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Description  |
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FIELD OF THE INVENTION
The field of the invention is that of enossal implants.
BACKGROUND OF THE INVENTION
Enossal implants, also known as endosteal or endosseous implants, are being
applied to an increasing extent in order to establish a long-lasting
partial or full prosthesis in the jaw of the patient. In this way, a fully
functional tooth replacement is provided, which enables the patient to
chew food without difficulty, thus fulfilling a very important health
function. Thorough chewing, particularly of raw foods and relatively tough
foods such as whole-grain bread, is an important preliminary stage in the
digestive process. It must be considered that a poorly seated partial or
full prosthesis is accompanied by the risk that, due to chewing
difficulties, the patient will not consume sufficient quantities of
physiologically important foods such as fresh salads, fruit, and
vegetables.
In known implants, the tooth replacement is bolted with a fastening head,
in which a screw, starting from the chewing surface of the tooth or
denture, is screwed into a prepared threaded bore of the fastening head.
It has been demonstrated that a simple screw connection of this type is not
adequate in many cases to secure the tooth replacement to the fastening
head, since the screws have the tendency to loosen due to the alternating
loads of chewing motions, so that the patient has to seek out his dentist
to have the tooth replacement newly fastened. Particularly disturbing is
when the loosening screw connection involves a single tooth since the
tooth can twist, leading to damage to the tooth and/or to its opposite
situated tooth.
SUMMARY OF THE INVENTION
An objective of the invention is to produce an improved implant, in which
no danger exists that the screw connection between the tooth replacement
and the fastening head will loosen.
This objective is fulfilled by the fact that the provision of a fastening
head attached to a first end of the implant post, the first end being that
end of the implant post which is turned away from the base body. The
fastening head is fitted with a fitting surface tapered in the direction
of the tooth replacement.
High frictional forces between the fitting surface and the opposite surface
in the tooth replacement, due to a tapered fitting surface on the
fastening head, on the one hand, and a corresponding opposite surface in
the tooth replacement on the other hand, are achieved when mounting the
tooth replacement. These frictional forces prevent later relative motion
between the tooth replacement and fastening head, so that undesired
loosening of the fitting connection can no longer occur, largely due to
the wedge effect of the fitting connection which can be additionally
secured by a adhesive or screw connection between the fastening head and
the tooth replacement.
It has been shown to be advantageous if the fitting surface has a conical
surface tapered in the direction of the tooth replacement and mates with a
corresponding cone/taper surface on the tooth replacement. This type of
conical surface can be relatively large and, additionally, provides a
method of centering the tooth replacement in relation to the fastening
head.
It has further been shown to be favorable if the implant post is detachable
and can be connected to the base body by means of an elastic, deformable
middle element. This way, the risk of relative motions between the tooth
replacement and the fastening head are further reduced since the forces
acting on the tooth replacement are taken by the elastic deformation of
the middle element, so that the fitted connection cannot loosen.
In regard to the elastic, deformable middle element, it is preferably
manufactured from a viscous-elastic synthetic, which, in conjunction with
geometrical measurements of the middle element, permits simulation of the
natural tooth movement between the base body healed into the jaw bone and
the tooth replacement, or in some cases, the implant post.
The implant post can also be manufactured as part of a one-piece fastening
head from a similar viscous-elastic synthetic, in which case the implant
post is so constructed that its elastic deformation due to acting forces
is essentially outside the elastic range of the fastening head, so that
relative motions between the tooth replacement and the fastening head are
kept to a minimum. This is not essential, however, in view of the
durability of the screw connection, since the deformability of the implant
post or fastening head material results in a particularly close fit or
wedging of the fitting surfaces, and the smallest tolerances between the
fitting surfaces are themselves fully balanced out by the corresponding
deformation of the synthetic material during the installation of the screw
connection.
In regard to making the connection between the base body and the implant
post, a number of advantageous possibilities exist according to the
invention.
