PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Lasers”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources

Laser prostatectomy with the holmium: YAG laser.

Laser prostatectomy has generated considerable interest amongst urologists as an alternative to traditional transurethral resection for the treatment of benign prostatic hypertrophy. The majority of reports available concerning laser prostatectomy have described use of the neodymium: YAG wavelength delivered via contact or non contact fibers. Recently, a new laser wavelength has become available for urologic use. The holmium: YAG laser is a multipurpose device with many potential applications in urology as well as other surgical disciplines. At a wavelength of 2,100 nm, this laser possesses both ablative and hemostatic properties. Energy and frequency settings can be varied by the operator. Using the holmium: YAG laser as well as the neodymium: YAG laser in a combined procedure, we performed laser prostatectomies in 16 patients. In our series we used the holmium laser to vaporize a channel prior to producing quadrant irradiations with the Nd:YAG laser. At 3-month follow-up there was a mean reduction of AUA symptom scores from 19 to 9 and a mean improvement in peak flows from 13.9 to 16.6 ml/s. Early results show clinical effect but the optimal technique of combined holmium: YAG, Nd:YAG laser prostatectomy is yet to be determined.

Aluminum Silicates↗

Occurrence and magnitude of pressure waves during Er:YAG laser ablation of atherosclerotic tissue: comparison to XeCl excimer laser ablation.

BACKGROUND AND OBJECTIVE: Since excimer laser ablation has not shown advantages in comparison to conventional balloon angioplasty, the search for other laser light sources came up with the Er:YAG laser, operating at a wavelength of 2.94 microns. STUDY DESIGN/MATERIALS AND METHODS: Normal and atherosclerotic human vessel segments were irradiated in vitro, using pulsed Er:YAG laser systems. The laser beam was either focused onto the tissue in air or delivered via a fibre system onto the tissue being immersed in saline. Needle-type hydrophones were used for pressure pulse detection. RESULTS: Er:YAG laser irradiation results in effective tissue ablation of normal and calcified atherosclerotic vessel segments. In comparison to excimer lasers, ablation rates can be increased by a factor of 5 to 10 at least. Er:YAG laser ablation is also associated with a generation of pressure waves. On calcified plaque, the acoustic signals differ significantly from those on normal tissue. Histological tissue analysis reveals small zones of discoloration and tissue fissures that are found 100-200 microns lateral to the crater edge, depending on the energy density used. CONCLUSION: Er:YAG lasers generate pressure waves that are comparable to excimer laser ablation. Er:YAG lasers, however, show a markedly improved ablation efficiency, which may favour these systems as effectively cutting, less traumatic tools for removal of atherosclerotic plaque.

Aortic Diseases↗

Laser thrombolysis using long pulse frequency-doubled Nd:YAG lasers.

BACKGROUND AND OBJECTIVE: Laser thrombolysis is a means for clearing blood clots in occluded arteries. Many researchers have studied the mechanisms of clot ablation, and research clinicians have used the technique to treat myocardial infarction with a number of different laser systems. Specifically, a 1-microsec pulsed dye laser has been used clinically to remove blood clots in coronary arteries. As a comparative study, the ablation characteristics of lasers with pulse durations in the ranges of 50-150 microsec and 2-10 msec were investigated. Two frequency-doubled Nd:YAG lasers at 532 nm were used in this study. Ablation threshold and ablation efficiency of gel phantoms and thrombus using these two lasers were measured and compared with the results of the pulsed dye laser. The pulsed dye laser in this study operated at 522 nm. STUDY DESIGN/MATERIALS AND METHODS: Gelatin samples with 150 cm(-1) absorption coefficient at 532 nm and animal clot were confined to 3-mm silicone tubes to measure ablation parameters. Additional samples with 150 cm(-1) absorption coefficient at 522 nm were prepared for use with the pulsed dye laser. A fluorescence technique and photographic bubble detection were used to determine ablation threshold. A spectrophotometric technique was used to determine ablation efficiency. RESULTS: The ablation threshold of the gel phantoms for all three lasers was determined to be 17 +/- 2 mJ/mm(2). Ablation efficiency for the gel phantoms was 1.7 +/- 0.1 microg/mJ. Clot had an ablation efficiency of 2.9 +/- 1.0 microg/mJ. CONCLUSIONS: Ablation threshold and efficiency are independent of laser pulse duration for 1-microsec, 50-150-microsec, and 2-10-msec pulses (P < 0.05).

