WO2003032862A1

WO2003032862A1 - Connection for dental prostheses

Info

Publication number: WO2003032862A1
Application number: PCT/IB2002/004155
Authority: WO
Inventors: Alessandro Cattaneo
Original assignee: Alessandro Cattaneo
Priority date: 2001-10-11
Filing date: 2002-10-10
Publication date: 2003-04-24
Also published as: ITMO20010200A1; ITMO20010200A0

Abstract

An elastically yielding element suitable for being interposed between a male part (1) and a female part (2) of components of dental prostheses, so as to produce pressure and friction along at least one friction surface (3A) of said yielding element (30), comprises a concave surface (43) opposite at least said one friction surface (3A), said elastically yielding element (30) being so shaped as to substantially work under compression.

Description

Connection for dental pros heses

The present invention concerns a yielding element for activating dental connections, conical crowns, telescopic crowns, milled parts and milled counter parts. Industrial invention patent application CA98A000002 discloses fixing means for fixing dental prostheses comprising reciprocal coupling surfaces that converge in an occluding direction and include at least one portion in an elastically yielding material so as to push parts of said surfaces towards one another.

The connection described in the aforesaid patent application consists of two portions: a first portion having at least two reciprocally opposite surfaces that diverge from one another with respect to an axis that defines the coupling direction with the surfaces of a second portion, said surfaces of the second portion converging with respect to said axis and matching with the above mentioned surfaces of the first portion. One of said surfaces is in elastically yielding material and when it is deformed in the pressure coupling with the surface of the other portion that match with it, owing to its elastic memory, causes pressure and friction between the surfaces of the two portions opposite said surface in elastically yielding material, preventing accidental dislocation of the portions. In particular, said connection may comprise a male part and a female part between which an element in elastically yielding material is interposed that is suitable for maintaining the male part and the female part firmly in contact with each another. This friction connection is based on the prior-art conometrics principle of inclined surfaces, but differs from this principle inasmuch as the connection friction is generated by the action of the elastically yielding element, which, inserted in a zone between the coupling surfaces, acts like a spring and determines friction between zones of the coupling surfaces opposite said elastically yielding element.

This enables surfaces to be created with less machining accuracy and the amount of the friction grip to be modulated without danger of accidental jamming or dislocation.

The connection described in CA98A000002 enables significantly simpler assembly operations compared with assembly of prior-art connections but has the drawback that the elastically yielding element may get damaged. As said element is frequently made of plastic material it tends to stretch when subjected to repeated mechanical stress. When this occurs, the elastically yielding element must be replaced, which causes the patient a certain degree of discomfort. The yielding element has a prismatic form and is housed in a seat that is suitable for being shapingly coupled with the element; in this way, however, the deformability of the element is, due to its dimensions, rather limited so that the insertion of the male part into the female part of the connection is hardly progressive. Prior art further comprises .various types of friction grips made from plastic material and which can be applied to different types of dental connections and joints. The most used types of friction grip have an open ring-shaped section and are suitable for being associated with cylinder- shaped patrices.

The company Cendres & Metaux S.A. uses this type of solution to make connections, for example "Mini SG" connections. The ring friction grip acts as a sheath that determines a soft metal-plastic friction. Other plastic-cap friction grips are used with a snap effect in spherical connections.

Another type of friction grip in isotropic material consists of a cylinder in silicon, or in soft plastic material, that is inserted into the matrix or patrix of a connection, said elastic cylinder is positioned lengthwise and is adjusted by a screw that compresses it, thereby modifying the extension thereof; the cylinder acts on a coupling surface of the connection and is compressed to regulate the friction grip generated thereby.

EP 0894480 describes a connection with a snap effect comprising an externally concave ring which is inserted into a matrix to cause a snap fit in an undercut of a cylindrical patrix. The elastic ring carries out a flexural work owing to the elasticity of the ^λPOM' plastic material or ^Λacetal resin', which are resins that are very elastic in relation to flexure but are resistant to compression, which substantially behave as a lamellar spring in non-isotropic material. The friction grip described above has a concave section and is provided with bevelled and non-caged ends that can rotate and slide to enable flexure of the plastic.

A further friction-grip system is disclosed in PCT/DE90/00078; this type of clip friction exploits the flexibility of plastic to bend inside an empty space to enable an undercut to be overcome.

PCT/DE90/00078 describes a U-shaped elastically yielding element comprising a first end portion and a second end portion that are interconnected by an intermediate portion. The first end portion and the second end portion can be supported against a wall defining a cavity obtained in a first part of a connection for dental prostheses.