In one method, the implant post and/or middle element has a cylindrical or
slightly conical surface on the end facing the base body, in order to
anchor the implant post in the base body. In this case, similar fitted
connection can be applied as in the case of the fastening head and tooth
replacement.
Another advantageous possibility is to bolt the implant post, or as
applicable, the inserted middle element, to the base body. Such a screwed
connection is particularly secure if, in addition, mating fitted surfaces
are provided on the base body and the implant post or middle element.
Another configuration of the invention provides the possibility of a
bayonet type connection between the implant post/middle element and the
base body. In this case, the elasticity of the middle element and/or the
implant post is ensured by the axial mobility of the elements of the
bayonet connection.
Otherwise, the following is to be noted in regard to anchoring the implant
post:
If the invention preferably involves an enossal implant, in particular
where the implant post is connected by means of a middle element to an
invention-specific base body, it is quite possible to apply other implants
or natural tooth roots as the base body, particularly with the use of
implant posts with cylindrical or slightly conical fitting surfaces. In
the latter case of natural tooth roots, these must be provided with
cylindrical or slightly conical surfaces by means of cement or glue or
alone through frictional forces in order to create the conical fit of the
required connection. In addition, a bayonet type connection between the
implant post and the base body healed into the bone has proven to be
particularly favorable, as is further detailed below.
In development of the invention, it has proven to be advantageous to use a
spacer bushing which has a center band and is installed in the open upper
end of the base body after it has healed, and thereby provides a shoulder
on the upper edge of the base body. By means of the spacer bushing, an
extension of the base body is obtained, which is very advantageous for
several reasons which are further detailed below.
An implant, according to this invention, with a base body, a spacer
bushing, an elastic deformable middle element, and an implant post with
fastening head, proceeds such that the metal base body is allowed to heal
into the bone in an exact fitting boring of the jaw-bone. Bordering on the
boring, one or more slit shaped extensions may be provided for accepting
lateral wings of the, in principle, cylindrical base body. The spacer
bushing with center band is then installed in the healed-in base body of
the implant, such that its shoulder rests on the upper edge of the base
body. Then, the elastic deformable middle element, with a shoulder that
rests on the upper edge of the spacer bushing, is screwed into the female
thread of the base body. Subsequently, the implant post, which rests with
one shoulder on the upper side of the middle element and above the
shoulder is fitted with a fastening head with a preferably conical fitting
surface, is screwed into the middle element. The fastening head has a
threaded boring, into which, for example, a crown may be screwed, whereby
the fastening screw grasps the crown material starting from the chewing
surface and screws into the female thread of the fastening head. The
fastening head of the implant post serves to fasten the tooth replacement,
which can be a single tooth (a crown), a bridge or a partial or full
prosthesis. One or more additional implants are used to fasten larger
partial or full prostheses. A particular advantage of the spacer bushing,
in this case, is the fact that it extends the base body, which heals into
the gums, past the upper edge of the gums, so that they are not irritated
by the deformation motions allowed by the elastic deformable middle
element.
In the implant according to this invention, the implant post may be
replaced by an impression post during the creation of an impression of the
jaw and/or teeth, necessary for preparing the tooth replacement. The
middle element and spacer bushing are also replaced with this impression
post.
It has been shown that during the preparation of a model in the dental
laboratory on the basis of such an impression, the axis of the fastening
head, already fixed by the axis of the rigid, healed base body, is usually
not optimal. The fastening head should be exactly in the middle of the
chewing surface of the tooth, if possible. On the other hand, since the
tooth replacement must be properly positioned in relation to the patient's
other teeth or previous tooth replacements, often there has been no other
choice than to place the screw in another, less favorable location on the
tooth replacement. Also, attempts to solve this problem by using a
deformable collar between the base body of the implant and the fastening
head have not been successful, since the collar is often inclined to
undesirable deformations later during loading of the tooth replacement.
Starting with the above described difficulties, an additional objective of
the invention is to provide a simple method for optimally positioning the
longitudinal axis of the fastening head in relation to the longitudinal
axis of the base body during work on the model, that is, during exact
positioning of the tooth replacement in view of the tooth and jaw
relationship of the particular patient.
