In vitro bactericidal effect of Nd:YAG laser on Actinomyces israelii

A bactericidal effect has been reported by the use of near-infrared laser light on both Gram-positive and Gram-negative bacteria. The aim of this study was to evaluate the effect of Nd:YAG laser on Actinomyces israelii, filamentous bacteria causing cervicofacial actinomycosis. Experiments were realized on bacterial cells in saline suspension or streaked on Mueller–Hinton (MH) agar plates with or without India ink. Laser application was performed in Eppendorf tubes with different powers and frequencies for 40 s; bacterial suspensions were then streaked on agar plates and incubated at 35 °C in proper conditions for 5 days before colony enumeration. A reduction of colony number variable from 60.13 to 100 % for powers of 2, 4, and 6 W at 25–50 Hz of frequency was observed in comparison with growth control. For agar plates, laser application was performed with different powers at 50 Hz for 60 s. A growth inhibition was observed after 5 days of incubation on MH plates with powers of 6 W and on MH–ink plates with all applied powers. This preliminary study showed a bactericidal effect caused by Nd:YAG laser application worthy to be evaluated in further experiments in vivo.     

In vitro effects of Nd:YAG laser radiation on blood: A quantitative and morphologic analysis

Use of the Neodymium: yttrium -aluminum -garnet (Nd:YAG) laser to recanalize stenosed arteries may require delivery of the beam through blood. To assess the degree of hemolysis and debris formation, 54 samples of citrated whole blood were exposed to Nd:YAG laser radiation of varying powers (10, 20 and 30 watts) and duration (1, 2.5 and 5 seconds). Compared to control samples which were not subjected to laser light, there was no significant decrease in hematocrit (41 to 40.5 +/- 5%), hemoglobin concentration (13.8 to 13.8 +/- .06 g/1OO ml), or increase in "free" hemoglobin concentration. Debris weight (from .45 +/- .002 to .45 +/- .002 mg), as well as the white blood cell count, was also not significantly changed (from 5,400 to 5,200 +/- 240 WBC/cm). Light microscopy examination of debris from samples of whole blood, washed erythrocytes, and platelet-rich plasma subjected to the laser at 30 watts for five seconds failed to demonstrate the presence of membrane denaturation of blood elements, as compared with the morphologic changes observed in whole blood samples exposed to a "hot tip" rather than Nd:YAG laser radiation. Nd:YAG laser can be used intravascularly without fear of hemolysis or debris "micro-embolization" up to a power of 30 watts for five seconds.     

Efficacy of a combined Er:YAG laser and Nd:YAG laser in non-surgical treatment for severe periodontitis

Lasers in Medical Science - Severe periodontitis is challenging to treat. The aim of this study was to evaluate the efficacy of a combined Er:YAG laser (ERL) and Nd:YAG laser (NDL)...     

Modeling of tissue heating with a pulsed Nd:YAG laser

Temperature profiles were measured in large sections of bovine muscle and bovine liver exposed to single pulses from a clinical Nd:YAG laser. The data were analyzed with a photothermal model applicable to an incident gaussian beam including the effects of beam spread and heat flow. Closed form expressions for the radial average initial temperatures and thermal relaxation were derived and compared with the measurements.     

Ablation of polymethylmethacrylate by Ho:YAG,Nd:YAG,and Erb:YAG lasers

Ho:YAG, Nd:YAG, and Erb:YAG laser ablation of Polymethylmethacrylate (PMMA) was investigated under in vitro and simulated clinical conditions. Ablation rates were measured for all lasers and after ablation, macroscopic and microscopic appearance of the ablation site was investigated. The mean ablation rates of the Erb:YAG, Ho:YAG, and Nd:YAG laser increased from 8 μm per pulse at 100 mJ to 44 μm per pulse at 300 mJ from 100 μm per pulse at 200 mJ to 222 μm per pulse at 800 mJ and from 28 μm per pulse at 100 mJ to 189 μm per pulse at 800 mJ, respectively. Macroscopic investigation exhibited melting of bone cement for the Ho:YAG and Nd:YAG lasers and pulse-to-pulse vaporization for the Erb:YAG laser. The width of thermal alteration, however, was comparable for all lasers used. Removal of cement from bone specimens under simulated clinical conditions showed good detachment of cement when the fiber was used parallel; in case of perpendicular use, remainders of cement and carbonization of bone could be observed upon histological investigation. © 1993 Wiley-Liss, Inc.     

