Switchable scattering meta-surfaces for broadband terahertz modulation.

Active tuning and switching of electromagnetic properties of materials is of great importance for controlling their interaction with electromagnetic waves. In spite of their great promise, previously demonstrated reconfigurable metamaterials are limited in their operation bandwidth due to their resonant nature. Here, we demonstrate a new class of meta-surfaces that exhibit electrically-induced switching in their scattering parameters at room temperature and over a broad range of frequencies. Structural configuration of the subwavelength meta-molecules determines their electromagnetic response to an incident electromagnetic radiation. By reconfiguration of the meta-molecule structure, the strength of the induced electric field and magnetic field in the opposite direction to the incident fields are varied and the scattering parameters of the meta-surface are altered, consequently. We demonstrate a custom-designed meta-surface with switchable scattering parameters at a broad range of terahertz frequencies, enabling terahertz intensity modulation with record high modulation depths and modulation bandwidths through a fully integrated, voltage-controlled device platform at room temperature.

Significant performance enhancement in photoconductive terahertz optoelectronics by incorporating plasmonic contact electrodes.

Even though the terahertz spectrum is well suited for chemical identification, material characterization, biological sensing and medical imaging, practical development of these applications has been hindered by attributes of existing terahertz optoelectronics. Here we demonstrate that the use of plasmonic contact electrodes can significantly mitigate the low-quantum efficiency performance of photoconductive terahertz optoelectronics. The use of plasmonic contact electrodes offers nanoscale carrier transport path lengths for the majority of photocarriers, increasing the number of collected photocarriers in a subpicosecond timescale and, thus, enhancing the optical-to-terahertz conversion efficiency of photoconductive terahertz emitters and the detection sensitivity of photoconductive terahertz detectors. We experimentally demonstrate 50 times higher terahertz radiation powers from a plasmonic photoconductive emitter in comparison with a similar photoconductive emitter with non-plasmonic contact electrodes, as well as 30 times higher terahertz detection sensitivities from a plasmonic photoconductive detector in comparison with a similar photoconductive detector with non-plasmonic contact electrodes.

Coronal leakage following three obturation techniques.

AIM: To compare coronal bacterial and India ink leakage in three different obturation techniques with the smear layer having been removed. METHODOLOGY: Seventy extracted single-rooted teeth were instrumented to an apical preparation size 7 Profile Series 29 (Tulsa Dental Products, Tulsa, OK, USA). The smear layer was removed and 20 teeth were randomly obturated with lateral compaction, 20 teeth with vertical compaction, and 20 teeth with Thermafil (Tulsa Dental Products, Tulsa OK, USA). Ten teeth were used for positive (five teeth) and negative (five teeth) controls. Teeth were stored for 90 days in 100% humidity, then subjected coronally to Proteus vulgaris for 21 days to assess bacterial leakage. Following bacterial challenge, India ink was placed coronally for a further 21 days, then scored according to depth of dye leakage. RESULTS: Vertical compaction leaked significantly less than lateral compaction during bacterial challenge. However, when dye was used there were no significant differences. CONCLUSIONS: Bacterial leakage and dye leakage demonstrated considerable variability. The use of a dye following bacterial testing may highlight the failure of experimental devices and vertical root fractures, thus avoiding false positive results found with bacterial testing alone.

Assessing the clinical effectiveness of an aerosol reduction device for the air polisher.

BACKGROUND: Because of the growing concern of the infectious nature of aerosols produced by air polishers, the Centers for Disease Control and Prevention and the American Dental Association have made recommendations to minimize dental aerosols. In addition, a device was developed in 1997 to reduce the aerosol generated during air polishing. METHODS: The authors conducted a blinded clinical study to determine the effectiveness of an aerosol reduction device during air polishing. All 30 subjects underwent two minutes of air polishing, one with the aerosol reduction device on one side of the mouth and one without the device on the opposite side. Microbial samples were collected on blood agar plates positioned 12 inches from the subject's mouth and from one plate attached to the dental hygienist's face mask. The sample plates were then inverted and incubated for three days at 37 C. RESULTS: Using the paired t-test, the authors found that the air polisher without the aerosol reduction device generated a significantly greater mean quantity of colony-forming units, or CFUs, 12 inches from the subject's mouth (mean +/- standard deviation, 148.00 +/- 145.00 CFUs) than the air polisher with the aerosol reduction device (20.10 +/- 53.90 CFUs) (P < .0001). In addition, the air polisher without the aerosol reduction device generated a significantly greater number of CFUs on the face mask plate (40.90 +/- 33.80 CFUs) than the air polisher with the aerosol reduction device (8.80 +/- 15.10 CFUs) (P < .0001). CONCLUSION: The data suggest that the aerosol reduction device is effective in reducing the number of microorganisms generated during air polishing. CLINICAL IMPLICATIONS: Air polishing with the aerosol reduction device may decrease the potential for disease transmission.