This objective is solved in an advantageous manner in that the fastening
devices are fitted with a ball and socket joint with a ball part and a
socket that can swivel in relation to the ball.
It is an advantage of an implant according to this invention that a fine
adjustment of the fastening head relative to the base body can be achieved
with the aid of the ball-socket joint, so that divergences between the
base body axis and the required position of the fastening head can be
corrected. This was previously not possible since, on the one hand, the
positioning and orientation of the base body and fastening head were
firmly predefined, while, on the other hand, the positioning of the tooth
replacement and the fastening head permitted no fine adjustment. (In
principle, the ball joint could, for example, be connected in one piece
with the base body of the implant; such a configuration would hardly find
application in practice, since it has proven advantageous to fasten the
fastening head to the base body of the implant only after it has healed
rigidly into the bone.)
In an advantageous configuration of the invention, an implant includes a
ball joint at the end of the implant post turned away from the base body.
The implant post has a fastening head and the system includes fastening
devices in the form of a detachable, deformable middle element connected
to the base body. This is best accomplished when the end of the implant
post turned away from the base body is fitted with the ball part that is
connected detachably to the tooth replacement. This type of configuration
allows the possibility during modeling to optimally locate the axis of the
fastening head for fastening the tooth replacement to the base body, on
the one hand, and optimally positioning it in relation to natural teeth or
other implants, on the other, or also for exact fitting of a single tooth.
When the correct axis position of the fastening head is found, then the
socket is rigidly attached to the ball part; the ball joint is actually
blocked in connection with orienting the axis of the fastening head.
There are basically several methods for establishing a movable connection
between the ball part and socket part. For example, a screw connection may
be used that allows a prescribed free play within limits and thereby
adjustable positioning of the ball and socket, which is then fixed by
tightening the screw in the desired position. It is particularly favorable
if the socket part is form fitted to the ball part in such a way that the
socket is bent radially inwards by shaping with a rolling tool. It can
then grasp from behind the mid-axis (equator) of the ball part. In this
manner, a one-piece construction of the socket is possible and the ball
joint thus requires a total of two elements, namely the ball part and the
socket part. Aside from deforming the socket part, there are other methods
for creating a form fit between the ball and socket. For example, the
socket can be placed on the ball on one side and, in this position, can be
connected by another piece on the other side underneath the ball part by
bolting, for example.
According to a preferred application of the invention, the socket part is
further fitted with a threaded bore which when connected to a set screw
establishes a predefined angle to the ball part, which can be changed by
loosening the set screw. This solution has the advantage that the threaded
bore can be easily created and that the fastening of the set screw can
also serve to fasten the tooth replacement, so that a relatively simple,
short screw for fastening the ball joint is required. The fastening screw
can itself serve as the set screw, where applicable.
A particularly favorable application of an implant according to the
invention results when the implant post itself is an elastic deformable
piece (within certain limits) made from synthetic material, on which the
ball part is formed in one piece so that this part of the ball joint also
has a certain elastic deformability. This can be used to limit the
relative motion of the bill socket, before locking of the ball element
with a set screw for example, to the point that no undesired change in
position can occur after positioning of the socket in relation to the
ball. Additionally or instead of the above, it is also possible to so
construct the socket that it grasps the ball part with a certain preload,
where the inner or lower end of the socket is fitted similarly like a
clamping sleeve with pretensioned fingers with springs against the ball's
upper surface. With this configuration, it is also possible to lock the
elements of the ball joint detachably together, for example by means of a
spring clip, so that the fingers are prevented from an undesired
separation due to tensile forces, and are held in position on the
perimeter of the ball part.
