Early-stage cancer detection is challenging due to the lack of associated oral-tissue clinical features and absence of changes on conventional cellular-imaging, serological and histopathological exams. By using a molecular-sensitive optical technique such as Fourier-transform infrared (FT-IR) spectroscopy, disease-specific biochemical changes can be detected non-destructively, non-invasively and with small sample volumes. In this study, we have used FT-IR spectroscopy to analyze saliva samples of control, smoker, and occasional smoker groups in the fingerprint region (900cm-1 to 1800cm-1). Saliva-sample classification was performed with a neural network algorithm and leave-one-out validation. Correctly classified instances were 72.7% for the control group, 65.5% for occasional smokers and 75% for smokers.
Nd:YAG-laser associated to a photoabsorber, in the reduction of artificial caries in enamel was evaluated. Eighty bovine specimens with 6mm diameter and 2mm high were obtained and a half of the surface of each was protected as a control. Microdurometer and FTIR were performed initially and 8 groups (n=10) were obtained according to treatments: G1(- control): no-treatment; G2(+control): fluorophosphate; G3(Nd:YAG 60mJ/pulse, 10Hz, 48J/cm2, non-contact); G4(photoabsorber + Nd:YAG 60mJ); G5(Nd:YAG 80mJ/pulse, 10Hz, 64J/cm2); G6(photoabsorber + Nd:YAG 80mJ); G7(Nd:YAG 100mJ/pulse, 10Hz, 80J/cm2); G8(photoabsorber + Nd:YAG 100mJ). De-remineralization cycle were performed for induction of artificial caries and to interferometer, microdurometer and FTIR. Microhardness data were submitted to 2-way ANOVA and Tukey/Dunnett tests 5%. Statistically differences were obtained in the photoabsorberfactor individually and in the interaction between laser and photoabsorber. There was a lower percentage of microhardness loss in the groups with photoabsorber; G8 presented microhardness similar to G2. FTIR data were submitted to T-test 5%. Compared with G2, higher concentrations of carbonate were found in G4, G6 and G8; phosphate in G8; lower Amide-I concentration at G8 and higher Carbonate/Phosphate ratio at G4 and G6. The interferometry results were submitted to 3-way ANOVA of repeated measures 5%. There were statistically differences in the photoabsorber-factor individually and in the time-factor. Photoabsorber decreased the demineralization; Nd:YAG-laser without photoabsorber were less effective than fluoride; Nd:YAG-laser 100mJ with photoabsorber was as effective as fluoride and; the Nd:YAG-laser, associated or not to the photoabsorber, was no more effective than fluoride in the reduction of artificial decay.
It is known that Nd:YAG laser radiation on dental structure can increase enamel resistance to demineralization; however, few studies report its impact in orthodontics. This study aimed to verify the interaction of Nd:YAG laser and aluminum oxide sandblasting (Al2O3) as preconditioning treatment of lingual brackets bonding to quantify the shear bond strength (SBS) and to characterize the enamel after different surface preconditioning techniques. Thirty-five bovines’ incisors were divided in 5 groups (n=7), according to the preconditioning. All groups had the lingual brackets bonded with Transbond XT adhesive according to manufacturer’ protocol, and shear bonded after 72h. Samples were analyzed by Optical Coherence Tomography (OCT) and Scanning Eletronic Microscope (SEM) to verify enamel alterations. Optical attenuation coefficient (α) was measured before any preconditioning (T0) and after preconditioning surface (T1) for each group. Statistics analysis ANOVA-test was used, followed by Post Hoc Tukey for shear bond strength data, and Kruskal Wallis and post hoc Dunn test for α data. SEM and OCT qualitative analysis showed the melting effect with laser irradiation and enamel crystal surface disorganization with sandblasting in T1 and after shear bond. All groups were adequate for SBS and the statistical differences (p=0.0034) among groups showed better results for groups with techniques association (laser and Al2O3 used in this or in reverse order) and the highest SBS when laser was used after. The Al2O3 removes part of melting effect. The α had statistical difference (p= 0.0124) among groups, increasing with laser and Al2O3 isolated and decrease with techniques association.
Wound healing is a biological response in order to recover the tissue stability after injury. The impaired healing by third-degree, when the damage achieves the major part of dermis, is defined in four sequential and overlapping phases: Inflammation, transition, proliferative and maturative1. The role of biochemical cascade associated in each phase are still not fully understood, thus systematic evaluations tests are crucial. In fact, the gold standard to interrogate the molecular signature of wound healing is concern on immunohistochemical analysis. This approach tends to be laborious, time-consuming and require multiple assays2. Since Fourier transform infrared spectroscopy (FTIR) has been demonstrated in other studies to provide molecular change report upon biological samples, the present study aims to estimate the feasibility of FTIR to discriminate healthy and burned skin throughout wound stages.
