Antimicrobial efficacy of sodium hypochlorite and hyper-pure chlorine dioxide in the depth of dentin tubules in vitro.

OBJECTIVES: The study aimed to compare the antibacterial effect of a novel disinfectant, hyper-pure chlorine dioxide (hClO2) to sodium hypochlorite (NaOCl) in various depths of dentin tubules. MATERIALS AND METHODS: The distal root of the extracted lower molars was infected artificially with Enterococcus faecalis. The control group was rinsed with saline, and the test groups were irrigated with either 5% NaOCl or 0.12% hClO2. The longitudinally split teeth were stained by viability stain. The coronal third of the root was scanned with a confocal laser scanning microscope. The fluorescent intensities were measured, and the percentage of dead bacteria was calculated at depths up to 950 µm along the dentin tubules. The effect of penetration depth, irrigants, and their interaction on antimicrobial efficacy was determined by the linear mixed model. RESULTS: The percentage of dead bacteria was higher both in the NaOCl (45.1 ± 2.3%, p < 0.01) and in the hClO2 (44.6 ± 3.8%, p < 0.01) irrigant groups compared to saline (23 ± 4.5%); however, there was no difference between them. The percentage of killed bacteria was not correlated with the depths in any group (p = 0.633). CONCLUSIONS: Our results suggest that the functional penetration depth of NaOCl is at least 2-3 times more than published to date. There is no difference in disinfection effectiveness along the dentin tubules between NaOCl and hClO2 until at least the measured 950 µm. However, both were only able to eradicate the intratubular bacteria partially. CLINICAL RELEVANCE: Hyper-pure ClO2 could be used as an alternative or final adjuvant irrigant in endodontic treatment.

Sonic anemometer data processing for comparison to optical turbulence theory and simulation.

With appropriate processing techniques, sonic anemometry can provide useful insights into the strength and spectral shape of optical turbulence. Closed form propagation models and simulations require stationary optical turbulence statistics to make a meaningful comparison with experimental results. This work presents a new approach for examining the stationarity of data provided by sonic anemometry and by fitting optical turbulence parameters. Von Kármán, Greenwood-Tarazano, and one minus exponential spectral models are fitted to experimental data. Each model fit is evaluated using information criteria. The Greenwood-Tarazano model is shown to provide the best fit to experimental data. Optical turbulence parameters from the Greenwood-Tarazano model are compared with results from instruments at varying heights above the ground.

Laser-plasma coupling for enhanced ablation of GaAs with combined femtosecond and nanosecond pulses.

The laser-plasma interactions that occur during the ablation of solid materials by a femtosecond filament superimposed with a lower-intensity nanosecond pulse are investigated. Pulses of 50 fs duration with intensities of ∼1014 W/cm2 centered at 800 nm are combined with 8 ns pulses at 1064 nm with ∼1010 W/cm2 intensity with delays of ±40 ns on crystalline GaAs targets in air. For each delay, the volume of material removed by a single femtosecond-nanosecond dual-pulse is compared to the laser-plasma interactions that are captured with ultrafast shadowgraph imaging of the plasma and shockwave generated by each pulse. Sedov-Taylor analysis of the shockwaves provides insight on the coupling of energy from the second pulse to the plasma. These dynamics are corroborated with radiation-hydrodynamics simulations. The interaction of the secondary pulse with the pre-existent plasma is shown to play a critical role in enhancing the material removal.

Comparative extreme ultraviolet emission measurements for lithium and tin laser plasmas.

Detailed spectroscopic studies on extreme UV emission from laser plasmas using tin and lithium planar solid targets were completed. At 13.5 nm, the best conversion efficiency (CE) for lithium was found to be 2.2% at intensities near 7 x 10(10) W/cm(2). The highest CE measured for tin was near 5.0% at an intensity close to 1 x 10(11) W/cm(2).