This PDF file contains the front matter associated with SPIE Proceedings Volume 6425, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Dental caries is a disease in which minerals of the tooth are dissolved by surrounding bacterial plaques. A caries process present for some time may result in a caries lesion. However, if it is detected early enough, the dentist and dental professionals can implement measures to reverse and control caries. Several optical, nonionized methods have been investigated and used to detect dental caries in early stages. However, there is not a method that can singly detect the caries process with both high sensitivity and high specificity. In this paper, we present a multimodal imaging system that combines visible reflectance, fluorescence, and Optical Coherence Tomography (OCT) imaging. This imaging system is designed to obtain one or more two-dimensional images of the tooth (reflectance and fluorescence images) and a three-dimensional OCT image providing depth and size information of the caries. The combination of two- and three-dimensional images of the tooth has the potential for highly sensitive and specific detection of dental caries.

Detailed morphological and cellular information relating to the human tooth have traditionally been obtained through histological studies that required decalcification, staining, and fixation. With the recent invention of multiphoton microscopy, it has become possible to acquire high resolution images without histological procedures. Using an epiilluminated multiphoton microscope, we obtained two-photon excited autofluorescence and second harmonic generation (SHG) images of ex vivo human tooth. By combining these two imaging modalities we obtained submicron resolution images of the enamel, dentin, and the periodontal ligaments. The enamel emits endogenous two-photon autofluorescence. The structure of the dentin is visible from both the autofluorescence and second harmonic generation signals. The periodontal ligament composed mostly of collagen can be visualized by SHG imaging. We also constructed three dimensional images of the enamel, dentin, and periodontal ligament. The effectiveness of using multiphoton and second harmonic generation microscopy to obtain structural information of teeth suggest its potential use in dental diagnostics.

Failure of endodontic treatment is commonly due to Enterococcal infection. In this study influence of chemical treatments of type-I collagen membrane by chemical agents commonly used in endodontic treatment on Enterococcus faecalis cell adherence was evaluated. In order to determine the change in number of adhering bacteria after chemical treatment, confocal laser scanning microscopy was used. For this, overnight culture of E faecalis in All Culture broth was applied to chemically treated type-I collagen membrane. It was found that Ca(OH)₂ treated groups had statistically significant (p value=0.05) increase in population of bacteria adherence. The change in adhesion force between bacteria and collagen was determined by using optical tweezers (1064 nm). For this experiment, Type-I collagen membrane was soaked for 5 mins in a media that contained 50% all culture media and 50% saturated Ca(OH)₂ . The membrane was spread on the coverslip, on which diluted bacterial suspension was added. The force of laser tweezers on the bacteria was estimated at different trap power levels using viscous drag method and trapping stiffness was calculated using Equipartition theorem method. Presence of Ca(OH)₂ was found to increase the cell-substrate adherence force from 0.38pN to >2.1pN. Together, these experiments show that it was highly probable that the increase in adherence to collagen was due to a stronger adhesion in the presence of Ca (OH)₂.

We have been developing a unique optical frequency domain reflectometry (OFDR)-OCT based on Mach-Zehnder interferometer using a discretly swept superstructure-grating distributed Bragg- reflector (SSG-DBR) lasers developed for telecommunication field. Our previous measurements at C-band wavelength (1529 to 1568 nm) revealed good quality of data. In this work, we extend measurements with a L-band (1560 to 1600 nm) SSG-DBR source at faster scanning speed of 0.5 &mgr;s/step compared with former 10 &mgr;s/step. In spite of the faster scanning, we can observe better quality of OCT images of hard and soft dental tissues in-vitro and in-vivo measurements.

