New biomaterials such as multi-walled carbon nanotubes oxide/graphene oxide (MWCNTO/GO), nanohydroxyapatite (nHAp) and combination of them together or not to acidulated phosphate fluoride gel (F) have been tested as protective coating before root dentin erosion. Fourteen bovine teeth were cleaned, polished, divided into two parts (n=28) and assigned to seven groups: (Control) – without previous surface treatment; F treatment; nHAp; MWCNTO/GO; F+nHAp; F+MWCNTO/GO and F+MWCNTO/GO/nHAp composites. Each sample had two sites of pre-treatments: acid etched area and an area without treatment. After the biomaterials application, the samples were submitted to six cycles (demineralization: orange juice, 10 min; remineralization: artificial saliva, 1 h). Micro energy-dispersive X-ray fluorescence spectrometry (μ-EDXRF) mapping area analyses were performed after erosive cycling on both sites (n=84). μ-EDXRF mappings showed that artificial saliva and MWCNTO/GO/nHAp/F composite treatments produced lower dentin demineralization than in the other groups. Exposed dentin tubules allowed better interaction of nanobiomaterials than in smear layer covered dentin. Association of fluoride with other biomaterials had a positive influence on acid etched dentin. MWCNTO/GO/nHAp/F composite treatment resulted in levels of demineralization similar to the control group.
The effects of laser etching on dentin are studied by microenergy-dispersive x-ray fluorescence spectrometry (μ-EDXRF) and scanning electron microscopy (SEM) to establish the correlation of data obtained. Fifteen human third molars are prepared, baseline μ-EDXRF mappings are performed, and ten specimens are selected. Each specimen received four treatments: acid etching (control-CG) or erbium:yttrium–aluminum–garnet (Er:YAG) laser irradiation (I—100 mJ, II—160 mJ, and III—220 mJ), and maps are done again. The Ca and P content are significantly reduced after acid etching (p<0.0001 ) and increased after laser irradiation with 220 mJ (Ca: p<0.0153 and P: p=0.0005 ). The Ca/P ratio increased and decreased after CG (p=0.0052 ) and GI (p=0.0003 ) treatments, respectively. CG treatment resulted in lower inorganic content (GI: p<0.05 , GII: p<0.01 , and GIII: p<0.01 ) and higher Ca/P ratios than laser etching (GI: p<0.001 , GII: p<0.01 , and GIII: p<0.01 ). The SEM photomicrographies revealed open (CG) and partially open dentin tubules (GI, GII, and GIII). μ-EDXRF mappings illustrated that acid etching created homogeneous distribution of inorganic content over dentin. Er:YAG laser etching (220 mJ) produced irregular elemental distribution and changed the stoichiometric proportions of hydroxyapatite, as showed by an increase of mineral content. Decreases and increases of mineral content in the μ-EDXRF images are correlated to holes and mounds, respectively, as found in SEM images.
We examine the morphological and chemical changes in the pulp chamber dentin after using endodontic agents by scanning electron microscopy (SEM), Fourier transform Raman spectroscopy (FT-Raman), and micro energy-dispersive x-ray fluorescence spectrometry (μEDXRF). Thirty teeth were sectioned exposing the pulp chamber and divided by six groups (n = 5): NT-no treatment; CHX-2% chlorhexidine; CHXE-2% chlorhexidine+17% EDTA; E-17% EDTA; SH5-5.25% NaOCl; SH5E-5.25% NaOCl+17% EDTA. The inorganic and organic content was analyzed by FT-Raman. μEDXRF examined calcium (Ca) and phosphorus (P) content as well as Ca/P ratio. Impressions of specimens were evaluated by SEM. Data were submitted to Kruskal-Wallis and Dunn tests (p<0.05). Differences were observed among groups for the 960 cm−1 peak. Ca and P content differences were significant (SH5>NT = SH5E>CHX>E>CHXE). CHXE and E presented the highest Ca/P ratio values compared to the other groups (p<0.05). The SEM images in the EDTA-treated groups had the highest number of open tubules. Erosion in the tubules was observed in CHX and SH5E groups. Endodontic agents change the inorganic and organic content of pulp chamber dentin. NaOCl used alone, or in association with EDTA, was the most effective agent considering chemical and morphological approaches.