A locking element that partially protrudes from said cavity is associated with the intermediate portion to interact with a further part of the connection, to enable said further part to be fixed to said first part.

The intermediate portion therefore actually constitutes a spring that is suitable for flexural working.

The connection known as "Mini-SG R 23.11" produced by the company Cendres & Metaux S.A. exploits the system described above in the context of the Mini SG system.

An object of the present invention is to improve prior-art connections for dental prostheses.

Another object of the invention is to obtain elastically yielding elements associatable with connections for dental prostheses that are less subject to stretching compared with prior-art elastically yielding elements.

A further object of the invention is to obtain elastically yielding elements associatable with connections for dental prostheses which, whilst having the same dimensions, are able to transmit to the male and the female part of said connections an elastic force that is more progressive than the force transmitted by the prior-art elastically yielding elements. A still further object of the present invention is to improve the one-sided friction grips, i.e. not the friction grips that cause plastic material-metal friction in the context of the operation of the connection, but the friction grips which act from only one side of the coupling surfaces between the patrix and matrix of a dental connection to determine a thrust that is translated into friction between the metal surfaces opposite the friction grip.

According to the present invention, an elastically yielding element is provided suitable for being interposed between a male part and a female part of components of dental prostheses so as to produce pressure and friction along at least one friction surface of said yielding element, comprising a concave surface opposite at least said one friction surface, characterised in that it is so shaped as to substantially work under compression. In a preferred version, said concave surface defines an arched structure in the elastically yielding element.

In another preferred version, the elastically yielding element is located in a seat obtained in one of said components. The yielding element therefore has an arched form and comes into contact with the bottom part of the seat substantially only in the end points located at the base of the arch; in this way said element is essentially subjected to compression stress, thereby significantly reducing the danger of stretching.

The yielding element furthermore has a width in the direction of the extension of the arch that is greater than the thickness measured transversally in relation to the arch. When the yielding element is located inside its seat and is pressed into the seat after coupling of the male part with the female part, the forces to which the yielding element is subjected are divided into two components which have the same intensity and are directed towards the base of the arch. In this case, as each of the aforesaid force components stresses the region near one of the semi-arches into which the yielding element is subdivided, overall a region is subjected to deformation that has an extension that is greater than that of prior-art yielding elements, in which deformability is a function of thickness. In this way, with the same dimensions, an element is obtained that is more yielding and can therefore transmit greater elastic force.

In a further preferred version, the elastically yielding element comprises projecting means arranged for positioning the elastically yielding element with respect to said components.

In a still further preferred version, the projecting means is obtained in the concave surface.

In a still further preferred version, the projecting means acts as stop means engaging in corresponding recess means obtained inside the aforesaid seat of the yielding element.

Owing to the projecting means it is therefore possible to avoid accidental shifts of the yielding element inside the seat in which said element is arranged. Furthermore, the projecting means enables the yielding element to which it is associated to be locally stiffened. In this way the stiffness of the yielding element can be precisely graduated, in other words a yielding element can be obtained that is less stiff along certain portions but stiffer along further portions associated with the projecting means.

The invention can be better understood and carried out with reference to the accompanying drawings, which show some exemplifying and not restrictive embodiments thereof, in which: Figure 1 is a plan view of a male part of a connection associatable with a yielding element according to the invention;

Figure 2 is a left-hand side view of Figure 1;

Figure 3 is a section taken along a horizontal plane of a connection with which a yielding element according to the invention is associated;

Figure 4 is a front view of a yielding element according to the invention;

Figure 5 is a perspective view of the yielding element of

Figure 4; Figure 6 is a perspective view of a yielding element according to the invention, provided with projecting means; Figure 7 is a perspective view of the yielding element of Figure 6, rotated by 180° around its own longitudinal axis; Figure 8 is a schematic plan view of components of dental prostheses associated with the yielding element of Figures 6 and 7 ;

Figures 9 and 10 are sections like those of Figure 3, showing elastically yielding elements subjected to different degrees of stress, in particular the elastically yielding element shown in Figure 9 is subjected to a smaller degree of stress compared with the degree of stress to which the elastically yielding element shown in Figure 10 is subjected.

Figures 1 to 5 show a connection for dental prostheses comprising a male part 1, fixed to a prosthesis structure C, which is associated with a female part 2.

The male part 1 has a body A in which a pair of grooves X are obtained having the form of a conical semi-structure, said conical semi-structure being upturned in relation to a given insertion axis Z; a pair of raised parts Y in the form of a conical semi-structure are also obtained in the body A. An inclined coupling surface 3 is also shown, which comes into contact with a friction surface 3A of the elastically yielding element 30 located in a seat 31 of the female connection 2 during the coupling of the female connection 2.

