U.S. patent application number 09/849838 was filed with the patent office on 2001-08-30 for fixture, prosthesis anchoring device and prosthesis.
This patent application is currently assigned to Medevelop AB. Invention is credited to Branemark, Per-Ingvar.
Application Number | 20010018176 09/849838 |
Document ID | / |
Family ID | 20403194 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010018176 |
Kind Code |
A1 |
Branemark, Per-Ingvar |
August 30, 2001 |
Fixture, prosthesis anchoring device and prosthesis
Abstract
The invention is related to an arrangement used to attach a
prosthesis to one or more fixtures (1) anchored in a person's bone
tissue. Such a fixture (1) has a fastening part (8) for the
prosthesis and said fastening part has a supporting surface the
prosthesis and a said fastening part has a supporting surface (9)
that engages a bearing surface (13) on the prosthesis. In
accordance with the first aspect of the invention such a fixture
(1) on its supporting surface (9) is provided with a deformation
device (18). This is plastically deformable in a direction
perpendicular to supporting surface (9) to compensate for any
misalignment between supporting surface (9) and bearing surface
(13). In accordance with a second aspect of the invention, the
deformation device is, instead, arranged on the prosthesis
supporting surface (13) in a corresponding way. The invention also
incorporates a prosthesis anchoring system that includes a fixture
having a deformation device.
Inventors: |
Branemark, Per-Ingvar;
(Molndal, SE) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
|
Assignee: |
Medevelop AB
|
Family ID: |
20403194 |
Appl. No.: |
09/849838 |
Filed: |
May 4, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09849838 |
May 4, 2001 |
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09214031 |
Mar 11, 1999 |
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09214031 |
Mar 11, 1999 |
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PCT/SE97/01035 |
Jun 12, 1997 |
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Current U.S.
Class: |
433/173 |
Current CPC
Class: |
A61C 8/0022 20130101;
A61C 8/0048 20130101 |
Class at
Publication: |
433/173 |
International
Class: |
A61C 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 1996 |
SE |
9602555-6 |
Claims
What is claimed is:
1. A prosthesis support fixture comprised of: a bone anchor; a
prosthesis attachment part extending from one end of the bone
anchor, the bone anchor and the prosthesis attachment part forming
an elongated unitary structure having a central axis; the
prosthesis attachment part including: a coupling element operative
to secure a prosthesis to the fixture; and an integral supporting
element including a planar surface substantially perpendicular to
the central axis for engagement with a bearing surface on a
prosthesis attachable to the fixture; the planar surface of the
supporting element being plastically deformable due to contact with
a bearing surface on a prosthesis while the prosthesis is being
secured to the fixture by the coupling element so that the force
applied by the bearing surface to the support fixture will
effectively be directed along the central axis when the prosthesis
is fully secured to the fixture.
2. A prosthesis support fixture as described in claim 1, in which
the supporting element is comprised of an axially extending flange
with an axially outer end thereof comprising the planar
surface.
3. A prosthesis support fixture as described in claim 2, in which
the flange includes a plurality of transverse slots.
4. A prosthesis support fixture as described in claim 1, in which
the supporting element is comprised of an axially extending annular
flange with an axially outer end thereof comprising the planar
surface.
5. A prosthesis support fixture as described in claim 4, in which
the flange includes a plurality of radial slots.
6. A prosthesis support fixture as described in claim 1, in which
the supporting element is comprised of an axially extending flange
having a beveled axially outer end thereof comprising the planar
surface.
7. A prosthesis support fixture as described in claim 1, in which
the supporting element is comprised of a radially extending flange
having an axially outer face thereof comprising the planar
surface.
8. A prosthesis support fixture as described in claim 1, further
including an annular slot spaced from the axially outer end
thereof, thus forming an annular flange, an axially outer face of
the flange comprising the planar surface.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation U.S. patent application Ser. No.
09/214,031 filed Mar. 11, 1999 in the name of Per-Ingvar Branemark
entitled FIXTURE, PROSTHESIS ANCHORING DEVICE AND PROSTHESIS as the
U.S. National Stage of PCT/SE97/01035 filed Jun. 12, 1997.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a fixture for implantation
and osseointegration with bone tissue whose purpose is to carry a
prosthesis, a prosthesis anchoring system, and a prosthesis
attached to the fixture.
