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1.
A 405-nm diode laser has recently been developed for soft tissue problems in dentistry. A new in-office bleaching agent consisting of a titanium dioxide photocatalyst and 3.5% hydrogen peroxide has proven to react well with light irradiated at a wavelength of around 400 nm. In this study, we evaluated the bleaching efficacy of a newly developed 405-nm diode laser on bovine teeth treated with a bleaching agent composed of titanium dioxide and 3.5% hydrogen peroxide. Sixteen bovine incisors were randomly divided into two groups: Group A, irradiated by the 405-nm diode laser at 200 mW; Group B, irradiated by the 405-nm diode laser at 400 mW. The bleaching agent with titanium dioxide and 3.5% hydrogen peroxide was applied to bovine enamel and irradiated for 1 min. The specimens were then washed and dried, and the same procedure was repeated nine more times. After irradiation, we assessed the effects of bleaching on the enamel by measuring the color of the specimens with a spectrophotometer and examining the enamel surfaces with a scanning electron microscope. L* rose to a high score, reaching a significantly higher post-treatment level in comparison to pretreatment. In a comparison of the color difference (ΔE) between Group A and Group B, the specimens in Group B showed significantly higher values after 10 min of irradiation for the post-treatment. No remarkable differences in the enamel surface morphology were found between the unbleached and bleached enamel. The use of a 405-nm diode laser in combination with a bleaching agent of titanium dioxide and 3.5% hydrogen peroxide may be an effective method for bleaching teeth without the risk of tooth damage. 相似文献
2.
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
3.
J. F. Kina P. C. Benitez R. F. Z. Lizarelli V. S. Bagnato T. C. Martinez C. F. Oliveira J. Hebling C. A. S. Costa 《Laser Physics》2008,18(12):1562-1569
The purpose of this study was to comparatively evaluate the response of human pulps after cavity preparation with different devices. Deep class I cavities were prepared in sound mandibular premolars using either a high-speed air-turbine handpiece (Group 1) or an Er:YAG laser (Group 2). Following total acid etching and the application of an adhesive system, all cavities were restored with composite resin. Fifteen days after the clinical procedure, the teeth were extracted and processed for analysis under optical microscopy. In Group 1 in which the average for the remaining dentin thickness (RDT) between the cavity floor and the coronal pulp was 909.5 μm, a discrete inflammatory response occurred in only one specimen with an RDT of 214 μm. However, tissue disorganization occurred in most specimens. In Group 2 (average RDT = 935.2 μm), the discrete inflammatory pulp response was observed in only one specimen (average RDT = 413 μm). It may be concluded that the high-speed air-turbine handpiece caused greater structural alterations in the pulp, although without inducing inflammatory processes. 相似文献
4.
Liu JM Gao F Gao WY Zeng LQ Huang XM Li ZM Huang XC Lin WN Wang FM Nie CL 《Journal of fluorescence》2008,18(2):573-579
When 1.00 mol l−1 I− is used as ion perturber, rhodamine 6G (Rh 6G) can emit strong and stable room temperature phosphorescence (RTP) on filter
paper substrate in KHC8H4O4–HCl buffer solution (pH = 3.50), heated at 70 °C for 10 min. NaIO4 can oxidize Rh 6G, which makes the RTP signal quench. Terbutaline sulfate (TBS) can inhibit NaIO4 from oxidizing Rh 6G, which makes the RTP signal of Rh 6G enhance sharply. The content of TBS is linear correlation to ΔIp of the system. Based on the facts above, a new inhibition solid substrate-room temperature phosphorimetry (SS-RTP) for the
determination of trace TBS has been established. The linear range of this method is 0.0104–2.08 pg spot−1 (corresponding concentration: 0.026–5.2 ng ml−1, with a sample volume of 0.4 μl) with a detection limit (L.D.) of 2.6 fg spot−1 (corresponding concentration: 6.5 × 10−12 g ml−1), and the regression equation of working curve is ΔIp = 2.040 + 54.54 mTBS (pg spot−1), n = 6, correlation coefficient is 0.9994. For the samples containing 0.0104 pg spot−1 and 2.08 pg spot−1 TBS, the relative standard deviation (RSD) are 3.8% and 2.3% (n = 8), respectively, indicating good precision. This method has been applied to determination of trace TBS in the practical
samples with satisfactory results. The reaction mechanism of NaIO4 oxidizing Rh 6G to inhibit SS-RTP for the determination of trace TBS is also discussed. 相似文献
5.
