The aim of this research was to evaluate dentin permeability effects at the apical cut surface prepared with Er:YAG laser and irradiated with Nd:YAG laser compared to conventional techniques. 62 extracted human teeth were divided into four groups of 7 teeth each. For Group 1 apicoectomy was performed using high speed handpiece and diamond burs. Group 2 was prepared as group 1 and lased with Nd:YAG (1W,15Hz of energy before retrograde cavity filling). For group 3 Er:YAG* laser irradiation (wavelength of 2.94μm, pulse width of 250-500μs)was used in 400mJ of energy, frequency of 6Hz, on focus mode under distilled water refrigeration and group 4 was performed as group 3 and lased with Nd:YAG (1W, 15Hz of energy before retrograde cavity filling). Permeability was evaluated by the extent of methylene blue dye penetration into the tubules. There were statistically significant differences in permeability between groups. Nd:YAG laser irradiation significantly reduced apical dentin permeability when compared to unlased groups. Er:YAG laser by itself showed higher percentage of dye penetration.

The study was conducted on 30 vital maxillary or mandibulary teeth destined for extraction due to periodontal problems. 21 were experimentally treated with pulsed CO₂ laser delivered by a newly developed fiber and 9 teeth represented the control group. The micro probe is a flexible, hollow, metal fiber, 300 μm in diameter and 20 mm in length, coupled onto a handpiece, with the following radiation parameters: wavelength-10.6μm; pulse duration-50m.sec; energy per pulses 0.25 joule; energy density-360 J/cm² per pulse; power on tissue-5W. The laser group was divided into three, receiving 20, 40 or 60 pulses, respectively. On light microscopy: in all the control group cases, large amount of residual pulp tissue was seen, it was diminished in some of the low energy group and was totally eradicated in the high energy group. This was confirmed by the scanning electron microscope (SEM) examination. The dentin tubuli were partly occluded with the low energy levels and completely with the high levels, as shown by the high-speed centrifuge dye penetration test and by the SEM tests.

The goal of the study was to verify differences between the alexandrite and Er:YAG laser energy distribution in the root canal and in the surrounding dentin and bone tissues. For the experiment, two lasers were prepared: the Er:YAG laser (λ=2.94 μm) with a delivery system fluorocarbon polymer-coated silver hollow glass waveguide ended by a special sapphire tip and the alexandrite laser (λ=0.75 μm) with a silicon fiber. The Er:YAG laser was operated in a free-running mode, the length of the generated pulses was 250 μsec and the output energy ranged from 100 to 350 mJ. The pulse length of the free- running alexandrite laser was 70 μsec and the output energy was ranged from 80 up to 200 mJ. For the experiment prepared root canals of molars were used. It was ascertained that the radiation of the alexandrite laser passes through the root canal and hits the surrounding tissue. Nocardia asteroids, Filaments, Micrococcus albus, Lactobacillus sp and Streptococcus sanguis colonies were treated by the Er:YAG or alexandrite laser radiation. The surface was checked by scanning electron microscopy. From the result it follows that the Er:YAG laser destroyed microbial colonies but the differences is in the depth of the affected area.

The success of endodontic therapy is based on the elimination of bacterial colonization from the endodontic system and periapical tissues. Recent studies have been showing the bactericidal effect of laser in root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canals from upper central incisor. For the experiment 12 teeth were selected, respect at the apical third, sterilized, and 10 μm Streptococcus sanguis liquid culture were inoculated in the root canals. The laser test groups were irradiated with Nd:YAG laser at standard setting of 15Hz, 100mj and 1,5 W for 10, 20 and 30 seconds each in slow helicoidal movements from the apex to the top using a 300 micrometers fiber. After the procedure the specimens were placed in Tryptic Soy Agar, the number of colony forming units was evaluated. The experiment showed a significant reduction on viability of Streptococcus sanguis at the respective time of 20 and 30 seconds.

