The immersion technique of detection of refractive index of bulk dentin is described. This technique is based on waveguide optical properties of dentin. The values of refractive index of dentin of recently erupted teeth are measured to be 1.553 +/- 0.001.

The frequency conversion of light in dental tissues is examined experimentally. It is shown that IR picosecond pulses of passively mode- locked neodymium laser stimulate the emission of visible radiation in enamel and dentin under threshold of destruction. The spectra of emitted radiation are measured in different regimes of dental tissue excitation. It is observed that the wavelength of maximum intensity and bandwidth of spectral distribution of visible radiation correspond to second harmonic of YAG:Nd laser radiation. The comparative study of second harmonic generation is enamel and dentin is carried out. The spatial spectra of forward scattered second harmonic radiation are measured. The nonlinear transmission of intact dentin in the field of intensive ultrashort Nd- laser pulses is observed. The possibilities of optical diagnostics of hard tooth tissues are discussed.

The aim of the study was to describe the effects of a caries selective laser system applied on human dentin. Ablation efficiencies of laser pulses emitted from a frequency doubled, gain-switched Alexandrite-laser (wavelength 377 nm) were determined for carious as well as for healthy dentin. Laser pulsed of different pulse duration, 100 ns and 1.6 microsecond(s) , were investigated in comparison. In spite of the different peak power- due to the different pulse durations-the ablation thresholds and ablation efficiencies were found to be about the same for 100 ns as for 1.6 microsecond(s) laser pulses. In healthy dentin two ablation efficiencies (0.03 and 0.12 mm³J^-1), according to the two different ablation regimes, could be described. An overall ablation efficiency of carious lesions from 34 different teeth was determined to be about 0.3 mm³J^-1. Fluences used for morphological and histological assessment were chosen with respect to the previously described ablation thresholds of healthy dentin. With respect to operating speed, the '99% selectivity mode' for fast caries ablation with fluences within the first ablation regime of healthy dentin (2.6 +/- 0.3 Jcm^-2) were used. The effects of different surrounding media-water and air-were studied in comparison. Light- and scanning electron microscopic investigations were performed. If during irradiation the tooth was submerged in water, craters in healthy dentin were small and uncolored. Crater walls demonstrated only a few microns of surface roughness. Ablation debris remains associated to the crater wall. Irradiation in air results in an early carbonization accompanied with melting and cracking of the irradiated dentin. As long as water cooling is provided the histological findings reveal that engaging a frequency-doubled Alexandrite-laser caries selective ablation is possible without too much damage to the surrounding healthy tissues. Nevertheless an active flow of cooling water is desirable in order to remove hot ablation debris out of the crater.

The results of comparative study of laser destruction of tooth dentin caused by intensive picosecond YAG:Nd laser pulses and submillisecond YAG:Er laser radiation are represented. The dependencies of destruction threshold and efficiency of laser treatment on demineralization degree of dentin are represented. The quality of laser cavities formed in demineralized dentine slices cut across the dentin tubules is analyzed. The possible mechanisms of destruction are discussed.

Ablation thresholds of healthy dentin were measured engaging four different pulsed laser systems, emitting in the near ultraviolet (wavelength 355 nm, wavelength 377 nm), in the near infrared (wavelength 755 nm), and in the mid infrared (wavelength 2.9 micrometers ) spectral region. A pulse duration of 200 ns was used during experiments with the Alexandrite-laser (wavelengths 377 nm and 755 nm) whereas at the wavelength 355 nm pulse duration was fixed at 9 ns and at wavelength 2.9 micrometers pulse duration was set to 200 ns again. Two well defined ablation thresholds could be detected using laser wavelengths which are well absorbed by the target (near UV, mid infrared). Due to low absorption of near infrared wavelengths in healthy dentin, high fluences must be engaged for ablation of healthy dentin. In this spectral region only a more or less statistically appearing ablation threshold was observed. Caused by high fluences unpredictable plasma formation takes place. Even so, short pulse duration leads to high peak power, thus originating plasma.