The effects of laser etching, decontamination, and storage treatments on dentin components were studied by energy-dispersive X-ray fluorescence spectrometry (EDXRF). Thirty bovine incisors were prepared to expose the dentin surface and then divided into two main groups based upon the decontamination process and storage procedure: autoclaved (group A, n=15) or stored in aqueous thymol solution (group B, n=15). The surfaces of the dentin slices were schematically divided into four areas, with each one corresponding to a treatment subgroup. The specimens were either etched with phosphoric acid (control subgroup) or irradiated with erbium-doped yttrium-aluminum-garnet (Er:YAG) laser (subgroups: I-80 mJ, II-120 mJ, and III-180 mJ). Samples were analyzed by micro-EDXRF, yielding three spectra for each area (before and after treatment). Surface mappings covering an area of 80×60 points with steps of 20 µm were also performed on selected specimens. The amount of Ca and P in group A specimens decreased significantly (P<0.05) after the acid etching and the Ca/P ratio increased (P<0.001). Er:YAG laser-etching using lower laser energies did not produce significant changes in dentin components. The mapping data support the hypothesis that acid etching on dentin produced a more chemically homogeneous surface and thus a more favorable surface for the diffusion of adhesive monomers.
The effects of laser etching, decontamination, and storage treatments on dentin components were studied using Fourier transform (FT)-Raman spectroscopy. Thirty bovine incisors were prepared to expose the dentin surface and then divided in two main groups based upon the decontamination process and storage procedure: autoclaved (group A, n=15) or stored in thymol aqueous solution (group B, n=15). The surfaces of the dentin slices were schematically divided into four areas, with each one corresponding to a treatment subgroup. The specimens were either etched with phosphoric acid (control subgroup) or irradiated with erbium-doped yttrium-aluminum-garnet (Er:YAG) laser (subgroups: I-80 mJ, II-120 mJ, and III-180 mJ, and total energy of 12 J). Samples were analyzed by FT-Raman spectroscopy; we collected three spectra for each area (before and after treatment). The integrated areas of five Raman peaks were calculated to yield average spectra. The areas of the peaks associated with phosphate content (P<0.001), type I collagen, and organic C-H bonds (P<0.05) were reduced significantly in group A (control). Analyses of samples irradiated with reduced laser energies did not show significant changes in the dentin components. These results suggest that thymol storage treatment is advised for in vitro study; furthermore, 12 J of Er:YAG laser energy does not affect dentin components.
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.
This in vitro pilot study investigated the CO2 laser effects on demineralization inhibition in sound human dental enamel. Thirty six human enamel specimens were used and randomly assigned to 6 groups, as follows: I) Control; II) 1W; III) 2W; IV) 3W; V) 4W; VI) 5W. Group I one was kept as control and others were irradiated using a pulsed CO2 laser (λ=10.6 μm) with low crescent potencies. Fourier Transform Raman Spectroscopy was used to study the surface composition of specimens after irradiation. One specimen from each group was analyzed by Scanning Electron Microscopy and the remaining ones were submitted to an 8-day pH cycling model with use of fluoridated toothpaste twice a day. After pH-cycling, the cross-sectional microhardness was performed for mineral loss (ΔZ) quantification. The data were analyzed by ANOVA and Tuckey test (α=0.05). No changes were found either in SEM photomicrographies or RAMAN Spectra of the specimens in all groups. The ΔZ values (n=5; mean±SD) for I-VI groups were: 1741.6±725.3a; 1782.7±639.0a; 1427.2±237.0a; 1780.6±552.4a; 1385.2±602.2a; 943.1±228.1a respectively. The highest percentage of caries inhibition was found in group VI (45.8%); however the differences between ΔZ of the groups were not statistically significant. The use of CO2 laser with low fluencies did not prevent more caries development than the use of fluoridated toothpaste, even though group VI had present good results in caries inhibition. Energy densities higher than 0.0125 J/cm2 should be used to promote chemical or morphological changes on enamel surface, which are able of inhibiting mineral.
FT-Raman spectroscopy was used to investigate the influence of the Er:YAG laser irradiation into the human dentin structure. Polished dentin disks with 4mm thickness from six third molars were irradiated with Er:YAG laser. The dentin disks were prepared by polishing through a series of SiO2 papers with water and cleaned by ultrasonic system. Four pretreatment were performed. The disks were etched with 37% phosphoric acid for 15 s (control group), Er:YAG laser 80mJ, 3Hz, and 30s. (Group I), Er:YAG laser 120mJ, 3Hz, 30s. (Group II) and Er:YAG laser 180mJ, 3Hz, and 30s. (Group III). The FT-Raman spectra obtained from normal and treated dentin were analyzed. Attention was paid to the inorganic and organic dentin component (961, 2941cm-1). FT-Raman spectroscopy showed that the mineral and organic content were less affected by the acid etching and by the Er:YAG laser irradiation with 80mJ. Pulse energies of 120 and 180mJ showed to produce more reduction in the organic and inorganic content associated with more reduction in the peak areas at 961 and 2941cm-1. FT-Raman spectroscopy provided information of dentin chemical constituents with non-chemical sampling preparation.