These and other details and advantages of the invention are further
illuminated by the drawings that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an axial section of the preferred implementation of an implant
according to the invention;
FIGS. 2-4 are axial sections of modified applications of fastening devices
for the implant post for an implant according to the invention;
FIG. 5 is an axial section of an installed base body in the jaw bone by
means of an implant according to the invention with fastening devices
according to FIG. 4;
FIGS. 6-8 are axial sections of modified applications of the fastening
devices for the implant post for an implant according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In detail, FIG. 1 shows an implant according to the invention with a base
body 10. The implant is installed precisely in a prepared boring of the
patient's jaw bone and heals into the bone in a period of about three
months. The base body 10 consists preferably of titanium and is highly
polished on its upper end, while the lower part, as shown in FIG. 1,
preferably has a roughened surface which can be achieved by knurling or
sand blasting, or also by plasma coating with titanium or hydroxyapatite.
The base body 10 is open at the upper part and is fitted with a female
thread, in which in this example the implant post 20 is directly screwed
in, whose shaft in part exhibits a male thread which grasps the female
thread of the base body 10 and at its upper end exhibits a fastening head
22, which is fitted with a conical fitting surface 23 and female thread
24. A tooth 26 is fitted on the fastening head 22, which is secured by
means of a screw 28, whose shaft grasps the female thread 24. The implant
post 20 can also, for example, be fabricated from titanium, but is
preferably, for previously mentioned reasons, made from a viscous-elastic
synthetic with the appropriate elastic properties and dimensions. The
essential advantage of the implant according to FIG. 1 is that the conical
surface 23 with a corresponding fitting surface of the tooth replacement
or tooth 26 forms a strong frictional and form fitting connection, which
after tightening of the fastening screw 28 prevents loosening of the same.
In the embodiment according to FIG. 2 of the drawing, a ball part 22d is
fastened by means of screw 29 to the fastening head 22 of the implant post
20. The ball part 22d has a conical recess for acceptance of the socket
22. In this case, the fastening head 22 does not serve directly as the
fastener of the tooth replacement as in the embodiment in FIG. 1, but
indirectly by keeping the ball part 22d in place, which works together
with the socket 22a, which is part of the external fastening head 22',
which again has a conical fitting surface 23', ensuring secure retention
of the tooth replacement. It should be mentioned here that the
availability of a fitting surface 23/23' on the fastening head 22/22', and
particularly a conical fitting surface, also permits a favorable and
reliable fastening of the tooth replacement even when it is not screwed in
as previously described but glued or cemented. The ball part 20d forms an
element of the ball joint with which the socket 22a of the external
fastening head 22' works as the other element.
The fastening head 22 consists preferably of titanium and has a ball socket
22a which grasps the ball part 22d in such a way that equatorial plane A
of the ball part is grasped from behind by the inner or lower edge of the
external fastening head 22'. This is accomplished simply by rolling inward
the lower edge of the metal fastening head 22', as shown in FIG. 2. Above
the socket 22a, the fastening head has a conical head piece 22b with a
central threaded bore 22c, in which the set screw 35 is screwed, and can
tightened against the ball 22d in order to block the ball joint so that
the correct orientation of the elements 22d and 22a of the ball joint is
achieved. A tooth or crown 26 can then be placed on the fastening head 22'
and held in place by friction or by cement. If screw 35 is implemented as
a screw, the upper part of the thread can be used in the fastening head 22
for a retaining screw 28 for the crown 26. If the length of the fastening
screw 28 is carefully specified, this same screw can be used both to
fasten the crown 26 and also the ball joint. In any case, it is
advantageous, if care is taken, that the inner end of the screw 28 or 35
forms a concave calotte shell and that the head of screw 29 forms a convex
calotte shell. Blockage of the ball joint is made possible in this way
without incurring perpendicular forces which have the tendency to alter
the adjusted positions of the joint parts during ball joint blockage.