The purpose of this study was to determine the efficiency of 15 F CO₂ laser microprobe, in cases of periapical lesions, by eliminating the pathological reaction caused by certain species of bacteria, reduction of reinfection and stimulation of osteogenesis in the periapical region. Until now, no suitable delivery fiber existed for CO₂ laser endodontic radiation in the apical region where it is most difficult to eliminate the pulp tissue using conventional methods. To overcome this problem, Sharplan laser designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal, thus favorably increasing the thermal effects. The study was conducted on 900 teeth, divided in two groups. 468 were new case, carefully selected according to strict parameters such as: wide periapical translucency over 1mm, supported by digital x-ray, with a lesion of 3mm and more. All root canals were mechanically prepared in the conventional method up to size 35, Physiological saline solution served as finding solution and were treated by 15 F CO₂ laser microprobe for 60 pulses repeatedly. The temperature at the surrounding tissue of the root did not exceed 38 degrees C filling of the canal was possible at the same appointment, without antibiotical treatment. 432 of the cases, which were referred to us by other dentists, after an unsuccessful treatment according to the classical therapy, were treated by the same laser therapy. Follow up was performed by clinical examination, and digital x-ray taken, during and after treatment as well as after 3, 6, 9, 12 month. The result demonstrate 98% success rate in both study groups, according to objective criteria for a successful treatment such as: reduction of apical translucency after 2- 6 months, freedom form clinical complains, and no need for periapical surgery.

The aim of this study was to determine safe parameters for intracanal laser irradiation. Single rooted extracted teeth were irradiated with the pulsed Er:YAG laser (2.94 μm) and Nd:YAG (1.06 μm) laser. The teeth with remaining root thickness ≥ 1mm on the apical portion were selected and divided in eight groups according to the laser parameters: output energy of 40-100 mJ/pulse; repetition rate of 10-15 Hz. The root canals were irradiated for 4 periods with a 20s breaks in between with the fiber stationary 1mm from the apical foramen, during 3s or from the apical to coronal surface in a continuous, circling fashion, with 2mm/s. Morphological changes were also observed by scanning electron microscopy.

The aim of study was to evaluate the effect of low-level laser radiation on the healing process after human lower molar extraction. Frequencies of 5 Hz, 292 Hz and 9000 Hz were used in this experiment. Monitoring the secretory IgA and albumin levels in saliva and changes in bone density were used as a marker of biostimulatory effect. Bone density after extraction and six month after surgical treatment was examined using the dental digital radiography. Wound closure was followed by healing of bone structure in extraction site. Changes of secretory IgA, albumin levels and bone density were compared in groups of patients with laser treatment and control group without any laser therapy. Differences in levels of the saliva markers were found to be significant comparing irradiated and non-irradiated groups, as well as comparing groups irradiated by various modulatory frequencies. Density of alveolar bone was examined on five slices acquired from every digital radiography image. Histogram were evaluated wit a computer program for microscopic image analysis. Density differences were verified in area of the whole slice. There were no significant differences found between bone density in irradiated and non irradiated groups perhaps due to our used therapeutical diagram.

This paper reports the result of the use of LLLT on the treatment of TMJ pain and present LLLT as an effective method of treating such problem. One hundred and eighty one female and 23 male patients aged between 7 and 81 years old (average 36.9 years old) suffering TMJ pain were treated with 632.8, 670, and 830nm diodes lasers at the Laser Center of the UFPE. The treatment consisted of a series of 12 applications twice a week. Patients were treated with an average dose of 3 J/cm². One hundred forty one out of 204 patients were asymptomatic at the end of the treatment, 37 improved considerably and 26 were symptomatic. These result show although LLLT does not cure TMJ disorders it is effective in reducing TMJ pain.

The aim of the present work was to evaluate histometrically the effect of the irradiation with semiconductor diode GaAlAs 790 nm low-powered laser in the chronology of alveolar repair of rats. Lasers of low intensity possesses an eminently analgesic, anti-inflammatory and bioestimulant effect, producing an increase of the local micro-circulation and in the speed of healing. Groups of five animals had their upper right incisors extracted under anesthesia and the mucous sutured; three groups received 1.5 J/cm² of irradiation immediately after the extraction with laser for sweeping on the operated area. After that, the animals were sacrificed in the periods of 7, 14 and 21 days after the dental extraction. The material was decalcified and processed for inclusion in paraffin. Longitudinal sections of 7 micrometers in the alveolus were made and stained with HE. The histometric analysis was performed with the Merz grid, and 2000 points were counted in each cervical, middle and apical thirds of the alveolus, assessing the percentage of the bone tissue. The result shows that low-powered intensity laser produced acceleration in osseous formation (10%) in some periods.

