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PubMedDate not supplied

Effectiveness of microwave sterilization on three hard chairside reline resins.

PURPOSE: The aim of this study was to evaluate the effectiveness of microwave irradiation sterilization on hard chairside reline resins. MATERIALS AND METHODS: Specimens of three reline resins (Kooliner, Tokuso Rebase, and Ufi Gel Hard) were fabricated and subjected to ethylene oxide sterilization. The specimens were then individually inoculated (10(7) cfu/mL) with Tryptic Soy Broth media containing one of the tested microorganisms (C albicans, S aureus, B subtilis, and P aeruginosa). After 48 hours at 37 degrees C, the samples were vortexed for 1 minute and allowed to stand for 9 minutes, followed by a short vortex to resuspend any organisms present. After inoculation, 40 specimens of each material were immersed in 200 mL of water and subjected to microwave irradiation at 650 W for 6 minutes. Forty non-irradiated specimens were used as positive controls. Replicate specimens (25 microL) of suspension were plated at dilutions of 10(-3) to 10(-6) on plates of selective media appropriate for each organism. All plates were incubated at 37 degrees C for 48 hours. After incubation, colonies were counted, and the data were statistically analyzed by the Kruskal-Wallis test. Twelve specimens of each material were prepared for SEM. RESULTS: All immersed specimens showed consistent sterilization of all the individual organisms after microwave irradiation. SEM examination indicated an alteration in cell morphology after microwave irradiation. CONCLUSION: Microwave sterilization for 6 minutes at 650 W proved to be effective for the sterilization of hard chairside reline resins.

Acrylic Resins↗
PubMed2004

In vitro and in vivo induction of human LoVo cells into apoptotic process by non-invasive microwave treatment: a potentially novel approach for physical therapy of human colorectal cancer.

The human LoVo and WI-38 cells were exposed to high power non-invasive microwaves. The apoptotic effect of the microwaves on the cells was examined with TUNEL, DNA fragmentation and flow cytometry. The human colon cancer LoVo cells showed pathological change of apoptosis but the normal human WI-38 cells showed no detectable apoptotic response. Exposure of the mice bearing tumor tissue to microwave resulted in a significant regression of the tumor tissue in the animal models. We demonstrate that the LoVo cells can be induced into apoptosis by microwave treatment both in in vitro and in vivo. The data described in this communication implies the possibility that microwave therapy may become a novel approach in human colorectal cancer treatment.

Animals↗
PubMed2005

[Study on water extraction process of Herba epimedii with microwave technology].

OBJECTIVE: To study, the high polar media-water extraction process of Herba epimedii with the microwave technology. METHOD: The single parameters of extraction process was investigated with dry extract yield and extraction efficiency of icariin as content index. RESULT: Through studying the single parameter, the optimal conditions are as follows: 70% ethanol as wetting solvent, volume of solvent to weight of material equal to 6:1 in wetting, 30 min wetting time, 2.5 min microwave irradiation time, volume of solvent to weight of material equal to 50:1 in extraction process, 10 min microwave-assisted extraction time. CONCLUSION: Compared with conventional methods, microwave-assisted extraction (MAE) after Microwave Pretreament (MP) of raw material was higher extraction efficiency and time-saving.

Drugs, Chinese Herbal↗
PubMed2005

[Effects of microwave power on temperature change in dental pulpal chamber in vitro].

OBJECTIVE: To explore the effects of microwave powers on temperature changes of dental pulpal chamber in vitro. METHODS: 96 isolated teeth were prepared in three degrees of dental occlusal wear according to Smith BG's report. Temperature change values in dental pulpal chamber were recorded by thermometer (DM 6801A) while the different affect time and microwave powers acted directly and with 75% sodium fluoride glycerine paste on face of isolated teeth separately in room temperature. RESULTS: The degree of temperature in dental pulpal chamber was going up follow the raising microwave power and prolonging time. The temperature in dental pulpal chamber with microwave acting sodium fluoride on dental occlusal was higher than acting directly dental occlusal. CONCLUSION: The microwave power, time and degree of dental occlusal wear are very important factors on temperature change in dental pulpal chamber in our study.

Dental Pulp↗
PubMed1992

The effect of in-line microwave energy on blood: a potential modality for blood warming.

