Continuous Wave Carbon Dioxide Laser Research Articles

Effects of Irradiation of Continuous Wave Carbon Dioxide Laser on Caries Resistance of Deciduous Teeth

The objective of this st udy aimed to assess the caries-preventive potential of various CW CO2 laser parameters, and to explore the effect of the laser power density on the caries inhibition activity.Extracted human deciduous molars were irradiated with three various power dens ities, by changing the output power, the exposure time, and the spot diameter. The CO2 laser system emitted laser with 10.6µm in wavelength. All teeth were subjected to carieslike lesion form ation by 3.5 pH lactic acid for 21 days. The teeth after that were sectioned into ground cross sections and the lesion depths were measured under a polarizing microscope.CW CO2 laser preventive treatments inhibited carieslike lesion progres sion up to 82%. This effect was improved with increasing power d ensity within the limits of the examined laser parameters.

Evaluating the efficacy of continuous wave carbon dioxide laser therapy in conjunction with biologics for the management of hidradenitis suppurativa.

Evaluating the efficacy of continuous wave carbon dioxide laser therapy in conjunction with biologics for the management of hidradenitis suppurativa.

Limited Systemic Sclerosis-Associated Calcinosis Cutis of the Fingers Treated Successfully With Ablative Continuous-Wave Carbon Dioxide Laser and Curettage.

*Martin Army Community Hospital, Georgia; †Department of Dermatology, Walter Reed National Military Medical Center, Bethesda, Maryland The authors have indicated no significant interest with commercial supporters. The views expressed in this work are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, Defense Health Agency, or U.S. government. I certify that all individuals who qualify as authors have been listed; each has participated in the conception and design of this work, the writing of the document, and the approval of the submission of this version; that the document represents valid work; that if used information derived from another source, I obtained all necessary approvals to use it and made appropriate acknowledgements in the document; and I take public responsibility for it.

The evaluation of prepared microstructure pattern by carbon-dioxide laser on zirconia-based ceramics for dental implant application: an in vitro study.

3mol% yttria-stabilized zirconia ceramics have been gaining attention as promising restorative materials that are extensively used in dental implant applications. However, implant failure due to bacterial infection and its bioinert surface slow osseointegration in vivo, which are significant issues in clinical applications. In this work, surface modification was achieved using a continuous wave carbon dioxide laser at a wavelength of 10.6µm in an air atmosphere. Changes in the surface characteristics were evaluated using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and 2D roughness and hardness tests. The bioactivity of the laser-treated samples was studied by examining their behavior when immersed in the SBF solution. The formation of the hydroxyapatite phase on the laser-treated sample was much more uniform than that of its untreated counterparts. The antibacterial properties of surface-treated zirconia ceramics against Streptococcus mutans and Escherichia coli bacteria were rigorously examined. These results indicate that the laser-induced nanoscale grooves significantly improved antibacterial activity by creating hydrophobic surfaces. The cellular response was evaluated for 7days on microtextures on the zirconia surfaces and an untreated sample with MC3T3-E1 pre-osteoblast cell line cultured under basal conditions. Surface topography was revealed to improve the cellular response with increased metabolic activity compared to the untreated sample and showed modulation of cell morphology for the entire time. These results suggest that laser modification can be an appropriate non-contact method for designing nanoscale microtextures to improve the biological response and antibacterial behavior of zirconia ceramics in restorative dentistry.

Enhancement of Mechanical Properties and Corrosion Resistance of Cast Iron Alloy Using CO2 Laser Surface Treatment

This work aimed to study the effect of laser surface treatment on the mechanical characteristics and corrosion behaviour of grey cast iron type A159. Many technical applications used conventional surface treatment, but laser surface hardening has recently been used to enhance the surface properties of many alloys. The mechanical characteristics, including microstructure, microhardness, and wear resistance of A159 grey cast iron, were studied, in addition to corrosion behaviour. The experimental laser parameters in this work were 0.9, 1.2, and 1.5 KW power with continuous wave carbon dioxide lasers with scanning speeds of 10 and 12 mm/s were used. The results found that phase-transitional alterations in microstructure were influenced by laser therapy. Also, the microhardness increased with increasing power, with the maximum reaching approximately 950 HV while the base metal has an average of approximately 260 HV. Also, we found the power laser increased corrosion resistance by lowering the corrosion rate (CR) from 21.10 for the untreated sample to 1.02 (m.p.y.), additionally, corrosion protection efficiency (CPE) increased to 95.27 percent. On the other hand, the wear test revealed that mass loss decreased as laser surface treatment power increased; it reached 0.19 g for the laser-treated samples, compared to 1.25 g for the base metal after the 50th minute of the wear experiment.

