Surgery on the paranasal sinuses is well documented as far back as 2000 years ago. Old and new world tribes performed ritualistic as well as minimally therapeutic trephinations on the sinuses. There was no great understanding of the nasal or sinus anatomy or physiology until the 16th Century when the sinuses were first treated as a primary site of infection. External and internal curettage approaches, along with irrigating the sinuses through their natural ostia, were the mainstay in treating sinus disease. With the introduction and improvement of sinus radiography and continued research in the physiology of the sinuses, a better understanding was gained of the extent of sinus disease, the number of sinuses involved, and the roll of residual disease in the sinuses.

Cadaveric human temporal bones, cadaveric rabbits, and live rats were used to demonstrate the use and safety of the erbium:yttrium-scandium-gallium-garnet (Er:YSGG) laser for otologic applications: for dissection and precise drilling of bone. The shallow penetration of this wavelength and hence minimal collateral thermal effects spare underlying middle and inner ear structures and make it appealing for stapedotomy. Temperature measurements from the round window area during Er:YSGG stapedotomy recorded an elevation of less than 2 degree(s)C, which is well within acceptable limits. Ablation of bone was good and efficient. An acoustic shock produced at the impact site is the major disadvantage and requires further in vivo investigation of the transient and sustained deleterious effects away from the application site. This work supports further investigation into potential applications of the Er:YSGG laser in otology.

This study investigates the value of the Thulium:YAG laser ((lambda) equals 2.01 micrometers ) for otological applications. Fresh human stapes were used. The laser was used at fluences of 64 - 328 J/cm² per pulse in single pulse application with a pulse width of 700 microsecond(s) ec. The energy was delivered through a 300 micrometers fiber. The stapes were irradiated on an acrylic model vestibule with a thermocouple 2 mm below the surface. Perforations were performed at five fluence settings; the peak and sustained temperature rises were recorded. The `open vestibule' was then exposed to direct laser energy above 2 mm lateral to the thermocouple to mimic an open footplate. The stapes were submitted for pathological examination. The laser output had an average pulse to pulse variability of 8%. On average it took 16 pulses to perforate the footplate at the lowest energy and 2 pulses at the highest. There was little charring of the bone. The results are comparable to other mid-infrared lasers.

A technique was developed to secure small mucosal grafts onto the airway wound with fibrin/albumin tissue adhesive mixed with ICG dye and irradiated with a 810 nm diode laser. An in vitro study of the tensile strength produced strong mucosal soldering which was adequate to fix grafts in place. In vivo studies showed that wounds with mucosal grafts were completely covered by regenerated squamous cells in 1 week and by ciliated epithelium in 2 weeks. Excellent healing was observed at 6 and 14 days postoperatively and the histology at 28 days found normal epithelium over the vocal cord lesion. This soldering technique is a less traumatic treatment for patients with extensive lesions of the larynx of various origin. Diode laser soldering with ICG-doped fibrin tissue adhesive was evaluated in tracheal anastomosis as a substitute for absorbable sutures. In vitro studies demonstrated strong anastomoses with minimal tissue damage. In vivo animal study showed that these anastomoses had less fibrosis and tissue damage than control animals repaired with sutures only.

The carbon dioxide laser has been used for the first time to change the cartilage's shape. After the laser irradiation the cartilage has the tendency to retain its new form. Different types of laser modified cartilage structures were studied. The inferred physical mechanism for cartilage shaping using the stresses relaxation process is presented. The clinical significance of the results for corrective laser surgery is discussed.

The `SwiftLase' CO₂ laser flash-scanner technology for char-free ablation of tissue combined with a dedicated oral pharyngeal handpiece and a 30 W power CO₂ laser provide an ideal tool for the performance of staged laser assisted uvula palatoplasty (LAUP) and tonsil cryptolysis in the office. LAUP is virtually painless and enables the treatment of non apneic snoring problems in three to five 10 minute office sessions under local anesthesia. The addition of flexible CO₂ laser fiber delivery systems extends the use of the office CO₂ laser to nasal cavity procedures such as turbinate shrinking.

Functional endoscopic sinus surgery (FESS) utilizing laser energy delivered by optical fibers shows promising results. Due to high absorbance in tissue, pulsed CO₂ laser energy (10.6 micrometers ) has the theoretical advantage of causing minimal damage to the area surrounding the spot of vaporized tissue. However, conventional optical fibers are not capable of transmitting in this mid IR region. Unclad optical fibers made by extrusion of silver halide crystals are capable of transmitting CO₂ laser energy but their 0.9 mm diameter and output beam divergence results in less than desirable power density. We recently developed a silver halide optical fiber consisting of core and cladding, which can transmit CO₂ laser energy with lower divergence and an increase in the power density delivered to tissue. This preliminary study presents the histological effects on tissue of CO₂ laser energy, delivered through a clad silver halide optical fiber. Higher ablation rate and less circumferential damage to tissue have been observed.

Prior to the development of the stapes replacement prosthesis in the early 1950s, loss of hearing due to otosclerosis remained an untreatable disease. Today, loss of hearing due to otosclerosis can be restored in the majority of cases to near normal levels. Since 1980 the laser has played a major and important role in otosclerosis surgery. This paper explores the use of lasers for hearing restoration and compares the results of laser surgery to non-laser surgery.

Spatial and temporal coherence are properties of laser light we studied for some time as responsible for biophysical phenomena, capable of significant contributions in the treatment of chronic inflammatory lesions. In this paper we present the results of five years experience in the application of CO₂ low power laser (LPL) therapy as a new means of treating chronic pharyngitis. Based on our previous studies, we selected 85 patients with nonspecific chronic pharyngitis to be treated at our laser unit. The patients were grouped as follows: Group I, 40 patients, predominance of hyperemic aspect; and Group II, 45 patients, predominance of hypertrophied aspect. Both groups were submitted to low power irradiation of CO₂ laser in eight to ten sessions, one week interval according to the evolution of symptoms. The good results obtained lead us to conclude that this new application for LPL is very suitable for systematic treatment of chronic pharyngitis: a very common and disturbing symptom for a great number of ear, nose, and throat patients, still lacking an effective form of therapy.

Photodynamic therapy (PDT) has the potential to treat and cure early carcinomas of the head and neck while preserving normal tissue. Fifty-three patients with neoplasia of the head and neck have been treated with PDT with follow-up to 40 months. Eight patients with T2-T4 carcinomas of the upper aerodigestive tract had a partial response. Eighteen patients with CIS and T1 carcinomas of the larynx obtained a complete response and are disease free. Eleven patients with T1 carcinomas of the tongue, floor of mouth, and nasal cavity obtained a complete response. Three patients with mucosal melanomas of the nasopharynx obtained a complete response and remain disease free. Two patients with Kaposi's sarcoma or the oral cavity were treated, one obtained a complete response. Five patients with juvenile laryngotracheobronchial papillomatosis obtained a complete response, but all recurred within six months of treatment. PDT is a promising therapy for treatment of early neoplasia of the head and neck. There are, however limitations to this treatment based on tumor size and site. Methodology, clinical response, limitations and complications are discussed.

Five hundred and fifty-one cases of nodules in the vocal cords were treated by a He-He laser. To study the cure mechanism following experiments that were the examination of immune function the test temperature, the examination with indirect laryngoscope, the study of microstructure in the larynx, the test attenuated bacteria, and examination of the lipid peroxide were performed. It was demonstrated that the mechanism was able to make the temperature of the larynx rise, the blood vessel expansive, and hemocirculation rapid so as to increase local nutrition and immune function, accelerate the membranous growth in the larynx, eliminate edema in tissue, and make excretion of inflammatory effusion and poison rapid. The treatment spanned the years 1980 to 1992, the therapeutic effect was good. Study of the cure mechanism following the experiment was performed.

