The effect of normal pulsed Nd-YAG laser irradiation on pits and fissures in human teeth

The effects of normal pulsed Nd-YAG laser irradiation on the acid resistance of human dental enamel of pits and fissures, the cleaning of the pit and fissure contents and fluoride uptake into deep pits and fissures were examined. The acid resistance of the pit and fissure enamel was evaluated by the amount of dissolved calcium per square millimeter of the surface area. The pit and fissure enamel treated with laser irradiation obtained an acid resistance 30% higher than that of the unlased controls. The cleaning effect of laser irradiation on the pit and fissure contents was compared with chemicomechanical and mechanical methods. The laser irradiation was found to clean the pits and fissures to a greater depth without alterating the shape of pits and fissures, compared with the other two methods. The distribution of calcium, phosphorus and fluoride in the enamel of the pits and fissures was then measured by electron probe microanalyzer. At the entrance and in the deep part of the pits and fissures, the fluoride content of the enamel treated with acidulated phosphate fluoride after laser irradiation was higher than that of the enamel treated with acidulated phosphate fluoride alone. These results thus suggest that Nd-YAG laser irradiation might be effective in increasing the acid resistance of the pit and fissure enamel, while removing the pit and fissure debris contents and increasing the fluoride uptake into the pit and fissure enamel.     

Q-switched ruby laser treatment of mucocutaneous melanosis associated with Peutz-Jeghers syndrome

Peutz-Jeghers syndrome is an eponym for circumscribed mucocutaneous melanosis in association with gastrointestinal polyposis. Irregular pigmented macules of varying size and color can be found on the perioral skin, lip vermillion border, buccal mucosa, palate, and tongue. Previous treatments, such as surgical excision, cryosurgery, electrodesiccation, dermabrasion, and carbon dioxide or argon laser ablation commonly result in incomplete removal, scarring, or changes in normal pigmentation. The Q-switched ruby laser used at 694 nm, a wavelength well absorbed by melanin relative to other optically absorbing structures in skin, causes highly selective destruction of pigment-laden cells. In addition, the 20-nanosecond pulse duration produced by this laser approximates the thermal relaxation time for melanosomes, thereby confining the energy to the target. The Q-switched ruby laser produces clinically significant fading of mucocutaneous melanosis in association with Peutz-Jeghers syndrome without complications often seen with other therapeutic modalities.     

Probabilistic laser safety: ocular damage models for Q-switched neodymium and ruby lasers

International standards for the protection of the eyes from the hazards of laser radiation define a nominal ocular hazard distance as a distance beyond which an individual would not be expected to suffer any adverse biological effects. The nominal ocular hazard distance, and any associated hazard zones, are calculated using a deterministic technique. This technique does not consider the likelihood that an eye will be irradiated, or the probability that if any eye is exposed, then some level of ocular damage will result. An alternative method of hazard assessment, without compromising safety, is to adopt a probabilistic approach in which the ultimate safety criterion is that the expectation of someone receiving ocular damage must be less than some acceptable risk level. An important element in this assessment is an ocular damage model, which predicts the probability with which a laser exposure will cause permanent eye damage. This paper describes a rationale for the use of the minimum ophthalmoscopically visible lesion as a threshold criterion for the development of ocular damage models. A brief review of existing ocular damage threshold data for Q-switched neodymium:YAG and ruby lasers is presented, and ocular damage models for these lasers systems are derived.     

