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.
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.
Computer-assisted diagnoses (CAD) are performed by systems with embedded knowledge. These systems work as a second opinion to the physician and use patient data to infer diagnoses for health problems. Caries is the most common oral disease and directly affects both individuals and the society. Here we propose the use of dental fluorescence images as input of a caries computer-assisted diagnosis. We use texture descriptors together with statistical pattern recognition techniques to measure the descriptors performance for the caries classification task. The data set consists of 64 fluorescence images of in vitro healthy and carious teeth including different surfaces and lesions already diagnosed by an expert. The texture feature extraction was performed on fluorescence images using RGB and YCbCr color spaces, which generated 35 different descriptors for each sample. Principal components analysis was performed for the data interpretation and dimensionality reduction. Finally, unsupervised clustering was employed for the analysis of the relation between the output labeling and the diagnosis of the expert. The PCA result showed a high correlation between the extracted features; seven components were sufficient to represent 91.9% of the original feature vectors information. The unsupervised clustering output was compared with the expert classification resulting in an accuracy of 96.88%. The results show the high accuracy of the proposed approach in identifying carious and non-carious teeth. Therefore, the development of a CAD system for caries using such an approach appears to be promising.
We have developed an empirical method to determine light distribution in optical phantom. This method is based on
experimental measurements of light fluence rate as a function of position inside the medium. Milk solution and fat
emulsion were chosen as turbid media and a HeNe laser at 633nm was used as light source. Light fluence rate within the
phantoms was detected by an isotropic fiber optic probe. The data were collected for a collimated narrow laser beam and
arranged in a tridimensional matrix. Using this matrix, simple mathematical operations were used to simulate different
conditions of irradiation geometry. Comparison between experimental measurements and mathematical simulations
show that our method can be used to recover light distribution in biological tissue for any condition of illumination, since
we have previously performed simple measurements in a sample using a narrow beam. Further in vivo studies must be
performed to validate the method here proposed.
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.
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.
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 100oC 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 25oC. Time and temperature are important factors to promote a homogeneous structure polymerized composite resin more than the light source type, halogen or LEDs system.
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.
KEYWORDS: Light sources, Light emitting diodes, Chemical reactions, Dental bleaching, Blue light emitting diodes, Absorption, RGB color model, 3D modeling, Hydrogen, Chemical elements
The bleaching process is been objective of many studies since the beginning of the XX century. Heat has been used to activate the hydrogen peroxide; the aesthetic results were satisfactory, but associated with this process high incidence of hypersensitivity as well as radical endodontic treatment was observed making this technique clinically hard to implemented.
Nowadays the dental bleaching is one of the most wanted aesthetic procedures by the population at the dental office. With the utilization of new light sources as LASER and LED a technique to evaluate the efficiency of photo-bleaching of many pigments is necessary.
This work demonstrates a new method to quantify the breakage of pigments on a cellulose matrix using a blue LED system with 1W/cm2. We employed a computational analysis and digital spectroscopy. These matrixes were used because of its inert physical-chemical properties.
The obtained results are within the expectative, where the groups irradiated with light presents more broken pigments that the group with no light, it was also possible to observe on this experiment that light acts decreasing the free energy of the reaction and that way speeding up the rate of bleaching.
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