The effectiveness of an aerosol reduction device for ultrasonic scalers.

Intraoral use of ultrasonic scalers may generate aerosols that contain infectious microorganisms and therefore pose a hazard to the health of the dental professional. The purpose of this in vivo study was to determine if an aerosol reduction device for an ultrasonic scaler would be effective in reducing the amount of contaminated aerosols produced during ultrasonic instrumentation. Twelve adult subjects participated in the study. A split-mouth design was utilized, and two treatments (in separate rooms) were performed on each subject: 1) ultrasonic scaling for 5 minutes with the aerosol reduction device; and 2) ultrasonic scaling for 5 minutes without the aerosol reduction device. The right or left side of the subject's mouth was randomly assigned to one of the two treatment groups. After instrumentation, the subject and operator remained motionless for 25 minutes during collection of aerosol particles. Air samples were collected on blood agar plates 6 inches from the subject's mouth. Replicate organism detection and counting plates were used to sample microorganisms present on the investigator's face shield. All plates were incubated for 3 days at 37 degrees C. The results, using the paired t-test (P < 0.001), indicate that the ultrasonic scaler without the aerosol reduction device had a significantly greater quantity of mean colony forming units (CFUs) 6 inches from the subject's mouth (45.1 +/- 28.9) than the ultrasonic scaler with the aerosol reduction device (2.6 +/- 3.6). No significant difference was evident in the number of CFUs found on the investigator's face shield. These data suggest that an aerosol reduction device is effective in reducing the number of microorganisms generated during ultrasonic scaling, therefore decreasing the risk of disease transmission.

The Euro-Team Early Pregnancy (ETEP) protocol for recurrent miscarriage.

The underlying causes and rationale for treatment of recurrent abortion are not entirely clear. The Euro-Team early pregnancy protocol was developed as a diagnostic work-up based on the evaluation of risk factors. Possibilities for therapy can be based only on the expectancy that elimination of some risk factors may improve the prognosis.

Antibacterial activity of dental implant metals.

This study was conducted to investigate the specific in vitro antibacterial effect of seven dental implant metals on oral bacteria which have often been identified in failing implants. The metals chosen for evaluation were titanium, chromium, cobalt, aluminum, iron, gold, and vanadium. These metals were selected because they are contained in many commonly used dental implants. The bacteria selected for this study included isolates of Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, Prevotella melaniogenica, Actinobacillus actinomycetemcomitans, Actinomyces naeslundii, and Actinomyces viscosus. Sets of tubes containing either supplemented trypticase soy broth, brain-heart infusion-yeast extract, or brain-heart infusion-yeast extract with 5 percent defibrinated rabbit blood were aseptically prepared with doubling dilutions of the seven metals starting at an initial concentration of 500 micrograms/ml and terminating at 0 microgram/ml. Cultures of each organism were inoculated into each set of broth tubes containing all concentrations of metals. Tubes were incubated either anaerobically or in an atmosphere of 5 percent carbon dioxide for 48 hours at 35 degrees C and then assayed for ATP content which was proportional to the viable cellular biomass. The results showed that, although being bacteria and concentration dependent, all seven metals suppressed the growth of each organism. The rank order of antibacterial activity expressed by dental implant metals was gold > titanium > cobalt > vanadium > aluminum > chromium > iron.

Comparison of antimicrobial and cytotoxic effects of glutaraldehyde and formocresol.

The in vitro antimicrobial and cytotoxic concentrations of glutaraldehyde and formocresol were determined. Minimal antimicrobial concentrations of these two agents against selected microbial flora reported in carious primary teeth were 3.125% for glutaraldehyde and 0.75% for formocresol. At a doubling of these concentrations, most organisms, except Candida albicans, Staphylococcus epidermidis, and Streptococcus mutans, were killed by both substances in 30 seconds. Cytotoxicity was evaluated on tissue cultures of pulp fibroblasts and HeLa cells at minimal cidal concentrations and at 10- and 100-fold dilutions. Exposure of pulp fibroblasts and HeLa cells to formocresol and indirect exposure to vapors caused the cells to become atrophic and to form a less dense tissue pattern. Cells directly exposed to glutaraldehyde retained their normal cell shape and tissue pattern, whereas cells indirectly exposed to vapors continued to proliferate. These data showed effective antimicrobial activity at concentrations of 3.125% glutaraldehyde and 0.75% formocresol and suggested that glutaraldehyde may exert a less cytotoxic effect on the immediate and surrounding tissues when used as a pulpotomy agent.