A clinical study of hair removal using the long-pulsed ruby laser

BACKGROUND: Laser hair removal is rapidly becoming a widely used modality. Clinical studies are needed to assess these hair removal systems. The long-pulsed ruby laser is one such modality for the removal of unwanted hair. OBJECTIVES: To evaluate the efficacy of the long-pulsed ruby laser (694 nm, 3-msec pulsewidth, 7- or 10-mm spot size) in removing unwanted hair, and to provide treatment guidelines for the proper utilization of this laser system. METHODS: Forty-eight areas of unwanted facial and body hair from 25 patients with blonde, brown, or black hair were treated with the long-pulsed ruby laser at fluences between 10 and 40 J/cm2. Hair regrowth was measured at 4 weeks after the first treatment, 4 weeks after the second treatment, 4 weeks after the third treatment, and 16 weeks after the third treatment by counting the number of terminal hairs compared with baseline pretreatment values. All complications and treatment outcomes were documented. RESULTS: The mean percent of regrowth after the first treatment was 65.5%, 41% after the second treatment, and 34% after the third treatment. Overall, regardless of skin type or targeted body region, patients who underwent three treatment sessions demonstrated an average 35% regrowth in terminal hair count compared with baseline pretreatment values 6 months after initial therapy. CONCLUSION: Long-pulsed ruby laser treatment resulted in significant hair growth delay in most cases. Repeated laser treatments produced an increased number of vellus hairs, an increase in growth delay, and a decreased percentage of hair regrowth.     

Comparative gross and histological effects of the CO2 laser, Nd-YAG laser, scalpel, Shaw scalpel and cutting cautery on skin in rats

Pseudotumoral mediastinal and pulmonary amyloidosis occur infrequently and may be confused with other tumors that are found more commonly in this region. Enlargement of hilar lymph nodes in the absence of pulmonary involvement is extremely rare. We report a case of nodular amyloidosis of the hilar lymph nodes that was studied using different diagnostic and radiologic methods. A previously healthy 79-year-old man presented with a large right hilar mass detected on routine chest roentgenography. The extensive mass behaved like a solid tumor and mimicked a bronchogenic carcinoma. At thoracotomy, frozen sections revealed the tumor to consist of kappa-light-chain amyloid. In light of the irresectibility of the tumor, thoracotomy was ended as open biopsy. Immunoelectrophoretic analyses of the plasma and urine showed no evidence of a paraprotein immunoglobulin or light chains. The patient was discharged without symptoms of disease. Different diagnostic procedures before and after surgery are discussed.     

A practical review of laser-assisted hair removal using the Q-switched Nd:YAG, long-pulsed ruby, and long-pulsed alexandrite lasers

BACKGROUND: The recent development of numerous laser-assisted hair removal techniques has produced confusion in the field of cutaneous laser surgery. OBJECTIVES: A systematic review of the hair removal laser systems currently available is attempted. Appropriate patient selection, treatment protocols, and discussion of each system's advantages, disadvantages, and complications is provided. CONCLUSIONS: Techniques involving the use of selective Q-switched Nd:YAG and long-pulsed alexandrite and ruby laser systems provide a significant delay in hair growth. With further technologic advances and understanding of proper treatment parameters and intervals, it is expected that permanent hair removal may eventually be possible.     

Opacification of the posterior capsule after IOL implantation and its therapy using a picosecond Nd-YAG laser

In a group of 1700 patients after operation of cataract with implantation of IOL the authors found opacification of the posterior capsule in 765 instances (45%). Treatment was provided with a Nd-YAG laser using a picosecond regime. The authors discuss the causes of opacification, successful surgery and its complications.     

Efficacy of the ruby laser in the treatment of Ota's nevus previously treated using other therapeutic modalities

Ruby laser treatment, especially with a Q-switched laser, is remarkably effective for Ota's nevus, although a wide variety of other therapeutic modalities have had limited success. Consequently, laser treatment is now considered the treatment of choice. However, for Ota's nevus previously treated with dry ice cryotherapy (carbon dioxide snow), dermabrasion, free skin grafting, or other methods, therapy is still a challenge, even with the ruby laser. In this study, 14 patients with Ota's nevus previously treated using other modalities were treated using a Q-switched ruby laser. Eight patients previously underwent dry ice cryotherapy, three patients underwent free skin grafting, two patients underwent dermabrasion, and one patient received a cosmetic tattoo. The study group was composed of five male and nine female patients. The ages of the patients at the start of treatment ranged from 5 to 62 years. We concluded, based on the findings of this study, that Q-switched ruby laser therapy can provide favorable results even with lesions previously treated by other therapeutic modalities, provided that the treatment sessions are repeated more frequently and over a longer period of time than those used for untreated lesions and that they are combined with plastic surgical techniques such as scar resection or local flaps.     