32522 Refractory calcinosis cutis in limited systemic sclerosis treated with CO2 ablation and curettage

We present a case of a 50-year-old woman with limited systemic sclerosis with debilitating digital calcinosis cutis. Our patient reported tenderness with moderate limitation of her daily activities secondary to her fingertip nodules. She had previously undergone multiple debridements with orthopedic surgery under general sedation or with a nerve block. Due to the postoperative pain and logistical difficulty involved with the orthopedic surgeries, she opted to forgo further orthopedic surgery and presented to our dermatology department for evaluation. With dermatology, she trialed topical sodium thiosulfate twice a day for 6 months with no improvement, followed by intralesional sodium thiosulfate every 2 weeks for 4 months without notable benefit. Ultrasounds were performed to objectively assess response to treatment. Due to insufficient response, the patient successfully underwent 3 separate trials of continuous wave carbon dioxide (CO2) laser ablation followed by curettage for a 3 symptomatic nodules. There were no recurrences of the treated nodules at 6 months. She has experienced significant improvement in discomfort and functionality. Ablative CO2 laser therapy has rarely been used for treating digital calcinosis cutis, largely due to the appropriate concern for poor wound healing. However, in a review of the literature performed by Melone et al of 70 scleroderma patients requiring 272 hand operations did not reveal any complications with wound healing. We present this case to highlight ablative CO2 as a potential therapeutic option for patients with calcinosis cutis refractory to noninvasive methods.

Thermal Effect on Thin-Film Formation of the Polymer Sheets by the CO2 Laser with the Copper Base.

A method that makes polymer sheets partially thinner with continuous-wave carbon dioxide (CO2) lasers has been developed. This method can create thin polymer films by attaching the polymer sheets to the copper base by vacuum suction through the holes in the base. Applying the method to polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polytetrafluoroethylene (PTFE), the thin-film formation is confirmed in PP, PET, and PS but not PTFE. These polymers have the similar thermal properties. PP, PET, and PS show fluidity with increased temperature, but PTFE does not have fluidity. These characteristics of the polymers indicate that the fluidity of polymer is the important characteristic for film formation. The experiments with PP and PET sheets of different thickness show that thicker sheets make thicker films. The fluid flow of the molten polymer is considered to form the thin film at the bottom of the groove made by laser scribing. The numerical simulation of the 2D thermal model also indicates the week cooling effects of the base on the film formation and importance of polymer fluidity. The results of Fourier transform infrared spectrometer (FT-IR) show thermal degradation of the films. To decrease the heat’s effect on the films, the polymer sheets should be processed at the highest laser-beam scanning speed that can make thin films.

Microstructural Design of the Cast Iron via Laser Hardening with Defocused Beam of the Continuous Wave CO2 Laser

The cast iron is widely used in mechanical parts due to its good properties, as damping, good fluidity, resistance to deformation, excellent machinability and low cost. However, the number of its applications are reduced because its low corrosion, wear and friction resistance. The microstructure of the metallic materials has high influence on these properties. Laser hardening can improve these properties via designing of the microstructure. The evaluation of the laser parameter influence on the microstructural features is vital for a correct design of the microstructure and therefore, good improvement of the metallic material properties. Although the various laser parameter influence has been analysed on sundry papers, the influence of the distance from focal point and scan speed in the laser hardening microstructures has been rarely evaluated in the literature. Thus, the influence of this parameter on the microstructures generated through laser hardening is the subject matter of this work. The experiments were carried out with continuous wave carbon dioxide laser on samples of ground cast iron. The atmosphere was air flow at 0.7MPa, the laser operated at 100W and the scan rates were 1mm/s and 5mm/s. The distances to focal point of the laser beams ranged from 0.0mm to 5.6mm. The microstructures of the samples were revealed via nital and evaluated with optical microscopy. This work shown that the microstructure of gray iron cast can be designed by mean of laser hardening. In addition, laser hardened zones had various microstructures (e.g. austenitic, martensitic, pearlite and dendritic). The type of the microstructures in laser treated zones was determined by distance from focal point and scan speed. Moreover, the width and the depth of the laser hardened zones were generally enlarged with the increasing of the distance from focal point. Furthermore, the laser irradiation at slow rates, i.e. 1mm/s, produced laser hardened zones larger than laser scan at 5mm/s. In future works, the hardness, wear and friction resistance of the laser hardened samples will be evaluated because the literature review indicates that austenitic and martensitic microstructures show high values of these properties.

