Laser Pretreatment Research Articles

Effect of Er:YAG laser pretreatment on glass-ceramic surface in vitro.

This study investigated the feasibility of using an Er:YAG laser to pretreat glass-ceramic surface and evaluate the effect of the treatment on the bonding strength and marginal adaptation between glass-ceramic and dentin. Glass-ceramic samples (CEREC Blocs) and third molars were cut into 6mm × 6mm × 2mm plates. Thirty ceramic plates were randomly divided into 5 groups: group A (control), group B (pretreated with 9.6% hydrofluoric acid [HF]), group C (pretreated with the Er:YAG laser at 300mJ and 15Hz), group D (pretreated with the Er:YAG laser at 400mJ and 15Hz), and group E (pretreated with the Er:YAG laser at 500mJ and 15Hz). The surface morphologies of the samples in each group were studied under a scanning electron microscope, and the sample displaying optimal etching parameters was selected for subsequent experiments. Based on the surface treatments, 30 ceramic and dentin plates were randomly allocated into 3 groups: the control, laser, and acid-etching groups. After bonding a ceramic plate to a dentin plate, the microleakage and bonding strength were measured, and the pretreatment effects of the Er:YAG laser and 9.6% HF were compared. Group E exhibited an etching effect that was more pronounced and uniform than that in groups C and D. Microleakage and bonding strength analyses revealed that the laser and acid-etching groups differed significantly from the control group in dye penetration depth and shear strength (P < 0.05), although the laser and acid-etching groups did not differ from each other. Both 9.6% hydrofluoric acid and Er:YAG laser pretreatments can coarsen glass-ceramic surfaces, improve the marginal adaptation and bonding strength between the glass-ceramic and dentin, and decrease microleakage of the materials. The two treatments showed no apparent differences in pretreatment outcomes.

Efficacy evaluation and dermoscopy predictors of photodynamic therapy with different pretreatments in the treatment of actinic keratosis

Objective The aim of this study was to accurately evaluate the efficacy of photodynamic therapy (PDT) on actinic keratosis (AK) in the Asian population and its relationship with preconditioning and dermoscopy grading, and to determine whether some dermoscopic features of AK can independently predict the response to PDT to optimize the choice of clinical treatment. Materials and Methods From January 2017 to January 2020, patients who were diagnosed as AK with only one lesion in our hospital were included in our study. PDT was performed after pretreatment with ablative fractional CO2 laser or cryotherapy. Logistic regression analysis was used to evaluate the characteristics of dermoscopy to determine the independent predictors of efficacy. Results A total of 95 patients were enrolled in the study, and the final clinical evaluation was 92 cases (96.8%) as complete remission and 3 cases (3.2%) as partial remission/no response. Dermoscopy showed complete remission in 77 cases (81.1%) and partial remission/no response in 18 cases (18.9%). No significant difference was observed in the complete remission rate of dermoscopy grade 1 lesion after laser or cryotherapy pretreatment (p > 0.05), but for dermoscopy grade 2 and grade 3 lesions, the complete remission rate (dermoscopy evaluation) of the cryotherapy pretreatment group was higher than that of laser group (p < 0.05). The probability of complete remission with red pseudonetwork at the T0 time point increased by 3.8 times (odds ratio [OR] = 3.870,95%confidence interval [CI]:1.077–13.912, p = 0.048), while the probability of complete response for lesions with slight erosion at the baseline decreased by 85% (OR = 0.150,95%CI:0.033–0.671, p = 0.013). Conclusion For dermoscopy grade 2 and 3 lesions, PDT after pretreatment with cryotherapy is more effective. Dermoscopy pseudo-reticular structure and microscopic erosions were independent predictors of PDT efficacy. These findings may help clinicians to better select patients with AK for PDT.

Quantifying Skin Uptake of Topicals After 1,927-nm and 1,440-nm Nonablative Fractional Diode Laser Treatment.

