258 research outputs found
"All on short" prosthetic-implant supported rehabilitations
Objectives. Short implants are increasing their popularity among clinicians who want to fulfill the constant demanding of fixed prosthetic solutions in edentulous jaws. The aim of this report was to propose a new possibility to project and realize an occlusal guided implant cross-arch prosthesis supported by ultra-short implants, describing it presented an edentulous mandible case report. Methods. A 61-year-old, Caucasian, female patient who attended the dental clinic of the University of LâAquila presented with edentulous posterior inferior jaw and periodontitis and periimplantitis processes in the anterior mandible. The remaining tooth and the affected implant were removed. Six 4-mm-long implants were placed to support a cross-arch metal-resin prosthesis. Results. At 1-year follow-up clinical and radiological assessment showed a good osseointegration of the fixtures and the patient was satisfied with the prosthesis solution. Conclusion. The method, even if it requires further validation, seems to be a valid aid in solving lower edentulous clinical cases, and appears less complex and with more indications of other proposals presented in the current clinical literature. Our case report differs from the current technique All-on-Four, which uses four implants in the mandible to support overdenture prosthesis, assuring a very promising clinical resul
Interactive design of dental implant placements through CAD-CAM technologies: from 3D imaging to additive manufacturing
In the field of oral rehabilitation, the combined use of 3D imaging technologies and computer-guided approaches allows the development of reliable tools to be used in preoperative assessment of implant placement. In particular, the accurate transfer of the virtual planning into the operative field through surgical guides represents the main challenge of modern dental implantology. Guided implant positioning allows surgical and prosthetic approaches with minimal trauma by reducing treatment time and decreasing patientâs discomfort. This paper aims at defining a CAD/CAM framework for the accurate planning of flapless dental implant surgery. The system embraces three major applications: (1) freeform modelling, including 3D tissue reconstruction and 2D/3D anatomy visualization, (2) computer-aided surgical planning and customised template modelling, (3) additive manufacturing of guided surgery template. The tissue modelling approach is based on the integration of two maxillofacial imaging techniques: tomographic scanning and surface optical scanning. A 3D virtual maxillofacial model is created by matching radiographic data, captured by a CBCT scanner, and surface anatomical data, acquired by a structured light scanner. The pre-surgical planning process is carried out and controlled within the CAD application by referring to the integrated anatomical model. A surgical guide is then created by solid modelling and manufactured by additive techniques. Two different clinical cases have been approached by inserting 11 different implants. CAD-based planned fixture placements have been transferred into the clinical field by customised surgical guides, made of a biocompatible resin and equipped with drilling sleeves
DISTRIBUTIONS ISOTOPIQUES DES PRODUITS DE TRANSFERTS TRĂS INĂLASTIQUES ENTRE IONS LOURDS
On compare les distributions isotopiques expérimentales des produits de transfert trÚs inélastiques obtenus par les réactions 40Ca (284 MeV) + 40Ca et 40Ar (295 MeV) + 232Th
Nuclear break-up of 11Be
The break-up of 11Be was studied at 41AMeV using a secondary beam of 11Be
from the GANIL facility on a 48Ti target by measuring correlations between the
10Be core, the emitted neutrons and gamma rays. The nuclear break-up leading to
the emission of a neutron at large angle in the laboratory frame is identified
with the towing mode through its characteristic n-fragment correlation. The
experimental spectra are compared with a model where the time dependent
Schrodinger equation (TDSE) is solved for the neutron initially in the 11 Be. A
good agreement is found between experiment and theory for the shapes of neutron
experimental energies and angular distributions. The spectroscopic factor of
the 2s orbital is tentatively extracted to be 0.46+-0.15. The neutron emission
from the 1p and 1d orbitals is also studied
Microscopic description of Coulomb and nuclear excitation of multiphonon states in Ca + Ca collisions
We calculate the inelastic scattering cross sections to populate one- and
two-phonon states in heavy ion collisions with both Coulomb and nuclear
excitations. Starting from a microscopic approach based on RPA, we go beyond it
in order to treat anharmonicities and non-linear terms in the exciting field.
These anharmonicities and non-linearities are shown to have important effects
on the cross sections both in the low energy part of the spectrum and in the
energy region of the Double Giant Quadrupole Resonance. By properly introducing
an optical potential the inelastic cross section is calculated semiclassically
by integrating the excitation probability over all impact parameters. A
satisfactory agreement with the experimental results is obtained.Comment: 20 pages, 2 figures, revtex, to be published in Phys. Rev.