In this work a technique was proposed and evaluated for detection of metallic posts of parallel sides through a test body of Z100 dental resin. The technique presented involves the acquisition and the image processing by trans-illumination of the resin to detect the edges of the posts. LASER and LED systems in different colors were used as a source of irradiation for the image formation. The qualitative analysis of the results showed that just by using LED in the red and green colors it was possible to detect the edges of the posts. The results also showed that the use of LASER in this experiment was not successful mainly due to the LASER light optical interference phenomenon inside the resin, which resulted in low definition images. Lastly the discussion of the work was directed to the optical effects of absorption and scattering of light throughout the resin, light diffraction through the posts and interference of the coherent light evaluating the influence of each effect in the experiment.

We applied two new spectroscopic techniques (time-gated Raman microscopy and excitation-emission fluorescence microspectroscopy) to characterize healthy and carious dental tissues. These methods were used together with visual inspection, DIAGNOdent, optical polarization microscopy, scanning electron microscopy, and chemical microanalysis to get a more detailed picture of chemical and structural transformations in dental tissues as a result of caries development.

A new multi-wavelength optical-plethysmograph has been designed to study the relation between the transmitted optical density (OD) of the tooth vs. hemoglobin (Hb) content and oxygen saturation (SO₂) of the pulpal blood using the 467, 506, 522 and 810 nm light emitting diodes (LEDs). The experimental model utilized the extracted human upper incisor where the pulp cavity was filled with the blood having various values of Hb and SO₂. A resin cap was made to fit the tooth crown and optical fibers for transmission measurement. The LEDs were pulsed sequentially at 520 Hz with the pulse duration of 240 μs. The OD as a function of Hb for the isosbestic wavelengths of 506 and 522 nm increased almost linearly from 8.0 to 11.0 for Hb changing from 0.0 (saline control) to 2.5 g/dL, but beyond 2.5 g/dL no change was observed. At 810 nm, the OD increased linearly till Hb of 13.4 g/dL, but its change was much smaller with 1.0 OD per 13.4 g/dL. As for SO₂, the OD at 467 nm with Hb of 1.0 g/dL that simulated the mean pulpal Hb content in vivo varied by about 1.0 for SO₂ changing from 100 to 40%. The OD change with respect to Hb change at 506 and 522 nm showed better sensitivity than that at 810 nm. The combination of 467 and 506 or 522 nm wavelengths can provide a noninvasive measurement of both pulpal Hb content and SO₂ to diagnose pulp vitality of teeth in vivo.

Fiber-reinforced composites are new materials which have been used for a variety of dental applications, including tooth splinting, replacement of missing teeth, treatment of dental emergencies, reinforcement of resin provisional fixed prosthodontic restorations, orthodontic retention, and other clinical applications. Different fiber types are available, but little clinical information has been disseminated. The traditional microscopy investigation, most commonly used to study this material, is a destructive technique, which requires specimen sectioning and are essentially surface measurements. On the basis of these considerations, the aim of this research is to analyze the interior of a dental sample reinforced with fiber after a mechanical and thermal cycling to emulate oral conditions using optical coherence tomography (OCT). The device we are using is a home built Fourier domain OCT working at 800 nm with 6 &mgr;m resolution. The results are compared with microscopy images to validate OCT as a working method. In long term, fractures allow bacterial invasion provoking plaque and calculus formation that can cause caries and periodontal disease. Therefore, non invasive imaging of the bridge fiber enables the possibility of periodic clinical evaluation to ensure the patient health. Furthermore, OCT images can provide a powerful method for quantitative analysis of crack propagation, and can potentially be used for in vivo assessment.

This work presents a study to understand the interaction between Er:YAG laser and composite resin. The main purpose is the development of a new ultra-conservative clinical technique: differential ablation for composite resin restorations using Er:YAG laser. A hybrid composite resin (Z100, 3M, USA) formatted as tablets recently cured was used and after artificial aging method the teeth were irradiated with a Er:YAG laser and two different conditions were considered, energy level per pulse (100, 300 and 500mJ), frequencies (5, 10 and 15Hz) and different water fluxes. Diameter and depth of each resulted microcavity was measured and the material removed volumes were calculated. The resulted values were plotted and feted to allow a comparative observation of the material removed as a function of energy level per pulse. Frequencies of 5 and 10Hz were similar between them and seemed to allow the highest material ablated volume, however considering the energy per pulse parameter, 300mJ was more efficient than the others, mainly when water flux was around 0.1ml/s. The highest water flux showed lower ablation rate with the lowest fluency. Water fluxes presented an important factor considering composite ablation, even because it could modulate depth and surface regularity of the irradiated material.

