YAG Laser Irradiation Research Articles

Effect of Nd:YAG Laser Irradiation of the Growth of Oral Biofilm

Background: Oral microbiota comprises a wide variety of microorganisms. The purpose of this study was to evaluate the effects of Nd:YAG laser with a 1064 nm wavelength on the in vitro growth of Candida albicans, Candida glabrata, and Streptococcus mutans clinical strains, as well as their biofilm. The study also aimed to determine whether the parameters recommended for photobiomodulation (PBM) therapy, typically used for tissue wound healing, have any additional antibacterial or antifungal effects. Material and Methods: Single- and dual-species planktonic cell solution and biofilm cultures of Streptococcus mutans, Candida albicans, and Candida glabrata were irradiated using an Nd:YAG laser (LightWalker; Fotona; Slovenia) with a flat-top Genova handpiece. Two test groups were evaluated: Group 1 (G-T1) exposed to low power associated parameters (irradiance 0.5 W/cm2) and Group 2 (G-T2) with higher laser parameters (irradiance 1.75 W/cm2). Group 3 (control) was not exposed to any irradiation. The lasers’ effect was assessed both immediately after irradiation (DLI; Direct Laser Irradiation) and 24 h post-irradiation (24hLI) of the planktonic suspension using a quantitative method (colony-forming units per 1 mL of suspension; CFU/mL), and the results were compared with the control group, in which no laser was applied. The impact of laser irradiation on biofilm biomass was assessed immediately after laser irradiation using the crystal violet method. Results: Nd:YAG laser irradiation with photobiomodulation setting demonstrated an antimicrobial effect with the greatest immediate reduction observed in S. mutans, achieving up to 85.4% reduction at the T2 settings. However, the laser’s effectiveness diminished after 24 h. In single biofilm cultures, the highest reductions were noted for C. albicans and S. mutans at the T2 settings, with C. albicans achieving a 92.6 ± 3.3% reduction and S. mutans reaching a 94.3 ± 5.0% reduction. Overall, the T2 settings resulted in greater microbial reductions compared to T1, particularly in biofilm cultures, although the effectiveness varied depending on the microorganism and culture type. Laser irradiation, assessed immediately after using the crystal violet method, showed the strongest biofilm reduction for Streptococcus mutans in the T2 settings for both single-species and dual-species biofilms, with higher reductions observed in all the microbial samples at the T2 laser parameters (p < 0.05) Conclusion: The Nd:YAG laser using standard parameters typically applied for wound healing and analgesic effects significantly reduced the number of Candida albicans; Candida glabrata; and Streptococcus mutans strains.

Influence of Diode and Nd:YAG laser irradiation on shear bond strength between soft relining material and conventional, thermoplastic, and CAD/CAM denture resins

Influence of Diode and Nd:YAG laser irradiation on shear bond strength between soft relining material and conventional, thermoplastic, and CAD/CAM denture resins

Nd: YAG laser irradiation in the treatment of live pulp preservation in pediatric cariogenic pulpitis.

Dental pulpitis significantly impacts oral function and quality of life. Treatments like direct pulp capping aim to preserve pulp vitality. This study aims to investigate the application value of Nd:YAG laser irradiation in preserving pulp vitality in children with caries-induced pulpitis. This study, conducted from June 2019 to June 2023, included 89 children undergoing pulp vitality preservation treatment for caries-induced pulpitis. The children were divided into two groups using sealed envelopes: 44 in the control group received pulp capping treatment, while the study group received Nd:YAG laser-assisted pulp capping treatment. The efficacy, oral indicators, oral function, changes in root apex diameter and root length, changes in gingival crevicular fluid inflammatory factors, and incidence of complications were compared between the two groups before and 3 months after treatment. The total effective rates were 97.78% in the study group and 95.45% in the control group, with no significant difference between the groups (p> 0.05). Before treatment, there were no differences in gingival index, plaque index, and probing bleeding index between the groups (p> 0.05). After treatment, both groups showed decreased periodontal indexes compared to before treatment, with the study group showing lower values than the control group (p< 0.05). Chewing and biting function scores were similar between the groups before and after treatment (p> 0.05), but both groups showed decreased scores after treatment (p< 0.05). The study group had a higher percentage decrease in root apex diameter and a greater increase in root length compared to the control group (p< 0.05). During treatment, one case of tooth discoloration occurred in the study group (2.27%), while the control group had two cases of tooth discoloration and one case of secondary caries, resulting in a complication rate of 6.67%. There was no significant difference in the incidence of complications between the groups (p> 0.05). Nd:YAG laser irradiation effectively preserves pulp vitality in children with caries-induced pulpitis, improving periodontal health, reducing root apex diameter, and increasing root length with high safety.

