mechanical properties and glass transition temperature (Tg) of a denture base material prepared from high molecular weight poly methyl methacrylate (PMMA) and alumina (Al2O3). The glass transition temperature was studied by using differential scanning calorimetry (DSC). The effect of powder-to-liquid ratio was investigated. The result showed that the tensile properties and the Tg were slightly effected by the powder-to-liquid ratio. The ratio of 2.2:1 by weight of powder to liquid was found to be the best ratio for mixing the material to give the best result in this formulation.
The aim of this study was to evaluate the tensile properties and water absorption of denture base material prepared from high molecular weight poly methyl methacrylate (PMMA) and alumina (Al2O3) as particulate filler. Specimens for mechanical testing were prepared by adding composite powder to the monomer followed by hand mixing as in dental laboratory procedure. The tensile strength of the prepared denture base material was slightly higher than commercial denture base material, while the water absorption was almost the same for all formulation of denture base materials.
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.
We conducted a prospective study in order to audit our experience of repairing cranial defects using Methyl methacrylate. This included a total of 49 patients undergoing cranioplasty using methyl methacrylate, of which 45 were males and 4 females. The age of patients at the time of surgery ranged from 16 to 40 years old, with an average of 24 years. Malays were the majority (67%), followed by Chinese (23%) and Indian (10%). Cranial defects were mainly caused by motor vehicle accident (94%), while gunshot wounds, industrial accidents and tumours, each contribute 2%. Bone flaps were commonly removed during previous surgery related to traumatic subdural haemorrhage (33%), contusion (21%) and intracerebral haemorrhage (14%). The size of cranial defects ranged from 28 cm2 to 440 cm2, with an average of 201 cm2. Most had right sided (55%) and lateral defects [temporoparietal (52%) followed by temporal (16%), frontal (16%), frontotemporal (14%) and occipital (2%)]. Duration of surgery ranged from 70 to 275 minutes, with an average of 135 minutes. Nine of 12 patients (75%) with neurological disability had some improvement while 85% of symptomatic patients had symptoms improvement after cranioplasty. The infection rate in this series was 4%.
Nylon denture base material could be a useful alternative to poly (methyl methacrylate) (PMMA) in special circumstances such as patient allergy to the monomer. The aim of this study was to evaluate the flexural properties of a nylon denture base material (Lucitone FRS), a conventional compression-moulded heat-polymerized (Meliodent), a compression-moulded microwave-polymerized (Acron MC) and an injection-moulded microwave-polymerized (Lucitone 199) PMMA polymers. The effect of aldehyde-free, oxygen releasing disinfectant solution (Perform) on these properties was also investigated. The flexural modulus and the flexural strength were assessed with a three-point bending test. Specimens were stored in water at a temperature of 37 degrees C for 30 days. For each material, half of the prepared specimens were randomly selected and immersed in the disinfectant 24 h prior to testing. Results were compared statistically at a confidence level of 95%. The result showed that in both the control and disinfected groups, the flexural modulus of nylon was significantly lower than the three PMMA polymers. The flexural strength of nylon was significantly lower than those of Meliodent and Acron MC but was comparable with Lucitone 199. A 24-h immersion in the disinfecting solution increased the rigidity of nylon denture base material.
A single-step fabrication of a glucose biosensor with simultaneous immobilization of both ferrocene mediator and glucose oxidase in a photocurable methacrylic film consisting of poly(methyl methacrylate-co-2-hydroxylethyl methacrylate) was reported. The entrapped ferrocene showed reversible redox behaviour in the photocured film and no significant leaching of both entrapped ferrocene and enzyme glucose oxidase was observed because of the low water absorption properties of the co-polymer films. From electrochemical studies, ferrocene entrapped in the co-polymer film demonstrated slow diffusion properties. A linear glucose response range of 2-11 mM was obtained at low applied potential of +0.25 V. The glucose biosensor fabricated by this photocuring method yielded sensor reproducibility and repeatability with relative standard deviation of <10% and long-term stability of up to 14 days. The main advantage of the use of photocurable procedure is that biosensor membrane fabrication can be performed in a single step without any lengthy chemical immobilization of enzyme.
