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BACKGROUND OF THE INVENTION
The present invention relates in general to a hybrid dental implant system
and more particularly, to such a hybrid dental implant system constructed
and arranged to facilitate the recreation of a dentition in patients by
possessing the ability to freely interconvert from both a fixed and
retentive (nonstress bearing) implant modality.
During mastication, teeth are subjected to an infinite number for foce
vectors. Most of these forces are directed in an incisio-apical direction,
i.e., cusp tip to root tip, but some forces are directed the other way,
i.e., apico-incisal. These latter forces tend to dislodge full and
removable partial dentures, thereby presenting a continual problem to the
patient and dentist. In this regard, dental implants were created to help
the dentist most naturally recreate a dentition in patients who had lost
some or all of their teeth. These implants, in specific cases, have
superseded full and removable partial dentures. The dental implant
disclosed is an endosseous basket placed into a surgically prepared site
in the jawbone. A prosthesis is then attached to that portion of the
implant that extends through the soft gum tissue into the patient's mouth.
One such dental implant is illustrated in U.S. Pat. No. 4,359,318 in the
name of Neal Gittleman.
In general, these implants have been constructed in a variety of forms for
use by the dentist, either as a fixed implant or as a retentive implant.
The fixed implant, used for crown and bridge support, is generally
preferred by dentists as it aids in restoring a more natural dentition. In
the dentate patient chewing forces are absorbed in part by the resilient
action of the bone and periodontal ligament, while a fixed implant loads
the bone directly.
The retentive implant, on the other hand, is designed to retain a
prosthesis, not support it as in the case of the fixed implant. The
retentive design prevents dislodgement of the prosthesis when it is
subjected to apico-incisal forces, yet minimizes the occlusal forces
placed upon the implant by allowing the soft gum tissue to absorb most of
the inciso-apical forces. The retentive implant combines the desirable
aspects of full and removable partial dentures with those of an endosseous
fixed dental implant. For example, the retentive implant overcomes the
problem encountered with full and removable partial dentures by resisting
dislodging forces. The prosthesis, connected to the jawbone via the
implant, has a limited movement when subjected to apico-incisal forces. As
a result, forces which can cause movement of the implant within bone will
be maintained. This will manifest itself in a lower rate of peri-implant
epithelialization, peri-implant infection, and implant failure.
In the event of failure of a fixed implant and/or natural abutment, it is
often desirable that a retentive implant securing a denture be utilized.
Furthermore, fixed implant modalities often do not lend themselves to be
easily converted for use as a retentive implant. Therefore, it may be
required that the dentist remove the prosthesis and fixed implant, in
order that a retentive modality be substituted for retaining a full or
partial denture. This procedure may subject both the patient and dentist
to increased chair time, additional surgery, and further expenses.
SUMMARY OF THE INVENTION
It is broadly an object of the present invention to provide a hybrid dental
implant system which overcomes or avoids one or more of the foregoing
disadvantages resulting from the use of the above-mentioned prior art
dental implants, and which fulfills the specific requirement of such a
hybrid dental implant system possessing the ability to go from a fixed
implant modality to a retentive, nonstress bearing removable implant
modality. Specifically, it is within the contemplation of one aspect of
the present invention to provide a hybrid dental implant system which,
should an abutment tooth anterior or posterior to a fixed implant fail, a
fitting can be simply screwed out of an endosseous basket and a retentive
fitting screwed into the basket in its place.
Another object of the present invention is to provide a hybrid dental
implant system, which when employing a retentive implant, is virtually
stress-free by minimizing the occlusal forces that are placed on the
implant.
Another object of the present invention is to provide a hybrid dental
implant system, which when employing a retentive implant, provides
increased masticatory efficiency, and subjectively, the feeling of having
a more functional and asthetic dentition.
Another object of the present invention is to provide a hybrid dental
implant system, which when employing a retentive implant, combines the
best aspects of full and removable partial dentures with that of an
endosseous fixed dental implant.
Another object of the present invention is to provide a hybrid dental
implant system, which when employing a retentive dental implant, has its
fulcrum point beneath cortical bone.
Another object of the present invention is to provide a hybrid dental
implant system, which when employing a retentive dental implant, reduces
the lever arm of the implant upon loading by virtue of the implant being
constructed of resilient material and the location of its fulcrum point.
Another object of the present invention is to provide a hybrid dental
implant system, which when employing a fixed implant will predictably
support an occlusion.
Another object of the present invention is to provide a hybrid dental
implant system, which when employing a fixed implant, incorporates a
stress breaking device in the nature of an artificial periodontal
ligament.
Another object of the present invention is to provide a hybrid dental
implant system, which when employing a fixed implant, includes a stress
breaking device which is substantially isolated from the cortical bone and
soft gum tissue.