A new flexible handheld delivery system for the Erbium:YAG laser has recently been developed. We studied the ability of this system to deliver energy levels sufficient to cut human cadaveric femoral condylar bone and meniscal tissue, and evaluated the histologic effects and quality of those cuts. Furrowing cuts were made with the 2.9-micrometers Erbium:YAG laser in human cadaveric femoral condylar bone and meniscal tissue. Multiple cuts were delivered through a flexible handpiece with a focusing tip using five different energy settings ranging from 200 mj to 1000 mj at 10 Hz. The tissue samples were fixed and stained with HE and Trichrome. Microscopic analysis was completed and data is reported as direct measurements of histologic damage based on differential staining characteristics. This study shows that sufficient energy to cut cartilage and bone can be delivered through a flexible handheld device. The cut surfaces showed outstanding quality and minimal tissue damage, especially when compared to the Ho:YAG, Nd:YAG, and the CO₂ lasers, none of which adequately cut bone at the present time.

A primary interest of current medical technology is to create instruments that facilitate safe and precise surgical interventions. Conventional surgical instruments have thermal necrosis, aerosolized particle release, access, and depth control limitations. The development of laser systems for bone surgery offers an alternative to conventional instruments and techniques. The mid-infrared erbium laser has demonstrated its ability to ablate bone tissue with minimal damage and postoperative complications. The purpose of this study was to determine the bone cutting ability of a 2.8 micrometers erbium laser when used in a thermally controlled environment.

Joint injury often involves a stretching or loosening of the supporting ligaments. This joint laxity can be increasingly deleterious over time and may lead to osteoarthritis. Decreasing joint laxity is a clinical goal of ligament reconstructions. No study has addressed the possibility of tightening ligaments by heat. This pilot study examined the mechanical and histological effects of the shrinkage of human ligaments.

The ablation of ex vivo human samples of meniscus using the pulsed holmium:YAG (Ho:YAG) laser was studied. Delivery was by optical fiber in contact with the tissue. The rate of ablation was determined as (mm/pulse) for a range of pulse energies. Ablation with tissue in air versus under saline yielded similar rates of ablation, with the under-saline rate slightly higher. Experiments with two optical fiber sizes (200 micrometers and 600 micrometers ) suggested that total pulse energy [J/pulse] rather than radiant exposure [J/cm²/pulse] may be the better predictor for ablation rate. For comparison, results of a study of continuous Nd:YAG laser ablation of chicken breast using two beam sizes are also presented which suggest that total beam power [W] rather than irradiance [W/cm²] may be the better predictor for ablation rate. Comparison with the efficiency of simple boiling water indicates that laser ablation (both pulsed and continuous) is only about 10% as efficient as boiling water.

Using a pulsed Holmium:YAG laser at a wavelength of 2.1 microns, the ablation rates and thermal effects were measured on human meniscal cartilage. The penetration rate of a fiber under saline was measured as well as the mass loss in an air environment. Fluences were varied between 167 - 927 J/cm²/pulse for the penetration rate experiment and between 38 - 490 J/cm²/pulse for the mass loss experiment. Ablation threshold was found to be 10.6 J/cm² in air. A double pulsing scheme used to reduce acoustic effects showed equivalent tissue ablation effects. The increases in ablation rates were directly proportional to the increases in pulse fluence for both methods. Histologic examination showed the lateral thermal change to be a maximum of 600 microns in air at 24 pulses per second.

We report effects of applying variable doses of Holmium:YAG laser energy to bovine articular cartilage in vitro. The response of the cartilage to the Holmium:YAG laser energy was determined by quantification of cell proliferation and extracellular matrix glycosaminoglycan synthesis. This study demonstrates that articular cartilage cell metabolism was maintained at a normal level following treatment of cartilage at a dose of 0.6 joules/pulse. The laser energy was applied at 10 Hz for 10 seconds at 1 mm distance from the cartilage. Under these conditions and at a dose of 0.6 joules/pulse, the total energy density was calculated to be 240 joules/cm², assuming minimal loss of energy due to water absorption. Energy levels grater than 0.8 joules/pulse corresponding to calculated energy densities greater than 320 joules/cm² proved harmful to cartilage. Our data demonstrate that low levels of Holmium:YAG laser energy can be applied to articular cartilage under conditions that maintain and/or stimulate cell metabolism.

Broadly tunable cw laser emission is demonstrated at room temperature in the 1.85 - 2.15 micrometers and 2.20 - 2.45 micrometers regions from Tm:YALO solid-state laser with 795 nm diode laser pumping. Also efficient cw laser operation at room temperature is demonstrated from the Er³⁺ in a garnet host at 2.8 microns, which is resonantly pumped with the 970 nm diode laser, resulting in a laser slope efficiency of 36%.

The purpose of this study is to determine the laser related complication rate for shoulder arthroscopy in the initial clinical experience of 50 patients, and to identify potential advantages of laser use in shoulder arthroscopy. Fifty patients spanning ages 25 to 87 were treated. Surgical debridement was selective and conservative creating a smooth post resection rim. In those that included rotator cuff tears, in addition to arthroscopic debridement, a mini arthrotomy and open acromioplasty were performed. Changes in arthroscopic technique due to laser use included no arthroscopic pump use and use of the shaver only when the fiber could not be easily seen with severe synovitis. We found that the hyper-vascular synovium did not need to be resected last, it could be resected at any point during the procedure. Four hundred and 600 micron fiberoptics were used as well as 20 watts average power. Technical advantage of the laser was felt to be the size of the instrument probe and the availability of excellent hemostasis. Complications include one case of arthroscope damage and one case with a broken fiber tip which was removed with a grasper. Long term follow up of these patients is now underway.

Two orthopedic surgeons performed 27 knee arthroscopies on 26 patients using the 1.44 micrometers Nd:YAG. Mean patient age was 52.6 years. Six patients had their entire procedure done using the Nd:YAG alone and 20 had their procedures done using both the laser and a conventional arthroscopic side-shaver. Three patients had an additional knee procedure done immediately following their arthroscopy. The mean operative procedure time was 47.25 minutes (SD equals 14.75). The mean energy setting used was 2.2 Joules/Pulse (SD equals 0.89), mean frequency 16.6 Hz (SD equals 6.4), and mean total energy delivered was 9418.7 Joules (SD equals 6032.5). There were 15 patients with a minimum follow-up of at least 4 weeks (mean 8.26 weeks). The final results showed 35% returned to normal baseline, 43% improved from pre-op condition, and 21% were the same as pre-op. None of the patients were worse. The 1.44 micrometers Nd:YAG has a water absorption coefficient nearly identical to the 2.1 micrometers Ho:YAG, which is currently a popular arthroscopic tool. We conclude that the 1.44 micrometers Nd:YAG is an effective alternative for arthroscopic procedures of the knee.

In the early 1980s selective photothermolysis (SPT) was introduced. As a consequence a class of SPT lasers was developed with particular attention being centered on the removal of disfiguring vascular lesions, including port wine stains. This talk discusses the recently introduced Vascular System from Medical Bio Care, Sweden, also supplied through Derma- Lase. This system produces a variable pulsewidth in the range of 450 microsecond(s) to 10 ms. This range has been identified as optimal as it provides the theoretical possibility of matching laser pulsewidth with the theoretical relaxation time of most vascular lesions. The tunable wavelength includes 585 nm. The clinician can therefore tailor the options to match the characteristics of the individual lesion. Operation with close multiple pulses in a burst is also an option. The system consists of a compact solid state host mated to a unique delivery system.

The outcome of laser tattoo removal is dependent on the type of laser and characteristics of the tattoo. A rabbit model was developed to study the Q-switched ruby laser in the treatment of traumatic tattooing. On the backs of white New Zealand rabbits, three 3 cm patches were dermabraded and dressed with carbon black and antibiotic ointment. After a healing period of eight weeks, pre-treatment biopsies were obtained, and the rabbits were treated with the Q- switched ruby laser at various fluence settings with a pulse width of 34 nsec. At set intervals, further biopsies were obtained and studied with light and electron microscopic analysis, and photodocumentation was performed. Grossly, clearance of the tattooed areas was noted in the laser treated specimens. More effective clearance was observed with higher fluence treatment. No infections occurred, and hair regrowth was noted in all cases, though the rate seemed to be altered by laser treatment.

