Comparisons between Bio-Oss® and Straumann® Bone Ceramic in immediate and staged implant placement in dogs mandible bone defects

Objective: To compare immediate and staged approach implant placement in circumferential defects treated with deproteinized bovine bone mineral (DBBM); hidroxyapatite/tricalcium phosphate (HA/TP); autogenous bone (Ab); and coagulum (Cg); upon implant stability, osseointegration and alveolar crest maintenance. Materials and methods: Six dogs underwent extractions of lower premolars, bilaterally. Twelve weeks later four bone defects (6 mm wide/4 mm long) were drilled at one side and randomly filled with DBBM; HA/TP; Ab; and Cg, respectively, and left to heal (staged approach). Eight weeks later one implant (Osseospeed™, AstraTech) was placed in experimental sites. At the same session four defects were drilled on contra-lateral side and implants were inserted immediately after biomaterials grafting (immediate approach). Animals were euthanized 8 weeks later. Implant stability was measured by resonance frequency analysis (RFA) at installation and after sacrifice. Ground sections were prepared for bone contact (BIC); bone area (BA); distance implant shoulder-bone crest (IS-C); distance implant shoulder first bone contact (IS-B); and areas occupied by soft tissue. Results: The BA and BIC were superior in the staged approach. The Cg exhibited higher BIC and BA as compared with other materials at the total implant body (P = 0.004 and 0.012, respectively). The DBBM, HA/TP and Ab groups rendered similar BA and BIC. The immediate approach resulted in less crest resorption compared to staged approach. The biomaterials did not affect the IS-C and IS-B measurements. Particles area tended to be higher in DBBM group than HA/TP (P = 0.15), while soft tissue infiltrate was higher in DBBM group when used in the immediate approach (P = 0.04). The RFA indicated gain in stability in the staged approach (P = 0.002). The correlation test between RFA vs. BIC and BA demonstrated inferior stability for DBBM group in immediate approach (P = 0.01). Conclusions: Implants placed in healed defects resulted in better stability as a consequence of higher BIC and BA. The Cg alone rendered increased BIC compared to other materials in both approaches. Immediate approach should be preferable to staged approach in terms of alveolar crest maintenance. The BIC and BA values did not vary between micro and macro-threads in this experimental model. Implants installed in sites filled with DBBM in immediate approach were less stable. © 2011 John Wiley & Sons A/S.

Dinâmica não linear de sistemas de levitação magnética

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caos e controle de microviga em balanço de um microscópio de força atômica, operando em modo intermitente, na ressonância

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Osseointegração de implantes usinados e oxidados em seio maxilar preenchido por coágulo com ou sem osso autógeno: estudo histológico, histométrico e de RFA em macacos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação clínica e da freqüência de ressonância, de implantes instalados por meio de técnica cirúrgica modificada na maxila e submetidos à função imediata

Pós-graduação em Odontologia - FOA

On the Performance of a Two-Stage Vibration Isolation System Which has Geometrically Nonlinear Stiffness

Linear single-stage vibration isolation systems have a limitation on their performance, which can be overcome passively by using linear two-stage isolations systems. It has been demonstrated by several researchers that linear single-stage isolation systems can be improved upon by using nonlinear stiffness elements, especially for low-frequency vibrations. In this paper, an investigation is conducted into whether the same improvements can be made to a linear two-stage isolation system using the same methodology for both force and base excitation. The benefits of incorporating geometric stiffness nonlinearity in both upper and lower stages are studied. It is found that there are beneficial effects of using nonlinearity in the stiffness in both stages for both types of excitation. Further, it is found that this nonlinearity causes the transmissibility at the lower resonance frequency to bend to the right, but the transmissibility at the higher resonance frequency is not affected in the same way. Generally, it is found that a nonlinear two-stage system has superior isolation performance compared to that of a linear two-stage isolator.

Early loading of 6-mm-short implants with a moderately rough surface supporting single crowns: a prospective 5-year cohort study

AimTo evaluate prospectively the clinical and radiographic outcomes after 5years of early loading of 6-mm implants with a moderately rough (SLActive((R))) surface supporting single crowns in the posterior regions.Material and methodsThirty-five consecutive patients received 40 SLActive((R)) (Straumann) 6-mm implants with a diameter of 4.1mm (n=19) or 4.8mm (n=21). Insertion torque and resonance frequency analysis (RFA) were measured at implant installation. RFA was also measured at abutment connection. SynOcta abutments were tightened with 35Ncm after 6weeks of healing, and single porcelain fuse to metal crowns was cemented within 1week. Implant survival rate and marginal bone loss were evaluated at various time intervals until 5years after loading. The clinical crown/implant ratio was calculated as well.ResultsTwo of 40 implants were lost before loading (incorporation rate 95%), and no further implant loss or technical complications were encountered during the 5-year follow-up period. A mean marginal bone loss of 0.70.6mm was found after 5years of function. The clinical crown/implant ratio increased with time from 1.6 at the delivery of the prosthesis to 2 after 5years of loading.ConclusionSix millimeter implants with a SLActive((R)) moderately rough surface supporting single crowns in the posterior region and loaded after 6-7weeks maintained full function for at least 5year with low marginal bone resorption.