The violet diode laser (405nm) has recently begun to be studied for surgical use and authors reported the soft tissue could be effectively incised by irradiation power of even less than 1W. The wavelength of this laser is highly absorbed by hemoglobin, myoglobin or melanin pigment. Cutting or ablating soft tissues by lower irradiation power might be preferable for wound healing. The CO₂ laser is known to be preferable for low invasive treatment of soft tissues and widely used. The CO₂ laser light (10.6μm) is highly absorbed by water and proper for effective ablation of soft tissues. In this paper, we report the comparison of the violet diode laser with the CO₂ laser in surgical performance of soft tissues. Tuna tissue was used as an experimental sample. In the case of the violet diode laser, extensive vaporization of tissue was observed after the expansion of coagulation. Carbonization of tissue was observed after the explosion. On the other hand, consecutive vaporization and carbonization were observed immediately after irradiation in the case of CO₂ laser. The violet diode laser could ablate tissue equivalently with the CO₂ laser and coagulate larger area than the CO₂ laser. Therefore the violet diode laser might be expectable as a surgical tool which has excellent hemostatis.

Free running and Q-switch infrared Er:YAG laser radiations were compared in the case of hard tissue preparation. The interaction energy of 40 mJ in pulse 200 us long yielding to the interaction intensity 62 kW/cm², and the energy of 20 mJ in 100 ns long pulse yielding to the interaction intensity 62 MW/cm² was used for the case of free running, and Q-switch regime, respectively. For the radiation delivery, waveguide transfer system was used. It consisted of input lens (40 mm focal length), a cyclic olefin polymer coated silver hollow glass waveguide (700/850 um diameter), and output lens (55 um focal length). For the interaction experiment the samples of the extracted human teeth cut into longitudinal sections and polished were used. The thickness of the prepared samples ranged from 5 to 7 mm. The methods were compared from the point of prepared cavity shape (SEM), inner surface, and possibility of selective removal of carries. The composite filling material was used to reconstruct the cavities.

Laser treatment is a promising technique for dental applications such as caries removal, dental hypersensitivity reduction and improvement of the bond strength between dentin and restoration materials. In this study the topographic and morphological changes induced in enamel and dentin surfaces by treating with KrF excimer laser radiation were studied as a function of the number of laser pulses and radiation fluence by scanning electron microscopy and optical profilometry. For enamel, independently of the fluence used, material removal occurs preferentially at the prisms sheaths, leading to the formation of surface pits of a few micrometers. For dentin, a cone-like topography develops when the tubules are approximately parallel to the laser beam direction and the radiation fluence is within the range 0.5 to 1.5 J/cm². For higher fluences, the treated surfaces are flat and covered with a layer of re-solidified materials.

We have shown that the enamel of the tooth is almost completely transparent near 1310-nm in the near-infrared and that near-IR (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue and for observing defects in the interior of the tooth. Lasers are now routinely used for many applications in dentistry including the ablation of dental caries. The objective of this study was to test the hypothesis that real-time NIR imaging can be used to monitor laser-ablation under varying conditions to assess peripheral thermal and transient-stress induced damage and to measure the rate and efficiency of ablation. Moreover, NIR imaging may have considerable potential for monitoring the removal of demineralized areas of the tooth during cavity preparations. Sound human tooth sections of approximately 3-mm thickness were irradiated by a CO₂ laser under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with band-pass filter centered at 131--nm combined with an InGaAs focal plane array with a NIR zoom microscope in transillumination. Due to the high transparency of enamel at 1310-nm, laser-incisions were clearly visible to the dentin-enamel junction and crack formation, dehydration and irreversible thermal changes were observed during ablation. This study showed that there is great potential for near-IR imaging to monitor laser-ablation events in real-time to: assess safe laser operating parameters by imaging thermal and stress-induced damage, elaborate the mechanisms involved in ablation such as dehydration, and monitor the removal of demineralized enamel.

