Contents and introduction

Contents

In this study we analysed the solicitation state that grows up after the jaw-bone prostheses by traditional implants or by a combination of screw and bracket implants bound together through a wire welding.
For this reason a three-dimensional model (Finished Elements) of the whole made of implants, teeth, trabecolous bone, cortical bone, implanted bone was created, taking in consideration a perfect osteo-integration condition and the two different conditions of load.
The results showed the different tensional state related to the two different operations: in particular, a high concentration of tension occurred where traditional implants bore the bone and in correspondence of their extremity.

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Introduction

It's already demonstrated that the success or failure of various implants with a clear structural function (in particular orthopaedic and dental ones) is joined first to the conditions of the realised osseous-implant biomechanical system, a part from purely biologic conditions.
In the case of dental implants the biomechanical system to analyse is extremely complex because an ensemble of elements (teeth, implants, trabecolous bone, cortical bone) with different mechanical features and a complex geometry interact.
For this reason it's impossible to give a "rapid" evaluation of the transmission modalities of the load from teeth to bone, whereas we need using some apposite programs of Finished Elements to calculate complicated structures, subdividing them in a whole of elements with a simple geometry (tetrahedrons or parallelepipeds in the space).
The syntheses of the real situation to construct the basic geometry of the program (Finished Elements) can observe different approximation levels: the most popular models are plan or axis-symmetrical where only an isolated implant is considered and the bone is reduced to homogeneous; successively, the trabecolous and the cortical bone could be good modelled. In this way it isn't possible catching the interaction among different prosthetic implants: it is necessary to construct for it a more complicated model both three-dimensional and made of more implants.
A further step to construct more realistic models is given by the entire bone segment modelling (mandible and jaw-bone) where implants and natural teeth are inserted according to the real situation of the patient; to obtain a detailed comparison with the previous model we have to dispose important calculation resources. In this study we chose to create a three-dimensional model of a part of the jaw-bone arch, setting apposite ties to simulate the remaining part of the bone.
This fact allowed to simulate in a detailed way the geometry of implants and bone through the effective calculation resources.
We analysed two different biomechanical systems corresponding to specific different operation modalities on totally or partially edentulous jaw-bone with a law thickness of the cortical bone. The suggested technique in fact, seems simple to apply but it would be better to verify its validity from a biomechanical point of view too.
The tensional analyses allowed to show the more critical areas (that is to say the areas with important concentrations of tension) where in clinical instruction, areas with a probable bone resorption could correspond. It was so possible to highlight the limits of both the operation modalities to make than a reasoned choice; a further study of this research could be the personalising of the model, creating a model adaptable to the real situation of patient: in particular, it could be possible to change at least the thickness of the cortical bone and the quality of the trabecolous one.