Search Results (801)

Background: This prospective observational study was conducted to systematically assess immediate changes occurring (within one hour) in corneal endothelial cell morphology and anterior segment parameters following Nd:YAG laser posterior capsulotomy in pseudophakic patients and to analyze the correlation between these changes and laser energy parameters. Methods: A single-arm, within-subject pre–post design was employed to evaluate corneal endothelial morphology (cell density, count, area, coefficient of variation and hexagonal percentage) and anterior chamber parameters (depth, angle, volume) before and one hour after the procedure using specular microscopy and Pentacam analysis. Patient demographics (age), clinical parameters (best corrected visual acuity and intraocular pressure), postoperative-YAG laser interval, and laser energy parameters (energy per shot, pulse count, and total applied energy) were also documented. Results: Thirty-two pseudophakic patients (mean age 56.3 ± 19.2 years) underwent Nd:YAG laser posterior capsulotomy with mean energy per shot of 3.15 ± 1.07 mJ and pulse count of 34.3 ± 20.4. Specular microscopy revealed significant post-procedural decreases in endothelial cell density (2184.05 to 2057.2 cells/mm²; p = 0.006) and increases in average cell area (529.25 ± 242.72 to 587.75 ± 281.09 µm²; p = 0.004) and minimum cell area (199.3 ± 170.62 to 248.35 ± 202.7 µm²; p = 0.035). Corneal topography also decreased significantly in the anterior chamber angle (40.07 ± 10.34 to 35.42 ± 6.78 degrees; p = 0.048), with positive correlations between energy per shot and endothelial cell density (r = 0.557; p = 0.011) and average cell area (r = 0.544; p = 0.013). Conclusions: This study demonstrates that Nd:YAG laser capsulotomy causes immediate, energy-dependent alterations in corneal endothelial density and anterior chamber parameters within one hour post-procedurally. The identification of energy per shot as a key determinant represents a preliminary observation for optimizing laser parameters and reducing potential complications in pseudophakic patients. Full article

With the advent of novel scintillators featuring higher atomic numbers and enhanced radiation hardness, these materials exhibit potential applications under high-dose-rate irradiation. In this work, we systematically compared the photon output characteristics of ten mainstream or emerging inorganic scintillators under high-dose-rate irradiation with low-energy (0.1–1.7 MeV) electrons or protons. Initially, under electron irradiation among ~0.1 to ~50 rad/s, responses exhibited saturation trends to varying degrees, with their variations conforming to the saturation model proposed. However, under proton irradiation among ~5 rad/s to ~150 rad/s, responses exhibited sigmoidal trends due to competition between radiation-induced defects and luminescence centers. Through dynamic derivation of carriers and them, a triple-balance model that demonstrated close agreement with such variations was established. Subsequently, energy-dependent responses under proton irradiation exhibited marked nonlinearity, which were well fitted by Birks’ law, confirming the validity of our measurements. In contrast, electron-induced responses remained nearly linear with increasing energy. Then, after high-dose-rate and prolonged irradiation, BGO revealed highest response degradation, while YAG(Ce) demonstrated most radiation-damage resistance. Moreover, Ce-doped scintillators displayed higher afterglow levels after prolonged irradiation, particularly for YAG(Ce). In summary, these experimental analyses can provide critical guidance for material selection and effective calibration of scintillator detectors operating under high-dose-rate radiation from charged particles. Full article