Although the stratum corneum limits transdermal absorption of topicals, laser devices can enhance topical uptake by disrupting the skin barrier. Nonablative lasers are commonly used, but their effects on topical uptake should be quantified to optimize outcomes. The objective of this study is to analyze transdermal uptake of 4 topicals after nonablative fractional diode laser pretreatment. Human donor tissue was pretreated ex vivo with a nonablative fractional diode laser (1,927 nm or 1,440 nm, at varying treatment densities, powers, and peak energies) followed by application of either 2% salicylic acid, 10% ascorbic acid, over-the-counter mineral eye serum, or 4% hydroquinone. Topical uptake was quantified over 24 hours. Despite lower power settings, pretreatment with the 1,927 nm wavelength was associated with greater uptake of 10% ascorbic acid, mineral eye serum, and 4% hydroquinone than the 1,440 nm wavelength. In addition, 1,440-nm laser pretreatment with higher density (320 microscopic treatment zones [MTZ]/cm 2 ) and peak power (3 W) was associated with similar uptake but greater retention of 2% salicylic acid and greater uptake of 10% ascorbic acid than that with lower density (80 MTZ/cm 2 ) and peak power (1.2 W). When using laser pretreatment, device settings should be adjusted to balance outcomes with potential side effects.

Couple batch-injection analysis and microfluidic paper-based analytical device: A simple and disposable alternative to conventional BIA apparatus.

Under controlled dispersion conditions, sample injection towards a detector opened essential fields for the Analytical Chemistry fast development methods. Flow injection analysis (FIA) and batch injection analysis (BIA) systems are crucial for injecting the sample in these analytical methods. The BIA system eliminated the flow manifold, with samples injected directly onto the detector inside the batch injection cell. Paper was slightly evaluated coupled to FIA, and no reports were found associated with BIA. Still, it can potentially reduce the BIA manifold by removing the batch injection cell based on the capillarity properties to disperse the injected solution over the detection system. Hence, this article reported the first work coupling batch-injection analysis and microfluidic paper-based analytical device (BIA-μPAD) with pencil-drawn electrodes directly attached to the paper using a CO2 laser pre-treated chromatographic paper. The laser pretreatment of the paper (optimized conditions: 6.5% laser power, 12mms-1 scan rate, and 12mm output distance) was essential to enhance the electrochemical response for ferri/ferrocyanide redox couple and paracetamol (PAR), as shown by spectroscopic and electrochemical techniques. The proposed BIA-μPAD was evaluated using pharmaceutical paracetamol samples as proof-of-concept (optimized conditions: 15μL injected volume and 6.4μLs-1 dispensing rate), obtaining good linearity (R=0.9961) and recovery values ranging from 95 to 103%. Repeatability (n=16) and reproducibility (n=9) tests with 1mmolL-1 PAR also presented well relative standard deviation (RSD) results of 5.1% and 6.6%, respectively. A sampling frequency of 76 h-1 was obtained, which is a similar value compared with conventional BIA apparatus. Limits of detection and quantification were estimated in 0.046 and 0.154mmolL-1, respectively. Additionally, an improvement in the current response and the sample throughput was observed when comparing FIA and BIA-μPADs, attesting the applicability of the proposed device and opening for new possibilities related to paper-based devices coupled with flow techniques.

Effect of laser pretreatment and laser cladding on the interface bond strength and surface properties of vermicular graphite

Effect of laser pretreatment and laser cladding on the interface bond strength and surface properties of vermicular graphite

A comparative study on the adhesive bonding strength of unidirectional, 4-Harness Satin weaved and plain weaved carbon fibre reinforced polymer after KrF excimer laser pre-treatment

Several types of carbon fibre reinforced polymers (CFRP) are available based on the appearance of the carbon fibre laminates. In this study, three distinct types of CFRPs, namely, unidirectional (UD CFRP), 4-Harness Satin weaved (4HSW CFRP) and plain weaved (PW CFRP) were selected to compare the bonding strength performance of specific CFRP/CFRP adhesive joints after KrF laser pre-treatment. KrF excimer laser with top hat beam profile was utilized. This treatment increased the Sq and Sdr values significantly for all three CFRP types. KrF laser affected the matrix polymer C-N bonds and converted the tertiary and secondary aliphatic amines to secondary and primary amines, respectively, after de-polymerization. Single lap shear stress (SLSS) test revealed that the average adhesive bonding strength achieved respectively for UD CFRP, 4HSW CFRP and PW CFRP after KrF laser pre-treatment were 32.80, 23.97 and 35.21 MPa which were 104.34%, 47.24% and 39.72% higher than their pristine counterparts. Repeatability of the SLSS results were more for weaved pattern CFRPs. Adhesive failure reduced drastically and presence of cohesive failure, thin layer cohesive failure and fibre tear failure were prevalent in SLSS for all considered CFRPs. Comparison of all results showed that the best performance was obtained for PW CFRP.

