WO2003078741A2

WO2003078741A2 - Device for securely fixing a prosthetic dental cap to the support thereof

Info

Publication number: WO2003078741A2
Application number: PCT/FR2003/000766
Authority: WO
Inventors: Jean-Yves Cuenot
Original assignee: Jean-Yves Cuenot
Priority date: 2002-03-15
Filing date: 2003-03-10
Publication date: 2003-09-25
Also published as: FR2837090B1; WO2003078741B1; AU2003244685A1; WO2003078741A3; AU2003244685A8; EP1496813A2; FR2837090A1

Abstract

The invention is used to improve and secure the assembly of a prosthetic dental cap and the support thereof, whereby said two parts are nested together and, optionally, glued. The invention is characterised in that the contact surface between the two parts to be assembled is significantly increased by means of one or more complementary relief designs which form at least one set of alternating elements, namely convex and concave portions of surface or ridges, on the contact surface of each of the parts to be assembled. In this way, when the two parts are nested together, no gap exists between the two parts, either empty or filled with a cement or other substance which is malleable for assembly and subsequent hardening, except a possible housing for a fine layer of glue. In a preferred embodiment of the invention, the contact surface between the two parts is a pyramid or a truncated pyramid with a star-shaped base, preferably comprising three or four arms. The invention also relates to parts which are fitted with the aforementioned relief designs in accordance with the invention, the method of fixing a cap to the support thereof using the inventive device, and the method of producing two parts consisting in using preforms and a computer-assisted design and production software program.

Description

Secure fixation of a dental prosthesis cap on its support

The field of the present invention is that of dental prostheses and more precisely that of fixing dental prosthesis caps on their support.

According to the most common prior art, a support is implanted in a natural or artificial tooth stump, or directly in the maxillary bone. Then a replacement crown is attached to it. The two parts can thus have notches, grooves, hooks or other roughness ensuring mechanical assembly. The assembly can also be ensured, in addition to the mechanical means, by glues, cements, welds, solders. These malleable substances before hardening also make it possible to fill the interstices between the two parts when they are juxtaposed. Thus, patents US 5,316,478, DE 827,689 and US 1,612,227 claim different particular shapes of the two parts which join together leaving gaps to be filled with a fluid or moldable substance which hardens later. This technology is now outdated, mainly due to the lack of durability of the prostheses obtained. Indeed, the differences in the coefficient of expansion between the materials of the two parts and the binders of notable thicknesses gradually destroy the cohesion of the assembly during the thermal cycles to which it is subjected. The substances that make up the prosthesis also have different redox potentials in the electrolyte of saliva, which promotes their chemical degradation. This is why, the current tendency is to manufacture the prosthesis of pulped and cut, or the implant which replaces it, in three assembled parts, namely, one or more pins fixed in the dental channel (s) or an implant in the maxillary bone, the cap support fixed on the post or implant, and the cap which is itself fixed on its support, taking care to adjust them as well as possible, that is to say by reducing the interstices as much as possible.

Nowadays, on the post, we first adjust the cap support which allows to intervene on the cap without altering the roots or their substitutes. This support is generally made of malleable synthetic resin before hardening or of a cast alloy. The cap is preferably made of ceramic for aesthetic reasons. Those skilled in the art know how to work the post to adapt it to the morphology of the patient for whom the prosthesis is intended. Patent FR 98 02244 of the inventor of the present invention describes a process for adapting it also with precision in the cap or in its support. According to current art, the support, abutment or inlay-core, is, on the part to emerge from the root, a reduced reconstruction by homothety of the external faces of the natural dental crown. This homothetic reduction has the shape of a nipple as smooth and regular as possible, resembling a trunk of a pyramid with trapezoidal faces and the base of which is a convex polygon, often a pentagon. On the surface of this emerging nipple part, the prosthetic cap is fitted by interlocking and gluing, which has a bowl in pyramid trunk which is also as smooth and regular as possible and which is adjusted by fitting into the nipple. The surface of the trunk of the pyramid may not be perfect, may have manufacturing defects, whether desired or not, for example irregularities in the polyhedron itself or in its faces, non-planar faces, rounded or blunt edges, scratches or not very pronounced grooves, small asperities in hollow or in relief. All these imperfections only slightly increase the surface area of the external surface of the nipple and the complementary bowl, in any case less than 5%. Their accidental occurrence or being the result of the manufacturing process or machining tools does not improve not significantly, or even worsening in most cases, the holding of the cap on its support. It follows that the fixing of the cap on its support is not very safe and constitutes the weak point of the prosthetic reconstruction of the tooth, especially if the post has been perfectly fixed to the support of the cap, for example thanks to the process of patent FR 98 02244.