Effect of laser power density on formation of oxide particles during ablation of metallic bismuth in atmospheric air

Purposeful synthesis of bismuth oxide nanoparticles (NPs) of various crystal modifications is important for biomedicine, photocatalysis and other applications. In this work, pulsed laser ablation of a metallic Bi target in atmospheric air is used to obtain β-Bi2O3 NPs. The effect of the Nd:YAG laser radiation power density (1064 nm, 7 ns) in the range of 0.1–1.2 GW/cm2 on the features of formation of NPs under nonequilibrium conditions is studied, for which the spectra of laser-induced plasma are recorded and analyzed, the plasma composition is determined, and the temperature of the plasma plume is estimated. The NPs are comprehensively characterized using TEM, XRD, FTIR, Raman, and UV–Vis spectroscopies, and electrophoretic light scattering, which make it possible to determine their morphology, crystal structure, chemical composition, and optical properties. The photocatalytic activity of the resulting nanopowders in the Rhodamine B dye decomposition reaction is assessed.

Effect of Er:YAG laser surface treatment on surface properties and shear-bond strength of resin-cement to three translucent zirconia: an in-vitro study

Achieving optimal bonding to translucent zirconia poses certain challenges as there is no consensus on ideal surface treatment method. Therefore, the aim of present investigation is to evaluate effect of Er:YAG laser treatment on wettability, surface roughness and shear-bond strength of three Yttrium oxide-stabilized zirconium-oxide polycrystal translucent zirconias. 120 specimens (n = 40/zirconia type) were prepared from three commercially-available translucent zirconias (Dentsply Sirona, USA); Translucent, High-Translucent and Ultra-Translucent zirconia. Specimens were sub-divided (n = 20/surface-treatment) into control and Er:YAG laser surface-treated groups. Regarding water wettability test; goniometer was used to measure contact angle before and after laser treatment. Surface roughness was measured using atomic force microscope. For shear-bond strength (SBS) test; the control group was sandblasted. All resin-bonded zirconia specimens were thermocycled for 5000 cycle and subjected to shear force using universal testing machine with 0.5 mm/min crosshead-speed. Results were statistically analyzed using two-way-analysis-of- variance (p ≤ 0.05). There was significant decrease in average contact angles (p-value < 0.001) in all zirconia groups after laser treatment. For roughness test; insignificant difference in average Ra in Translucent zirconia group. However, significant increase in mean Ra was revealed after laser treatment for High and Ultra-Translucent zirconias. For SBS test, results revealed insignificant difference in average bond strength after laser treatment in Translucent and High-translucent zirconia groups. Significant increase in mean bond strength of Ultra-Translucent zirconia was recorded. Er: YAG laser treatment significantly affected surface properties and shear-bond strength of Ultra-Translucent zirconia. Er:YAG laser irradiation may be a promising zirconia surface treatment method.Graphical

Effect Of Air-Abrasion And Er:Yag Laser On The Bond Strength Between The Metal Housing Of An Overdenture Attachment System And The Hard Relining Material