Chemical modification of natural rubber (NR) has frequently been attempted to improve the performance in specific application. 30% poly(methyl metacrylate) (PMMA) grafted into NR (MG30) has been explored as a potential candidate for polymer electrolytes. The complexation effect of salt and plasticizer in polymer host electrolytes had been investigated using FTIR. The carbonyl stretch of MG30 locates at 1729 cm-1, with the addition of lithium trimethanesulfonate (LiCF3SO3) salt, new band evolves at lower frequency region at 1643-1645 cm-1. The nondegenerate vibrational mode of nus(SO3) of salted electrolytes appearing at 1031-1034 cm-1 comes from 'free' trimethanesulfonate anions and the 1040-1046 cm-1 absorption from the monodentate ion paired with triflates. These indicate MG30-salt interaction. When MG30 and ethylene carbonate (EC) formed film, the CH3 asymmetric bend of MG30 appearing at 1447cm-1 is shifted to 1449 cm-1 in the EC-polymer complex. The CO stretching at 1729 cm-1 also shifted to 1728 cm-1. Hence, the EC-MG30 system is complexed to each other. EC-LiCF3SO3 interactions are indicated by the shifting of CO bending band of EC from 718 cm-1 being shifted to 720 cm-1 in the complex. In Li+-EC interaction where the ring breathing region at 897 cm-1 in EC has shifted to 899 cm-1 in EC-salt spectrum. The band appearing at 1643-1645 cm-1 due to the coordination of Li+
We report a case of an 11-year-old boy with osteosarcoma of the proximal humerus treated with wide excision and reconstruction with a cement spacer-prosthesis. After seven years of follow-up, the patient is now almost a young adult. We present his current physical and functional status, which seems to defray the initial doubts regarding long-term problems when we chose this method of reconstruction.
The polymer electrolytes composing of the blend of polyvinyl chloride-polymethyl methacrylate (PVC/PMMA) with lithium triflate (LiCF3SO3) as salt, ethylene carbonate (EC) and dibutyl phthalate (DBP) as plasticizers and silica (SiO2) as the composite filler were prepared. FTIR studies confirm the complexation between PVC/PMMA blends. The CCl stretching mode at 834 cm-1 for pure PVC is shifted to 847 cm-1 in PVC-PMMA-LiCF3SO3 system. This suggests that there is interaction between Cl in PVC with Li+ ion from LiCF3SO3. The band due to OCH3 at 1150 cm-1 for PVC-PMMA blend is shifted to 1168 cm-1 in PVC-PMMA-LiCF3SO3 system. This shift is expected to be due to the interaction between Li+ ion and the oxygen atom in PMMA. The symmetric vibration band and the asymmetric vibration band of LiCF3SO3 at 1033 and 1256 cm-1 shifted to 1075 and 1286 cm-1 in the DBP-EC plasticized PVC-PMMA-LiCF3SO3 complexes. The interaction between Li+ ions and SiO2 will lead to an increase in the number of free plasticizers (which does not interact with Li+ ions). When the silica content increases from 2% to 5%, the intensity of the peak at 896 cm-1 (due to the ring breathing vibration of free EC) increases in PVC-PMMA-LiCF3SO3-DBP-EC system.