Animals↗

Acute and chronic effects of transmyocardial laser revascularization in the nonischemic pig myocardium by using three laser systems.

BACKGROUND AND OBJECTIVE: Transmyocardial laser revascularization (TMLR) improves symptoms in patients with coronary heart disease. It is based on the hypothesis of direct perfusion of ischemic myocardium by means of laser-created channels. Three different lasers were used to study alternative effects on myocardium. STUDY DESIGN/MATERIALS AND METHODS: The present study was conducted to evaluate comprehensively and compare the short and long-term tissue effects and the basic interaction mechanisms of CO2, Ho:YAG, and Er:YAG laser radiation with myocardium. The dynamics of laser-induced impacts in gel used as tissue phantom was visualized by time-resolved flash photography. Pressure measurements performed during perforation of myocardium in vitro revealed the explosive character of the ablation process. Channels made into the left ventricle of normal pig hearts were examined immediately and 6 weeks after creation. RESULTS: Regardless of laser source, all channels became occluded within 6 weeks by scar. Minimal acute thermal damage by Er:YAG laser corresponded to smaller scars. Pulsed Ho:YAG caused stronger tissue tearing than continuous wave CO2 irradiation. An increased volume density of intramyocardial vessels was found about the scars 6 weeks after treatment with all lasers. CONCLUSION: The laser sources permitted to study outcome of pressure effects and thermal damage in vivo. There were only minor differences between the three laser systems used. Rapid channel occlusion suggests that rather than revascularization, subsidiary physiologic tissue effects elicited by the thermal, oxidative, or mechanical action of the laser impact may contribute to the beneficial clinical effects of TMLR.

Animals↗

The effect of laparoscopic treatment of polycystic ovarian disease by CO2-laser or Nd:YAG laser.

The feasibility and efficacy of laparoscopic CO2 laser and Nd:YAG non-contact laser application for the treatment of polycystic ovarian disease (PCOD) were evaluated in 30 patients (19 patients treated with the CO2 laser, and 11 with the Nd:YAG laser). The criteria for inclusion of PCOD in our study were: amenorrhea or oligomenorrhea with chronic anovulation, failure to ovulate in response to clomide or human menopausal gonadotropin, elevated serum levels of luteinizing hormone (LH) or an elevated LH/follicle-stimulating hormone ratio, exaggerated LH response to gonadotrophin-releasing hormone (GnRH), elevated serum androgen levels, and ultrasonographic features of polycystic ovaries. Eight pregnancies after CO2 laser and three after Nd:YAG laser were achieved. Decline of serum androgen concentrations was noted in both groups, but was significantly higher in the Nd:YAG laser group (from 3.4 +/- 0.4 ng/ml to 2.2 +/- 0.2 ng/ml). Nine patients checked before and after laser treatment showed a decrease in the characteristically exaggerated pituitary response to exogenous GnRH injection. There were no consistent findings of the pattern in LH pulsatility studied in 5 patients after Nd:YAG laser treatment. Ovarian status was investigated in 11 patients by second-look laparoscopy or cesarian section. There were absolutely no adhesions after Nd:YAG laser coagulation. Filmy adhesions were seen in 3 patients in the CO2 laser group.

Amenorrhea↗

[Selective RPE laser treatment with a scanned cw laser beam in rabbits].

