Laser Power Settings Research Articles

The arthroscopically assistedholmium:YAG laser surgery in the shoulder

The Holmium:YAG (Ho:YAG) laser is the arthroscopic laser of choice. The arthroscopic surgeon can ablate, coagulate, or shrink periarticular soft tissues by manipulating Ho:YAG laser power settings. The ability to ablate soft tissue in a hemostatic fashion greatly facilitates the treatment of labral tear, synovitis, subacromial arch decompression, and distal clavicle arthritis. The nonablative application of Ho:YAG laser energy has been used successfully to treat glenohumeral instability. The laser-assisted capsular shift (LACS) procedure, in conjunction with standard labral repair techniques, successfully treats unidirectional and multidirectional shoulder instability Neuromuscular rehabilitation is accelerated. Excellent clinical results may be achieved with appropriate surgical technique and postoperative rehabilitation.

Permeability of dentine after Nd:YAG laser treatment: an in vitro study

summary The purpose of this investigation was to determine the effects of Nd:YAG laser treatment on the permeability of dentine. Forty dentine discs were prepared by horizontal sectioning through the middle coronal third of freshly extracted non‐carious third molars. After the removal of the pulp the discs were finished with 600 grit and divided into three test groups and one control group (n = 10). For the test groups three different laser power settings were chosen: test group A: 3 × 60 sec, 60 mJ; test group B: 3 × 60 sec, 90 mJ; test group C: 3 × 60 sec, 120 mJ. No laser treatment was performed on the control group. In a two‐chamber system the filtration rate of dentine tubules from an exactly defined area of the specimens was measured using a radioactive Ringer solution under a pressure of 30 cm H2O. Permeability measurements were carried out three times prior to lasing, three times immediately following laser treatment and six times after the application of phosphoric acid. Analysis of variance showed a significant influence of the Nd:YAG laser treatment on the permeability of dentine (P < 0.001). The mean quotient of non‐treated control vs. lased dentine was 2.19 ± 0.86 for the 60 mJ beam, 1.49 ± 0.88 for the 90 mJ beam, and 204 ± 2.17 for the 120 mJ beam. Etching the lased surfaces had a statistically significant influence on the permeability of the dentine only in the 60 mJ group (P < 0.001). The data show that the Nd:YAG laser treatment often increases the permeability of smear layer covered dentine but moderates the increase of permeability after etching the surface with phosphoric acid.

Permeability of dentine after Nd:YAG laser treatment: an in vitro study.

The purpose of this investigation was to determine the effects of Nd:YAG laser treatment on the permeability of dentine. Forty dentine discs were prepared by horizontal sectioning through the middle coronal third of freshly extracted non-carious third molars. After the removal of the pulp the discs were finished with 600 grit and divided into three test groups and one control group (n = 10). For the test group three different laser power settings were chosen: test group A: 3 x 60 sec, 60 mJ; test group B: 3 x 60 sec, 90 mJ; test group C: 3 x 60 sec, 120 mJ. No laser treatment was performed on the control group. In a two-chamber system the filtration rate of dentine tubules from an exactly defined area of the specimens was measured using a radioactive Ringer solution under a pressure of 30 cm H2O. Permeability measurements were carried out three times prior to lasing, three times immediately following laser treatment and six times after the application of phosphoric acid. Analysis of variance showed a significant influence of the Nd:YAG laser treatment on the permeability of dentine (P < 0.001). The mean quotient of non-treated control vs. lased dentine was 2.19 +/- 0.86 for the 60 mJ beam, 1.49 +/- 0.88 for the 90 mJ beam, and 2.04 +/- 2.17 for the 120 mJ beam. Etching the lased surfaces had a statistically significant influence on the permeability of the dentine only in the 60 mJ group (P < 0.001). The data show that the Nd:YAG laser treatment often increases the permeability of smear layer covered dentine but moderates the increase of permeability after etching the surface with phosphoric acid.

Origin of shrinkage, distortion and fracture of photopolymerized material

The influence of different laser power settings and layer pitches on the mechanical properties, microstructure and stability of parts built via ultraviolet (UV) laser scanning and subsequent post-curing under an intense UV light was investigated. It was observed that both UV power during scanning and the thickness of the layer have a strong influence on the mechanical properties and shape stability of the parts. Microstructural observation shows that two types of defects are generated during laser UV curing. The first type is the gas hole which is formed from air bubbles. It normally appears elliptical in shape. The second type is the cavity in which uncured resin can be found. Cavities can normally be observed at the upper last scanned layers of a cured specimen. They are associated with low laser power setting and/or large layer pitch. Measurements taken from the experiment indicate shrinkages appearing in two different directions.