Fourier Transform Infrared (FTIR) spectroscopy is a label-free analytical technique used to evaluate the chemical profile of a sample based on its molecular vibrations. The potential dermatological applications of FTIR spectroscopy has been well demonstrated over the past decades through many proof-of-concept studies evaluating cancerous and non-cancerous cutaneous diseases. Considering that the correctly identification of skin components plays an important role in the study of cutaneous diseases, the present study aims to evaluate the spectrochemical signatures of dermis and epidermis based on the pixels of a FTIR hyperspectral image collected from healthy skin.
This work aims was to correlate the changes in the optical attenuation coefficients obtained through the OCT technique with the values obtained in Knoop sectional microhardness tests over time in dental human enamel samples irradiated with the Nd: YAG laser and Acid Phosphate Fluoride (APF), aiming the prevention of caries lesions in vitro. After Ethical Committee approval, 160 enamel samples, obtained from 40 human tooth molars, were divided into 4 groups: Control group (where no treatment was performed); Fluoride group (APF - fluoride phosphate acidulated for 4 minutes); Fluoride-Laser group: APF followed by irradiation with Nd:YAG laser (DE = 84.9 J/cm2, contact mode, with the use of carbon paste as photoabsorver); Laser-fluoride group (irradiation with Nd:YAG laser followed by APF). The samples of all groups were subjected to pH cycling during 20 days. On days 5, 10, 15 and 20, 10 samples from each group were removed from the cycling for the Knoop sectional microhardness test. Two samples of each group, at each time, were randomly selected for the analysis with FTIR-ATR (Fourier transform infrared spectroscopy associated with attenuated total reflection technique). The analysis by ATR-FTIR showed changes in the chemical composition of the samples of the irradiated groups in relation to Control and Fluoride group. There was correlation between the values of sectional microhardness tests and the measured optical attenuation coefficient by OCT in irradiated dental enamel, showing that the association between fluoride application and Nd:YAG laser irradiation is an important tool for the prevention of tooth enamel demineralization.
In this study, FTIR spectroscopy was used to evaluate the overall biochemical status of necrotic tissue areas of cutaneous squamous cell carcinoma chemically-induced on mice. FTIR hyperspectral image collected from specimen showed high correlation with the photomicrograph obtained by light microscopy, in which we were able to identify clusters associated to keratin, necrosis and regions with no tissue. Alterations in the protein content were documented in the necrotic tissue areas, indicating changes on protein conformation.
Laser Induced Breakdown Spectroscopy (LIBS) is a technique capable to perform elemental analyses of a variety of samples, independent of matter state. Other spectroscopy techniques may require a destructive and time-consuming sample preparation. On the other hand, LIBS is a less destructive technique with no (or considerably less) sample preparation, using a relatively simple experimental setup. LIBS also provides a multielement analysis into one single spectrum acquisition, applying a Nd:YAG short-pulsed laser to ensure the stoichiometry between the sample and the generated plasma. LIBS have been applied on the study of carious lesions using a Nd:YAG into its fundamental emission at 1064 nm. It was shown that ratio of P/Ca and Zn/Ca can be used to monitor the cariogenic process. Another minor elements, e.g. C and Cu, associated with bacteria biofilm were also measured with the Nd:YAG laser. The fundamental wavelength emission (1064 nm) of Nd:YAG is coincident with a hydroxyapatite transmission window and it may affect the result. In order to address this issue a study used the second harmonic of the Nd:YAG laser at 532 nm. It was show that it is also possible perform LIBS on carious lesion using the Nd:YAG at 532 nm. However, there is not a work direct comparing the LIBS at 532 nm and 1064 nm for carious lesion detection. So, the aim of this work was to investigate the influence of laser wavelength on the LIBS performance for carious lesion detection. In both cases the carious lesion was detected with the advantage of no interference with hydroxyapatite at 532 nm.
The aim of this in vitro study was to evaluate the microshear bond strength (μSBS) of resin composite to enamel
etching by Er,Cr:YSGG laser with the use of two differents adhesives systems. Fifty freshly extracted human molars
halves were embedded in acrylic resin before preparation for the study, making a total of up to 100 available samples.