BACKGROUND: Selective RPE laser therapy with sparing of the neurosensory layer is possible by applying repetitive microsecond laser pulses. Macular diseases such as diabetic maculopathy, soft confluent drusen due to age-related macular degeneration or central serous chorioretinopathy were shown to be treated successfully-without concurrent laser scotoma-by this technique. It was the goal of this study to show, if selectivity could also be achieved using a conventional green cw-laser by scanning the beam across the retina during irradiation. MATERIAL AND METHODS: A cw-laser beam at 532 nm was coupled to a slitlamp via a single mode optical fiber. The spot (18 microm) was scanned across the retina of Dutch-belted rabbits through a contact lens using a two-dimensional acusto-optical deflector. The scan-field was 300 microm x 300 microm in size and consisted of six separate scan lines. The scanning speed was adjusted so as to produce 5 micros exposure at each absorber in the center of the scan line. The entire scan pattern was applied 100 times at each site at a frame rate of 100 Hz. Dose response curve was measured by variation of the laser power. ED(50)-thresholds for RPE damage were calculated by fluorescein angiographic leakage in irradiated areas after exposure to different laser intensities. The extent of selectivity was examined by light microscopy. RESULTS: Clinically the selective laser-induced RPE defect was demonstrated by fluorescein angiographic leakage and concurrent absence of ophthalmoscopic visibility. The angiographic ED(50)-damage threshold was 161 mJ/cm(2) (66 mW). Ophthalmoscopic visibility was not noticed even with the maximum available radiant exposure of 438 mJ/cm(2) (180 mW). Thus the safety range between angiographic and ophthalmoscopic thresholds had a factor of at least 2.7. First histological examinations revealed selective RPE destruction with intact photoreceptors for irradiation at laser power levels 2 times above angiographic threshold. CONCLUSION: Selective RPE targeting is feasible with a conventional green cw-laser when scanning the focused laser beam across the fundus with a speed such that every point in exposed RPE is irradiated for duration of 5 micros.

Animals↗

Recanalization of chronic total coronary arterial occlusions by percutaneous excimer-laser and laser-assisted angioplasty.

A low primary success and high restenosis rate after recanalization of chronic total occlusions by conventional coronary angioplasty have encouraged the application of new interventional techniques like excimer-laser angioplasty. In 39 patients with a coronary occlusion for 1 to 12 months, recanalization was attempted by laser angioplasty through a multifiber-catheter coupled to a pulsed XeCl excimer laser. After successful passage of the occlusion by a standard guidewire in 27 patients (69%), the laser catheter was advanced over the central guidewire and crossed the occlusion in 25 patients (64%). In 2 patients with unsuccessful passage of the laser catheter, the subsequent attempt with a low profile balloon catheter also failed. In 19 of the 25 patients with successful laser recanalization, the residual stenosis exceeded 50% and was therefore followed by additional balloon angioplasty. The average residual stenosis after laser was 61 +/- 17% of the vessel diameter, and after balloon angioplasty 28 +/- 9% (n = 19), whereas after laser angioplasty alone it was 38 +/- 5% (n = 6). No complications associated with the laser application were observed. Angiographic control after 24 hours showed a reocclusion of 2 (8%) recanalized vessels. In this pilot study, laser angioplasty proved to be a safe and feasible method for the treatment of chronic total coronary occlusions. Because it was necessary to guide the catheter by a central wire, the primary success was limited by a successful passage of the wire of the occlusion. The rate of stand-alone laser angioplasty has to be increased by future improvements of the technique to enable a comparative evaluation of this method with conventional angioplasty.

Angioplasty, Laser↗

Pulsed excimer laser versus continuous-wave Nd:YAG laser versus conventional angioplasty of peripheral arterial occlusions: prospective, controlled, randomised trial.