The treatment of hypothermia associated with hemorrhage, exposure, or intraoperative intervention continues to represent a challenge for trauma care teams. An innovative technique for combining microwave heating with continuous temperature monitoring into a feedback-controlled system for blood warming has been developed. The effect of microwave warming on the structure and function of blood was compared with that in nonheated controls. Erythrocyte structural integrity (hemolysis) was evaluated by comparing levels of lactate dehydrogenase (LDH), potassium (K+), and plasma hemoglobin (PHGB), and hematocrit (HCT) in heated and nonheated (control) samples of banked red blood cells. Hemoglobin function was evaluated in fresh blood by comparing the P50 and hemoglobin electrophoresis of experimental and control samples. Prewarming temperatures were 3 degrees or 23 degrees C; temperatures after warming were 35 degrees, 37 degrees, or 39 degrees C. The results reflect the percentage of changes for 84 heated and 24 unheated blood samples. There were no statistical differences in any of the biochemical variables measured. The P50 for three heated and three unheated samples was 30.7 +/- 1.2 and 30.5 +/- 0.9 mm Hg (p greater than 0.05). There were no changes in the hemoglobin electrophoretic patterns in experimental or control samples. This system is designed to deliver microwave energy in a uniform and controlled manner, overcoming the limitations of conventional microwave ovens that in the past caused local overheating and subsequent hemolysis when used for blood warming. The structural and functional integrity of erythrocytes after microwave warming indicate the safety and effectiveness of this technique.

Blood↗
PubMed1992

The microwave oven in temporal bone research.

The microwave oven has recently been introduced in morphological research. It can be used for virtually all procedures in histological processing; fixation, dehydration, embedding, staining, immunotechniques, and the techniques used for electron microscopy. Here we report that the microwave oven histoprocedures also have several advantages in temporal bone research on animals. The microwave oven has been tested for (i) fixation, (ii) decalcification, (ii) staining of semithin plastic sections. The microwave oven procedures are time-saving and results in an excellent preservation of the tissues. The microwave histoprocessing should also be applicable to temporal bone research in human.

Animals↗
PubMedDate not supplied

[The impact of electromagnetic radiation at microwave frequency (9.8 HhZ)on the embryonic and postembryonic development of the tick Hyalomma asiaticum (Acarina, Ixodidae)].

Low-power (20 microW/cm2) microwave-modulated radiation at a carrier frequency of 9.8 Hhz is shown to affect the course and specific features of ontogenesis of the ick H. asiaticum. The actin of microwave radiation on the development of H. asiaticum substantially depends on the frequency of microwave modulation of a signal and on the temperatures of an experiment. When the temperature is 22 degrees C, there is a significant suppression of development of fed larvae and nymphs after exposure to microwave radiation at modulated signal frequencies of 3 and 5 Hz/ The whole range of the tested modulation frequencies was 2 to 16 Hz. The hungry species of all developmental phases in H. asiaticum were virtually unresponsive to exposures. At 14 degrees C (a perithreshold temperature of H. asiaticum development), the action of microwave radiation changed from inhibitory to stimulating. At modulation frequencies of 3, 5 and 7 Hz, the proportion of hatching larvae was 42.5, 67.5 and 80.0%, respectively, and that of controls was 2.5%. Whether the size of a H.asiaticum population can be controlled by a radar that provokes the development of ticks before winter by its radiation is discussed.

Animals↗
PubMed2006

[Microwave sintering of nanometer powder of alumina and zirconia-based dental ceramics].

