Fibrin mixtures are currently under investigation for their ability to stimulate and maintain a reparative response in the avascular portion of the meniscus. A major problem with this technology is the inadequate adhesive strength of conventional fibrin clot mixtures. Argon laser assisted fibrin clot bonding (LAFCB) has been shown to increase the tensile strength of the meniscal-fibrin clot bond over 40 fold; however, LAFCB effect on fibrin clot's ability to stimulate meniscal repair has not been studied. Using in vitro tissue culture, the effects of diode laser energy on fibrin clot's ability to stimulate repair of 2 mm punch hole defects in human menisci is investigated. Four groups were created in each meniscus. Dye enhanced fibrin clot with (group I) and without (group II) exposure to 9.6 watts/cm² of continuous wave diode ion laser energy was used to fill 2.0 mm punch hole defects created in human menisci. Group III consisted of defects with fibrin clot alone. Unfilled defects served as controls (group IV). In vitro tissue culture was utilized to maintain meniscal viability. Specimens were analyzed at weekly intervals for eight weeks. All clots were grossly displaced from the punch hole defects within the first week except those in group I. Histologic evaluation revealed that exposure to diode laser energy stabilized fibrin clot. In no group was fibrochondrocyte migration or proliferation observed. These findings support a possible method of fibrin clot stabilization; however, further work is necessary to identify and overcome obstacles to fibrochondrocyte migration which could obviate the need for partial menisectomy and its subsequent degenerative effects.

PURPOSE: To determine the effects of Nd:YAG laser energy on the healing of full- and partial-thickness articular cartilage defects in canines

Electrosurgical devices and various lasers are used to cut human meniscal tissue, and the amount of thermal damage caused by each method is measured and compared.

This study analyzes the light absorption characteristics of human meniscal tissue. Increased absorption at certain wavelengths of light allows increased energy transfer and the ability to cut or ablate that tissue.

The Ho:YAG laser is used to perform percutaneous lumbar discectomy in swine to evaluate the procedure as a potential clinical tool.

In order to optimize bone and cartilage ablation, various excimer laser systems at 308 nm wavelength (pulse width 28 ns, 60 ns, 300 ns) and tapered fibers (core diameter 400 micrometers , 600 micrometers , 1000 micrometers ) were combined. By varying the major parameters such as fluence, pulselength, repetition rate, fiber diameter, medium, manner of application (drilling, cutting); analysis was made of the interaction of the excimer laser beam with different organic material (meniscus, bone tissue). More than 300 cuts and drillings have been realized with different parameters. The ablation rate mainly depends on fluence, repetition rate and pulse duration. The achieved ablation rate was 3 micrometers /pulse in bone. The drilling speed of the meniscus was 6 mm/s. The samples showed no carbonization at all, when being cut or drilled in liquid medium. This might be a breakthrough in fiber guided excimer laser surgery. From these and further experiments the authors obtained the dosimetry, which will be the basis for the elaboration of necessary operation guidelines for accident surgery.

This study was designed to compare the efficiency and thermal effect of a 135 ns pulsed-stretched XeCl excimer laser (308 nm) and a free-running Erbium:YAG laser (2940 nm) with 200 microsecond(s) pulse duration for ablation of knee joint structures (hyaline and fibrous cartilage, tendon and bone). The radiant exposure used for tissue ablation ranged from 2 to 15 J/cm² for the XeCl excimer and from 33 to 120 J/cm² for Er:YAG. The excimer and Er:YAG lasers were operated at 4 and 5 Hz respectively. The ablative laser energy was delivered to tissue through fibers. Ablation rates of soft tissues (hyaline and fibrous cartilage, tendon) varied from 8.5 to 203 micrometers /pulse for excimer and from 8.2 to 273 micrometers /pulse for Er:YAG lasers. Ablation rates of soft tissues are linearly dependent on the radiant exposure. Within the range of parameters tested all the tissues except the bone could be rapidly ablated by both lasers. Bone ablation was much less efficient, requiring 15 J/cm² and 110 J/cm² radiant exposure for excimer and Er:YAG lasers to ablate 9.5 and 8.2 micrometers tissue per pulse. However, excimer laser ablation produced less thermal damage in the tissues studied compared to Er:YAG at the same laser parameters. The authors conclude that both lasers are capable of efficient knee joint tissue ablation. XeCl excimer laser requires an order of magnitude less energy than Er:YAG laser for comparable tissue ablation.