The impact strength of a newly developed experimental polyurethane-based polymer which is derived from palm oil (Experimental PU) was compared with denture polymers; heat-cured and self cured polymethyl methacrylate (PMMA) and ® Eclipse , light-activated urethane dimethacrylate prosthetic resin system. Ten specimens were ® prepared using heat-cured PMMA (Meliodent Heat Cure, Heraeus Kulzer, Germany), self cured PMMA ® (Meliodent Rapid Repair, Heraeus Kulzer, ® Germany), Eclipse baseplate resin (Dentsply, USA) and Experimental PU material. Specimens were prepared following manu- facturer’s instructions except for the Experimental PU material where it was prepared in bulk and sectioned to the desired dimension, 64 x 6 x 4 mm. A ‘V’ notch of approximately 0.8mm in depth was machine cut across the 6mm width. Prior to the Charpy type impact test, specimens were soaked in a water bath for 50 hours at 37ºC. ® Eclipse baseplate resin showed the highest 2 impact strength (2.73 kJ/m ±0.54) followed by ® 2 Meliodent Rapid Repair (2.50kJ/m ±0.65), ® 2 Meliodent Heat Cure (1.96kJ/m ±0.42) and 2 Experimental PU (1.04kJ/m ±0.29). One-way ANOVA showed significant interaction between materials (p
Sodium silicate was used to synthesize silica fine particles at room temperature using non-ionic surfactant of triethanolamine (TEA), dissolution salt and precipitating agent. The experiments were conducted by different composition of precursor material, nonionic surfactant and dissolution salt concentrations through the sol-gel process. Various particle sizes in the range 100-300nm were synthesized. The particle size of silica powders were analyzed via Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray Analysis (EDAX), X-Ray Fluorescence (XRF), and Fourier Transformation Infrared (FTIR). The result has demonstrated that the particle size can be controlled by changing the ratio of non-ionic surfactant and dissolution salt or the sodium silicate concentration.
Many attempts have been focused in the past on preparing of synthetic E-tricalcium (E-TCP), which being employed as bone substitute due to its biocompatibility and resorbability. Low temperature synthesize such as sol-gel method become popular due to the high product purity and homogenous composition. Sol-gel method is less economical towards commercialization because the cost of raw materials and the yield of the product that can be achieved. This paper describes the synthesis of ETCP via mixing of CaCO3 and H3PO4 followed by calcinations process at 750qC – 1050qC. X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), fourier transformation infra-red (FTIR) were used for characterization and evaluation of the phase composition, morphology, particle size and thermal behavior of the product. E-TCP phase start to occur after calcinations at 750qC.
An artificial neural network (ANN) was applied for the determination of V(V) based on immobilized fatty hydroxamic acid (FHA) in poly(methyl methacrylate) (PMMA). Spectra obtained from the V(V)-FHA complex at single wavelengths was used as the input data for the ANN. The V(V)-FHA complex shows a limited linear dynamic range of V(V) concentration of 10 - 100 mg/ L. After training with ANN, the linear dynamic range was extended with low calibration error. A three layer feed forward neural network using backpropagation (BP) algorithm was employed in this study. The input layer consisted of single neurons, 30 neurons in hidden a layer and one output neuron was found appropriate for the multivariate calibration used. The network were trained up to 10000 epochs with 0.003 % learning rate. This reagent also provided a good analytical pedormance with reproducibility characters of the method yielding relative standard deviation (RSD) of 9.29% and 7.09% for V(V) at concentrations of 50 mg/ L and 200 mg/ L, respectively. The limit of detection of the method was 8.4 mg/ L.
Barium strontium titanate (Ba0.7Sr0.3TiO3) powder was processed at temperature 80 o C by reacting titania sol in aqueous solutions that contained BaCl2, SrCl2 and NaOH at atmospheric pressure.
The structural characteristic of the powder and sintered pellet were studied using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) whereas the electrical characteristic was determined via Impedance Spectroscopy (IS) and LCR meter. The synthesized powder was found to have a tetragonal phase after heating at 1300 o C. XRD pattern also showed the presence of secondary phase BaTi2O5 (BT2). The SEM results shows the fine grain size was in the range of 0.2 Pm to 0.4 Pm whereas the large ones are approximately 0.8 Pm to 1.2 Pm The ac response of sample sintered at 1300 o C indicated that three electrically different regions. Element 1 can be assigned as a ferroelectric grain boundary region and it is actually BT2, element 2 as a ferroelectric bulk region and the third element is a conductive core which has a low resistance (200 :) and capacitance value.