Fifteen patients with erythematous/hypertrophic scars and eleven patients with post- inflammatory brown hyperpigmentation of scars were treated with flashlamp pump pulsed-dye lasers. The red scars were treated with a wavelength of 585 nm and a pulse width of 450 msec. The brown scars were treated with a wavelength of 510 nm and a pulse width of 300 nsec. The erythematous scars improved an average of 77% after 1.8 treatments, and 46% of these scars had complete resolution of the erythema. The hyperpigmented scars had an average improvement of 80% after 1.5 treatments, and 45% of these patients had complete resolution of the hyperpigmentation. An unexpected benefit of treatment of these scars was softening and flattening of the hypertrophic scar tissue and normalization of the surface of the scar. Repeated treatments were noted to result in cumulative and progressive improvement in all aspects of these scars.

The CO₂ laser has broad clinical application yet also presents a number of practical disadvantages. These drawbacks have limited the success and utilization of this laser in plastic surgery. Flashscanner technology has recently been used for char-free CO₂ laser surgery of the oropharynx, the external female genital tract, and perirectal mucosa. A commercially available optomechanical flashscanner unit `Swiftlase,' was adapted to a CO₂ laser and used for treatment in numerous plastic surgical applications. Conditions and situations that were treated in this study included generalized neurofibromatosis, tuberous sclerosis, rhinophyma, viral warts, breast reconstruction, and deepithelialization prior to microsurgery or local flap transfer and/or skin graft placement. There were no significant wound healing complications. Some patients previously sustained undue scarring from conventional CO₂ laser surgery. Conservative, primarily ablative CO₂ laser surgery with the Swiftlase has usefulness for treatment of patients in plastic surgery including those that were previously unsuccessfully treated.

Limited regions of human stratum corneum were removed by laser ablation using an Er:YAG laser. Immediately after this procedure, an ointment containing 5-aminolevulinic acid (ALA) was applied topically to the laser-treated and surrounding skin. The time-dependent ALA- induced biosynthesis of protoporphyrin IX was measured by fluorescence detection. Fluorescence in the red spectral region was found to occur in the ablated skin regions only. Time-resolved measurements showed the formation of long-lived fluorophores (16 ns) indicating the presence of ALA-induced monomeric porphyrin. Naturally occurring fluorophores (NAD(P)H, flavins, collagen, elastin) possess shorter fluorescence decay times. Therefore, time-gated measurements in the nanosecond region enable the specific detection of ALA-stimulated porphyrin fluorescence by choosing an appropriate time-window. In addition, detection of backscattered excitation light can be avoided. High-contrast video images of ALA-incubated fluorescent areas were obtained using this novel imaging technique.

Topical application of aminolevulinic acid (ALA) is known to lead to enhanced concentrations of protoporphyrin IX (PpIX) in skin tumors versus normal tissue several hours after application. As PpIX is an effective photosensitizer, topical ALA is being used in several clinical trials to treat skin malignancies, with variable success rates to date. As PpIX is highly fluorescent, we have initiated a clinical trial to determine the PpIX distribution in normal and tumor tissue after the application of ALA via fluorescent imaging. Subjects apply ALA topically several hours prior to surgical excision of basal cell carcinomas, and the resulting PpIX distributions in normal and tumor tissue are examined on a macroscopic and microscopic scale. This information allows us to determine the exact degree of correlation between PpIX distribution and tumor tissue, and gain insight into the mechanism for the specificity of PpIX for tumor tissue. In addition, we are exploring the possibility of using the PpIX fluorescence as a guide to the excision of skin tumors.

The average depth of blood vessels in a cutaneous site, either normal or diseased, can be specified by a simple rapid noninvasive optical measurement. An optical fiber spectrophotometer delivers white light via optical fibers to a skin site. The light reflected by tissue scattering and successfully collected by optical fibers is carried to a diode array spectrophotometer for spectral analysis. The reflectance spectrum is analyzed to specify the component of the optical density (OD) spectrum which is attributed to the cutaneous blood. Then the ratio of the OD_{420 nm}/OD_{585 nm} provides a quantitative indication of the average depth of the blood in the skin site. The purple light (420 nm) less easily penetrates the skin to sample the cutaneous blood content than does the yellow light (585 nm). The calibration of the measurement was accomplished by Monte Carlo simulations of measurements on skin with a layer of blood at various depths. In a study of 47 neonates, the amount of blood content ranged from 4 - 12 mg hemoglobin/g tissue (equivalent to 0.8 - 2.4% of the skin volume being whole blood), and the average depth of blood ranged from 250 - 425 micrometers .

Theoretical and experimental analysis of the efficiency of application of 2 micrometers pulsed holmium laser for cosmetic and plastic surgery and dermatology is carried out. Preliminary experiments were carried out on rats. Solid state 2 micrometers pulsed laser was allowed to operate in free running mode with pulse energy up to 1.5 J and pulse repetition rate up to 5 Hz. To deliver emission to the object a flexible quartz fiber without further focusing of 2.5 m in length and 400 micrometers of the core diameter was used. The effect of the different power density emission on the skin was studied. The second stage was the study of the influence of 2 micrometers emission on human skin. The results of the removal of hemangioma, papilloma, telangiectasia, nevus, nevus acantholytic, xanthelasma palpebral, verruca, chloasma, pigmental spots, tattoos, etc. are presented. Precision, simplicity, efficiency, and the high cosmetic effect of these operations is noted.

A histopathological study on the effect of He-Ne laser treatment on the evolution of cat gingiva open wounds is presented. The irradiation initiates first a massive inflammatory cell exudate together with an antiedematic effect after the second postoperative day. A substantial acceleration of the healing process is noted on the sixth day among irradiated tissues as compared to the operated gingiva which still shows, at this period of time, inflammatory exudate and isolated fibroblasts. The persistence of inflammatory exudate and edema among the untreated gingiva seemed to have a delaying effect upon the healing process. The biostimulatory effect of soft laser seems to act photodynamically both at the intracellular level and extracellular millieu, thus promoting the proliferative capacity of fibroblasts and capillary buds formation necessary for a rapid differentiation of connective tissue. The controlled application of He-Ne laser treatment is suggested in dental healing procedures.

Microleakage of composite restorations was examined using an Er:YAG laser and a burr for preparation and bevelling. As can be expected, dye penetration does not depend on the method of preparation, if bevelling is performed conventionally by the burr and acid etching. Replacing the burr by the laser to bevel the margins has no advantage with respect to the microleakage. Further investigations on the basis of a mechanically prepared bevel revealed only minimal dye penetration and high tensile strength for an Er:Y AG laser conditioning of enamel, if an appropriate irradiation pattern is used. From these results the applicability of the Er:Y AG laser alternatively to the acid etching technique can be concluded.

It is understood that if a laser is to replace the dental high speed handpiece it must be able to ablate dental materials which are present in teeth being treated with the laser. It is the intent of this paper to evaluate the effects of the Er:YAG laser on dental composite restorative material concentrating on the etch rate with and without waterspray. Composite dental material is used to form plugs of known thickness and the etch rate of the Er:YAG laser on this material is determined. The results are compared with those obtained from studies of the Er:YAG on dentin and enamel. In these studies the water reduced the efficiency of the Er:YAG laser 15 - 20% on these tissues.

The results of primary comparative investigation of possible application of lasers based on four different Er-doped crystals (YAG, YLF, YSGG, YAP) are presented. The influence of laser wavelength and temporal structure of laser radiation on efficiency of hard tooth tissues treatment is considered. The experimental data on damage thresholds and efficiency of enamel and dentine removal under influence of submillisecond pulses of all four types of lasers are obtained.

Erbium lasers have previously demonstrated their capabilities as dental hard tissue ablators. Phase changes in the crystalline structures of enamel and dentin appear not to have been produced by the erbium 2.94 micrometers laser radiation. However, the detailed ablation mechanism is still not understood. A hypothesis proposed by some authors is that hard tissue removal is in part by a continuous vaporization process and in part by microexplosions. In an attempt to better understand the ablative processes we have employed different observational instruments and techniques to characterize and identify the morphological changes taking place. The purpose of this study was to develop an understanding of the morphological changes of dentin and enamel that occur after ablation with an experimental erbium laser system.