This study aimed to assess the effect of the use of lasers (635; 670nm) on Candida albicans In Vitro. Cultures of microorganisms were irradiated with and without artificial illumination and non-irradiated cultures acted as controls. A single irradiation with the dose of 1.5J/cm² was used and measurements of DO and NC assessed the effects of the irradiation. The measurements were carried out with 24 (T₁), 48 (T₂) and 72 (T₃)after irradiation. The results showed a significant difference between groups with relation to the DO on the presence of illumination. There are significant differences between the three groups at T₁ and T₃ related to the NC. In all situations significant differences were observed highest values occurred when illumination was not used. Cultures irradiated with the laser 635 nm grow faster than those irradiated with the laser 670 nm. Measurements of DO/NC were sensitive to detect changes in Candida albicans cultures irradiated or not. It is concluded that a single irradiation of Candida albicans cultures with laser of 670 and 635 nm results in proliferation of the microorganisms In Vitro.

To perform this study, 40 extracted single rooted human teeth were used to compare dye leakage between apicoectomy following amalgam retrofill and apicoectomy using CO₂ laser irradiation. All the 40 teeth were endodontically treated and than were separate in two groups of 20 teeth each. A bur was used to ressect the apexes of the sample of group I followed by silver amalgam retrofill. the 20 teeth of group II had their apexes ressected with a Carbon Dioxide laser beam. All the samples were submerged into a methylene blue dye solution, washed, longitudinally sectioned and graded upon the level of leakage by two separate examiners. The result showed a perfect concordance between both examiners and also, a non significant difference on the level of leakage in the two groups.

The purpose of this investigation was to show the percentage of cured patients treated with low level laser therapy clinically diagnosed dentinary hypersensitivity. The authors report on this investigation more than 300 human teeth treated at the Laser Center of Camilo Castelo Branco University during the years of 1995, 1996 and 1997. Pulpal vitality was verified using thermal tests, and only reversible process was treated. The teeth were dried with cotton pellets and laser beam was applied, using He-Ne (632.8 nm)laser, and ArGaAl Lasers(780 nm and 830 nm). All teeth received 4 joules/session, and were treated until 5 sessions. 79.13% of our patients were treated in 3 sessions with success; 8.58% were cure in 4 sessions; and 4.29% were successfully treated in 5 sessions, obtaining a 92% of success. The authors concluded that low level laser therapy is an effective and useful treatment to dentinary hypersensibility.

The objective of this present work to evaluate in the level of pain and tumor the effect of the low-power density laser irradiation of GaAlAs 790 nm in implanted patients during the postoperative period. Forty five clinic situations were selected and divided in three different groups: Group I, control, without laser application, but with analgesic and anti-inflammatory medication; Group II, patients were irradiated on the day of the surgery, after the same concluded, and on the two subsequent days; and Group III, patients were irradiated on the day of the surgery, on the day of the surgery, before and after the end of the same, and in the two subsequent days after. All the applications were accomplished using the same energy parameters and by the same operator. The measures, with relationship to the pain and the tumor, they were accomplished in the immediate postoperative, in the postoperative (24 hours and also 72 hours after) always by the same examiner. The statistical analysis sustained the clinic observations. In our study, the low power density laser of GaAlAs 790 nm suggested the same clinical results when pain and tumor formation were controlled by analgesic and anti- inflammatory medication.

40 patients with edentulous maxillary jaws were referred to our private practice limited to maxillofacial surgery, due to atrophy of the alveolar ridge. Before prosthetic renewal of the upper removable prosthesis the restorative dentist requested a sufficient vestibule. After supraperiostal preparation, soft tissue advancement and fixation with absorbable sutures. The recipient site was covered with a free gingival graft. Group I was operated on traditionally using a scalpel. In group II incision and soft tissue preparation was performed using a diode laser. Wavelength: 810 nm; Continuous wave mode; 400 micron optic fiber; Output power 1.6 Watt. All operations were performed by one surgeon experienced in both operation techniques. Every patient was followed-up 1, 4, 8 weeks, 6 and 12 months. The vestibular height directly adjacent to the nasal cavity and 2cm distal to these first measuring locations were taken. Each patient was asked to evaluate their individual discomfort and postoperative pain level. Both groups showed no significant difference in vestibular height after 1, 4, 8 weeks, 6 months and 1 year. The postoperative height of 1.28 cm was reduced to 0.84 cm after 1 year. Furthermore both groups showed uneventful healing and take of the free gingival grafts. The assessment of the pain and discomfort level by the patients brought a significant difference between both groups in favor of the laser assisted operation technique.