Enamel components are related to enamel caries susceptibility, thus, non-destructive techniques to be used in selecting homogeneous dental enamel have been studied. This study aimed to determine the enamel components that make it more susceptible to in vitro demineralization. Fourier transform Raman Spectroscopy (FTRS) was used to verify the relative amounts of organic material and enamel mineral before and after being submitted to an 8-day pH cycling model. FTRS was performed in 30 enamel slabs, which were subsequently demineralized; next, the slabs were again analyzed by FTRS. The cross-section microhardness was performed for mineral loss (ΔZ) quantification. Slabs that presented the greatest differences in the caries development pattern, considering the ΔZ mean obtained (ΔZ=1,510.1±623.4; n=30), were selected in order to constitute 2 groups with statistically different ΔZ values, more demineralized group (MDG) and less demineralized group (LDG), which had ΔZ=2,368.9±421.7a and ΔZ=909.2±229.2b (n=8), respectively. The differences between both MDG and LDG, regarding enamel components (phosphate, carbonate and organic matrix) determined by FTRS before and after pHC, were accessed by t test (significance level=0.05). The results showed that all groups presented fewer carbonate and organic contents after demineralization. LDG showed no difference in phosphate content before and after pHC. Before pHC, MDG carbonate content was statistically greater than the one found in LDG. The presence of a correspondent calcium fluoride band was not observed in enamel spectrum. In conclusion, only carbonate quantity influenced enamel susceptibility to in vitro demineralization and FT-RAMAN is an appropriate technique to select homogeneous enamel samples.
Raman Spectroscopy was used to examine the distribution of the mineral and organic components in the human dentin before and after the chemical and thermal etching process. Polished dentin disks (n = 6/group) with 4mm thickness from twelve third molars were irradiated with Er:YAG laser. The dentin disks were prepared by polishing through a series of SiO2 papers with water and cleaned by ultrasonic system. Four pretreatment were performed. The disks were etched with 37% phosphoric acid (group I), Er:YAG laser 80mJ, 3Hz, 30s. (group II), Er:YAG laser 120mJ, 3Hz, 30s. (group III) and Er:YAG laser 180mJ, 3Hz, 30s. (group IV). The Raman spectra obtained from normal and treated dentin were analyzed. Attention was paid to the mineral PO4 (962 cm-1), CO3 (1073 cm-1) and to the organic component (1453cm-1). Raman spectroscopy showed that the mineral and organic dentin content were more affected in autoclaved teeth than in the specimens treated by Thymol. Peak area reduction in the specimens treated by Thymol in group I and II showed to be the most conservative procedures regarding to changes in organic and inorganic dentin components. Pulse energies of 120 and 180mJ showed to produce more reduction in the organic and inorganic content associated with more reduction in the peak areas at 960 and 1453cm-1.
Raman Spectroscopy was used to examine the distribution of the organic components in the human dentin before and after the chemical and thermal etching process. Polished dentin disks (n = 6/group) with 4mm thickness from twelve third molars were irradiated with Er:YAG laser. The dentin disks were prepared by polishing through a series of SiO2 papers with water and cleaned by ultrasonic system. Four pretreatment were performed. The disks were etched with 37% phoshporic acid for 15 s (group 1), Er:YAG laser 80 mJ, 3Hz, 30s. (group II), Er:YAG laser 120 mJ, 3Hz, 30s. (group III) and Er:YAG laser 180mJ, 3Hz, 30s. (group IV). The Raman spectra obtained from normal and treated dentin were analyzed. Attention was paid to the organic component (1453cm-1). Raman spectroscopy showed that the organic dentin content were more affected in autoclaved teeth than in the specimens treated by Thymol. Peak area reduction in the specimens treated by Thymol in group I and II showed to be the most conservative procedures regarding to changes in organic dentin components. Pulse energies of 120 and 180 mJ showed to preduce more reduction in the organic content associated with more reduction in the peak areas at 1453 cm-1.
We present the results of the Vicker's hardness test and the use of near-infrared Raman spectroscopy (RS) to measure in vitro the degree of conversion (DC) of a bis(phenol)-A-glycidyl-dimethacrylate-based composite resin, photoactivated by both a halogen lamp (power density = 478 mW/cm2; 8-mm diameter spot) and an argon laser (power density = 625 mW/cm2; 7-mm diameter spot). The degree of conversion was estimated by analyzing the relative intensities between the aromatic CC stretching Raman mode at 1610 cm–1 and the methacrylate CC stretching Raman mode (1640 cm–1) on top and bottom surfaces. For the hardness evaluation, the samples were embedded in polyester resin and three indentations with a 50-g load for 10 s were made on the top surface. The higher relative DC values achieved by the photoactivation of a composite resin by the argon laser suggest a better biocompatibility in the bottom surface. The correlation test showed that the higher Vicker's hardness number (VHN) values were associated with higher DC values. The derivative analysis showed a greater curing rate from 5 to 20 s of exposure. The comparison of VHN and DC values with both light sources at each curing time showed that a small change in conversion is related to a large change in hardness. Raman spectroscopy is more sensitive to changes in the first stages of curing reaction than later ones, and the Vicker's hardness assay is more sensitive to changes in the last stages.