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

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. 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. 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 approximately 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. 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.

Optical Properties of Diamond-Like Carbon Films Deposited by Laser Ablation

ABSTRACTVarious optical techniques, including Photothermal Deflection Spectroscopy (PDS), ellipsometry, and transmission measurements, have been used to examine the optical properties of diamond like C films deposited at various laser power densities on Si and fused quartz. The absorption coefficients of these films are typically above 5 × 104 cm−1 throughout the visible part of the spectrum, decreasing quasi-exponentially in the infra-red. Larger sp2/sp3 bonding ratios caused by deposition at lower laser power settings noticeably increase film absorption coefficients. While Tauc plots of our absorption data yield bandgaps of 1.5-1.0 eV, the quality of these fits is unimpressive and the slopes are unphysically low. Rather than modelling these materials as narrow gap semiconductors, we have pursued another avenue: treating the films as a mixture of small graphitic particles embedded in a diamond, sp3-like matrix. We will discuss the results of this approach as well as the evolution of the optical properties after thermal anneals.

The relationship of different power settings and fiber geometries to thermal tissue damage created by the superpulse Nd:YAG laser

We attempted to quantify the amount of thermal damage that was created to surrounding tissues when an incision was made with the superpulse neodymium:yttrium-aluminum-garnet (Nd:YAG) laser with the optical fiber in contact. Light micrographic studies of several incisions, at different laser power settings and with different fiber geometries, were made in the anterior abdominal wall of 16 Sprague-Dawley rats. The specimens were collected immediately postoperatively and at 48 hours postoperatively. Several laser power settings (2–50 W) and seven different optical fiber geometries were studied. The micrographs showed minimal damage (<0.1 mm) to surrounding tissues at all laser power settings in both the immediate and the 48-hour studies. The superpulse Nd:YAG laser with optical fiber contact limited laser thermal damage to the surrounding tissues to less than 0.1 mm in the range of power settings studied. Higher power settings minimally increased the damage. The geometries of the optical fiber created no significant alteration in thermal damage. The results suggest that the superpulse Nd:YAG laser creates both thermal and photodisruptive effects in tissue.

Characterization of tissue effects produced by the Prolase II lateral‐firing neodymm:YAG laser fiber in the canine prostate

The immediate and long term-effects of neodymium:YAG laser treatment with the ProLase II lateral-firing laser fiber in the canine prostate were evaluated. Fourteen male dogs, aged 3 years and older with established benign prostatic hyperplasia, underwent endoscopic ablation of the prostate using the ProLase II fiber. Subjects were treated at laser power settings of 60 watts (6 dogs), 75 watts (4 dogs), or 90 watts (3 dogs), with a mean total energy delivery of 15,000 joules. One dog underwent a sham procedure and served as a normal control. Prostates were examined grossly and histologically at 48 hours, 2 weeks, 4 weeks, or 8 weeks post-treatment. The cross-sectional diameter and volume of tissue ablation were measured in each prostate. Histological studies of the extent of thermal injury to the prostatic tissue and the course of healing of the prostatic urethra were performed. The mean cross-sectional diameter of tissue ablation was 28.6 +/- 4.7 mm and mean volume of tissue ablation was 8.2 +/- 5.1 cc. No statistically significant difference in diameter or volume of tissue ablation was noted between varying power settings. Histological studies showed extensive tissue necrosis with hemorrhage and an acute inflammatory cell infiltrate at 48 hours. By 8 weeks, total resolution of both necrosis and inflammatory changes with complete re-epithelialization of the prostatic urethra was observed.

Laser etching of enamel for direct bonding.

The application of laser irradiation to etch dental enamel in preparation for direct bonding of orthodontic appliances has been studied. Forty extracted human teeth were divided into four groups of 10 teeth. Within each group, five teeth were subjected to a 30 sec acid etch of the buccal enamel surface; the other five in each group were etched with a laser. Four power settings on the laser etching unit were used: 80mJ, 1W, 2W and 3W. After etching, brackets were adhered to the prepared buccal enamel surfaces with composite resin. Shear bond strength was tested 7 days later. The findings showed that an acceptable shear bond strength, viz. > or = 0.6 kg/mm, could be achieved at laser power settings of 1 to 3W but not at the lowest setting (80 mJ). However, the mean shear bond strengths obtained with laser treatment of the enamel at 80mJ, 1W and 2W were lower (p < 0.01 or 0.001) than that achieved with acid etching.