The specimens were randomly assigned into six groups (η=10) according to substrate pre-treatment and adhesive system
on the enamel. A two-step self-etching primer system (Clearfil SE Bond) and a universal adhesive used as an etch-andrinse
adhesive (Adper Single Bond Universal) were applied to the nonirradiated enamel surface according to
manufacturer’s instructions, as control groups (Control CF and Control SB, respectively). For the other groups, enamel
surfaces were previously irradiated with the Er,Cr:YSGG laser with 0.5 W, 75 mJ and 66 J/cm2 (CF 5 Hz and SB 5 Hz)
and 1.25 W, 50 mJ and 44 J/cm2 (CF 15 Hz and SB 15 Hz). Irradiation was performed under air (50%) and water (50%)
cooling. An independent t-test was performed to compare the adhesive systems. Mean μSBS ± sd (MPa) for each group
was 16.857 ± 2.61, 17.87 ± 5.83, 12.23 ± 2.02, 9.88 ± 2.26, 15.94 ± 1.98, 17.62 ± 2.10, respectively. The control groups
and the 50 mJ laser groups showed no statistically significant differences, regardless of the adhesive system used. The
results obtained lead us to affirm that the bonding interaction of adhesives to enamel depends not only on the
morphological aspects of the dental surface, but also on the characteristics of the adhesive employed and the
parameters of the laser.
Knowledge of dental structures is essential for understanding of laser interaction and its consequences during adhesion processes. Tubule density in dentin ranges from 4.900 to 90.000 per mm2, for diameters from 1 to 3 μm. Light propagation inside the tubules is associated with tubules orientation. To the best of our knowledge, there is no previous work in literature characterizing physical-chemical alterations in dentin. The dentin samples were irradiated with a Er,Cr:YSGG Laser at wavelength 2.78 μm, with an energy density of 9.46 J/cm2 , above the ablation threshold. ATRFTIR at wavenumbers 2000 to 700 cm-1 was used to evaluate the differences among third root region and tubules orientation.
We verified the changes promoted by ionizing radiation in bone tissue using FTIR. Samples of bovine bone were irradiated using Cobalt-60 with 0.01kGy, 0.1kGy, 1kGy, 15kGy and 75kGy. The effects of ionizing irradiation on chemical structure of bone, were studied considering the sub-bands of amide I, the crystallinity index and relation of organic and inorganic materials. ATR-FTIR spectroscopy showed changes in organic components and in hydroxyapatite crystals organization. High correlation with statistical significance was observed between (amideIII+collagen)/ ν1,ν3PO4, crystallinity and mechanical properties of the samples.
Considering the use of high intensity lasers for preventing dental caries, this blind in vitro study evaluated the compositional and fluorescence effects promoted by Nd:YAG laser (λ=1064 nm) when applied for prevention of progression of dentin caries, in association or not with topical application of acidulated phosphate fluoride (APF). Sixty bovine root dentin slabs were prepared and demineralized by 32h in order to create early caries lesions. After, the slabs were distributed into six experimental groups: G1- untreated and not submitted to a pH-cycling model; G2- untreated and submitted to a pH-cycling model; G3- acidulated phosphate fluoride application (APF); G4- Nd:YAG irradiation (84.9 J/cm2, 60 mJ/pulse); G5- treated with Nd:YAG+APF; G6- treated with APF+Nd:YAG. After treatments, the samples of groups G2 to G6 were submitted to a 4-day pH-cycling model in order to simulate the progression of early caries lesions. All samples were characterized by the micro-attenuated total reflection technique of Fourier transformed infrared spectroscopy (μATR-FTIR), using a diamond crystal, and by a fluorescence imaging system (FIS), in which it was used an illuminating system at λ= 405±30 nm. Demineralization promoted reduction in carbonate and phosphate contents, exposing the organic matter; as well, it was observed a significant reduction of fluorescence intensity. Nd:YAG laser promoted additional chemical changes, and increased the fluorescence intensity even with the development of caries lesions. It was concluded that the compositional changes promoted by Nd:YAG, when associated to APF, are responsible for the reduction of demineralization progression observed on root dentin.
Nonmelanoma skin cancers are the most common form of malignancy in humans. Between the traditional treatment ways, the photodynamic therapy (PDT) is a promising alternative which is minimally invasive and do not requires surgical intervention or exposure to ionizing radiation. The understanding of the cascade of effects playing role in PDT is not fully understood, so that define and understand the biochemical events caused by photodynamic effect will hopefully result in designing better PDT protocols. In this study we investigated the potential of the FTIR spectroscopy to assess the biochemical changes caused by photodynamic therapy after 10 and 20 days of treatment using 5-aminolevulinic acid (ALA) as precursor of the photosensitizer photoporphyrin IX (PpIX). The amplitude values of second derivative from vibrational modes obtained with FTIR spectroscopy showed similar behavior with the morphological features observed in histopathological analysis, which showed active lesions even 20 days after PDT. Thus, the technique has the potential to be used to complement the investigation of the main biochemical changes that photodynamic therapy promotes in tissue.