The aim of this work was to characterize the degree of photoactivation of the Z250 resin through photoacoustics. In this technique, the signal detected is proportional to the heat produced in a sample as a consequence of light absorption. This technique has been used for more than 20 years as a work tool in diverse fields of biological and biomedical sciences. Through photoacoustic measurements, it is possible to study optical and thermal properties of samples, and to obtain information on the characteristic times involved in photoinduced processes, as the photoactivation of composed resins. After application on the surface, the Z250 resin is photoactivated by incidence of continuous light (λ = 475 ± 15 nm) coming from a photodiode. This leads to the polymerization of the resin, modifying its thermal properties. The experimental method employed in this work was the following: a) the resin was applied on an aluminum sheet placed in contact with the photoacoustic cell (front incidence); b) modulated white light was applied in the lower surface of the aluminum sheet, black-painted to increase the light absorption; c) the photothermal signal was observed. Polymerization was evaluated through the alteration of the photoacoustic signal caused by the activation of the resin promoted by the incidence of the continuous light, for different activation times. The results show that the polymerization of the resin substantially modifies the photoacoustic signal, indicating that the degree of photoactivation can be evaluated through photoacoustic measurements.
The degree of conversion (DC) of Z100 (3M) composite resin photoactivated by both Light-Emitting Diode and halogen lamp was evaluated by FT-Raman Spectroscopy. Eighteen circular blocks of resin (Φ 6mm X 3mm) were cured either by the LED (λ = 470nm, 190mW/cm2,Φ = 8mm) and by the halogen lamp (λ = 400-500nm, 600mW/cm2,Φ = 7mm) varying the irradiation time (20, 40 and 60s). The resin surfaces were analyzed immediately after curing by FT-Raman Spectroscopy. The FT-Raman results showed the reduction in monomer trough changes in the intensity of the
peak at 1640cm-1 as a function of irradiation time. The samples that were cured by 60s with LED source reached the
maximum degree of conversion of 52% and 50% for the irradiated and non-irradiated surface, respectively. Whereas the samples cured by the same irradiation time, but with halogen lamp, those values were around only 4% higher for each surface with no statistically significant difference. It was observed no statistically significant differences in the DC values between both light sources used with 40s of irradiation. Therefore we conclude that, despite of their reduced
irradiance, LEDs can cure composite resin ensuring a DC without statistically significant differences from the halogen lamp.
Raman Spectroscopy was used in the present investigation to evaluate the degree of conversion of composite resin, photoactivated by the Halogen lamp, the Argon Laser beam and by the Light Emitting Diode. Eighteen circular blocks of resin (7mm X 2,5mm) were cured by the Halogen light source (n = 9, λ = 400-500nm, Power density = 478
mW/cm2), by the Argon laser beam (n = 9, λ = 488nm, Power density = 625 mW/cm2) and nine blocks (6mm X 3mm)
by the LED (n = 9, λ = 475 ± 15nm, Power density = 190mW/cm2) using the same irradiation time (20, 40 and 60
seconds). The resin surfaces were analyzed immediately after curing by Raman and FT-Raman Spectroscopy. The Raman results show changes of the relative intensities between the peaks at 1610 and the 1640cm-1, as a function of irradiation time. After 60s of irradiation time, the maximum degree of conversion reached for the samples cured either by the Argon laser, the Halogen lamp and LED were 66,4%, 62,2% and 52%, respectively. The Argon laser was more
effective and shown a better biocompatibility, with less residual monomer in the bottom.
Raman Spectroscopy was used on the present investigation to monitor the degree of conversion of microparticled composite resin (Z100-3M), polymerized by both the conventional halogen light and the Argon Laser beam. Circular blocks of composite 6mm diameter and 3mm of thickness were used on this study. The tip of the halogen light source ((lambda) = 400-500nm, 478mW/cm2) or the Argon laser beam ((lambda) = 488nm, 624mW/cm2) was positioned on the surface of the composite resin and both activated for different irradiation times (5, 10, 20, 30, 40 and 60 seconds). The top surface which was directly irradiated and the non-irradiated (inferior) surface were analyzed immediately after curing by Raman Spectroscopy. The Raman results show systematic changes of the relative intensities between the peaks at 1610 (aromatic C=C stretching mode) and the 1640 cm-1 (methacrylate C=C stretching mode), as a function of irradiation time. The degree of conversion was calculated based on the relative intensity change of these two modes and compared for each light source. The change in the relative intensity shows that Raman Spectroscopy can be used as an effective method to study the degree of conversion of composite resins.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.