Aim of study was to evaluate osseointegration of the KrF laser hydroxyapatite coated titanium alloy Ti6Al4V dental implants. For deposition KrF excimer laser in stainless- steel deposition chamber was used. Thickness of HA films were round 1 μm . Mini-pigs were used in this investigation. Implants were placed vertically into the lower jaw. After 14 weeks unloaded osseointegration the metal ceramic crowns were inserted. the experimental animals were sacrificed (1 year post insertion). The vertical position of implants was controlled with a radiograph. Microscopical sections were cut and ground. Sections were viewed using microscope with CCD camera. 1 year osseointegration in lower jaw confirmed by all implants presence of newly formed bone around the all implants. Laser-deposited coating the layer of fibrous connective tissue was seen only seldom. In the control group (titamium implant without cover) the fibrous connective tissue was seen between implant and newly formed bone.

Recently, laser pretreatment of dental enamel has emerged as a new technique in the field of orthodontics. However, the changes in the morphology of the enamel surface is very much dependent on the wavelength of laser, emission mode of the laser, energy density, exposure time and the nature of the substance absorbing the energy. Based on these, we made a comparative in vitro study on laser etching with acid etching with reference to their bond strength. Studies were conducted on 90 freshly extracted, non carious, human maxillary or mandibular anteriors and premolars. Out of 90, 60 were randomly selected for laser irradiation. The other 30 were used for conventional acid pretreatment. The group of 60 were subjected to Nd-YAG laser exposure (1060 nm, 10 Hz) at differetn fluences. The remaining 30 were acid pretreated with 30% orthophosphoric acid. Suitable Begg's brackets were selected and bound to the pretreated surface and the bond strength were tested using Instron testing machine. The bond strength achieved through acid pretreatment is found to be appreciably greater than the laser pretreated tooth. Though the bond strength achieved through the acid pretreated tooth is found to be significantly greater than the laser pretreated specimens, the laser pretreatement is found to be successful enough to produce a clinically acceptable bond strength of > 0.60 Kb/mm. Examination of the laser pre-treated tooth under SEM showed globule formation which may produce the mechanical interface required for the retention of the resin material.

Er:YAG laser as well as the frequency doubled Alexandrite laser have been suggested for the use in periodontal therapy and so for the elimination of calculus and the treatment of infected root cement. Intended is the laser application inside the gingival pocket. In consequence, both these lasers may be used in areas close to cervical or approximal location, or even on the fillings' surfaces. Light cured composite and compomer materials are in use for these types of fillings among others. Aim of the study presented here was to compare the effect of an Er:YAG laser (wavelength 2.94 μm, pulse duration 250 μs, free running. fluence 4.5 J/cm² and 21.4 J/cm²) on compomers and composites with the result following irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 200 ns, fluence 3 Jcm^-2 and 6 J/cm²). The surface of standardized compomer and composite samples were irradiated with both laser wavelengths (either frequency doubled Alexandrite or Er:YAG laser) using the same standardized application protocol. Scanning electron microscopic investigation showed that irradiation with both lasers causes surface changes in composites and compomers removing calculus with these lasers.

The authors evaluated, in vitro, the tensile strength of a hydrophilic adhesive on dentin surface, with and without previous treatment with high power Nd:YAG laser. Power of 1.0 W and 2.0 W with respective frequencies of 25 Hz and 50 Hz were used. Thirteen human extracted molars were prepared and randomly separated in five groups: GI, Nd:YAG laser with 1.0 W plus SBMPP (3M) adhesive system; GII, laser with 2.0 W, plus adhesive system; GIII, laser with 1.0 W; GIV, laser with 2.0 W; GV, adhesive system to treat dentin surface. To each group five samples with a composite bottom each, totalling in 25 samples, which were kept in distilled water, by 37°C, during 30 days. After that, thermal cycling was applied. After this period, the samples were submitted the tensile strength test to evaluate the necessary threshold of power to break up the adhesive bond of composite button from dentin surface. The statistical evaluation was done through variance analysis. Results showed that the values of tensile strength of the GV (26.4 kgf/cm²) were better than GI (4.6 kgf/cm²) which was the best laser group: GIII (2.4 kgf/cm²); GII (1.7 kgf/cm²) and GIV (1.2 kgf/cm²).