In laser cut clinical applications, the use of energy densities lower than the ablation threshold causes increase of
temperature of the irradiated tissue, which might result in an irreversible thermal damage. Hence, knowing the ablation
threshold is crucial for insuring the safety of these procedures. The aim of this study was to determine the ablation
threshold of the Er,Cr:YSGG laser in bone tissue. Bone pieces from jaws of New Zealand rabbits were cut as blocks of
5 mm × 8 mm and polished with sandpaper. The Er,Cr:YSGG laser used in this study had wavelength of 2780 nm, 20 Hz
of frequency, and the irradiation condition was chosen so as to simulate the irradiation during a surgical procedure. The
laser irradiation was performed with 12 different values of laser energy densities, between 3 J/cm2 and 42 J/cm2, during
3 seconds, resulting in the overlap of 60 pulses. This process was repeated in each sample, for all laser energy densities.
After irradiation, the samples were analyzed by scanning electron microscope (SEM), and it was measured the crater
diameter for each energy density. By fitting a curve that related the ablation threshold with the energy density and the
corresponding diameter of ablation crater, it was possible to determine the ablation threshold. The results showed that the
ablation threshold of the Er,Cr:YSGG in bone tissue was 1.95±0.42 J/cm2.
Objectives: to develop an apparatus for the detection of early caries lesions in enamel using the full extent of the tooth fluorescence spectrum, through the integration of a laser diode, fiber optics, filters and one portable spectrometer connected to a computer, all commercially available; to evaluate the developed device in clinical and laboratory tests, and compare its performance with commercial equipment. Methods: clinical examinations were performed in patients with indication for exodontics of premolars. After examinations, the patients underwent surgery and the teeth were stored individually. The optical measurements were repeated approximately two months after extraction, on the same sites previously examined, then histological analysis was carried out. Results: the spectral detector has presented high specificity and moderate sensitivity when applied to differentiate between healthy and damaged tissues, with no significant differences from the performance of the commercial equipment. The developed device is able to detect initial damages in enamel, with depth of approximately 300 μm. Conclusions: we successfully demonstrated the development of a simple and portable system based in laser-induced fluorescence for caries detection, assembled from common commercial parts. As the spectral detector acquires a complete recording of the spectrum from each tissue, it is possible to use it for monitoring developments of caries lesions.
Photodynamic therapy (PDT) has become a promising alternative for treatment of skin lesions such as squamous cell carcinoma. We propose a method to monitor the effects of PDT in a noninvasive way by using the optical attenuation coefficient (OAC) calculated from optical coherence tomography (OCT) images. We conducted a study on mice with chemically induced neoplastic lesions and performed PDT on these lesions using homemade photosensitizers. The response of neoplastic lesions to therapy was monitored using, at the same time, macroscopic clinical visualization, histopathological analysis, OCT imaging, and OCT-based attenuation coefficient measurement. Results with all four modalities demonstrated a positive response to treatment. The attenuation coefficient was found to be 1.4 higher in skin lesions than in healthy tissue and it decreased after therapy. This study shows that the OAC is a potential tool to noninvasively assess the evolution of skin neoplastic lesions with time after treatment.
The cutting of bone is routinely required in medical procedures, especially in dental applications. In such cases, bone
regeneration and new bone quality can determine the success of the treatment. This study investigated the main spectral
differences of undamaged and healed bone using the ATR-FTIR spectroscopy technique. Three rabbits were submitted
to a surgical procedure; a small piece of bone (3x3 mm2) was removed from both sides of their jaws using a high speed
drill. After 15 days, the rabbits were euthanized and the jaws were removed. A bone slice was cut from each side of the
jaw containing regions of undamaged and newly formed bone, resulting in six samples which were polished for
spectroscopic comparison. The samples were analyzed by FTIR spectroscopy using a diamond ATR accessory. Spectral
characteristics were compared and particular attention was paid to the proportion of phosphate to amide I bands and the
width of the phosphate band. The results show that the ratio of phosphate to amide I is smaller in new bone tissue than in
the undamaged bone, indicating a higher organic content in the newly formed bone. The analysis of the width of the
phosphate band suggests a crystallinity difference between both tissues, since the width was higher in the new bone than
in the natural bone. These results suggest that the differences observed in bone aging processes by FTIR spectroscopic
can be applied to the study of healing processes.
Dental Transillumination (DT) is a technique for imaging internal structures of teeth by detecting infrared radiation
transmitted throughout the specimens. It was successfully used to detect caries even considering dental enamel and
dentin scatter infrared radiation strongly. Literature reports enamel’s scattering coefficient is 10 to 30 times lower than
dentin; this explain why DT is useful for imaging pathologies in dental enamel, but does not disable its using for imaging
dental structures or pathologies inside the dentin. There was no conclusive data in the literature about the limitations of
using DT to access biomedical information of dentin.