P. Kammel V. A. Andreev D. V. Balin R. M. Carey T. Case D. B. Chitwood S. M. Clayton K. M. Crowe J. Deutsch P. T. Debevec P. U. Dick A. Dijksman J. Egger D. Fahrni A. A. Fetisov S. J. Freedman V. A. Ganzha B. Gartner J. Govaerts F. E. Gray F. J. Hartmann W. D. Herold D. W. Hertzog V. I. Jatsoura A. G. Krivshich B. Lauss E. M. Maev O. E. Maev V. E. Markushin C. J. G. Onderwater C. Petitjean G. E. Petrov C. C. Polly R. Prieels S. M. Sadetsky G. N. Schapkin R. Schmidt G. G. Semenchuk M. Soroka A. A. Vorobyov N. I. Voropaev 《Hyperfine Interactions》2001,138(1-4):435-443
The aim of the μCap experiment is a 1% measurement of the singlet capture rate Λ
S
for the basic electro-weak reaction μ + p → n + νμ. This observable is sensitive to the weak form-factors of the nucleon, in particular to the induced pseudoscalar coupling
constant g
P
. It will provide a rigorous test of theoretical predictions based on the Standard Model and effective theories of QCD. The
present method is based on high precision lifetime measurements of μ− in hydrogen gas and the comparison with the free μ+ lifetime. The μ− experiment will be performed in ultra-clean, deuterium-depleted H2 gas at 10 bar. Low density compared to liquid H2 is chosen to avoid uncertainties due to ppμ formation. A time projection chamber acts as a pure hydrogen active target. It defines the muon stop position in 3D and
detects rare background reactions. Decay electrons are tracked in cylindrical wire-chambers and a scintillator array covering
75% of 4π.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Four-photon polarization spectra of double distilled water subjected to a special treatment in a cavitation chamber and 20%
aqueous solution of hydrogen peroxide were recorded in the range ±8 cm−1. All recorded spectra contain narrow (< 0.3 cm−1) resonances corresponding to the frequencies of the rotational spectrum of ortho and para spin isomers of the H2O molecule. Numerical simulation of the spectra obtained made it possible to quantitatively estimate the contribution of the
rotational spectrum to the coherent scattering signal. It was found that the contribution of the para spin isomer of the H2O molecule to the rotational line spectrum decreases in an aqueous solution of the α-chymotrypsin protein. Apparently, this decrease indicates the selectivity of interaction of biopolymer molecules with different
spin isomers. 相似文献
7.
E. M. Maev V. A. Andreev T. A. Case K. M. Crowe P. U. Dick A. Dijksman J. Egger D. Fahrni A. A. Fetisov V. A. Ganzha F. J. Hartmann P. Kammel A. G. Krivchitch O. E. Maev C. Petitjean G. E. Petrov R. Prieels S. M. Sadetsky G. N. Schapkin R. Schmidt G. G. Semenchuk M. Soroka A. A. Vorobyov N. I. Voropaev 《Hyperfine Interactions》2001,138(1-4):451-457
A new experiment is under preparation with the aim to improve considerably the present knowledge of the rate Λ
s
, which should be measured on a level of 1% or better, for the basic electroweak capture reaction of a negative muon on the
free proton μp
1s
→ n + νμ. The capture rate will be determined by measuring the lifetime of μ− stopped in ultra pure hydrogen at 10 bar pressure and comparing it with the lifetime of the unbound μ+. A new experimental method was developed for this project which should allow measuring the μ− lifetime with at least 10 ppm precision. The basic element of the detector is operating in the hydrogen gas time projection
chamber (TPC) surrounded by multi-wire proportional chambers (MWPCs) and scintillator counters. The arrival times and trajectories
of the incoming muons and the outgoing decay electrons are measured with this device providing effective suppression of background.
