Clinical tests of the caries treatment with a Er:YAG laser system have been very promising. The problem of the Er:YAG laser drilling machine is the speed of preparation. It is not possible to increase the laser energy and repetition rate because this process is directly connected with temperature elevation. Therefore attention has been paid to define the differences between the classical and the laser drilling effect with a safe but effective laser energy and repetition rate. For the experiment, an Er:YAG laser drilling machine with an articulated arm was designed. Thirty samples of extracted human teeth were cut by both this system and classical drilling machine. The circumference, area and structure of surface sections were observed and analyzed. From the comparison of the measured time of preparation significant differences followed from the time of preparation. The time of preparation related to 1 mm² of the cut surface was 5.42 sec for the Er:YAG laser machine and 0.66 sec for the classical method. From this comparison it follows that the laser system is 8 times slower than the classical preparation technique. In both cases the roughness of the surface analyzed by SCAN was found similar. Also, there were no differences between the distribution of the elements, especially calcium and phosphorus.

Nd:YAG lasers have been used previously for selective removal of various material from teeth. To permit ablation of healthy enamel with the Nd:YAG laser, we have adopted a strategy in which micro-drops of photoabsorptive 'promoters' are placed on the enamel to enhance absorption of individual laser pulses. Ink-jet technology dispenses the micro-drops with micron- and millisecond-scale precision. Various promoters using drug and cosmetic dyes, indocyanine green, or carbon-black pigments have been studied. Typical ablation parameters are 1.064 micrometers ; 20-180 mJ per pulse; 100 microsecond(s) ; 10-30 pulses/sec; 0.2-2.0 nl drops. Recent results from the program include: (1) For a variety of promoters, a monotonic relationship obtains between absorption coefficient at 1.064 micrometers and the efficiency of ablation of enamel. (2) With different promoter volumes, the efficiency of ablation rises, plateaus, then falls with increasing volume. (3) At drilling rates of 30 pulses/sec, ablation efficiency approaches rates of 0.1 mm³/sec. LM and SEM observations show a glassy 'pebbled' crater surface indicative of hydroxyapatite that has cooled, condensed, and solidified on the crater walls. Together these results favor the view that a micro-drop promoter-assisted Nd:YAG drill can five clinically useful ablations hard dental tissue.

A systematical investigation of Er:YAG laser drilling of both human dentin and enamel with pulselengths between 50 microsecond(s) and 1.2 ms is presented. At the shorter pulselengths, the influence of heat diffusion is negligible. Consequently, ablation of tissue starts abruptly at a well-defined fluence value, which is independent of the pulselength. Depths and volumes of the resulting craters show a quasi-logarithmical dependence on the applied laser fluence. An improved analytical model of the laser beam screening by the ejected debris is developed, which fits well to the experimental data. With longer laser pulses, ablation turns up only gradually, with differential ablation efficiency slowly increasing with applied laser fluence. Such double-threshold behavior is explained by a simple model of dynamical interplay between the ablation front and heat-diffusion wave. The model enables us to derive expressions for pulselength and laser fluence ranges in which such behavior should be expected for any combination of tissue and laser properties. Also, it predicts qualitatively the amount of thermal side effects in a general laser ablation process.

There is great interest in dentistry to find a replacement for the dental drill which is a great source fear in dental patients. Lasers have been considered a potential replacement. Hard tissue use of lasers on dental tissues has been slow in development has had very limited acceptance by the dental community. The ultimate goal is to develop a laser which can remove both healthy and diseased dental hard tissues and dental materials. The CO₂ laser surgical applications on sot tissues has been reported by many authors. It is hard tissue applications have had very few published reports. The thermal effects of this laser on hard tissues precluded its use on hard tissues. A new CO₂ laser has been developed to reduce the thermal effects on dentin and enamel. Powers of 3-5 watts were used to ablate the buccal surface of extracted human molar teeth. These teeth were gold coated and evaluated under scanning electron microscopy. The results show some melting of the dentin and enamel, however patent dentinal tubules are evident and there appears to be a non-thermal cutting of the enamel at the boarder of the cut surface. In conclusion these very preliminary results appear to show that this new CO₂ laser can cut dentin and enamel efficiently and with very little thermal effect as seen under SEM.