The purpose of this study was to determine histological and ultrastructural modifications produced by an Nd:YAG pulsed laser beam after an in vivo exposure of human molars. Using a Nd:YAG pulsed laser beam delivered by a 600 micrometers optical fiber and concurrent air and water cooling spray, 14 human third molars with artificial first class cavities were exposed at different power levels (6, 7, and 8 W). All the teeth were extracted at different time periods between 10 and 25 days and prepared for histological examination. The results of the histological examination showed no evidence of degeneration or necrosis of the pulpar tissue. Analysis of the dentinal surfaces after exposure demonstrated that the dentinal tubules are completely closed due to the melted dentin. In conclusion a Nd:YAG pulsed laser beam with an air and water cooling spray is safe for treatments of class I decay and no necrosis or degeneration of the pulp was found for laser powers of 6, 7, and 8 W.

Many attempts to introduce computer technology into the field of dentistry have been actively developed. Process prosthetics demands precise qualitative and quantitative estimations of information in dental topography. Procedures of laser holography and coherent optics permit us to carry out noncontactive topographical recording of the surface form of a subject under investigation. In the present study the precise 3D shape measurement of the abutment and other teeth was attempted by using a He-Ne laser displacement meter and a computer controlled scanning system of model teeth.

This in vitro study was undertaken to determine energy levels necessary to produce tubule closure and surface smoothing on dentinal surfaces of human teeth and their resultant temperature increases within the pulpal canals with the Holmium:YAG laser. An optimal working spot size and even absorption pattern were produced by defocusing the laser beam and evaluated by images produced on light exposed and developed photographic paper. The surface effects on dentin were examined by scanning electron microscopy. A thermocouple was positioned in the canals of fresh dissected dog jaws and attached to a recorder which produced a graph of the temperature changes. The in vitro research model for intrapulpal temperatures changes was verified by comparing premortem and postmortem temperature readings. The same protocol was used to evaluate temperature changes in fresh human extracted teeth. In vivo histological studies were conducted to evaluate the effects of HO:YAG laser energy on pulpal tissues. The results of these studies indicate the HO:YAG laser at a wavelength of 2.12 microns can be safely and effectively used for photoconditioning of the dentinal surfaces of teeth in clinical conditions.

In this study the affects of a pulsed excimer laser emitting at 308 nm (XeCl) on enamel susceptibility to artificial caries-like lesions were investigated. Additional effects of fluoride (F) application were also studied and SEC examinations performed. Sixty-four extracted human molar teeth were coated with acid resistant varnish leaving four windows, then sectioned, leaving one window on each tooth quarter. The windows were treated in one of the following ways: untreated (control), or lased, or exposed to 4 min. APF (1.23% F) before lasing, or exposed to 4 min. APF (1.23% F) after lasing. After lasing, microhardness profiles were obtained and SEM was performed. Caries resistance was generally increased at moderate fluences. F application combined with lasing enhanced caries resistance at some parameters. SEM showed effects ranging from minimal to localized effects to extended glazing. Pulsed excimer laser irradiation, especially combined with topical F application can inhibit development of artificial caries-like lesions.

A line-tunable and variable pulselength CO₂ laser system for ablation of dental and bone tissues has been tested. To avoid the undesirable effects of plasma formation, acoustic shock waves and collateral thermal damage to the tissues, we have found an optimum laser pulselength in the 10 - 20 microseconds range. At a fluence of 30 J/cm² and laser wavelength of 10.6 micrometers the ablation depths in enamel (dentin) were 12(18) micrometers and no significant noise was observed. Without water cooling enamel showed no visible color change, while some minimal carbonization of dentin was present even at low pulse repetition frequencies.

The paper investigates the effects of UV laser irradiation on hard dental tissues. 12 sagittal cross sections 1 mm thick of teet extracted have been irradiated with pulsed ArF (A.=193 nm) and XeCl (A.=308 nm) excimer lasers. The beam has been focused to obtain a spot of about 1 mm on the enamel and dentin of the teet. The depth and the internal profile of the holes have been measured with a profilometer and correlated with the number of pulses and beam energy for each wavelength. No cracks were induced by thermal stresses nor preferential concentrations of Ca and F have been evidenced on the enamel and dentin after UV irradiation. These results show that the ablation of hard dental material can be successfully carried out with excimer laser irradiation without heat damage of the underlying tissues.

CO₂ lasers in particular are expected to have many dental applications because the CO₂ laser beam exhibits strong tissue transpirative actions, such as instant coagulation, carbonization, and vaporization, and because its wavelength at 10.6 micrometers is fully absorbed by water so that the ability to make precise incisions with a high degree of safety is excellent, without damaging the deep tissues. However, clinical application of the CO₂ laser has been slowed since a fiber which can conduct the laser beam to the oral cavity has only recently developed. This new fiber is an extremely flexible fiber with a minimum bending radius of 20 mm and utilizes pulse wave modes that have improved the handling characteristics in the mouth, and this has enabled us to apply the CO₂ laser to a variety of periodontal conditions. The aim of this study was to evaluate the effectiveness of CO₂ lasers for the early treatment of inflammation and pain relief of acute periodontitis, curettage of periodontal pockets, healing after excision of gingiva, and early improvement of gingivitis.

Carbon dioxide laser has been used in dental surgery. The existence of healthy teeth, which have pulp vitality needing to be preserved, is observed in a great number of cases. In this work we describe an experimental model which provides the measurement of temperature in pulp chamber `in vivo,' during oral surgeries in which the CO₂ laser beam is applied to gingival tissue. The problems met during the search for the best way to place the thermal probe regarding the diameter and depth of pulp chamber and the thickness of the tissue layer formed by gum and maxillary bone are discussed. We use a thermocouple placed in the pulp chamber of superior canine teeth in dogs. After that, the probe was also placed between gum and dental root. Since the temperature at gingival surface was known, it was easy to determine the rise in temperature at pulp chamber and also to observe the thermal gradient from gum to tissue to bone, thus avoiding pulp damage during laser applications.

In this study we present the results of two techniques in a group of 50 patients with gingival hyperplasia that were treated in the department of buco-maxillary surgery and laser unit. The majority of those patients had no teeth and had an incorrect adaptation of dental prosthesis. The first group (30 patients, 40 to 55 years) were submitted to conventional surgery with local anesthesia. The second group (20 patients, 40 to 55 years) were submitted to CO₂ laser surgery with local anesthesia. We were able to verify that the group treated with CO₂ laser had much less bleeding during laser procedure, had a better tolerance, and required less anesthesia. The immediate post-operative was smoother with almost no complaint of pain since edematous and inflammatory reaction were reduced. Concerning the late post-operative, the group submitted to conventional surgery presented a high degree of recidivous hyperplasia (60%) allowing a poor or no prosthesis readaptation. In the group treated with CO₂ laser the recidivous hyperplasia occurred in only 35% allowing a much better rehabilitation. This comparative study demonstrated more benefits and effective results of CO₂ laser surgery over conventional techniques.

The aim of this study was to determine changes in dental hard tissues after caries selective laser impact. Light and scanning electron microscopic investigations were performed. The effects of a frequency-doubled, Q-switched Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, various repetition rates) on healthy and carious dentin were studied. From the clinical and especially histological point of view, fluences in the region of the second ablation threshold of healthy dentin (3 J/cm²) were most interesting. Furthermore laser impacts with fluences up to 7 J/cm² were studied. Fiber optics ranging in diameter from 300 to 400 micrometers were engaged. Histological examinations of craters in hard tissues were performed without decalcification of samples. Craters in dental hard tissues were sharply cut and followed closely the profile of the illuminating fiber. Crater walls demonstrated only a few microns of surface roughness. Apart from a very tiny zone due to temperature rise, surrounding hard tissues seem to be totally unaffected, anytime, cracks did not occur.