Polymethylmethacrylate (PMMA) is a compound frequently employed in orthopedic surgery for the fixation of prosthetics and other materials to bone. It is employed for this purpose due to its excellent strength and durability. However, these same properties also make the removal of PMMA very difficult. With this problem in mind, the ablation of PMMA by the Nd:YAG and the THC:YAG lasers was compared. The tip of the optical fiber was placed at a distance to achieve optimal spot size on to pre-weighed blocks of PMMA (Simplex - Howmedica, Rutherford, N.J.). Ablation was carried out with both the THC:YAG and Nd:YAG lasers over a range of powers (5 - 20 watts) and time periods. The amount of PMMA ablated was then determined and compared. Throughout the energy range examined, the THC:YAG laser was more effective than its Neodynium counterpart at the power levels tested. Present clinical application of these lasers in PMMA ablation is limited by technical obstacles.

Purpose: to compare CO₂ laser to mechanical means of PMMA removal in total hip arthroplasty revision surgery. Materials and methods: Forty-five patients requiring hip revision surgery were studied and compared to historical controls. Cement was removed from the femoral canal utilizing a 30 centimeter laparoscope. A CO₂ laser waveguide was passed through the laparoscope into the femoral canal and a TV camera was placed over the eye piece to permit visualization of the depths of the femoral canal on a video monitor. The leg was placed in a horizontal position which avoided the pooling of blood or saline in the depths of the femur. Under direct vision the distal plug could be vaporized with a 40 centimeter CO₂ laser waveguide. Power settings of 20 to 25 watts and a superpulsed mode were used. A 2 mm suction tube was welded to the outside of the laparoscope permitting aspiration of the products of vaporization. Results: Of 45 hip revisions there were no shaft perforation, fractures or undue loss of bone stock. There was no statistically different stay in hospital time, blood loss or operative time between the CO₂ revision group compared to the non-laser revision group, in which cement was removed by mechanical methods. Conclusions: Mechanical methods used in removing bone cement using high speed burrs, reamers, gouges, and osteotomies is technically difficult and fraught with complications including shaft fracture, perforations, and unnecessary loss of bone stock. The authors' experience using the CO₂ laser in hip revision surgery has permitted the removal of bone cement. Use of a modified laparoscope has allowed for precise, complete removal of bone cement deep within the femoral shaft without complication or additional operative time. The authors now advocate the use of a CO₂ laser with modified laparoscope in hip revision surgery in which bone cement is to be removed from within the femoral shaft.

Conventional treatment of ingrown toenails requires ablation of the nail bed by curettage with or without the use of cauterizing agents such as phenol. Despite these measures, incomplete ablation of the ingrown nail does occur, often requiring additional procedures. This recurrence rate is reported to as high as 50% in some series. The purpose of this study is to see if CO₂ partial matricectomies were more effective in treating symptomatic ingrown toenails. In particular, the authors looked at the recurrence rate and infection rate.

The development of efficient high-power lasersystems for use in surgery, especially in arthroscopic fields, leads to a new push for all endoscopic techniques. Both techniques, laser and endoscope, complete each other in an ideal way and allow applications which could not be reached with conventional techniques. One of the newer laser types is the excimer laser, which will be a good choice for surface treatment because of its very considerate interaction with tissue. One example is the ablation or smoothing of articular cartilage and meniscal shaving in orthopaedics. On the other hand, the power of this laser system is high enough to cut tissue, for instance in the lateral release, and offers therefore an alternative to the mechanical and electrical instruments. All lasers can only work fine with effective delivery systems. Sometimes there is only a single fiber, which becomes very stiff at diameters of more than 800 micrometers . This fiber often allows only the tangential treatment of tissue, most of the laser power is lost in the background. New fiber systems with many, sometimes hundreds of very thin single fibers, could offer a solution. Special handpieces and fibersystems offer distinct advantages in small joint arthroscopy, especially those for use with excimer lasers will be discussed.