The goal in this study was to present an application of DT to imaging internal structures of dentin. Slices of tooth were
confectioned varying the thickness of groups from 0.5 mm up to 2,5 mm. For imaging a FPA InGaAs camera Xeva 1.7-
320 (900-1700 nm; Xenics, Inc., Belgium) and a 3W lamp-based broadband light source (Ocean Optics, Inc., USA) was
used; bandpass optical filters at 1000±10 nm, 1100±10 nm, 1200±10 nm and 1300±50 nm spectral region were also applied to spectral selection. Images were captured for different camera exposure times and finally a computational processing was applied. The best results revealed the viability to imaging dent in tissue with thickness up to 2,5 mm without a filter (900-1700nm spectral range). After these results a pilot experiment of using DT to detect the pulp
chamber of an incisive human tooth was made. New data showed the viability to imaging the pulp chamber of specimen.
The chemical carcinogens from tobacco are related to over 90% of lung cancers around the world. The
risk of death of this kind of cancer is high because the diagnosis usually is made only in advanced stages.
Therefore, it is necessary to develop new diagnostic methods for detecting the lung cancer in earlier
stages. The Fourier Transform Infrared Spectroscopy (FTIR) can offer high sensibility and accuracy to
detect the minimal chemical changes into the biological sample. The aim of this study is to evaluate the
differences on infrared spectra between normal lung cells and precancerous lung cells transformed by
NNK. Non-cancerous lung cell line e10 (ATCC) and NNK-transformed e10 cell lines were maintained in
complete culture medium (1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F12
[DMEM/Ham's F12], supplemented with 100 ng/ml cholera enterotoxin, 10 lg/ml insulin, 0.5 lg/ml.
hydrocortisol, 20 ng/ml epidermal growth factor, and 5% horse serum. The cultures were maintained in
alcohol 70%. The infrared spectra were acquired on ATR-FTIR Nicolet 6700 spectrophotometer at 4 cm-1
resolution, 30 scans, in the 1800-900 cm-1 spectral range. Each sample had 3 spectra recorded, 30
infrared spectra were obtained from each cell line. The second derivate of spectra indicates that there are
displacement in 1646 cm-1 (amine I) and 1255 cm-1(DNA), allowing the possibility to differentiate the
two king of cells, with accuracy of 89,9%. These preliminary results indicate that ATR-FTIR is useful to
differentiate normal e10 lung cells from precancerous e10 transformed by NNK.
The diagnosis of dental caries at an early stage enables the implementation of conservative treatments based
on dental preservation. Several diagnostic methods have been developed, like visual-tactile and radiographic
are the most commons but are limited for this application. The Optical Coherence Tomography is a technique
that provides information of optical properties of enamel, which may change due to the decay process. The
objective of this study was to evaluate the ability of OCT to detect different stages of demineralization of tooth
enamel during the development of artificial caries lesions, taking as a reference standard for comparison
sectional microhardness testing. Different stages of caries lesions were simulated using the pH cycling model
suggested Feathestone and modified by Argenta. The samples were exposed to 0 (control group), 5, 10, 15,
20 and 25 days at a daily regimen of three hours demineralization followed by remineralization during 20
hours. It was used an OCT system with at 930nm. Sectional images were generated in all lesion region. The
results obtained from the OCT technique presented similar behavior to microhardness, except for the group
25 days, due to inability to perform indentations reading in areas of more intense demineralization. A linear
relationship was observed between the OCT and microhardness techniques for detection of demineralization
in enamel. This relationship will allow the use of OCT technique in quantitative assessment of mineral loss
and for the evaluation of incipient caries lesions.
The use of laser for bone cutting can be more advantageous than the use of drill. However, for a safe clinical application,
it is necessary to know the effects of laser irradiation on bone tissues. In this study, the Fourier Transform Infrared
spectroscopy (FTIR) was used to verify the molecular and compositional changes promoted by laser irradiation on bone
tissue. Bone slabs were obtained from rabbit's tibia and analyzed using ATR-FTIR. After the initial analysis, the samples
were irradiated using a pulsed Er,Cr:YSGG laser (2780nm), and analyzed one more time. In order to verify changes due
to laser irradiation, the area under phosphate (1300-900cm-1), amides (1680-1200cm-1), water (3600-2400cm-1), and
carbonate (around 870cm-1 and between 1600-1300cm-1) bands were calculated, and normalized by phosphate band area
(1300-900cm-1). It was observed that Er,Cr:YSGG irradiation promoted a significant decrease in the content of water
and amides I and III at irradiated bone, evidencing that laser procedure caused an evaporation of the organic content and
changed the collagen structure, suggesting that these changes may interfere with the healing process. In this way, these
changes should be considered in a clinical application of laser irradiation in surgeries.