Periimplantitis is one of the major factors for the loss of dental implants. Due to the minor defense ability of the tissue surrounding the implant compared to natural teeth treatment of periimplantitis in the early stage is very important. Reducing bacteria with a laser might be the most successful step in therapy of periimplantitis. Aim of the study was to observe changes in surface morphology of seven different implants after irradiation with three different lasers. Two kinds of flat round samles were prepared by the manufacturers either identical to the body surface or to the cervical area of the corresponding implants. The samples were irradiated using different power settings. The lasers used were a CO₂ laser (Uni Laser 450P, ASAH Medico Denmark; fiber guided, wavelength 10.6 μm, max. average power 8.3 W, "soft-pulse" and cw) an Er:YAG laser (KaVo Key Laser II, wavelength 2.94 μm, pulse duration 250-500μs, pulse energy 60-500 mJ, pulse repetition rate 1-15 Hz, focus diameter 620 μm, air-water cooling; Biberach, Germany) and a frequency doubled Alexandrite laser (laboratory prototype, q-switched, fiber guided, wavelength 377 nm, pulse duration 1 μs, pulse repetition rate 30 Hz, water cooling). After irradiation the implant surfaces were investigated with a Scanning Electron Microscope. Ablation thresholds were determined. After CO₂ laser irradiation no changes in surface morphology were observed whereas using the pulsed Er:YAG laser or frequency doubled Alexandrite laser even at low energies loss of integrity or melting of the surface was observed. The changes in surface morphology seem to depend very strongly on the type of surface coating.

This paper reports on the revision of the Curriculum Guidelines and Standards for Dental Laser Education. The original Guidelines were developed at a workshop at the University of California, San Francisco School of Dentistry in 1992, presented at the January 1993 SPIE symposium, and published in SPIE Proceedings Vol. 1880. They have since been endorsed and implemented worldwide. The Guidelines define the standard of education for practitioners who use lasers, with a goal to enhance of student and practitioner understanding and knowledge of laser technology applications in dentistry. Four levels of education are outlined. Introductory Courses are designed to provide general information on lasers in dentistry. They are informational, without an assessment of the student's proficiency in laser use. Standard Proficiency, Advanced Proficiency, and Educator Courses have specific educational goals, behavioral objectives, and examinations of proficiency. Standard Proficiency Courses prove a basic level of education with didactic, laboratory, and clinical exercises to be satisfactorily completed before using laser clinically. Advanced Proficiency Courses increase this level of education to include a clinical case study requirement. Educator Courses define requirements for instructors of laser education in dentistry. Revision of the Guidelines ensures that they keep pace with technological developments and research findings.

The aim of this study was to evaluate microleakage of composite restorations submitted to marginal treatment. Class V preparations with walls located in enamel were performed at buccal and lingual surfaces of eighteen recently extracted, non-carious human premolars. Cavities were restored with composite resins and adhesive system. Samples were stored in distilled water for 48h and polished with Sof-Lex discs. Teeth were randomly divide in six groups: G1 - Control; G2 - marginal treatment with surface sealant; G3 - Nd:YAG 25 Hz, 80mJ, 2W; G4 - Nd:YAG 20Hz, 100mJ, 2W; G5 - Nd:YAG 30Hz, 60mJ, 1.8W; G6 - Nd:YAG 30Hz, 40mJ, 1.2W. Contact fiberoptic (300μm) pulsed (1.064 μm) Nd:YAG laser was used for 30sec, under air cooling. Teeth were impermeabilized, immersed in a dye (Rhodamine B) for 4h at 37°, and sectioned. Specimens were evaluated under light microscopy and evaluated with scores. Results were analyzed with Kruskal- Wallis test (p=0.05) and showed that there were significant differences between marginal treatments; there were no significant differences beaten groups 1, 2, 4 and 3, 5, 6; lower values of microleakage were at groups 3, 5, 6. Nd:YAG laser showed marginal sealing ability and decreased microleakage of composite resins restorations.

