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Evaluating the effectiveness of two wavelengths of 810 and 980 nm Diode laser with two different beam profiles on tooth discoloration in bleaching: an experimental study

Teeth color has a significant impact on facial aesthetics. Tooth bleaching is the safest way to lighten the color of your teeth. Today, hydrogen peroxide is the most commonly used bleaching agent. The diode laser is one of the light sources that speeds up the bleaching process. One of the laser beam features is the laser beam profile, which depicts the distribution of laser intensity across the beam section. The goal of this study is to look into the effectiveness of Gaussian and Flat top beam profiles on tooth shade using two diode laser wavelengths of 810 and 980 nm in the tooth bleaching process. Fifty human anterior and premolar teeth were extracted and placed in a tea and coffee solution for three weeks before being divided into five groups. The first group did not receive laser radiation because 40% hydrogen peroxide was used; in the second and third groups, the profile of the flat top beam and the wavelength were 810 and 980 nm, respectively; and in the fourth and fifth groups, the wavelength of the Gaussian beam profile was 810 and 980 nm. The shade of the samples before and after bleaching was measured with a CIELab-based spectrophotometer, and the results were analyzed using one-way ANOVA and Tukey’s multiple comparison test. All bleaching methods resulted in a significant change in tooth color (ΔE>3.3). There was a significant difference in average shade changes across groups (P<0.001). The highest degree of shade change was observed in two groups of lasers with a wavelength of 980 nm and profiles of Flat top beam (ΔE=5.35) and Gaussian (ΔE=5.02). There were no differences between the remaining groups. We conclude that the 980 nm wavelength produces a greater shade change than the 810 nm wavelength and chemical method. The diode laser’s 810 nm wavelength has no effect on the shade of teeth.

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Biomechanical changes after keratorefractive lenticule extraction with CLEAR and after femtosecond LASIK, correlated with optical coherence tomography findings

The aim of this retrospective, comparative, single-eye study was to assess the biomechanical changes after laser correction of myopia by keratorefractive lenticule extraction (KLEx) and by femtosecond LASIK (FS-LASIK), correlating them with the stromal changes on anterior segment optical coherence tomography. Corneal biomechanical parameters, provided by the high-speed Scheimpflug camera CorVis-ST (Oculus Optikgeräte GmbH) and measured pre-operatively and 1 week post-operatively, were: stiffness parameter at first applanation (SP-A1), stress-strain index (SSI), inverse integrated radius (IIR), deformation amplitude ratio at 2 mm (DA ratio-2mm). A total of 79 eyes undergone KLEx (CLEAR, Ziemer Group) and 93 eyes undergone FS-LASIK were included. The mean residual stromal bed (RSB) was 271.36±17.22 µm after KLEx and 304.21±21.82 µm after FS-LASIK (p=0.00). All parameters in both groups showed statistically significant post-operative changes (p=0.00), except for SSI after FS-LASIK (p=0.39). The percent changes in all parameters were significantly higher in the KLEx group. Even in the eyes with equal RSB (300±5 µm; 19 eyes post-KLEx, 26 eyes post-FS-LASIK), changes were significantly higher after KLEx (SP-A1: -35.9%; SSI: -6.7%) than after FS-LASIK (SP-A1: -29.6%; SSI: -3.8%) (respectively, p=0.02, and p=0.00). In KLEx, reduction in stromal thickness had a weak correlation with reduction in SP-A1 (r=0.39), and poor correlation with reduction in SSI (r=0.26). In conclusion, stiffness parameters were significantly worse after KLEx than after FS-LASIK, even in eyes ending with similar RSB. These findings should be valued cautiously, as the CorVis-ST might not capture all the clinically significant alterations, especially in the post-KLEx bi-layered cornea.

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Frequency-doubled neodymium yttrium aluminum garnet (Nd:YAG) laser trabeculoplasty as adjuvant therapy for open-angle glaucomas

The thermal frequency-doubled Nd:YAG (neodymium: yttrium-aluminum-garnet) laser was used sparingly for trabeculoplasty. Our goal was to assess the efficacy and safety of frequency-doubled Nd:YAG laser trabeculoplasty as an adjunct therapy to anti-glaucoma medications in open-angle glaucoma. Laser trabeculoplasty was performed on 41 eyes of 22 adults with open-angle glaucomas using a thermal frequency-doubled Nd:YAG laser (Green laser photocoagulator GYC-500® 532 nm, Nidek, Japan). To assess the laser’s effectiveness, patients were monitored for intraocular pressure (IOP) reduction, control, and complications at 1 hour, 1 week, and then monthly for a year. Primary open-angle glaucoma was the most common diagnosis in 31 (75.6%) eyes. The pre-laser baseline IOP was 18.87±3.66 mmHg. The mean IOP was 14.9±2.54 mmHg at Week 1 (p = 0.000), 14.65±2.50 mmHg at Month 1, 14.53±2.60 mmHg at Month 3, 15.85±2.30 mmHg at Month 6, and 15.14±2.17 mmHg at Month 12 (p=0.000). A significant percentage reduction in IOP was achieved at 1, 3, 6, and 12 months: 21.78%, 22.48%, 16.73%, and 18.53%, respectively. Patients used an average of 2.73±1.00 topical drugs before laser treatment. There was a significant reduction in medicines after laser treatment on all occasions, at 1, 3, 6, and 12 months (p = 0.000). Complications included some degree of peripheral anterior synechiae (PAS) in 20 (51.3%) eyes; an IOP spike in one patient only, bilaterally (5.1%) at 1 hour after therapy; and mild anterior uveitis in four (9.75%) cases. To summarize, frequency-doubled Nd:YAG laser trabeculoplasty is a safe and effective adjuvant therapy for open-angle glaucoma that reduces intraocular pressure and medication use.

