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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to a novel osseointerfaced implanted
artificial tooth which provides a permanent replacement for a natural
tooth. In the past, many systems have been proposed for the implantation
of artificial teeth. For example, diverse designs with screws, nails,
blades, and the like which are loaded immediately upon insertion in the
jaw bone. These implants generally result in scar formation around the
implant with insufficient gingival seal, causing chronic infection, bone
loss, and the eventual removal of the implant itself. For example, U.S.
Pat. Nos. 2,857,670 and 3,579,831 describe these systems.
Later designs, such as that shown by U.S. Pat. No. 3,589,011, describe a
two stage implant where a shank, or hollow pin, is used as the root of the
artificial tooth. A superstructure is then attached to the shank by
utilizing the hollow herewithin to support the super structure, including
the crown of the artificial tooth thereabove. U.S. Pat. Nos. 3,797,113;
3,979,828; 4,178,686; 4,195,409; 4,259,072; 4,270,905; and 4,324,550
describe this type of system. The root portion in many cases becomes
resorbable which eventually weakens the implant necessitating removal.
Many materials such as polymethylmethacrylate eventually cause tissue
necrosis and scar formation.
U.S. Pat. Nos. 4,215,986 and 4,318,696 describe implants which address the
problem of protecting destruction of the artificial tooth by the
masticatory forces that overload. It has been found that adjacent natural
teeth have also been damaged by this type of implant, causing the
breakdown of tissue supporting the natural tooth. An artificial implant
system which overcomes the disadvantages of the prior art hereinabove
described would be an extremely useful advance in the dental field.
SUMMARY OF THE INVENTION
In accordance with the present invention, a novel and useful
osseointerfaced implant system is described which may be permanently
affixed to the jaw bone is provided.
An artificial tooth of the present invention is implantable in the jaw bone
(alveolar) and employs an implantable tooth root. The tooth root has a
distal end portion extending into the jaw bone and a proximal end portion
being accessible from the outer surface of the jaw bone. The root further
includes a hollow extending from the proximal end portion of the root
toward the distal end portion of the root. The root may include means for
tapping, or self tapping the same in relation to the jaw bone during
placement. Means is also provided for fixing the root to the jaw bone,
such as a threaded surface. The hollow of the tooth root provides a place
of fixation for the remainder of the artificial tooth. A post threads or
otherwise fixes to the hollow of the tooth root and extends upwardly away
from the jaw bone. The hollow may be sealed during a healing period to
further strengthen the tooth root, and to maintain an unobstructed place
of fixation for the post. The post may have a first portion fitting within
the hollow of the root and a second portion extending outwardly from the
hollow. The post second portion may also embrace an outer surface which
slopes downwardly toward the first portion of the post, and inwardly
toward the center of the post. This so called obtuse angle provides a
tight contact between the gingiva and the implant and protects this
contact as well.
A crown is then connected to the post, specifically the second portion of
the post extending outwardly from the hollow of the tooth root. The second
portion of the post may also be formed such that a base connects to the
first portion of the post and a stem extends from the base of the second
portion of the post. Means may also be provided for breakably connecting
the base to the stem of the second portion of the post. In this manner,
excessive lateral forces would shear the post rather than traumatizing the
implant or the jaw bone itself.
To limit the elasticity of the upper structure, the second portion of the
post may be coated with a polymer which would lie between the crown and
the post. The polymer acts as a shock absorber and protects the bone
against sudden high stress. Moreover, the polymer, or plastic coating,
must have an elasticity which would limit mobility of the implant system;
thus precluding damage to the bone around the natural teeth.
The base of the second portion of the post may include a dimension that
extends a greater distance transversely in relation to the root than a
transverse dimension of the stem of the second portion of the post. Thus a
platform is provided for the plastic or polymer coating against shear
stresses thereupon.
Another embodiment of the present invention utilizes a spacer and spline as
the post. Means for fixing the spacer adjacent to spline and between the
root and crown is also provided. The spacer may include the sloping outer
surface of the post. Such a spacer would provide the dental practitioner
with a method for adjusting the height of the same above the artificial
tooth root. The spacer would also have means of turning the same in
relation to the spline. Thus, the spacer and post fittingly engage one
another.
