Effect of dental surface treatment with Nd:YAG and Er:YAG lasers on bond strength of resin composite to recently bleached enamel

The aim of this work is to evaluate the effect of surface treatment with Er:YAG and Nd:YAG lasers on resin composite bond strength to recently bleached enamel. In this study, 120 bovine incisors were distributed into two groups: group C: without bleaching treatment; group B: bleached with 35% hydrogen peroxide. Each group was divided into three subgroups: subgroup N: without laser treatment; subgroup Nd: irradiation with Nd:YAG laser; subgroup Er: irradiation with Er:YAG laser. The adhesive system (Adper Single Bond 2) was then applied and composite buildups were constructed with Filtek Supreme composite. The teeth were sectioned to obtain enamel-resin sticks (1 x 1 mm) and submitted to microtensile bond testing. The data were statistically analyzed by the ANOVA and Tukey tests. The bond strength values in the bleached control group (5.57 MPa) presented a significant difference in comparison to the group bleached and irradiated with Er:YAG laser (13.18 MPa) or Nd:YAG (25.67 MPa). The non-bleached control group presented mean values of 30.92 MPa, with statistical difference of all the others groups. The use of Nd:YAG and Er:YAG lasers on bleached specimens was able to improve the bond strengths of them.

Evaluation of the shear bond strength of a composite resin in sound, demineralized and hypermineralized bovine dentin after irradiation with Er:YAG and Nd:YAG lasers, employing a self-etching adhesive system

Background and Objectives. The adhesion of dental materials is important for the success of treatment. The aim of this study is to evaluate the bond strength of a composite resin applied with a self-etching adhesive system in different dentins after irradiation with Er:YAG and Nd:YAG lasers, observing their morphologic pattern using Scanning Electronic Microscopy (SEM). Materials and Methods. The buccal surface of 72 bovine incisors was worn until exposure of medium depth dentin. The specimens were divided into three groups; GI: normal, GII: demineralized and GIII: hypermineralized dentin. These were also divided into two subgroups; A-irradiated for 30 s with Er:YAG laser in noncontact mode at 40 mJ and 6 Hz and B- irradiated for 30 s with Nd:YAG laser in contact mode at 60 mJ and 10 Hz. The adhesive system Clearfil SE. Bond (Kuraray) and composite resin Tetric Ceram (Vivadent) were applied on the irradiated area by the incremental technique. After storage for 24 h in distilled water at 37 degrees C, the specimens were submitted to the shear strength test in a universal testing machine (EMIC) at a crosshead speed of 1.0 mm/min. Other specimens were made to be analyzed by SEM. Results. The results were statistically analyzed by Analysis of Variance and the Tukey test. Regardless of the type of dentin, the bond strength of specimens irradiated with the Nd:YAG laser (8,94 +/- 2,07) was higher compared to specimens irradiated with the Er:YAG laser (7,03 +/- 2,47); the highest bond strength was obtained for the group of hypermineralized dentin irradiated with the Nd:YAG laser. The SEM analysis showed that the Er:YAG laser caused opening of tubules and the Nd:YAG laser produced areas of fusion as well as regions of opening of dentinal tubules. Conclusions. The dentin showed different morphological patterns and the laser promote alterations on their surfaces, influencing the bond strength of the composite resin. (C) 2010 Laser Institute of America.

Assessment of external root temperature during root canal irradiation by Nd:YAG and Er:YAG lasers

Different types of laser have been widely studied for applicability in the oral health area. In the endodontic area, investigations with some types of laser have been conducted to establish safe parameters for clinical application in root canals. However, it has not been duly explained whether the temperature increase caused by laser irradiation could cause alteration in the temperature on the external surface of the root and, consequently, alterations in the cells of the periodontal ligament, causing resorption and even loss of the dental element. The proposal in this paper was to gauge the external root temperature in the apical and cervical regions of the roots of human teeth during root canal irradiation with Nd:yttrium aluminum garnet (YAG) and Er:YAG lasers using different parameters. The novel approach of this paper is the use of the technique of laser applications along the total length of the root canal with series of repetitive irradiation, however, using time of 1 s of irradiation associated with 1 s off to avoid cumulative thermal effects. Experimental results confirm the accuracy of the parameters and exposure regimen obtained. All the parameters used in this paper are acceptable from a clinical as well as a biological point of view. (C) 2009 Laser Institute of America.