The technology in dentistry has been developed significantly lately, increasing the technological level of new materials, methods and equipment have been developed. Undoubtedly the CO₂ laser has contributed to this evolution particular to the treatment of the infected dentin. CO₂ laser can sterilize and promote increase 6 to 8 times of dentin resistance, through the transformation the hydroxyapatite in calcium-phosphato-hydroxyapatite. We can reassure our patients about the use of pulsed CO₂ laser due to better preservation of dental structure and its benefits permitting advanced esthetic treatments. The CEREC system, registers a tri-dimensional image of the preparation through a scan system, and sends it to the computer and the operator will edit the restorations so the equipment will finish porcelain restoration. The authors used a new laser 650 nm for caries detection and the other low lever laser (670 nm and 730 nm) considered an auxiliary method to prevent and treat the hypersensitivity in dentin.

Dental caries (tooth decay) continues to be a major problems for adults as well as children, even though great advances have been made in preventive methods in the last 20 years. New methods for the management of caries will work best if lesions can be detected at an early stage and chemical rather than physical intervention can take place, thereby preserving the natural tooth structure and helping the saliva to heal, or remineralize, the areas of early decay. Clinical detection of caries in the US relies on visual examination, tactile with hand held explorer, and conventional radiographs, all of which are inadequate for the occlusal (biting) surfaces of the teeth where most of the decay now occurs. The dentist often has to explore by drilling with a dental bur to confirm early decay in these areas. New method that can determine the extent and degree of subsurface lesions in these surfaces non-destructively are essential for further advances in the clinical management of dental caries. Optical methods, which exploit the differences between sound and carious enamel and dentin, show great promise for the accurate detection of these lesions. Two or three- dimensional images, which include a measure of severity will be needed.

Today the diagnosis of caries is based mainly on examinations by visual inspection, dental probe or by x- rays. All methods are very limited when either initial or undermining caries have to be found. For initial caries promising results have been demonstrated by fluorescence spectroscopy with excitation wavelengths in the (ultra-)violet to green spectral region, especially 406 nm or 488 nm. In our investigations, we extended the considered excitation wavelength range into red. As expected, total fluorescence yield is decreasing with increasing wavelength, but this decrease is much more pronounced for sound compared to carious enamel or dentin. For 640 nm or 655 nm excitation for example, integral (λ>680nm) fluorescence intensity of cares can exceed that of healthy tissue by about one order of magnitude. This allows to detect caries by fluorescence intensity rather than by spectral analysis. On the basis of these results we have built up a system using a diode laser as light source, and a photo diode combined with a long pass filter as detector. It provides quantitatively reproducible measurements and detection even through sound enamel of 1 mm thickness. Clinical applications include detection of undermining caries and monitoring of the decay process.

The Quantitative Laser-Induced Fluorescence (QLF) technique has been sued for diagnosis of early caries in permanent teeth (PT). The objective of this study was to determine the caries quantification ability of QLF in deciduous teeth (DT). Sixty sound teeth, thirty DT and thirty PT, were used. All teeth were cleaned to remove debris and equally divided into three groups. Lesions were created in small windows (0.8x2.0 mm²) on buccal or labial surface for 48, 72, and 96 hr. Lesion images were made with a 488 nm argon laser (QLF I) and then with a 370 ± 80 nm violet-blue light (QLF II). Both images were analyzed to determine the mean percent change in fluorescence radiance (ΔF). A center section from the lesions was taken for analysis with microradiography. The lesion depth and loss of mineral content were determined. The correlations between ΔF and lesion depth as well as ΔZ in DT were 0.76 and 0.84 with QLF I, 0.81 and 0.88 with QLF II, respectively. It can be concluded the ability of QLF to quantify white-spots in DT is better than in PT.

A clinical investigation was conducted in children to validate the use of fluorescence for the early detection of dental caries. A total of 150 children were examined for the presence of dental caries at baseline and at 4-month intervals for one year using conventional visual-tactile with and without a dental explorer, electrical conductivity and light fluorescence methods on the occlusal, buccal and lingual tooth surfaces. Interproximal tooth surfaces were examined using conventional film and direct digital radiography at baseline and 12 months. Validation of the clinical methods was performed by the histologic examination of exfoliated primary teeth. The results indicate that visual-tactile examinations with an explorer detected more carious lesions than similar examinations without an explorer. The use of quantitative light fluorescence permitted the detection of a substantially greater number of enamel lesions or demineralized areas than the conventional visual-tactile-radiographic diagnostic procedure. Further, the use of the quantitative light fluorescence permitted the monitoring of both the progression of regression of early carious lesions.