Realtime calibration of the A4 electromagnetic lead fluoride calorimeter
Sufficient energy resolution is the key issue for the calorimetry in particle
and nuclear physics. The calorimeter of the A4 parity violation experiment at
MAMI is a segmented calorimeter where the energy of an event is determined by
summing the signals of neighbouring channels. In this case the precise matching
of the individual modules is crucial to obtain a good energy resolution. We
have developped a calibration procedure for our total absorbing electromagnetic
calorimeter which consists of 1022 lead fluoride (PbF_2) crystals. This
procedure reconstructs the the single-module contributions to the events by
solving a linear system of equations, involving the inversion of a 1022 x
1022-matrix. The system has shown its functionality at beam energies between
300 and 1500 MeV and represents a new and fast method to keep the calorimeter
permanently in a well-calibrated state
The importance of the nucleon-nucleon correlations for the eta alpha S-wave scattering length, and the pi-eta mixing angle in the low-energy eta alpha scattering length model
Using the new set of dd --> eta alpha near threshold experimental data, the
estimate of the importance of the nucleon-nucleon correlations for the eta
alpha S-wave scattering length in the multiple scattering theory is obtained
using the low-energy scattering length model. The contribution turns out to be
much bigger then previously believed. The pi-eta mixing angle is extracted
using the experimental data on the dd --> eta alpha and dd --> pi alpha
processes. The model is dominated by the subthreshold extrapolation recipe for
the eta alpha scattering amplitudes. When the recipe is chosen the model is
completely insensitive to the eta alpha parameters for the subthreshold value
of the eta cm momentum of p_{eta}^2 = -(0.46)^2 fm^{-2}. Provided that the
subthreshold extrapolation recipe is correct, a good estimate of the pi-eta
mixing angle is obtained, if the experimental cross sections for the dd --> pi
alpha reaction at the corresponding deuteron input energy are taken from the
literature.Comment: 8 pages, 2 figure
Probing pre-formed alpha particles in the ground state of nuclei
In this Letter, we report on alpha particle emission through the nuclear
break-up in the reaction 40Ca on a 40Ca target at 50A MeV. It is observed that,
similarly to nucleons, alpha particles can be emitted to the continuum with
very specific angular distribution during the reaction. The alpha particle
properties can be understood as resulting from an alpha cluster in the daughter
nucleus that is perturbed by the short range nuclear attraction of the
collision partner and emitted. A time-dependent theory that describe the alpha
particle wave-function evolution is able to reproduce qualitatively the
observed angular distribution. This mechanism offers new possibilities to study
alpha particle properties in the nuclear medium.Comment: 4 pages, 3 figure
Evidence for Strange Quark Contributions to the Nucleon's Form Factors at = 0.108 (GeV/c)
We report on a measurement of the parity violating asymmetry in the elastic
scattering of polarized electrons off unpolarized protons with the A4 apparatus
at MAMI in Mainz at a four momentum transfer value of = \Qsquare
(GeV/c) and at a forward electron scattering angle of 30. The measured asymmetry is = (\Aphys
\Deltastat \Deltasyst) 10. The
expectation from the Standard Model assuming no strangeness contribution to the
vector current is A = (\Azero \DeltaAzero) 10. We
have improved the statistical accuracy by a factor of 3 as compared to our
previous measurements at a higher . We have extracted the strangeness
contribution to the electromagnetic form factors from our data to be +
\FakGMs = \GEsGMs \DeltaGEsGMs at = \Qsquare (GeV/c).
As in our previous measurement at higher momentum transfer for + 0.230
, we again find the value for + \FakGMs to be positive,
this time at an improved significance level of 2 .Comment: 4 pages, 3 figure
Measurement of the Transverse Beam Spin Asymmetry in Elastic Electron Proton Scattering and the Inelastic Contribution to the Imaginary Part of the Two-Photon Exchange Amplitude
We report on a measurement of the asymmetry in the scattering of transversely
polarized electrons off unpolarized protons, A, at two Q values of
\qsquaredaveragedlow (GeV/c) and \qsquaredaveragedhighII (GeV/c) and a
scattering angle of . The measured transverse
asymmetries are A(Q = \qsquaredaveragedlow (GeV/c)) =
(\experimentalasymmetry alulowcorr \statisticalerrorlow
\combinedsyspolerrorlowalucor) 10 and
A(Q = \qsquaredaveragedhighII (GeV/c)) = (\experimentalasymme
tryaluhighcorr \statisticalerrorhigh
\combinedsyspolerrorhighalucor) 10. The first
errors denotes the statistical error and the second the systematic
uncertainties. A arises from the imaginary part of the two-photon
exchange amplitude and is zero in the one-photon exchange approximation. From
comparison with theoretical estimates of A we conclude that
N-intermediate states give a substantial contribution to the imaginary
part of the two-photon amplitude. The contribution from the ground state proton
to the imaginary part of the two-photon exchange can be neglected. There is no
obvious reason why this should be different for the real part of the two-photon
amplitude, which enters into the radiative corrections for the Rosenbluth
separation measurements of the electric form factor of the proton.Comment: 4 figures, submitted to PRL on Oct.
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