Objective. This study investigated the effect of air-abrasion and erbium:yttrium-aluminum-garnet (Er:YAG) laser treatments on push-out bond strength (PBS) between hard relining material and metal housing of an overdenture attachment system. Material and Methods. A total of 36 metal housings were randomly divided into 3 subgroups according to surface pretreatments (n=12): Control (no surface treatment; C), air-abrasion (A), and Er:YAG laser (L). Surface roughness (Ra) of specimens was determined using a profilometer. One additional specimen per group was evaluated by scanning electron microscopy (SEM). The hard relining material was bonded to metal housings, and a PBS test was performed using a universal testing machine. Data were statistically analyzed using 1-way analysis of variance (ANOVA), Tukey’s honestly significant difference (HSD), and Tamhane’s T2 tests (α=.05). Results. C and L groups showed the lowest and highest Ra values, respectively. The mean Ra of the A group was statistically different from the mean values of the C and L groups (P&amp;lt;.001). The L group showed higher PBS values than the C group (P&amp;lt;.05), whereas the A group exhibited statistically similar PBS values to both C and L groups (P&amp;gt;.05). Conclusions. Air-abrasion did not significantly increase the bond strength between the metal housing and hard relining material. Er:YAG laser irradiation noticeably improved the PBS but caused surface microcracks.

Effect of Er:YAG laser on debonding zirconia and lithium disilicate crowns bonded with 2- and 1-bottle adhesive resin cements.

Erbium-doped yttrium-aluminum-garnet (Er:YAG) laser debonding of zirconia and lithium disilicate restorations is increasingly used for a range of clinical applications. Using rotary instruments to remove such restorations for any purpose has proven to be challenging. Erbium laser has been reported to be a conservative method for removing ceramic restorations. There is little data in the literature about the effect of adhesive resin cement type on the debonding time of the ceramic restoration using the Er:YAG laser. To evaluate and compare the time required for the Er:YAG laser to debond zirconia and lithium disilicate crowns bonded with a 2- and 1-bottle adhesive resin cement systems. Forty extracted premolar teeth were prepared and scanned for milled 40 CAD/CAM crowns. Teeth were randomly assigned into groups (n = 10 per group): 3 mol% yttria-partially stabilized zirconia crowns 3Y-PSZ (G1a) bonded with Panavia™ V5 (2-bottle adhesive resin cement), Zirconia 3Y-PSZ crowns (G1b) bonded with RelyX™ Ultimate (1-bottle adhesive resin cement), and for the lithium disilicate crowns bonded with the two types of cements (G2a, G2b). Each specimen was irradiated with an Er:YAG laser at 335 mJ, 15 Hz, 5.0 W, and 50-ms pulse duration (super short pulse mode). The irradiation time required for crowns to be successfully debonded was recorded for each specimen. Data were statistically analyzed using ANOVA and Tukey HSD post-hoc test (p < 0.05), at the 95 percent level of confidence. The intaglio surface of the debonded crown was analyzed using scanning electron microscopy (SEM). The mean ± standard deviation times needed for crown debonding were 5.75 ± 2.00 min for the G1a group, 4.79 ± 1.20 min for group G1b, 1.69 ± 0.49 min for group G2a, and 1.12 ± 0.17 for group G2b. There was no statistically significant difference in debonding time between the 2- and 1- bottle adhesive resin cement within the groups G1a and b (p = 0.2914), or between groups G2a b (p = 0.7116). A statistically significant difference (p < 0.05) was found between groups G1a and G2a and b and between groups G1b and G2a and b were SEM analysis showed no changes in the microstructure of the ceramic surface after Er:YAG laser irradiation. Zirconia and lithium disilicate restorations can be debonded using Er:YAG lasers in a safe and efficient manner. There is no significant difference in the debonding time between the 2- and 1- bottle adhesive resin cement systems used in this study. Retrieving zirconia and lithium disilicate ceramics can be a challenging process when using diamond rotary instruments. ER:YAG lasers may efficiently debond these ceramics from the tooth structure, independent of the bonding process used for bonding them.