Free electron laser (FEL) with the wide wavelength tunability has been developed and used for various applications. The FEL gives high efficiency for the photo- induced ablation when the laser is tuned to an absorption maximum of the target. This study investigates the FEL induced desorption of ions from tooth dentine to find new possibility for laser dentistry. The FEL was tuned to 9.4 (Mu) m, which is an absorption maximum of phosphoric acid ion known as major component of dentine. The FEL pulse length was several ps. The output average power was varied from 5 to 20mW by filters. A time-of-flight mass spectroscopy systems were developed for the purpose of analyzing the desorbed ions of varying masses. After the 9.4 micrometers FEL irradiation, the dentine surface was ablated, and visible light emission was observed. As a result, positive ions which correspond to Na⁺ and many phosphoric acid ions were measured. The positive ions, however were not observed when the FEL was not tuned to the absorption peak of the target. Therefore, this wavelength dependence points to resonant multiphoton vibrational excitation of molecules by the 9.4 micrometers FEL irradiation.

Clinical applications of Er:YAG laser are now developing in periodontics and restorative dentistry. To date, there have been few studies indicating safety criteria for intraoral usage of the Er:YAG laser. The present study examined the effects of the Er:YAG laser on bone tissues, supposing mis- irradiation in the oral cavity during dental application, especially periodontal surgery. The experiments were performed using the newly-developed Er:YAG laser apparatus equipped with a contact probe. In experiment 1, 10 pulses of laser irradiation were administered to the parietal bone of a rat at 50, 150 and 300 mJ/pulse with and without water irrigation, changing the irradiation distance to 0, 5, 10 and 20 mm, respectively. As a control, electric knife was employed. Macroscopic and SEM observations of the wound surface were performed. In experiment 2, laser irradiation in a straight line was performed at 150 mJ/pulse, 1- pps and 0,5, 10 mm irradiation distance without water irrigation. Wound healing was observed histologically at 0, 3, 7, 14 and 28 days after laser irradiation and compared with that of the control. Non-contact irradiation by Er:YAG laser did not cause severe damage to the parietal bone tissue under water irrigation. Contact irradiation induced a limited wound, however, new bone formation was observed 28 days after laser irradiation, while osseous defect with thermal degenerative tissue remained at the control site. In conclusion, irradiation with an Er:YAG laser would not cause severe damage to surrounding bone tissues in the oral cavity when used within the usual power settings for dental treatment. Furthermore, this laser may be applicable for osseous surgery because of its high ablation efficiency and good wound healing after irradiation.

With respect to lasers emitting within the mid-IR spectral domain fiber applicators are being developed. Intended is the use of these lasers in periodontal therapy and their application inside the gingival pocket. Aim of the study presented here is to compare the effect of an Er:YAG laser on dental calculus with the results following irradiation with a frequency doubled Alexandrite laser. The surface of freshly extracted wisdom teeth and of extracted teeth suffering from severe periodontitis were irradiated with both laser wavelengths using a standardized application protocol. Calculus on the enamel surface, at the enamel cementum junction and on the root surface was irradiated. For light microscope investigations undecalcified histological sections were prepared after treatment. For the scanning electron microscope teeth were dried in alcohol and sputtered with gold. Investigations revealed that with both laser systems calculus can be removed. Using the frequency doubled Alexandrite laser selective removal of calculus is possible while engaging the Er:YAG laser even at lowest energies necessary for calculus removal healthy cementum is ablated without control.