Classification of laser irradiation and safety measures

The use of lasers in medicine and especially surgery is rapidly expanding in many disciplines from clinical laboratory to the office practice and operating room. It is essential that users of this powerful tool have knowledge of their potential hazards and the measures to protect patients and personnel against injuries or undesired effects. Below, we have included information about the way lasers are classified; the development of protective standards; the current status of protection standards that apply to lasers, especially those used in medicine/surgery; the specific kinds of hazards associated with medical/surgical applications; and the measures by which hazards have been controlled. Since laser technology is still a young field, it is likely that problems unknown at present will occur and methodologies for controlling hazards will evolve. The American National Standards Committee produced the first consensus standard Z136.1 in 1973. The Standard was revised in 1976 to accommodate differences in biological effects for different wavelengths in the visible spectrum. The ANSI Standard has been revised again in 1980, and currently (1984) there are two additional standards in preparation, Z136.2 and 136.3, which treat the safe use of light-emitting diodes and the safe use of lasers in the health care environment, respectively. Most surgical and medical lasers are Class III or IV. Some lasers have a Class IV therapy level beam plus a Class I or II alignment beam. When using lasers, it is possible to generate incandescence or fluorescence in an irradiated object. This can occur even with protective eyewear, because the correlated radiations are usually of a different wavelength. Generally, this should not be a problem when beams are directed at biological material. However, hazard could be caused by lasers designed to produce fluorescence. Control of correlative radiation in a laser system is required in the federal regulations. Hazards of lasers may be grouped as those to the eye, skin and associated hazards, fire, x-rays, electrical, fumes, toxic materials, etc. Effects on tissue are governed by the following factors:--the energy or power density of the beam;--the absorption in tissue at the laser wavelength;--the time the beam is held at a given area.;--the protective effects of heat removal by thermal conduction and by circulation. Eye hazards include thermal burns or acoustical disruption (shock waves) from high-powered or high-energy beams in the visible and near infrared wavelengths. Direct beam exposure or specular or diffuse reflaction from these very high-power lasers can also cause injuries to other parts of the retina. For example, beams can directly penetrate through the sclera and cause retinal injury. Near ultraviolet (less than 400 hm) and far infrared (.3000 hm including CO2 lasers) can cause moderate to severe corneal burns. Far ultraviolet (200-315 nm), mid infrared (1400-3000 nanometers) can cause welders' flash or snow blindness and chronic exposure could cause cataract, and exposure to ultraviolet rays may be carcinogenic. For CO2 lasers, the far infrared radiation is attenuated by plastic goggles, or by glasses, or quartz. Other eyewear with special filters is used for different lasers. The whole personnel who may be exposed to direct beams, specular reflections, and many times diffuse reflections must wear protective eyewear. In all cases the surgeon and others viewing the procedure through the endoscope need glasses or suitable protective lenses installed in the endoscope. Persons who are not viewing the beam may not need to wear protective glasses with the same level of optical density. Glasses may be selected to provide protection for lasers operating in the visible wavelength to the point where the normal aversion response could protect the individual.     

Microcirculatory bed of the rat ovary in health and under laser irradiation

Personal clinical observations during the recent years allow the authors to confirm the indisputable value of surgical experience got during the Great Patriotic War (1941-1945) and in particular, the "fourfold" scheme proposed by V. I. Voiachek for the diagnosis and treatment of blind gunshot wounds to the skull base. Computed tomography considerably increases the probability of detection of the exact localization of foreign bodies in complex anatomical structures of the skull and thus facilitates choosing the most rational surgical management. The use of the electro-optical transducer for the extraction of foreign bodies from almost inaccessible areas of the skull base decreases the risk of operation.     