The purpose of this study was to determine the ablation rates of healthy and carious enamel and dentin on extracted human permanent molars and premolars. Measurements were taken using a flash lamp pumped pulsed 2.94 micrometers CrEr:YAG laser (pulse length 200 microsecond(s) , energy density 2-20 J/cm², f equals 1-2 Hz). Teeth were cut into slices of 2 mm thickness and the ablation rates of 1450 craters were measured as a function of the energy density and pulse number. Clearly higher degrees of ablation were observed in dentin than in enamel with most effective ablation rates in carious enamel and dentin. Ablation thresholds in enamel, dentin and caries could not be detected. However, it could not be shown that there is any selectivity in caries removal by Erbium:YAG laser radiation.

A numerical combined model with movable boundary conditions have been used for the evaluation of Er-laser dental treatments is presented. This model facilitates the simulation of heat flows and temperature distribution in different kinds of human teeth caused by Er-laser irradiation with arbitrary orientation of laser beam axis. This model can be used for simulation and optimization of exposure parameters to minimize pulp overheating and procedure duration in the application of lasers for dental treatment.

The results of the investigation of bacteria (streptococcus, staphylococcus, bacillus subtillis) vitality in products of a destruction of human hard dental tissues simulated by submillisecond YAG:Er and YSGG:Cr;Er laser pulses are first represented at this lecture. The dependencies of bacteria vitality from energy density and Er-laser radiation exposure are given also. The problems of availability of some possible mechanisms of bacteria destruction by Er-laser submillisecond pulses are talked over.

This paper represents the first results of the investigation of an interaction between YAG:Cr;Tm;Er ((lambda) equals 2.69 micrometers ) laser radiation and human hard dental tissues. A comparison of intact and carious enamel and dentine destruction thresholds by submillisecond pulses of YAG:Cr;Tm;Er laser is first given also.

The paper presents the investigation results of the morphofunctional state of the mouth cavity tissues after teeth processing by the laser radiation with the wavelength 2.69 micrometers . Teeth preparation down to the state of the deep or intermediate caries as well as pulp trepanation cases are discussed. No pulp necrosis was observed.

The paper presents the main results of the clinical study of the laser radiation with the wavelength 2.69 micrometers usage for the teeth caries preparation. This laser prospects for the dentistry are shown.

In this work we represent the results of emission spectral analysis at laser atomization of hard tooth tissues. The spatial-temporal characteristics of laser emission plume for enamel and dentin have been studied. The dynamics of spectrum temporal evolution for enamel and dentin and the spectra in several parts of plume have been evaluated. The analysis of spectrum at transition from high energy sub-msec pulses with comparatively small power density to short sub-nsec pulses with low energy but high power density was carried out. The spectral of emission plume have been investigated under the excitation of laser radiation with several wavelength. The influence of water irrigation on spectrum character was also investigated. It was shown that the spectra character are different for the enamel and dentin at sub-msec duration pulses.

For the treatment of carious decays of enamel and dentin the Er:YAG laser is preferred in comparison to other laser systems, because of the thermomechanical process. Cavity preparation as well as removal of secondary carious lesions without thermal damage to the tooth hard substances and the pulp is possible. Clinical studies have shown that the pain perception is less than by drilling with the mechanical burr. From experimental studies it can be concluded, that the Er:YAG laser can possibly substitute the acid etching technique in conditioning the tooth surface. Further indications can be given in oral surgery for incision or excision of benign mucosal diseases and for cutting bone. As an advantage, opposite to other thermal laser systems, the wound healing process is very similar to the wound healing after mechanical cutting by the scalpel or by the burr.

Any laser that will be used by dentist to replace the dental drill (handpiece) must remove dental hard tissues safely. These lasers must also have the ability to ablate the restorative dental materials which are present in the teeth being treated. Prior to any laser being used to treat humans a thorough knowledge of the effects of the laser treatment on dental materials must be understood. Cores of dental amalgam were created and sliced into thin wafers for this experiment. Ablation efficiency and thermal changes were evaluated with and without water. It appears as if the Er:YAG laser can effectively ablate amalgam dental material with and without water. The water prevents the temperature from increasing much above baseline and does not reduce efficiency of ablation.

There have been 4032 laser surgical operations for the last 7 years with first generation lasers available CO₂, Nd:YAG, Argon, Combo (CO₂ + $Nd:YAG). The most important experience, the advantages and disadvantages of application are shown by the evaluation of the results and complications. In oral soft tissue surgery there have been established the most important indicational circles of the use of first generation lasers. The clinical introduction of a second generation of surgical lasers Ho:YAG, ER:YAG, Excimer etc. brings new possibilities in not only hard tissue surgery, but it also widens the advantages of the use of surgical lasers in the surgery of oral soft tissues.