Antimicrobial properties of topical anesthetic liquids containing lidocaine or benzocaine.

Six species of microorganisms commonly found within the oral cavity were exposed for either one minute or two hours to 5% lidocaine liquid topical anesthetic and benzocaine liquid topical anesthetic. Mixtures of microorganisms and anesthetics were diluted and plated onto a brain heart infusion medium. Reduction in cell viability was 73-100% after exposure to the anesthetic agents when compared with the saline/buffer controls. A significant reduction (p < .005) in cell growth by Streptococcus mutans, S. sanguis, S. mitis, S. salivarius, Actinomyces viscosus, and Candida albicans was associated with a one-minute and two-hour exposure to lidocaine, benzocaine, 5% lidocaine, and the benzocaine vehicle control. Five percent lidocaine reduced growth of the test orgainisms more than benzocaine in one-minute exposures to S. mutans, A. viscosus and S. salivarius and with a two-hour exposure to S. salivarius.Five percent lidocaine was bacteriocidal or fungicidal to all microorganisms for both time periods whereas, benzocaine liquid topical anesthetic was predominately bacteriostatic or fungistatic after one-minute exposures and bacteriocidal or fungicidal after two hours.The results indicated that two dental liquid topical anesthetics containing lidocaine or benzocaine possessed considerable antimicrobial activity to selected oral microorganisms. The exclusive use of a topical liquid anesthetic may be an adequate means to render the oral mucosa aseptic before injection of a local anesthetic.

Incidence of temperature elevations after a full mouth dental rehabilitation under general anesthesia.

Fifty-seven patients underwent a full-mouth dental rehabilitation under general anesthesia at Texas Scottish Rite Hospital for Crippled Children. Thirty-eight subjects had complete data collected to monitor for temperature elevation. Nineteen subjects were discarded from the study due to incomplete data. The results showed 45 percent (seventeen subjects) had a significant temperature elevation to 38 degrees C or above. Sex of the subject made no difference. The significance temperature elevations occurred in the younger age-groups, especially in the one- to-five-year age-group. In the subjects with a significant temperature elevation after surgery, no definite pattern was evident as to when it would occur or how long it would last. The study population was divided into two groups, one with a significant temperature elevation to 38 degrees C or above, and the control group with temperatures below 38 degrees C. These groups were then compared to see whether their preoperative Oral Hygiene Index, Gingival Index, and soft tissue trauma or extraction of teeth showed a difference. No significant difference was found. This study is the first designed specifically to monitor temperature. It reported the highest percentage of subjects (45 percent) to have a postoperative temperature elevation, in comparison to other studies. Although no single factor could be found as the cause of the postoperative temperature elevation, combinations of the factors mentioned or the effects of anesthetic may have caused the elevations.

The antimicrobial effect of fluorides (acidulated phosphate, sodium and stannous) on Actinomyces viscosus.

The effect of three commercially prepared fluoride compounds (acidulated phosphate fluoride 1.23% F-, stannous fluoride 0.4%, and sodium fluoride 0.05%) diluted to various concentrations with brain heart infusion broth, on the growth of five strains of Actinomyces viscosus following 1 and 24 hours' exposure to the fluorides was studied. Results demonstrated that SnF2 was the most effective growth inhibitor of the organisms at 500 ppm F- after 1 hour and at 100 ppm F- after 24 hours' exposure. APF and NaF were not effective within a 1 hour exposure period, but did suppress growth of the organisms at 200 ppm in the cultures exposed for 24 hours.

A radioimmunoassay method for the rapid detection of Candida antibodies in experimental systemic candidiasis.

Rabbits were employed as experimental models to evaluate a solid-phase radioimmunoassay (RIA) method for the diagnosis of systemic candidiasis. Ten rabbits were inoculated subcutaneously to mimic superficial candidiasis and were found to produce no antibodies to Candida as determined by both immunodiffusion and RIA procedures. However, 94 per cent of 18 rabbits systemically infected by intravenous injection of Candida cells were observed to produce antibody as assessed by the RIA technique. These data encourage further tests with human sera and the continued development ofthis RIA procedure as a useful tool in the early serodiagnosis of systemic candidiasis.

The effect of adsorption on the acid production of caries and noncaries-producing streptococci.

Eighteen different Streptococcus strains including S mutans, sanguis, mitis, salivarius, bovis, and 2F2, were assayed for their relative adsorption to synthetic hydroxyapatite and for quantities of lactic acid produced while in the adsorbed state. The results indicated that all S mutans and some S sanguis have an enhanced metabolic activity while adsorbed to hydroxapatite as compared to control suspensions without hydroxyapatite.