WO2013118153A1

WO2013118153A1 - Improved dental prosthesis and anti-loosening device for said prosthesis

Info

Publication number: WO2013118153A1
Application number: PCT/IT2012/000043
Authority: WO
Inventors: Bernardo MANFRÈ
Original assignee: Biotech S.R.L.
Priority date: 2012-02-07
Filing date: 2012-02-07
Publication date: 2013-08-15

Abstract

The present invention relates to a fixed dental prosthesis (1), comprising: an implant (5) intended to be fitted into a bone of a patient, an abutment (4) connectable with said implant (5), a screw member (2) for coupling said abutment (4) with said implant (5) and, a washer (3) fittable between said screw member (2) and said abutment (4), wherein the screw member (2 ) and the abutment (4) comprise respective areas (2C, 4E) coupling with the washer (3) that are shaped such to increase friction and to cause the washer to be deformed in the mounted condition.

Description

IMPROVED DENTAL PROSTHESIS AND ANTI-LOOSENING DEVICE FOR SAID PROSTHESIS

DESCRIPTION

TECHNICAL FIELD

The present invention relates to the dental field, more specifically it applies to fixed dental prostheses that require the use of the implantology technique.

STATE OF THE ART

The so called "screwed fixed prosthesis" subject of the present invention comprises elements made of metallic material that, once coupled to each other, form such prosthesis.

More in detail the fixed prosthesis comprises a first root portion, otherwise called as "implant", intended to be inserted into the bone of the patient, in order to replace the missing tooth root (because generally it is removed).

The prosthesis also comprises a second portion, commonly called, in the technical jargon, with the English term "abutment", usually made of metallic or ceramic material.

The first and second portions are fastened to each other by a tightening screw. The prosthesis finally comprises a third portion, called "crown" that is fastened on the abutment, and that constitutes the artificial reconstruction of the missing tooth.

This prosthetic technique has a still unresolved drawback: the risk of breakage of the screw or of the abutment during the tightening phase carried out by the dentist and the loosening of the prosthesis, a circumstance that results in the instability thereof and consequently resulting in serious discomforts for the patient .

Such drawback has to be found in inaccuracies in the contact generated between the seat housing the screw inside the abutment and the head of the tightening screw, which are particularly influential in these systems that provide flat surfaces to be faced coupled, which do not succeed in being perfectly planar to each other.

The inaccuracies in the contact, during the mastication phase of the patient, produce imperceptible movements that trigger the process of destabilization of the prosthesis with the risk of breaking it.

This drawback is made worse if one considers that the most widely used materials in prosthesis implantology are Titanium and Zirconium Oxide. Such materials have basic features for the dentistry application: biocompatibility, strength and aesthetic appearance with particular reference to Zirconium Oxide.

However, such materials, in the coupling phase of the connections, are particularly subjected to the drawbacks described above, such as the risk of breaking the screw in the phase for tightening or loosening the prosthesis.

^• Particularly, this regards at the greatest extent Zirconium Oxide, whose use, when matched with materials of different nature, has found an obstacle mainly due to the intrinsic characteristic of Zirconia material, which appears to be particularly weak to shearing forces and therefore it is more subjected to the risk of breakage or loosening of the prosthesis.

Thus, the coupling of the three components of the fixed prosthesis (implant, abutment and screw) by the technique described above, represents a critical issue of the modern implantology that unfortunately is still unsolved, because the pressure exerted by the chewing forces acting in different directions on the prosthesis causes the connections to become loose over time, leading to serious inconveniences for the patients and still leaving the drawback related to the loosening of the abutment unsolved.

A first solution to this state of things is that of tightening the screw of the abutment with a quite high force and approximately equal to 30 Newton: however for the reasons described above this solution has not proved to be satisfactory, because it does not completely solve the drawbacks related to the mastication and it involves a high risk of breakage of the implant components, in particular with reference to the abutments made of Zirconium Oxide for the reasons mentioned above.

Another, quite recent, solution is described in U.S. patent application US2003/ 224330 that describes the use of a gold washer placed between the abutment and the titanium screw head: the different hardness of the materials leads to the deformation of the washer and it tries to prevent a possible loosening of the prosthesis.

This solution, although valid in a general sense, forces to use specific materials, leaving little free space for different solutions.

