1,721,184 research outputs found
A comparative analysis based on different strength criteria for evaluation of risk factor for dental implants
No full textA numerical analysis is developed to study the interaction phenomena between endousseus titanium
dental implants and surrounding jawbone tissue. The interest is focused on the most appropriate
evaluation of the stress state arising in the tissue because of the implant under physiological loading.
The problem is considered with regard to linear elastic response of the one and to short time effect.
Different configurations of bone–implant system are described, using axial–symmetrical and threedimensional
models, by means of finite and geometric element method. The investigation attains to the
stress states induced in bone that lead to a limit condition near the effective failure surface. The
parameter commonly adopted in literature, such as the Von Mises stress, represents an excessive
simplification of problem formulation, leading to an incorrect evaluation of the real failure risk for the
implant, due to the assumption of the isotropic and deviatoric nature of the adopted stress measure.
More suitable criterion can be assumed, such as the Tsai–Wu criterion, to take into account the
anisotropy that characterises the response of bone, as well as the influence of a hydrostatic stress state.
The analysis developed offers a comparison of results by using different criteria, leading to an
evaluation of reliability of the procedure to be followed and addressing also to an evaluation of a risk
factor for the implant investigated
Investigation of biomechanical response of PDL by using an hyperelastic formulation
No full textThe work pertains to the formulation of a numerical model for
the investigation of biomechanical response of the periodontal
ligament [1] and of the evaluation of displacement behaviour
of natural teeth under different loadings.
Tissue material constitutive models are defined on the
basis of experimental data, deduced from tests on PDL
samples of animals. In vivo tests [2,3] are considered for
humans, leading to macroscopic data as forces and
displacements monitored for a specific tooth, and used to
identify elastic and viscous characteristics.
Hyperelastic isotropic and/or anisotropic models [4] are
developed for describing the mechanics of the PDL tissue,
under specific loading conditions admitting elastic response.
In the present investigation, results are validated by
comparison with experimental data on human central incisors
under intrusive forces.
Time-dependent behaviour of the PDL [5] can be
considered by means of visco-elastic constitutive models,
investigating the mobility of human teeth under application of
transversal forces of low magnitude
Investigation of bone inelastic response in interaction phenomena with dental implants
No full textObjectives. The aim of the paper is to analyze the effects of misfits in multi-implant oral
prostheses caused by defects in manufacturing of bar connecting implants. The consequent
stress–strain state on peri-implant bone tissue must be carefully considered because of the
significant effects induced.
Materials and methods. The case of a two-implant prosthesis connected by a titanium cast bar
in the pre-molar mandible region is investigated. The complex geometry requires the use
of refined finite element model. In consideration of the action induced on the bone tissue,
a specific constitutive model that includes inelastic behavior is implemented. The linear
misfits considered, estimated with reference to experimental works already present in the
literature, induce relevant strains in the peri-implant bone tissue up to a post-elastic phase.
Relaxation phenomena are also evaluated. The interaction between the bone and implant is
modeled by using contact elements to represent possible detachments at the bone–implant
interface.
Results. The response of the bone material is reported with regard to the stress/strain field
induced, evaluating the inelastic behavior in terms of plastic and relaxation responses. The
effects on the peri-implant bone tissue at the interface are evaluated.
Significance. The analysis confirms that the interaction phenomena between the multiimplant
oral prostheses and bone induced by the misfit defects of normal intensity induce
significant strain in the bone tissue and inelastic phenomena must be taken into account.
Local permanent strains of bone tissue and relaxation phenomena represent short-term
tissue response for a correct interpretation of the real biomechanical behavior of multiple
implant frames
Extension of the energy-momentum method to non-linear dynamics of elasto-damaged thin shells
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