It has been previously demonstrated that short &lgr;=355-nm laser pulses can be used for the selective removal of caries lesions and composite restorative materials from occlusal surfaces with minimal damage to the peripheral sound tooth structure. One advantage of laser-systems is they can be integrated with acoustic and optical feedback systems for the automated discrimination of dental caries and restorative materials. The objective of this study was to test the hypothesis that root caries could be selectively removed from tooth surfaces using a computer controlled laserscanning system coupled with an acoustic feedback system. Dental root caries surfaces on extracted teeth were scanned with &lgr;=355-nm laser pulses at irradiation intensities ranging from 0.6 to 0.8 J/cm². Acoustic feedback signals were acquired and used to control the laser output and scanning stages were used to position the laser over carious dentin until all the caries were removed to a fixed depth. Polarization optical coherence tomography (PSOCT) was used to acquire images of the root caries lesions before and after removal by the laser in order to assess if ablation was selective. The amplitude of the acoustic waves generated during the ablation of carious dentin was higher than for sound dentin allowing the acoustic feedback system to discriminate between sound and carious dentin. PS-OCT showed that caries were removed to a depth of up to 1.5-mm with minimal peripheral damage to peripheral sound dentin. The acoustic feedback was successfully used to distinguish between root caries and sound dentin, enabling the selective removal of caries from dentin surfaces using a &lgr;=355-nm, Nd:YAG Q-switched laser system.

Samples of bone, dentin and enamel were stored in distilled water, 10% neutral buffered formalin, 70% ethyl alcohol or 6% sodium hypochlorite solutions for fifteen days. Other samples were stored in the same solutions for 36 hours and then transferred to distilled water for the remainder of the fifteen day period. Finally, samples than had been stored dry for up to 5 years were rehydrated and ablated. All enamel specimens appeared unaffected by the storage conditions. Dentin samples were very significantly affected by all storage methods. Bone samples were affected by most storage conditions. Samples stored in sodium hypochlorite had as much as a 100 percent increase in ablation rate. Surprisingly, dry stored samples that were reconstituted for 36 hours ablated at virtually the same rate as those stored in distilled water. None of the storage conditions studied produced ablation rates that mirrored in vivo ablation. Sterilization by autoclave is the only reliable and safe method studied but cannot be used on teeth with amalgam fillings for safety reasons. Teeth with fillings should be stored in 10% neutral bufferred formalin for a minimum of one week.

Ultrashort-pulsed laser (USPL) can ablate various materials with precious less thermal effect. In laser dentistry, to solve the problem that were the generation of crack and carbonized layer by irradiating with conventional laser such as Er:YAG and CO₂ laser, USPL has been studied to ablate dental hard tissues by several researchers. We investigated the effectiveness of ablation on dental hard tissues by USPL. In this study, Ti:sapphire laser as USPL was used. The laser parameter had the pulse duration of 130 fsec, 800nm wavelength, 1KHz of repetition rate and the average power density of 90~360W/cm². Bovine root dentin plates and crown enamel plates were irradiated with USPL at 1mm/sec using moving stage. The irradiated samples were analyzed by SEM, EDX, FTIR and roughness meter. In all irradiated samples, the cavity margin and wall were sharp and steep, extremely. In irradiated dentin samples, the surface showed the opened dentin tubules and no smear layer. The Ca/P ratio by EDX measurement and the optical spectrum by FTIR measurement had no change on comparison irradiated samples and non-irradiated samples. These results confirmed that USPL could ablate dental hard tissue, precisely and non-thermally. In addition, the ablation depths of samples were 10&mgr;m, 20&mgr;m, and 60&mgr;m at 90 W/cm², 180 W/cm², and 360 W/cm², approximately. Therefore, ablation depth by USPL depends on the average power density. USPL has the possibility that can control the precision and non-thermal ablation with depth direction by adjusting the irradiated average power density.