Using the TPC as an active target, we can monitor on-line the protium contamination by impurities with a sensitivity better
than 10−8. This can be done by detecting the charged products of the muon capture reaction on these impurities. It was demonstrated
that the TPC and MWPCs can operate in pure hydrogen under 10 bar pressure providing gas gain up to 10 000.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
F. Monteverde 《Applied Physics A: Materials Science & Processing》2006,82(2):329-337
A fully dense ZrB2 ceramic containing 10 vol. % ultra-fine α-SiC particulate was successfully hot pressed at 1900 °C for 20 min and 40–50 MPa
of applied pressure. Faceted ZrB2 grains (average size ≈3 μm) and SiC particles dispersed regularly characterized the base material. No extra secondary phases
were found. The introduction of the ultra-fine α-SiC particulate was recognized as the key factor that enabled both the control
of the diboride grain growth and the achievement of full density. The mechanical properties offered an interesting combination
of data: 4.8±0.2 MPafracture toughness, 507±4 GPa Young’s modulus, 0.12 Poisson’sratio, and 835±35 MPa flexural strength at room temperature.
The flexural strength measured at 1500 °C (in air) provided values of 300±35 MPa. The incorporated ultra-fine α-SiC particulate
was fundamental, sinterability apart, to enhancing the strength and oxidation resistance of ZrB2. The latter property was tested at 1450 °C for 20 h in flowing dry air. In such oxidizing conditions, the formation of a
thin external borosilicate glassy coating supplied partial protection for the faces of the material exposed to the hot environment.
The oxidation attack penetrated into the material’s bulk and created a 200-μm-thick zirconia scale. The SiC particulate included
in the oxide scale, lost by active oxidation, left carbon-based inclusions in the formerly occupied sites.
PACS 81.05.Je; 81.20.Ev; 81.70.Bt 相似文献
9.
C. Petitjean 《Hyperfine Interactions》2001,138(1-4):191-201
During 25 years pioneering μCF experiments were performed at PSI. After initial study of the Wolfenstein–Gershtein effect
in H/D, an intense research program on dμd fusion led to the early discovery of resonant dμd formation at low temperature and to the first direct observation of μd spin flip. With the Gatchina ionisation chamber absolute precisions of ∼1% on the determination of dμd formation and spin flip rates were recently obtained in good agreement with the theory.
In a very large effort the highly resonant dμt fusion cycle was investigated. Record cycle rates up to 2×108 s−1 and yields up to 124 fusions per muon were measured. By slope analysis and by direct observation, effective sticking ω
s
= (0.505 ± 0.029)% is the final PSI result. Clear experimental evidence of large epithermal resonances in D/T and H/D/T mixtures
was found.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
R. Pohl F. Biraben C.A.N. Conde C. Donche Gay T.W. Hänsch F.J. Hartmann P. Hauser V.W. Hughes O. Huot P. Indelicato P. Knowles F. Kottmann Y. W. Liu F. Mulhauser F. Nez C. Petitjean P. Rabinowitz J.M.F. dos Santos L.A. Schaller H. Schneuwly W. Schott L.M. Simons D. Taqqu F. Trehin J.F.C.A. Veloso 《Hyperfine Interactions》2000,127(1-4):161-166
The contribution of the root mean square (RMS) proton charge radius to the Lamb shift (2S–2P energy difference) in muonic
hydrogen (μp) amounts to 2%. Apart from the uncertainty on this charge radius, theory predicts the Lamb shift with a precision
on the ppm level. We are going to measure ΔE (2 S1/2(F=1)–2 P3/2(F=2)) in a laser resonance experiment to a precision of 30 ppm (i.e., 10% of the natural linewidth) and to deduce the RMS
proton charge radius with 10−3 relative accuracy, 20 times more precise than presently known.