OBJECTIVE: The objective of the present study was to investigate the feasibility and reliability of sintering alumina and zirconia-based all-ceramic materials through a recently introduced microwave heating technique. The variation of crystal phases, the growth of grain sizes and microstructural features of these materials were evaluated after sintering. METHODS: Four different groups of powder (l00%Al2O3, 60%Al2O3+40%ZrO2, 40% Al2O3+60%ZrO2, 100% ZrO2) were respectively press-compacted to fabricate green disk samples, 5 specimen of each group were prepared. All the samples were surrounded by refractory materials for heat containment and processed at 1 600 degrees C in a domestic microwave oven (850 W, 2 450 MHz), 1 600 degrees C/5 min for heating rate, 10 min for holding time. After sintering, the phase composition and average grain size of these ceramics were examined using X-ray diffraction (XRD). Their microstructure characteristics were studied by scanning electron microscopy (SEM). RESULTS: All the specimens were successfully sintered with the application of microwave heating system in combination with a suitable thermal insulator. No phase change was found in alumina while monoclinic-zirconia was found to be transformed to tetragonal-zirconia. A little grain size growth of Al2O3 and ZrO2 has been observed with Al2O3 24.1 nm/before and 51.8 nm/after; ZrO2 25.3 nm/before and 29.7 nm/after. The SEM photos indicated that the microwave-sintered Al2O3-ZrO2 ceramics had a uniform crystal distribution and their crystal sizes could be maintained within the range of nanometers. CONCLUSION: It is expected that in the near future microwave heating system could be a promising substitute for conventional processing methods due to its unparalled advantages, including more rapid heating rate, shortened sintering time, superfine grain size, improved microstructure and much less expensive equipment.

Aluminum Oxide↗
PubMed2006

[Microwave coagulation at different temperatures for hepatocellular carcinoma management: efficacy evaluation by enzyme histochemical staining].

OBJECTIVE: To compare the application of HE and enzyme histochemical staining in assessing the viability of hepatocellular carcinoma (HCC) cells coagulated by microwave ablation at different temperatures. METHODS: Two groups of mice (n=6) with transplanted homogenic HCC were treated by microwave ablation at 60 degrees C and 50 degrees C for 3 min, respectively. Before and after microwave ablation, paraffin sections and frozen sections of the tumors were prepared for routine HE staining and enzyme histochemical staining with nicotinamide adenine dinucleotide diaphorase (NADH-diaphorase), respectively, and observed under microscope. RESULTS: Shortly after microwave ablation, the morphology and arrangements of the nucleus of the ablated tumor cells in the two groups showed no obvious alteration in HE stained sections, but in sections with enzyme histochemical staining, the activity of NADH-diaphorase in ablated tumor tissue at 60 degrees C disappeared, suggesting the death of HCC cells; sporadic activity of the enzyme was detected in the coagulated tumor at 50 degrees C, indicating tumor cells surviving the ablation. The ablation effect was markedly different between the two groups (P<0.01). CONCLUSION: HE staining is not suitable for evaluation of HCC destruction immediately after microwave ablation, and detection of NADH-diaphorase activity with the enzyme histochemical method better suits this purpose.

Animals↗
PubMed2006

Microbial inactivation by microwave radiation in the home environment.

The study reported here looked at the survival of microorganisms (heterotrophic plate counts, total coliforms, E. coli, and bacterial spores) in a consumer-type microwave oven. Kitchen sponges, scrubbing pads, and syringes were experimentally contaminated with wastewater and subsequently exposed to microwave radiation. At 100 percent power level, it was found that the heterotrophic plate count (i.e., total bacterial count) of the wastewater was reduced by more that 99 percent within 1 to 2 minutes, and the total coliform and E. coli were totally inactivated after 30 seconds of microwave radiation. Bacterial phage MS2 was totally inactivated within 1 to 2 minutes. Spores of Bacillus cereus were more resistant than the other microorganisms tested, and were completely eradicated only after 4-minute irradiation. Similar inactivation rates were obtained in wastewater-contaminated scrubbing pads. Microorganisms attached to plastic syringes were more resistant to microwave irradiation than those associated with kitchen sponges or scrubbing pads. It took 10 minutes for total inactivation of the heterotrophic plate count and 4 minutes for total inactivation of total coliform and E. coli. A 4-log reduction of phage MS2 was obtained after 2 minutes; 97.4 percent reduction was observed after 12 minutes. The authors also observed a higher inactivation of B. cereus spores in syringes placed in a ceramic container than of spores in syringes placed in a glass container. This finding could have some implications for the design of containers to be used in exposure of medical devices to microwave radiation. The article discusses the implications of these findings for consumer safety in the home environment.

Bacteria↗
PubMed1991

[Effects of sodium chloride on destruction of microorganisms by microwave heating in potatoes].