The results of investigation of interaction of combined of Ho- and Nd- laser radiation with soft tissue in contact and noncontact modes of processing under fiber-optical delivery system application are represented. Laser wound is evaluated according to criteria of efficiency (energy of laser radiation spent to removal of unit volume of tissue) and invasion (ratio of irreversibly necrotized tissue volume to removed tissue volume). The dependencies of destruction efficiency index and laser wound invasion on energetically parameters of laser radiation and destruction rate are represented. The considerable difference of destruction efficiencies of contact and noncontact modes is shown. The requirements to optimum parameters of combined Ho- and Nd- laser radiation for surgery are formulated.

This presentation will demonstrate and discuss any surgical applications of the Argon dental laser. This presentation will also increase the awareness and basic understanding of the physical principals of the Argon laser. The wavelength of the Argon laser is specifically absorbed by red pigments such a hemoglobin which is abundant in oral soft tissue. The result is a sharp clean incision with minimal thermal damage to adjacent healthy tissue. Preprosthetic procedures such as full arch vestibuloplasty, labial and lingual frenectomy, and epulis fissuratum removal will be demonstrated. Other soft tissue management procedures such as minor periodontal pocket elimination surgery (gingivectomy), removal of hyperplastic granulation tissue from around poorly maintained implants, and the removal of granulation and/or cystic tissue from the apex of teeth undergoing endodontic (apicoec-tomy) surgery will also be demonstrated and discussed. Provided basic oral surgery protocol is followed, surgical procedures utilizing the Argon laser can be accomplished with minimal bleeding, minimal trauma and with minimal post-operative discomfort.

The argon laser has proven to be a valuable tool for the thermodynamic debridement of the periodontal lesion, incisions and tissue fusion. Illustrations of clinical applications and discussion of laser parameters will be provided.

The Nd:YAG laser has ablation, crack, and crater effects on the dental enamel through black mediators which are very similar to the acid etching effects of phosphoric acid. This study was designed for searching how the different black mediators influence the shear strengths of the brackets bound to the enamel surfaces which were treated with the Nd:YAG laser. 90 bovine enamels divided into 5 groups were painted with 5 kinds of black mediators including Chinese ink, oil ink, black ball pen, water ink and black transfer paper. The enamel surfaces painted with black mediators were then radiated by Nd:YAG laser (ADL; American Dental Laser 300dl, power: 20 pps, 87.5 mj). Orthodontic brackets were bonded to the radiated surfaces. Then the shear strengths of the brackets to the enamels were measured by Instron. The results showed that the Chinese ink group and oil ink group has the strongest shear strength, ball pen group and water ink group showed the second strength, and the transfer paper group has the lowest shear strength. In addition, scanning electronic microscope also was used to observe the topographic changes of the enamel surfaces induced by the laser ablation.

The following paper introduces the results of an interdisciplinary research project. With the aid of photomacroscopic examination, light and scanning electron microscope investigations, changes to temporomandibular joint structures were detected in vitro after irradiation with an Erbium:YAG laser system. The solid-state Erbium:YAG laser, operating at a wavelength of 2.94 micrometers was used in the normal- spiking mode. The free-running laser beam was focussed onto freshly excised porcine tissue samples using a 108-mm sapphire lens. In this study the output was generally pulsed at a repetition rate of 4 Hz, with a pulse duration varying from 120 microsecond(s) to 500 microsecond(s) . Between 50 mJ and 500 mJ per pulse were applied to create pinpoint lesions. The optimum average energy density and pulse duration of the Erbium:YAG laser radiation for the purpose of TMJ-surgery (as far as it concerns meniscus and articulating facets) - which means efficient etch rate and minimal adjacent injury - seems to be about 24-42 J/cm² and 120 microsecond(s) -240 microsecond(s) , respectively.