The example in FIG. 3 corresponds to the one in FIG. 2 to the extent that
also in this case a ball joint is used and constructed in the same manner
as described in the description for FIG. 2. Different from the example in
FIG. 2 is the fact that the conical recess is not located directly in the
ball part 20d, but rather in a pedestal part 36 connected to the ball part
20d. This pedestal part rests on the inner fastening head 22. In addition,
the ball part is fitted with a screw part 37, whose upper end is
preferably installed by press fit into the ball part 20d, and on whole
lower end or inner end an expansion bolt 38 is connected. The expansion
bolt's diameter is slightly larger than the diameter of the smooth walled
extension of the internal thread of the implant post 20. The expansion
bolt 38 presses the external thread of the implant post 20 into close
contact with the internal thread of the base body 10, so that also a
particularly secure connection is maintained between the base body and
implant post, whereby it is assumed that the implant post 20 consists of a
synthetic elastically deformable material.
A deviation from the application example shown in FIG. 2 is shown in the
example in FIG. 4, where the ball part 20d is formed as one piece with the
implant post 20. This way, the need for a fastening device to attach the
ball part 20d to the implant post is eliminated.
In addition, the implant post 20 according to FIG. 4 is designed for use
with a spacer bushing 16, which forms an extension of the upper end of the
base body 10. The spacer bushing 16 has a central band, which grasps the
base body 10 and ends in a shoulder 16a, which rests on the frontal
surface of the base body 10.
FIG. 5 shows an implanted implant according to the invention with an
implant post construction according to the previously described FIG. 4. In
regard to FIG. 5, the following describes how an implant according to the
invention should be handled. In detail, the treatment of the patient
begins by fitting the cylindrical base body 10 into a precisely prepared
fitting in the jaw-bone 12, which is allowed to heal for a period of three
months. During the healing process, the upper, open end of the base body
is sealed with a sealing screw (not shown), over which the opened gum
tissue 14 again grows. When the base body 10 has healed, the gum is opened
in the location of the sealing screw and the spacer bushing 16 is
installed in the open end of the base body, which grasps the base body
with a band and rests with its shoulder 16a on the upper edge of base body
10. Next, a impression post (not shown) is screwed into the female thread
of the base body. When this has occurred, an impression or mold of the
tooth/jaw formation of the patient is made and a model is created. On the
basis of the model, the appropriate tooth replacement is prepared; in the
simplest case, a crown, whereby the implant post used in the model has a
ball joint according to FIG. 5 on its upper end which aids in orienting
tee fastening head 22 correctly. In this case, locking of the ball joint
is done already on the model, after which the various parts of the tooth
replacement are brought into their proper position. As shown in FIG. 5,
axis C of the base body and axis B of the fastening head form an obtuse
angle.
According to FIG. 6, the base body 10 is again extended by means of a
spacer bushing 16, and the implant post 20 is again a one-piece synthetic
material with a built-in ball part 20d. The ball part includes in its
upper part a recess 39, which is connected to the threaded bore 22c of the
fastening head 22.
When the proper position of the ball joint is found, a hardening material,
for example in the form of balls 40, is introduced through the threaded
bore 22c into the recess 39 and neighboring part of the threaded bore 22c.
When the hardening material has hardened, the result is that the ball
joint is blocked into the desired position.
FIGS. 7 and 8 finally present further variations on the implant post
configuration, which correspond somewhat to FIGS. 1 and 4. In both cases,
however, a screw 42 is fitted, which similar to the screw part 37 in FIG.
3, has an expansion bolt 38, which grasps into a narrow pocket, or in some
cases, into a boring 42, which extends all the way to the inner end of the
implant post.
According to the examples of FIGS. 7 and 8, the screws 40 with their
expansion bolts 38 serve solely to press the synthetic material of the
implant post 20 outwards in the area of the expansion bolt 38 in such a
manner that a reliable resistance against turning between the base body
and the implant post is ensured.
In summary, an implant made according to the invention, among other
advantages, results in shortened labor time for preparation of firmly
seated tooth replacements in the laboratory, and increased accuracy and
quality, which is beneficial to the patient and represents a significant
step forward in dental treatment methods. While embodiments and
applications of this invention have been shown and described, it would be
apparent to those skilled in the art that many more modifications are
possible without departing from the inventive concepts herein. The
invention, therefore, is not to be restricted except in the spirit of the
appended claims.
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