The CO₂ laser was selected for arthroscopic surgery due to its availability in the hospital high power output and excellent absorption by unpigmented tissues. During the course of this study 4 generations of laser instruments were tested. These include the focused beam delivered via a handpiece the (3 mm O.D.) macrowaveguide the (1.5 mm Q.D.) microwaveguide and the flexible waveguide. The latter two devices complement each other in that the microwaveguide will tolerate and retain up to a 30 degree(s) curve. The flexible waveguide will clear narrow joint tolerances without creating lesions in the articular surface. CO₂ laser arthroscopic tissue ablation must be done under gaseous joint distention but this presents no undue difficulties. At the completion of the procedure saline irrigation must be done for char removal.

Fifteen patients were studied prospectively as a pilot study to evaluate the safety and efficacy of the contact Neodynium: Yttrium Aluminum Garnet (Nd:YAG) laser in performing arthroscopic meniscal resection in a saline medium, (Surgical Laser Technologies; Malverne, PA). All fifteen patients were rated as having clinically excellent results based on pain relief, wound healing, and post-operative swelling. Although there was increased time involved with setting up and calibrating the laser, there was not an increase in time for meniscal resection. In addition, the decreased need for secondary trimming and increased accessibility to the posterior horns of the menisci represent advantages over conventional instruments. Based on the findings, arthroscopic contact Nd:YAG laser surgery is a safe and effective clinical tool for meniscal resection which may, with increased technological advancements and cost reduction, replace standard instrumentation.

This paper describes the data of experimental investigation of Cr,Er:YSGG radiation (2.79 micrometers wavelength) influence on hard tissues of teeth. The laser operated in pulse free-running regime with the pulse energy 100 - 600 mJ at a repetition rate 1 - 2 Hz. The crater depths, as function of energy density and number of pulses, have been obtained. The damage thresholds and absorption coefficients for dentin (~0.5 KJ/cm³, ~350 1/cm) and for enamel (~3 KJ/cm³, ~180 1/cm) have been estimated. The variation of free-running pulse duration in the range of 100 - 700 microsecond(s) did not influence the efficiency of teeth-radiation interaction.

The great interest in the field of laser applications in dentistry provokes the question, if all these new techniques may really fulfill advantages, which are expected after initial in-vitro studies. Whereas laser surgery of soft oral tissues has been developed to a standard method, laser treatment of dental hard tissues and the bone are attended with many unsolved problems. Different laser types, especially pulsed lasers in a wide spectrum of wavelengths have been proofed for dental use. Today neither the excimer lasers, emitting in the far uv-range from 193 to 351 nm, nor the mid-infrared lasers like Nd:YAG (1,064 μm), Ho:YAG (2,1 μm) and Er:YAG (2,96 μm) or the C0₂-laser (10,6 μm) show mechanism of interaction more carefully and faster than a preparation of teeth with diamond drillers. The laser type with the most precise and considerate treatment effects in the moment is the short pulsed (15 ns) ArF-excimer laser with a wavelength of 193 nm. However this laser type has not yet the effectivity of mechanical instruments and it needs a mirror system to deliver the radiation. Histological results point out, that this laser shows no significant pathological alterations in the adjacent tissues. Another interesting excimer laser, filled with XeCI and emitting at a wavelength of 308 nm has the advantage to be good to deliver through quartz fibers. A little more thermal influence is to be seen according to the longer wavelength. Yet the energy density, necessary to cut dental hard tissues will not be reached with the laser systems available now. Both the pulsed Er:YAG- (2,94 μm, pulse duration 250 s) and the Ho:YAG -laser (2,1 μm, pulse duration 250 μs) have an effective coupling of the laser energy to hydrogeneous tissues, but they do not work sufficient on healthy enamel and dentine. The influence to adjacent healthy tissue is not tolerable, especially in regard of the thermal damage dentine and pulp tissues. Moreover, like the 193 nm ArF-excimer laser radiation the Er:YAG-laser radiation could also only be delivered via mirror systems, while the radiation of the Ho:YAG-Laser can be well transmitted through quartz fibers. The energy of the well known and in other medical disciplines often used Nd:YAG - laser (1,064 μm, pulse duration 150 us) laser can be transmitted through fiber systems without problems, but this laser has not the effectivity to work sufficient on healthy hard dental tissues due to the high transmission in mineralized dental tissues. The thermal injuries of this laser type are not tolerable. The short pulsed TEA-C0₂-laser (9,6 and 10,6 μm, pulse duration 200-300 ns), which has an excellent coupling not only to the hydrogeneous tissues but also to the mineralized tissues could be an alternative system to prepare dental tissues. The greatest disadvantage of this system is the noneffective delivery of the light energy through flexible fiber systems, which are still in development. Another good chance perhaps will have the q-switched Neodym, Erbium and Holmium:- YAG lasers with pulse durations of about some hundred ns. Both, possible thermal influences and possible disruptive effects should be small enough to let the adjacent tissues undamaged.