The present study investigated the effect of CO₂ laser irradiation on dentin underneath the carious dentin that is to be removed.The investigation consisted of two experiments. In the first experiment, morphological and elemental changes of extracted human dentin irradiated by the CO₂ laser were observed by microscope, SEM and XMA. In the second experiment, changes in hardness of bovine dentin irradiated by the CO₂ laser were examined. Panalas C10, a CO₂ laser with a flexible optical fiber, was used with different total energies for both experiments. The present study showed that CO₂ laser irradiation made a significantly harder arched layer underneath the superficial carbonized layer in dentin. It seemed that this harder layer occurred where the dentin tubules were plugged with particular structural elements, and where there was a high concentration of calcium and phosphorus. It is suggested that use of the CO₂ laser irradiation to remove carious dentin may have an additional effect that enhances the mechanical and chemical properties of the dentin layer underneath the carious dentin.

The effect of the Er:YAG laser on caries removal was studied. Extracted human teeth with cervical root caries were used. Each root caries lesion was divided into two areas axially. A divided half was treated with the Er:YAG laser, and the other was removed with round steel burs mounted on an electric engine or was nontreated as a control. Laser irradiation was performed at 160 mJ/pulse (56.5 J/cm²/pulse) and 10 pps under water spray using a fiber delivery system with a contact probe. The time required for caries removal was measured with each treatment. SEM observation and hardness measurement of cavity floor dentin, and observation of the decalcified serial sections of the specimens were compared. The results indicated that the removal of carious dentin using Er:YAG laser could be performed to the same degree as the electric engine treatment. In addition, the Er:YAG laser treatment diminished unpleasant sound and vibration. However, it was noticed that careful laser irradiation was necessary for the removal of infected dentin layer without overreduction of intact dentin layer. The time required for the laser treatment was longer than that for the electric engine treatment under the conditions of the present experiment.

A histopathological study was performed on the tooth pulp of mongrel dogs after cavity preparation using the conventional high speed method (control group) and the newly developed Er:YAG laser system (laser group, output energy: 100 mJ, 150 mJ, and 200 mJ/pulse). All samples were divided into two groups (deep cavity and shallow cavity) according to the remaining dentin thickness (RDT) and histopathologically evaluated. After 1, 2, 4, 7 and 28 days postoperatively, there was no histopathological difference between the control group and the laser group. Er:YAG laser irradiation with three different output energies made little difference in the degree of pulpal damage. In the deep cavities, damage of the pulp was more remarkable than the shallow cavities in all groups. The efficacy of cutting rate in the laser group was not very different from the control group.

The results of investigation of dynamics of free-running YAG:Er and YSGG:Er:Cr lasers are represented. The influence of pumping, cavity parameters and parameters of crystals on duration and temporal profile of laser pulse is determined.

Low energy laser radiation is widely used in different areas of medicine including dentistry. The main biologic laser radiation action mechanism is its multiangle influence on disease pathogenesis. In clinical practice, the most widely spread equipment is based on helium-neon laser (HNL) with the wavelength of 630 nm. HNL is able to cause different therapeutic effects depending on power flow density, i.e. antiinflammatory, microcirculation stimulation, metabolic, proliferative tissue activity, analgetic. However, considering specific features of oral cavity and parodontium disease pathogenesis, it is necessary to point to a few weak features of HNL. For example, HNL in therapeutic doses has insufficient antimicrobial and antiinflammatory effects; it just decreases microflora pathogeneity in the oral cavity. HNL radiation has poor lithic effect (for example, during the period of debridement) [Prokhonchukov, Zhizhina, Lapidus, 1985]. Regardless of the apparent positive HNL effect following extracorporal or intravascular blood irradiation in cases of generalized acute infection, this method is not used often in dentistry. Therefore, there is a necessity to search for some other more adequate laser irradiation sources which would solve prophylaxis and treatment problems for the most widely spread dental diseases such as caries, parodontosis. As far as a prior aim of laser radiation is to elicit different therapeutic effects, depending on laser beam intensity, the main principle of the treatment should be to vary this as well as wavelength values at different stages of development, duration and pathologic process profylaxis. In order to optimize efficiency of light biostimulators in dentistry it seems of importance to consider theoretical prerequisites of photobiological activation processes and specific activity of different light wavelength effects.