[0004] 2. Description of the Related Art
[0005] It is known to implant fixtures in a person's bone tissue in
order to attach different types of prostheses to them, dental
prostheses for example.
[0006] To make certain that the fixture anchorages are permanent, a
number of factors must be fulfilled with regard to, among other
things, material selections and operation techniques. In practice,
fixtures developed by Professor Branemark made of pure titanium
with micro-pitted surfaces have shown very good long-term anchoring
abilities. The screw-shaped fixtures are operated into a bone, the
jawbone for example, and are permitted to heal
in--osseointegrate--for a certain time period, usually a few
months. Thereafter, a prosthesis can be mounted on the
fixtures.
[0007] Most types of these fixtures are provided with external
threads--and are thus implanted screws--and they are attached by
screwing them into holes made in the bone tissue. The holes are
often pre-threaded, but it is also possible to screw in
self-tapping screws. Normally, the fixtures require shorter or
longer times for healing-in before they should be exposed to
significant loads. On the fixtures, one can attach different types
of prostheses, and for dental prostheses one can attach individual
teeth, i.e., one tooth per fixture, but it is also possible for two
or more fixtures to serve as attachment points for a bridge
structure containing a number of teeth or even an entire row of
teeth. The fixtures are therefore designed in a suitable way at
their free ends.
[0008] The free end of such a fixture to which a prosthesis is to
be fastened, i.e., the fastening end, is equipped with some form of
fastening device that will engage a corresponding fastening device
on the prosthesis. It is herewith usual to have the attachment
arranged so that a bearing surface on the prosthesis or a
prosthesis-carrying element will be in contact with a supporting
surface on the fixture's fastening end. The supporting and bearing
surfaces should be parallel to ensure fully satisfactory
functionality. This seldom poses any problem for prostheses of the
type that are attached by means of only one fixture since in such
cases the prosthesis, which is usually fastened by a threaded joint
to the fixture, will have its bearing surface forced into contact
with the fixturets supporting surface throughout its entire area
when the prosthesis is screwed into place.
[0009] In many cases, a prosthesis can be anchored using more than
one fixture. This is especially true in connection with jaw
reconstruction when a prosthesis containing a row of teeth is to be
attached, but it can also occur for prostheses used for other parts
of the body.
[0010] When such a prosthesis or a holder for such a prosthesis is
to be attached to two or more fixtures, the fixture onto which the
prosthesis is first attached and screwed into place will force the
prosthesis into a certain position as a result of the fact that its
bearing surface, which is pressed against the fixture's supporting
surface will forcibly have its direction determined by said
supporting surface. For screwing a prosthesis to the second fixture
and to additional fixtures if any, it is desirable that the
corresponding bearing and supporting surfaces on this/these
fixture(s) also be parallel so that there will be no misalignment.
When anchoring fixtures in bone tissue one tries, of course, to
have the supporting surfaces assume their intended directions
relative to each other with the greatest possible precision, and
these directions should be adapted to the corresponding bearing
surfaces on the prosthesis. Usually the fixture surfaces are to lie
in the same plane or at least be parallel.
[0011] To fully achieve this is very difficult, and it must be
expected that an anchored fixture will deviate directionally from
what is intended. Anchoring two or more fixtures fully parallel is
also very difficult, and the possibility of obtaining precisely
matching heights is remote. A deviation of even a mere degree or so
results in a deficient fit between the supporting surfaces and
bearing surfaces when a prosthesis, as described above, is attached
to the fixtures. Since the prosthesis element or prosthesis holder
is generally made from a completely rigid material such as
stainless steel, a faulty fit cannot be compensated for by
deforming the element or holder. Instead, there is poor contact
with one or more of the fixtures' supporting surfaces and strains
develop in the prosthesis structure when one tightens the threaded
joint to attach the prosthesis to the fixtures. Moreover, these
strains are propagated down into the bone tissue. This can cause
discomfort and trouble for the patient while detracting from the
functionality of the prosthesis and shortening its life
expectancy.
[0012] This problem is especially common in connection with jaw
reconstruction where a superstructure with a dental prosthesis is
screwed in place on the fixtures directly or via an attachment bar.