Microleakage and nanoleakage: Influence of laser in cavity preparation and dentin pretreatment

Objective: the purpose of this study was to verify if the application of the Nd:YAG laser following pretreatment of dentin with adhesive systems that were not light cured in class V cavities and were prepared with Er:YAG laser would promote better sealing of the gingival margins when compared to cavities prepared the conventional way. Background Data: Previous studies had shown that the pretreatment of dentin with laser irradiation after the application of an adhesive system is efficient in achieving higher shear bond and tensile bond strength. Materials and Methods: Er:YAG laser (Kavo-Key, Germany) with 350 mJ, 4 Hz, and 116.7 J/cm(2) was used for cavity preparation. The conventional preparation was made with diamond bur mounted in high-speed turbine. Dentin treatment was accomplished using an Nd:YAG laser (Pulse Master 1000, ADT. USA) at 60 mJ, 10 Hz, and 74.65/cm(2) following application of the adhesive system. The cavities were stored with Single Bond/Z100 and Prime & Bond NT/TPH. Eighty bovine incisors were used, and class V preparations were done at buccal and lingual surfaces divided into eight groups: (1) Er:YAG preparation + Prime & Bond NT + TPH; (2) Er:YAG preparation + Single Bond + Z100; (3) Er:YAG preparation + Single Bond + Nd:YAG + Z100; (4) Er:YAG preparation + Prime & Bond NT + Nd:YAG + TPH; (5) conventional preparation + Prime & Bond NT + TPH; (6) conventional preparation + Single Bond + Z100; (7) conventional preparation + Single Bond + Nd:YAG + Z100; (8) conventional preparation + Prime & Bond NT + Nd:YAG + TPH. All specimens were thermocycled for 300 full cycles between 5 degreesC +/- 2 degreesC and 55 degreesC +/- 2 degreesC (dwell time of 30 sec), and stored in 50% silver nitrate solution for 24 h soaked in photodeveloping solution and exposed to fluorescent light for 6 h. After this procedure, the specimens were sectioned longitudinally in 3 portions and the extension of microleakage at the gingival wall was determined following a criteria ranging from 0 to 4 using scanning electron microscopy (SEM). The medium portion sectioned of each specimen was polished and prepared for nanoleakage avaliation by SEM. Results: Kruskall-Wallis and Miller statistical tests determined that group 3 presented less microleakage and nanoleakage. Conclusion: Application of the Nd:YAG laser following pretreatment of dentin with adhesive Single Bond non-photocured Single Bond adhesive in cavities prepared with Er:YAG promote better sealing of the gingival margins.

Electron trapping of laser-induced carriers in Er-doped SnO2 thin films

In order to investigate optically excited electronic transport in Er-doped SnO2, thin films are excited with the fourth harmonic of an Nd:YAG laser (266nm) at low temperature, yielding conductivity decay when the illumination is removed. Inspection of these electrical characteristics aims knowledge for electroluminescent devices operation. Based on a proposed model where trapping defects present thermally activated cross section, the capture barrier is evaluated as 140, 108, 100 and 148 meV for doped SnO2, thin films with 0.0, 0.05, 0. 10 and 4.0 at% of Er, respectively. The undoped film has vacancy levels as dominating, whereas for doped films. there are two distinct trapping centers: Er3+ substitutional at Sn lattice sites and Er3+ located at grain boundary. (C) 2007 Elsevier Ltd. All rights reserved.

Apatite coatings onto titanium surfaces submitted to laser ablation with different energy densities

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Time-resolved Z-scan and thermal lens measurements in Er+3 and Nd+3 doped fluoroindate glasses

In rare earth ion doped solids, a resonant non-linear refractive index, n2, appears when the laser pumps one of the ion excited states and the refractive index change is proportional to the excited state population. In these solids there are usually thermal and non-thermal lensing effects, where the non-thermal one is due to the polarizability difference, Δα, between excited and ground states of the ions. We have used the time resolved Z-scan and a mode-mismatched thermal lens technique with an Ar+ ion laser in Er+3 (20ZnF2-20SrF2-2NaF-16BaF2-6GaF3-(36 - x)InF3-xErF3, with x= 1, 2, 3 and 4 mol%) and Nd+3 (20SrF2-16BaF2-20ZnF2-2GdF3-2NaF-(40 - x)InF3-xNdF3, with x = 0.1, 0.25, 0.5-1 mol%) doped fluoroindate glasses. In both samples we found that the non-linear refraction is due to the thermal effect, while the non-thermal effect is negligible. This result indicates that in fluoride glasses Δα is very small (less than 10-26 cm3). We also measured the imaginary part of the non-linear refractive index (n″2) due to absorption saturation.