The implant of the present invention may also include means for permitting
the attachment of a denture to the post and the plastic, metal or like
coating there around.
It may be apparent that a novel and useful artificial tooth implantable in
the jaw bone has been described. It is therefore an object of the present
invention to provide an artificial tooth implantable in a jaw bone which
provides satisfactory service over a long term.
It is another object of the present invention to provide an artificial
tooth implantable in a jaw bone which closely resembles the mobility of
the natural tooth, thus permitting the patient to chew in a normal manner
and protect against parafunctional forces.
It is yet another object of the present invention to provide an artificial
tooth implantable in a jaw bone which may be used in substitution for a
single tooth or a group of teeth as well as being connectable to natural
teeth.
Still another object of the present invention is to provide an artificial
tooth implantable in a jaw bone which protects against food particles
being wedged between the gingiva and the implant during the chewing
process, and against traumatizing of the contact site between the gingiva
and implant.
Yet another object of the present invention is to provide an artificial
tooth implantable in a jaw bone which has a predetermined breakage point
of a portion thereof, upon the application of a predetermined shear force,
thus protecting the implant and/or the jaw bone itself.
Another object of the present invention is to provide an artificial tooth
implantable in the jaw bone which utilizes a post having a removable
section which permits the dental practitioner to adjust the height of the
post in relation to the tooth root.
Another object of the present invention is to provide an artificial tooth
implantable in the jaw which permits the dental practitioner to remove all
portions of the implant, and replace the same with new portions, except
the artificial root.
The invention possess other objects and advantages, especially as concerns
particular characteristics and features thereof which will become apparent
as the specification continues.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of an embodiment of the present invention
showing a portion of the jaw and gum in broken away configuration.
FIG. 1A is a view taken along line 1A--1A of FIG. 1.
FIG. 1B is a view taken along line 1B--1B of FIG. 1.
FIG. 1C is a view taken along line 1C--1C of FIG. 1.
FIG. 2 is a sectional view of another embodiment of the present invention.
FIG. 3 is a sectional view of another embodiment of the present invention.
For a better understanding of the invention, reference is made to the
following detailed description of the preferred embodiment which should be
taken in conjunction with the hereinabove described drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Various aspects of the present invention will evolve from the following
detailed description which should be taken in conjunction with the
hereinabove described drawing. The invention as a whole is shown in the
figures by reference character 10 and may include as one of its elements
an implantable tooth root 12.
Root 12 may be constructed of a relatively rigid biocompatable material.
For example, titanium would be a satisfactory material under this
criteria. Root 12 is roughly cylindrical in shape and possesses a threaded
surface 14. Root 12 may also include a self tapping construction, FIG. 1
broken away portion, of known construction. Root 12 includes a hollow
portion 18 which extends from the upper surface 20 of root 12 toward the
lower surface 22 thereof. Thus, proximal end portion 24 of root 12 extends
to the outer surface of jaw bone 26. Distal end portion 28 of root 12
extends into the jaw bone 26 as far as is necessary for a satisfactory
implantation. Threaded surface 14 of root 12 threadingly engages the
threaded surface of jaw bone, FIG. 1C, 26 created by self tapping means
16. Thus, this threading engagement may be considered means 30 for fixing
root 12 to jaw bone 26. Slot 32 permits the user to use a driving means to
turn root 12 during the tapping of jaw bone 26. It should be noted that a
screw 34 is temporarily placed in hollow proportion 18 and is held in
place by the threaded surface 36 of screw 34 engaging threaded surface 38
of root 12 within hollow portion 18. Turning to FIG. 1A, it may be seen
that screw 34 is temporarily inserted into hollow 18 during first stage of
the implant which will be further described hereinafter.
Post 44 includes a first portion 46 which fits within hollow 18 of root 12.
