共查询到20条相似文献,搜索用时 390 毫秒
1.
Esteves-Oliveira M. Apel C. Gutknecht N. Velloso W. F. Cotrim M. E. B. Eduardo C. P. Zezell D. M. 《Laser Physics》2008,18(4):478-485
This study investigated whether subablative-pulsed CO2 laser (10.6 μm) irradiation, using fluences lower than 1 J/cm2, was capable of reducing enamel acid solubility. Fifty-one samples of bovine dental enamel were divided into three groups: control group, which was not irradiated (CG); group laser A (LA) irradiated with 0.3 J/cm2; and group laser B (LB) irradiated with 0.7 J/cm2. After irradiation, the samples were subjected to demineralization in an acetate buffer solution and were then analyzed by SEM. A finite-element model was used to calculate the temperature increase. The calcium and phosphorous content in the demineralization solution were measured with an ICP-OES. ANOVA and the t-test pairwise comparison (p < 0.016) revealed that LB showed significantly lower mean Ca and P content values in the demineralization solution than other groups. A reduction in the enamel solubility can be obtained with pulsed CO2 laser irradiation (0.7 J/cm2, 135 mJ/pulse, 74 Hz, 100 μs) without any surface photomodification and a less than 2°C temperature increase at a 3-mm depth from the surface. 相似文献
2.
This study evaluated the change that occurs in dental enamel under action of oven heating or Er,Cr:YSGG laser irradiation
aiming to obtain a structure more resistant to demineralization. Enamel powder was obtained from bovine teeth. Samples were
subjected to oven heating at temperatures of 200, 400, 600, 800, and 1000°C or during laser irradiation with energy densities
of 7.53, 10.95, and 13.74 J/cm2. The infrared thermography was used to measure the surface temperature generated in the solid samples of enamel during lasers
irradiation. The samples were analyzed by Fourier transform infrared spectroscopy (FTIR), which shows changes on enamel oven
heated or laser irradiated, due to treatments, related to carbonates, adsorbed water and hydroxyl content. These compositional
effects were more evident in lased samples. These changes may alter the material properties such as its solubility, and decrese
of demineralization that is important for caries prevention. 相似文献
3.
W. C. de Souza-Zaroni A. C. P. Freitas F. S. Hanashiro C. Steiner-Oliveira M. Nobre-dos-Santos M. N. Youssef 《Laser Physics》2010,20(2):537-543
Although the cariostatic effects of CO2 laser on enamel have been shown, its effects on root surface demineralization remains uncertain. The objectives of this in
vitro research was to establish safe parameters for a pulsed 10.6 μm CO2 laser and to evaluate its effect on morphological features of the root surface, as well as on the reduction of root demineralization.
Ninety-five human root surfaces were randomly divided into five groups: G1-No treatment (control); G2—2.5 J/cm2; G3—4.0 J/cm2; G4—5.0 J/cm2; and G5—6.0 J/cm2. Intrapulpal temperature was evaluated during root surface irradiation by a thermocouple and morphological changes were evaluated
by SEM. After the surface treatment, the specimens were submitted to a 7-day pH-cycling model. Subsequently, the cross-sectional
Knoop microhardness values were measured. For all irradiated groups, intrapulpal temperature changes were less than 1.5°C.
Scanning electron microscopy images indicated that fluences as low as 4.0 J/cm2 were sufficient to induce morphological changes in the root surface. Additionally, for fluences reaching or exceeding 4.0
J/cm2, laser-induced inhibitory effects on root surface demineralization were observed. It was concluded that laser energy density
in the range of 4.0 to 6.0 J/cm2 could be applied to a dental root to reduce demineralization of this surface without compromising pulp vitality. 相似文献
4.