To assess the destructive effect of different sodium chloride concentrations (0, 0.3, 1.5, and 3%) on microorganisms with microwave heating, strains of Vibrio parahaemolyticus, Staphylococcus aureus, Salmonella enteritidis, Escherichia coli and Bacillus cereus were used to inoculate a mashed potato preparation. After microwave heating for 1 min at 800 W, resulted in temperatures and rate of destruction of bacteria significantly higher (p less than 0.05) in the core than on the surface of mashed potato when no salt was added. Except for B. cereus, microorganisms inoculated into mashed potato, with no added salt, could be completely destroyed by 2 min of microwave heating. Core temperatures and rate of destruction of microorganisms in the mashed potato decreased significantly (p less than 0.05) with increase in concentration of added salt. The results also indicate that bacterial species differ in their susceptibility to microwave inactivation. In particular, S. aureus, which exhibited a level of survival that was greater than that of any other species tested here, seemed notably resistant to microwave treatment for 2 min while V. parahaemolyticus was highly susceptible.

Bacteria↗
PubMed1991

Altered restriction patterns of microwave irradiated lambdaphage DNA.

Samples of lambdaphage DNA exposed to short pulses of microwave irradiation were subjected to restriction fragmentation by Eco RI and Bam HI. Eco RI digests of microwaved DNA samples yielded three additional fragments ranging in base pair lengths between 24,226 and 7,421 besides the six expected fragments. While Bam HI digests of the microwaved samples did not yield any additional fragments, mobilities of the Bam HI fragments from the microwaved DNA samples were slower and the bands were broader in comparison to those from native samples. We attribute these altered restriction patterns to the conformational anomolies in DNA resulting from single strand breaks and localized strand separations induced by microwave irradiation.

Amino Acid Sequence↗
PubMed1991

Microwave exposure alters the expression of 2-5A-dependent RNase.

The effects of 2.45-GHz continuous-wave microwaves (SAR = 130 mW/g) on the expression of the interferon-regulated enzymes 2'-5'-oligoadenylate (2-5A) synthetase(s) and 2-5A-dependent endoribonuclease (RNase L) were studied in murine L929 cells. Cells growing as monolayers were removed from the substratum and placed in suspension culture for a 4-h sham or microwave exposure. The cells were returned to monolayer growth for 18 h, and then harvested and assayed to determine the amount of RNase L protein (via [32P]2-5A binding) and the specific activities of RNase L and 2-5A synthetase. Binding of radioactive 2-5A to RNase L for sham- and microwave-exposed samples was 14.5 and 36.4% above control, respectively (the microwave-exposed bound 19.0% more probe than the sham-exposed). The increases in 2-5A binding were accompanied by corresponding elevations of RNase L specific activity. In contrast, sham or microwave irradiation produced no alterations in 2-5A synthetase specific activity. No detectable differences were noted in the postexposure cell viability, plating efficiency, or proliferation rate. Also, there were no detectable differences in cell viability or plating efficiency between controls and cultures irradiated for 2 h when the temperature was simultaneously increased to above normal physiological limits (39 to 45 degrees C). The SAR (130 mW/g) and the power density (95 mW/cm2) used for the greater part of this study were nearly 20 times higher than the ANSI limit of 8 mW/g and 5 mW/cm2 for any 1 g of exposed human tissue.

2',5'-Oligoadenylate Synthetase↗
PubMed1990

[Evaluation of the nutritive value of soybean milk prepared with microwave-treated soybeans].

Aqueous soybean extracts were prepared from beans, previously treated by microwaves to almost inactivate their lipoxygenase. These soy milks thus obtained were then nutritionally evaluated. All soy milks studied showed lower protein, fat, ash and total solids contents, as compared to a control milk prepared from soy beans not processed by microwaves. The milk obtained from soybeans with 8.7% initial moisture, treated by microwaves for 240 seconds, had the best total chemical score and the highest apparent methionine availability, as well as PER. The complete inactivation of the trypsin inhibitor activity was achieved with the milk prepared from soybeans with 56.8% initial moisture, subjected to microwave treatment for 180 seconds. On the other hand, the milk obtained from soybeans with 38.8% initial moisture, processed by microwaves for 180 seconds, resulted to have the highest, in vitro, protein digestibility.

Amino Acids, Essential↗
PubMed1990

Microwave-stimulated brain enzyme incubations are possible at the unphysiological condition of 50 degrees C.