Efficient drying of laser-treated raspberry in a pulse-spouted microwave freeze dryer

Pulse-spouted microwave freeze drying (PSMFD) has been shown to be more energy efficient than the conventional vacuum freeze dryer. PSMFD yields higher drying rate and better energy efficiency due to volumetric heating. Because of the mass transfer resistance due to the berry’s epidermal barrier during drying, the raspberry skin was subjected to laser pretreatment so as to perforate the surface with pre-selected number of fine holes generated by a CO2 laser. The perforations allow vapor generated within the bulk of the berry to escape with no resistance of the waxy skin. In addition to studying the effect of perforation parameters on drying time; therefore, quality indicators of the dried product (shrinkage ratio, hardness, rehydration capacity, color, flavor, and anthocyanin content) were also explored. The micropore parameters in experiments were set as follows: P-0 (no perforations), P-3 (12 perforations), P-6 (24 perforations), and P-9 (36 perforations). As expected, greater the number of perforations per berry shorter is the drying time, by up to 23.08%. Moreover, the shortened drying time has a positive effect on product quality as well. The shrinkage rate could be reduced by about 3.95% and the retention rate of anthocyanin could be increased by 20.02%.

Obtaining colored patterns on polyamide fabric with laser pretreatment and pomegranate peel dyeing

Increasing environmental and sustainability considerations have led to the revival of natural dyes. Even though the application of natural dyes on natural substrates has been extensively investigated, research regarding simultaneous dyeing, patterning and functional finishing of polyamide fabrics is reported to a limited extent. This paper aims at obtaining colored patterns on polyamide fabrics by laser pretreatment and dyeing with pomegranate peel dye. The most notable color difference can be obtained by using a 12 W laser and 2% (on weight of the fabric) pomegranate peel dye. The significant color difference between laser pretreated and untreated areas showed the pattern. It was then used for the further pattern design of polyamide fabrics combined with computer-aided design software. The dyed fabric had good color fastness, and no mordant was used in the dyeing process. In addition, the dyed fabrics were endowed with various functional properties by pomegranate peel dye.

Influence of high pulse fluence infrared laser surface pretreatment parameters on the mechanical properties of CFRP/aluminium alloy adhesive joints

ABSTRACT Laser surface pretreatment is an effective approach for improving the mechanical properties of adhesive joints. In the case of laser surface treatment of carbon fibre reinforced polymer (CFRP), ultraviolet (UV) lasers and lower pulse fluence infrared (IR) lasers are usually used to ensure the surface pretreatment quality. With respect to improving the surface treatment efficiency as much as possible, the influence of higher pulse fluence (12.7 J/cm2) IR laser pretreatment parameters on the mechanical properties of CFRP/aluminium alloy hybrid joints were investigated in this study. Scanning electron microscopy (SEM), contact angle measurements, confocal laser scanning microscope (CLSM), and X-ray photoelectron spectroscopy (XPS) were used to analyse the surface modification and failure modes of the adhesive surface. Additionally, the influence of the IR laser pretreatment parameters on the failure mode of CFRP/aluminium alloy adhesive joints under tension loading was discussed. The results showed that in addition to surface free energy, subsurface damage and mechanical interlocking were important factors affecting the shear strength of CFRP/aluminium alloy adhesive joints when a higher pulse fluence IR laser was applied for surface pretreatment. Finally, the optimized laser surface pretreatment parameters considering both the treatment efficiency and quality were obtained for the CFRP/aluminium alloy adhesive joint.