The aim of the study was to find conditions for selective ablation of carious dentine. Absorption characteristics of healthy enamel, dentine, and carious lesions were studied by means of microspectrophotometry. It was found that in the spectral range of 330 to 520 nm optical density of carious dentine is higher by about a factor of 4 as in respect to healthy dentine. In the second part of the study, ablation thresholds were studied for different tissues at 355 nm (frequency tripled Q-switched Nd:YAG-Laser). By means of a piezoelectric detector, ultrasonic waves generated by ablation and subthreshold thermoelastic mechanisms were detected. Employing a fiber-optic delivery system, selective ablation of carious dentine occurred for pulse energies exceeding 0.4 Jcm^-2 up to 1.2 Jcm^-2.

The basic principles, instrumentation, analytical capabilities and limitations of LAser Microprobe Mass Spectrometry (LAMMS) are briefly presented. Applications of LAMMS in dental science are reviewed. A detailed LAMMS investigation of metallic particles incorporated in the human oral mucosa underlines the potential figures of merit for clinical and toxicological research.

A laser Doppler instrument has been designed for blood flow measurements in the human pulp. By using infrared laser light from a laser diode the penetration into the tooth is considerably improved in comparison with earlier He-Ne measurements. A hand-held, pen-shaped probe facilitates the clinical use of the instrument. Restricted blood flow conditions in trauma patients, as well as the heart-rate synchronous pulsating nature of pulp blood in normal subjects, have been investigated.

In previous reports it could be shown that pulsed Er:YAG laser radiation is effective for the removal of dental enamel, dentin, and caries. Damage to the adjacent hard substances is minimal. Temperature measurements and animal studies revealed that thermal pulp damage can be avoided. The experimental results make the Er:YAG laser promising for the preparation of dental cavities. In many cases patients already have fillings which have to be removed. In the present work, investigation is made of the effect of Er:YAG laser radiation on various restorative filling materials. The experiments demonstrate that removal is possible for all tested cements, composites and amalgam. Ablation efficiency is comparable to that of enamel and dentin, and thus sufficient for practical applications. Morphology of crater walls indicates greater thermal side effects than for natural dental hard substances.

Er:YAG laser irradiation was performed on dental hard substances of beagle dogs. Two, 4, 6 and 8 weeks after laser exposure at various intensities and repetition rates the teeth and especially the pulps were analyzed histologically. No reaction of the pulp was found after enamel or pulpfar dentine exposure to the laser beam even at a radiant exposure of 30 J/cm² per pulse. Fluorescent marking sections of the teeth showed neoformation of calcified dentin after 6 and 8 weeks following laser light impact to the pulpnear dentin or artificial opening of the pulp cavity. These results correspond to the observations of pulp microcirculation during Er:YAG laser irradiation.

Carbon dioxide laser energy has been shown to possess the ability of enhancing dentinal bond strength of a recently introduced dentinal bonding agent. It is presently unclear as to whether Nd-YAG laser energy can have the same effect. The objective of this study was to measure the effect of Nd-YAG laser pretreatment of dentin on the dentinal bond strength. Thirty extracted molars were mounted vertically in an acrylic base, to a depth of their cervical lines. The bottom of the base was flattened, and a plane perpendicular to this base was ground into one buckle surface of each molar. This exposed a dentin surface 6 mm or greater in diameter. These teeth were randomly distributed into two groups, with 15 teeth per group. Brass rings of approximately 5 mm in diameter were placed on these flat surfaces, and filled using Scotchbond 2 (3M) and P-50 (3M) composite material as per manufacturer's instructions. The experimental group was treated identically to the control group with the exception of laser treatment of the dentin at 51 Watts/cm2 for 0.2 sec. before application of Scotchbond 2. After curing, these restorations were shear tested using an Instron machine at 0.1 in/min. crosshead speed. The mean shear strength and standard deviation for the control group were 1.29, 1.74 MPa, and for the irradiated group 1.05, and 1.07 MPa, respectively. Students t-test found no significant difference (P equals 0.2914) between the groups. It does not appear that, at these powers, the Nd-YAG laser possesses the ability to enhance the bond strength of Scotchbond 2 dentinal bonding agent.