Microwave-stimulated enzyme incubations for acetylcholinesterase, 5'-nucleotidase, alkaline phosphatase, lactate dehydrogenase, malate dehydrogenase, succinic dehydrogenase and isocitric dehydrogenase were studied, and compared with incubations in a waterbath. Temperature settings of 37 degrees C and 50 degrees C were used, and the incubation times were varied from 30 seconds to 30 minutes. The desired temperature of the incubation solution was reached in the microwave oven within 1 minute, whilst in the waterbath it took 10 to 25 minutes. The microscopic results for alkaline phosphatase and succinic dehydrogenase at a temperature setting of 50 degrees C were superior in the microwave method for incubation times less than 15 minutes. It is postulated that the increased reaction product of alkaline phosphatase and succinic dehydrogenase is due to a temperature effect, which has to be large enough to be of practical value. For the other enzymes studied, microwave-stimulated incubations were no better than the conventional incubations at corresponding temperatures. For 5'-nucleotidase there were aspecific lead deposits in the microwave method. All enzymes performed at the elevated, unphysiological temperature of 50 degrees C proved to have advantages, except for 5'-nucleotidase, whilst for malate dehydrogenase there was an aspecific reduction of the colour developer at this temperature.

Animals↗
PubMed1990

Physiological changes in rats after exposure to low levels of microwaves.

The effects of exposure to sublethal levels of microwaves were studied. Young albino rats of both sexes were exposed for 60 days to 7.5-GHz microwaves (1.0-KHz square wave modulation, average power 0.6 mW/cm2) for 3 h daily. During and after microwave exposure several physiological parameters were measured in both control and exposed animals. It was found that the animals exposed to microwaves tended to eat and drink less and thus showed a smaller gain in body weight. Some of the hematological parameters and organ weights were also significantly different. It is proposed that a nonspecific stress response due to microwave exposure and mediated through the central nervous system is responsible for the observed physiological changes.

Animals↗
PubMedDate not supplied

[The immune and hormonal effects of the local action of microwaves of different intensities].

The trend in immune and hormonal parameters in thyroid, adrenal and transcerebral exposure to microwaves with intensity of 120, 240 and 480 mW/cm2 was studied in rabbits. The thyroid exposure to 120 and 240 mW/cm2 microwaves lead to immunostimulation, while adrenal and transcerebral one induced immunosuppression. The exposure to 240 mW/cm2 and 480 mW/cm2 microwaves resulted in damage to the tissues in 56 and 100% of the animals, respectively. The latter irradiation appeared lethal for 25% of the rabbits. 120 mW/cm2 MV proved safe as there were no signs of edema and necrosis seen with more intensive microwaves. The authors suggest to employ microwaves of 120 mW/cm2 intensity for endocrine glands irradiation to produce an immunomodulating effect.

Adrenal Glands↗
PubMed1979

Quantitation of chronic microwave radiation effects on muscle cell electrical excitable properties: a temperature dependence analysis of the H-H cable and membrane current parameters of irradiated cells.

Frogs Rana pipiens maintained under constant laboratory environmental conditions were subjected daily to chronic microwave exposure with pulsed microwave (2.88 GHZ) at a power density of 10 mW/cm2, during 0.1 hour, for periods up to 100 days. The whole body Specific Absorption Rate (SAR) was of 1.5 mW/g per 1 mW/cm2. The passive and dynamic electrical parameters of sartorius muscle cells from control and irradiated frogs as a function of temperature in the range from 10 C to 30 C, have been analyzed. This temperature dependence analysis, presented in another work, was planned to be used in this paper for detecting those possible "masked" chronic microwave effects in complex membrane mechanisms highly temperature sensitive, and tightly related to the excitation and propagation of bioelectrical responses. The temperature dependence of the passive (Vr, Gm, Cm, and tau) and the active cell electrical parameters (theta, V*, Vs, VNa, Vn, V+, V-, kr, kNa, kK, tau Na, tau K, -gNa, gNa, gK, INa, and IK) was not altered by chronic microwave exposure. The striking observation reported in another work, about the presence of two groups of cell electrical parameters, characterized by their dependence with temperature, was reproduced on the irradiated muscle cells. Results have indicated that there was not muscle cell cumulative bioeffects resulting from microwave exposure to 10 mW/cm2, over a 0.1 hour period.

Action Potentials↗