Nonlinear microscopy imaging technique enable take both images of collagen fibers in dermis through second harmonic
generation (SHG) signal and elastic fibers by two-photon emission fluorescence microscopy (TPEFM). These techniques
are the most commonly used technique for turbid and thick tissue imaging and also to image biological samples which
presents highly ordered structural proteins without any exogenous label. The objective of this study is characterizing
dermis of third-degree burned skin by TPEFM and SHG technique. The modelocked laser (Spectra Physics) source used
in this study with pulse width of approximately 100 fs at 80 MHz was directed into a multiphoton microscope using a
laser scanning unit (Olympus Fluoview 300), mounted on an inverted confocal system microscope (Olympus IX81), with
focusing objective (40x, NA = 1.30). The samples were obtained from Wistar rats, male, adult. One dorsum area was
submitted to burn caused by vapour exposure. The biopsies obtained were cryosectioned in slices of 20 μm width.
Selected area of interface between the injured and healthy subdermal burned skin were imaged by TPEFM and SHG
technique. Two different autofluorescence signals are observed as a function of excitation wavelength. The
autofluorescence observed at 760 nm and 690 nm suggest components of extracellular matrix at differents depths. In
SHG images, collagen fibers are visible. According to the images obtained, these methodologies can be used to
characterize dermis of burned tissue as its healing process with reduced out-of-plane photobleaching and phototoxicity.
This study investigated the compositional and crystallographic changes on enamel when irradiated by Er,Cr:YSGG (λ=2.7μm, 8.5J/cm2) or Nd:YAG (λ=1064nm, 84.9J/cm2 associated with black coating), its resistance to demineralization when irradiation is associated with fluoride (APF-gel), and CaF2-like material formation and retention. Sample surfaces were analyzed by ATR-FTIR (4000-650cm-1, 4cm-1) resolution. Irradiation with Er,Cr:YSGG laser promoted a significant decrease on carbonate content of enamel. After
Nd:YAG irradiation, it was observed a significant decrease of carbonate and amides I and II. X-ray diffraction showed that both laser irradiations promoted formation of α-tricalcium phosphate and tetracalcium phosphate, and a significant increase on the crystal growth of the enamel apatite (ANOVA, p<0.05 was used for all analysis). These changes can explain the improved resistance of enamel to demineralization observed in the second part of the study, in which 240 enamel slices were divided in 8 groups, received 4 min of professional fluoride gel (APF-gel 1.23%F-) applied before or after irradiation. After treatments, the formation of calcium fluoride (CaF2) was determined. The remaining slabs of each group were submitted to a 10-day pH-cycling
model and, subsequently, enamel demineralization was evaluated by cross-sectional microhardness. Both lasers significantly reduced enamel demineralization (ANOVA, p<0.05), and the previous APF-gel application followed by laser showed the higher reduction of enamel demineralization. CaF2 formed before pH-cycling was
significantly higher in groups were APF was associated with laser irradiation. After demineralization, these groups also presented higher CaF2 retention in respect to isolated treatments (only APF or only laser), suggesting its anticaries potential.
Blue light, especially from LED devices, is a tool very frequently used in dental procedures. However, the investigations
of its effects on dental enamel are focused primarily on enamel demineralization and fluoride retention. Despite the fact
that this spectral region can inhibit enamel demineralization, the consequences of the irradiation on demineralized
enamel are not known. For this reason, we evaluated the effects of blue LED on enamel remineralization. Artificial
lesions formed in bovine dental enamel samples by immersion in undersaturated acetate buffer were divided into three
groups. In the first group (DE), the lesions were not submitted to any treatment. In the second (RE), the lesions were
submitted to remineralization. The lesions from the third group (LED+RE) were irradiated with blue LED (455nm,
1.38W/cm2, 13.75J/cm2 and 10s) before the remineralization. Cross-sectional microhardness was used to assess mineral
changes induced by remineralization under pH-cycling. The mineral deposition occurred preferably in the middle portion
of the lesions. Specimens from group RE showed higher hardness value than the DE ones. On the other hand, the mean
hardness value of the LED+RE samples was not statistically different from the DE samples. Results obtained in the
present study show that the blue light is not innocuous for the dental enamel and inhibition of its remineralization can
occur.
We aim to characterize natural caries enamel lesions by fluorescence spectroscopy. Sixty human samples with natural noncavitated caries lesions on smooth surfaces were selected and classified into three groups: dull, shiny, and brown lesions. All the samples were analyzed externally at the natural surface and after hemisectionig internally at the center of the lesion. The lesions were excited with a 405-nm InGaN diode laser and the fluorescence was collected with a single grating spectrometer. Four emission bands (455, 500, 582, and 622 nm) are identified in both sound and carious regions. The area under each emission band is correlated with the total area of the four bands for the sound and carious regions. The detected fluorescence from natural and cut surfaces through the caries lesions is not statistically different for the shiny and dull lesion, but is different [analysis of variance (ANOVA) (p<0.05)] for brown lesion at all emission bands. At the 405-nm excitation wavelength, the area of the fluorescence bands at 455 and 500 nm differ statistically for natural carious lesions and sound tissue.