Prostaglandin Release After Low-Energy Femtosecond Laser-Assisted Cataract Surgery Without Anti-Inflammatory Drug Premedication

To compare prostaglandin E2 (PGE-2) levels in the aqueous and pupil diameter in patients undergoing low-pulse energy femtosecond laser-assisted cataract surgery (LCS) without non-steroidal anti-inflammatory (NSAID) pretreatment with either fragmentation or capsulotomy performed first. Prospective, randomized, fellow-eye controlled comparison. This study was undertaken at the Department of Ophthalmology, Medical University of Vienna. The population consisted of 140 eyes of 70 patients with bilateral age-related cataract. Bilateral same-day LCS with either anterior capsulotomy before lens fragmentation (Caps-First) in one eye or vice versa (Frag-First) in a random sequence were performed. Aqueous was tapped 5 minutes after LCS and PGE-2 concentration was analyzed. Pupil diameters were recorded immediately before and after femtosecond laser pretreatment. The main outcome measure was PGE-2 concentrations in picograms/milliliter and pupil diameter in millimeters. Mean PGE-2 concentrations were 42.0 ± 63.7 pg/mL in the Caps-First group versus 71.8 ± 160.7 pg/mL with the Frag-First group (P=.186). Mean pupil diameters before and after pretreatment were 7.6 ± 0.8 mm and 7.6 ± 0.8 mm, respectively (P=.871). Mean PGE-2 concentrations and pupil diameters did not show any significant difference between time points or groups. Low-energy femtosecond laser pretreatment did not increase PGE-2 levels in the absence of NSAID pretreatment. This was independent of whether capsulotomy or fragmentation was performed first. Moreover, no pupillary miosis was observed.

Effect of Pulsed Laser Pretreatment on the Performance of Butt Joints in Laser Welding-Brazing of Titanium/Aluminum Dissimilar Alloys

Effect of Pulsed Laser Pretreatment on the Performance of Butt Joints in Laser Welding-Brazing of Titanium/Aluminum Dissimilar Alloys

Individualized and controlled laser beam pre-treatment process for adhesive bonding of fiber-reinforced plastics. III. Effects of contaminants

Adhesive bonding of plastic components is a well-established process for various applications. Specifically for thermoplastic parts, surface pre-treatment is required to achieve optimum bonding quality. However, automated surface pre-treatment is not established yet. Reasons are missing process monitoring and significant challenges arising from conventional monitoring techniques that hardly identify surface contaminants. In a recent research project, the authors investigated how process monitoring by spectrometry during a laser-based surface pre-treatment might solve this challenge for fiber-reinforced plastics and generic surface contaminants. This article describes experiments conducted on two composite materials with different contaminants. A nanosecond-pulsed UV-laser was used to pretreat a glass-fiber reinforced 2C-polyurethane (GF-PUR) and a glass-fiber reinforced polyamide 6 (GF-PA6). Each composite had coupons contaminated with an industry standard mould release agent or artificial silicate-based dust as well as uncontaminated samples. The samples were laser pretreated and compared to reference coupons that did not receive laser treatment. The samples were analyzed after laser pre-treatment for their free surface energies by the detection of the contact angle and measured for the surface roughness. The bonding improvement due to the laser process was determined by shear strength and peel resistance tests. The results show that UV-laser pre-treatment has an advantageous impact on the bonding strength of GF-PUR and GF-PA6. Combined with a fast spectrometric process monitoring that robustly identifies contaminants during the laser process, an inline process control is feasible.

Intralesional diode laser pretreatment facilitates surgery for orbital venous malformations: initial experience with 23 consecutive patients.