The present invention improves and secures the fixing of the cap on its support. It consists in fact of a device which makes it possible to improve the fixing by fitting and possibly bonding of a dental prosthesis cap on its support, characterized in that the surface of the contact surface between the two parts to be assembled has been notably increased by one or more complementary sculptures forming on the contact surface of each of the two parts to be assembled at least an alternation of elements, portions of surfaces or edges, convex and concave so that, when the two parts are nested There is no other gap between the two parts, which would remain empty or filled with cement or another substance malleable to the assembly and hardening later, than the possible accommodation of a thin layer of glue. According to the terminology of the present description and of the claims which follow it, the contact surface of the cap-support assembly is the surface in which the surfaces of the two parts coincide after fitting apart from the plane of the collar marked C1, C2 and C3 in the accompanying drawings. Each of the parts has its own contact surface.

The sculptures are asperities or hollows which modify the contact surface, in particular the pyramid trunks mentioned above on page 2, lines 15 to 18 of each of the two parts, by alternating concave and convex elements, surface portions. or respectively reentrant or projecting edges. According to the invention, the sculptures are useful for increasing the surface area of the contact surface of the two parts. The sculptures are said to be complementary when at each roughness of one of the parts there is a hollow in the other so that the contact of the assembled parts continues at the level of the sculptures. The increase in the surface area of the two complementary contact surfaces is obtained by removing, effectively or virtually, material in the part comprising the nipple and by removing similarly less material in the complementary bowl. We thus obtain complementary asperities hollows. The pattern can be complicated by the addition of hollows in the asperities and asperities in the hollows. However, it is essential that the contact surfaces of the two parts can fully fit into each other. According to one embodiment of the invention, the contact surfaces are portions of planes on which asperities have been placed and the complementary recesses on the other part, it being understood that a part may contain both asperities and recesses , which implies that the other part has complementary hollows and asperities. The area of the contact area is said to have been significantly increased if the increase is 5% or more of the area of the contact area. The percentage of 5% was chosen arbitrarily enough to differentiate manufacturing vagaries or other various reasons from the deliberate desire to significantly increase the surface area of the contact surface. It should be noted here that if the surface area of one of the two parts has been accidentally increased or without a well-intentioned will, the other part will not include the additional sculpture, so that the surface area of the effective surface contact has decreased. With a bonding force equal to cm ² , the connection of the two parts is weakened. The assembly is also weakened by the gap formed that it remains empty or filled with a binder. On the contrary, according to the invention, the increase in the surface area of the contact surface makes it possible to correlatively strengthen that of the connection of the two parts, with an adhesive force of equal cm ² . The precise nesting of the asperities in the recesses also increases the connection of the two parts and is opposed to any relative movement of rotation or translation.

This explains why it is important that the contact surface of the cap is complementary to the contact surface of the support. This invention is quite surprising and not accessible to a person skilled in the art who seeks to make the contact surface between the cap and its support as homothetic as possible from the outside of the cap so as not to weaken the headdress, especially if it is ceramic. According to one embodiment of the invention, the contact surface between the two parts, cap and support, is broken by at least one edge. The edges according to the invention are portions of straight lines or curves which can also be sharp, rounded or blunt. They are protruding or inward. The advantage of these edges, to which complementary edges correspond on the other part is to improve the fixing of the two parts and to better avoid any relative rotation or translation between the two parts, which improves the rigidity and the security of the fixation.

According to one embodiment of the invention, the contact surface of each of the two parts, cap and its support, includes at least one projecting edge and a re-entrant edge. According to a variation of this embodiment, the contact surface between the two parts, cap and support, is that of a pyramid or a trunk of a pyramid, the base of which is a regular or irregular star. According to the terminology of the present description, a star is said to be regular when the length of its sides and the angles of its points are equal. It is said to be irregular otherwise. If, in this variation of embodiment, the nipple is carried by the support, we approach the embodiment of the prior art described above on page 2, lines 15 to 18. But the nipple in the shape of a pyramid trunk with a convex polygon base, generally pentagon, has been dug with stripes themselves having the shape of a pyramid or a trunk of pyramid of the same summit as the nipple. This variation in construction is preferred because, while sufficiently increasing the contact surfaces, it is easy to produce and contains several projecting and re-entrant edges, a characteristic which contributes to the rigidity and therefore to the security of the fixing of the two parts.

