The Effectiveness of Low-Intensity Red Laser for Activating a Bleaching Gel and Its Effect in Temperature of the Bleaching Gel and the Dental Pulp

Statement of the Problem: The effectiveness of low-intensity red laser for activating a bleaching gel and its effect in pulp temperature was not investigated in dental literature. Purpose: The objective of this study was to assess the effectiveness of low-intensity red laser for activating a bleaching gel, as well as its effect in temperature of the bleaching gel and the dental pulp. Materials and Methods: Forty extracted bovine teeth were immersed in a solution of coffee 14 days for darkening. The initial colors were recorded by spectrophotometric analysis. The specimens were randomly distributed into two groups (N = 20): the control, which did not receive light and the experimental group that received light from an appliance fitted with three red light-emitting laser diodes (? = 660 nm). A green-colored, 35% H2O2based bleaching gel was applied for 30 minutes, and changed three times. After bleaching, the colors were again measured to obtain the L*a*b* values. Color variation was calculated (?E) and the data submitted to the non-paired t-test (5%). To assess temperature, 10 human incisors were prepared, in which one thermocouple was placed on the bleaching gel applied on the surface of the teeth and another inside the pulp chamber. Results: There was a significant difference between the groups (p = 0.016), and the experimental group presented a significantly higher mean variation (7.21 +/- 2.76) in comparison with the control group (5.37 +/- 1.76). There was an increase in pulp temperature, but it was not sufficient to cause damage to the pulp. Conclusion: Bleaching gel activation with low-intensity red laser was capable of increasing the effectiveness of bleaching treatment and did not increase pulp temperature to levels deleterious to the pulp. CLINICAL SIGNIFICANCE The application of a low-intensity red laser was effective for activating a bleaching gel with green dye, without any deleterious increases in pulpal temperature. (J Esthet Restor Dent 24:126134, 2012)

Medidor de energia para laser pulsado

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Microestrutura e resistência à corrosão do Ti c.p. soldado a laser utilizando em prótese sobre implantes

Foram realizados estudos para avaliar a microestrutura, a dureza e a resistência à corrosão do titânio comercialmente puro-Ti c.p. soldado por laser e utilizado na confecção de prótese sobre implantes. Verificou-se que na soldagem a laser a microestrutura apresentou três regiões distintas: o cordão de solda, a zona afetada pelo calor - ZAC e o metal base. O Ti c.p. possui microestrutura granular, a microestrutura do cordão de solda é mais refinada e de maior dureza do que o metal base. A ZAC obtida por este processo de soldagem foi relativamente pequena quando comparada com o processo de soldagem por brasagem. Os ensaios eletroquímicos mostraram que a região da solda apresentou menor resistência à corrosão em meio de NaCl 0,15 molL-1 à temperatura ambiente.

Estudo microestrutural e resistência à corrosão de uma liga de Au soldada a laser, empregada em prótese sobre implantes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hydroxyapatite deposition study through polymeric process on commercially pure Ti surfaces modified by laser beam irradiation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fluoride uptake and acid resistance of enamel irradiated with Er : YAG laser

This study evaluated the resistance to demineralization and fluoride incorporation of enamel irradiated with Er:YAG. A total of 110 bovine teeth were selected and divided into eight groups: unlased, 37% phosphoric acid, and samples irradiated with the Er:YAG laser at several fluences (31.84 J/cm(2), 25.47 J/cm(2), 19.10 J/cm(2), 2.08 J/cm(2), 1.8 J/cm(2), and 0.9 J/cm(2)). The application of acidulated phosphate fluoride was performed after treatments. All samples were immersed in 2 ml of 2.0 M acetic-acetate acid solution at pH 4.5 for 8 h, and fluoride, calcium, and phosphorus ions dissolved were analyzed by atomic absorption spectrometry and spectrophotometry. The phosphoric acid and 31.84 J/cm(2) groups presented the lowest dissolution of calcium and phosphorus ions. Higher fluoride incorporation was observed on 1.8 J/cm(2) and 0.9 J/cm(2) groups. Based on these results, Er:YAG laser was able to decrease acid dissolution and increase fluoride uptake and can be a promissory alternative for preventive dentistry.