The most important requirement for the feasibility of such an experiment, namely the availability of a sufficient amount of
long lived metastable μp atoms in the 2S state, has been investigated in a recent experiment at PSI. Our analysis shows that
in the order of one percent of all muons stopped in low pressure hydrogen gas form a long lived μp(2S) with a lifetime of
the order of 1 μs.
The technical realization of our experiment involves a new high intensity low energy muon beam, an efficient low energy muon
entrance detector, a randomly triggered 3 stage laser system providing the 0.5 mJ, 7 ns laser pulses at 6.02 μm wavelength,
and a combination of a xenon gas proportional scintillation chamber (GPSC) and a microstrip gas chamber (MSGC) with a CsI
coated surface to detect the 2 keV X rays from theμp(2P → 1S) transition.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
E. M. A. Clavijo V. R. G. Clavijo M. C. Bandéca M. R. Nadalin M. F. Andrade J. R. C. Saad A. A. Pelegrine 《Laser Physics》2009,19(10):2041-2044
Dentin hipersensitivity (DH) is a relatively common clinical condition, especially in periodontal patients after treatment.
In this study it was evaluated 28 teeth who presented dentin hypersensitivity. The teeth were subjected to clinical and radiographic
exams and were divided into groups following the treatment and the time of examination after application proposed: GI: PO
3% (Potassium Oxalate—group control)/Baseline; GII: PO 3%/3 days after first session; GIII: PO 3%/6 days; GIV: PO 3%/30 days;
GV: PO 3%/60 days; GVI: PO 3%/90 days; GVII: Laser (Low_level diode laser with 110 mW/cm2)/Baseline; GVIII: Laser/7 days after first session; GIX: Laser/14 days; GX: Laser/30 days; GXI: Laser/60 days; and GXII:
Laser/90 days. The groups I–VI, the teeth were subjected to 3 applications (GI–GIII) of desensitizing agent at regular intervals
of seven days. The Groups VII–XI, each tooth was subjected to three applications (GVII–GIX) in three different points (mesial,
meddle and distal surfaces) with an interval of 72 h. The time of application in each point was of 33 s and the patients from
both groups were followed up to 90 days. The nonparametric test Friedman (α = 0.05) was applied and the test of Mann Whitney
(α = 0.05) was used to compare the time of examination between groups. The application of Laser was effective 6 days after
first session and to PO was 30 days. It was observed that both treatments were effective for the reduction of dentin hypersensitivity,
however the laser presented better effectiveness. 相似文献
12.
Past trials with soft and calcified tissues have demonstrated that long pulse train (2.5 mus) Er:YAG (2.94 mum) laser may be used to ablate tooth structure of human teeth. Determination of physical and thermal damage to surrounding tissue during removal of enamel and dentin is a primary objective of this study. Extracted human teeth with thermal probes imbedded in the pulp chambers were submitted to cavity preparation using an Erbium YAG laser with water mist. Wavelength selection as well as use of a water mist during the procedure resulted in efficient tissue removal without significant surrounding damage. Ground sections and SEM sections of teeth showed little or no melting or ash formation in adjacent dentin and enamel and no visible change in the pulp chamber. The surfaces produced by laser ablation were rough and irregular with craters and grooves. Average temperature change in the pulp chamber monitored during tooth preparation was 2.2 degrees Centigrade. These findings suggest that constantly available water aids vaporization and microexplosions, increasing the efficiency of tooth structure removal, and aids in cooling of the tooth structures. The long pulse Er:YAG (2.94 mum) laser may be an effective method for tooth reduction applications when used with a water mist. 相似文献
13.