Preparing teeth the operating speed of laser systems is limited by the temperature increase at the pulp. In dentin the absorbed energy generated by a caries selective laser system working in the subthreshold fluence range for healthy dentin is converted nearly by 100% into heat. This heat is partly transferred to the pulp and endangers the vitality of the pulp. The aim of our measurements was to determine the temperature increase in the pulp chamber as a function of dentin thickness between the lasering point and the pulp chamber. The caries selective conditions were produced by a frequency doubled Alexandrite-laser (wavelength 377 nm, fluence 2 Jcm^-2). Freshly extracted, sound human teeth were cut into slices ranging from 0.1 mm to 2 mm in thickness. A miniature bead thermistor measured the temperature on the pulpal side of the tooth slice in corresponding position to the irradiating fiber. Reducing the thickness of the remaining dentin results in an exponential increase of temperature. We examined the influence of fluence and pulse repetition rate on the temperature in the pulp chamber.

The laser-induced in vivo autofluorescence of human teeth was investigated by means of time- resolved/time-gated fluorescence techniques. The aim of these studies was non-contact caries and plaque detection. Carious lesions and dental plaque fluoresce in the red spectral region. This autofluorescence seems to be based on porphyrin-producing bacteria. We report on preliminary studies on patients using a novel method of autofluorescence imaging. A special device was constructed for time-gated video imaging. Nanosecond laser pulses for fluorescence excitation were provided by a frequency-doubled, Q-switched Nd:YAG laser. Autofluorescence was detected in an appropriate nanosecond time window using a video camera with a time-gated image intensifier (minimal time gate: 5 ns). Laser-induced autofluorescence based on porphyrin-producing bacteria seems to be an appropriate tool for detecting dental lesions and for creating `caries-images' and `dental plaque' images.

Dentin from freshly extracted human teeth was exposed to flashlamp pumped Nd:YAG pulses (100 microsecond(s) duration, 50 - 200 mJ/pulse) delivered through a flat cut fiberoptic in contact with the dentin surface. Ablation depth and volume were measured optically and confirmed with electron microscope morphometrics. Ablation depth increased with force applied at the fiber tip up to 5 - 10 g. Above this ablation depths were insensitive to applied force. Craters made in dental stone were deeper and narrower than those made in normal dentin. Ablation depths per pulse and volumes per pulse decrease as the number of pulses increase. This is more prominent for 200 mJ pulses. At 60 mJ the ablation depths are the same from 10 to 100 Hz repetition rates, although qualitative changes (collateral damage) are greater at higher repetition rates. A progressive increase in collateral damage is seen from the 1st through the 200th pulse.

The effects of contact tip, pulsed Nd:YAG ablation of dentin were studied with scanning electron microscopy. Both the fiber tip and the ablation crater were examined. During the ablation process the fiber tip changes shape, loses transmission and melted silica is found at the bottom of the ablation crater. A thin layer of melted dentin covers the crater surfaces. A preliminary model is presented of the morphological alterations and of the many, interacting photophysical process that occur.

Nd:YAG and carbon dioxide lasers are used for a wide variety of soft tissue applications. As clinicians explore hard tissue applications, such as caries removal and surface modifications, questions arise as to the safety of these new procedures. In this study, thermal characteristics of laser application on enamel and dentin were investigated. Infrared thermography was used to evaluate thermal penetration depth, diameter of hot spot, and the extent of thermal perturbation on dentin and enamel surfaces. Scanning electron microscopy was then used to examine the treated surfaces and correlate the results to the thermal measurements. Laser parameters which have previously been reported in applications of Nd:YAG and CO₂ lasers to dentin and enamel were studied. Our results indicate that, in spite of comparable thermal effects, application of the CO₂ laser created unacceptable thermal damage to adjacent tissue.

The purpose of this study was to determine the microhardness and extent of bacterial reduction of contaminated dentin following pulsed fiber optic delivered Nd:YAG laser exposure. Knoop hardness was determined before and after laser exposures from 0.3 to 3.0 W and repetition rates of 10 to 30 Hz. Half the sections were covered with an organic black pigment before laser exposure to evaluate the use of the pigment as an initiator to increase laser absorbance on the surface. Repeated measures design was employed to determine the microhardness of cut and polished dentin sections. Additional dentin sections were sterilized by gamma irradiation and then inoculated with B. subtilis, E. coli or B. stearothermophilus. The contaminated sections were exposed to contact delivered Nd:YAG laser. Cultures were obtained from the dentin surfaces and the colony forming units counted. Increased microhardness was found for all laser treatments above the physical modification. Bacterial reduction was obtained but complete sterilization was not.

The pulsed Nd:YAG laser has been proposed as an alternative to the dental handpiece for caries removal in enamel and dentin. The purpose of this study was to systematically evaluate, in vitro, the process of caries removal and restoration in enamel and dentin. The effectiveness of this device was investigated utilizing scanning electron microscopy to determine the behavior of dentin after laser treatment of artificially created carious lesions in dentin. Histologic sections of extracted teeth after laser treatment and restoration demonstrated successful caries removal and restoration using the pulsed fiber optic delivered Nd:YAG laser as compared to both high and low speed rotary instrumentation. The adjacent enamel and dentin were unaffected by the laser irradiation although slight carbonization was seen on the dentin surface. Thermocouples placed in the pulp chamber during caries removal confirmed previous studies that showed laser parameters up to 1 W and 10 Hz being the same as conventional caries removal in the amount of heat generated which reaches the pulp. The addition of air/water coolant decreased pulpal temperature.

Optoacoustic measurements were carried out in order to obtain better understanding of the ablation mechanisms during the illumination of hard dental tissue by Er:YAG laser radiation. A broadband microphone was used to detect laser generated acoustic waves in the ambient air. Correlation analysis of the laser pulse spikes and the response of the optoacoustic probe indicates that each laser spike ablates the hard dental tissue independently of other spikes. This is in agreement with the model of ablation by means of micro explosions. The optoacoustic signal is observed to be approximately linearly related to the ablation efficiency, and is thus demonstrated to be a good measure of the ablation efficiency. The experiments also show a significant difference in optoacoustic signals obtained during ablation in caries, enamel, and dentin.

We present a novel technique of nerve repair attempting to reduce scarring and improve alignment. A laser solder composed of albumin, hyaluronate, and indocyanine green dye (peak absorbance 805 nm) was used. After applying solder to the anastomotic site, nerve ends can be precisely aligned and sealed in place using an 810 nm diode laser. Transected sciatic nerves in the rat were used as the experimental model. Laser repairs had approximately half the immediate strength of suture repairs (130 vs 280 g/cm²) but comparable strength by 7 days (270 vs 250 g/cm²). There was no dehiscence in either group. Thermal damage was confined to the solder and epineurium. At 90 days there was no difference in nerve conduction values or axon counts in suture or laser repairs. Histology was suggestive of a later stage of regeneration in the laser group. Laser soldering produces increased strength compared with traditional laser welding with less thermal injury.

Microvascular anastomoses on femoral vessels of rats and rabbits were performed by diode laser tissue welding in association with indocyanine green as a photoenhancing chromophore. Satisfactory clinical results were obtained by reducing the number of supporting stays. In this concern, the feasibility of this technique without any stay was demonstrated on rat femoral arteries. A histological examination at 90 days indicated a complete restoring of vessel structures with a wide proliferation of smooth muscle cells and negligible scar tissue.

A method for `welding' bones is being developed. Tensile joint strengths of chicken bones welded in vitro have exceeded one kilogram. Welding was performed with either a Nd:YAG (1064 nm) or a diode laser (820 nm). Light was delivered with an optical fiber held a few millimeters from the bone surface. A solder was developed to assist in the welding process.