According to one embodiment of this variation, we particularly privilege the case where the star at the base of the pyramid or the trunk of the pyramid is with three or four branches, that is to say that the star forms a Y or an X, regular or irregular. These two forms gave the best security to the fixation. It does not matter whether the X or the Y are in relief or hollow on the support. The X shape is preferably used for molar or premolar prostheses, while the Y shape is preferred for canine or incisor prostheses.

The present invention also relates, as a new product, to the assembly consisting of the cap and its support, before or after their assembly, characterized in that it contains the device according to the invention. The present invention relates in particular to the cap-support assembly whose device according to the invention includes an edge. The present invention relates in particular to the cap-support assembly according to the invention, the contact surface of each of the parts, the cap and its support, includes at least one projecting edge and a re-entrant edge. The present invention also relates to the cap-support assembly according to the invention, the contact surface of which is that of a pyramid or of a trunk of a pyramid with a star base, and in particular when said star is with three or four branches. The present invention further relates to the method of fixing a dental prosthesis cap on its support, characterized in that it is improved by the device according to the invention. The present invention finally relates to the method of manufacturing the assembly consisting of a dental prosthesis cap and its support provided with the device according to the invention characterized in that it includes the use of one of the elements of the '' including the use of preforms and the use of computer-aided design and manufacturing software abbreviated as CAD / CAM. It is in fact thanks to the use of these preforms known to those skilled in the art or of this software, also known, or the simultaneous or successive use of the two that the technician will be able to affix fairly fine sculptures but strong enough on the often ceramic cover and its support so that they can fit perfectly into each other, and thus ensure sufficient security for the attachment of the two parts with or without adhesive while avoiding weakening the together.

The present invention will be better understood on reading the following examples and the accompanying drawings. Drawing 1 is a perspective view of a canine root preparation with a trapezoidal section carrying a Y-shaped inlay-core.

The drawing le is a top view perpendicular to the plane Cl

(neck plan) of the inlay-core in Y on the preparation of the canine root.

Drawing 2 is a perspective view of the preparation of a molar with an X-shaped inlay-core. Drawing 2c is a top view perpendicular to the plane C2 (neck plane) of the inlay-core in X on the preparation of the molar. Drawing 3 is a perspective view of an implant, to be screwed onto the maxillary bone, of circular section carrying an abutment in X. Drawing 3c is a top view perpendicular to the plane C3 (plane of the collar) of the X-shaped abutment screwed onto the implant. In these drawings, the scriptural markers have the following meaning: B represents one of the blunt edges of a pyramid trunk with a star-shaped base of an inlay-core or a stump. I represents a titanium implant to be screwed onto the maxillary bone.

M represents the coronary part (emerging from the gum) in X or in

Y of inlay-core or abutment.

P represents the pertuis of the abutment in X screwed on the implant. R represents the natural root or roots of the tooth which have been sawn off at the level of the collar according to the plans C1 or C2.

T represents the part of the inlay-core which carries the stud (s).

V represents a screw which fixes the abutment in X on the implant. α represents the angle which separates the axis of two contiguous branches of the star with 3 or 4 branches (in Y or in X) on the plane of the collar (Cl, C2 or C3).

Example 1: inlay-core of Y-canine prosthesis. In drawings 1 and le, we see that the inlay-core carries a pin T which is fixed in the radical channel of the root R of the natural tooth which has been sawn along the plane of the Cl neck. The inlay-core is extended in the part emerging from the root by an approximate trunk of pyramid whose large base on the plane of the Cl neck is a three-pointed star, in Y. In this plane Cl, the angle α which separates each pair of contiguous branches is equal to 120 °. The small base of the pyramid trunk is too small to be able to determine a particular shape for it, but any cut parallel to the plane C1 inside the pyramid trunk is also a Y-shaped star. pyramid has 3 edges that are roughly straight but blunt and even slightly flared. The ceramic cap of the prosthesis which restores the crown imitates the natural crown on its exterior.

Its interior has the shape of a bowl, the flat edge of which is complementary to the part released from the sawn edge of the root along the plane Cl. The bowl is extended by sculptures complementary to the emerging part of the inlay-core.

It can be seen in the drawing 1C that the area of the contact surface of the two parts according to this example is significantly larger than the area of the contact surface of the inlay-core that would have been obtained according to the prior art which would have given the pyramid trunk a triangular base in the plane Cl.