A. Mandelis R. Jeon A. Matvienko S. H. Abrams B. T. Amaechi 《The European physical journal. Special topics》2008,153(1):449-454
Recent trends in biothermophotonics of teeth are
presented. The presentation is centered on the development of clinical-level
frequency-domain photothermal radiometry and modulated luminescence to
address issues associated with the early diagnosis of demineralization
caries in human teeth. Biothermophotonic principles and applications to the
detection of the carious state in human teeth as embodied by laser
photothermal radiometry are presented and further supported by modulated
luminescence. The emphasis is on recent developments with regard to
abilities of these techniques to diagnose interproximal lesions between
teeth, etching with phosphoric acid and with an artificial demineralization
gel in order to simulate early demineralization, as well as demineralization
and remineralization of dental crown enamel and root dentin. These are
lesions which normally go undetected by X-ray radiographs. Comparisons with
X rays, Micro-Computed Tomography (μ-CT) and Transverse
Micro-Radiography (TMR) are discussed. A theoretical model involving coupled
diffuse photon density and thermal-wave fields is developed and applied to
frequency scans from demineralized artificial lesions to produce
quantitative values for optical and thermophysical parameters of teeth as
well as the thickness of the induced lesion. 相似文献
5.
A. Lohner M. Huber S. D. Ganichev W. Prettl H. Niederdellmann 《International Journal of Infrared and Millimeter Waves》2000,21(3):407-419
Visible light emission of dental hard substances excited by high-power infrared pulses of a tunable TEA CO2 laser has been investigated. A clear correlation between observed visible light emission, plasma formation as well as ablation of dental hard tissue has been demonstrated. Both, the highly nonlinear infrared to visible upconversion process and the ablation efficiency show a sharp spectral resonance close to a vibrational mode of PO4 at 1090 cm-1 in dental enamel and dentin. The influence of strong infrared light impulses on dental hard tissue is examined by performing upconversion studies of visible light emission of human dental enamel and dentin. Our experimental setup allows one to determine the plasma formation threshold being important in dental surgery. 相似文献
6.
D. P. Jacomassi E. C. Lins A. N. S. Rastelli C. Kurachi V. S. Bagnato 《Laser Physics》2009,19(12):2230-2235
The aim of this study was to evaluate the shrinkage of a microhybrid dental composite resin photo-activated by one LED with
different power densities by means of speckle technique. The dental composite resin Filtek™ Z-250 (3M/ESPE) at color A2 was used for the samples preparation. Uncured composite was packed in a metallic mold and irradiated during 20 s from 100
to 1000 mW cm−2. For the photo-activation of the samples, it was used a LED prototype (Light Emission Diode) with wavelength centered at
470 nm and adjustable power density until 1 W cm−2. The speckle patterns obtained from the bottom composite surfaces were monitored using a CCD camera without lens. The speckle
field is recorded in a digital picture and stored by CCD camera as the carrier of information on the displacement of the tested
surface. The calculated values were obtained for each pair of adjacent patterns and the changes in speckle contrast as a function
of time were obtained from six repeated measurements. The speckle contrasts obtained from the bottom surface with 100 mW cm−1 were smaller than those than the other power densities. The higher power densities provided the higher shrinkage. 相似文献
7.
Characterization of enamel caries lesions in rat molars using synchrotron X‐ray microtomography 下载免费PDF全文
R. D. Free K. DeRocher S. R. Stock D. Keane K. Scott-Anne W. H. Bowen D. Joester 《Journal of synchrotron radiation》2017,24(5):1056-1064
Dental caries is a ubiquitous infectious disease with a nearly 100% lifetime prevalence. Rodent caries models are widely used to investigate the etiology, progression and potential prevention or treatment of the disease. To explore the suitability of these models for deeper investigations of intact surface zones during enamel caries, the structures of early‐stage carious lesions in rats were characterized and compared with previous reports on white spot enamel lesions in humans. Synchrotron X‐ray microcomputed tomography non‐destructively mapped demineralization in carious rat molar specimens across a range of caries severity, identifying 52 lesions across the 30 teeth imaged. Of these lesions, 13 were shown to have intact surface zones. Depth profiles of fractional mineral density were qualitatively similar to lesions in human teeth. However, the thickness of the surface zone in the rat model ranges from 10 to 58 µm, and is therefore significantly thinner than in human enamel. These results indicate that a fraction of lesions in rat caries possess an intact surface zone and are qualitatively similar to human lesions at the micrometer scale. This suggests that rat caries models may be a suitable analog through which to investigate the structure of surface zone enamel and its role during dental caries. 相似文献
8.