This study aims to evaluate the efficacy and safety of intralesional diode laser pretreatment for facilitating surgery for orbital venous malformations (OVMs). This is a retrospective, non-comparative, interventional cohort involving 23 consecutive OVM patients undergoing intralesional laser pretreatment followed by surgical excision. The main outcome measures included volumetric changes, exophthalmometry, cosmesis, and symptom scores as well as treatment-related adverse events. Following intralesional diode laser, the mean volume dropped significantly from 2366 ± 1887 to 129 ± 119 mm3 (t = 5.716; p < 0.001). After a single treatment session, a mean 90 ± 13% volume shrinkage was achieved in all 23 OVM. The mean Hertel exophthalmometry decreased significantly from 14 ± 3 to 13 ± 1mm (t = 2.515; P < 0.02). The resolution of periocular dyschromasia and swelling were evident in 20 patients (87%). Symptom scores improved significantly from 6.5 ± 1.4 (very intense discomfort or effect on daily living) to 1.2 ± 1.0 (very mild discomfort or effect on daily living; p < 0.001). Short-term bruises and swelling were reported in 20 patients (87%). Intralesional laser pretreatment is effective to facilitate surgery especially for the deep involving orbital venous malformations.

Shear bond strength of metallic brackets bonded to enamel pretreated with Er,Cr:YSGG LASER and CPP-ACP

BackgroundIncreased risk of enamel demineralization during and after orthodontic treatment raises the demand for better preventive measures including combinations of laser, CPP-ACP, and fluoride. The combination of Er,Cr:YSGG laser with CPP-ACP was proved to have a synergetic effect compared to each of them alone. Shear bond strength (SBS) of orthodontic brackets bonded to the enamel surface after being treated with preventive measures is critical. The aim of this study was to compare the SBS and failure mode of metallic brackets bonded to teeth with no pretreatment and pretreated enamel surface, either with Er,Cr:YSGG laser alone or combined with CPP-ACP.MethodsSixty sound extracted human premolar teeth were allocated randomly to 3 groups: In Group 1 (control), teeth were etched and bonded directly; in Group 2, laser pretreatment of the enamel surface was done followed by etching and bonding as in the control group; in Group 3, the enamel surface was lased then CPP-ACP was applied according to the manufacturer instructions, etched and bonded. SBS and Adhesive remnant index (ARI) were evaluated.ResultsNo significant differences were found between the 3 groups neither in the SBS nor in the ARI scores.ConclusionsThe use of combined Er,Cr:YSGG laser with CPP-ACP as a preventive measure before bonding orthodontic brackets does not endanger the bracket’s bonding strength.

Effects of CO2 laser pretreatment conditions on adhesion properties of Cu/Ti films and polyimide substrates

Effects of CO2 laser pretreatment conditions on adhesion properties of Cu/Ti films and polyimide substrates

Modification of the Cu-Zr bronze surface by exposure to powerful UV laser pulses

The laser pre-treatment of Cu-Zr alloy surface for diffusion welding, which is used in the aerospace industry for joining dissimilar materials, has been investigated. The effect of a nanosecond UV laser pulse on the surface of Cu-Zr alloy samples was studied. It was found that at a pulse energy density E ∼ 0.2-1 J/cm2 pre-ablative microscopic effects of mainly thermal nature were observed in the metal, also there were uplifts of material in the irradiated zone. The surface profile of the sample in the irradiated zone corresponds to the energy distribution of the laser beam. Significant deformations occurred in the crystal structure of the surface layer, and an irreversible configuration of the metal surface was created. At E ≥ 1 J/cm2 an optical breakdown with the formation of a plasma torch and with the appearance of a classical laser crater was observed. The arising erosion of the surface prevented registration of this effect. Microanalysis showed that the concentration of zirconium in the surface layer of the metal after exposure decreased.

Influence of Diode Laser for the Treatment of Dentin Hypersensitivity on Microleakage of Cervical Restorations.