Thermal stress cleavage of a single-crystal round sapphire bar by carbon dioxide laser

This study is the first attempt of applying thermal stress cleavage to a single-crystal round sapphire bar having a morphologically continuous circumference surface. Previously, thermal stress cleavage was only applied to brittle material substrates or wafers owing to the crack propagation behaviour induced by thermal stress distribution. To overcome this issue, a V-shaped groove was prepared on the circumference as an initial point for crack propagation, and a continuous-wave carbon dioxide (CO2) laser was used as the heat source. The thermal stress behaviour was simulated via finite element analysis, and the effect of the initial crack morphology on the thermal stress behaviour was evaluated. In addition, the crack propagation was monitored using an acoustic emission sensor, and the separation mechanism of the round sapphire bar was investigated. Results indicated that the thermal stress cleavage using the CO2 laser beam allowed the complete separation of the round sapphire bar with the V-shaped groove without any final edge remaining. The crack propagation behaviour was determined from the relationship between the thermal stress distribution and morphology change during crack propagation. The fabricated sharp V-shaped groove improved the quality of the cleaved surface, and the high aspect ratio of the groove enabled a high-quality cleavage. The initial crack propagation immediately after the start of laser beam irradiation was affected by the tip of the V-shaped groove, and the crack propagation direction could be controlled through the tip morphology of the V-shaped groove.

Laser-driven electron storage rings

Advanced accelerator concepts usually address linear acceleration schemes. Storage rings, however, are often superior to linear machines regarding repetition rate, stability and efficiency. The radiative energy loss per turn in an electron storage ring is compensated by radiofrequency resonators with a wavelength of the order of 1 meter, which corresponds to the spacing between consecutive potential wells, so-called buckets, and results in a bunch length around 1 centimeter or several 10 picoseconds. As an alternative, longitudinal focusing could be performed by a laser wave co-propagating with the electrons in an undulator. Considering a continuous-wave carbon dioxide laser beam as an example, the bucket spacing would be 10.6 micrometer with a bunch length in the femtosecond range. The paper discusses chances and limitations of such a laser-driven storage ring concept with steady-state femtosecond bunches.

Investigation on the effect of laser remelting for laser cladding nickel based alloy

Laser cladding is a recently developed additive manufacturing technique, which is widely used in remanufacturing and sustainable manufacturing fields. However, the surface roughness of laser cladding layer often fails to meet the tribological functions and assembly requirements. In order to improve the surface finish quality of laser cladding, various techniques such as manual polishing, grinding, abrasive blasting, and chemical polishing were adopted. However, these methods have certain disadvantages, such as secondary positioning and polluting the environment. Laser remelting is an eco-friendly technology, which is based on remelting of a thin surface layer and can improve surface quality without the secondary positioning. In this paper, the high-power continuous-wave carbon dioxide laser was first used for preparing laser cladding layer of nickel-based alloy and then used for laser remelting process. Design of experiments based on orthogonal arrays was employed for optimization of process parameters. Both surfaces of laser cladding and laser remelting, as well as the cross-sectional subsurface, were analyzed to investigate the variation of surface roughness. Scanning electron microscopy and energy dispersive spectrometer were used to analyze the microstructure of the remelted sample. It was shown that the average surface roughness of laser cladding layer was reduced more than 2 μm after laser remelting process. Microstructure and microhardness of laser remelting zone were investigated in order to examine the thermal effect of laser remelting processing on the laser cladding layer. It can be induced that laser remelting process is an effective method to improve the surface quality of laser cladding.

Laser Surface Modification of Carbon Fiber Reinforced Composites

The removal of top resin layer is an essential task prior to adhesive bonding of carbon fiber reinforced polymer (CFRP) composites. This paper investigates the technical feasibility of using a low power continuous wave carbon dioxide laser for removing the top resin layer of CFRP without damaging the underlying fiber. The operating window and damaging threshold were experimentally determined. Irradiating the CFRP surface at a power of 14 W, scanning speed of 880 mm/sec, and a beam overlap of 25% provides an optimal thermal condition for removal of top resin layer. A finite element model was used to explain the removal mechanisms.