Such a lack of parallelism among the fixtures poses a major
problem, particularly in connection with the use of prefabricated
superstructures not intended for extensive individual adaptation.
In order to compensate for this non-accuracy it is earlier known
e.g. from EP 0126 624, EP 0370 590 and EP 0466 267 to provide an
intermediate elastic device between the fixture and the
prosthesis.
SUMMARY OF THE INVENTION
[0013] The present invention eliminates the disadvantages described
above that are encountered when the directions of the fixtures
and/or their height positions do not fully match what was intended,
and without inserting special compensation elements.
[0014] In accordance with the invention, this has been achieved by
means of a fixture for implantation and osseointegration with bone
tissue whose purpose is to carry a prosthesis, by means of a
prosthesis anchoring device having a prosthesis base that engages
the fixture, and by means of a prosthesis containing a number of
attachment units arranged integrally with the prosthesis or with a
separate prosthesis base, where each attachment unit is arranged to
be attached to a fixture anchored in a person's bone tissue, and
also containing a bearing surface arranged so that when the
prosthesis is attached to said fixtures, the bearing surface will
be in contact with a supporting surface on the appropriate fixture,
the bearing surface and the supporting surface both being
substantially perpendicular to a center axis of a related fixture
wherein at least one of said bearing surfaces is provided with a
deformation device that is deformable in at least one direction
that is perpendicular to the bearing surface to attain absolute
parallelity between the supporting surface and the bearing surface
when the bearing surface is pressed against the supporting
surface..
[0015] Because the supporting surface on the fixture or the bearing
surface on the prosthesis is integrally provided with a deformation
device that can be deformed plastically in a direction
perpendicular to the respective surface when misalignment occurs,
the deformation device will be deformed to a corresponding extent.
As a result, the bearing surface will have a fully functional
contact with the supporting surface in spite of the misalignment.
Since angular misalignment is absorbed by such deformation devices,
the tightening of the retainer screws will not implement any
strains in the patient's bone tissue.
[0016] The fixture is preferably designed with at least parts that
are rotationally symmetrical, wherewith its supporting surface is
perpendicular to its center axis.
[0017] Other features and advantages of the present invention will
become apparent from the following description of the invention
which refers to the accompanying drawings.
[0018] In one preferable embodiment, the deformation device is
designed as an axially aligned flange, suitably cylindrical and
coaxial with the center axis.
[0019] It is preferred that the flange be peripherally arranged on
a circular supporting surface to provide optimal deformation
distribution. This will occur as a result of the fact that the
flange will then be located at as long a distance as possible from
the center axis.
[0020] In other preferred embodiments, the flange is provided with
slots and/or is beveled axially outward, thereby facilitating
deformation.
[0021] Moreover, it is preferred that the flange's outer end be
pointed, i.e. sharp, thus providing progressive resistance to
deformation.
[0022] The above and other preferred embodiments of the invention
are set forth in the dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The invention is explained in greater detail in the
following detailed description of the invention with reference to
the accompanying figures, of which:
[0024] FIG. 1 presents a rough sketch of the known technique.
[0025] FIG. 2 is a partially sectioned side view of a fixture in
accordance with a first embodiment.
[0026] FIG. 3 is a perspective view of a part of the fixture shown
in FIG. 2.
[0027] FIG. 4 is an enlarged section taken through a part shown in
FIG. 3.
[0028] FIGS. 5-7 are sections that correspond with what is shown in
FIG. 4, illustrating the second through the fifth embodiments of
the invention.
[0029] FIG. 8 is an end view of a fixture in accordance with a
sixth embodiment of the invention.
[0030] FIG. 9 is a perspective view of a part shown in FIG. 8.
[0031] FIG. 10 is an exploded view of a prosthesis anchoring device
in accordance with the invention.
[0032] FIG. 11 is a longitudinal section taken through a part shown
in FIG. 10.
[0033] FIG. 12 is a side view of a part in a prosthesis in
accordance with the invention.