In this study, we investigated the role of water spray. To ablate human enamel tissue, a long-pulsed Er,Cr:YSGG laser was used at various radiant exposures. During dental ablation, distilled water was sprayed to the sample surface. Desiccated samples were also tested with direct irradiation for comparison. In order to identify dominant ablation mechanisms, transient acoustic waves were measured using a piezoelectric microphone. Enamel ablation efficiency was evaluated with Optical Coherence Tomography (OCT). Material removal was up to four times larger at the best flow rate with respect to ablation without spray. In spite of 60 % higher damage threshold by water absorption, spray ablation enhanced both the laser-induced acoustic transients up to six times and the ablation efficiency up to twice over the entire range of radiant exposures tested, compared to dry ablation. The improved pressure and ablation performance of the spray-assisted process with cooling effect were thought to be induced by recoil stress, rapid water vaporization, interstitial water explosion, and/or liquid-jet formation. Spray ablation along with water cooling and abrasive mechanical effects can be a safe and efficient modality for dental treatment.

The present study aimed to compare root caries removal by air turbine and Er,Cr:YSGG laser, and examine morphological changes after these caries removal techniques under scanning electron microscopy (SEM). Seventy two extracted human carious-free third molars were used in this study. After the in vitro root caries induction using S. mutans, the carious lesions were removed by the conventional technique, using burs (control), and by the Er,Cr:YSGG laser, using 13 different parameters, between 1 and 4,0 W. During caries removal, preparation time was recorded for all groups. The results appointed out that the conventional method was the fastest one. When only laser treatment was evaluated, the higher parameters seemed to remove caries faster then the lower ones. SEM revealed that the surfaces treated by air turbine were smooth, but with debris. The laser groups demonstrated smooth undulations, with little or absence of smear layer, and no signs of carbonization. These results suggest that caries removal by Er,Cr:YSGG laser was effective. Therefore, this equipment requires training on cavity preparation, in order to avoid damages in dental hard tissues.

Laser systems of various wavelengths and pulse characteristics have been introduced in dentistry. At present, the range of applications for the different systems is being investigated mainly differentiating between soft and hard tissue applications. For the preparation of root canals both hard and soft tissues are involved. Ideally, one would like to use one laser system for the whole treatment. In this study, we studied the characteristics of the pulsed 2,78 Er,Cr:YSGG laser (Biolase, Waterlase Millenium), in view of root canal cleaning and desinfection. The laser energy was fiber delivered with fiber tip diameters from 400 &mgr;m down to 200 &mgr;m. Special thermal and high speed imaging techniques were applied in a transparent model of a tapered root canal and slices cut from human teeth. High speed imaging revealed the dynamics of an explosive vapor bubble at the tip of the Er laser in water and the root canal model. Typically for Erbium lasers, within a time span of several hundred &mgr;s, a longitudinal bubble expanded to maximum size of 5 mm length and 2 mm diameter at 100 mJ and imploded afterwards. In the root canal, the explosive bubble created turbulent high speed water streaming which resects soft tissue from the hard tissue. Thermal imaging showed the dynamics of all lasers heating of the canal wall up to several mm depending on the wavelength and energy settings. The mechanism of smear layer removal and sterilization in the root canal, is attributed to cavitation effects induced by the pulsed laser. The heat generation into the dentine wall was minimal.