OUR EXPERIENCE IN SURGICAL TREATMENT OF MUCOSAL HYPERTROPHY OF TORI TUBARII

Puprose. Evaluation of the effectiveness of surgical treatment of mucous hypertrophy of tori tubarii by submucosal tissue destruction using Ho:YAG laser radiation. Materials and methods. The study involved 48 adult patients with symptoms of Eustachian tube dysfunction. The patency of the auditory tube was assessed by standard tests, the ETDQ 7 questionnaire, tympanometry, pure tone threshold audiometry, and endoscopic video recording of the results were performed. Surgical intervention was carried out by forming under the influence of pulsed radiation from a Ho:YAG laser with a frequency of 10 Hz and a pulse energy of 2 J, 4–6 tunnels with a depth of 5–7 mm in the hypertrophied mucous membrane of the torui tubarii along the posteromedial surface and 2 tunnels up to 3 mm up and down from the pharyngeal mouth of the auditory tube. The control periods after surgery were 1, 3 and 6 months. Results. A significant improvement in the results of the auditory tube according to ETDQ-7 was noted by 3 months after surgery in 71% of patients and in 84% by 6 months. By 6 months after surgery, type C tympanometry and clinically significant conductive hearing loss persisted in 8 and 5% of patients, respectively. The subjective feeling of fully performing the Valsalva test improved in 58% after 3 months and in 82% by the 6th month, and the Toynbee test in 42% and 64% in the 3rd and 6th months, respectively. In 16% of patients, despite a visual decrease in mucosal hypertrophy during endoscopic examination, signs of dysfunction remained according to ETDQ 7. There were no complications after surgical treatment during 6 months of observation. Conclusion. The use of endoscopic diagnosis of the nasopharynx in patients with signs of dysfunction of the auditory tubes in combination with functional tests and the ETDQ-7 questionnaire allows to determine the indications for the surgical treatment of hypertrophy of the mucous membrane of the tori tubarii using the Ho:YAG laser, the effectiveness of which in our study was 84%.

Reduced A–B super exchange interaction in zirconium doped cobalt ferrite due to laser irradiation

The impact of Nd:YAG laser irradiation and the addition of zirconium ions (Zr4+) on the physical properties of CoFe2O4 spinel nano-ferrites has been studied. The co-precipitation method was used to synthesize the samples. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were employed to examine the structure and morphology. The decrease in the Curie temperature Tc is due to the laser irradiation and the increase in the Zr content of the sample. This decline in Tc is a result of an increase in the canting of the spins, leading to a change in the thermal energy needed for compensate the spin alignment. The difference in the Tc between the non irradiated and the irradiated samples is about 7%, 43% and 34% for CoFe2O4, Co1.1Zr0.1Fe1.8O4, and Co1.3Zr0.3Fe1.4O4, respectively. The decrease in the coercivity of the laser irradiated sample is due to a reduction in the magnetic anisotropy and an altered distribution of the cations (Co2+, Fe3+, Zr4+). The observed trend indicates that laser irradiation, and Zr substitution, can be used to modify the magnetic hardness of the samples. The low coercivity of irradiated Co1.1Zr0.1Fe1.8O4 makes it suitable for a range of applications. The high-frequency response of the Co1+xZrxFe2–2xO4 NPs shows that they can operate within the frequency range of 7.5 GHz–11.56 GHz.

Dentin Collagen versus Er:YAG Laser as Surface Biomodifiers for Intact Root Slices Simulating Delayed Replanted Roots.

Objective: To evaluate effects of dentin collagen versus Er:YAG laser application through enhancing human periodontal ligament fibroblast (PDLF) cells to attach to intact root surfaces imitating delayed replanted roots. Background Data: Accidental traumatic injuries with teeth avulsion are managed by replantation. Root resorption, poor conditioning, and non-viable fibroblasts are factors responsible for failure. Methods: Thirty six human healthy single-rooted premolars were collected. Six teeth were used for PDLF, six teeth used for dentin collagen, whereas the remaining 24 teeth (48 root slices) were used for PDLF cell density and morphology. Each root was soaked in 5.25% NaOCl. Three groups (n = 16 slices/each) were planned as follows: I: Control (untreated); II: dentin collagen application; III: Er:YAG laser irradiation (4 mm distance, 40 mJ/pulse, under coolant). Following incubation, cell density and morphology of PDLF were investigated under SEM. Statistical analysis was performed using analysis of variance with Scheffé's test, and p < 0.05 was considered significant. Results: All groups showed increased cultured PDLF following incubation. Regarding cell density, attached PDLFs were significantly lower in untreated controls (36.5 ± 6.36) (p < 0.00001 i.e., <0.05) in negative empty and/or light cellular areas, compared with dentin collagen (65 ± 6) and laser-irradiated (66.75 ± 5.77) groups that did not show significant differences (p = 0.940 i.e., >0.05) and showed intermediate and/or heavy cellular areas. Regarding cell morphology, controls showed round and/or oval appearance with less lamellipodia, whereas dentin collagen and laser groups showed flat morphology with cytoplasmic processes. Conclusions: Both dentin collagen and Er:YAG laser showed comparable effectiveness as biomodification tools with good biocompatibility for human PDLF cell attachment on intact root slices imitating delayed replantation. Dentin collagen as a natural bioactive material is considered an alternative to Er:YAG laser to enhance the regenerative effects.