Cancer promotion by CO₂ laser surgery is known to occur in animal models. It is not clear whether these observations are relevant to human disease. To test this, a series of 21 patients with oral lesions treated with CO₂ laser surgery were followed for 2 weeks to 32 months with a mean of 10.2 months. Following laser surgery, 83% of lesions presenting as leukoplakia recurred, whereas no recurrences were observed amongst other lesions. This supports the hypothesis that growth factors released in response to CO₂ laser surgery could promote cancers in patients with initiated lesions.

Previous studies by the authors have shown that carbon dioxide (CO₂) laser light has marked effects on dental hard tissues and that these effects are wavelength-dependent. The aim of the present study was to determine whether treatment by CO₂ laser of caries-like lesions in human enamel would inhibit subsequent lesion progression. Nine groups of 10 teeth each with preformed caries-like lesions were treated with/without CO₂ laser (9.32 micrometers , 15 mJ or 25 mJ per pulse) by a pulsed laser (100-200 nsec) for either 200 or 400 pulses. Preformed lesions were then treated with acidulated phosphate fluoride for 5 minutes with control groups with no fluoride treatment. Teeth were subjected to a subsequent pH cycling challenge to determine the protection against lesion progression. Low energy laser treatment coupled with fluoride treatment entirely inhibited subsequent lesion progression in this model system.

With the acquisition of a Nd:YAG and a CO₂ laser in the College of Veterinary Medicine at Oklahoma State University in 1989, over 100 small animal clinical cases have been managed with these modern modalities for surgical excision and tissue vaporization. Most procedures have been for oncologic problems, but inflammatory, infectious, or congenital conditions including vaporization of acral lick 'granulomas,' excision/vaporization of foreign body induced, infected draining tracts, and resection of elongated soft palates have been successfully accomplished. Laser excision or vaporization of both benign and malignant neoplasms have effectively been performed and include feline nasal squamous cell carcinoma, mast cell tumors, and rectal/anal neoplasms. Results to date have been excellent with animals exhibiting little postoperative pain, swelling, and inflammation. Investigations involving application of laser energy for tissue welding of esophageal lacerations and hepatitic interstitial hyperthermia for metastatic colorectal cancer have also shown potential. A review of cases with an emphasis on survival time and postoperative morbidity suggests that carefully planned laser surgical procedures in clinical veterinary practice done with standardized protocols and techniques offer an acceptable means of treating conditions that were previously considered extremely difficult or virtually impossible to perform.

Chloro-aluminum sulfonated phthalocyanine (CASPc) has been proposed as a photosensitizing agent for photodynamic therapy (PDT) of neoplasia. This paper reviews the results of PDT treatment using CASPc as a photosensitizing agent in the treatment of 15 cats representing 23 sites of facial, solar induced squamous cell carcinoma, 4 dogs with hemangiopericytomas, 3 dogs with fibrosarcomas, and 1 dog with multiple cutaneous mast cell tumors. The results of this study to date suggest that CASPc is a good photosensitizing agent for the treatment of some forms of spontaneously occurring malignant neoplasia and should be more thoroughly evaluated for this purpose.

Conventional hyperthermia treatment of superficial tumors in the oral cavity is difficult due to inability in accessing the lesion. A new hyperthermia technique employing near infrared Nd:YAG irradiation delivered through an optical fiber is introduced for heating oral and nasal tumors in animals. This system consisted of an Nd:YAG laser, a He-Ne laser, a computer controlled optical shutter, an interstitial thermometer, computer and a printer. The tumors were heated via surface illumination of the lesion. A thermocouple implanted in the base of the tumor provided temperature feedback for laser energy regulation. Three spontaneously occurring canine (two squamous cell carcinoma on the gum, one pigmented melanoma on the hard palate) and one feline tumor (squamous cell carcinoma on the nose) have been treated with the Nd:YAG laser-induced hyperthermia delivered following radiation therapy. The tumor temperature was maintained between 43.2-43.5 degree(s)C for one hour. Nd:YAG hyperthermia allowed efficient delivery of heat to veterinary oral and nasal lesions otherwise impossible to treat with conventional heating techniques.