This characteristic, combined with the rigidity provided by the embedding of the faces of the respective pyramid trunks of the inlay-core support and of the cap gives the fixing of the two assembled parts improved solidity and security.

Example 2: inlay-core of molar in X.

Figures 2 and 2C show that in this case, the angle α has 90 ° and that the inlay-core has three tenons instead of one in example 1. But if these two characteristics are adapted to the morphology of the natural tooth, they do not reduce the improved quality of the fixing of the cap on the inlay-core in X compared to the prior art.

Example 3: X-shaped abutment screwed onto an implant.

The drawings 3 and 3C also show that if the assembly specific to the implant which is known from the prior art has been used, the method of fixing the cap on the abutment is completely similar to that of the example 2 for fixing the cap on the inlay-core. It follows that in this example too, the binding is improved and secure compared to the prior art. We compared the pull-out resistance of 5 infiltrated alumina caps of the In-Ceram brand produced by the company Vita glued on volumes of nickel-chrome alloy abutments of brand Wiron 99 from the company Bego in the shape of a parallelepiped and in the shape of a star.

According to the protocol of the experiment, an average pullout force of:

1043 N with the star supports according to the invention, 745 N with the abutments including a traditional five-sided polyhedron. It can be seen that the pullout force of the two parts, cap and support, is very much greater for the product according to the invention, this with a substantially equal standard deviation. The study of these examples and the accompanying drawings show that the geometric figures mentioned in this text are precisely adapted to the morphology of each patient. They do not necessarily meet the geometric definition of designated entities, more or less rectilinear edges and not sharp, trunk of imperfect pyramids, somewhat thin stars. These variations result from the machining mode, artisanal or CAD / CAM, and from the type of material used to make them. What counts mainly, in addition to the increase in the surface area of the contact surfaces, is that the sculptures of the cap and its support are complementary.

Likewise, the present invention is not limited to the examples given above. The present invention also includes any method and any dental prosthesis from the spirit of the present invention.

Claims

claims

1). Device making it possible to improve and secure the fixing by fitting and optionally gluing a dental prosthesis cap on its support, characterized in that the surface of the contact surface between the two parts to be assembled has been notably increased by one or more sculptures complementary forming on the contact surface of each of the two parts to be assembled at least an alternation of elements, surface portions and edges, convex and concave so that, when the two parts are nested, there is no the two pieces of other gap, which would remain empty or filled with cement or another substance malleable to the assembly and hardening later, than the possible accommodation of a thin layer of glue. 2). Device according to claim 1 characterized in that the contact surface between the two parts, cap and support, is broken by at least one edge.

3). Device according to either of Claims 1 and 2, characterized in that the contact surface of each of the two parts, the cap and its support, includes at least one projecting edge and a reentrant edge. 4). Device according to one of claims 1, 2 or 3 characterized in that the contact surface between the two parts, cap and support, is that of a pyramid or a trunk of a pyramid whose base is a star. 5). Device according to Claim 4, characterized in that the star at the base of the pyramid or the trunk of the pyramid has three or four branches.

6). Assembly consisting of the cap and its support, before or after their assembly, characterized in that it comprises at least one device according to one of claims 1, 2, 3, 4, or 5. 7). An assembly according to claim 6 characterized in that the contact surface of the cap support carries an element of the assembly consisting of a protruding edge, a reentrant edge, a protruding edge and a reentrant edge, a raised pyramid whose base is star-shaped, a hollow pyramid whose base is star-shaped, a raised pyramid trunk whose base is a star, a hollow pyramid trunk whose base is a star, an embossed pyramid whose base is a three-pointed star, a hollow pyramid whose base is a three-pointed star, a raised pyramid trunk whose base is a three-pointed star, a hollow pyramid trunk whose base is a three-pointed star, an embossed pyramid whose base is a four-pointed star, a hollow pyramid whose base is a star with four branches, a relief pyramid trunk whose base is a four-pointed star, a hollow pyramid trunk whose base is a four-pointed star. 8). Element of the assembly consisting of an insulated cap and an insulated cap support characterized in that it constitutes a cap or a support of an assembly according to any one of claims 6 or 7. 9). Method of fixing a dental prosthesis cap on its support, characterized in that it is improved by a device according to any one of claims 1, 2, 3, 4, or 5.

10). Method of manufacturing the assembly consisting of a dental prosthesis cap and its support provided with the device according to any one of claims 1, 2, 3, 4 or 5 characterized in that it includes the use of the '' one of the elements of the set including the use of preforms and the use of computer-aided design and manufacturing software.