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Pre-prosthetic atraumatic laser-assisted mandibular rehabilitation: Er,Cr:YSGG 2780 nm for alveoloplasty and mucocele removal. A case report

Lasers are a popular technology in many areas of dentistry due to their low invasiveness, quick tissue response, and rapid healing time. Mucoceles develop from minor salivary glands, whereas bony exostosis is a prosthodontic challenge that prevents optimal prosthetic management. Scarring, pain, and discomfort are common drawbacks of traditional surgical approaches, which are followed by prolonged postoperative healing. Laser-assisted mandibular rehabilitation is a promising approach with predictable results. The patient complained of severe pain during denture fabrication, as well as a small, painless swelling on the inner aspect of the lower lip. The patient was able to receive the planned complete dentures after undergoing atraumatic laser-assisted removal of mucocele and bone exostosis with an Er,Cr:YSGG (Erbium, chromium-doped, yttrium, scandium, gallium, and garnet) laser treatment at 2780 nm. Both procedures were completed quickly, and there were no postoperative complications to report. Blanching overlying both lesions quickly faded after healing and was replaced by a healthy pink mucosal color; both lesions were monitored until complete healing. The Er,Cr:YSGG effectively ablated and removed both soft and hard tissue lesions with minimal bleeding and pain.

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Pre-prosthetic atraumatic laser-assisted mandibular rehabilitation: Er,Cr:YSGG 2780 nm for alveoloplasty and mucocele removal. A case report

Lasers are a popular technology in many areas of dentistry due to their low invasiveness, quick tissue response, and rapid healing time. Mucoceles develop from minor salivary glands, whereas bony exostosis is a prosthodontic challenge that prevents optimal prosthetic management. Scarring, pain, and discomfort are common drawbacks of traditional surgical approaches, which are followed by prolonged postoperative healing. Laser-assisted mandibular rehabilitation is a promising approach with predictable results. The patient complained of severe pain during denture fabrication, as well as a small, painless swelling on the inner aspect of the lower lip. The patient was able to receive the planned complete dentures after undergoing atraumatic laser-assisted removal of mucocele and bone exostosis with an Er,Cr:YSGG (Erbium, chromium-doped, yttrium, scandium, gallium, and garnet) laser treatment at 2780 nm. Both procedures were completed quickly, and there were no postoperative complications to report. Blanching overlying both lesions quickly faded after healing and was replaced by a healthy pink mucosal color; both lesions were monitored until complete healing. The Er,Cr:YSGG effectively ablated and removed both soft and hard tissue lesions with minimal bleeding and pain.

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Infectious keratitis after photorefractive keratectomy, femtosecond-LASIK and lenticule extraction in a 100,000-eye case series

This study evaluates the incidence and outcome of infectious keratitis after laser vision correction by photorefractive keratectomy (PRK), femtosecond LASIK, and keratorefractive lenticule extraction (KLEx) in a retrospective, consecutive, single-institute series. Patients with presumed infectious keratitis between 2011 and 2023 were analyzed. In PRK, manual deepithelialization was done, and mitomycin C was used with spherical equivalents greater than 3 diopters. Femtosecond LASIK and KLEx were performed with an LDV Ziemer laser; the interface was rinsed in both techniques. All treatments received post-operative netilmicin eyedrops. Finally, 106269 eyes of 54278 patients were included; 6 eyes of 6 patients were identified as having infectious keratitis (3 by staphylococci, 3 culture-negative). The overall incidence of infectious keratitis was 0.0056% (0.0164% after PRK, 0.0023% after femtosecond LASIK, 0.1366% after KLEx; Chi2 p<0.00001). The odds ratio for PRK compared to LASIK was 7.2 (p=0.0307); for KLEx compared to LASIK 59.7 (p=0.0008). Presentation after KLEx (2 days) was earlier than after PRK (5, 4, and 5 days) and LASIK (6 and 4 days). In all cases, hourly fortified cefazolin and tobramycin eyedrops were used, with a good response: 3 eyes maintained a 20/20 uncorrected visual acuity; 2 eyes 20/20 with myopic astigmatism; 1 eye ended 20/25 with correction because of irregular astigmatism. In conclusion, infectious keratitis was a rare complication, more common after KLEx and less common after femtosecond-LASIK. Only 3/6 cases had a positive culture. All the cases in our series had a favorable outcome.

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