强脉冲光联合调Q激光治疗色素增生性皮肤病

目的探讨强脉冲光联合调Q激光疗法对面部色素增生性皮肤病的疗效及安全性。方法根据患者面部色素性疾病的特点,对225例FitzpatrickⅢ、Ⅳ型皮肤的色素细胞增生性皮肤病患者,采用560nm强脉冲光联合调Q532nm激光治疗,首先使用560nm强脉冲光,能量密度30～40J／cm2的光子嫩肤治疗,每月1次,3个月后观察疗效。对于改善不品著的脂溢性角化斑、咖啡斑及眼睑、口唇周围残留的雀斑等,再使用调Q532nm激光,施行局部针对性治疗,能量密度70J／cm2。于激光治疗后2个月,对皮损的改善和满意度进行评估并记录不良反应。结果90％患者的雀斑、咖啡斑、脂溢性角化斑的色素均有50％～70％不同程度的消退,同时毛细血管扩张、毛孔粗大、细小皱纹均达到了60％以上的程度的改善。主要并发症为暂时性红斑和水疱。结论560nm强脉冲光联合调Q激光治疗面部色素增生性皮肤病安全有效,同时能有效改善肤质。     

CO2激光结合Nd:YAG激光治疗色素痣的临床观察

目的：评价CO2激光结合Nd：YAG激光治疗色素痣的疗效。方法：先用CO2激光选择连续脉冲，小功率输出，烧灼皮损到周围正常皮肤水平，继之用Nd：YAG激光治疗，治疗面部色素痣128例、768个皮损。结果：Ⅰ、Ⅱ级(痊愈 显效)率为96．76％。治疗次数平均为1.32次。结论：采用CO2激光结合Nd：YAG激光治疗面部色素痣疗效肯定，治愈率高，疗程短。多数患者无明显瘢痕形成。     

A split-face,evaluator-blind randomized study on the early effects of Q-switched Nd:YAG laser plus Er:YAG micropeel (combined therapy) versus Q-switched Nd:YAG alone in light solar lentigines in Asians

Solar lentigines are a common sign of aging in Asians, who often asked for treatment. Various lasers, including Q-switched Nd:YAG and Er:YAG, have been adopted, but the results are not always satisfactory, especially for those who are relatively light in color. Our objective was to compare the early effects as well as side effects of Q-switched Nd:YAG laser plus Er:YAG micropeel (combined therapy) with those of Q-switched Nd:YAG laser (QSNY) alone in light solar lentigines in Asians. This was a split-face, evaluator-blind, randomized controlled study. A single session of treatment was performed on Asian patients with light facial lentigines. A combined treatment with QSNY and Er:YAG micropeel was allocated to one half of the face, and QSNY alone to the other half. The response to therapy was evaluated by two independent dermatologists, with standardized photographs taken 2 weeks and 1 month after the laser treatment. Patients’ satisfaction and preference in treatment were also assessed. Fifteen patients completed the study and were analyzed. Overall, a reduction in pigment was observed with both treatment arms during the study period. The degree of pigment reduction following combined therapy and QSNY alone was similar at 2 weeks’ follow-up (P?=?0.433). However, due to the higher incidence of postinflammatory hyperpigmentation (PIH) with combined therapy (73.3 vs 40 %), the degree of pigment reduction in the combined side of the face was found significantly lower than that of the QSNY-alone side at 1-month follow-up (P?=?0.014). Although our study results show that both combined therapy and QSNY alone are capable of reducing pigmentation, QSNY alone is considered to have more favorable qualities than combined treatment for light solar lentigines in Asians.     