A GaAlAs semiconductor diode laser operating at a wavelength of 796 nm has been sued in conjunction with Indocyanine Green (ICG) dye to ablate carious dentin and enamel from extracted human teeth. The laser-dye ablation technique offers selective ablation as it is controlled by the placement of the ICG dye. In contrast with other laser techniques, the risk of collateral thermal damage is substantially reduced. The diode laser is suitable for ordinary fiber delivery and is cheaper and more compact than the higher power CO₂; Er:YAG, Nd:YAG and Argon lasers currently being used by researchers. This paper reports the ablation of dental caries in fifty extracted teeth with various laser diode powers and dye concentrations. The mass of material ablated, temperature rise in the pulp and surface temperature were measured. The ablation was found to be efficient with negligible thermal damage to surrounding tissue. At the same time average surface temperatures reached during ablation may be sufficient to sterilize the treated surface. Hardness measurements and scanning electron microscopy of the laser treated cavity surfaces show the new surfaces to be suitable for placement of a dental filling.

The aim of this investigation is to define optimal parameters of KTP laser irradiation during caries removal. 12 decayed human teeth, recently extracted were used. Their rot canals were prepared for insertion of a thermocouple probe into the pulp chamber. The demineralized tissues have been colored by Acid Red 52 before proceeding to different conditions of irradiation. Pulpal temperature increases were found under the following parameters with 15 seconds continuous lasing: 400mw, 0.10 m sec pulse width, PRR <EQ 60 Hz or 400 mw, 0.12 m sec pulse width, PRR <EQ 50 Hz for efficient caries removal. A resting time average of 70 s was necessary to allow pulp temperature to get back to its baseline.

To prepare the enamel, the energy used was mainly 345 mJ and repetition rate 2 Hz, for dentine the optimal energy of Er:YAG drilling machine was 200 mJ and repetition rate from 1 to 2 Hz, depending on cavity depth. Subject of treatment were caries of enamel and dentine and it was possible to remove the old insufficient fillings. The average number of pulses was 111.22, ranging from 16 to 489. During preparation, vibrations of microexplosions were felt by 8 patients, however, neither pain or unpleasant sensations were experienced. The filling materials used were composite resins and glassionomer cements. Their clinical evaluation 6 months post insertion was similar to that of the classical drilling system.

Previous studies have shown that dentin can be thermally modified by pulsed CO₂ laser irradiation to form a more highly mineralized tissue. The implications are important for the potential laser modification or removal of dentinal and root caries. Temperature excursions were followed after (lambda) equals 9.3, 9.6, 10.3, and 10.6 micrometers laser irradiation with pulses of 100 (Mu) s duration at irradiation intensities of 0.5 to 8 J/cm². In addition, photoacoustic and transient reflectance measurements were used to monitor the loss of water and organics and to detect the thresholds for surface modification and tissue ablation. The surface temperatures of dentin were markedly higher than those measured on enamel for similar irradiation intensities due to the lower reflectance losses of dentin and the lower thermal diffusivity at the respective wavelengths. Hence, lower fluences are required for the thermal decomposition of dentin. Ablation typically occurred with the first few laser pulses during multiple pulse irradiation and eventually ceased after modification of dentin to a more hypermineralized tissue. The debris ejected during the initial laser pulses shielded the surface by as much as 60 percent at the low fluences employed in this study. Optical and electron microscopy and IR spectroscopy indicated that incident laser fluences of 1-2 J/cm² at 9.3 and 9.6 micrometers produced sufficient crystalline changes in the carbonated apatite mineral in dentin for caries preventive treatments.

Calcium carbonate (CaCO₃) and its structural relatives, the phosphates and hydroxyapatites, are natural crystals which are similar to the minerals found in such hard tissues as teeth and bone. We have recently demonstrated that laser- induced material removal in calcium carbonate occurs with high efficiency when irradiating with a free-electron laser at the fundamental asymmetric stretch mode of the carbonate group near 7 micrometers ; related studies show that the same thing is true in the isoelectronic sodium nitrate, and we expect it to operate in the phosphates as well when irradiated near the resonant 9 micrometers band. The mechanism of material removal appears to be the ejection of CO followed by a calcination reaction which produces CaO. Among the features which make CaCO₃ such an interesting model material is that it also has a characteristic, temperature-dependent thermoluminescence - thus making it possible, by the study of the light emitted by the crystal prior to and after ablation, to estimate the temperature reached by the crystal in the early stages of laser ablation. Wavelength-dependent photoluminescence, photoacoustic and plume-spectroscopic studies show that efficient evaporative 'hole drilling' occurs at the infrared wavelengths corresponding to carbonate or nitrate vibration modes. However, where electronic or vibrational defects are excited by visible or infrared lasers, respectively, the mechanisms of material removal are photomechanical fracture in the former case and exfoliation or subsurface explosive vaporization in the latter.