W. Kabbach D. M. Zezell M. C. Bandéca T. M. Pereira M. F. Andrade 《Laser Physics》2010,20(9):1833-1837
This study measured the critical temperature reaching time and also the variation of temperature in the surface of the cervical
region and within the pulp chamber of human teeth submitted to dental bleaching using 35% hydrogen peroxide gel activated
by three different light sources. The samples were randomly divided into 3 groups (n = 15), according to the catalyst light source: Halogen Light (HL), High Intensity Diode Laser (DL), and Light Emmited Diode (LED). The results of temperature variation were submitted to the analysis of variance and
Tukey test with p < 0.05. The temperature increase (mean value and standard deviation) inside the pulp chamber for the HL group was 6.8 ± 2.8°C;
for the DL group was 15.3 ± 8.8°C; and for the LED group was 1.9 ± 1.0°C for. The temperature variation (mean value and standard
deviation) on the tooth surface, for the group irradiated with HL was 9.1 ± 2.2°C; for the group irradiated with DL were 25.7
± 18.9°C; and for the group irradiated with LED were 2.6 ± 1.4°C. The mean temperature increase values were significantly
higher for the group irradiated with DL when compared with groups irradiated with HL and LED (p < 0.05). When applying the inferior limits of the interval of confidence of 95%, an application time of 38.7 s was found
for HL group, and 4.4 s for DL group. The LED group did not achieve the critical temperatures for pulp or the periodontal,
even when irradiated for 360 s. The HL and DL light sources may be used for dental bleaching for a short period of time. The
LED source did not heat the target tissues significantly within the parameters used in this study. 相似文献
9.
《Radiation measurements》2000,32(3):163-167
We are reporting an alternative method of extracting useful dose information from complex EPR spectra of dental enamel. Digital differentiation of the initial first derivative spectrum followed by filtering is used to clearly distinguish the radiation-induced signal from the native background signal. The peak-to-peak height of the resulting second derivative of the signal is then measured as an indication of absorbed dose. This method does not require preliminary elimination of the native background signal, and is not effected by any uncertainty in the determination of the background signal or by errors resulting from the subtraction of two signals of comparable magnitude. Ten enamel samples were irradiated with known doses in the range of 250–105 mGy. There was agreement for all the samples, within the typical experimental error of ±10% for EPR dosimetry in dental enamel, between the doses determined by two common techniques using native signal subtraction and the doses determined by the new second derivative method proposed here. 相似文献
10.
Argon laser irradiation can be used to cure orthodontic brackets onto teeth in significantly less time than conventional curing lights. In addition, it has been shown that the argon laser seems to impart a demineralization resistance to the enamel. The purpose of this study was to use surface science techniques to ascertain if this demineralization resistance is possibly a result of a decrease in the carbonate content of enamel. Eleven mandibular third molars previously scheduled for extraction were collected and used in the present study. The teeth were sectioned in two and randomly assigned to either the argon laser (457-502 nm; 250 mW cm−2) or the control (no treatment) group. The sections assigned to the argon laser group were cured for 10 s and analyzed. To exaggerate any potential changes the experimental sections were then exposed to a further 110 s of argon laser irradiation. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results showed no statistically significant change in the carbonate content of enamel after argon laser irradiation (p > 0.05). Thus, it is suggested that any demineralization resistance imparted to the enamel surface by argon laser irradiation is not due to alterations in carbonate content. 相似文献
11.