In vitro inactivation of endodontic pathogens with Nd:YAG and Er:YAG lasers

Both Nd:YAG and Er:YAG lasers have been suggested as root canal disinfection aids. The aim of this in vitro study is to compare both wavelengths in terms of irradiation dose required for microbial inactivation, to quantify these irradiation doses and to investigate the influence of certain (laser) parameters on the antimicrobial efficacy. Agar plates containing a uniform layer of Enterococcus faecalis, Candida albicans or Propionibacterium acnes were mounted perpendicularly underneath the laser handpieces (5?mm spot). The Er:YAG laser was operated in single-pulse mode. Pulse energies of 40–400?mJ and pulse lengths of 100, 300, 600, and 1,000?μs were tested. After incubation at 37°C for 48?h, growth on the plates was scored. The pulse energy yielding complete absence of growth over the entire spot area was taken as the total inhibition threshold (TIT). TITs were determined for every species and pulse length. The Nd:YAG laser was operated with pulse trains because single pulses were ineffective. Output power was 15?W and frequency was 100?Hz. Spots were irradiated for 5–120?s. After incubation, the diameters of the inhibition zones were measured. For the Er:YAG laser, TITs varied between 100 and 210?mJ, and differed significantly between species and pulse lengths. Using Nd:YAG irradiation, TITs were around 5,300?J/cm² for C. albicans and 7,100?J/cm² for P. acnes. No inhibition was observed for E. faecalis. Er:YAG irradiation was superior to Nd:YAG in inactivating microorganisms on agar surfaces.     

Comparison of tissue effects with sculptured fiberoptic cables and other Nd:YAG laser and argon laser treatments.

The use of a fiber optic cable in contact with tissue results in a complex thermal interaction between the cable and the tissue. The effect of the laser-tissue interaction was investigated using sculptured quartz fiber optic cables, sapphire contact rods, and bare fiber optic cables attached to the Nd:YAG laser. The laser-tissue effects of the Nd:YAG and argon lasers were compared. Examination of treated animals showed there to be a significant difference between immediate and 48-hour thermal effects. The sculptured fibers created significantly less tissue damage than the sapphire contact tips, the 0.6-mm bare fiber, or the argon laser with a 0.3-mm bare fiber either with or without contact. All Nd:YAG laser contact treatments were less damaging than the argon laser treatments.     

Use of the pulsed Nd:YAG laser for intraoral soft tissue surgery.

Application of a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser was compared to conventional scalpel in dental soft tissue surgery. Two surgery sites on 29 patients were randomly selected and treated. An additional 41 patients were exclusively treated with the Nd:YAG laser. The surgical technique was then evaluated for periodontal pocket depths, degree of pain perceived, bleeding, inflammation, procedure time, and anesthesia. Surgical prognosis was made at the time of surgery and compared to actual healing 1 week and 1 month after surgery. No differences were observed between laser and scalpel surgery in terms of pocket depth reduction, postoperative pain, post-operative inflammation, and treatment time. However, operative and postoperative bleeding with laser surgery were significantly less than with conventional surgery. Anesthesia is required for scalpel surgery, the majority of laser-treated sites evoked minimal pain without anesthesia. These results indicate that the Nd:YAG laser can be used successfully for intraoral soft tissue applications are well tolerated without anesthesia and minimal bleeding compared to scalpel surgery.     

Evaluation of the effects of Er:YAG laser,Nd:YAG laser,and two different desensitizers on dentin permeability: in vitro study