Early clinical studies of coronary and peripheral laser angioplasty showed that arterial occlusions could be recanalised by continuous-wave lasers delivered with contact probes and by pulsed lasers applied with multifibre catheters. However, whether laser-assisted angioplasty improves success rates in reopening occlusions and in long-term patency rates is unclear. We have compared the primary recanalisation and long-term patency rates after laser-assisted and conventional percutaneous transluminal angioplasty (PTA) of femoropopliteal artery occlusions in 116 consecutive symptomatic patients (excimer laser 37, Nd:YAG laser 40, PTA 39). Primary recanalisation was achieved in 81 patients (70%). The primary recanalisation rate achieved with the excimer laser was significantly lower than that with the Nd:YAG laser (49% vs 78%, p < 0.01) or with PTA (82%, p < 0.003). The overall angiographic recanalisation rate (primary and secondary recanalisation) after laser and PTA was 89%. After 3 months, clinical improvement was recorded in 76% of patients. Clinical long-term results were available in 94 (91%), and angiographic long-term results in 77 (75%), of 103 successfully recanalised patients. Life-table analysis of the long-term results revealed no significant difference of the restenosis rate between the three treatment groups. The 12-month patency rate was 60% as assessed clinically and 39% as judged by angiography. Primary and secondary recanalisation rates and long-term patency rates were significantly correlated with length of the occlusion. Our results suggest that PTA of femoropopliteal artery occlusions is only indicated if the occlusion is short (< 8 cm) and that laser-assisted angioplasty should only be used after failure of conventional PTA.

Aged↗

Effect of intracoronary saline infusion on dissection during excimer laser coronary angioplasty: a randomized trial. The Percutaneous Excimer Laser Coronary Angioplasty (PELCA) Investigators.

OBJECTIVES: We sought to evaluate whether intracoronary saline infusion during excimer laser coronary angioplasty decreases the incidence of significant laser-induced coronary artery dissections. BACKGROUND: Despite procedural success rates > 90%, coronary artery dissections occur in 17% to 27% of excimer laser coronary angioplasty procedures. Excimer laser irradiation of blood results in vapor bubble formation and acoustomechanical trauma to the vessel wall. Saline infusion into a coronary artery may minimize blood irradiation and consequent arterial wall damage. METHODS: In this prospective, randomized, controlled study, consecutive patients undergoing excimer laser coronary angioplasty were randomly assigned to conventional laser irradiation in a blood medium or to laser irradiation with blood displacement by intracoronary saline infusion. In the patients randomized to intracoronary saline infusion, prewarmed normal saline was injected through the coronary artery guide catheter at a rate of 1 to 2 ml/s using a power injector. The incidence and severity of dissection after excimer laser ablation were evaluated in a core laboratory by angiographers with no knowledge of treatment assignment. The severity of coronary artery dissection was rated on an ordinal scale of 1 to 5. Dissections of grade 2 or higher were considered significant. RESULTS: The mean (+/- SE) dissection grade after laser angioplasty in patients treated with intracoronary saline infusion was 0.43 +/- 0.13 compared with 0.91 +/- 0.26 in patients undergoing laser angioplasty in a blood medium. The incidence of significant dissection was 7% in saline-treated patients compared with 24% in conventionally treated patients (p < 0.05). No significant complications were associated with saline infusion. CONCLUSIONS: Intracoronary saline infusion should be incorporated into all excimer laser coronary angioplasty procedures.

Aged↗

Laser angioplasty of restenosed coronary stents: results of a multicenter surveillance trial. The Laser Angioplasty of Restenosed Stents (LARS) Investigators.