One-dimensional analytical model for oxide thin film growth on Ti metal layers during laser heating in air

This paper presents the theoretical and experimental results for oxide thin film growth on titanium films previously deposited over glass substrate. Ti films of thickness 0.1 μm were heated by Nd:YAG laser pulses in air. The oxide tracks were created by moving the samples with a constant speed of 2 mm/s, under the laser action. The micro-topographic analysis of the tracks was performed by a microprofiler. The results taken along a straight line perpendicular to the track axis revealed a Gaussian profile that closely matches the laser's spatial mode profile, indicating the effectiveness of the surface temperature gradient on the film's growth process. The sample's micro-Raman spectra showed two strong bands at 447 and 612 cm -1 associated with the TiO 2 structure. This is a strong indication that thermo-oxidation reactions took place at the Ti film surface that reached an estimated temperature of 1160 K just due to the action of the first pulse. The results obtained from the numerical integration of the analytical equation which describes the oxidation rate (Wagner equation) are in agreement with the experimental data for film thickness in the high laser intensity region. This shows the partial accuracy of the one-dimensional model adopted for describing the film growth rate. © 2001 Elsevier Science B.V.

Evaluation of titanium implants with surface modification by laser beam. Biomechanical study in rabbit tibias

The purpose of the present study was to evaluate, using a biomechanical test, the force needed to remove implants with surface modification by laser (Nd:YAG) in comparison with implants with machined surfaces. Twenty-four rabbits received one implant with each surface treatment in the tibia, machined surface (MS) and laser-modified surface (LMS). After 4, 8 and 12 weeks of healing, the removal torque was measured by a torque gauge. The surfaces studied were analyzed according to their topography, chemical composition and roughness. The average removal torque in each period was 23.28, 24.0 and 33.85 Ncm for MS, and 33.0, 39.87 and 54.57 Ncm for LMS, respectively. The difference between the surfaces in all periods of evaluation was statistically significant (p < 0.05). Surface characterization showed that a deep and regular topography was provided by the laser conditioning, with a great quantity of oxygen ions when compared to the MS. The surface micro-topography analysis showed a statistical difference (p < 0.01) between the roughness of the LMS (R a = 1.38 ± 0.23 μm) when compared to that of the MS (R a = 0.33 ± 0.06 μm). Based on these results, it was possible to conclude that the LMS implants' physical-chemical properties increased bone-implant interaction when compared to the MS implants. © 2009 Sociedade Brasileira de Pesquisa Odontológica.

Upconversion ultraviolet random lasing in Nd 3+ doped fluoroindate glass powder

An upconversion random laser (RL) operating in the ultraviolet is reported for Nd 3+ doped fluoroindate glass powder pumped at 575 nm. The RL is obtained by the resonant excitation of the Nd 3+ state 2G 7/2 followed by energy transfer among two excited ions such that one ion in the pair decays to a lower energy state and the other is promoted to state 4D 7/2 from where it decays emitting light at 381 nm. The RL threshold of 30 kW/cm 2 was determined by monitoring the photoluminescence intensity as a function of the pump laser intensity. The RL pulses have time duration of 29 ns that is 50 times smaller than the decay time of the upconversion signal when the sample is pumped with intensities below the RL laser threshold. © 2011 Optical Society of America.

Laser stimulated light reflection for TeO2-WO 3-Bi2O3 thin films with incorporated Si nanoparticles

A novel method of preparation of the Si nanoparticles (NPs) incorporated in tellurite TeO2-WO3-Bi2O3 (TWB) thin films is proposed. This mew method applies RF magnetron sputtering technique at room temperature. The incorporation of Si NP was confirmed by transmission electron microscopy (TEM); isolated Si NPs with diameters of around 6 nm are observed. Energy dispersive X-ray spectroscopy (EDS) was performed during TEM analysis in order to confirm the presence of Si NP and also the other elements of the thin film. The thin films are explored with respect to the photoinduced changes of the reflectivity within the 400-65 nm spectra range using a 10 ns pulsed Nd:YAG with power densities varying up to 400 MW/cm2 and beam diameter within the 3-5 mm range. The observed processes are analyzed within a framework of trapping level conceptions for the Si NP. The possible application of the discovered materials as optical sensitive sensors is proposed. © 2013 Elsevier B.V.

Resistência à cárie de esmalte dental irradiado por lasers de Er:YAG e Nd:YAG, avaliada através da morfologia e proporção Ca/P

Pós-graduação em Ciências Odontológicas - FOAR

Recobrimentos cerâmicos bioativos pelo processo sol-gel sobre Ti c.p. modificado por laser empregados em implantes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise da superfície de titânio sob ação do laser com e sem deposição de hidroxiapatita

Pós-graduação em Odontologia - FOA

Influência de aplicações do laser érbio:YAG sobre a viabilidade microbiana, sua resistência a drogas e atividade hemolítica

Pós-graduação em Odontologia - FOA