Noncarious cervical lesions (NCCLs) are a common clinical finding often linked with dentin hypersensitivity (DH). Aim. The aim of the study was to evaluate the influence of diode laser for the treatment of DH on microleakage of subsequent NCCL restorations. Materials and Methods. Forty-eight extracted human premolars were collected. All teeth received standardized cervical preparation on both the buccal and palatal surfaces and were randomly divided into three groups (n = 16) according to the restorative material used: nanohybrid composite resin (CR), resin-modified glass ionomer (RMGI), and conventional glass ionomer (GIC). The prepared cavities on the palatal surfaces were treated by diode laser using SIROlaser Blue (Sirona Dental Systems, Bensheim, Germany) prior to restoration, while preparations on the buccal surfaces were directly restored. After thermocycling, the teeth were immersed in methylene blue dye for microleakage evaluation under 40x magnification at both occlusal and cervical margins. The Kruskal-Wallis test followed by the Bonferroni tests was conducted to determine inter- and intragroup differences (P < 0.05). Results. All restorative materials tested showed some degree of microleakage with no statistically significantly different scores with or without the use of laser desensitization prior to restorative treatment. Group CR showed the least microleakage, followed by group RMGI, while group GIC showed the highest. Cervical margins showed greater microleakage than the occlusal margins where the difference was statistically significant in the RMGI group without laser pretreatment (P = 0.006) and in both groups CR (P = 0.02) and RMGI (P = 0.006) with the laser pretreatment. Conclusion. Application of diode laser for the treatment of DH prior to the restoration of teeth with NCCL did not affect the microleakage of all the restorative materials tested. All the materials showed some degree of microleakage, which was higher in gingival margins compared to occlusal margins. The resin composite shows the least microleakage among all the tested materials.

Picosecond Laser-Assisted Chemical Mechanical Polishing (CMP): Aiming at the Si-Face of Single-Crystal 6H-SiC Wafer

Silicon carbide (SiC) presents huge application potential in semiconductor devices. However, attributed to its high hardness and stability, there always appears an urgent problem about how to improve the efficiency of chemical mechanical polishing (CMP) of the SiC Si-face. In this study, an effective picosecond laser-assisted CMP method is proposed, which first preprocesses the Si-face with picosecond laser and then carries out CMP. Scanning electron microscopy (SEM), nano scratch tester (NST), and X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface alteration of SiC Si-face by picosecond laser pretreatment (PLP). The results demonstrate that the ripples and polycrystalline layer produced by PLP improve the surface machinability, and the C–O, Si–C–O, and Si–O bonds oxidized by PLP lead to easier removal by CMP. Hence compared with the no laser pretreated (NLP) samples, the material removal rate (MRR) of PLP samples is much higher in the first 45 min of CMP and the surface roughness (Rq) is lower after CMP. The proposed method has certain scientific significance and industrial production guidance for SiC semiconductor device manufacture.

Conductive cotton fabric using laser pre-treatment and electroless plating

This paper presents the fabrication and characterization of laser-treated conductive cotton fabrics by means of copper metallization techniques. The physical properties of the laser-treated knitted samples were examined in terms of thickness, durability, and abrasion impact. Furthermore, the surface topography of the laser-treated substrates was analyzed using a scanning electron microscope (SEM) before and after the coating process and samples demonstrated remarkably uniform deposition of copper metal nanoparticles on the surface of the fabric. An energy dispersing spectroscopy (SEM-EDX) analysis was carried out to determine the elemental composition on the surface of the substrate after the electroless metallization method. The study found that laser-treated samples showed better resistance to wear compared to untreated fabric samples. Since abrasion resistance is key property in electronic textile applications, laser-treated samples could, therefore, be ideal candidates for electronic textile applications. As a result, laser treatment has been shown to be successful in improving the abrasion resistance of conductive textile fabrics.

Development and evaluation of a heparin gel for transdermal delivery via laser-generated micropores.

Aim: Our study investigated the feasibility of transdermal delivery of heparin, an anticoagulant used against venous thromboembolism, as an alternative to intravenous administration. Materials& methods: Skin was pretreated using ablative laser (Precise Laser Epidermal System [P.L.E.A.S.E.®] technology) for enhanced delivery of heparin. In vitro permeation studies using static Franz diffusion cells provided a comparison between delivery from 0.3% w/v heparin-loaded poloxamer gel and solution across untreated and laser-treated dermatomed porcine ear skin.Results: No passive delivery of heparin was observed. Laser-assisted delivery from solution(26.07±1.82μg/cm2) was higher(p<0.05) than delivery from heparin gel (11.28±5.32μg/cm2). However, gel is likely to sustain the delivery over prolonged periods like a maintenance dose via continuous intravenous infusion. Conclusion: Thus, ablative laser pretreatment successfully delivered heparin, establishing the feasibility of delivering hydrophilic macromolecules using the transdermal route.