CO2 and diode laser for excisional biopsies of oral mucosal lesions. A pilot study evaluating clinical and histopathological parameters

PURPOSE: The present pilot study evaluates the histopathological characteristics and suitability of CO2 and diode lasers for performing excisional biopsies in the buccal mucosa with special emphasis on the extent of the thermal damage zone created. PATIENTS AND METHODS: 15 patients agreed to undergo surgical removal of their fibrous hyperplasias with a laser. These patients were randomly assigned to one diode or two CO2 laser groups. The CO2 laser was used in a continuous wave mode (cw) with a power of 5 W (Watts), and in a pulsed char-free mode (cf). Power settings for the diode laser were 5.12 W in a pulsed mode. The thermal damage zone of the three lasers and intraoperative and postoperative complications were assessed and compared. RESULTS: The collateral thermal damage zone on the borders of the excisional biopsies was significantly smaller with the CO, laser for both settings tested compared to the diode laser regarding values in pm or histopathological index scores. The only intraoperative complication encountered was bleeding, which had to be controlled with electrocauterization. No postoperative complications occurred in any of the three groups. CONCLUSIONS: The CO2 laser seems to be appropriate for excisional biopsies of benign oral mucosal lesions. The CO2 laser offers clear advantages in terms of smaller thermal damage zones over the diode laser. More study participants are needed to demonstrate potential differences between the two different CO2 laser settings tested.

Light-emitting diode and laser fluorescence-based devices in detecting occlusal caries

The aim of this study was to assess the performance of two light-emitting diode (LED)- and two laser fluorescence-based devices in detecting occlusal caries in vitro. Ninety-seven permanent molars were assessed twice by two examiners using two LED- (Midwest Caries - MID and VistaProof - VP) and two laser fluorescence-based (DIAGNOdent 2095 - LF and DIAGNOdent pen 2190 - LFpen) devices. After measuring, the teeth were histologically prepared and classified according to lesion extension. At D1 the specificities were 0.76 (LF and LFpen), 0.94 (MID), and 0.70 (VP); the sensitivities were 0.70 (LF), 0.62 (LFpen), 0.31 (MID), and 0.75 (VP). At D(3) threshold the specificities were 0.88 (LF), 0.87 (LFpen), 0.90 (MID), and 0.70 (VP); the sensitivities were 0.63 (LF and LFpen), 0.70 (MID), and 0.96 (VP). Spearman's rank correlations with histology were 0.56 (LF), 0.51 (LFpen), 0.55 (MID), and 0.58 (VP). Inter- and intraexaminer ICC values were high and varied from 0.83 to 0.90. Both LF devices seemed to be useful auxiliary tools to the conventional methods, presenting good reproducibility and better accuracy at D(3) threshold. MID was not able to differentiate sound surfaces from enamel caries and VP still needs improvement on the cut-off limits for its use.

Coherent phase contrast imaging of THz phonon-polariton tunneling

We report on coherent spatiotemporal imaging of single-cycle THz waves in frustrated total internal reflection geometry. Our technique yields images of the spatiotemporal electric field distribution before and after tunneling through an air gap in between two LiNbO3 crystals. Measurements of the reflected and the transmitted THz waveforms for different tunnel distances allow for a direct comparison with results from a causal linear dispersion theory and excellent agreement is found.

Prospective ex-vivo study on thermal effects in human skin phototypes II, IV and VI: a comparison between the 808, 1064, 1210 and 1320-nm diode laser

Laser Assisted Skin Healing (LASH) was first introduced in 2001 by Capon and Mordon to prevent keloids and hypertrophic scars. LASH requires homogenous heating throughout the full thickness of the skin around the wound. However, LASH therapy with 808-nm diode laser is deemed to be only applicable for phototype I-IV due to melanin absorption. This prospective ex-vivo study aims to evaluate the thermal effects of different wavelengths (808, 1064, 1210 and 1320 nm) on human skin phototype II, IV and VI.

1.9 µm diode laser assisted vascular microanastomoses: Experience in 40 clinical procedures

Since the initial work of Jacobson and Suarez in 1960, microsurgery has evolved greatly. In 2009, we reported our clinical experience with 1.9 µm diode laser-assisted vascular microanastomoses (LAMA) for free flap reconstruction. In this report, the ongoing study is now expanded to include 11 additional procedures which were analyzed prospectively with a focus on the duration of the LAMA technique.

[Blood flow assessment with magnetic resonance imaging after 1.9 μm diode laser assisted arterial micronastomoses]

The most important factor for successful free-flap transfer and replantations is a well-executed anastomosis. The aim of this study is to assess blood flow after laser assisted arterial microanastomosis (LAMA) using a 1.9 μm diode laser.

