Dentistry – Method or material for testing – treating – restoring – or... – Crown
Patent
1992-05-13
1994-07-12
Mancene, Gene
Dentistry
Method or material for testing, treating, restoring, or...
Crown
433221, A61C 508
Patent
active
053283724
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a crown-root reconstitution system comprising a physiological dental securing peg made of a composite material and a crown reconstituting material placed between the peg and the sound dentine walls, as well as to a process for manufacturing this peg.
Dental securing pegs which are currently used at the present time in odontology, are generally made of metal alloys. However, these pegs have not proved to be totally satisfactory as, even if they are made of precious alloy, which is often the case for reasons of regulations, they may give rise to phenomena of corrosion and oxidation of a chemical or electrochemical origin.
In order to overcome this drawback, it has already been envisaged, as described in Patent FR-A-2 588 181, to make an endobuccal prosthesis of composite material constituted by fibers of high mechanical strength, included in a resin constituting the matrix of the material. A peg is also known, as described in Patent FR-A-2 626 167, comprising a central thread or filament around which is moulded a synthetic resin which preferably contains fibers. Patent DE-A-3 825 601 likewise discloses a dental securing peg constituted by a piece of revolution made of composite material formed by two parts of different diameters, coaxial in line with each other, the part of smaller diameter being adapted to engage in the root canal of the tooth. The pegs manufactured in this way may be given interesting physical and mechanical characteristics but the pegs thus obtained are not totally satisfactory as their mechanical properties are far away from the natural characteristics of the dentine. The disparity of the mechanical properties between those of the peg and those of the dentine is a constant source of disturbance, with a concentration of the stresses at certain points, and this may result in the destruction of the reconstruction assembly if the stresses applied to this assembly, during chewing, end up by disconnecting the constituent elements.
The present invention aims at overcoming this drawback by providing a reconstitution system which dampens the stresses and distributes them at a maximum in the zones subjected to the efforts.
To that end, this crown-root reconstitution system comprises a physiological dental securing peg of a composite material, and a crown reconstituting material placed between the peg and the sound dentine walls, the peg being constituted by a piece of revolution of the type made of high strength fibers embedded in a resin constituting the matrix, the fibers being parallel to one another, elongated in the axial direction of the peg, continuous from one end of the peg to the other, in the central part of this peg, is characterized in that the resistant fibers are equally tensioned and pre-stressed in traction so that the peg thus obtained presents a transverse modulus of elasticity of the order of magnitude of the average of that of the dentine, namely 18 GPa, and a longitudinal compression-tensile strength and shear strength greater than the corresponding average values for the dentine.
A securing peg according to the invention presents anisotropic mechanical characteristics, i.e. which depend considerably on the direction of application of an effort with respect to the longitudinal direction of the fibers, i.e. of the peg. Thus, such a peg made from high performance carbon fibers embedded in an epoxy resin matrix, has a transverse modulus of elasticity which has a value of 8.5 GPa for an angle of application of the traction effort, with respect to the transverse direction, of 0.degree. and a value of 34 GPa for an angle of 20.degree. which gives an average of 21 GPa in the angular range of 0.degree. to 20.degree. which corresponds to the average orientation of the stresses exerted on a tooth during chewing. This value is close to the transverse modulus of elasticity of the dentine which is 18 GPa. Concerning the compression resistance, it may go up to 500 MPa, i.e. 200 MPa more than the mean resistance of the dentine. Such characteristics are obtai
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Duret Bernard
Duret Francois
Reynaud Marc
Reynaud Pierre-Luc
Lucchesi Nicholas A.
Mancene Gene
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