OBJECTIVES: This study evaluated safety and efficacy of excimer laser angioplasty for treatment of restenosed or occluded coronary stents. BACKGROUND: Balloon angioplasty of in-stent restenosis is limited by a high recurrence rate. Debulking by laser angioplasty is a novel concept to treat in-stent restenosis. METHODS: A total of 440 patients with restenoses or occlusions in 527 stents were enrolled for treatment with concentric or eccentric laser catheters and adjunctive balloon angioplasty. RESULTS: Laser angioplasty success (< or =50% diameter stenosis after laser treatment or successful passage with a 2.0-mm or 1.7-mm eccentric laser catheter) was achieved in 92% of patients. Adjunctive balloon angioplasty was performed in 99%. Procedural success (laser angioplasty success followed by < or =30% stenosis with or without balloon angioplasty) was 91%. There was neither a significant difference in success with respect to lesion length, nor were there differences between small and large vessels or native vessels and vein grafts. Success was higher and residual stenosis lower using large or eccentric catheters. Serious adverse events included death (1.6%, not directly laser catheter related), Q-wave myocardial infarction (0.5%), non-Q-wave infarction (2.7%), cardiac tamponade (0.5%) and stent damage (0.5%). Perforations after laser treatment occurred in 0.9% of patients and after balloon angioplasty in 0.2%. Dissections were visible in 4.8% of patients after laser treatment and in 9.3% after balloon angioplasty. Reinterventions during hospitalization were necessary in 0.9% of patients; bypass surgery was performed in 0.2%. CONCLUSIONS: Excimer laser angioplasty with adjunctive balloon angioplasty is a safe and efficient technology to treat in-stent restenoses. These data justify a randomized comparison with balloon angioplasty.

Adult↗

CO2 laser laparoscopic surgery. Adhesiolysis, salpingostomy, laser uterine nerve ablation and tubal pregnancy.

Used endoscopically, the CO2 laser offers some advantages over other operative techniques for endometriosis and adhesions but, in spite of the continuing development of new instrumentation there are still problems with the system. The technique needs specialized equipment requiring ongoing biomedical maintenance and specialized technical care in the operating room. Some problems such as the intraperitoneal accumulation of smoke, gas leakage, and difficulty with maintenance of proper beam alignment still occur. In spite of these problems the advantages are numerous: the system allows precise bloodless destruction of diseased tissue and eliminates the risks of cautery. In the hands of an experienced laparoscopist, it appears safe and effective in vaporization of endometriotic lesions, utero-sacral neurectomy, adhesiolysis and salpingostomy. The judicious use of these techniques, combined with carefully planned further investigations by well-trained and experienced laparoscopists and continuing improvements in the delivery systems, will soon reveal the true efficacy of the CO2 laser laparoscope. If studies continue to show pregnancy rates and pain relief to be equivalent to those patients treated by laparotomy, CO2 laser laparoscopy will become the preferred procedure for the management of pelvic endometriosis and its associated adhesions, distal tubal occlusion, pelvic pain and tubal pregnancy. With the exception of using the argon laser to treat endometriosis, the selective absorption characteristic of lasers has not been greatly utilized. While the CO2 laser is heavily absorbed by water and hence vaporizes most cells in a rather indiscriminate fashion, this is not true for other wavelengths, such as argon, Nd-YAG, KTP, krypton, xenon, copper and gold vapour lasers. The energy form of each of these lasers has different properties of penetration, absorption, reflection and heat dissipation. Many of these lasers have not yet been evaluated in human subjects. An exciting, although not new, area of possible laser application involves the use of photosensitizers and fluorescing agents (Dougherty et al, 1978). Some recent experimental studies (Schellhas and Schneider, 1986; Schneider et al, 1988) may lead to new therapeutic possibilities. The surgical laser is not, however, a panacea. Only controlled trials carried out carefully over the next few years will clearly define its potential. In the meantime it is incumbent upon all of us to investigate the clinical, gynaecological and surgical applications in a careful, methodical and scientific manner.

Female↗

Transmyocardial laser revascularization: effect of laser parameters on tissue ablation and cardiac perfusion.