Structural aspects of redox-mediated electron tunneling (Dedicated to the memory of professor Alexander M. Kuznetsov)

We investigated structural aspects of electron transfer (ET) in tunneling junctions (Au(1 1 1)vertical bar FcN vertical bar solution gap vertical bar Au STM tip) with four different redox-active N-thioalk(ano)ylferrocenes (FcN) embedded. The investigated molecules consist of a redox-active ferrocene (Fc) moiety connected via alkyl spacers with N = 4, 6, 8 and 11 carbon atoms to a thiol anchoring group. We found that for short FcNs (N = 4, 6,8) the redox-mediated ET response increases with the increase of the alkyl chain length, while no enhancement of the ET was observed for Fc1 1. The model of two-step ET with partial vibrational relaxation by Kuznetsov and Ulstrup was used to rationalize these results. The theoretical ET steps were assigned to two processes: (1) electron tunneling from the Fc group to the Au tip through the electrolyte layer and (2) electron transport from the Au(1 1 1) substrate to the Fc group through the organic adlayer. We argue that for the three short FcNs, the first process represents the rate-limiting step. The increase of the length of the alkyl chain leads to an approach of the Fc group to the STM tip, and consequently accelerates the first El' step. In case of the Fcl 1 junctions the rather high thickness of the organic layer leads to a decrease of the rate of the second ET step. In consequence, the contribution of the redox-mediated current enhancement to the total tunneling current appears to be insignificant. Our work demonstrates the importance of combined structural and transport approaches for the understanding of Er processes in electrochemical nanosystems. (C) 2010 Elsevier B.V. All rights reserved.

Vibronic Spectra of Jet-Cooled 2-Aminopurine center dot H2O Clusters Studied by UV Resonant Two-Photon Ionization Spectroscopy and Quantum Chemical Calculations

For understanding the major- and minor-groove hydration patterns of DNAs and RNAs, it is important to understand the local solvation of individual nucleobases at the molecular level. We have investigated the 2-aminopurine center dot H2O. monohydrate by two-color resonant two-photon ionization and UV/UV hole-burning spectroscopies, which reveal two isomers, denoted A and B. The electronic spectral shift delta nu of the S-1 <- S-0 transition relative to bare 9H-2-aminopurine (9H-2AP) is small for isomer A (-70 cm(-1)), while that of isomer B is much larger (delta nu = 889 cm(-1)). B3LYP geometry optimizations with the TZVP basis set predict four cluster isomers, of which three are doubly H-bonded, with H2O acting as an acceptor to a N-H or -NH2 group and as a donor to either of the pyrimidine N sites. The "sugar-edge" isomer A is calculated to be the most stable form with binding energy D-e = 56.4 kJ/mol. Isomers B and C are H-bonded between the -NH2 group and pyrimidine moieties and are 2.5 and 6.9 kJ/mol less stable, respectively. Time-dependent (TD) B3LYP/TZVP calculations predict the adiabatic energies of the lowest (1)pi pi* states of A and B in excellent agreement with the observed 0(0)(0) bands; also, the relative intensities of the A and B origin bands agree well with the calculated S-0 state relative energies. This allows unequivocal identification of the isomers. The R2PI spectra of 9H-2AP and of isomer A exhibit intense low-frequency out-of-plane overtone and combination bands, which is interpreted as a coupling of the optically excited (1)pi pi* state to the lower-lying (1)n pi* dark state. In contrast, these overtone and combination bands are much weaker for isomer B, implying that the (1)pi pi* state of B is planar and decoupled from the (1)n pi* state. These observations agree with the calculations, which predict the (1)n pi* above the (1)pi pi* state for isomer B but below the (1)pi pi* for both 9H-2AP and isomer A.

Multi-stage ytterbium fiber-amplifier seeded by a gain-switched laser diode

We demonstrated all-fiber amplification of 11 ps pulses from a gain-switched laser diode at 1064 nm. The diode was driven at a repetition rate of 40 MHz and delivered 13 µW of fiber-coupled average output power. For the low output pulse energy of 325 fJ we have designed a multi-stage core pumped pre-amplifier in order to keep the contribution of undesired amplified spontaneous emission as low as possible. By using a novel time-domain approach for determining the power spectral density ratio (PSD) of signal to noise, we identified the optimal working point for our pre-amplifier. After the pre-amplifier we reduced the 40 MHz repetition rate to 1 MHz using a fiber coupled pulse-picker. The final amplification was done with a cladding pumped Yb-doped large mode area fiber and a subsequent Yb-doped rod-type fiber. With our setup we reached a total gain of 73 dB, resulting in pulse energies of >5.6 µJ and peak powers of >0.5 MW. The average PSD-ratio of signal to noise we determined to be 18/1 at the output of the final amplification stage.