The durability of bonding between the denture base and reline materials plays a critical role in the long-term success of removable prostheses. This study aimed to compare the bond strength of denture base resins fabricated by heat-polymerization, CAD-CAM milling, and 3D printing techniques after thermocycling and different surface treatments. A total of 216 specimens (10 × 10 × 20 mm) were prepared from three base materials and subjected to surface treatment via no treatment (control), alumina air abrasion, or an Er/YAG laser. Two reline materials (hard and soft) were applied according to manufacturers’ instructions. All samples underwent 5000 thermal cycles and were tested using a tensile bond strength test. SEM analysis was performed to evaluate failure modes. The highest bond strength was observed in the milled resin group combined with alumina air abrasion and the hard reline material, reaching up to 12.41 MPa. Statistically significant effects were found for the material type, surface treatment, and reline material (p < 0.001). The results indicate that material properties, surface preparation, and reline type critically influence bond performance. Milled PMMA bases and hard relining agents, particularly when combined with air abrasion, offer superior bonding outcomes. Full article

Background/Objectives: The laser beam absorption and thermal relaxation time (TRT) in oral tissues are key to optimizing treatment parameters. The aim of this study is to (1) evaluate, in an ex vivo study, the percentage of attenuation and transmittance of each wavelength as a function of tissue thickness; (2) determine the global absorption coefficient, α, of pig gingival tissue for the most commonly used wavelengths in dentistry; (3) calculate the thermal relaxation time (TRT) of oral tissue for these wavelengths; and (4) determine their corresponding penetration depths. Methods: We measured the transmission of different laser wavelengths through pig oral gingival tissues (Mandibular labial gingiva). We placed each tissue sample between two glass slides with minimal light attenuation. The input and output powers were measured after irradiating the tissue at different specific wavelengths: 450 nm, 480 nm, 532 nm, 632 nm, 810 nm, 940 and 980 nm, 1064 nm, 1341, 2780 nm and 2940 nm. After calculating the transmittance values, we plotted transmittance curves for each wavelength. Using the Beer–Lambert law, we then calculated the absorption coefficient (α) of each wavelength in the oral gingival tissue. Absorption coefficients were then used to calculate the TRT and penetration depth for each wavelength. Results: Among the tested wavelengths, 810 nm exhibited the lowest absorption in ex vivo porcine gingival tissue (α = 9.60 cm⁻¹). The 450 nm blue laser showed moderate absorption (α = 26.8 cm⁻¹), while the Er:YAG laser at 2940 nm demonstrated the highest absorption (α = 144.8 cm⁻¹). We ranked the wavelengths from most absorbed to least absorbed by porcine oral gingival mucosa as follows: 2940 nm > 2780 nm > 450 nm > 480 nm > 532 nm > 1341 nm > 632 nm > 940 nm > 980 nm > 1064 nm > 810 nm. Conclusions: Absorption and the TRT vary significantly across wavelengths. Erbium lasers are characterized by the highest absorption and minimal light penetration. Infrared diodes, particularly the 810 nm wavelength, showed the lowest absorption and deepest tissue penetration and exhibited the highest thermal relaxation time. The 480 nm laser demonstrated greater absorption by porcine gingival tissue compared to the 532 nm laser. These findings provide evidence-based guidance for wavelength selection in dental treatments and photobiomodulation, enabling improved precision, safety, and therapeutic efficacy in clinical practice. Full article

This study investigates two-sided pulsed-periodic laser welding of three-layer metal–polymer–metal (MPM) composite sheets composed of galvanized dual-phase steel (DPK 30/50+ZE) as outer layers and a polypropylene–polyethylene (PP–PE) core. Welding was performed using a Rofin StarWeld Performance pulsed Nd:YAG laser with controlled parameters: pulse energy (30–32 J), duration (6–8 ms), and frequency (up to 1 Hz). High-quality welds were achieved with penetration depths reaching 70% of the outer metal layer thickness and minimal defects. Microscopic analysis revealed distinct fusion and heat-affected zones (HAZ) with no evidence of cracks or porosity, indicating stable thermal conditions. Mechanical testing showed that the welded joints attained a tensile strength of approximately 470 MPa, about 80% of the ultimate tensile strength of the base metal, with an average elongation of 0.6 mm. These results confirm the structural integrity of the joints. The observed weld morphology and microstructural features suggest that thermal conditions during welding significantly affect joint quality and HAZ formation. The study demonstrates that strong, defect-free joints can be produced using basic beam-shaping optics and outlines a pathway for further improvement through the integration of diffractive optical elements (DOEs) to enhance spatial-energy control in multilayer structures. Full article