《The European Physical Journal C - Particles and Fields》2005,39(3):331-337
We have reconstructed 695 three-track τ decay vertices using a high resolution drift chamber close to the interaction point.
From the distribution of decay lengths we measure the lifetime to be (3.06 ±0.20±0.14)×10−13 s. Using this result we find that the ratio of charged weak coupling constant for the τ to that of the μ,G
τ/G
μ=0.967±0.040 consistent with the concept of lepton universality.
On leave from Warsaw University, Poland
Now at Hasylab, DESY
Supported by Bundesministerium für Forschung und Technologie
Supported by UK Science and Engineering Research Council
Supported by CAICYT
Supported by the Minerva Gesellschaft für Forschung GmbH
Supported by US Dept. of Energy, contract DE-AC02-76ER000881 and by US Nat. Sci. Foundation Grant no INT-8313994 for travel
Partially supported by grant CPBP 01.06 相似文献
14.
Jianfeng Ping Xiuling Mao Kai Fan Dongyang Li Shiping Ru Jian Wu Yibin Ying 《Ionics》2010,16(6):523-527
A highly selective, sensitive, fast, and stable amperometric sensor for the determination of hydrogen peroxide residues in
aseptic milk is presented. To fabricate this amperometric sensor, a thin film of Prussian blue was first electrodeposited
on a glassy carbon electrode and then a Nafion polymer layer was formed on the top. It was found that Nafion film greatly
improves the anti-interference ability and the stability of the Prussian blue-modified electrode. Factors that influence the
overall analytical performance of the sensor, such as the concentration of Nafion drop and pH value of the electrolyte, were
examined. Results show that the prepared sensor possesses efficient electrocatalytic activity towards hydrogen peroxide with
the detection limit as low as 0.2 μM and linear range from 0.8 μM to 0.12 mM. The developed sensor was applied to the determination
of hydrogen peroxide in milk with satisfactory results. 相似文献
15.
The purpose of this study was to investigate the optical properties, absorption coefficient (μ
a
) scattering coefficient (μ
s
) and refractive indices, (n) of HeLa cell line in a suspension of 2% minimum essential medium (MEM) at two different (632.8 and 532.0 nm) wave lengths
of laser light. Optical properties were determined with Kubelka Munk Model (KMM) and refractive index measurement was made
through minimum angle of deviation method (MAD). We reported μ
a
= 8.643 ± 0.187 and 2.348 ± 0.249 cm−1 and μ
s
= 5.609 ± 0.287 and 88.166 ± 2.833 cm−1 at 632.8 and 532.0 nm, respectively. Refractive index was found to be 1.332 and 1.312 at 632.8 nm and 532.0 nm, respectively.
The discussed results provide a route of information for clinical diagnosis, therapeutic application and dosimetry studies
in HeLa and other cell lines. 相似文献
16.
B. M. Forster J. M. Bailey G. A. Beer J. L. Beveridge J. H. Brewer W. N. Hardy T. M. Huber K. R. Kendall A. R. Kunselman J. A. Macdonald G. M. Marshall G. R. Mason A. Olin M. Senba J. B. Warren 《Hyperfine Interactions》1991,65(1-4):1007-1013
Muonic hydrogen isotopes (μ− p, μ− d, and μ−t) are simple quantum mechanical systems ideally suited for studies of numerous fundamental phenomena in electroweak and strong
interactions as well as in applied areas such as muon chemistry or muon catalyzed fusion.
Emission of muonic hydrogen isotopes into vacuum helps to overcome the limitations which are normally imposed on conventional
investigations with gaseous and liquid targets. A proof of principle experiment for this new technique was performed at TRIUMF
last year. Negative muons with 30 MeV/c momentum were stopped in a thin film of solid hydrogen and produced very low energy μ−d in vacuum. The distribution center of the normal velocity components of emitted μ−d atoms was measured to be ∼1 cm/μs. The yield of μ−d in vacuum is an increasing function of H2 film thickness δ up to a value of δ≥1 mm. 相似文献
17.