The effects of phototherapy on herpes lesions have been clinically demonstrated by either preventing the lesion
formation or speeding their repair. The aim of this in vitro study was analyze the effect of phototherapy on epithelial
cells and HSV-1 in culture. Cultures of HSV-1 and epithelial cells (Vero cell line) were used. The irradiations were done
using a GaAlAs laser (660 e 780 nm, 4.0 mm2). One, two and three irradiations with 6 h-intervals were done. The
experimental groups were: Control: non-irradiated; 660 nm and 3 J/cm2 (2.8 sec); 660 nm and 5 J/cm2 (3.8 sec); 780 nm
and 3 J/cm2 (1.9 sec), and 780 nm and 5 J/cm2 (2.5 sec). The HSV-1 cytopatic effect and the cell viability of irradiated
cultures and controls were analyzed in four different conditions: irradiation of non-infected epithelial cells; epithelial
cells irradiated prior infection; virus irradiated prior infection; irradiation of HSV infected cells. The mitochondrial
activity and cytopathic effects were assessed. The number of irradiations influenced the cell growth positively and
proportionally, except for the 660 nm/ 3 J/cm2 group. Any variation in cytopathic effects was observed amongst the
experimental groups. The viability of infected cells prior irradiation was significantly higher than that of non-irradiated
cultures when 2 irradiations were done. Under the experimental conditions of this study we concluded that phototherapy
is capable of enhancing epithelial cell growth and prolonging cell viability of HSV-1 infected cells. Positive benefits of
phototherapy could be resultant from prolongation of infected cells viability, corroborating with host defenses.
We use the optical path difference (OPD) technique to quantify the organization of collagen fibers during skin repair of full-thickness burns following low-intensity polarized laser therapy with two different polarization incidence vectors. Three burns are cryogenerated on the back of rats. Lesion L is irradiated using the electric field vector of the polarized laser radiation aligned in parallel with the rat's occipital-caudal direction. Lesion L is irradiated using the electric field vector of the polarized laser radiation aligned perpendicularly to the aforementioned orientation. Lesion C is untreated. A healthy area labeled H is also evaluated. The tissue samples are collected and processed for polarized light microscopy. The overall finding is that the OPD for collagen fibers depends on the electric field vector of the incident polarized laser radiation. No significant differences in OPDs are observed between L and H in the center, sides, and edges of the lesion. Lesions irradiated using the electric field vector of the polarized laser radiation aligned in parallel with the rat's occipital-caudal direction show higher birefringence, indicating that collagen bundles in these lesions are more organized.
Optical Coherence Tomography was used to monitor subsurface caries evolution process in vitro. Human tooth was used and bacteria were employed to induce caries lesions. Twenty-five human third molars, were used in this study. The teeth were cut longitudinally at mesio-distal direction; the surfaces were coated with nail varnish except for two squared windows (2x4 mm); at the cement-enamel junction. Artificial lesions were induced by a S. Mutans microbiological culture. The samples (N = 50) were divided into groups according to the demineralization time: 3, 5, 7, 9 and 11 days. The culture medium, was changed each 48 hours. After the demineralization process the samples were rinsed with double-deionized water and stored in a humid environment. The OCT system was implemented with average power of 96 μW in the sample arm, providing a 23 μm of axial resolution. The images were produced with lateral scans step of 10 μm. The detection system was composed by a detector, a demodulator and a computer. With the images generated by OCT it was possible to determine the lesion depth as function of sample exposition time to microbiological culture. We observed that the depth of the lesion in the root dentine increased from 70 μm to 230 μm, depending of exposure time, and follows the bacterial population growth law. This OCT system accurately depicts hard dental tissue and it was able to detect early caries in its structure, providing a powerful contactless high resolution image of lesions.
The inner structure of teeth, i.e. the root canal anatomy, is very complex. However a good knowledge of endodontic architecture is the first step towards successful endodontic treatment. Optical coherence tomography (OCT) is a powerful technique to generate images of hard and soft tissue. Its images show dependency on the optical properties of the tissue under analysis. Changes in the scattering and absorption of tissues can be observed through the OCT images. In this work, we used optical coherence tomography to perform in vitro studies of the inner structure of the first molar of albino rats (Rattus norvegicus). Focusing on the pulp chamber and in the root canal, we compare the images generated with the OCT technique to the histology. We are analyzing the feasibility of OCT to help on the diagnostic of endodontic diseases.
Evaluation of molar dental restorations on enamel is performed using optical coherence tomography (OCT) with 10 µm resolution. Images of ~50 µm failure gaps in the restorations are demonstrated and the OCT images are compared with x-ray and optical microscopy pictures. The results demonstrate the potential of the technique for clinical evaluation of dental restorations.