Marking techniques are employed to guarantee the identification and traceability of biomedical materials. This study investigated the impact of laser and mechanical marking processes on the tribological performance of ISO 5832-1 austenitic stainless steel (SS), specifically examining corrosion resistance, the coefficient of friction, and wear volume in ball-cratering wear tests. The laser marking was performed using a nanosecond Q-switched Nd:YAG laser. Cytotoxicity tests assessed the biocompatibility of the biomaterial. Non-marked surfaces were also evaluated for comparison. A phosphate-buffered saline solution (PBS) served as both the lubricant and corrosion medium. The surface finishing was analyzed using optical microscopy and scanning electron microscopy coupled with a field-emission gun (SEM-FEG), combined with an energy-dispersive X-ray spectrometer. The oxide film was examined through X-ray photoelectron spectroscopy (XPS). Wear tests lasted 10 min, with PBS drops applied every 10 s at 75 rpm; solid balls of AISI 316L stainless steel (SS) and polypropylene (PP), each 1 inch in diameter, were used as counter-bodies. Corrosion resistance was assessed using electrochemical methods. Results showed variations in roughness and microstructure due to laser marking. The tribological behaviour was influenced by the type of marking process, and the wear amount depended on the normal force and ball nature. None of the samples was considered cytotoxic, although laser-marked surfaces exhibited the lowest cellular viability among the tested surfaces and the lowest corrosion resistance. Full article

Background and Clinical Significance: Cervical ectopic pregnancy (CEP) is a rare and potentially serious condition, in which the embryo implants within the cervical canal rather than the uterine cavity and is present in less than 1% of all ectopic pregnancies. There are different treatment options depending on the particular situation and the woman’s reproductive desire but conservative approaches as the first line of treatment is preferred in all cases and hysteroscopic resection of the fetus is one of these options. Several types of laser systems are available for use in hysteroscopic surgery, including neodymium:YAG (Nd:YAG) lasers, KTP and Argon lasers, as well as diode lasers. The holmium:YAG (Ho:YAG) laser, although more commonly used in urology due to its ability to cut, coagulate, and vaporize tissue, has gained interest in gynecologic procedures because of its precision and favorable safety profile. Case Presentation: We present the case of a 32-year-old woman, pregnant for the first time, who was diagnosed with CEP and successfully treated using a Ho:YAG laser during an outpatient hysteroscopic procedure. As far as we know, this is the first published case using this approach. Conclusions: The Ho:YAG laser is a proven tool for outpatient hysteroscopic procedures like septum and adhesion removal. Its ability to both cut and coagulate offers a minimally invasive, fertility-sparing option for managing cervical ectopic pregnancy. With the right patient and proper backup plans in place, this approach could be a promising alternative to more aggressive treatments. Full article