We have developed a stent specifically for use in the laser welded anastomosis of small blood vessels (outer diameter 0.8 - 1.2 mm). The stent consists of a core composed of a 50% (v/v) mixture of polyethylene glycol 4000 and polyethylene glycol 20,000. This mixture (PEG 4/20), is covered with a coating of mono/diglyceride. Among the properties of PEG 4/20 is a melting point of 60 - 70 C and a high solubility in water. The glyceride portion of the stent has a melting point of 36.0 - 38.0 C and is insoluble in water. The PEG 4/20 center provides a rigid frame to the stent for easy insertion into the artery, while the glyceride component prevents early dissolution. Upon the application of laser energy, the glyceride coating melts and the PEG 4/20 center remains intact until completion of the anastomosis. Following laser anastomosis, the blood flow through the repaired vessel dissolves the PEG 4/20 center leaving no trace of the stent. We have used these stents successfully in pilot studies utilizing an indocyanine green laser solder with an 810 nm diode laser (gallium-aluminum-arsenide).

The increasing use of indocyanine green (ICG) in tissue solders has prompted us to investigate its properties in aqueous solutions. We have measured the optical absorbance of several ICG solutions over three orders of magnitude of concentration, and have analyzed the data at several different wavelengths. Our data suggest that, first, more than one oligomeric species is present in aqueous ICG solutions (even at fairly low concentrations), and second, that rather than a dimer or trimer, the predominant oligomeric species is an n-mer where n >= 4. Our experiments show that the compounds generated during photodegradation of aqueous ICG are equivalent to those produced during degradation in the absence of light. Our data also confirm that the adsorption of ICG onto human serum albumin (HSA) reduces both aggregation and degradation, but also show that HSA has a finite capacity for this effect. We have used thin-layer chromatography (TLC) to study the nature of the degradation products of ICG. The degradation process is complex, leading to the formation of at least a dozen products.

The mechanism of laser welding between artificial film and airway epithelium was investigated. An expanded-polytetrafluoroethylene (e-PTFE) patch (200 micrometers in thickness) was welded to exised canine trachea using carbon monoxide laser (wavelength 5.4 micrometers ) with contact irradiation method. The power density at the tip of the laser fiber cable was 300 W/cm² and irradiation time was five seconds. This method was designed for closure of a postoperative bronchopleural fistula via a bronchoscope using laser tissue welding. The welded contact surfaces of the patch and the tissue were examined with scanning electron microscope. The surface of e-PTFE showed porous structure. And welded surface of the tissue revealed multiple process. The porous structure of the e-PTFE patch and process of the tracheal epithelium coincided with size. The evidence of its remodeling as cast of the patch surface proved. Strings of e-PTFE fibrils were also recognized among the process. The mechanical anchoring effect was considered as a possible mechanism of laser patch welding of e-PTFE and bronchial epithelium.

Numerical modeling and experimental verification studies were conducted to compare continuous wave Ar, Tm:YAG, and Ho:YAG fusion characteristics in rat intestinal tissues. Spot sizes, powers, and activation times were varied according to laser characteristics. Exposed transected bowel wall was apposed and irradiated to obtain fusion in vivo. Tissue surface temperature distributions were measured with a thermal camera in the 8 to 12 micrometers band for calibration of the numerical models. The lasers were operated at fixed power, duration, and spot size. Experimental results were analyzed histologically to determine the extent of changes in submucosal collagen as indicated by birefringence loss. Modeling studies based on damage kinetics were conducted for the Tm:YAG and Ho:YAG experiments to study the microscale thermal and damage accumulation phenomena. Comparisons between predicted and measured damage boundaries showed favorable agreement.

To determine the relative strengths of various biologic adhesives at several timepoints, we compared thrombin-activated SD (solvent-detergent treated) cryoprecipitate with laser- activated SD cryoprecipitate and a laser-activated, albumin-based glue. Male Sprague-Dawley rats (n equals 79) received four, 3-cm, dorsal skin incisions which were closed with either laser- activated cryoprecipitate, laser-activated albumin solder, thrombin-activated cryoprecipitate, or standard skin staples. The cryoprecipitate was derived from pooled human plasma and was treated with a solvent-detergent process, rendering it free of envelope-coated viruses (i.e., HBV, HIV). An 808-nm diode laser was used to activate each solder with an average duration of exposure of 75 seconds per incision. Animals were sacrificed for evaluation of wound tensile strength and histology at 0 hours, 2 hours, 4 hours, and 4 days. At all timepoints tested, laser-activated solders were significantly stronger than thrombin-activated cryoprecipitate (p < 0.03) and control wounds (p < 0.003). There was no significant difference in tensile strength between the two types of laser-activated solder at any timepoint.

As in other facets of medical science, the use of lasers in veterinary medicine is a relatively new phenomenon. Economic aspects of the profession as well as questionable returns on investment have limited laser applications primarily to the academic community, research institutions, and specialty practices. As technology improves and efficacy is proven, costs should decrease and allow further introduction of laser surgical and diagnostic devices into the mainstream of clinical veterinary medicine.

Medial and lateral aspects of both radiuses were subjected to periosteal transection of nine healthy equine foals. One site per foal was subjected to surgical periosteal transection and elevation under general anesthesia. The remaining three sites of each foal after injection of a local anesthetic received Nd:YAG contact percutaneous periosteal transection. All radiuses were evaluated radiographically prior to periosteal transection and immediately prior to euthanasia. Foals were euthanized at 3 days, 31 to 34 days, and 67 days post-periosteal transection and gross postmortem and histologic examination performed on each site. Radiographically, periosteal proliferation occurred at all the conventional surgery sites and a majority of the percutaneous laser sites by 30 days post-treatment and was present at 67 days. No limb angulations were noted to occur in any of the foals. The conclusion of the study was that Nd:YAG percutaneous laser periosteal transection was successful in producing periosteal obliteration but with a different histologic appearance than that produced by conventional surgery.

Objectives of our project were to determine the affects of Ho:YAG laser energy on canine intervertebral (IV) discs by thermography, and histology. Multiple IV discs in three cadaveric nonchondrodystrophoid spines were treated with 20 J to 180 J of energy and evaluated by thermography and histology. Histologic evaluation revealed thermal affects at all doses including potential acoustic wave affects, increased eosinophilia, carbonization, and in some cases a large defect due to laser irradiation. Laser affects were confined only to the nucleus pulposus and annulus fibrosus with adjacent structures unaffected. In an acute study, two nonchondrodystrophoid dogs were sacrificed after IV discs were treated with 20 - 180 J of Ho:YAG laser radiation, following an extensive dorsal laminectomy to allow placement of thermoprobes in spinal and spinal cord structures. Heating occurred in only the nucleus pulposus and annulus fibrosus with minimal temperature changes in the adjacent structures including the spinal cord.

In this study, visual laser ablation of the prostate (VLAP) was performed on eight mongrel dogs utilizing a cylindrically diffusing fiber attached to a 1.06 neodymium:YAG (Nd:YAG) laser. All dogs received one continuous dose totaling 15,000 J (25 W for 10 min) applied from the vesical neck to the colliculus seminalis. There was no visible hemorrhage from the lasing intraoperatively in any dog. Postoperative recovery was uneventful with no dog experiencing urinary incontinence and only one incident of dysuria with urinary retention during their observation period. Gross and histopathologic examinations of serial sections of the prostate were performed from 2 hours to 7 weeks postoperatively and demonstrated a consistent spherical zone of destruction 2.9 cm (average) in diameter. We believe the simplified fiber placement and complete lack of postoperative complications in this small group of dogs suggest that the cylindrically diffusing fiber offers significant advantage over laterally deflecting fibers for transurethral prostatectomies in the dog.

The most common surgery performed in our clinic with the CO₂ laser is the cutting and vaporization of neoplasms associated with the head and neck, in particular, the squamous cell carcinoma in the cat. A majority of the tumors are malignant and 50% are metastatic at the time of presentation for surgery. Experience has taught us that early detection and removal with the CO₂ laser affords the best prognosis. To date, roughly 100 cases have been treated with the CO₂ laser. The success rate in the dog is not as rewarding as in the cat. Most cases were done with 5 - 10 watts of power continuous or pulsed wave, using a 125 mm or 50 mm handpiece. The laser beam was focused or defocused to adjust for cutting, vaporization, and coagulation. No post-op care of the wounds was recommended. Other small neoplasms in and around the ears, head, and neck can also be removed easily with the CO₂ laser.