The purpose of this in vitro study was to evaluate and compare the efficacy of erbium-doped yttrium aluminum garnet (Er:YAG) laser, neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, PrevDent nano-hydroxyapatite toothpaste plus Repairing Serum Kit (PNH), and NUPRO Sensodyne Prophylaxis Paste with NovaMin (NPP) on dentin permeability reduction. Forty dentin discs obtained from bovine incisors were divided into four study groups: Er:YAG laser-treated (2940 nm; 0.2 W, 80 mJ/pulse, 3 Hz); Nd:YAG laser-treated (1064 nm; 1 W, 10 Hz); PNH-treated; and NPP-treated groups. The quantitative changes in permeability of each dentin disc were measured using a computerized fluid filtration method (CFFM) before and after desensitizer treatments. The data were analyzed using the Wilcoxon, paired-samples t, Kruskal-Wallis, and Mann-Whitney U tests. The dentin surfaces and tubules were also morphologically detected by scanning electron microscopy (SEM). In all groups, dentin permeability was significantly reduced after the desensitizer and laser treatments (p?<?0.05). Among the groups, we detected a significant difference in only when comparing the Er:YAG laser- and NPP-treated groups (p?=?0.034). SEM analysis revealed physical changes in the dentin surface in all groups. This in vitro study shows that all tested desensitizers and laser treatments reduced dentin permeability. Also, surface changes, such as complete or partial occlusion or shrinkage of dentin tubules, were observed in all groups. Although the laser groups performed best, the PNH protocol can be considered as an alternative therapeutic product. In addition, clinical and laboratory studies should be performed for this product, and their efficacy should be assessed by combined therapy with lasers.     

Transurethral Nd:YAG laser prostatectomy with a laterally firing fiber: Local effects on tissue associated with erectile dysfunction

Background and Objectives: Transurethral laser prostatectomy is anticipated to become a recognized alternative to conventional transurethral resection of the prostate. However, the effects of this procedure on the nerves of the pelvic plexus and erectile dysfunction remain unaddressed. The objective of this study was to evaluate the effects of laser energy on extent of prostatic damage as well as injury to periprostatic cavernosal nerves and erectile dysfunction in a canine model. Study Design/Materials and Methods: Six adult male mongrel dogs underwent transurethral laser prostatectomy at 30 (n = 3) and 40 (n = 3) watt power settings. Total laser energy delivered varied between 6,000 and 13,800 joules. Erectile function was evaluated by pelvic nerve stimulation at 2, 4, and 8 weeks. Animals were then sacrificed to assess histopathology of the prostate at each time point. Results: Histopathologic changes were noted in the prostate in a dose-dependent manner and did not vary with different laser power settings. In dogs that received ?10,000 J, substantial prostate ablation confined within the capsule was achieved in every prostate gland. Adequate erectile responses were noted in five of six animals; all received < 10,000 J. In one animal that received a total dose of 13,800 J, an erectile response was not obtained, and histology revealed both prostatic capsule perforation in close proximity to the cavernous nerves and thermal neural damage. Conclusions: We conclude that cavernous nerve damage may result from excessive doses of laser energy during transurethral laser treatment of the prostate gland. In canines, the upper limit for periprostatic injury is between 10 and 14,000 joules. © 1995 Wiley-Liss, Inc.     

Intense pulsed light and Nd:YAG laser non-ablative treatment of facial rhytids

BACKGROUND AND OBJECTIVE: The aim of this study was to evaluate the efficacy and safety of the intense pulsed light source (IPL) and the Nd:YAG laser in the treatment of facial rhytids. Both systems can be used in a non-ablative manner and cause a dermal wound. This is thought to stimulate the production of new collagen without epidermal disruption. Non-ablative techniques eliminate the downtime that must be endured by patients treated with ablative methods such as the carbon dioxide and erbium lasers. STUDY DESIGN/MATERIALS AND METHODS: Fifteen subjects with perioral rhytids and Fitzpatrick skin types II and III received three-to-five treatments with the IPL using 590 and 755 nm cut-off filters, and the 1,064-nm Nd:YAG laser. The subjects were evaluated at 2, 4, 8, 12, and 24 weeks after the final treatment for improvement in rhytids and presence of any side effects. RESULTS: At 6 months, the patient satisfaction score (1-10) was comparable in all three groups. Evaluator assessment of improved skin quality was also similar in all three treatment groups. Side effects such as blistering and erythema were most commonly seen in the subjects treated with the IPL. The least discomfort was seen with the Nd:YAG laser. CONCLUSIONS: Although both non-ablative treatment systems improved facial rhytids presumably by causing a non-specific dermal wound, the Nd:YAG laser was better tolerated and produced fewer side effects.