Another system providing the use of a washer is described in the international application WO2010116330: this document teaches how to produce a prosthesis comprising an implant, an abutment, a crown and a retaining screw wherein a washer is provided to be used which comprises a low friction polymeric material and that is rotatably arranged adjacent to the head of the screw so as to reduce friction between the head of the screw and the base of the implant when the screw is tightened.

The fact that the washer is made of polymeric material, allows the screw to be tightened in a better way but at the same time it accentuates the drawbacks related to the loosening of the screw when using the prosthesis and therefore it is not a solution to the drawbacks mentioned above.

Still another system using a washer is the one described in the international application WO2010058358: in this case the washer comprises a shape memory material whose properties are used in order to allow the washer to exert a return force, after being deformed, on the screw head, such to prevent it from being loosened.

This solution, like the one described in US2003/ 224330, however, forces to select materials that both have shape memory and that are highly biocompatible, actually reducing the selection to few materials, such as for example Nitinol or the like.

Moreover, in all the systems described here the reaction to micro-movements produced during the mastication is not optimal and the loosening of the screw is always possible.

OBJECT AND SUMMARY OF THE INVENTION

The object of the present invention is to overcome the prior art drawbacks.

In particular, the object of the present invention is to obtain an effective tightening of fixed prostheses in the implant application.

This result is achieved by the use of a washer between the implant and the abutment or more precisely between the abutment and the head of the screw member, which comprise respective areas coupling with the washer that are shaped such to increase friction and such to cause the washer to be deformed when in the mounted condition.

Thanks to this solution the washer acts as a deformable element able to compensate the inaccuracies in the contact of the coupled flat surfaces (coupling areas) in order to ensure an optimum planarity.

Furthermore the washer also acts with a buffer function, since it absorbs micro-movements and vibrations caused by the mastication, thus ensuring an effective tightening of the prosthesis and therefore preventing it from being loosened.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described here below with reference to non-limitative examples, provided for explanation and not limitative purposes in the attached drawings. These drawings show different aspects and embodiments of the present invention and, where appropriate, reference numbers showing similar structures, components, materials and/or elements in different figures are denoted by similar reference numbers.

— Figure 1 is an exploded view of the prosthesis of the present invention,

— Figure 2 is a side view of the screw member of the prosthesis of fig.l,

— Figure 3 is a front view of the screw member of Fig. 2,

— Figure 4 is a sectional view of the abutment of the prosthesis of fig.l, — Figure 5 is a front view of the abutment of Fig. 4,

— Figs. 6 and 7 are an exploded side and sectional view of the prosthesis of

Fig-

— Figs. 8 and 9 are a side and sectional view of the prosthesis of Fig. 1 in the assembled condition,

— Figure 10 is an enlarged detail of fig. 9,

— Fig. 11 is the washer of the present invention,

— Figs. 12-14 are different alternative embodiment of the abutment of the prosthesis of the present invention

— Fig. 15 is an enlarged detail of the abutment of figg. 12-14.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is susceptible to various modifications and alternative forms, some relevant illustrated embodiments are shown in the drawings and will be described below in detail.

It should be understood, however, that there is no intention to limit the invention to the specific embodiment illustrated, but, on the contrary, the invention intends to cover all modifications, alternative forms, and equivalents falling within the scope of the invention as defined in the claims.

The use of "for example", "etc.", "or" indicates not-exclusive alternatives without limitation unless otherwise noted. The use of "including" means "including, but not limited to" unless otherwise noted.

With reference to the attached drawings, therein is shown a fixed dental prosthesis denoted in its entirety by reference number 1.

The prosthesis 1 comprises an implant 5 intended to be inserted into a bone of a patient, an abutment 4 connectable with the implant 5, a fastening screw member 2 for coupling the abutment 4 with the implant 5 and a washer 3 fittable between the screw member 2 and the abutment 4.

According to the teachings provided herein, the screw member 2 and the abutment 4 particularly comprise respective areas 2C, 4E coupling with the washer 3 which have such a shape to increase friction and to cause the washer to be deformed in the mounted condition.

Such coupling areas, when the prosthesis 1 is assembled, face the washer 3, as it is clearly shown in the attached figures.

In more detail and with reference to figs. 2, 3 and 9, the screw member 2 is a screw comprising an enlarged head 2A and a body 2B, 2D between which an annular shoulder 2C of the head 2A is comprised, which is arranged at the region of the latter facing the body 2B, 2D.

