WO1990009766A1 - Telescopic crown - Google Patents

Abstract

To produce a telescopic crown with a primary crown which can be secured on a tooth stump and a secondary crown which may be pushed over it, wherein the inner wall of the secondary crown is fitted with a retainer engaging by means of a claw in a recess in the primary crown, which permits a safe and permanent seating in a prosthesis fitted with telescopic crowns at low cost and avoids embedding the spring-loaded retainer in the secondary crown material, it is proposed to make the retainer (5) in the shape of a U, the base (9) of which carries the claw (6) at its centre and the side-members (10) of which project downwards on the side away from the claw, and to insert the retainer (5) in a recess (11) in the inner wall of the secondary crown (3), on the side-walls of which the side-members (10) can be supported and the base of which is at a distance from the base (9) of the retainer (5) corresponding to the spring travel of the claw (6).

Description

 Telescopic crown

The invention relates to a telescopic crown, consisting of a primary crown that can be attached to a tooth stump and a secondary crown that can be pushed onto it, a spring-loaded retention part being held in the inner wall of the secondary crown, said retention part projecting over the wall towards the outer wall of the primary crown Snap into a recess of the same shape in the outer wall of the primary crown is inserted in the desired position. Such telescopic crowns are used to fix dental prostheses, removable, partial dental prostheses being attached to telescopic crowns. Many dentists prefer the telescopic crown technique over all conventionally manufactured holding elements such as attachments, anchors and the like in order to give the removable prostheses the correct hold in the mouth. The secondary crown is usually pushed onto the primary crown with friction. However, the desired friction is not always achieved, and it is also known that after a certain amount Wear of the dental prosthesis reduces the friction of the telescopic crowns and an exact fit of the prosthesis is no longer guaranteed. It is disadvantageous for the prosthesis wearer that even if the dental prosthesis is lifted slightly, food residues can slide under the prosthesis. Even when speaking or laughing, a movement of the prosthesis between the still standing natural teeth is a very unsettling situation for the prosthesis wearer. The conventional technology of the telescopic crowns is very complex with regard to production, because the exact friction can be determined by time-consuming, careful grinding or grinding. A generic prior art is known from DE 29 45 489 C2, in which a rubber-elastic ring or the like is inserted into a recess in the secondary crown wall, as a result of which a positive and non-positive connection is achieved between the primary crown and the secondary crown shall be. In practice, however, such a part has not proven itself because, because of the extremely small spaces available, a tight fit cannot be achieved due to the small protrusion of the rubber body. A telescopic crown of the type described in the preamble is also known from operational practice, with a spring-loaded in a cavity of the secondary crown. the web is held with a catch arranged at the free end of the cantilever arm. After the secondary crown has been pushed over the primary crown, this catch engages in a corresponding recess in the primary crown. However, this arrangement has also proven to be unsustainable, since the mounting of the web on the secondary crown loosens and loosens due to the bending forces of the web occurring, and can even break out.

On the basis of this prior art, the object of the invention is to create a telescopic crown of the generic type which, with little effort, enables the prosthesis equipped with telescopic crowns to be seated securely and precisely, with the resilient retention being embedded. part in the material of the secondary crown is avoided. To achieve this object, the invention proposes that the retention part is U-shaped, the base of which bears the catch at least approximately in the center ^and its legs protrude to the side facing away from the catch, and that the retention part is in a recess in the inner wall of the secondary crown is used, on the side walls of which the legs can be supported and the bottom of which is at a distance corresponding to the spring travel of the detent from the base of the retention part. The training enables the dental technician to place the secondary crown on the primary crown without friction, with the catch in the secondary crown only snapping into the locking recess of the same shape in the primary crown in the desired position, as a result of which the desired securing of the position is achieved perfectly. The secondary crown can be removed from the primary crown by overcoming the latching action to release the dental prosthesis by applying appropriate force. In addition, even with the small installation space available for the retention part in the

Secondary crown ensures the suspension effect to a sufficient extent, the resilient retention part springing back when the secondary crown is pushed onto the primary crown, so that the particularly hemispherical detent is pushed back until the desired position is reached, in which the detent in the ent speaking hemispherical recess of the primary crown can snap into place with at least partial relaxation of the spring force of the retention part. This locking process is connected with an audible "click" so that the user can also acoustically detect the correct seat.

This arrangement also has the advantage that the retention part only has to be inserted into the recess in the secondary crowns, that is, it is not embedded in them. The resilient possibility of movement of the retention part is thus ensured without thereby the secondary crown or material areas of the secondary crown would be loaded. This prevents the secondary crown material from breaking out or being excessively loaded. In addition, the permanent function is ensured because the retention part is loaded only when the secondary crown is pushed over the primary crown or when the secondary crown is removed from the primary crown in the sense of deflection, while in the desired position the retention part is arranged almost or completely relaxed, so that permanent plastic deformation of the retention part can be excluded with certainty.

It is preferably provided that the catch and the east recess are hemispherical. It is furthermore particularly preferred that the side walls of the recess are undercut and the legs are arranged under the undercut. In this way, the retention part is held in the corresponding recess of the secondary crown very securely and in the normal case in a non-detachable manner, the removal of the retention part remaining possible using a suitable tool.