Nabil El-Faramawy Reham Ameen Khaled El-Haddad Ahmed Maghraby Medhat El-Zainy 《辐射效应与固体损伤》2013,168(12):927-934
In the present study, 40 adult male albino rats were used to study the effect of gamma radiation on the hard dental tissues (enamel surface, dentinal tubules and the cementum surface). The rats were irradiated at 0.2, 0.5, 1.0, 2.0, 4.0 and 6.0 Gy gamma doses. The effects of irradiated hard dental tissues samples were investigated using a scanning electron microscope. For doses up to 0.5 Gy, there was no evidence of the existence of cracks on the enamel surface. With 1 Gy irradiation dose, cracks were clearly observed with localized erosive areas. At 2 Gy irradiation dose, the enamel showed morphological alterations as disturbed prismatic and interprismatic areas. An increase in dentinal tubules diameter and a contemporary inter-tubular dentine volume decrease were observed with higher irradiation dose. Concerning cementum, low doses,<0.5 Gy, showed surface irregularities and with increase in the irradiation dose to≥1 Gy, noticeable surface irregularities and erosive areas with decrease in Sharpey's fiber sites were observed. These observations could shed light on the hazardous effects of irradiation fields to the functioning of the human teeth. 相似文献
12.
M. A. S. Melo D. M. de-Paula J. P. M. Lima F. M. C. Borges C. Steiner-Oliveira M. Nobre-dos-Santos I. C. J. Zanin E. B. Barros L. K. A. Rodrigues 《Laser Physics》2010,20(6):1504-1513
The development of a method to ensure bacterial-free substrates without extensive cavity preparation would be highly useful
to dentistry, since there is no currently available effective method for killing residual bacteria in dentinal tissue. This
randomized in vitro study determined parameters for using toluidine blue O (TBO) with a light-emitting diode (LED) for dentine
caries disinfection and monitored intrapulpal/periodontal temperatures during irradiation. Occlusal human dentine slabs were
immersed in Streptococcus mutans culture for demineralization induction. Slabs were allocated to 10 groups (n = 15), which were treated with 0.1 mg ml−1 TBO with 5 min of incubation time or 0.9% NaCl solution for 5, 10 or 15 min, and submitted or not to irradiation for 5, 10
or 15 min (47, 94, and 144 J/cm2). Before and after treatments, dentine samples were analyzed with regard to S. mutans counts. In whole teeth, temperature in pulp and periodontium was measured by thermocouples during irradiation. Kruskal-Wallis/Student-Newman-Keuls,
and ANOVA/Tukey test were respectively utilized to compare log reductions and temperature rises between groups. Bacterial
reduction was observed when dentine was exposed to both TBO and LED at all irradiation times, as well as to LED alone for
10 and 15 min. Temperature increases lower than 2°C were observed for either pulp or periodontium. Concluding, LED combined
with TBO is a safe and effective approach for dentine caries disinfection. Nevertheless, additional studies should be conducted
to determine the influence of the irradiation in S. mutans viability in dentinal surface/tubules. 相似文献
13.
14.
R. J. Jeon A. Matvienko A. Mandelis S. H. Abrams B. T. Amaechi G. Kulkarni 《The European physical journal. Special topics》2008,153(1):467-469
Frequency-domain photothermal radiometry (FD-PTR or PTR)
has been used to detect mechanical holes and demineralized enamel in the
interproximal contact area of extracted human teeth. Thirty four teeth were
used in a series of experiments. Preliminary tests to detect mechanical
holes created by dental burs and 37% phosphoric acid etching for 20 s on
the interproximal contact points showed distinct differences in the signal.
Interproximal contact areas were demineralized by using a partially
saturated acidic buffer system. Each sample pair was examined with PTR
before and after micro-machining or treating at sequential treatment periods
spanning 6 hours to 30 days. Dental bitewing radio graphs showed no sign of
demineralized lesion even for samples treated for 30 days. μ-CT, TMR and SEM
analyses were performed. Although μ-CT and TMR measured mineral losses and
lesion depths, only SEM surface images showed visible signs of treatment
because of the minimal extent of the demineralization. However, the PTR
amplitude increased by more than 300% after 80 hours of treatment.