Recently most analyses of Ca and P in different parts of tooth enamel have been performed semi-quantitatively. A direct and semi quantitative method for the determination of major and trace elements in human teeth by X-ray spectrometry is reported. The ratio Ca/P has been determined in the surface enamel of the third molar teeth. The surfaces were irradiated with short pulse laser Nd:YAG. The modifications in human dental enamel chemical composition for major and trace elements is here outlined. The accuracy of procedures was performed by analysis of natural hydroxyapatite as standard reference material. Results are consistent with other studies and they have indicated greater ratio Ca/P in irradiated groups in comparison to the non-irradiated group.
Low-intensity laser therapy (LILT) with adequate wavelength, intensity, and dose can accelerate tissue repair. However, there is still disperse information about light characteristics. Several works indicate that laser polarization plays an important role on the wound healing process. This study was conducted to verify the degree of linear polarization in normal and pathological rat skin samples. Artificial burns about 6 mm in diameter were created with liquid N2 on the back of the animals. The degree of polarization was measured in normal and pathological skin samples. It was verified that linearly polarized light can survive in the superficial layers of skin and it can be more preserved in skin under pathological condition when compared with health skin. The present study supports the hypothesis that polarized laser radiation can be used to treat open wounds and improve the healing.
Various materials and techniques have been investigated in order to minimize or eliminate microleakage in composite restorations. The CO2 laser (10.6 micrometer) removes the smear layer and creates an irregular surface able to promote micromechanical retention for adhesive restorative materials. Forty Class V cavities were performed with high-speed drill in 20 extracted human molar and randomly divided into 4 different groups: Group 1 -- CO2 laser (3 W, 2 Hz, 50 ms) and after 37% phosphoric acid etching on dentin and enamel surface; Group 2 -- 37% phosphoric acid etching and after CO2 laser; Group 3 -- CO2 laser; Group 4 -- 37% phosphoric acid etching. The cavity restored with composite resin (Z-100) and thermally stressed (700 cycles, 5 - 55 degree Celsius). After the samples were impermeabilized, immersed in 50% silver nitrate solution for 8 hours and sectioned with Isomet saw. The teeth were exposed to Photoflood light (G.E.) for 5 minutes to reveal the dye. Leakage was observed under stereomicroscope and evaluated with scores. Results were analyzed with ANOVA (p greater than 1%) and Tukey's test (p equals 5%) and showed significant lower microleakage in the group treated only with CO2 laser and phosphoric acid etching alone (group 3 and 4) than groups treated with phosphoric acid and CO2 laser together (group 1 and 2).
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 influence of low-intensity linearly polarized visible ((lambda) equals 632.8 nm) and near infrared ((lambda) equals 797 nm) laser radiation on healing of skin wounds was compared histologically. Three round lesions measuring about 6 mm in diameter were created at the end of the spinal column of 20 rats divided in two groups of 10 animals by burning the rat back skin with liquid nitrogen. Lesions #1 and #2 were illuminated using He-Ne or GaAlAs laser radiation. The laser polarization was aligned with the rat spinal direction in lesion #1, lesion #2 with the perpendicular relative orientation and lesion #3 was not irradiated (control). The animals were irradiated with a total dose of 1 J/cm2 on day 3, 8, 11 and 14. After each irradiation, two rats from each group were killed to obtain morphological information. On day 17 the last rats were killed. The irradiated lesions presented a significant acceleration on the wound repair compared to the control. The results showed that the relative orientation of the electric field has an essential role on the healing process if exposure is visible light. On the other hand, no morphological difference was observed between illuminated lesions by near infrared radiation with respect to polarization orientation.
This study was undertaken to investigate the influence of low level s- and p-polarized visible He-Ne laser irradiation on healing of skin wounds. Three lesions about 6 mm in diameter were induced on back of rates with liquid nitrogen: one was irradiated by He-Ne s-polarized radiation, other by He-Ne p-polarized and the third lesion was not irradiated. Two rats were killed after each irradiation to get sections of tissue for morphological analysis. The wound illuminated by p-polarized He-Ne was completely healed after 17 days when compared to other lesions which showed a poor degree of healing.
A prototype of Er:Tm:Ho:LiYF4 (Ho:YLF) laser, emitting at 2,065 micrometers , 1,25 J 5 Hz, with pulsewidth of 250 microsecond(s) was developed for biomedical applications. In order to verify the possibility of using this laser for cavities preparation in vivo, temperature rise in the pulp chamber must be known. Temperature changes were measured during Ho:YLF irradiation with 500 mJ/pulse, 30 pulses/position with energy density of 2079 J/cm2/pulse. Two groups of teeth were used: group I with pulp chamber empty and group II with pulp chamber filled with phase change material. In both cases, there were no temperature rise above 3,8 degree(s)C in the pulp chamber.
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