Dr. Mahmood Mirhoseini from Milwaukee, WI, transformed transmyocardial revascularization (TMR) into transmyocardial laser revascularization (TMLR) more than 2 decades ago. The controversial nature of this laser procedure and the prospect of its successful application to refractory cases of chronic debilitating angina have created spirited interest in TMLR. As a natural component of this interest, various laser modalities have been proposed and employed during the performance of the TMLR procedure both in the experimental and the clinical setting. However, it is the nature of laser-tissue interactions that is primarily responsible for the long-term fate of the channels, the angiogenesis that occurs in the vicinity of these laser channels, and the resulting increase (if any) in myocardial perfusion. These interactions with tissue are, in turn, determined by laser variables such as photonic absorption and scattering by the target tissue, pulse energy and duration, and the peak power generated. The CO2 laser has the advantages of producing high-energy pulses that create a transmural channel with a single pulse, low-peak power that minimizes structural tissue trauma, and high photonic absorption to minimize thermal damage. The holmium:YAG and excimer lasers, in turn, have the advantage of being coupled to a fiber optic catheter for transluminal endocardial delivery. Importantly, long-term clinical and perfusional data showing a cause and effect relationship between the use of TMLR and these end-points are available for the CO2 laser only. Prospective randomized trials are, therefore, warranted to delineate the use of each laser modality in relation to that of the CO2 laser in the TMLR setting.

Coronary Circulation↗

In situ investigation of laser-induced ignition and the early stages of methane-air combustion at high pressures using a rapidly tuned diode laser at 2.55 microm.

The laser-induced ignition of methane/air-mixtures at elevated pressures was investigated by an absorption spectroscopic technique. A room temperature continuous wave InGaAsSb/AlGaAsSb quantum well ridge diode laser was wavelength tuned around 2.55 mum by periodically modulating the injection current from 0 to 174 mA at a 5 kHz repetition rate. The laser heat sink temperature was fixed at 291 K. The infrared laser beam was sent through the pressurized combustion vessel perpendicularly to the igniting laser beam (Nd:YAG laser, 10 ns pulse duration, 20 mJ) at the position of the ignition spark. Fuel-rich to fuel-lean mixtures of methane/air (air equivalence ratio 0.89, 1.06, 1.42, 2.50) were investigated at initial pressures of up to 3 MPa. The initial temperature was 473 K, the volume of the combustion vessel 0.9x10(-3) m(3). The formation of water vapor in the vicinity of the laser spark was tracked by the diode laser. The time resolution of the measurements was 0.2 ms for a total continuous measurement time of up to 1 s. In this way, the laser-induced ignition and its accompanying effects could be investigated on a time scale spanning four orders of magnitude. Apart from the absorbance of water vapor which could be determined semi-quantitatively (due to the effects of severe pressure broadening at high pressures and the ignorance of the exact temperature distribution after ignition), the emissions from the flame (broadband, 1-10 mum) and a gas inhomogeneity index were recorded. The gas inhomogeneity index was obtained by extracting a frequency variable from the time-dependent fluctuations of the transmitted laser intensities and calculating its derivation. The absorbance of water vapor, the emissions from the flame and the gas inhomogeneity index were found to be a powerful tool to characterize laser-induced ignition. Major implications of in situ species concentration measurements at high pressures for the design and development of high-load combustors are presented.

Air↗

Laser-induced chorioretinal venous anastomosis using combined lasers with different wavelengths.

AIM: To evaluate the effectiveness of combined lasers with different wavelengths in creating chorioretinal venous anastomosis (CRVA) in nonischaemic central retinal vein occlusion (CRVO). METHODS: In this retrospective, noncomparative, consecutive case series, records of all patients with a diagnosis of nonischaemic CRVO who underwent combined laser treatment to induce CRVA and who were followed-up for 6 months or longer were reviewed. RESULTS: Records of 85 patients (85 eyes) were analysed. These patients were divided into two groups. In group 1 (24 cases, 24 eyes), combined lasers with two different wavelengths (argon blue-green laser combined with Nd-YAG laser were used. In group 2 (61 cases, 61 eyes), combined lasers with three different wavelengths (argon blue-green laser combined with krypton red laser and Nd-YAG laser) were used. Functional anastomosis formed in 13 out of 24 eyes (54%) in group 1 and 47 out of 61 eyes (77%) in group 2. In patients with successful anastomosis, visual acuity improved for two or more lines in 49 out of 60 eyes (82%), with the remaining eyes undergoing no change. There were no serious complications. CONCLUSION: The use of three laser wavelengths results in the creation of laser anastomosis and the success rate may be higher than when using two wavelengths alone.