It is particularly preferred that the cross-sectional shape of the recess is dovetail-shaped and the legs are inclined at the same angle.

A possible variant is seen in that the catch of the retention part consists of metal. According to a further variant it is provided that the retention part consists of metal. It can also be provided that the retention part consists of plastic.

It is preferably provided that the retention part has an integrally molded catch.

A particularly preferred embodiment is seen in the fact that the recess receiving the retention part has a height of approximately 0.7 to 1.1 mm, the retention part can be inserted flush into the recess, the leg of which has a free length of approximately 0.3 have up to 0.5 mm and the notch protrudes by about 0.2 to 0.4 mm, in particular 0.3 mm. A particularly secure and wobble-free fit of the retention part in the corresponding recess is achieved in that the diverging legs of the retention part have a narrow edge running parallel to the base, their outer leg surfaces adjoining the edge edge have an angle of 50 ° to one another enclose, enclose their inner surfaces adjoining the marginal edges at a flat angle of in particular 140 ° and extend at a more acute angle of approximately 80 ° to the base.

It is further preferably provided that the width of the retention part is approximately 1.1 to 1.5 mm, in particular 1.3 mm. It is also advantageous that the recess for the retention part and the latching recess is formed in each case by a molded part of the same shape, made of completely combustible plastic, which is lost. It can preferably be provided that the molded part for forming the recess for the retention part is cuboid with an open cover surface, the narrow side surfaces for forming the undercut being convergent to the cover surface and the undercut shortly before connection to the longer one Side faces ends.

Furthermore, it can be provided that the molded part for forming the latching recess is a rectangular plate with a central depression, with struts striving towards the top in particular at its short marginal edges

Retaining webs are formed, which are connected to the plate in particular via predetermined breaking points. Exemplary embodiments of the invention are shown in the drawing and are described in more detail below. It shows:

1 shows a telescopic crown during the pushing together process; 2 shows a detail in side view and in plan view; 3 shows a further detail in a side view; 4 shows the retention part of the telescopic crown in different load conditions; Figure 5 seen a molded part in plan view and in cross section. Fig. 6 shows another molded part in plan view and

Cut ; Fig. 7 seen a retention part in view and in section. The telescopic crown, which is shown, for example, in FIG. 1, essentially consists of a primary crown 2 fastened on a ground tooth stump 1 and a secondary crown 3 that can be pushed onto it. The secondary crown 3 has an inner cavity for this purpose, which has little play the outer shape of the primary crown 2 is adapted. To secure the desired position, a resilient retention part 5 is held in the inner wall of the secondary crown 3, which is directed parallel to the push-on direction (shown by the arrow 4), which has a catch 6 projecting beyond the wall towards the outer wall of the primary crown 2 engages in a locking recess 7 of the same shape in the outer wall of the primary crown 2 and engages in a locking recess 7 of the same shape in the outer wall of the primary crown 2. The retention part springs in the direction transverse to arrow 4, as can be seen in FIG. 4 (see arrow 8). The notch 6 and the notch 7 are each hemispherical, the functional parts engaging in the desired position without play or almost without play. The retention part 5 is essentially U-shaped, the base 9 of which carries the catch 6 in the center. Its legs protrude on the side facing away from the catch 6. The retention part 5 is inserted into a corresponding recess in the inner wall of the secondary crown 3, on the side walls of which the Support leg 10, the bottom of which is at a distance corresponding to the spring travel of the catch 6 from the base 9 of the retention part 5, so that when the secondary crown 3 is pushed onto the primary crown 2, the catch can completely disappear in alignment with the inner wall of the secondary crown 3 , as can be seen from Figure 4.

The side walls of the recess for receiving the retention part 5 are designed such that they engage under the undercut. In this way, the retention part is held securely in the recess. The cross-sectional shape of the recess is preferably dovetail-shaped, the legs 10 being inclined at the same angle. In the exemplary embodiment, the retention part 5 together with the catch 6 is made in one piece from a suitable plastic. The basic structure of the recess 11 receiving the retention part 5 can be seen from the drawing figures 2, 4 and 6. The corresponding molded parts or functional parts are shown on a greatly enlarged scale in the drawing figures 5 to 7. The recess 11 receiving the retention part has, for example, a height of 0.7 mm and a width of 1.4 to 1.45 mm. According to FIG. 7, the retention part 5 has a total height of 0.95 mm, the catch 6 being a hollow half ball is formed so that the desired spring action can be achieved not only via the legs 10 and the base 9, but also by an additional deformation of the hemisphere 6. The legs 10 protrude on the side facing away from the catch 6 by about 0.35 mm in the normal direction, the catch 6 projecting beyond the base by about 0.3 mm. The diverging legs 10 of the retention part 5 have a narrow edge 12 running parallel to the base 9, which is shown in the drawing figure 7 on an enlarged scale of 40: 1. The outer leg surfaces 13 adjoining the edge 12 form an angle of approximately 50 ° with one another. Their inner surfaces 14 adjoining the marginal edges 12 enclose a flat angle of 140 ° with one another and merge into a more acute angle of approximately 80 °, from where they open into the base 9. The width of the retention part 5 is approximately 1.3 to 1.35 mm. In the manufacture of the telescopic crown, the recess 11 for the retention part 5 and the locking recess 7 is in each case formed by a contour-matched, lost molded part 15 or 16, which molded parts are shown in the drawing figures 5 and 6. The molded part 6 for forming the recess 11 for the retention part 5 is essentially cuboid formed with an open top surface, wherein the narrow side surfaces 17 are formed to converge toward the top surface to form the undercut. The undercut thus formed ends laterally shortly before the connection to the longer side surfaces 18. Das