The present field study on 800 cases of LPL treatments in situ using a preset `blind code' was designed to verify previously published field results; and to check whether a practicing equine vet, trainer, horse owner or rider may obtain beneficial therapeutic effects in traumatology and/or post-surgery, two of the most prevailing modalities in equine sportsmedicine. With the exception of chronic infected traumas, the positive/beneficial response to LPL treatment was verified in a range of 33.3% (infected) to 100% (non-infected, surgical) of the traumas under investigation. The administration of antibiotics, a modality compatible with LPL treatment in infected injuries, increased the beneficial effects of LPL irradiation to 66.7%. This fact indicates that laser irradiation should not be considered a replacement of common therapeutic routine but simply an efficient follow up or parallel treatment that may act synergistically to the benefit of an injured equine athlete. In the case of non-infected surgical trauma, LPL-treatment was additionally found to shorten the post-surgical `inactive' time period or `comeback time' (CBT), thus bringing the horse back into its sportive capacity considerably faster than without LPL irradiation, and at a statistically significant level (p < 0.001).

A pulsed carbon dioxide laser was used to vaporize articular cartilage in four horses, and perforate the cartilage and subchondral bone in four horses. Both intercarpal joints were examined arthroscopically and either a 1 cm cartilage crater or a series of holes was created in the third carpal bone of one joint. The contralateral carpus served as a control. The horses were evaluated clinically for 8 weeks, euthanatized and the joints examined radiographically, grossly, and histologically. Pulsed carbon dioxide laser vaporized cartilage readily but penetrated bone poorly. Cartilage vaporization resulted in no greater swelling, heat, pain on flexion, lameness, or synovial fluid reaction than the sham procedure. Laser drilling resulted in a shallow, charred hole with a tenacious carbon residue, and in combination with the thermal damage to deeper bone, resulted in increased swelling, mild lameness and a low-grade, but persistent synovitis. Cartilage removal by laser vaporization resulted in rapid regrowth with fibrous and fibrovascular tissue and occasional regions of fibrocartilage at week 8. The subchondral bone, synovial membrane, and draining lymph nodes appeared essentially unaffected by the laser cartilage vaporization procedure. Conversely, carbon dioxide laser drilling of subchondral bone resulted in poor penetration, extensive areas of thermal necrosis of bone, and significant secondary damage to the apposing articular surface of the radial carpal bone. The carbon dioxide laser is a useful intraarticular instrument for removal of cartilage and has potential application in inaccessible regions of diarthrodial joints. It does not penetrate bone sufficiently to have application in subchondral drilling.

Noncontact transendoscopic application of a high-powered Nd:YAG laser was used over six years to treat partial upper respiratory obstruction in 112 large animal cases. Laser irradiation was applied to the standing animal, which has developed into a successful alternative to surgical intervention under general anesthesia for treatment of entrapment of the epiglottis and various nasal pharyngeal masses. Treatment of laryngeal hemiplegia and bleeding disorders of the gutteral pouch were treated by a combined therapy consisting of a surgical approach under anesthesia followed by laser irradiation.

Hollow plastic fibers lined with metal and dielectric films that transmit carbon dioxide laser energy were evaluated for clinical use in upper airway surgery of the horse. These flexible waveguides were used both freehand and through the biopsy channel of an endoscope to incise, coagulate and vaporize tissues in the pharynx and larynx of 4 horses.

Root resection was performed on endodontically treated extracted human teeth exposed to pulsed Er:YAG laser radiation at energy levels between 50 -90 mJ/pulse in wet and dry fields. The lased surfaces were examined by optical and scanning electron microscopy. The smooth, clean resected root surfaces, devoid of charring (in wet fields) indicate that the Er:YAG laser can replace the mechanical drills currently employed in endodontic periapical procedures. In addition, the laser would promote hemostasis and sterilization of the surgical field, resulting in diminished postoperative discomfort.