Thermal effects caused by 532 nm Nd:YAG laser pulses on human tooth surface are investigated using an IR high frame rate (60 Hz) detector (256x 256 elements, Indium Antimonide, with 3-5 μm spectral bandwidth). Measurements of the temperature on a reference line of the tooth surface during exposure to laser pulses of 0.5 W of power, with time amplitude of 12 ns and 10 Hz of frequency repetition are performed. Images and maps of temperature of the human to the surface are shown during laser treatment. Results are discussed with particular reference to the possibility to evaluate thermal effects of pulsed lasers of frequent use in dentistry and to the application of such lasers as excitation sources for non- destructive defect analysis of human teeth by laser Doppler vibrometry.

Partial coherence interferometry (PCI) and optical coherence tomography (OCT) are noninvasive and noncontact techniques for high precision biometry and for obtaining cross- sectional images of biologic structures. OCT was initially introduced to depict the transparent tissue of the eye. It is based on interferometry employing the partial coherence properties of a light source with high spatial coherence ut short coherence length to image structures with a resolution of the order of a few microns. Recently this technique has been modified for cross section al imaging of dental and periodontal tissues. In vitro and in vivo OCT images have been recorded, which distinguish enamel, cemento and dentin structures and provide detailed structural information on clinical abnormalities. In contrast to convention OCT, where the magnitude of backscattered light as a function of depth is imaged, polarization sensitive OCT uses backscattered light to image the magnitude of the birefringence in the sample as a function of depth. First polarization sensitive OCT recordings show, that changes in the mineralization status of enamel or dentin caused by caries or non-caries lesions can result in changes of the polarization state of the light backscattered by dental material. Therefore polarization sensitive OCT might provide a new diagnostic imaging modality in clinical and research dentistry.

There is no diagnostic technology presently available utilizing non-ionizing radiation that can image the state of demineralization of dental enamel in vivo for the detection, characterization and monitoring of early, incipient caries lesions. In this study, a Polarization Sensitive Optical Coherence Tomography (PS-OCT) system was evaluated for its potential for the non-invasive diagnosis of early carious lesions. We demonstrated clear discrimination in PS-OCT imags between regions of normal and demineralized enamel in bovine enamel blocks containing well-characterized artificial lesions. Moreover, high-resolution, cross- sectional images were acquired that clearly discriminate between the normal and carious regions of extracted human teeth. Regions that appeared to be demineralized in the PS- OCT imags were verified using histological thin sections examined under polarized light. The PS-OCT system discriminates between normal and carious regions by measuring the state of polarization of the back-scattered 1310 nm light, which is affected by the state of demineralization of the enamel. The demineralized regions of enamel have a large scattering coefficient, thus depolarizing the incident light. This initial study shows that PS-OCT has great potential for the detection, characterization, and monitoring of incipient caries lesions.

Derivation and predictions of the basic analytical model of thermo-mechanical laser ablation, treating the limit case of constant laser intensity, 1D geometry, negligible heat diffusion and no debris screening, is summarized first as a reference point for further discussion. Each of the above requirements is then omitted in turn, to analyze additional effects observed under various experimental conditions. Scattering and absorption of the laser radiation in ejected debris is treated using a model that allows the debris extinction coefficient to vary dynamically during the ablation process, resulting in influence of pulse duration on the fluence dependence of predicted ablation crater depths. Next, the influence of heat diffusion on ablation efficiency and amount of thermal side effects is analyzed in a semi-quantitative way, leading to rule-of-thumb formulas that predict the ablation regime for a general ablation process from laser pulse fluence and duration as well as optical and thermal properties of the treated tissue. Influence of the laser beam profile on ablation crater depth and shape is demonstrated and discussed for the case of Gaussian beam profile. In the end, fiber-tip contact ablation in the presence of water spray is discussed as a counter-example of experimentally observed effects that - to our best knowledge - are still beyond the reach of quantitative understanding.

Pulsed CO₂ lasers have been shown to be effective for both removal and modification of dental hard tissue for the treatment of dental caries. In this study, sealed TEA laser systems optimally tuned to the highly absorbed 9.6 μm wavelength were investigated for application on dental hard tissue. Conventional TEA lasers produce a laser pulse wit a 100-200 ns gain switched spike followed by a long tail of about 1-4 μs in duration. the pulse duration is well matched to the 1-2 μs thermal relaxation time of the deposited laser energy at 9.6 μm and effectively heats the enamel to temperatures required for surface modification for caries prevention at absorbed fluences of less than 0.5 J/cm². Thus, the heat deposition in the tooth and the corresponding risk, of pulpal necrosis form excessive heat accumulation is minimized. At higher fluences the high peak power of the gain-switched spike rapidly initiates a plasma that markedly reduces the ablation rate and efficiency, severely limiting applicability for hard tissue ablation. By slightly stretching the pulse to reduce the energy distributed in the initial 100-200 ns of the laser pulse, the plasma threshold can be raised sufficiently to increase the ablation rate by an order of magnitude. This results in a practical and efficient CO₂ laser system for caries ablation and surface modification.