Adolescent↗

Combined CO2/erbium:YAG laser resurfacing of peri-oral rhytides and side-by-side comparison with carbon dioxide laser alone.

BACKGROUND: Laser resurfacing of facial rhytids has become a popular treatment option for many patients with wrinkles, photoaging, and acne scarring. Laser wavelength options and optimization of techniques continue to evolve in an attempt to shorten the healing phase associated with laser skin resurfacing. OBJECTIVE: To prospectively study the clinical effects of pulsed carbon dioxide (CO2) laser resurfacing of facial rhytids used alone, compared with a combination of CO2 and the pulsed Erbium:YAG (Er:YAG) laser. METHODS: Forty treatment sites on 20 patients were randomized and evaluated following treatment of the upper lip region with a combination of CO2 laser resurfacing alone or with the same CO2 laser treatment followed by 3 passes with the Er:YAG laser. Patient diaries were maintained to assess erythema, crusting, pain, itching, swelling, pigmentary changes, and the day of first make-up application. Blinded objective grading of improvement was independently assessed by 4 blinded observers at time intervals 3, 6, and 10 days, and 1, 2, and 4 months. Chromometer measurements of erythema were also analyzed and percentage moisture recorded. RESULTS: Subjectively, all patients reported, on average, 10 days of redness and 2.4 days of pain, with no significant difference noted between the two procedures. On average, patients were able to apply make-up 5.5 days postoperatively, regardless of which procedure used. However, the combined CO2/Er:YAG laser treatment patients experienced reduced duration of crusting, compared to the patients treated with CO2 alone. The duration of crusting was reduced on average from 7.4 to 6.5 days, and also the duration of itching was reduced in patients receiving combined treatment from 5.5 to 4.8 days. Chromometer measurements noted no significant difference between techniques in the rate of resolution of erythema. Blinded objective grading revealed that crusting was reduced on average from 7.2 to 6.0 days, and swelling was reduced from 6.3 to 6.0 days in patients receiving the combined procedure. No cases of permanent hyperpigmentation, hypopigmentation, or scarring occurred in any patients. CONCLUSION: The addition of the Er:YAG laser following CO2 laser resurfacing reduces the duration of crusting, swelling, and itching postoperatively. Medium to deep (Grade III) facial rhytids were improved by 70% with both procedures with no significant difference noted between techniques.

Adult↗

[Holmium:YAG infrared laser and UV-Excimer. Laser effects on oral mucosa].

The in-vivo tissue ablation characteristics of a pulsed infrared laser (Holmium:YAG, lambda = 1980) and a pulsed excimer laser (XeCl, lambda = 308 nm) were studied. The holmium laser energy was coupled into nylon fibres. The excimer laser energy was coupled into quartz fibers. Laser incisions were made on white rats at different sites of the tongue. Power settings of 400 mJ per 2.5 microseconds pulse at 5 pulses per second for the holmium:YAG laser and 250 mJ per 1 microsecond pulse at 20 pulses per second for the excimer laser were used. Thermal gradients following laser application were measured. Excellent control of depth of tissue ablation was noted for both types of lasers. The tissue response was examined by light microscopy. Histological studies revealed tissue defects with clean contours. The coagulative necrosis zone for the 400 mJ holmium:YAG injuries measured from 370 microns to 640 microns, compared with 40 microns to 160 microns with the 250 mJ UV-excimer injuries. Wound healing was studied over a six-week period. Histologically, wound closure was completed after four weeks showing re-epithelialization without scar formation for both types of laser. The in-vivo tissue ablation characteristics and the operation reliability of the two lasers were compared.