Shaped part 16 for forming the catch recess 7 for the catch 6 of the retention part 5 is formed by a rectangular plate with a central recess, as can be seen from FIG. 5. On the short edge edges of the plate protruding from the plate at right, protruding towards the top Haltetegege 19 are formed, which can be broken off at predetermined breaking points 20. The molded parts 15, 16 are modeled into the inner surface of the secondary crown 3 or the outer surface of the primary crown 2 and embedded together with the crown. The modeled material is removed by heat, and in addition the molded parts 15, 16, which consist of plastic which can be burned without residue, are completely removed. Metal is then poured into the mold, as a result of which the primary crown 2 and the secondary crown 3 are produced with the contours shown in FIG. The space between the undercut and the side walls 18, which can be seen in drawing figure 6, for example, serves to avoid air bubbles when the crown is embedded. These holding webs 19 of the molded part 16 are used so that this molded part can be modeled and arranged in the correct position with an auxiliary tool.

Claims

Claims 1. Telescopic crown, consisting of a primary crown that can be attached to a tooth stump and a secondary crown that can be slid onto it, with a resilient retention part being held in the inner wall of the secondary crown, which rests in a projection that protrudes the wall towards the outer wall of the primary crown a recess of the same shape in the outer wall of the primary crown in the desired position is inserted, characterized in that the retention part (5) is U-shaped, the base (9) of which carries the catch (6) at least approximately in the center and the latter Project leg (10) to the side facing away from the catch (6) and that the retention part (5) is inserted into a recess (11) in the inner wall of the secondary crown (3), on the side walls of which the leg (10 ) can be supported and the bottom of the spring travel of the detent (6) has a corresponding distance from the base (9) of the retention part (5). 2. Telescopic crown according to claim 1, characterized gekenn¬ characterized in that the detent (6) and the locking recess (7) are hemispherical. 3. telescopic crown according to claim 1, characterized gekenn¬ characterized in that the side walls of the recess (11) are undercut and the legs (10) are arranged under the undercuts. 4. Telescopic crown according to one of claims 1 to 3, characterized in that the cross-sectional shape of the recess (11) is dovetail-shaped and the legs (10) are inclined at the same angle. 5. Telescopic crown according to one of claims 1 to 4, characterized in that the catch (6) of the retention part (5) consists of metal. 6. Telescopic crown according to one of claims 1 to 5, characterized in that the retention part (5) consists of metal. 7. Telescopic crown according to one of claims 1 to 6, characterized in that the retention part (5) consists of plastic. 8. Telescopic crown according to one of claims 1 to 7, characterized in that the retention part (5) has an integrally molded catch (6). 9. Telescopic crown according to one of claims 1 to 8, characterized in that the retention part (5) receiving recess (11) has a height of about 0.7 to 1.1 mm, the Retentions¬ part (5) flush into the recess (11) can be used, the legs (10) of which have a free length of approximately 0.3 to 0.5 mm and the catch (6) protrudes by approximately 0.2 to 0.4 mm, in particular 0.3 mm. 10. Telescopic crown according to one of claims 1 to 9, characterized in that the diverging legs (10) of the retention part (5) have a narrow edge edge (12) running parallel to the base, their outer edge, to the edge edge (12) adjoining leg surfaces (13) enclose an angle of 50 ° with one another, their inner surfaces (14) adjoining the edge edges (12) enclose a flat angle of in particular 140 ° with one another and transitioning into an acute angle of approximately 80 ° Base (9) run. 11. Telescopic crown according to one of claims 1 to 10, characterized in that the width of the Reten¬ tion part (5) is about 1.1 to 1.5 mm, in particular 1.3 mm. 12.Telescopic crown according to one of claims 1 to 11, characterized in that the recess (11) for the retention part (5) and the locking recess (7) each by a contour-matched molded part (15 or 16), in particular from residue-free combustible plastic is formed. 13. Telescopic crown according to one of claims 1 to 12, characterized in that the molded part (15) for forming the recess (11) for the Retentions¬ part (5) is cuboid with an open cover surface aus¬, the narrow side surfaces (17) are formed to form the undercut to the top surface and the undercut shortly before connection to the longer side surfaces (18) ends. 14. Telescopic crown according to one of claims 1 to 13, characterized in that the shaped part (16) for forming the latching recess (7) is a rectangular plate with a central recess, with retaining webs (19) striving towards the top in particular at their short marginal edges. are integrally formed, which are connected to the plate in particular via predetermined breaking points (20).