Resonance in Bose-Einstein condensate oscillation from a periodic variation in scattering length

Using the explicit numerical solution of the axially symmetric Gross-Pitaevskii equation, we study the oscillation of the Bose-Einstein condensate (BEC) induced by a periodic variation in the atomic scattering length a. When the frequency of oscillation of a is an even multiple of the radial or axial trap frequency, respectively, the radial or axial oscillation of the condensate exhibits resonance with a novel feature. In this nonlinear problem without damping, at resonance in the steady state the amplitude of oscillation passes through a maximum and minimum. Such a growth and decay cycle of the amplitude may keep on repeating. Similar behaviour is also observed in a rotating BEC.

Analytical study of the nonlinear behavior of a shape memory oscillator: Part II-resonance secondary

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Analytical study of the nonlinear behavior of a shape memory oscillator: Part I-primary resonance and free response at low temperatures

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Mechanical and electrical driving field induced high-frequency dielectric anomalies in ferroelectric systems

Polycrystalline or single-crystal ferroelectric materials present dielectric dispersion in the frequency range 100 MHz-1 GHz that has been attributed to a dispersive ( relaxation-like) mechanism as well as a resonant mechanism. Particularly in 'normal' ferroelectric materials, a dielectric response that is indistinguishable from dispersion or a resonance has been reported. Nevertheless, the reported results are not conclusive enough to distinguish each mechanism clearly. A detailed study of the dielectric dispersion phenomenon has been carried out in PbTiO3-based ferroelectric ceramics, with the composition Pb1-xLaxTiO3 (x = 0.15), over a wide range of temperatures and frequencies, including microwave frequencies. The dielectric response of La-modified lead titanate ferroelectric ceramics, in 'virgin' and poled states, has been investigated in the temperature and frequency ranges 300-450 K and 1 kHz-2 GHz, respectively. The results revealed that the frequency dependence of the dielectric anomalies, depending on the measuring direction with respect to the orientation of the macroscopic polarization, may be described as a general mechanism related to an 'over-damped' resonant process. Applying either a uniaxial stress along the measurement field direction or a poling electric field parallel and/or perpendicular to the measuring direction, a resonant response of the real and imaginary components of the dielectric constant is observed, in contrast to the dispersion behavior obtained in the absence of the stress, for the 'virgin' samples. Both results, resonance and/or dispersion, can be explained by considering a common mechanism involving a resonant response (damped and/or over-damped) which is strongly affected by a ferroelastic-ferroelectric coupling, contributing to the low-field dielectric constant.

INPLANE RESISTIVITY IN GRAPHITE-INTERCALATION COMPOUNDS OBTAINED FROM CONDUCTION-ELECTRON-SPIN-RESONANCE MEASUREMENTS

We developed a procedure to take advantage of the magnetic-field-modulation-frequency effect on the line shape of conduction-electron-spin resonance of graphite intercalation compounds (GIC's) to extract the absolute value of the in-plane resistivity. We calculated the power absorbed in each slice of the sample normal to the wave penetration, multiplied by a factor to account for the magnetic-field-modulation-frequency effect. Room-temperature spectra of stage-I AlCl3-intercalated GIC in both H-0 perpendicular-to c and H-0 parallel-to c configurations were fitted to the theoretical line shapes and the value of in-plane resistivity (and also the value of c-axis resistivity) obtained from the fitting parameters are in reasonable agreement with those from the literature.

Energy transfer and frequency upconversion in Yb3+-Er3+-doped PbO-GeO2 glass containing silver nanoparticles

We report the infrared-to-visible frequency upconversion in Er3+-Yb3+-codoped PbO-GeO2 glass containing silver nanoparticles (NPs). The optical excitation is made with a laser at 980 nm in resonance with the F-2(5/2)-> F-2(7/2) transition of Yb3+ ions. Intense emission bands centered at 525, 550, and 662 nm were observed corresponding to Er3+ transitions. The simultaneous influence of the Yb3+-> Er3+ energy transfer and the contribution of the intensified local field effect due to the silver NPs give origin to the enhancement of the whole frequency upconversion spectra.

Surface-plasmon-enhanced frequency upconversion in Pr(3+) doped tellurium-oxide glasses containing silver nanoparticles

A frequency upconversion process in Pr(3+) doped TeO(2)-ZnO glasses containing silver nanoparticles is studied under excitation with a nanosecond laser operating at 590 nm, in resonance with the (3)H(4)-->(1)D(2) transition. The excited Pr(3+) ions exchange energy in the presence of the nanoparticles, originating efficient conversion from orange to blue. The enhancement in the intensity of the luminescence at similar to 482 nm, corresponding to the (3)P(0)-->(3)H(4) transition, is due to the influence of the large local field on the Pr(3+) ions, which are located near the metallic nanoparticles. (C) 2008 American Institute of Physics.

Frequency upconversion luminescence from Yb+3-Tm+3 codoped PbO-GeO2 glasses containing silver nanoparticles

Infrared-to-visible and infrared-to-infrared frequency upconversion processes in Yb3+-Tm3+ doped PbO-GeO2 glasses containing silver nanoparticles (NPs) were investigated. The experiments were performed by exciting the samples with a diode laser operating at 980 nm (in resonance with the Yb3+ transition F-2(7/2)-> F-2(5/2)) and observing the photoluminescence (PL) in the visible and infrared regions due to energy transfer from Yb3+ to Tm3+ ions followed by excited state absorption in the Tm3+ ions. The intensified local field in the vicinity of the metallic NPs contributes for enhancement in the PL intensity at 480 nm (Tm3+ :(1)G(4)-> H-3(6)) and at 800 nm (Tm3+ : H-3(4) -> H-3(6)). (C) 2009 American Institute of Physics. [doi:10.1063/1.3211300]