Characterization and minimization of cellular autofluorescence in the study of oligonucleotide uptake using confocal microscopy.

Intrinsic autofluorescent signals can interfere with extrinsic fluorophore signals when living cells are viewed under a confocal laser scanning microscope. The general pattern of this endogenous fluorescence is initially diffuse and cytoplasmic, but it can redistribute and intensify to become punctate and perinuclear as cells age. To reduce the contribution of autofluorescence when tracking the location of an extrinsic fluorophore, such as a fluorescently-labeled oligonucleotide, laser power settings, aperture settings, laser scanning rates, pH buffering environments, and excitatory wavelengths can be modulated. Decreasing laser power settings and aperture sizes, increasing laser scanning rates and excitatory wavelengths, and surrounding cells in a pH buffer all act to delay the signal transformation. In addition, the presence of an exogenous fluorophore can hasten the autofluorescent redistribution and intensification when compared to similar untreated cells.

連続波Nd:YAGレーザーによる接触型経強膜毛様体光凝固の安全性と有用性

We treated 36 eyes with uncontrolled intraocular pressure (IOP) by applying transscleral cyclophotocoagulation with continuous wave Nd:YAG laser. Anterior edge of the probe tip was placed 1mm posterior to the limbus among the circumference. We used laser energy of 1.88±0.44W. The coagulation time was 3.3±0.95sec. The number of coagulation was 18.5±12.8. The IOP decreased from 43.0±15.2mmHg to 29.4±15.2mmHg 6 months after treatment. Complications were minimal. Additional treatment was required in 10 eyes. The success rate (IOPs controlled 25mmHg or less 6 month after treatment.) was 75%in the group of the initial IOP was 40mmHg or less and only 18.8%in the initial IOP was more than 41 mmHg.We conclude that 2W×4sec may be effective and safer as laser power setting in the eyes of which the initial IOP are less than 40mmHg. The eyes with the initial IOP more than 40mmHg should be coagulated by 2.5 to 3.0W for laser power setting. The additional treatment is necessary one month after treatment, if IOP reduction was not enough.

Rat lactotrophs isolated by fluorescence-activated cell sorting are electrically excitable

Lactotrophs (prolactin-containing cells) from the anterior pituitary of the adult female rat were labeled by a cell-surface reaction with anti-prolactin antibodies and then isolated by fluorescence-activated cell sorting (FACS). FACS-isolated pituitary cells were maintained in culture 1–9 days, after which their excitable membrane properties were examined using the whole-cell patch recording technique. Comparisons between lactotrophs sorted at different laser-power settings on the FACS showed that although the electrical excitability of the sorted lactotrophs was acutely altered by exposure to high laser power, excitability comparable to unsorted cells was retained by the use of minimal laser power (10 mW). Recordings were made from 67 cells that had been isolated using the low laser power. These cells had resting membrane potentials ranging from − 22 mV to − 60 mV. More than 80% of the cells responded to depolarizing current injections with regenerative, full-amplitude, overshooting action potentials. Approximately 20% of these cells exhibited spontaneous 20–30 mV fluctuations in the level of resting membrane potential, the majority of which did not overshoot 0 mV. Both the action potentials and the spontaneous fluctuations involved Na + and Ca 2+ ion conductance mechanisms.

A Two-Year Experience with the Neodymium-YAG Laser in Endobronchial Obstruction

In the first two years after the introduction of neodymium-yttrium-aluminum-garnet (Nd: YAG) laser therapy to our practice, 116 patients were treated 176 times. One hundred six patients (91.4 percent) were treated with the flexible fiberoptic bronchoscope. General anesthesia was used in 89.7 percent of treatments; there were four transient anesthetic complications. Three deaths from massive hemorrhage occurred in the first 59 treatments (first 30 patients). After laser power settings were reduced from 90 to 40 W, there were no further incidences of massive hemorrhage or death in the subsequent 117 treatments. The airway caliber was improved in 83.4 percent of treatments. The trachea, mainstem bronchi, and bronchus intermedius airway calibers were improved more often than those of the lobar bronchi. With lower laser power settings, Nd:YAG laser therapy is a safe and effective means of relieving airway obstruction. Thirty-six percent of patients were alive at one year. The median time to retreatment or death was 130 days.