Effect of low-power laser irradiation on impulse conduction in anesthetized rabbits

Low-power laser analgesic effect was generally accepted in clinical cases, whereas there was no direct evidence to indicate that low-power laser irradiation suppressed an impulse conduction within a peripheral nerve. The effect of low-power laser irradiation on electrically evoked responses within the sural nerve was electrophysiologically analyzed in anesthetized rabbits. High threshold evoked responses (conduction velocity was about 11 m/sec, unmyelinated A delta), which were induced by an electrical stimulation to the peripheral stump of the nerve, were significantly suppressed (9 to 19% inhibition) during low-power laser irradiation, which applied to the exposed sural nerve between the stimulus site and the recording site. The suppressive effect was reversible and recovered to the control level after the irradiation. Experimental evidence indicated that low-power laser irradiation suppressed the impulse conduction of unmyelinated A delta afferents in peripheral sensory nerve, which caused a pain sensation. Our data suggest that low-power laser acts as a reversible direct suppressor of neuronal activity.     

Stereological studies of the effects of alpha-MSH and cAMP on melanosomes in melanoma cells

It is generally accepted that the severity of renal insufficiency in patients correlates with the severity of tubulointerstitial abnormalities, but not with the severity of glomerular abnormalities in kidney biopsies. We recently challenged this view by demonstrating significant correlations of glomerular structural abnormalities with renal function in a histomorphometric study of biopsies from patients with various kidney diseases. We set out to confirm these findings in biopsies from patients with a single disease entity. IgA nephropathy was selected. An additional objective of the study was to determine the prognostic value of our histological predictors of renal function. Histomorphometric measurements were done in silver- and PAS-stained paraffin sections of biopsies from 83 patients with primary IgA nephropathy. The results were correlated with creatinine clearance at the time of biopsy. The prognostic value of the histomorphometric parameters and of several clinical characteristics were determined in a Cox proportional hazard model. All glomerular histomorphometric indices correlated with the severity of renal insufficiency, but quantitative estimates of the glomerular deposition of periodic acid-Schiff positive extracellular matrix (PAS-index) seemed to be the most important glomerular structural-functional correlate (r = 0.53, p<0.001). However, the correlation of quantitative estimates of the severity of interstitial extracellular matrix accumulation with renal function (quantitative interstitial index) was superior (r = 0.76, p<0.001). Creatinine clearance at biopsy and initial proteinuria were the strongest clinical predictors of renal survival. The severity of tubulointerstitial extracellular matrix accumulation was the strongest histological predictor of an adverse outcome. In conclusion, quantitative estimates of the severity of glomerular and tubulointerstitial extracellular matrix accumulation both correlate well with the severity of renal failure in biopsies from patients with IgA nephropathy. Creatinine clearance at biopsy, initial proteinuria and the severity of tubulointerstitial extracellular matrix accumulation are the best predictors of renal survival. On a more general note, the paradigm of the absence of correlation of glomerular pathology with renal function should be abandoned.     

The effect of chlorine substitution on the dermal absorption of polychlorinated biphenyls

This study investigated the characteristics of computer-based case simulations (CCS) that may be associated with case difficulty. Difficulty was defined as the average rating by physicians of examinee performance on a nine-point scale or the passing rate on the cases. Two data sets were used, one from an administration of 18 cases, the other from an administration of 22 cases with 13 cases used on both occasions. Stepwise regression procedures were used separately for case properties and for analytic scoring of key variables to identify the best sets of predictors of case difficulty. Because of the small number of cases, regression results were evaluated for consistency across both data and both difficulty measures. For key variables, the best set of predictors included the number of different serious errors of commission, risk items, and benefit items. In general, cases were more difficult for higher values of these variables. For case variables, the only consistent variable was the length of the paragraph that provided patient history, with longer paragraphs associated with more difficult cases. Other variables were less consistent, but were often related to the structure of the simulation or the severity of the patient condition. Although the findings for case variables were limited, the analyses were very helpful in illuminating the interconnections among the variables within cases.     

Use of laser irradiation in the surgical treatment of pulmonary echinococcosis

Unilateral disturbance of nasal respiration was modeled in albino rats. All animals developed deformations of the skull in the sagittal and transversal planes. The pathogenesis of deformations is connected with neurotrophic disorders and injury to the nasal cartilaginous structures responsible for the skull growth.