The surface 4 of the male connection 1 is fixed to the prosthetic structure C. The female connection 2 is fixed to another part of the prosthetic structure that is not shown. As shown in Figure 3, the seat 31 has a prismatic form with a trapeziform section, whilst the elastically yielding element 30 has a bridge structure defined by an arched bottom surface 43. When the female part 2 is coupled with the male part 1, the surface 3 of the male part 1 comes into contact with the respective friction surface 3A of the yielding element 30 and presses said yielding element 30 inside the seat 31. The yielding element 30 adheres to the seat 31 along the walls 40 that constitute the oblique sides of the trapeziform section, but substantially not along the entire surface arranged along the larger base 42 of the aforesaid trapeziform section. In this way the force transmitted by the male part 1 to the yielding element 30 divides into two components that act in the directions indicated by the arrows F and that are applied at the points 41 at the base of the arched surface 43. Owing to its particular configuration, the yielding element 30 is therefore prevalently subjected to compression stress. It is furthermore subjected to considerable deformation, particularly in the direction of the arrow F' , thereby being able to transmit great elastic force to maintain the male part 1 and the female part 2 firmly connected together. Figures 9 and 10 show the elastically yielding element 30 subjected to stress of differing degrees.

In particular, in the case of rather high stress, as in the case shown in Figure 10, the components of the force transmitted by the male part 1 are arranged in the manner shown by the arrows Fl, in other words so as to be almost parallel to the larger base 42 of the trapeziform section of the seat 31. In the embodiment of Figures 6 and 7, the yielding element 30 is provided with stop means comprising a projecting part 50 that protrudes from the arched surface 43. The function of the projecting part 50 is clearly disclosed in Figure 8, which shows a milled crown 51, situated in the patient's mouth, on which a milled portion 52, known as the milled part, is created, and which acts as the male part 1. The milled crown 51 is designed to be coupled with a movable prosthesis 54, provided with a shaped portion 53, known as the milled counter part, which acts as the female part 2, said shaped portion 53 being suitable for shapingly coupling with the milled part 52. When the movable prosthesis 54 needs to be connected to the milled crown 51, the female part 2 is coupled with the male part 1 and the yielding element 30 is interposed. As already described above, the yielding element 30 is deformed to produce friction and pressure between the male part 1 and the female part 2, thereby ensuring a stable and durable connection.

Furthermore, the projecting part 50 created on the yielding element 30 is inserted into a recess 55 with which the seat created in the female part 2 is provided, thereby preventing any accidental dislocations of the yielding element 30 from the seat, as a result of which the yielding element 30 could be involuntarily ejected from its seat.

In an alternative embodiment that is not shown, the yielding element 30 may be provided with a plurality of projecting parts 50. Finally, the yielding element 30 may be used for connecting any male part and any female part of components of dental prostheses, such as dental connections, milled parts or double crowns .

Claims

CLAIMS Elastically yielding element suitable for being interposed between a male part (1) and a female part (2) of components of dental prostheses, so as to produce pressure and friction along at least one friction surface (3A) of said yielding element (30), comprising a concave surface (43) opposite at least said one friction surface (3A), characterised in that it is so shaped as to substantially work under compression. Elastically yielding element according to claim 1, wherein said concave surface identifies in said elastically yielding element (30) an arched structure. Elastically yielding element according to claim 1, or 2, and insertable into a seat (31) obtained in said components . Elastically yielding element according to claim 3, and arranged for interacting with a face of said seat (31) adjacent to said concave surface (43) at the end points (41) of said arched structure. Elastically yielding element according to claim 3, or 4, wherein said seat (31) has the form of a prism. Elastically yielding element according to claim 5, wherein said prism has a trapeziform section. Elastically yielding element according to claim 6, and arranged for interacting with the walls of said seat (31) along the surfaces located at the oblique sides (40) of said trapeziform section, but substantially not along the entire surface situated at the larger base (42) of said trapeziform section. Elastically yielding element according to one of the preceding claims and further comprising projecting means protruding from said elastically yielding element (30) .

9. Elastically yielding element according to claim 8, wherein said projecting means (50) acts as stop means.

10. Elastically yielding element according to claim 8, or 9, wherein said projecting means (50) is obtained on said concave surface (43) .

11. Elastically yielding element according to any one of claims 8 to 10, wherein said projecting means (50) is arranged for engaging in recess means (55) obtained on said components. 12. Elastically yielding element according to any one of claims 8 to 11, wherein said projecting means (50) acts as stiffening means of said elastically yielding element (30) .