Tunable optical parametric oscillator based on ZnGeP2 crystal for greenhouse gas remote sensing systems

This work is devoted to the development of a compact source of coherent radiation with frequency-energy characteristics and a spectral generation range that allows remote determination of background concentrations of greenhouse gases in the atmosphere. The aim of this work was to create a frequency parametric converter based on ZGP, pumped by Ho:YAG laser radiation. For use as a source in a mobile lidar for remote determination of the concentration of greenhouse gases in the atmosphere. In the course of the research, a layout of an Optical parametric oscillator OPO based on a ZGP crystal with Ho:YAG laser radiation pumping was developed. The system’s continuous failure-free operation time was 1.5 h at a pulse repetition rate of 10 kHz and a pulse energy of the generated radiation of 0.08 mJ. The tuning range of the OPO was from 3.3 to 5 μm when using a Lyot filter. The losses from the average generation power when the Lyot filter was introduced into the resonator were 30%. At the same time, it was possible to achieve a linewidth of the generated radiation of 0.7 nm. The divergence of the generated radiation did not exceed 1.5 mrad.The absorption spectrum of gases CO2, CH4, N2O, CO in a gas cell was simulated for the entire generation range of the ZnGeP2-based OPO. As a result of the simulation, the most intense absorption lines of gases CO2, CH4, N2O, CO in the OPO tuning range were revealed, the central wavelengths of the absorption lines and their spectral width were determined.

Morphological and size tuning of biogenic Ag and Au nanoparticles induced by laser irradiation

Since size and shape of the metal nanoparticles (NPs) determine its physical and chemical properties, such could be relevant for specific applications; it is critical to have adequate control over such features. In this work, a facile bottom-up, bio-inspired synthetic route for noble metal nanoparticles (NPs) preparation is presented. Specifically, Ag and Au monometallic nanoparticles were synthesized by bio-reduction with Citrus paradisi (Grapefruit) aqueous extract. Besides, conventional chemical reduction synthesis using NaBH4 and PVP as capping agent was also performed for comparison purposes. Characterization accomplished by UV–vis spectroscopy and electron microscopy over the synthesized nanoparticles shown that, although that unimodal (in the case of Ag NPs) or almost unimodal (Au NPs) size distributions were obtained, thanks to stabilizing effect of the ligand acting-biomolecules present in the extract; and the narrower size distribution in comparison with the conventional chemical synthesis route were observed, several morphologies were found for both metals. In order to modify such features, the obtained noble metal NPs were submitted to pulsed (30 ps, 10 mJ) Nd:YAG laser irradiation process; after that, the spherical shape seems to be the predominant morphology in both metal nanoparticles, whereas the population of particles smaller than 15 nm became increases considerably.

Effect of chitosan and CMCS on dentin after Er:YAG laser irradiation: shear bond strength and surface morphology analysis.

The aim of the present study was to evaluate the effect of chitosan and carboxymethyl chitosan (CMCS) on dentin surface morphology and bonding strength after irradiation of Er:YAG laser. Eighty-four laser-irradiated dentin samples were randomly distributed into three groups (n = 28/group) according to different surface conditioning process: deionized water for 60s; 1wt% chitosan for 60s; or 1wt% CMCS for 60s. Two specimens from each group were subjected to TEM analysis to confirm the presence of extrafibrillar demineralization on dentin fibrils. Two specimens from each group were subjected to morphological analysis by SEM. Seventy-two specimens (n = 24/group) were prepared, with a composite resin cone adhered to the dentin surface, and were then randomly assigned to one of two aging processes: storage in deionized water for 24h or a thermocycling stimulation. The shear bond strength of laser-irradiated dentin to the resin composite was determined by a universal testing machine. Data acquired in the shear bond strength test was analyzed by one-way ANOVA with the Tukey honestly significant difference post hoc test and Independent Samples t-test (α = 0.05). CMCS group presented demineralized zone and a relatively smooth dentin surface morphology. CMCS group had significantly higher SBS value (6.08 ± 2.12) without aging (p < 0.05). After thermal cycling, both chitosan (5.26 ± 2.30) and CMCS group (5.82 ± 1.90) presented higher bonding strength compared to control group (3.19 ± 1.32) (p < 0.05). Chitosan and CMCS group preserved the bonding strength after aging process (p > 0.05). CMCS has the potential to be applied in conjunction with Er:YAG laser in cavity preparation and resin restoration.