The latter comprises a threaded area 2B and a non-threaded one 2D next to the head 2A.

The coupling shaped area of the screw 2 is formed at the annular shoulder 2C, such that in the assembled condition it faces the washer 3.

Now with reference to the abutment 4 in figs. 4, 5 and 9 it has to be noted that it comprises a hollow inner area 4D wherein an annular shoulder 4E is defined.

In particular the annular shoulder 4E is arranged such to divide a threaded section 4C of the abutment 4, wherein the screw member 2 is engaged from a non- threaded section 4A, upon which a crown (not shown) is fitted which usually has the external shape of a tooth.

The coupling shaped area of the abutment 4 is formed at the annular shoulder 2C, such that in the assembled condition it faces the washer 3.

Observing in detail the figures 3 and 5 it has to be noted that in the present example the shape of the coupling area 2C comprises ridges, while the shapes of the coupling area 4E of the abutment 4 comprise a plurality of micro-depressions.

In this embodiment the micro-depressions 4F include rounded grooves; in other embodiment, like the one of figures 12-15, micro-depressions 4F' comprises substantially rectilinear grooves, having a V cross-section.

Generally speaking, micro-depressions 4F, 4F are preferably arranged in a radially shape on area 4E and extend over whole or only part of that area; a partial extension provides that micro-depressions extend radially for a distance between 80% and 99% of the area 4E.

The depth of the micro-depressions can vary depending on needs, experiments conducted by the Applicant provides that the depth of the grooves is preferably between 0.01 and 0.2 mm.

With reference to the washer 3, it is made of a material less hard than that of the screw 2 and of the abutment 4, such to be the deformable element during the tightening.

This allows, during the tightening action, the washer 3 to be deformed whose material fills at least partially the cavities between the ridges and the micro- depressions, it being able to achieve the technical planarity requirement, and to better retain the screw 2 from loosening.

In particular, the washer 3 comprises one of the following: gold or platinum or palladium or rhodium or titanium or silver or aluminium; preferably the abutment 4 is made of zirconium oxide.

The presence of ridges and micro-depressions allows the washer 3 to be deformed at a greater extent and therefore it allows a more effective tightening.

Preferably the washer 3 is annular and it has a diameter equal to the shoulder 2C and to shoulder 4E such to completely occupy the space between the abutment 4 and the screw 2 in the mounted condition, by resting also on the inner side shell wall of the recess 4D to further improve the sealing.

The provision of the washer 3 allows a screwing operation with a higher tightening force than that usually recommended with the abutment 4 made of Titanium or Zirconia, since forces are distributed in a uniform manner.

Thus the above mentioned objects are achieved.

Claims

1. Fixed dental prosthesis (1), comprising:

- an implant (5) intended to be inserted into a bone of a patient,

- an abutment (4) connectable with said implant (5)

- a fastening screw member (2) for coupling said abutment (4) with said implant (5)

- a washer (3) fittable between said screw member (2) and said abutment (4) characterized in that

said screw member (2) and said abutment (4) comprise respective areas (2C,

4E) coupling with said washer (3), said coupling areas (2C, 4E) being shaped such to increase friction and to cause the washer to be deformed in the mounted condition.

2. Dental prosthesis (1) according to claim 1, wherein said screw member (2) comprises an enlarged head (2A) and a body (2B, 2D) between which an annular shoulder (2C) of said head (2A) is comprised in the area of the latter facing the body (2B, 2D), said shaped coupling area of said screw member (2) being made at said annular shoulder (2C).

3. Dental prosthesis (1) according to claim 1 or 2, wherein said abutment (4) comprises a hollow inner region (4D) wherein an annular shoulder (4E) is defined, said shaped coupling area of said abutment (4) being made at said annular shoulder (2C).

4. Dental prosthesis (1) according to one or more of the preceding claims, wherein said shaped coupling area (2C) of said screw member (2) comprises ridges.

5. Dental prosthesis (1) according to one or more of the preceding claims, wherein said shaped coupling area (4E) of said abutment (4) comprises a plurality of micro-depressions.

6. Dental prosthesis (1) according to one or more of the preceding claims, wherein said washer (3) is made of a material comprising one of the following: gold or platinum or palladium or rhodium or titanium or silver or aluminium.

7. Dental prosthesis (1) according to one or more of the preceding claims, wherein said abutment (4) is made of zirconium oxide.