Several studies in our laboratories have demonstrated that CO₂ laser treatment of dental enamel can inhibit subsequent caries-like progression from 10-75 percent compared to controls. The present study tested the hypothesis that laser radiation at specific wavelengths is absorbed by the mineral, converted efficiently to heat at the surface, causing thermal decomposition of the carbonated apatite enamel crystals to a less soluble form. Samples of enamel 5 X 5 mm were examined before and after laser irradiation by specular reflectance FTIR. Sample surfaces were irradiated by pulsed CO₂ laser at 9.3, 9.6, 10.3 or 10.6 micrometers , 100 microsecond(s) pulse duration, 25 pulses per spot, with fluences of 0-6 J/cm². In separate experiments surface temperatures were measured dependent, and fluence dependent, with total loss occurring with 9.6 micrometers irradiation occurred at 4 J/cm². Optimum inhibition of caries progression following 9.6 micrometers irradiation occurred at 4 J/cm². We conclude that irradiation of dental enamel by specific wavelengths and fluences of CO₂ laser light alters the chemical composition of the crystals, decomposing the CO₃ component, thereby markedly reducing the reactivity.

In this four-year follow up in vivo controlled study, 112 human permanent first molars, from children between the ages of 6 and 11 years old were used to investigate the viability of the CO₂ laser in promoting carie-free occlusal surfaces in permanent molars, as an isolated form of treatment or associated with conventional fissure sealants. The findings suggest that occlusal caries prevention only by means of CO₂ laser irradiation is not effective; that the utilization of photo-activated sealants, as well as its association with CO₂ laser, applied over the occlusal fissures, are effective means of preventing occlusal caries and that the application of CO₂ laser over occlusal fissures, prior to the application of a photo-activated fissure sealant, improves the retention of the sealant.

12 teeth have been extracted and treated 'in vitro' by ultrasonics and Nd:YAG pulsed laser with fiber optic delivery to compare the cleaning efficiency of the root canal. The optic fiber was equipped with a water-air coaxial cooling system. The ultrasonic device was equipped with a 3 percent NaCl solution douche system. The samples have been prepared according to the technical specifications of the suppliers of laser and ultrasonics and observed by an endodontic endoscope. Cross sections of the samples have been utilized for microradiographic investigations and scanning electron microscopy observations. Local melting has been observed after laser irradiation.Also, vitrification preferentially occurred in the apical zones. The occurrence of vitrification was found strongly dependent on the translation velocity of the laser beam inside the root canal. The laser beam has shown a cleaning efficiency greater than that obtained by ultrasonic procedure.

The canals of 30 recently extracted human teeth were filled with a photosensitizer. A series of 5 shots, separated by a resting time of 1 second also, was delivered by means of the KTP:YAG fiber tip. The temperature increases were measured on the topical point of the root surfaces by the use of a thermocouple. For laser settings, the rises were always below the safety threshold of 7 C. We conclude that the KTP:NdYAG laser can be harmless for periodontal tissues under some conditions.