The Influence of Neodymium-Doped Yttrium Aluminum Garnet Laser Pulse Repetition Rate on Cytokine Secretion from Peripheral Blood Mononuclear Cells in Vitro

Objective: Biological effects of infrared laser energy at various exposure parameters have been characterized in previous in vitro and animal studies. However, the impact of pulse repetition rate (PRR) has not been evaluated in this context. The purpose of this investigation was to assess the influence of PRR on cytokine secretion from peripheral blood mononuclear cells (PBMCs) subjected to pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser energy. Materials and Methods: Rat PBMCs were cultured in vitro then stimulated using a lipopolysaccharide concentration of 0 or 100 ng/ml. Cultures received Nd:YAG laser radiation (1064 nm, 5 W, 30 s) at PRR of 0 (untreated controls), 20, 30, 40, or 60 Hz. Concentrations of tumor necrosis factor-α (TNF-α), macrophage inflammatory protein (MIP)-1α, macrophage inflammatory protein (MIP)-2, monocyte chemoattractant protein-1 (MCP-1), interferon-gamma-induced protein (IP)-10, interleukin (IL)-6, and IL-10 were recorded using a magnetic microsphere immunoassay. The main effects of PRR and LPS stimulation on cytokine concentrations, and the interaction between PRR and LPS stimulation, were assessed using two-way analysis of variance. Bonferroni post hoc tests were used to identify pairwise differences between groups. Results: The main effect of PRR was statistically significant for MIP-1α (P = 0.018), TNF-α (P = 0.025), MCP-1 (P &lt; 0.001), MIP-2 (P = 0.013), and IL-6 (P = 0.031). Five of six pro-inflammatory cytokines exhibited significantly lower mean concentrations in laser-exposed compared with control cultures at one or more PRR. However, no statistically significant differences were found between PRR groups. Conclusions: Under the described conditions, statistically significant differences in cytokine secretion were observed between laser-exposed and control cultures, consistent with prior reports. However, PRR appears to be an irrelevant factor in immunomodulation of PBMCs.

Effects of Two Remineralizing Agents in Combination with Er:YAG and CO2 Laser Irradiation on Microhardness of Demineralized Enamel: A Preliminary In Vitro Study.

Objectives: This study assessed the effects of two remineralizing agents namely MI Paste Plus containing casein phosphopeptide amorphous calcium phosphate fluoride (CPP-ACFP) and Remin Pro containing hydroxyapatite, fluoride and xylitol (HFX) with/without erbium-doped yttrium aluminium garnet (Er:YAG) and CO2 laser irradiation on demineralized enamel microhardness. Materials and Methods: In this in vitro study, 70 sound human premolars were mesiodistally sectioned, demineralized at a pH of 4.6 for 8 hours, and randomly divided into 7 remineralization groups (n=10): of (I) MI Paste Plus (CPP-ACFP), (II) Remin Pro (HFX), (III) MI Paste Plus+CO2 laser (0.7 W power, 50 Hz), (IV) Remin Pro+CO2 laser, (V) MI Paste Plus+Er:YAG laser (1 W power, 10 Hz), (VI) Remin Pro+Er:YAG laser, and (VII) negative control. The Vickers hardness number of specimens was then measured. The groups were compared by one-way ANOVA and Tukey's test (α=0.05). Results: The mean microhardness was 319.8±49.9, 325.3±44.6, 359.4±35.7, 296.4±33.7, 319.9±58.1, 358.9±28.4, and 240.0±41.6 kg/mm2 in groups 1 to 7, respectively. The difference in microhardness was significant among the groups (P<0.0001). Pairwise comparisons revealed significant differences in microhardness between all groups (P≤0.03) except between groups 1 and 2, 1 and 5, 2 and 5, and 3 and 6 (P>0.05). Conclusion: Both Remin Pro (containing HFX) and MI Paste Plus (containing CPP-ACFP) can cause enamel remineralization. MI Paste Plus+CO2 laser irradiation and Remin Pro+Er:YAG laser irradiation were significantly more effective than the application of each remineralizing agent alone.