The main factors in pathogenesis of the mouth mucosa and parodontium are defects in microcirculation: changes in the vessel tone, the vascular wall permeability and reactivity, rhealogical properties of blood and defects in metabolism and local factors of immunological defence. He-Ne laser (HNL) radiation with wavelength of 630 nm has been effectively used as an antiinflammatory procedure. HNL was determined to lower permeability of vessels, to increase the rate of volumetric blood flow, to rise Po2 in periodontal tissues which helps to stop tissue hypoxia and to do away with oedema.

Laser stomatology- a relatively young branch of stomatology -has been developing actively lately. Bactericidal action of laser radiation enables to use it widely for processing carious cavities and root canals in the treatment of caries and its complications. 113 patients were studied by us. The 40 patients had antiseptic procedure of the caries cavity and then the procedure of laser therapy, so micro-organisms were found out in 26% cases. The 63 patients had antiseptic procedure only, so micro-organisms were found out in 70% cases. Control group were consisted of patients, where laser therapy was carried out without antiseptic remedies.

Application of the low-intensity laser irradiation let decrease to a marked degree complication in the treatment of pulpitis, periodontitis and pulpoperiodontitis, and reduce the period of tooth and periodontal tissues phlogistic. Morphological researches evident confirm clinical results on the example of the 380 patients. Combination of the laser therapy with various varieties of the medicinal treatment is possible and effective. The results of our researches prove the value of laser therapy application in endodonty. Integral and pathogenetic effect of laser in influence on the pulp and periodontal tissues let us recommend the present variety of therapy as the main in treatment of endodontic pathologies. The great success has been achieved in using the lasers in the treatment of dental diseases during the last years. There are some reports in the literature devoted to the positive effects of the laser therapy in the prophylaxis and treatment of caries /7, 11, 13/, pulpitis /3,6,8, 11 /, elimination of the complications in the treatment of pulpitis and periodontitis /2,3, 4,5,10/. The notes in some papers /1,6,7,10,11,12/ about the affects of therapeutic treatment, associated with the multifactor pathogenic activity of the laser irradiation on the dental tissues are extremely important too. At present various methods are used in the treatment of pulpitis and periodontitis, and they give the possibility to make a prognosis about different modifications in applying lasers into a complex of therapeutic procedures. In connection with this the search for the optimal parameters and methods in laser therapy is quite actual.

Effective methods of reveling overload zones of the oral mucosa under the bases of plane dentures, the effect of low intensity laser radiation ont he increase of its resistance are discussed. At present removable plate dentures of different modifications to a certain degree restore aesthetic proportions of the face, phonetics and malfunction of the teeth and jaws. Besides, removable bridge are known not to secure even distribution of mastication pressure along the whole dentures bed which results in the development of inflammatory and dystrophic processes, and, finally in the accelerated atrophy of the oral mucosa and bony tissue of the alveolar process of upper and alveolar parts of the mandible. Many papers are devoted to the anti-inflammatory effect of laser therapy. Improvement of metabolic processes and revascularization of the dentures bed mucosa, normalization of the oral microflora structure, anesthetizing effect is noted too. At the same time there are no papers about studying the therapeutic effect of low intensity laser radiation intraumatic dentures stomatitis, inflammation of the oral mucosa in the literature available for us. To increase the functional effectiveness of removable plate dentures, profilaxy of inflammation and dystrophic phenomena and to decrease adaptation period we have developed methods of early detection of overload zone of oral mucosa at the initial stages of acute inflammation with the help of macrohistochemical reaction. Visible with the naked eye for the timely and precise correction of the dentures.

The light of He-Ne laser is widely used for the treatment of many stomatological diseases. The caries static activity of a helium-neon laser (HNL) light, its influence ont he activation of microcirculation of the pulpenzyme system and on the increase of enamel permeability became clear nowadays. These data allow to suppose that the Ne-Ne light may potent the activity of the initial caries by the increase of teeth stability to the factors provoking the caries.