Therefore, PTR has been shown to have sufficient contrast for the detection
of very early interproximal demineralized lesions. The technique further
exhibited excellent signal reproducibility and consistent signal changes in
the presence of interproximal demineralized lesions, attributes which render
PTR a reliable probe to detect early interproximal demineralization lesions.
Modulated luminescence was also measured simultaneously, but it showed a
lower ability to detect these interproximal demineralized lesions than PTR. 相似文献
15.
In the present study, a novel blue light source from LED was used to activate hypocrellin B in ovarian cancer HO-8910 cells.
Hypporellin B concentration was kept at 2.5 μM and light doses from 0.5–4.0 J/cm2. Photocytotoxicity was investigated using MTT reduction assay and light microscopy after light irradiation. Cellular morphology
was observed using transmission electron microscopy (TEM). MTT assay showed that the cytotoxicity of blue light-activated
hypocrellin B in HO-8910 cells increased along with light dose. The observations from light microscopy reinforced the above
results. TEM showed that microvillin disappearance, vacuole formation, chromatin condensation, and topical apoptotic body
were observed in the cells treated by both light and hypocrellin B. The findings demonstrated that blue light from LED source
could effectively activate hypocrellin B to cause the destruction of HO-8910 cells, indicating that Blue light-activated hypocrellin
B might be potential therapeutic strategy in the management of ovarian cancer. 相似文献
16.
M.?R.?Galv?o S.?X.?S.?Costa K.?R.?Victorino A.?A.?Ribeiro F.?C.?H.?Menezes A.?N.?S.?Rastelli V.?S.?Bagnato M.?F.?Andrade 《Laser Physics》2010,20(12):2050-2055
The aim of this study was to evaluate the degree of conversion and hardness of a dental composite resin Filtek™ Z-350 (3M
ESPE, Dental Products St. Paul, MN) photo-activated for 20 s of irradiation time with two different light guide tips, metal
and polymer, coupled on blue LED Ultraled LCU (Dabi Atlante, SP, Brazil). With the metal light tip, power density was of 352
and with the polymer was of 456 mW/cm2, respectively. Five samples (4 mm in diameter and 2mm in thickness—ISO 4049), were made for each Group evaluated. The measurements
for DC (%) were made in a Nexus-470 FT-IR, Thermo Nicolet, E.U.A. Spectroscopy (FTIR). Spectra for both uncured and cured
samples were analyzed using an accessory of reflectance diffuse. The measurements were recorded in absorbance operating under
the following conditions: 32 scans, 4 cm−1 resolution, 300–4000 cm−1 wavelength. The percentage of unreacted carbon double bonds (% C=C) was determined from the ratio of absorbance intensities
of aliphatic C=C (peak at 1637 cm−1) against internal standard before and after curing of the sample: aromatic C-C (peak at 1610 cm−1). The Vickers hardness measurements (top and bottom surfaces) were performed in a universal testing machine (Buehler MMT-3
digital microhardness tester Lake Bluff, Illinois USA). A 50 gf load was used and the indenter with a dwell time of 30 s.
The data were submitted to the test t Student at significance level of 5%. The mean values of degree of conversion for the polymer and metal light guide tip no were statistically
different (p = 0.8389). The hardness mean values were no statistically significant different among the light guide tips (p = 0.6244), however, there was difference between top and bottom surfaces (p < 0.001). The results show that so much the polymer light tip as the metal light tip can be used for the photo-activation,
probably for the low quality of the light guide tip metal. 相似文献
17.