Stone cleaning for cultural heritage monuments is a critical conservation intervention that must effectively eliminate harmful surface contaminants while preserving the material’s physical, chemical, and historical integrity. This study investigated the removal of tenacious black biofilms formed by Nocardia species previously isolated from deteriorated limestone from the Bastet tomb in Tell Basta, Zagazig City, Egypt, using a Q-switched 1064 nm Nd:YAG laser. Experimental limestone specimens were systematically inoculated with Nocardia sp. under controlled laboratory conditions to simulate biodeterioration processes. Comprehensive testing revealed that a laser fluence of 0.03 J/cm² with a 5 ns pulse duration, applied under wet conditions with 500 pulses, achieved the complete elimination of the biological black film without damaging the underlying stone substrate. The cleaning efficacy was evaluated through an integrated analytical framework combining stereomicroscopy, scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), X-ray diffraction (XRD), and laser-induced plasma spectroscopy (LIPS). These analyses demonstrated a remarkable transformation from a compromised mineralogical composition dominated by gypsum (62%) and anhydrite (13%) to a restored state of 98% calcite, confirming the laser treatment’s effectiveness in reversing biodeterioration processes. SEM micrographs revealed the complete elimination of mycelial networks that had penetrated to depths between 984 μm and 1.66 mm, while LIPS analysis confirmed the restoration of elemental signatures to near-control levels. The successful application of LIPS for real-time monitoring during cleaning provides a valuable tool for preventing overcleaning, addressing a significant concern in laser conservation interventions. This research establishes evidence-based protocols for the non-invasive removal of Nocardia-induced black biofilms from limestone artifacts, offering conservation professionals a precise, effective, and environmentally sustainable alternative to traditional chemical treatments for preserving irreplaceable cultural heritage. Full article

Background/Objectives: The Tecnis Eyhance is an enhanced monofocal intraocular lens (IOL) designed to improve intermediate vision without compromising distance clarity or increasing the incidence of photic phenomena. Although short-term results have been encouraging, long-term data remain limited. This study presents the 5-year follow-up of a previously published 6-month clinical evaluation, aiming to assess the stability of visual, optical, and patient-reported outcomes over time. Methods: A single-center retrospective study of 18 patients (36 eyes) undergoing bilateral Tecnis Eyhance IOL implantation was conducted. The same cohort from the original 6-month study was re-evaluated after a mean follow-up of 5 years. Visual acuity (distance, intermediate, near), defocus curves, contrast sensitivity, optical quality, effective lens position (ELP), halo size, and patient-reported measures were assessed. Results: Visual acuity remained stable across all distances, with binocular uncorrected intermediate visual acuity (UIVA) ≤ 0.2 logMAR in all patients. No significant changes were observed in optical quality parameters or contrast sensitivity. ELP remained consistent over time (p = 0.298), and posterior capsule opacification (PCO) requiring Nd:YAG capsulotomy developed in 5% of the eyes. Halo size was mild, and subjective glare perception did not increase. Spectacle independence remained high for distance (100%) and intermediate (more than 75%) tasks. Conclusions: This 5-year follow-up study confirms the long-term stability and effectiveness of the Tecnis Eyhance IOL. These findings support its long-term use as a stable monofocal IOL with enhanced intermediate function. Full article

(1) Background: This study aimed to compare alveolar bone preservation and early healing outcomes following a comprehensive laser-assisted post-extraction protocol compared to conventional extraction alone. In addition, the potential influence of serum vitamin D levels on bone regeneration was assessed. (2) Methods: Thirty tooth extractions were performed and randomized into two groups: a test group (G1, n =15) and a control group (G2, n = 15). G1 received a laser-assisted protocol using Er:YAG and Nd:YAG lasers for granulation tissue removal, socket disinfection, clot stabilization, de-epithelialization, and photobiomodulation (PBM) with the Genova handpiece (LightWalker, Fotona, Slovenia). G2 underwent standard mechanical extractions and socket debridement without laser. (3) Results: Procedures in G1 were on average 8.7 min longer, but patients in this group reported significantly lower postoperative pain during the first three days (p < 0.05). A statistically significant difference in alveolar height was observed at the distal lingual site (25.4 mm vs. 21.7 mm; p = 0.046), with other sites showing a trend toward significance. Cumulative bone preservation, measured by Bone Loss Index (BLI4), was significantly better in the laser group. Notably, a positive correlation was found between serum vitamin D levels and bone preservation: each 1 ng/mL increase in vitamin D corresponded to a 0.18 mm gain in alveolar height (p = 0.021). (4) Conclusions: The comprehensive laser-assisted post-extraction protocol reduced postoperative pain and improved alveolar bone preservation, particularly at the lingual distal site. Serum vitamin D levels positively correlated with healing outcomes, suggesting a potential synergistic role of systemic and local regenerative factors. Full article