Studies in cariology have been struggling for the development of caries prevention techniques, precocious diagnoses of lesions, re-mineralization of incipient carious lesions and early restorative intervention with minimally invasive procedures. When removing caries, healthy dental structure is often removed inadvertently during its final phase, for being quite difficult to precise the limits between viable and decayed dental tissues clinically. With laser technologies, a subjective clinical hint, often used to indicate when tissue ablation should be stopped is that different sounds are perceptive whether in carious (bass) or in healthy (treble) dental structure; when sound produced by ablation turned treble it would mean that healthy tissue was reached. This study aims to classify those audio differences and to turn them into objective parameters for a conservative operative dentistry with minimally invasive tissue removal when using erbium lasers. Twenty freshly extracted human teeth were used (10 decayed and 10 sound teeth). Dentine was erbium laser irradiated under same parameters, distance and refrigeration and a mono directional microphone was set 10 cm far from the operative area in order to capture and record the ablation produced sounds when working either on carious or healthy dentine. Ten pulses per file were then analysed in a computer software (200 analyses). It was permitted to draw similarities among the patterns in each group (decayed and healthy teeth) as well as differences between decayed and healthy produced sounds. Audio analysis came out to be a technical reliable objective parameter to determine whether laser ablated dentine substrates are decayed or sound; therefore it can be proposed as a conservative parameter, avoiding unnecessary removal of healthy dentine and restricting it to carious one.

This study evaluated the molecular and morphological changes on dentin elements after the Er:YAG laser irradiation. Six human third molars were selected and the occlusal one-third of the crown was removed. The dentin surface was schematically divided into areas corresponding to four surface treatments groups: Control (Group C): 37% phosphoric acid etching; Group I: Er:YAG laser 80mJ; Group II: Er:YAG laser 120mJ; Group III: Er:YAG laser 180mJ. The characterization was performed by Scanning Electron Microscopy (SEM) and Fourier-Transformed Raman Spectroscopy (FT-Raman) before and after the treatments. A reduction of the relative intensity for the spectra was observed in the Group II and III samples. The SEM photomicrographies revealed open dentin tubules in the control group specimens. The groups I, II and III presented partially open dentin tubules. SEM images showed that the laser-irradiated dentin surface was not favorable to the diffusion of monomers. The chemical information obtained by Raman spectroscopy showed that higher laser energies (180 mJ) affected more the phosphate, carbonate and the organic components of dentin.

Polarization sensitive optical coherence tomography (PS-OCT) and near-IR (NIR) imaging are promising new technologies under development for monitoring early carious lesions. Fluorosis is a growing problem in the U.S., and the more prevalent mild fluorosis can be visually mistaken for early enamel demineralization. Some initial NIR images suggest that enamel defects and dental caries manifest different optical behavior in the NIR. Unfortunately, there is little quantitative information available regarding the differences in optical properties of sound enamel, enamel developmental defects, and demineralized enamel due to caries. This study tested the hypothesis that hypomineralized enamel due to fluorosis can be differentiated from demineralized enamel due to caries using NIR and PS-OCT imaging because of different optical behavior in the NIR. Thirty extracted human teeth with various degrees of suspected fluorosis and/or caries were imaged using PS-OCT and NIR transillumination. An InGaAs camera and a near-IR diode laser were used to measure the optical attenuation through transverse tooth sections (~200 &mgr;m). Developmental defects were clearly visible in the polarization-resolved OCT images, demonstrating that PS-OCT can be used to nondestructively measure the depth and possible severity of the defects. Enamel defects on whole teeth that could be imaged with high contrast with visible light were transparent in the near-IR while demineralized areas due to caries were opaque. In contrast, dental caries could be clearly distinguished from sound enamel. This study suggests that PS-OCT and NIR methods may potentially be used as tools to assess the severity and extent of enamel defects and for the differentiation of mild fluorosis defects from early carious lesions.