[0034] FIG. 13 is an end view of a part shown in FIG. 12.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0035] The purpose of FIG. 1 is to clarify the set of problems that
the present invention is intended to solve, and it is therefore
drawn in schematic form. 101 represents a part of a prosthesis, a
bridge base for a dental bridge, for example. Prosthesis part 101
is anchored in a person's jawbone by means of a number of fixtures
screwed into holes made in the jawbone. Only two fixtures 102, 103
are shown in the figure, and only their upper ends are shown. Each
fixture acquires a direction determined by the hole in the jawbone
in which it is anchored. Quite frequently, these holes are not
fully parallel, which leads to corresponding mutual misalignment of
fixtures 102, 103. Prosthesis part 101, when it is tightened
against the first fixture, is forced into a position determined by
the direction of the first fixture's supporting surface 104 when
the corresponding bearing surface 105 on prosthesis part 101 is
drawn into contact with supporting surface 104.
[0036] If, then, the second fixture 103 has an angular deviation
from parallelism with the first fixture 102, the tightening of the
threaded joint located at the second fixture 103 will lead to a
misalignment of the second fixture's supporting surface 106
relative to the corresponding bearing surface 107 on the prostheses
part so that contact will be almost of the point-to-point type, as
shown at 108. When both fixtures are tightened against prosthesis
part 101, torque will be developed on each fixture in the
directions shown by the arrows. Such torque will create strains in
the jawbone where the fixtures are anchored. The harmful effects of
this are mentioned in the introduction to the 98.1 description.
Similar problems are encountered if the positions of the bearing
surfaces of the fixtures do not match with regard to height.
[0037] FIG. 2 shows a fixture 1 according to the present invention
with its anchoring end anchored in a person's lower jawbone 2. At
the upper end of fixture 1, its fastening end, there is a base such
as a bar 3 intended to carry a dental prosthesis bridge (not shown)
attached to it.
[0038] Fixture anchoring part 7 is conventionally designed with a
threaded part 4 which, at its end, has a conical part 5 provided
with slots 6. Anchoring part 7, which is made of titanium, is
self-tappingly screwed into a pre-drilled hole in jawbone 2. The
upper end, the fastening end, of the fixture, comprises a spacer
part 8 which can be combined with anchoring part 7 to form a single
piece or more commonly, arranged as a separate unit that is screwed
into an anchoring part 7 that has been provided with an internally
threaded bore (not shown in FIG. 2).
[0039] The fastening end is provided with an attachment unit that
engages another attachment unit adapted to it on bar 3, whereupon
the two are attached together. The fastening end's attachment unit
contains a supporting surface 9 arranged perpendicularly to the
fixture's longitudinal axis A, an axially aligned projection 10
extending out from supporting surface 9, the projection having a
hexagonal outer profile, and an internally threaded bore 12 in the
fixture that is axially aligned relative to the top of the
projection. The corresponding attachment unit for bar 3 includes a
section of its bottom surface that comprises bearing surface 13, a
through-going bore 14, a cylindrical countersink 15 at the upper
end of the bore, a hexagonal countersink 16 at the lower end of the
bore and a retainer screw 17.
[0040] Bar 3 defines a direction that is dependent on the direction
of a first (not shown) fixture as described in connection with FIG.
1. As mentioned previously, an effort is made to see that normal
alignment B of this direction will correspond to the shown
direction A of fixture 1. Such is not the case in FIG. 1. Instead,
there is an angular deviation of a.degree. between them. A
corresponding angular deviation also occurs between supporting
surface 9 and bearing surface 13.
[0041] The bearing surface 9 is provided with a deformation device
in the form of a flange 18 that is arranged at the periphery of
bearing surface 9 and extends axially out from it. The flange is
relatively thin, about 0.05 mm, and has a height of about 0.15 mm.
When fixture 1 is pulled firmly onto bar 3 by tightening screw 17,
the part of the fixture's supporting surface that consists of the
flange will come into direct contact with bearing surface 13 on bar
3. Since the surfaces are not parallel, contact occurs initially at
a single point on flange 18. Continued tightening of the screw
deforms flange 18 at this location, and when the screw is tightened
further, this deformation extends throughout more and more of
flange 18. Because the deformation is plastic, the change in shape
is retained. The left side of the figure shows the flange deformed
in this way at 19. The deformed flange will acquire an end surface
that is parallel with bearing surface 13 on bar 3 and contact it
throughout its entire extent. Compensation has thus been obtained
for angular deviation a so that there is good contact between
fixture 1 and bar 3 and so that no strains develop in jawbone
2.