The problem of complex treatment of inflammatory disease of parodontium has become very acute and actual at the moment. The diseases of inflammatory nature are considered to be the most vital issues of the day. The state of the local immune system of oral cavity plays the most important role in the complicated mechanism of inflammatory process development in the tissues of parodontium. Recently physical factors have become predominant in the system of complex therapy of parodontitis. The application of low-intense laser radiation (LLR) is considered to be the most important and up-to-date method in the preventive dentistry. There were 60 patients of average damage rate suffering from chronic generalizing parodontitis at the age of 25 up to 55 under observation. The major goal of examination was to get the objective results of the following methods' application: parodontium index (Russel, 1956), hygiene index (Fyodorov, Volodkina, 1971), Bacterioscopy of dental-gingival pockets content, simple and broadened stomatoscopy (Kunin, 1970), SIgA level determination in mixed saliva (Manchini et all, 1965) and R-protein level in gingival blood (Kulberg, 1990). All the patients were split into 2 groups. The first group (30 patients) has undergone the laser therapy course while the second group of 30 patients couldn't get it (LLR). Despite the kind of therapy they have undergone, all the patients have got the local anti-inflammatory medicamental therapy. The results of clinical observations have proved the fact that laser therapy application makes it possible to shorten the course of treatment in 1.5 times. The shifts of oral cavity local resistance take place in case of chronic generalizing parodontitis. The direct immunostimulating effect could be observed as a result of LLR- therapy application. The close connection of both anti-inflammatory medicamental and LLR-therapy has proved the possibility of purposeful local immune status correction in case of parodontitis.

In this article we discuss the methods of definition of indication for laser therapy on the base of findings of a priori systematization of diagnostic caries signs with the purpose of reducing their volume and exposing the most informative of them used in the procedure of specified classification of biomedical objects conditions, forming graphic base of the recommendations in choice of treatment methods.

Acute radiation reactions and injuries of lips skin and mucous membrane occur after radiation treatment of lips cancer. We denote such reactions and injuries of lips skin and mucous membrane by common term- afterradiation heilit. Medicinal treatment is not effective enough in the solution of this problem. So we created the method, which can allow to cure afterradiation heilit only by low-intensity laser irradiation fully and without complications.

In this work was carried out microbiological estimate the efficiency of ultraviolet and He-Ne laser radiation at the treatment of parodontitis. 90 persons was investigated with parodontitis of middle serious diagnosis. The optimal regimes of ultraviolet radiation influence on various micro-organisms discharged from pathologic tooth pocket (PTP) were determined. On the base of specils microflora composition study and data of microbic PTP dissemination owe may conclude that the complex He- Ne and ultraviolet laser radiation show the most pronounced antimicrobic effect.

The aim of the present paper is the presentation of biophotometrical data obtained from various anatomic-topographical mouth areas to be used for the development of differential approaches to laser therapy in dentistry. Biophotometrical measurements were carried out using a portative biophotometer, as a portion of a multifunctional equipping system of laser therapy, acupuncture and biophotometry referred to as 'Aura-laser'. The results of biophotometrical measurements allow the implementation of differential approaches to laser therapy of parodontitis and mucous mouth tissue taking their clinic form and rate of disease into account.

To study microvascular changes in parodontium under the Low Level Laser Therapy the investigation of volunteers and patients with parodontitis has been conducted. With the contact luminescent microscope we have observed the microcirculatory bed under various stages of parodontitis. We have also used the Laser Doppler Flowmeter in assessment of capillary blood flow. Our work has shown that the microcirculation state is dependent on the stage of disease. Tissue blood flow rapidly falls under hard parodontitis stages. The laser therapy in combination with traditional treatment is very effective in the case of the light and middle stages of parodontitis. There are the restoration and even the enhancement of capillary blood flow and the reconstruction of native microvascular bed in parodontium after complex therapy. The long-term results of laser therapy are also positive.

The theoretical model of coherent light scattering on enamel and dentin surface is described. The surfaces of hard tooth tissues are represented as 3D rough structures. The enamel components are assumed to form mosaic structure consisting of enamel prisms and interprism space elements. The possible tilt of enamel prisms is accounted. The dentin elements are represented as a set of shell-enclosed cylinders placed into bulk substance. The presence of peritubular dentin with refraction and absorption indices different to bulk dentin ones inside dentinal tubules is accounted. The results of computer simulation of laser radiation scattering on rough surfaces of enamel and dentin are represented. The dependencies of far-field axial intensity and FWHM of back-scattered light field on parameters of hard tooth tissue surfaces are calculated. The experimental set-up for examination of hard tooth tissues surfaces via parameters of back-scattered He-Ne laser radiation is designed. The investigation of laser radiation back-scattering on enamel and dentin surfaces is carried out. The experimental results are compared with theoretical predictions.