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. The objective of this study was to test the hypothesis that two-dimensional NIR images of demineralized tooth surfaces can be used to guide CO₂ laser ablation for the selective removal of artificial caries lesions. Highly patterned artificial lesions were produced by submerging 5 x 5 mm² bovine enamel samples in demineralized solution for a 9-day period while sound areas were protected with acid resistant varnish. NIR imaging and polarization sensitive optical coherence tomography (PS-OCT) were used to acquire depth-resolved images at a wavelength of 1310-nm. An imaging processing module was developed to analyze the NIR images and to generate optical maps. The optical maps were used to control a CO₂ laser for the selective removal of the lesions at a uniform depth. This experiment showed that the patterned artificial lesions were removed selectively using the optical maps with minimal damage to sound enamel areas. Post-ablation NIR and PS-OCT imaging confirmed that demineralized areas were removed while sound enamel was conserved. This study successfully demonstrated that near-IR imaging can be integrated with a CO₂ laser ablation system for the selective removal of dental caries.

Previous studies have demonstrated that Polarization Sensitive Optical Coherence Tomography (PS-OCT) can be used to image early dental caries. The purpose of this study was to compare the measured integrated reflectivity of natural caries lesions with the mineral loss measured using digital microradiography in order to determine if PS-OCT can be used as a nondestructive in vivo method to measure the severity of dental decay in the important occlusal surfaces. A PS-OCT system operating at 1310-nm was used to acquire polarization resolved images of natural caries lesions on the occlusal surfaces of extracted teeth. The integrated reflectivity from lesion areas was compared to the integrated mineral loss from the same lesion area measured using digital microradiography. There was a strong correlation between the integrated mineral loss of the caries lesion measured using high resolution digital microradiography and the integrated reflectivity in the perpendicular polarization axis of the PS-OCT system demonstrating the potential for this method to nondestructively monitor the severity of caries lesion in the occlusal pit and fissure where most new decay is found. Although we find these results encouraging, we desire a higher correlation between the integrated mineral loss and the integrated reflectivity and we believe a higher correlation is attainable with better matching of the PS-OCT scans and the histological thin sections.

Pemphigus vulgaris is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. In this case micro-Raman spectroscopy (&mgr;-RS) can provide a powerful tool for a not invasive analysis of biological tissue for biopsy and in vivo investigation. Based on the evaluation of molecular vibration frequencies, the &mgr;-RS is able to detect the main molecular bonds of protein constituents, as the C-H and C-C ones. Changes in frequency or in the relative intensity of the vibration modes revealed by &mgr;-RS can be related to changes of chemical bond and of protein structure induced by pathology. Quantitative information on the intensity variation of specific Raman lines can be extracted by Partial Least Square (PLS) analysis. &mgr;-RS was performed on some samples of oral tissue and blood serum from informed patients affected by pemphigus vulgaris (an oral pathology) at different pathology stages. The spectra were measured by means of a Raman confocal microspectrometer apparatus using the 633 nm line of a He- Ne laser source. The main protein bonds are clearly detectable in the considered samples giving important information on the integrity and on the state of tissue and blood serum components (lipids and proteins), and consequently on the occurrence of pathology.

This study evaluated ex vivo the influence of the number of gel/LED-laser applications/activations on cervical microleakage of two different barrier materials used for protection during whitening of endodontically treated teeth. Eighty-four canines were instrumented and obturated with epoxy resin sealer. The seal was removed 2 mm beyond the cemento-enamel junction for barrier placement and the teeth were divided into two groups of 40 teeth each: G1, zinc phosphate cement; G2, glass ionomer cement. The two groups were subdivided into 4 subgroups (n=10 each): I) no gel or LED-laser application; II) one gel application and two LED-laser activations; III) two gel applications and four LED-laser activations; IV) three gel applications and six LED-laser activations. The teeth were immersed in India ink for 7 days, decalcified and cleared. Cervical microleakage was quantified with a measurement microscope. Statistical analysis showed that zinc phosphate caused significantly lower microleakage than glass ionomer cement (presented microleakage in all subgroups). However, after two (p<0.01) and three (p<0.001) applications of gel, there was statistially significant microleakage in zinc phosphate barriers. Based on the present results, it can be concluded that cervical barriers with zinc phosphate cement show less cervical microleakage and that two or more applications/activations of gel/LED-laser significantly increase microleakage.