The effects of different laser doses on skin

Directly after the exposure, biopsies of normal and exposed skin were preserved and fixed for histological studies. The images obtained from the compound light and electron microscopes exerted changes contributed to the interaction of the skin cells to the heat and energy produced by the continuous wave carbon dioxide (CW CO2) laser during the exposure time. Basically, the tissue damage caused by the laser was mainly due to photothermal effect and increased gradually as the irradiation dose increased. Epidermal loss along with coagulation, homogenous hyalinization, lost of hair associated with shrinkage and collapse of hair follicle structures of varying depths at the-burn sites were detected in the histologic sections. Damage-power density (DPD) relationship was confirmed by measuring the damage depth using the software provided in the light microscope. On the other hand, Scanning electron microscopy (SEM) showed detailed images of the extensive epidermal epithelial cells damage which also increased by increasing the laser dose. Rough surface, partial destruction of intercellular junctions giving rise to loss of adherence between squamous cells and formation of narrow spaces between these cells were the most evident changes detected. The findings may help specialists to choose the best laser parameters for certain applications.

Comparison of CO2laser and atmospheric plasma treatments on thermal stability and structural modifications of microporous poly(vinyl chloride)/Silica composites

Several ways using surface modification are commonly used to enhance thermal stability of polymer matrices. In this study, Continuous-Wave carbon dioxide (CW CO2) laser irradiation and atmospheric pressure non-thermal He plasma treatment on microporous poly(vinyl chlo-ride)/Silica composite have been investigated and compared. On one hand the alternative was based on the efficiency of the thermal energy afforded by CW CO2 laser irradiation and induced photodegradation processes to release HCl and form polyene sequences under well-controlled condition. On the other hand atmospheric plasma treatment involved surface modification by formation of unstable radicals, inducing crosslinking and dehydrochlorination. In both cases a global thermal stabilization of the composite was noticed by partial dehydrochlorination of PVC, even for short exposure time. The main effects observed after laser irradiation were related to the formation of a very dense structure on surface with very low chlorine content and an important chlorine atoms in-depth gradient on the cross section up to 150 μm in thickness; whereas atmospheric He plasma treatment led to a homogeneous decrease of the chlorine in-depth content due to the plasma interpenetration in the porous microstructure. Structural and chemical modifications both on extreme surface and in the thickness have been investigated respectively by Environmental Scanning Electron Microscope (ESEM) coupled with an Energy Dispersive X-ray analysis (EDX) and X-ray Photoelectron Spectroscopy (XPS). Composites thermal stability and investigation on chlorine release have been evaluated by Thermo Gravimetric Analysis (TGA) coupled with Mass Spectrometry (MS).

Experimental investigation of laser surface processing of flexure silicon nitride ceramic

A continuous wave carbon dioxide (CO 2) laser (λ=10.6 μm) was employed to treat the surface of Si 3N 4 MOR (modulus of rupture) bars. The effects of the CO 2 laser process on physical and mechanical properties of ground Si 3N 4 samples were investigated. Scanning electron microscopy (SEM) analysis shows that the area occupied by cavities and fracture is decreased by about 49.4% after laser treatments. Cross-sectional metallography results indicate that the secondary YSiAION phase in the Si 3N 4 ceramic is softened/melted and flowed into the defects. Four-point bending tests show that the flexural strength of the treated samples is improved to 10.9%. Fractographic analysis show that the fracture origins move from the surface to subsurface. It is concluded that laser surface processing have significant effects on fracture behavior of flexure Si 3N 4 ceramic.

Angiokeratoma Circumscriptum Naeviforme: Successful Treatment with Carbon-Dioxide Laser Vaporization

Angiokeratoma circumscriptum naeviforme (ACN) is an unusual type of localized angiokeratoma that occurs more frequently in females and is usually located on the buttocks or thighs, showing a unilateral distribution. ACN usually causes large lesions, which may require laser ablation because they often are too extensive to perform surgical excision. Carbon-dioxide laser is a known alternative for treating angiokeratomas. Report of two cases of ACN treated with carbon-dioxide laser vaporization. A 28-year-old woman with a hyperkeratotic, violaceus plaque on her left buttock and a 24-year-old woman with a similar lesion on her right buttock were treated with a carbon-dioxide laser. Two laser passes were performed on each lesion within a single session. A successful cosmetic aspect of treated areas was obtained, with minimal pigmentary or textural changes. After a 2-year follow-up in the first patient and a 6-month follow-up in the second patient, no recurrence of the lesions was observed. Our results, obtaining relevant cosmetic improvement after a few sessions of treatment, with low morbidity and minimal secondary effects, suggest that continuous-wave carbon-dioxide laser vaporization is a safe and effective treatment for ACN.