The effects of low-power laser irradiation on prostaglandin (PG)E₂ and interleukin(IL)-1(beta) production in stretched human periodontal ligament (PDL) cells were assessed in vitro. PDL cells derived from healthy premolars were utilized for these experiments. Cells were seeded in flexible-bottom culture plates and elongated (18% increase) under a vacuum at 6 cycles per minute for 1 to 5 days. The stretched cells were irradiated with a Ga-Al-As low-power diode laser (60 mW) once a day for 3 to 10 minutes for 1 to 5 days. PGE₂ and IL-1(beta) levels in the medium were measured by radio immunoassay. Human PDL cells showed a marked elevation in PGE₂ and IL-1(beta) production in response to mechanical stretching. The increase in PGE₂ production was significantly inhibited by laser irradiation in a dose-dependent manner. The increase in IL-1(beta) production was also inhibited by laser irradiation, although the inhibition was only partial under this irradiation condition. Since high levels of PGE₂ and IL-1(beta) are found in the PDL when teeth are moved during orthodontic treatment and since both factors are involved with the induction of pain, the inhibitory effects of laser irradiation on PGE₂ and IL-1(beta) production suggest that laser irradiation may have therapeutic benefits in relieving the pain that accompanies orthodontic treatment.

The effect of low-power laser irradiation on bone formation in vitro were assessed. Osteoblast-like cells were isolated from rat calvariae of 21d rat fetuses. The cultured calvarial cells were irradiated with a low-power laser (830 nm, 60 mW) one time only or once daily for 21d at various energy doses (10.8-108 J/day). The number and the total area of mineralized bone modules that had developed in the culture dish on day 21 were evaluated. DNA content, alkaline phosphatase (ALP) activity and the amount of extra-cellular collagen were also measured. Calcium and phosphorus in bone nodules were examined with an X-ray microanalyzer. Laser irradiation significantly increased the number and the total area of bone nodules in a dose-dependent manner. Cell proliferation and ALP activity in the irradiation group were higher in the early and middle culture periods, while the collagen content was higher in the middle an late periods compared with the control. Calcium and phosphorus were both higher in the irradiation group. These findings indicate that laser irradiation may play a principal role in stimulating differentiation of osteoblasts during the early stage of the culture, resulting in increased bone formation through acceleration of bone nodule maturation.

After a short analysis of the dental laser market and its main characteristics the two most important factors for future growth of the dental laser market are briefly sketched. First increase of use of the equipment; primarily by broadening the range of indications for lasers in dentistry and oral surgery. Second the reduction of prices for the laser systems. With other words economics have to be improved substantially.

The purpose of this study was to find the difference in the size and morphology of the cavities formed by a single pulse of Erbium:YAG laser radiation on enamel or dentin, in air or immersed in water at three different energy levels. The inner surface morphology of cavities without a smear layer might be suitable for adhesive fillings. In water, cavity preparation by Erbium:YAG laser is very effective especially in dentin. Provided irritation to the pulp can be avoided, effective cavitation is better achieved at higher energy level. The efficacy of cavitation at higher energy levels needs to be investigated.

Collimated transillumination is a technique based on the observation that some of photons from a laser beam can traverse an entire tooth, and other tissues in an apparent straight light path and therefore make a shadow of any pathology on the receiver similar to x-rays. To observe the very weak, transmitted, unscattered light rays a special patented system has been developed using collimated, narrow light beams and a highly sensitive, post collimated receiver which rasterscans the entire sample. The image is then transferred to a film. To increase the sensitivity a high resolution mode (HR) has been added.

Ever since Geusic developed the Nd:YAG laser in 1965, there have been numerous fundamental and clinical studies conducted, and reports on its clinical applications in many fields of dentistry, including its potential use for soft tissues to hard tissues. It seems especially effective for these applications when conducting the secondary operations and is actually being clinically applied. Despite the relatively satisfactory results obtained in incising or vaporizing, there have been very few reports concerning the morphological changes on implant structures resulting from laser irradiation. In this report, we would like to consider the extent to which it may be possible to apply Nd:YAG lasers for treating implants. We will discuss the results of the fundamental tests we have conducted together with cases of actual clinical application.