[0042] FIG. 3 presents a perspective view of the upper end of
fixture 1. This also shows how the spacer part 8 can be attached to
its anchoring part 7 by means of a threaded bore 20 represented by
broken lines that engages a corresponding threaded stud-end (not
shown) on spacer part 8. FIG. 3 also shows clearly how, at the
upper end of spacer part 8, an axial flange 18 provided at the
periphery of supporting surface 9 is shaped. This is also shown by
FIG. 4, which shows a section taken through the flange and drawn to
a larger scale. Flange 18 is, in this embodiment, uniformly thick
and is terminated with a part that is perpendicular to the axial
direction.
[0043] The embodiments shown in FIGS. 5 and 6 differ from what is
shown in FIG. 4 due to the fact that the outer ends of flanges 18a
and 18b are provided with bevels 21a, 21b on their inner side and
outer side respectively. These bevels extend, in both cases, across
the entire width of the flanges so that a pointed, i.e., sharp,
edge is form at the outer end. The bevels can, of course, be
arranged differently so that they extend over only a part of the
width of the flange, leaving a flat edge surface at the outer end
of the flange. Similarly, the flange can be provided with a bevel
on both the inner and outer sides. Beveling keeps the resistance to
deformation relatively low when initial contact is made. Resistance
then increases more and more as the screw is tightened.
[0044] In FIG. 7, the deformation device comprises a flange 18c
which is radially aligned, wherewith a radially aligned circular
slot 22 around spacer part 8 separates flange 18c axially from the
rest of spacer part 8. Flange 18c is deformed when pressure is
brought to bear on a point farthest out on its top side, since it
is then bent downward towards slot 22 as indicated by the chain
lines.
[0045] In the embodiment shown in FIG. 8, flange 18e is provided
with slots 23 which facilitate deformation of flange 18e. These are
drawn to a larger scale in FIG. 9. Slots 23 can, as shown in FIG.
8, extend axially throughout the entire flange 18e or, as shown in
FIG. 9, extend only throughout a part of its axial extent. In the
latter case, a lower initial deformation resistance is
obtained.
[0046] FIG. 10 presents a dental prosthesis system for which the
invention's advantages are of special importance. The dental
prosthesis system includes a superstructure with a bridge 30 that
is provided with dental prostheses and a bar 4 to which bridge 30
is attached by means of a number of screws 31 in threaded holes 32
in bar 4. Bar 4 is anchored in a person's jawbone via three
fixtures 1 to which bar 4 is attached by means of a number of
screws 17, each of which is passed through a hole 14 in the bar and
screwed into a threaded bore in the appropriate fixture 1. Each
fixture's supporting surface 9 will come into contact with a
corresponding bearing surface 13 on bar 4, and any angular
deviations will be taken up, in the manner described previously, by
flange 18 which is shown in FIG. 11.
[0047] FIG. 12 is a side view of a bar 4' which is of a type
similar to that previously described, but it shows an alternative
embodiment of the invention. Each of the individual bearing
surfaces 13' is located adjacent to a fastening hole 14' on the
bottom side of the bar. Each bearing surface 13' is provided with
an axially aligned flange 18' that is concentric with fastening
hole 14'. FIG. 13 shows, in an enlarged end view, how this flange
18' is arranged. Flange 18', in this embodiment of the invention,
replaces the corresponding flange in the previously described
embodiments. Here, deformation is absorbed by a deformation device
on the bearing surface 13' of bar 4' instead of being taken up by
such a device on the supporting surface of the fixture. In other
respects, since the arrangement shown for this embodiment functions
in the same way as described previously, further description is
omitted. It should be understood that the deformation device shaped
as flange 18' in this embodiment can be modified in the different
ways set forth for the previously described embodiments in which
the deformation devices are located on fixtures.
[0048] Although the present invention has been described in
relation to particular embodiments thereof, many other variations
and modifications and other uses will become apparent to those
skilled in the art. It is preferred, therefore, that the present
invention be limited not by the specific disclosure herein, but
only by the appended claims.
* * * * *