Animals↗

Laser etching of enamel for direct bonding with an Er,Cr:YSGG hydrokinetic laser system.

Irradiation of enamel with laser energy changes the physical and chemical characteristics of the enamel surface, and these alterations hold promise for the conditioning of enamel for bonding procedures. This laboratory study examined the influence of laser irradiation of enamel at 2 different power settings with an erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) hydrokinetic laser system (Millennium System, Biolase Technology, Inc; San Clemente, Calif) on the shear bond strength of orthodontic appliances and compared these with that of acid-etching. The prepared surfaces of 40 noncarious, intact, extracted premolars were exposed to laser energy: 20 teeth at 2-W setting (5.6 J/cm(2)) and 20 teeth at 1-W setting (2.7 J/cm(2)) of the commercial laser unit. Twenty teeth were etched with 37% orthophosphoric acid. Brackets were bonded with an orthodontic no-mix adhesive, and shear bond strength was determined with a universal testing machine. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests. Etched and restored surfaces of an acid-etched tooth and a 2-W laser-irradiated tooth were examined with scanning electron microscopy (SEM). Laser treatment under 2 W resulted in bond strengths of 7.11 +/- 4.56 megapascals (MPa), which was not significantly different from that of acid etching (8.23 +/- 2.30 MPa). Laser irradiation at 1 W resulted in bond strengths of 5.64 +/- 3.19 MPa, which was significantly different from that of acid etching (P <.05). However, large SD and coefficient of variation values of both laser groups made reliability of this method as an enamel conditioner questionable. Scanning electron microscopy studies of the restored irradiated surfaces showed good surface characteristics, whereas the lased surface was still more irregular than the restored acid-etched sample. Although laser devices are effectively used in some other areas of dentistry, enamel conditioning with an Er,Cr:YSGG laser cannot be considered a successful alternative to the conventional methods of increasing bond strengths to enamel.

Acid Etching, Dental↗

Laser irradiation of bone: III. Long-term healing following treatment by CO2 and Nd:YAG lasers.

BACKGROUND: Relative few reports exist concerning healing of laser created osteotomies over an extended period of time. The purpose of this study was to evaluate long-term healing, from 21 to 63 days, of osteotomy defects in the rat tibia created with the Nd:YAG and CO2 in the presence of a surface cooling spray of air/water. METHODS: The experimental model consisted of 15 large Sprague-Dawley rats. Six treatment modalities were randomly distributed among 6 tibial recipient sites: 1) a negative control (no treatment); 2) a positive control (bur osteotomy); 3) CO2 laser at 5 W (860 J/cm2); 4) CO2 laser at 6 W (1,032 J/cm2); 5) Nd:YAG laser at 5 W (714 J/cm2); and 6) Nd:YAG laser at 7 W (1,000 J/cm2). All laser irradiation was delivered in the presence of a surface coolant consisting of air (15 psi) and sterile water. Five animals were sacrificed at each of 3 time intervals: 21, 35, and 63 days post-treatment. Multiple histologic sections from each treatment site were examined by light microscopy using hematoxylin and eosin Goldner's trichrome stains, and polarized light and evaluated for presence of a char layer, heat induced cracking, heat related alterations in cells or tissue matrix, and osseous regeneration. RESULTS: Healing was severely delayed in all laser treated sites compared to positive control sites. Of the laser treated sites, those irradiated by CO2 laser at 5 W (780 J/cm2) exhibited the greater amount of bone regeneration. At best, however, only a small percentage of sections from any of the laser treated specimens showed evidence of bone regeneration within the ablation defect regardless of the post-treatment time interval. CONCLUSIONS: Under the conditions of this study, the osseous healing response was severely delayed by CO2 and Nd:YAG laser irradiation of bone, even in the presence of a surface cooling spray of air/water.

Air↗