Laser CO2 continu dans le traitement des hamartomes épidermiques verruqueux

Verrucous epidermal nevus are benign epidermal hyperplasias. Their treatments are disappointing because of recurrences and anaesthetic scars. The aim of this study was to evaluate the efficacy of continuous carbon dioxide laser in the treatment of verrucous epidermal nevus. It was a retrospective study concerning all patients treated for epidermal verrucous nevus by carbon dioxide laser from 1991 to 2003. Several criteria were evaluated by the patients, a dermatologist and a staff (external observers). Aesthetic result, recurrences, pain due to treatment and global result were evaluated by the patients when they came back. Twenty-one patients (12 F and 9 M), medium age 20.4, were evaluated with a 40.4 months follow-up (7 to 165 months). The epidermal verrucous nevus was situated on the neck or on the head for 62% of them (n = 13). Among these 21 patients, 86% (n = 19) estimated their skin as "cured" or "nearly normal" or "much improved". The rate was the same for the dermatologist. As for the staff, thanks to photos, only 53% of results were satisfying. The recurrences were never complete, but moderate in 38% of patients. Five patients, medium age 12,5, had hypertrophic scars. Among them, three were only partially hypertrophic. A literature review has been made. Our satisfaction rates (nearly 90%) were slightly higher than other studies rates using carbon dioxide laser (74%) or other types of lasers (87%). The medium follow-up was longer than the one of other laser CO2 studies (26.7 months) or other lasers studies' (15.8 months). This study shows that continuous wave carbon dioxide laser is an easy and effective treatment of verrucous epidermal nevus. Aesthetic results are satisfying but moderate recurrences often occur. To prevent hypertrophic scars, we suggest to exclude teenagers.

Controlling thermal damage of incisions using diamond, copper, and sapphire heat-conducting templates with and without cooling

We investigated the reduction of thermal damage to the surrounding tissue when laser incisions were made with and without using thermal conducting templates at room temperature and cooled to 5 degrees C. We used the Vanderbilt free-electron laser (FEL) at 5.4, 6.1, 6.45, and 7.7 microns. We also used a conventional continuous wave (CW) carbon dioxide laser at 10.6 microns. Incisions were made on 5x10 mm pieces of human breast skin (in vitro) and analyzed with histology. Computer morphometrics were used to measure the amount of thermal damage. All templates produced a statistically significant reduction in the thermal damage. Additionally, we showed that cooling the templates made a statistically significant greater reduction in the thermal damage. The cooled diamond template reduced the thermal damage from the FEL to 28% of the damage observed without a template. The same cooled template reduced the thermal damage from the CO(2) laser to 56% of the damage observed without a template. Lesser reductions were observed with the copper template and even less with the sapphire template. The sapphire template reduced the thermal damage to 39 and 67% of the damage observed without a template for the FEL and the CO(2) laser, respectively. These results indicate that unwanted lateral thermal damage from laser incisions can be reduced with cooled thermally conductive templates with the best results obtained with the diamond template, which is also the best thermal conductor.

The generation and frequency measurement of short-wavelength far-infrared laser emissions

A significantly improved three-laser heterodyne system has been assembled to generate and measure short-wavelength far-infrared (FIR) laser emissions. Over the past several years, this system has been used to discover fifty-five FIR laser emissions, ranging in wavelength from 26.3 to 185.0 /spl mu/m. These emissions were generated by optically pumping a FIR cavity with a continuous-wave carbon dioxide laser in a X-V geometry when using either hydrazine or a methanol isotopologue as the FIR laser medium. Although heterodyne techniques can be used to measure the frequencies of these FIR laser emissions with fractional uncertainties of /spl plusmn/2/spl times/10/sup -7/, shortcomings in the previous system limited its effectiveness. Improvements made to the three-laser heterodyne system have resulted in an increase in the spectral range used to search for the beat between the known and unknown laser frequencies (an increase of up to 25 GHz) as well as an increase in the system's sensitivity (by up to a factor of 30), all without requiring the use of an additional microwave frequency source. With this improved system, the FIR laser frequencies for the recently discovered 53.9- and 90.0-/spl mu/m laser emissions generated by optically pumped CH/sub 3/OD have been measured.

Measurement of far-infrared laser frequencies generated by optically pumped N2H4 and N2D4

A three-laser heterodyne system has been used to measure the frequencies of four previously observed far-infrared laser emissions generated by optically pumping either hydrazine (N2H4) or its fully deuterated isotope (N2D4) with a continuous-wave carbon dioxide laser. These newly measured frequencies have fractional uncertainties of ± 2 × 10−7 and correspond to laser wavelengths ranging from 63.9 to 158.4 μm. This work represents the first measurement of a N2D4 laser frequency.