A second portion 48 extends outwardly from hollow 18 and upwardly from the
surface of jaw bone 26. Second portion 48 includes an outer surface 50
which slopes downwardly toward first portion 46 of post 44 and inwardly
toward the center of post 44. This permits the tight fitting of gingiva 52
to the outer surface 50. The sloping surface 50 also acts as a shelter
against food particles wedging between surface 50 and gingiva 52. It
should be added that the prevention of food particles from entering the
space between the gingiva and the outer surface 50 of the post prevents
damage to the implant and the living tissue thereat. Means 54 fixes first
portion 46 of post 44 within hollow 18 of root 12. Such means may take the
form of providing first portion 46 of post 44 with a threaded surface 56
which engages threaded surface 38 of hollow 18. It may be apparent that
threaded surface 36 of screw 34 previously engaged the same threaded
surface 38 of hollow 18, FIG. 1B. Post 44 may again be constructed of a
fairly rigid material such as titanium. Second portion 48 of post 44 may
include a base 58 connected to first portion 46 of post 44. Stem 60
extends from base 58 upwardly from jaw bone 26. As shown in the embodiment
in FIG. 1, stem 60 is narrower transversely than base 58. Means 62
breakably connects base 58 to stem 60. In other words, second portion 48
of post 44 includes a weakened undercut portion 64 which surrounds the
connection area between base 58 and stem 60. Thus, any excess lateral or
shear forces will cause the breakage of stem 60 in relation to base 58 and
thereby protect root 12 in bone 26. Undercut portion 64 is filled with a
glue 66 which also surrounds stem 60. Glue 66 is used to attach a layer of
resilient material 68 such as silicone, polysulphone, and the like. The
thickness in quality of resilient layer 68 may be predetermined to
restrict the range of movement of the upper structure to about 200
microns. Resilient layer 68 also acts as a shock absorber to protect the
bone 26 against sudden high stress. Finally, a crown 70 may be formed as
shown in FIG. 1.
Turning to FIG. 2, it may be seen that another embodiment of the present
invention is provided. Post 44 includes a first portion 46 which fixes to
root 12 in the same manner as the post shown in FIG. 1. However, the upper
portion 48 has been split into a spline 72 and a washer, or spacer 74.
Means 76 fixes spacer 74 to spline 72. As shown in FIG. 2, means 76 takes
the form of a threaded outer surface 78 of spline 72 engaging a threaded
surface 80 of spacer 74. Means 82 is provided for turning spacer 74 in
relation to spline 72. Upper portion 84 of spline 72 may again break in
relation to lower portion 86 thereof via means 62. In certain cases,
spacer 74 may be replaced with one having a different height to compensate
for dimensional adjustments to root 12. Means 82 in the form of openings
88 and 90 permit the use of tool to perform this turning or rotational
action.
Turning to FIG. 3, it may be seen that upper portion 84 of spline 72 may be
reduced in size and a new resilient layer having a groove 92 is placed
over upper portion 84. A denture 94 may be snapped into place by the use
of "O" ring 96. It should be noted that if any portion of spline 72 or
post 44 break by the use of means 62, remainder of post 44 or spline 72
within root 12 may be removed and replaced.
In operation the jaw bone 26 is made visible to the dental practitioner by
the use of a surgical device. Root 12 is tapped into place using tapping
means 16 such that upper surface 20 of root 12 is accessible at the outer
surface of bone 26. The drills used to locate the root opening are cooled
to protect the bone against burning during this process. Screw 34 is
inserted into hollow 18 of root 12 and covered by gingiva 52 for
approximately four months. After this time period pilot hole 42 permits
the dental practitioner to locate screw 34 through the gingiva 52 covering
screw 34. A special cutting instrument removes the overlying tissue to
reveal screw 34. Screw 34 is then removed and post 44 or spline 72 and
spacer 74 are inserted within hollow 18 of root 12. It should be apparent
that the superstructure consisting of the crown and resilient layer 68
could be attached to post 44 or spline 72 and spacer 74 after fixation of
the post 44 or spline and spacer 72 and 74 to root 12. Resilient layer 68
will separate under pressure, such as the pressure applied by a plier-like
device. Separation of resilient layer 68 from post 44 permits the dental
practitioner to inspect, and/or alter the superstructure of the implant
system. Post 44 would also be removable from root 12. As heretofore
described, spacer 74 may be replaced with a spacer of a different height.
Upper portion 84 of spline 72 may be cut down to provide for the insertion
of a denture. Thus, all portions of the artificial tooth are replaceable,
except the root 12.
While on the foregoing embodiments of the present invention have been set
forth in considerable detail for the purposes of making a complete
disclosure of the invention, it may be apparent to those of skill in the
art that numerous changes may be made in such detail without departing
from the spirit and principles of the invention.
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