Changqi Xu Kunal Karan Xiaomei Yao Yong Wang 《Journal of Raman spectroscopy : JRS》2009,40(12):1780-1785
Molecular structure of the sclerotic dentin in noncarious cervical lesions (NCCLs) including both the inorganic phase and organic phase was investigated using Raman spectroscopy. It was found that NCCL sclerotic dentin was hypermineralized with the mineral/matrix ratios 2–3 times higher than those of normal dentin, which was caused by both the increase of mineral content and decrease of organic matrix (collagen) content in the sclerotic dentin. For the inorganic phase, the phosphate band (PO43−, ν1, symmetric stretching vibrational mode) in NCCL sclerotic dentin was shifted from 960 to 963 cm−1, and the width of this band was decreased from 16.4 to 10.4 cm−1, indicating that the degree of mineral crystallinity in NCCL sclerotic dentin was higher than that of normal dentin. In addition, the carbonate content in the mineral of NCCL sclerotic dentin was less than that of normal dentin. As compared to the inorganic phase, the changes within the organic phase were not dramatic. However, the changes in collagen cross‐link density along with other spectral changes were still detectable. There was a noteworthy reduction in the ratio of nonreducible to reducible cross‐links in the NCCL sclerotic dentin, indicating that cross‐link breaks occurred in the collagen matrix of the lesions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
18.
《Radiation measurements》2007,42(6-7):1256-1260
This paper briefly reviews the optically stimulated luminescence (OSL) properties of dental enamel and discusses the potential and challenges of OSL for filling the technology gap in biodosimetry required for medical triage following a radiological/nuclear accident or terrorist event. The OSL technique uses light to stimulate a radiation-induced luminescence signal from materials previously exposed to ionizing radiation. This luminescence originates from radiation-induced defects in insulating crystals and is proportional to the absorbed dose of ionizing radiation. In our research conducted to date, we focused on fundamental investigations of the OSL properties of dental enamel using extracted teeth and tabletop OSL readers. The objective was to obtain information to support the development of the necessary instrumentation for retrospective dosimetry using dental enamel in laboratory, or for in situ and non-invasive accident dosimetry using dental enamel in emergency triage. An OSL signal from human dental enamel was detected using blue, green, or IR stimulation. Blue/green stimulation associated with UV emission detection seems to be the most appropriate combination in the sense that there is no signal from un-irradiated samples and the shape of the OSL decay is clear. Improvements in the minimum detection level were achieved by incorporating an ellipsoidal mirror in the OSL system to maximize light collection. Other possibilities to improve the sensitivity and research steps necessary to establish the feasibility of the technique for retrospective assessment of radiation exposure are also discussed. 相似文献
19.
N. Yagi N. Ohta T. Matsuo T. Tanaka Y. Terada H. Kamasaka K. To‐o T. Kometani T. Kuriki 《Journal of synchrotron radiation》2009,16(3):398-404
Early caries lesion is a demineralization process that takes place in the top 0.1 mm layer of tooth enamel. In this study, X‐ray microbeam diffraction was used to evaluate the hydroxyapatite crystallites in the subsurface lesion of a bovine enamel section and the results are compared with those obtained by transversal microradiography, a method commonly used for evaluation of tooth mineral. Synchrotron radiation from SPring‐8 was used to obtain a microbeam with a diameter of 6 µm. Wide‐angle X‐ray diffraction reports the amount of hydroxyapatite crystals, and small‐angle X‐ray scattering reports that of voids in crystallites. All three methods showed a marked decrease in the enamel density in the subsurface region after demineralization. As these diffraction methods provide structural information in the nanometre range, they are useful for investigating the mechanism of the mineral loss in early caries lesion at a nanometre level. 相似文献
20.
Summary A new method of dental fluorine prophylaxis based on the chemical reaction induced by UV irradiation in dental enamel has
been presented. Fluorine ions from a gel topic can be retained to the dental apatite in the lamp-irradiated samples at about
70% and in the laser-irradiated samples at about 80% of the maximum deposited value. The19F(p,α)16O nuclear reaction was used to measure the fluorine concentrations in the first 3 μm of the enamel of healthy teeth before
and after the gel topic applications with and without UV irradiation. This method of dental prefenction resolves the problem
of the traditional fluorine prophylaxis which brings fluorine in the enamel without binding the apatite.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献