Effects of Nd:YAG laser irradiation at different energy densities on dentin bond durability under simulated pulpal pressure.

To evaluate the effects of Nd:YAG laser irradiation on the microstructures of dentin surfaces and the long-term bond strength of dentin under simulated pulpal pressure. Under simulated pulp pressure, 30 freshly extracted caries-free third molars were cut into 2-mm-thick dentin samples and then divided into five groups: the control and laser groups (93.3J/cm2; 124.4J/cm2; 155.5J/cm2; 186.6J/cm2). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and Vickers hardness were used to analyze the surface morphology, composition, and mechanical properties of the dentin before and after laser irradiation. Another 80 caries-free third molars were removed and treated as described above, and the resin was bonded to the dentin surface with Single Bond Universal (SBU) adhesive in self-etch mode to make stick specimens. Microtensile bond strength (µTBS), confocal laser scanning microscopy (CLSM), and interfacial silver nanoleakage tests before and after 10,000 times thermocycling were then performed to analyze the bonding properties and interfacial durability of each group. SEM observations revealed that the surfaces of all laser group specimens were rough with open dentin tubules. Laser irradiation altered the surface composition of dentin while removing some collagen fibers but did not affect its surface hardness or crystallographic characteristics. Furthermore, laser irradiation with an energy density of 124.4J/cm2 significantly promoted the immediate and aging bond strengths and reduced nanoleakage compared to those of the control group. Under simulated pulp pressure, Nd:YAG laser pretreatment altered the chemical composition of dentin and improved the immediate and long-term bond strength. This study investigated the optimal parameters for Nd:YAG laser pretreatment of dentin, which has potential as a clinical method to strengthen bonding.

Correction to: Nd: YAG laser irradiation consequences on calcium and magnesium in human dental tissues

Correction to: Nd: YAG laser irradiation consequences on calcium and magnesium in human dental tissues

Effects of Nd: YAG LASER irradiation and O2 plasma on the adhesive performance of poly-ether-ether-ketone (PEEK)

PurposeTo evaluate the effects of neodymium-doped yttrium aluminum garnet (Nd: YAG) LASER irradiation and oxygen (O2) plasma on the adhesive performance of polyether ether ketone (PEEK) and resin adhesive. MethodsNd: YAG LASERs of varying powers and O2 plasma for different durations were used to modify PEEK. A total of 168 PEEK specimens were randomly divided into seven groups (n = 24/group): (A) Control group: untreated PEEK, (B) L0.75 group: PEEK modified with 0.75 W Nd: YAG LASER, (C) L1 group: PEEK modified with 1.0 W Nd: YAG LASER, (D) L1.25 group: PEEK modified with 1.25 W Nd: YAG LASER, (E) P15 group: PEEK modified with 15 min of O2 plasma, (F) P25 group: PEEK modified with 25 min of O2 plasma, and (G) P35 group: PEEK modified with 35 min of O2 plasma. The surface characteristics of the materials were comprehensively analyzed using a scanning electron microscope (SEM), profilometer, energy-dispersive spectrometer (EDS), and contact angle tester. The adhesive specimens were bonded with Variolink N resin adhesive in all groups and each group was further divided into two subgroups (n = 12/group): (a) water storage for 56 h at 37 °C and (b) thermal cycling 5000 times. Shear bond strength (SBS) was tested using a universal testing machine, and the fracture modes were observed using an automated chemiluminescence analysis system to assess the effects of Nd: YAG LASER and O2 plasma on the bond strength of PEEK to resin adhesive. ResultsBoth Nd: YAG LASER and O2 plasma treatments altered the surface characteristics of PEEK and significantly increased the SBS between PEEK and Variolink N resin adhesive. The L0.75 group (Nd: YAG LASER) and the P35 group (O2 plasma) achieved the highest SBS, respectively. Furthermore, the SBS of the L0.75 group was higher than that of the P35 group. Following thermal cycling, SBS values decreased compared to the water storage subgroups. The fracture modes of the specimens in each group were predominantly interfacial and mixed, with no cohesive fractures observed. ConclusionsNd: YAG LASER irradiation and O2 plasma treatments can improve the SBS between PEEK and resin adhesive, with the 0.75 W Nd: YAG LASER being the preferred treatment method.