In this manuscript, we demonstrated a switchable single-/dual-wavelength Yb:YAG laser based on intracavity loss modulation in a dual-confocal resonator configuration. The laser employed a dual-confocal resonator with a length of 175 mm that enabled the controlled adjustment of geometric losses through precise angular modulation of the output coupler, achieving stable switching between single- and dual-wavelength operations. Under a maximum pump power of 20.98 W, the laser delivered 1.868 W of single-wavelength output at 1050 nm with an optical-to-optical (O–O) conversion efficiency of 8.9%, exhibiting excellent power stability (RMS < 0.6%). When it was switched to a dual-wavelength operation at 1030 nm and 1050 nm, the total output power reached 0.376 W with respective powers of 0.180 W (1030 nm) and 0.196 W (1050 nm), corresponding to a 1.792% O–O conversion efficiency and a power stability of RMS < 3.0%. When it was switched to single-wavelength operation at 1030 nm, the maximum output power reached 0.193 W with a 0.920% O–O conversion efficiency and a power stability of RMS < 1.5%. These experimental results confirm that the controlled modulation of geometric losses in a dual-confocal resonator provides an effective approach for achieving flexible wavelength switching while maintaining stable output performance. This methodology offers promising potential for expanding the application scope of dual-wavelength lasers in precision optical systems. Full article

Introduction: Actinic cheilitis (AC) is a common precancerous condition affecting the lips, primarily caused by prolonged ultraviolet radiation exposure. Various treatment options are available. However, the optimal treatment approach remains a subject of debate. Objective: To summarize and compare practice-relevant interventions for AC. Materials and Methods: A pre-defined protocol was registered in PROSPERO (CRD42021225182). Systematic searches in Medline, Embase, and Central, along with manual trial register searches, identified studies reporting participant clearance rates (PCR) or recurrence rates (PRR). Quality assessment for randomized controlled trials (RCTs) was conducted using the Cochrane Risk of Bias tool 2. Uncontrolled studies were evaluated using the tool developed by the National Heart, Lung, and Blood Institute. The generalized linear mixed model was used to pool proportions for uncontrolled studies. A pairwise meta-analysis for RCTs was applied, using the odds ratio (OR) as the effect estimate and the GRADE approach to evaluate the quality of the evidence. Adverse events were analyzed qualitatively. Results: A comprehensive inclusion of 36 studies facilitated an evaluation of 614 participants for PCR, and 430 patients for PRR. Diclofenac showed the lowest PCR (0.53, 95% confidence interval (CI) [0.41; 0.66]), while CO₂ laser showed the highest PCR (0.97, 95% CI [0.90; 0.99]). For PRR, Er:YAG laser showed the highest rates (0.14, 95% CI [0.08; 0.21]), and imiquimod the lowest (0.00, 95% CI [0.00; 0.06]). In a pairwise meta-analysis, the OR indicated a lower recurrence rate for Er:YAG ablative fractional laser (AFL)-primed methyl-aminolevulinate photodynamic therapy (MAL-PDT) (Er:YAG AFL-PDT) compared to methyl-aminolevulinate photodynamic therapy (MAL-PDT) alone (OR = 0.22, 95% CI [0.06; 0.82]). The CO₂ laser showed fewer local side effects than the Er:YAG laser, while PDTs caused more skin reactions. Due to qualitative data, comparability was limited, highlighting the need for individualized treatment. Conclusions: This study provides a complete and up-to-date evidence synthesis of practice-relevant interventions for AC, identifying the CO₂ laser as the most effective treatment and regarding PCR and imiquimod as most effective concerning PRR. Full article