Current endodontic therapy involves debridement and disinfection of the root canal by means of mechanical instrumentation and chemical irrigation. However, several studies have shown that these techniques fail to achieve complete cleansing. Recently, lasers have been suggested for use within root canals. This study was conducted to determine the efficacy of Holmium:YAG laser irradiation in removing intracanal debris and smear layer. Root canal surfaces of freshly-extracted human teeth were exposed to pulsed Ho:YAG laser radiation. Subsequently, laser induced structural changes were investigated using scanning electron microscopy. Temperature measurements during irradiation were performed by means of thermocouples. The result of this survey give a preliminary indication of the ability of the Ho:YAG laser to improve current endodontic treatment survey give a preliminary indication of the ability of the Ho:YAG laser to improve current endodontic treatment modalities. However, limitations exist with regard to circumscribed and well-quantified irradiation of root canal surfaces, due to the lack of perpendicular delivery of the laser beam. Additional studies will be required to develop suitable optical transmission systems, in order to achieve complete cleansing and to avoid damage to the periradicular tissues, respectively.

The purposes of this study was to define the optimal irradiation conditions of a KTP:NdYAG laser after root planning treatment. The surfaces of 40 single-root human teeth were scaled with conventional tools before lasing. The pulpal temperature increase was measured by means of a thermocouple. The influence of variables of coloration by Acid Red 52, scanning speed, dentin thickness, and probe position, have been analyzed for a constant exposure time of 15 seconds. The temperature was below 3 C for the adjustments, power output: 400 mw, scanning speed of irradiation: 2 mm/sec., and Pw 0.10 m sec, PRR < 60 Hz or Pw: 0.12 m sec, PRR < 55 Hz.

The CO2 laser has been suggested for occlusion of dentinal tubuli and sterilization of the beveled root surfaces, avoiding degrees of irritants from the root canal system into periapical tissues. This study has evaluated marginal leakage in 40 human single rooted teeth divided into 4 groups of 8 teeth which received retrofillings, and 2 control groups of 4 teeth each. Group A: Super EBA; group B: Super EBA and CO2 laser irradiation; group C: Glass Ionomer Cement; group D: Glass ionomer Cement and laser; group E: positive control; group F: negative control. In groups B and D the power set was 2 watts, 20 msec, with a CT3105 ceramic point. Teeth were placed in 5 percent methylene blue dye for 24 hs and the dye penetration was lower in B. The higher penetration was seen in C. Analysis of variance found statistical difference between groups. In this study the laser irradiation was able to change the amount of dye penetration. It can be assumed that Super EBA and Glass Ionomer Cement have their sealing abilities improved by laser irradiation.

Vertical root fracture has been requested tooth extraction or root hemisection. There is no conservative treatment. The purpose of this paper was to analyze the CO₂ laser effects on root fracture, associated with other materials. Forty two extracted human canines divided into 6 groups have their root vertically fractured. In groups A and B the CO₂ laser was used with power of 5 W and 7 W respectively and the fracture line was covered with glass ionomer cement. In groups C and D the laser was used with 5 and 7 W and fracture line was covered with a dual composite. Groups E and F were controls, treated with glass ionomer cement and FLC dual composite. The teeth were placed in 5 percent methylene blue dye for 48 hs. The dye penetration was lowest in groups with glass ionomer cement and laser (A and B), at about (1.06mm). The difference between groups was statistically significant at 1 percent. All experimental groups showed dye penetration. The laser seemed to favor the sealing of the fracture line.

The in vitro tissue ablation characteristics of two pulsed mid-infrared lasers were studied, especially, with the intent to evaluate photomechanical and photothermal side effects. The Erbium:YAG laser emitted radiation at 2.94 micrometers in a spiking mode. The free-running beam from the laser was focused onto freshly-excised porcine samples via a 108-mm sapphire lens. The spot size was determined by a photosensitive metallic foil. The Holmium:YAG laser emitted radiation at 2.10 micrometers . The radiation was coupled to a 400- micrometers core quartz fiber. Both lasers were operated at 5 Hz, and 6 pulses were delivered to each porcine specimen using 'dry' and 'wet' ablation mode, respectively. After irradiation, the samples were investigated by means of light and scanning electron microscopy. The results of this survey indicate that both laser types ablate porcine oral mucosa efficiently. The Er:YAG laser produces less surrounding mechanical and thermal damage. In contrast to safe and suitable optical fibers available for the Ho:YAG laser, fiber optical delivery systems for the Er:YAG laser are still in the development phase. Nevertheless, current research work in this field seems promising and the near future may hold an adequate optical transmission systems for the delivery of both wavelengths, 2.10 micrometers and 2.94 micrometers , in order to provide on the one hand atraumatic ablation and on the other hand sufficient hemostasis.