Previous studies have shown that IR irradiation of dental enamel at specific wavelengths results in chemical changes in the mineral phase that reduce the progression of sub- surface caries-like lesions. The inhibition of lesion progression has been correlated to the decomposition of carbonate in the irradiated enamel mineral. The present study investigated loss of the carbonate component as a function of depth with 1 micrometers resolution by measuring the strength of the spectrum in the region of the carbonate absorption bands near 1400 cm^-1. Bovine enamel samples were laser treated at λ=9.6 μm with a pulse duration of either 2 μs or 100 μs and at λ=10.6 μm with a pluse duration of 2 μs. The depth of treatment was compared with numerical simulation of the temperature rise in enamel due to laser heating. The temperature rise needed to initiate carbonate loss was 400° C, but complete carbonate loss did not occur until surface temperatures were reached which exceeded the melting temperature (800-1200 °C). The depth of the treatment varied depending upon the absorption coefficient, pulse duration, and fluence of the laser irradiation.

The differences between a contact and non-contact Er:YAG laser hard dental tissue preparation were verified. The influence of laser energy and number of pulses on a profile and depth of a drilled cavity was investigated. The delivery systems used were an articulated arm and a cyclic olefin polymer-coated silver hollow glass waveguide with or without a special sapphire tip. In the case of the non-contact preparation, the laser radiation was directed onto the dental tissue by focusing optics (CaF₂ lens) together with the cooling water spray in order to ensure that the tissues will not be burned. The water spray was also used during the preparation when the waveguide with a sapphire tip was used to deliver the radiation. For the evaluation of shapes, depth and profiles of the prepared cavities the metallographic microscope, photographs from the light microscope and scanning electron microsec were used. From the result it follows that great differences exist in the laser speed, value of energy, the profile, and depth of the cavities prepared by the contact and non-contact preparation. In the case of contact ablation the procedure is quicker, the energy fluence needed is lower and more precise cavities with larger diameters are produced.

This study compared the effects of a new CO₂ laser device on the enamel surface of deciduous teeth in the continuous and superpulsed mode. Literature presents works on superpulsed CO₂ laser specially on bone tissue and only tow studies on permanent teeth. Deciduous exfoliated noncarious human canine teeth were used from the teeth collection of the Dentistry College of the University of Sao Paulo. The results showed specific changes on the surface of human deciduous teeth enamel after application of CO₂ laser and CO₂ laser superpulsed.

Enamel surface morphologic alterations were investigated when an Er:YAG focused moistened laser radiation (λ =2.94μm) was applied on canine deciduous teeth enamel. The results were compared to the data already reported concerning permanent dental enamel. The results indicated that the ultrastructural effects obtained were very alike to permanent enamel literature reports.

Previous studies have shown that irradiation of dental enamel by carbon dioxide (CO₂) laser irradiation, with and without fluoride, can inhibit the acid-induced surface dissolution of the carbonated apatite (CAP) mineral of the tooth. The aim of the present study was to test the hypothesis that laser treatment together with fluoride (F) can effectively transform the CAP in caries-like lesions to fluorapatite (FAP), which is orders of magnitude less soluble than CAP. Samples of both sound and caries-like enamel were irradiated by CO₂ laser at 9.6 μm , 25 pulses per spot, 2 μs pulse duration and 1J/cm² fluence, with and without F treatment. The surface acid-dissolution rate was measured, together with untreated controls in a specially constructed apparatus. FAP formation was assessed by chemical analysis. Results showed dissolution rate reductions of 49%, 73%, and 87% for fluoride treatment, laser alone, and the laser/F combination respectively. Carbonate loss (measured by FTIR) coincided with dissolution rate reduction. High F concentrations were incorporated into the laser treated samples, producing marked dissolution rate reductions, most likely related to the formation of FAP.