The process of photodynamic therapy (PDT) and its application for the treatment of cancer has been reported for veterinary patients(l,2,3,4,5,6). Multiple factors function together in the patient to influence the overall effectiveness of a PDT treatment, including tumor size, location and biology, efficiency of the photosensitizer to produce a cytotoxic reaction, systemic and tumor pharmacokinetics of the photosensitizer, tissue oxygenation, and light dosimetry, All of these factors need to be considered in evaluating a patient for possible PDT treatment, reviewing the design and results of any PDT clinical trial, and in proposing alterations to the approach of the clinical application of PDT where improvement of results is desired. The use of PDT has been reported several times for the treatment of facial, solar-induced squamous cell carcinoma (SCC) in cats. Several of these studies have employed the use of chloro-aluminum sulfonated phthalocyanine (AlPcS) as a photosensitizer, with varying degrees of clinical response, which the authors in each case felt were encouraging for the employment of PDT for this condition in cats. ( 4,5,6) From our clinical experiences in employing AlPcS for this condition in cats and in comparing our experiences to those of others, we are attempting to better understand this disease and the factors which could influence the effectiveness of PDT for its treatment.

Promising results obtained by photodynamic therapy (PDT) with porphyrins on superficial spontaneous canine tumors suggested the experiment of this technique on intracavitary tumors, specifically at the endonasal site. The supposed neoplastic residual bed was irradiated directly during surgery at the end of the debulking. Five dogs referred to the surgical department of the veterinary school, University of Milan and affected by endonasal neoplasias were submitted to PDT after radiologic and cyto-histologic diagnosis and TNM stadiation. All the selected tumors were included in the clinical stage 1 (T1NOMO). Mean and median survival time (from the day of treatment) were 11.6 - 5.4 and 12 months, respectively. Different staging of the treated tumors limits the possibility of an objective comparison with other alternative therapeutic procedures.

The cardiopulmonary affects and the affects on muscular microperfusion of the beta adrenergic agonist, clenbuterol (0.8 mcg/kg intravenously), were investigated in dorsally recumbent anesthetized ponies. Muscle microcirculation was measured by laser Doppler flowmetry, utilizing fine optical fiber probes. Other measurements included heart rate, cardiac output, arterial blood pressure, and arterial blood gas tensions. Clenbuterol injection caused a regular, but transitory rise in muscle microcirculation, an increase in heart rate, and cardiac output and a decrease in mean arterial blood pressure. Clenbuterol did appear to prevent the continuing fall in arterial blood oxygen tensions seen in the treatment groups, but had only minimal affects in reversing the hypoxia already present.

A comparative wound healing study was performed to test the efficacy of using an electromagnetic field focusing device (EFF) as an incisional tool, and to compare it to wounds created using a scalpel, an Nd:YAG laser, and an electrosurgical device. Rabbits were aseptically incised using each modality. The wounds were allowed to heal for periods of 7, 14, and 21 days, and then the tissue was collected for histopathological analysis and tensile strength tests. The results indicated that the scalpel wounds healed faster and with fewer complications. The other three modalities resulted in thermal damage and necrosis that delayed healing.

X rays were used for low energy photon therapy (LEPT) efficacy assessment for cervical lordosis restoration and radial head spur healing. Two cases, their evaluation, and treatment are discussed along with the follow-up results.

The authors describe the results of a series of experiences made to evaluate the interaction in vitro between He-Ne laser light and Staphylococcus aureus. The results confirm the interaction in decreasing energy necessary in relaction with black-white moon and perigee for inducing sensitivity at some antibiotics by Staphylococcus aureus.

Helium-neon laser irradiation (HNLI) is an effective biostimulating agent but its influence on embryonal processes is almost unknown. We have studied fish embryos and larvae development, viability, and growth after HNLI of fish eggs at different stages. With this aim carp, grass carp, sturgeon, and stellared sturgeon eggs were incubated in Petri plates or in fish-breeding apparatuses and were irradiated in situ with different exposures. Then we studied hutchling percentage, larvae survival and growth dynamics, and morphological anomalies percentage. HNLI effect depended on irradiation exposures and intensity, embryonal stages, and fish species. Laser eggs irradiation essentially affected larvae viability and growth in the postembryonal phase. For example, HNLI of sturgeon spawn at cleavage stage or grass carp at organogenesis decreased larvae survival rate. On the contrary HNLI at gastrulation or embryonal motorics stages markedly increased larvae survival rate and decreased the morphological anomalies percentage. We determined most effective irradiation regimes depending of fish species which may be used in practical fish-breeding.

Ten to fifteen thousand new cases of recurrent respiratory papillomatosis (RRP) are diagnosed each year in the United States. RRP is caused by the human papillomavirus (HPV) and is characterized by recurrent, non-malignant, proliferative lesions of the larynx. Patients with RRP undergo numerous microsurgical procedures to remove laryngeal papilloma threatening airway patency and interfering with phonation. The standard surgical technique involves CO₂ laser vaporization of laryngeal epithelium affected by the lesions, and requires general anesthesia. The pulsed dye laser operating at 585 nm has previously been demonstrated to be effective in clearing HPV lesions of the skin (verrucae). For treatment of RRP, the fiber- compatible pulsed dye laser radiation may be delivered under local anesthesia using a flexible intranasal laryngoscope. Potential advantages of the pulsed dye laser treatment over CO₂ laser surgery include (1) reduced morbidity, especially a lower risk of laryngeal scarring; (2) lower cost; (3) reduced technical difficulty; and (4) reduced risk of viral dissemination or transmission. In vivo studies are underway to determine the effect of pulsed dye laser radiation on normal canine laryngeal tissue.

Infrared lasers are the most favored systems for laser micro surgery. The reason is due to the short penetration depth of these emission wavelengths in water. The application of pulsed lasers with sufficient short pulse widths prevents the diffusion of heat from the irradiated volume to the surrounding tissue. Therefore, using pulsed lasers rather than cw-lasers reduces the damage zone significantly. In contrast to the radiation of the CO₂-laser and the Er:YAG laser, there are quartz fibers available for the Ho:YAG laser. These fibers are biocompatible and offer a high spectral transmission and a high laser damage threshold. In paranasal sinus and middle ear surgery both the fiberoptic transmission and the possibility of bone ablation are preconditions for an optimal laser use. Because the beam profile of the laser radiation is determined by the fiber, the question arises for the quality of the obtained incisions and for optimal working conditions.

For many medical applications the well-known advantages of the CO₂ laser cannot be completely used due to the absence of flexible delivery systems. New systems, built up by hollow waveguides, are available for clinical work. Furthermore optical fibers based on silver halides are under development for CO₂ laser radiation. First experimental applications with fibers demonstrate the interesting possibilities of these delivery systems. It is possible to insert a fiber in a flexible bronchoscope and transmit 7.5 W output power.

The HO:YAG laser is a near-contact laser with a capacity to ablate or cut tissues. The ablation function allows the surgeon to remove meniscal tissue, lyse and resect adhesions, melt loose bodies, and dissolve inflamed synovium. The cutting function of the laser is utilized to perform a lateral release or resect torn menisci. The laser can also be utilized to drill holes in Grade IV chondromalacic lesions to initiate a healing response. The laser has been embraced by orthopaedic surgeons because of its shape and versatility. The tip is only 2 mm wide and can be delivered into the tight posterior compartments of the knee with no damaging contact with the articular surfaces. The laser coagulates as it works and bleeding is minimized. The laser can function both as a cutting and ablating tool. The laser can also drill holes into subchondral bone to, hopefully, initiate a healing response.

The impact of using the 2.1 micrometers Ho:YAG laser in orthopaedic surgery has not been fully investigated, especially as to what affect it may have on an employee's return to work and normal activities. In this retrospective review of 140 patients who underwent arthroscopic surgery at our facility, there were found to be significant decreases in time on crutches and time off from work when laser-assisted knee arthroscopies were compared to procedures where conventional mechanical or motorized instruments were used. The patients who had laser-assisted knee arthroscopies discontinued use of crutches 5 days earlier than the conventional group and returned to work 10 days earlier than their counterparts who had undergone conventional arthroscopic surgery. The ability to return to work more quickly translates into significant cost savings for employers who otherwise would have to replace the worker with temporary help, pay overtime, or face lost productivity due to an employee's absence following arthroscopic knee surgery.