An experimental investigation of micro-channels on transparent material using Nd: YAG laser transmission technique

Among the fastest growing basic materials, polymers have good strength-to-weight ratios, easy to shape, relatively economical, and recyclable which enabled it to become substitutes for metals and alloys in the fields of medical, automobile, aerospace, electronics, thermal and chemical engineering. But a thick transparent PMMA plate creates deep sub-surface cracks due to the burning and charring of polymeric chains, making the operation with Nd: YAG laser radiation extremely difficult. In the current research, a 75 W nanosecond pulsed Nd: YAG laser system is applied to make micro-channel with adequate depth on a thick transparent PMMA plate by using transmission cutting technique. The input process factors considered are pulse width, laser power, cutting speed, and pulse frequency in order to examine the quality characteristics, the depth of cut and heat affected zone (HAZ) in and around the formed micro-channel. To design the experiment of laser transmission channelling of thick PMMA plate of 11 mm, a central composite design (CCD) methodology is used. Due to open-air laser processing, undesirable laser processing effects have been minimised, resulting in a finer and cleaner micro-channel structure with adequate depth of cut, kerf width and minimal Heat Affected Zone (HAZ) width with laser power of around 9 W, pulse frequency of around 33 kHz and cutting speed of 2 mm/sec.

Er:YAG laser suppresses pro-inflammatory cytokines expression and inflammasome in human periodontal ligament fibroblasts with Porphyromonas gingivalis-lipopolysaccharide stimulation

Background/purposePeriodontitis is an inflammatory condition of the tooth-supporting structures triggered by the host's immune response towards the bacterial deposits around the teeth. It is well acknowledged that pro-inflammatory interleukin (IL)-6, IL-8, MCP-1 as well as the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, are the key modulators in the activation of this response. Erbium-doped yttrium-aluminium-garnet (Er:YAG) laser, a solid-state crystal laser have been commonly used in the treatment of periodontal diseases. However, little is understood about the molecular mechanism of the Er:YAG laser, especially in targeting the host immune response brought on by periodontal pathogens. Hence, the current study focused on the protective effects of Er:YAG laser on periodontitis in-vitro in terms of pro-inflammatory cytokines, chemokines and NLRP3 inflammasome expressions. Materials and methodsHuman periodontal ligament fibroblast (PDLFs) were first stimulated with lipopolysaccharides (LPS) from P. gingivalis (Pg-LPS) to simulate periodontitis. Cells were then irradiated with Er:YAG laser of ascending energy densities (3.6–6.3 J/cm2), followed by cell proliferation and wound healing assay. Next, the effects of Er:YAG laser on the expressions of IL-6, IL-8, MCP-1, NLRP3, and cleaved GSDMD were examined. ResultsPg-LPS was found to reduce cell's proliferation rate and wound healing ability in PDLFs and these were rescued by Er:YAG laser irradiation. In addition, LPS stimuli resulted in a marked upregulation in the secretion of IL-6, IL-8 and MCP-1 as well as the mRNA and protein expression of NLRP3 and cleaved-GSDMD protein whereas Er:YAG laser suppressed the elicited phenomena. ConclusionTo our knowledge, this is the first study to look into the laser's implication on the NLRP3 inflammasome in periodontitis models. Our study reveals a crucial role of Er:YAG laser in ameliorating periodontitis in-vitro through the modulation of IL-6, IL-8, MCP-1 and the NLRP3 inflammasome and highlights that the control of the NLRP3 inflammasome may become a potential approach for periodontitis.