In this study, a novel direct laser beam turning (DLBT) approach is proposed for the precision machining of AISI 308L austenitic stainless steel, which eliminates the need for cutting tools and thereby eradicates tool wear and vibration-induced surface irregularities. A nanosecond-pulsed Nd:YAG fiber laser (λ = 1064 nm, spot size = 0.05 mm) was used, and Ø1.6 mm × 20 mm cylindrical rods were processed under ambient conditions without auxiliary cooling. The experimental framework systematically evaluated the influence of scanning speed, pulse frequency, and the number of laser passes on dimensional accuracy and material removal efficiency. The results indicate that a maximum diameter reduction of 0.271 mm was achieved at a scanning speed of 3200 mm/s and 50 kHz, whereas 0.195 mm was attained at 6400 mm/s and 200 kHz. A robust second-order polynomial correlation (R² = 0.99) was established between diameter reduction and the number of passes, revealing the high predictability of the process. Crucially, when the scanning speed was doubled, the effective fluence was halved, considerably influencing the ablation characteristics. Despite the low fluence, evidence of material evaporation at elevated frequencies due to the incubation effect underscores the complex photothermal dynamics governing the process. This work constitutes the first comprehensive quantification of pass-dependent diameter modulation in DLBT and introduces a transformative, noncontact micromachining strategy for hard-to-machine alloys. The demonstrated precision, repeatability, and thermal control position DLBT as a promising candidate for next-generation manufacturing of high-performance miniaturized components. Full article

This work presents a comprehensive study of the structural, luminescent, and photoconversion properties of epitaxial composite phosphor converters based on single crystalline films of Ce³⁺-activated Ca_2−xY_1+xMg_1+xSc_1−xSi₃O₁₂:Ce (x = 0–0.25) (CYMSSG:Ce) garnet, grown using the liquid phase epitaxy (LPE) method on single-crystal Y₃Al₅O₁₂ (YAG) and YAG:Ce substrates. The main goal of this study is to elucidate the structure–composition–property relationships that influence the photoluminescence and photoconversion efficiency of these film–substrate composite converters, aiming to optimize their performance in high-power white light-emitting diode (WLED) applications. Systematic variation in the Y³⁺/Sc³⁺/Mg²⁺ cationic ratios within the garnet structure, combined with the controlled tuning of film thickness (ranging from 19 to 67 µm for CYMSSG:Ce/YAG and 10–22 µm for CYMSSG:Ce/YAG:Ce structures), enabled the precise modulation of their photoconversion properties. Prototypes of phosphor-converted WLEDs (pc-WLEDs) were developed based on these epitaxial structures to assess their performance and investigate how the content and thickness of SCFs affect the colorimetric properties of SCFs and composite converters. Clear trends were observed in the Ce³⁺ emission peak position, intensity, and color rendering, induced by the Y³⁺/Sc³⁺/Mg²⁺ cation substitution in the film converter, film thickness, and activator concentrations in the substrate and film. These results may be useful for the design of epitaxial phosphor converters with tunable emission spectra based on the epitaxially grown structures of garnet compounds. Full article

A novel total internal reflection solar end-pumped laser system has been introduced for the first time, aimed at enhancing the solar-to-laser conversion efficiency. Utilizing a conical solid or cavity reflector, this system refocuses sunlight from a 0.2818 $m^2$ parabolic mirror into a single Ce (0.05 at.%): Nd (1 at.%): YAG crystal rod, measuring 4 mm in diameter and 10 mm in length, thereby promoting total internal reflection and extending the pumping path. Simulation results indicate that under the same solar input power conditions (249.05 W), the conversion efficiencies of the conical solid reflector and cavity reflector systems are 1.2 times and 1.33 times higher than the current highest recorded efficiency of single-rod systems, respectively. At 950 ${W/m}^2$, the conical reflector reaches 5.48% efficiency, while the cavity reflector attains 6.09%. Their collection efficiencies are 52.03 ${W/m}^2$ and 57.90 ${W/m}^2$, with slope efficiencies of 6.65% and 7.72%. Full article