Insoluble Type I collagen from bovine Achilles tendon (Sigma C9879) was suspended in a 3 mM solution of the dye diEd66Br dissolved in Cremophor EL^R (BASF) to give a molecular concentration ratio. Fifty-microliter aliquots in 5-mm-diameter wells were exposed to 458 J/cm² (225 mW/cm², 1800 sec) of 457.9-nm light from an argon ion laser; similar aliquots with and without dye were kept in the dark to serve as controls. Following pelleting of the collagen by centrifugation and 3x washing in phosphate-buffered saline, aliquots of light-treated and control sample pellets were (1) digested in collagenase (Sigma C9891) or (2) extracted in 0.5 M acetic acid, followed by centrifugative ultrafiltration (10-kd cutoff) in 0.01 M acetic acid. Aliquots of the supernatant of the acid-extracted collagen also were digested in pepsin. Electrophoretic protein migration in 8% to 25% gradient polyacrylamide gels following SDS solubilization disclosed numerous, densely packed, essentially contiguous protein bands. These studies indicate that the dye and light treatment of insoluble Type I collagen (1) results in cross-linking of collagen molecules and (2) does not denature the trimer conformation sufficiently to enable significant digestion by pepsin.

This is a report of a case study with interesting laser applications. A 7 year old female was referred to us for treatment of hyperplastic tissue. At age two the patient had successfully undergone a liver transplant. She had undergone two periodontal surgeries under general anesthetic for the same soft tissue problem. Other possible complications were chronic sinusitis and frequent headaches. She has allergies to penicillin and sulfa. Her daily medications are Predisone and Cyclosporin. We consulted with her transplant team and they had no contraindication for the proposed dental surgery. The doctor placed her on prophylactic erythromycin for the procedure, as a preventive measure. The patient desired not to have any more general anesthetics administered. Clinical examination revealed electric pulp tests were normal for all teeth tested. No visible carious lesions were observed and there was no need for radiographs at this time. Soft tissue revealed red inflamed fibrous tissue consistent with gingival hyperplasia. Probing demonstrated 4 - 6 mm pockets around the anterior teeth.

Research has shown that CO₂ laser energy can both fuse and etch enamel, the effect being dependent on the exposure parameters utilized. Such energy can also fuse dental porcelains, but it is not known whether porcelain can be etched by CO₂ laser. The objective of this study was to evaluate whether CO₂ laser energy can be utilized to etch porcelain laminates, an effect necessary for resin bonding. Porcelain laminate disks 10 mm in diameter were prepared. The disks were each numbered and divided into quadrants with a small carbide high speed bur. Six disks were utilized, each quadrant receiving a single laser exposure for a total of 24 exposures. Each exposure was at either 10 or 15 W for .01, .05, or .10 seconds, with a focal spot of either 0.8 or 0.35 mm. This range of exposures includes those exposures which cause enamel etching. Two exposures were made at each combination of exposure parameters. Each disk was prepared for scanning electron microscopy and viewed at 75X to examine the exposure sites. All 24 exposure sites were examined and no definite etching was observed.

The effects of Ho:YAG laser energy on articular cartilage and subchondral bone adjacent to traumatically created cartilage lesions in a continuous weight-bearing model were investigated. The 2.1 micrometers wavelength was delivered in hand-controlled contact and near-contact hard tissue arthroscopic surgery in a saline medium. Bilateral arthroscopy was performed on normal antebrachiocarpal and intercarpal joints of four adult horses. One-hundred twenty traumatic lesions were created on three weight-bearing articular surfaces with a knife, curette, or a motorized burr. Depths of the lesions were partial and full thickness. Configurations of the lesions were lacerations, scrapes, and craters. Left limbs were used as controls. Right limb lesions were treated with various intensities of laser energy. Animals were sacrificed at intervals of 1, 3, and 8 weeks. Gross microscopic anatomy was documented, and tissue sections were subjected to blind review by a pathologist. Mankin grading for cellularity and proteoglycan content was used to qualitatively evaluate cartilage response. Cartilage adjacent to all lesions exposed to laser energy had better cellularity and proteoglycan content than corresponding controls by Mankin grading.

Conventional root canal treatments often fail due to insufficient removal of root canal contents and due to ineffective reduction of bacterial growth. In vitro investigations on the 308 nm excimer laser root canal preparation showed excellent results concerning the preparation quality. The aim of the present study was to investigate the influence of 308 nm excimer laserlight on the growth of bacteria. Bacterial suspensions of Staph. aureus, E. coli, and Enterococcus faec. were irradiated with various energy densities and different time duration. In order to exclude thermal side effects the temperature rise inside the suspensions was registered during irradiation. It was able to demonstrate that 308 nm excimer laserlight effects a log reduction of germ concentration at energy densities of 0.5 - 2.4 J/cm². Laserlight effects germ reduction even without tissue removal. The effectiveness is dependent on the type of bacteria, the energy density, and the time of irradiation. The antimicrobial effect is independent from temperature.

This research was designed to ascertain which CO₂ laser exposure parameters result in consistent etching of enamel. Fourteen non-carious teeth were selected and a 2 X 4 gridwork was cut into the buccal surfaces creating eight discrete windows for laser exposures. Four teeth served for the initial pilot project. Two windows were lased at each combination of exposure parameters. Laser exposures were at .01, .02, .05, or.10 sec. at 2, 5, 10, or 15 watts (W) with a model 20C Pfizer CO₂ laser. A 1.0 mm focal spot was used throughout. Following SEM examinations, it became clear that etching occurred only at .05 and .10 sec. at 10 and 15 W. Ten teeth were used for the main project at .05 and .10 sec exposures at 10 and 15 W. Ten windows were lased for each combination of exposure parameters. SEM analysis was accomplished at 100X and 1,200X. Laser exposures of 10/10 at .05 sec./15 W, .10 sec./10 W and .10 sec./15 W resulted in etched enamel. Statistical analysis showed a significant difference in etching between the .05 sec. 10 W group and the higher exposure parameters.

It is well known that fluorescence emission is produced when human dental enamel is irradiated with short-wavelength optical radiation. A limitation to wide acceptance of laser scanning is the scan acquisition time -- often over thirty minutes. This paper discusses a new approach to laser scanning that overcomes the above limitation while preserving the precision of micro-scanning. A surface of a tooth is flooded with laser light and an image of the fluorescence signal is acquired through a narrow wavelength window, typically 10 nm. An electronic optical filter selects the optical window and presents it to a CCD array. Under computer control, images at specific wavelengths can be obtained. By selecting regions which are most sensitive to fluorescence, the optical properties of a tooth surface can be rapidly determined. In the research version, a scanning laser fluorometer, co-aligned with the imaging system, allows precision fluorescence measurements of small regions identified by the imaging system.

Human and bovine enamel samples were irradiated with a pulsed CO₂ laser at (lambda) equals 9.3, 9.6, 10.3, and 10.6 micrometers with 5 - 10 J/cm² pulses of 50 - 500 microsecond(s) duration in order to determine the required energy densities needed to fuse the enamel surface. The resulting temperature rise at the sample surface ranged from 500 to 1500 degree(s)C, as measured by a HgCdZnTe detector. The temperature was significantly higher at 9.3 and 9.6 micrometers than at 10.3 and 10.6 micrometers for the same absorbed energy. Scanning electron micrographs of the irradiated enamel revealed surface changes that were consistent with the surface temperature observations. The temperature rise at the ceiling of the pulse chamber determines the risk of pulpal necrosis. This temperature was measured using thermocouples and a thermal imaging camera for different pulse repetition rates and number of pulses. These results indicate that the more efficient absorption at (lambda) equals 9.3 and 9.6 micrometers may be used to fuse enamel at lower laser energies, therefore requiring less energy, significantly reducing the risk of pulpal necrosis during laser treatment.