Investigação da Interface Metal-Porcelana da Liga Ni-Cr-Mo Soldada a LASER

The interface formed between the metal and the porcelain of a LASER welded Ni-Cr-Mo alloy was studied. The characterization was carried out through optical microscopy, scanning electron microscopy, X-ray dispersive spectroscopy-EDS and mechanical testing by three-point flexion test-TPE in the region LASER welded with and without the porcelain. The porcelain adhesion with the alloy alone is possible after the oxidation of the metallic surface and subsequent application of an adhesive called opaco. The applied porcelain, on the base metal and fusion zone presented some distinct behaviors. After the TPF test the base metal presented fractures while that in the fusion zone was completely gone. One noticed that the region submitted to the LASER welding showed less porcelain adhesion than the region of the base metal due to the microestructural refinement of the fusion zone. These results can be evidenced by the EDS of the studied regions. The TPF had demonstrated that the Ni-Cr-Mo alloy submitted to the LASER welding, undergone significant alterations in its mechanical properties after the application of the porcelain.

Production of defects in ZBLAN, ZBLAN : Tm3+ and ZBLAN : Cr3+ glasses by ultra-short pulses laser interaction

In this work we have studied pure and thulium- and chromium-doped ZBLAN glasses irradiated by ultra-short laser pulses. A Ti:sapphire CPA system was used, producing a 500 Hz train of pulses, centered at 830 nm, with 375 mu J of energy and 50 fs of duration (FWHM). The beam was focused by a 20 Him lens, producing a converging beam with a waist of 12 pin. The absorption spectra before and after laser irradiation were obtained showing production of color centers in pure, thulium-doped and chromium-doped ZBLAN glasses. A damage threshold of 9.56 TW/cm(2) was determined for ZBLAN. (C) 2007 Elsevier Ltd. All rights reserved.

Efeitos da radiação laser de dióxido de carbono em tecido ósseo: estudo macroscópico em ratos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeitos od laser CO2 na mandíbula de ratos: Estudo através da microscopia eletrônica de varredura

A face lateral do corpo da mandíbula de ratos foi irradiada pelo laser CO2 com disparos contínuos de 10watts de potência. Após três meses, o sulco formado pela irradiação apresentou, em uma grande extensão, material fundido com diversas fraturas. Após sete meses, o periósteo neoformado recobriu amplas áreas da incisão, que apresentou ainda material carbonizado. Um ano após a incisão, o periósteo neoformado estava composto por fibras colágenas, que formaram feixes espessos, transversais à incisão, ou malhas regulares, que recobriram a incisão. Ainda nessa fase, resquícios de material carbonizado foram verificados, caracterizando um retardo na regeneração óssea

Influência da energia de soldagem em uniões de lâminas finas através de laser pulsado de Nd:YAG

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

FAR INFRARED-LASER LINES AND ASSIGNMENTS OF CH3OH - A REVIEW

Methyl alcohol is the most important lasing molecule in the Far-Infrared (FIR) spectral region, and the most widely used for investigation and for applications. Since the last critical review of 1984, over seventy papers have been published dealing with the FIR laser lines and the infrared spectroscopy of CH3OH. In 1984 we could list about 330 FIR laser lines, 98 of which were measured in frequency and 105 assigned. Since then more than 70 papers were published increasing the number of the known laser lines to 575 (103 measured in frequency). Also the FIR and IR spectroscopy was largely improved thanks to the analysis of high resolution FT spectra, and the number of the correctly assigned laser lines has been increased to 224. The wavenumbers of the assigned lines can now be predicted with an accuracy of about 0.001 cm-1 or better, thus approaching the accuracy of the experimental frequency measurements.

Enhanced multiwavelength holographic profilometry by laser mode selection

A method for improving the accuracy of surface shape measurement by multiwavelength holography is presented. In our holographic setup, a Bi12TiO20 photorefractive crystal was the holographic recording medium, and a multimode diode laser emitting in the red region was the light source in a two-wave mixing scheme. on employing such lasers the resulting holographic image appears covered with interference fringes corresponding to the object relief, and the interferogram spatial frequency is proportional to the diode laser's free spectral range (FSR). Our method consists in increasing the effective free spectral range of the laser by positioning a Fabry-Perot etalon at the laser output for mode selection. As larger effective values of the laser FSR were achieved, higher-spatial-frequency interferograms were obtained and therefore more sensitive and accurate measurements were performed. The quantitative evaluation of the interferograms was made through the phase-stepping technique, and the phase map unwrapping was carried out through the cellular-automata method. For a given surface, shape measurements with different interferogram spatial frequencies were performed and compared with respect to measurement noise and visual inspection. (c) 2007 Society of Photo-Optical Instrumentation Engineers.