The dental bleaching is known for many years. Recently a technique employing light has open up new and exciting possibilities. Besides its vast application there are still many important points to be understood about teeth photon bleaching. In this work we present an "in vitro" experiment to explore the main mechanisms involved during the photon action in tooth whitening. Our results indicated that light at same wavelengths are great absorbed by pigments creating a local heating which considerably increase the bleaching rate. This results in a fast reaction without heating the whole dental structure. We discuss details of our experiment. Work supported by Fapesp and CNPq.

Selection of the proper shade and color matching of restorations to natural dentition continues to be one of the most frustrating problems in dentistry and currently available shade guide presents a limited selection of colors compared to those found in natural dentition. This investigation evaluation if the composites resins shade B2 are equivalent to the Vita shade guide B2. Twelve composite resins (Renamel Microfill Super Brite- Cosmedent USA, Renamel Universal Brite- Cosmedent USA, Renamel Microfill Body- Cosmedent USA, Renamel Universal Body- Cosmedent USA, Opallis EB2-FGM, Opallis DB2-FGM, Filtek Supreme XT-3M/ESPE, Filtek Z250-3M/ESPE, Filtek Z350-3M/ESPE, Z100-3M/ESPE, 4 Seasons Dentin-Ivoclar/Vivadent, Tetric Ceram-Ivoclar/Vivadent) shade B2 were used. From each composite, two specimens were made in a steel matrix with 8.0 mm diameter and 10.0 mm different predetermined thickness (0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 mm). The specimens were 40 seconds light polymerized by LED Ultrablue (DMC). The specimens were measured 10 times each to determine the shade using a reflectance spectrophotometer (Pocket Spec). According to results was verified that not any of composites resins shade B2 evaluated in this study presented values of color difference (ΔE) equivalent to the Vita shade guide B2 and the 2 mm thickness showed the closer match to the Vita shade guide B2.

A major characteristic of LEDs systems is the lower heat emission related with the kind of light generation and spectral emission band. Material temperature during photoactivation can promote different photocuring performance. Organic dye penetration could be a trace to identify the efficacy of photocured composite resin. A new method using fluorescent spectroscopy through digital image evaluation was developed in this study. In order to understand if there is a real influence of material temperature during the photoactivation procedure of a dental restorative material, a hybrid composite resin (Z250, 3M-Espe, USA) and 3 light sources, halogen lamp (510 mW/cm²) and two LED systems 470±10nm (345 and 1000 mW/cm²) under different temperatures and intensities were used. One thousand and five hundred samples under different associations between light sources and temperatures (0, 25, 50, 75 and 100^oC were tested and immediately kept in 6G rodamin dye solution. Dye penetration was evaluated through fluorescent spectroscopy recorded by digital image data. Pixels in gray scale showed the percentage penetration of organic dye into the composite resin mass. Time and temperature were statistically significant (p<0.05) through the ANOVA statistical test. The lowest penetration value was with 60 seconds and 25^oC. Time and temperature are important factors to promote a homogeneous structure polymerized composite resin more than the light source type, halogen or LEDs system.

In this work the color dependence of resin composites with the background color was evaluated. The objective was to measure since what thickness the color of the sample stops being influenced by the color of the background over which the resin is placed and the methodology used in experiment was based in analyzing the contrast of digital images of the sample over a black background. The results shown that since 0.8 mm the images contrast becomes almost constant; it prove that since this thickness the color of resin composite depends on the optical resin properties only. The experiment was repeated under three conditions of luminosity to evaluate the influence of it on the image contrast and the results obtained were identical.