During the last six years we have developed a new CO₂ laser technique for the treatment of symptomatic oral cavity hemangioma. Our new technique, named 'laser encircling technique', has especially succeeded during hemangioma buccal maxillary surgeries. The treatment consisted in the application of a line of points of CO₂ laser circling the lesion. Depending on the position and size of the lesion, we used from 0.4 to 4.0 Joules/mm² laser energy density per pulse, causing reduction in the size of the lesion throughout the sclerosis of nutritional vessels which led to reduction in size, volume and color of the hemangiomas with no significant bleeding or inflammatory reaction. In this work forty male and female patients, twelve to fifty years old, presenting medium to small size hemangiomas situated in different sites of the oral cavity such as the tongue, mouth vestibule, pharynx, tonsil area and lips were treated by the procedure described above. The number of laser applications was defined by the peculiarities of each case, varying form 3 to 6 sessions at 4 week intervals, always under local or topic anesthesia. The patients complained about minimal posit operative discomfort and had good cicatrix evolution. The good results achieved by this technique lead to the conclusion that CO₂ laser for these types of hemangioma is an efficient and very secure method of treatment. An important aspect of our technique is the fact that using relatively low laser power we do not perform real surgery but a less aggressive alternative of treatment.

A new laser activated solder weld technique is described for the microsurgical repair of the inferior alveolar nerve in rats. The laser weld technique used an albumin based solder, containing indocyanine cardiogreen, plus an infrared diode laser. Seven animals had inferior alveolar nerve repairs performed using the laser weld technique and these were compared against corresponding unoperated controls plus three cases of nerve section without repair. Histochemical analysis was performed utilizing neuron counts and horseradish peroxidase tracer (HRP) uptake in the trigeminal ganglion following sacrifice and staining of frozen sections with cresyl violet and diaminobenzidene. The results of this analysis showed comparable mean neuron counts and mean HRP uptake by neurons for the unoperated control and laser weld groups with considerable reduction of mean values in cases of nerve section with no repair. Sections of the repaired inferior alveolar nerves, stained with Masson's trichrome, showed no adverse reactions by axons or epineurium to the coagulative repair with the solder and demonstrated regeneration of myelinated axons at the time of sacrifice. In summary a new technique of laser weld repair of the inferior alveolar nerve is described which, on initial analysis, appears to be a reliable alternative to traditional techniques.

The clinical application of a new developed fiber guided CO₂ laser in soft tissue surgery will be demonstrated (wavelength 10.6 micrometers , pulse duration 5 ms up to cw, pulse repetition rate 1-99 Hz, maximum average power at the outlet of the handpiece 9.4 watts, focus diameter 0.3 mm, two confocal pilot laser beams; ASAH medico, Hvidovre, Denmark). In this study laser parameters were set to a pulse duration of 5 up to 20 ms and a maximum repetition rate of 20 Hz. Leukoplakia removal was done with a defocused beam, while for excisions and incisions the laser was used in focus. Excisions of fibromas, lipomas etc. were performed. Especially for gingiva extensions employing free gingival grafts this new laser device was engaged. After two weeks of wound healing all gingival graft procedures were successfully complete. Healing process following large vestibuloplasty procedures concerning a total jaw lasted as long as known from conventional techniques. For the daily clinical use in soft tissue surgery this fiber guided CO₂ laser system appears to be a versatile and reliable tool.

We have, in this preliminary study, investigated the use of optical coherence tomography for diagnosis of periodontal disease. We took in vitro OCT images of the dental and periodontal tissues from a young pig and compared them to histological sections. These images distinguish tooth and soft tissue relationships that are important in diagnosing and assessing periodontal disease. We have imaged the attachment of gingiva to the tooth surface and located the cemento-enamel junction. This junction is an important reference point for defining attachment level in the diagnosis of periodontal disease. the boundary between enamel and dentin is also visible for most of the length of the anatomical crown, allowing quantitation of enamel thickness and character.