Ribbon-form Sendust was prepared by a roll quenching method. The size of the ribbon was 20∼110 μm thick, 2∼8 mm wide and 5∼10
m long. The normal direction of the ribbon plane was parallel to the [100] as well as the [110] axes, and no preferential
directions exist within the ribbon plane. Vickers hardnessH
v
of the as-prepared ribbon was 563±7, decreased with increasing the annealing time and became almost constant. The minimum
bending diameter of the as-prepared ribbon was 8 mm and increased gradually with increase of the annealing time. Initial permeability
of the 84.80 Fe·9.50 Si·5.70 Al ribbon was about 34,000 in the frequency range from 1 to 3kHz and decreased to be 10,000 at
85 kHz. The permeability of the molded core in a resin was about 21,000 in the frequency range from 1 to 3 kHz. 相似文献
18.
R. Pohl H. Daniel F. J. Hartmann P. Hauser Y. W. Liu F. Kottmann C. Maierl V. E. Markushin M. Mühlbauer C. Petitjean W. Schott D. Taqqu 《Hyperfine Interactions》2001,138(1-4):35-40
Kinetic energy distributions of muonic hydrogen atoms μp(1S) have been obtained by means of a time-of-flight technique for
hydrogen gas pressures between 4 and 64 hPa. A high energy component of ∼900 eV observed in the data is interpreted as the
signature of long-lived μp(2S) atoms, which are quenched in a non-radiative process leading to the observed high energy: the
collision of a thermalized μp(2S) atom with a hydrogen molecule H2 results in the resonant formation of a {[(ppμ)+]*pee}* molecule. Then the (ppμ)+ complex undergoes Coulomb de-excitation and the ∼1.9 keV excitation energy is shared between a μp(1S) atom and one proton.
The preliminary analysis of the time spectra gives a long-lived μp(2S) population of ∼1% of all stopped muons, and a quenching
rate of ∼4⋅1011 s−1.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
T. N. Mamedov V. G. Grebinnik K. I. Gritsai V. N. Duginov V. A. Zhukov V. G. Ol’shevskii A. V. Stoikov 《JETP Letters》1999,69(3):192-195
The lifetimes of a negative muon in the isotopes 132Xe and 40Ar in the solid phase are measured. The lifetime of μ
− in the 1s state of the isotope 132Xe is τ(132Xe)=101.7±1.7 ns, which corresponds to a total nuclear capture rate Λc(132Xe)=9.4±0.2 μs−1. The lifetime of μ
− in the isotope 40Ar, viz., τ (40Ar)=568±6 ns, corresponding to a capture rate Λc(40Ar)=1.31±0.01 μs−1, is obtained to several times better accuracy as compared to previously published results.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 3, 181–183 (10 February 1999) 相似文献
20.
The experimental results of a high-power tunable mid-IR laser are presented. The optical parametric oscillator (OPO) with
a 3-mm-thick PPMgCLN crystal was pumped by a 1.064 μm pulse laser. When the pump power of the 1.064 μm laser was 151 W at
10 kHz, and the operating temperature of the PPMgCLN with 5% MgO doping was 100°C, average output power of 23.7 W at 3.91
μm was obtained with a slope efficiency of 18.2% for the idler resonant OPO. The variation of the 3.91 μm output power was
about ±4% in 10 min continuous operation. The beam quality factor M
2 was less than 2.6. The average output power of 27.4 W at 3.91 μm was also obtained with 151 W pump power and the slope efficiency
of 20.9% for the signal resonant OPO by changing the coating parameters of the OPO cavity mirrors. The mid-IR wavelength tunability
of 3.7–4.0 μm can be achieved by adjusting the temperature of a 29 μm period PPMgCLN crystal from 200 to 30°C. 相似文献