In this study, the efficacy of laser-supported curettage was examined with relation to the periodontitis-reference germs. Initially, a manual subgingival curettage followed by irradiation using the Nd:YAG-laser was carried out on 18 diseased periodontia. At two further appointments with weekly intervals, only laser irradiation was performed. Prior to and upon completion of therapy, subgingival plaque samples were taken at each appointment from all the treated periodontia. These were then examined microbiologically to establish the number of prevotella intermedia. A distinct bacterial reduction as well as a decrease in recolonization was shown. In conclusion the application of the Nd:YAG laser with a 400 micron fiber and an energy setting of 2 watts, 20 pps is beneficial when used in conjunction with manual periodontal treatment because of its disinfecting effect.

Pioneer work published by Mester and cols. opened a new frontier in the clinical treatment of many disorders with the use of LILT. Although LILT is not well accepted in many countries, its use is growing steadily in many others, especially in Europe and lately in Brazil. This paper reports on the treatment of 107 patients using LILT. Eighty- nine female and 18 male patients aged between 7 and 81 years old suffering from disorders of the maxillofacial region were treated with 632, 8, 670 and 830 nm diodes lasers at the Laser Center of the UFPE. The disorders included TMJ pain, Trigeminal neuralgia, muscular pain, aphatae, inflammation, hypersensibility, postoperatively, and in small hemangiomas. Most treatment consisted of a series of 12 applications and in eight cases a second series was applied. Patients were treated with an average dose of 2.5 J/cm². Eighty one out of 107 patients were asymptomatic at the end of the treatment, 15 improved considerably and 11 were symptomatic. These preliminary results indicate that LILT is an important tool and brings many benefits for the treatment of many disorders of the maxillofacial region.

The objective of this study was to determine the effectiveness of localized laser pulp surgery in the canine model. Effects of laser parameters on treatment outcome were also investigated. Pulpal exposure 3 mm in diameter were prepared in healthy teeth and left open to infection from the oral cavity for 72 hours. Pulpal tissue was then removed using high speed handpiece with sterile irrigation, or a CO₂ laser. Teeth were monitored clinically, radiographically for 3 months. Results for each criterion were evaluated on a scale of 0-(-2). After sacrifice, histological assessment was made soft and hard tissue response. Results for each category were evaluated on a standard scale of 0-(-2). All evaluations were performed by 1 blinded, pre-standardized clinician. Statistical assessment using the chi-square test and Fisher's Exact Test associated laser treatment with a significantly better clinical, radiographic and histological treatment outcome. NIH RRO1192, seed grant funding form Loma Linda University, the Edna P. Jacobsen Charitable Trust for Animals, Inc.

Accurate determination of the optical properties of dental enamel is important for modeling the energy redistribution of laser radiation incident on the tissue. The high absorption coefficients of dental enamel in the mid-IR preclude the use of conventional transmission methods for the determination of optical properties, therefore non- conventional methods must be used. Enamel was irradiated with 9.3 micrometers , 9.6 micrometers , 10.3 micrometers , and 10.6 micrometers light from a CO₂ laser with a pulse duration of approximately 100 microsecond(s) . Samples were irradiated with fluences up to 2 J/cm². These fluences produce temperature excursions below the melting point for the tissue. Surface temperatures were monitored using time resolved radiometric measurements with 1 microsecond(s) temporal resolution. A 1D heat conduction model was used to estimate the temperature increase in enamel. By varying the absorption coefficient, the model temperature versus time profile was fitted to the experimental profile. The absorption coefficients of enamel were found to fall well below values in the literature determined using angular-resolved reflectance measurements at the same wavelengths. The new absorption coefficients were used in our heat conduction model to determine temperature excursions below the surface of the tooth. This study is a vital step in determining the optimum laser parameters for caries preventive treatments.