Another object of the present invention is to provide a hybrid dental
implant system which avoids inflammation, infection and hard tissue
resorption.
Another object of the present invention is to provide a hybrid dental
implant system which is permanently anchored in the jawbone through bone
growth.
In accordance with one embodiment of the present invention, there is
provided a dental implant system for attaching a dental prosthesis to a
jawbone underlying gum tissue. The dental implant system is constructed of
a sleeve member to be secured within an upper portion of the jawbone,
fixed implant means to be received by the sleeve for securing a dental
prosthesis thereto, and retentive implant means to be alternatively
received by the sleeve member for retaining the dental prosthesis while
the prosthesis is at least partially supported by gum tissue.
BRIEF DESCRIPTION OF THE DRAWINGS
The above description, as well as further objects, features and advantages
of the present invention will be more fully understood by reference to the
following detailed description of a presently preferred, but nonetheless
illustrative, hybrid dental implant system in accordance with the present
invention when taken in conjunction with the accompanying drawings,
wherein:
FIG. 1 is a cross-sectional view of the hybrid dental implant system
employing an endosseous basket and a fixed implant member, including a
stress breaking device;
FIG. 2 is a cross-sectional view of the hybrid dental implant system as
shown in FIG. 1 employing an endosseous basket and a retentive implant
member adapted to allow a dental prosthesis to be supported on gum tissue;
FIG. 3 is a top plan view of the fixed implant member as shown in FIG. 1;
FIG. 4 is a top plan view of the retentive implant member as shown in FIG.
2;
FIG. 5 is a perspective view of an inert biocompatible submergible dowel
adapted for use with the endosseous basket as shown in FIGS. 1 and 2;
FIG. 6 is a front elevational view, in partial cross-section, showing the
use of a fixed implant member for supporting a crown and bridge
prosthesis; and
FIG. 7 is a cross-sectional view of the dental hybrid implant system as
shown in FIG. 2, illustrating its retention of a denture by a retentive
implant member, and which denture is being partially supported by soft gum
tissue.
DETAILED DESCRIPTION
Referring now to the drawings, wherein like reference numerals represent
like elements, there is disclosed in FIGS. 1 and 2 a hybrid dental implant
system generally designated by reference numeral 100. The implant system
100 includes a sleeve member 102 which is preferably constructed from
surgical titanium or alternatively a ceramic or possibly one of the
hydroxylapatite materials. The sleeve member 102 includes a hollow
cylindrical lower portion 104 and a hollow cylindrical upper portion 106
separated from the lower portion by rib 108. A series of apertures 110 are
provided about the lower portion 104, while a plurality of grooves 112 are
provided circumscribing the sleeve member 102 as to be described
hereinafter. The upper portion 106 is provided with a central bore 114
extending to the rib 108 and provided with a plurality of internal threads
116. In accordance with one embodiment, the sleeve member 102 has an
overall length of about 12 millimeters and an outside diameter of about 4
millimeters.
The implant system 100 includes a fixed implant member 118, as shown in
cross-section in FIG. 1 and in plan view in FIG. 3; and a retentive
implant member 120, as shown in cross-section in FIG. 2 and in plan view
in FIG. 4. Referring now to FIGS. 1 and 3, the fixed implant member 118
includes a cylindrical hollow outer core 122 having a closed end and a
plurality of external threads 124, a concentrically arranged inner sleeve
126 having a closed end 127 and providing a surrounding annular opening
between the core and inner sleeve, and a spacer 128 of resilient material,
for example, silicon, provided within the annular opening. The hollow core
122 is provided at its upper edge with a pair of spaced-apart notches 130
as to be described hereinafter. The hollow core 122 and inner sleeve 126
are preferably constructed from surgical titanium. In accordance with one
embodiment, the fixed implant member 118 has an overall length of about 6
millimeters and an outside diameter of about 3 millimeters. The fixed
implant member 118 is adapted to be threadedly received within the
threaded core 114 in the upper portion 106 of the sleeve member 102. A
fixed implant insert 132 constructed of surgical titanium, includes an
elongated cylindrical stem 134 adapted to be slidingly received within the
inner sleeve 126 of the fixed implant member 118 and an enlarged head 136.
Although they fixed implant insert 132 has been described as a cylindrical
member, it is to be understood that the fixed implant insert may be
constructed in the form of a flat blade and the like.
Referring now to FIGS. 2 and 4, the retentive implant member 120 includes a
cylindrical hollow core 138 of surgical titanium and having a closed end
139 and a plurality of external threads 140. A retentive lip 142 formed
between a pair of cam surfaces 144, 146 is arranged extending inwardly
from the interior surface of the inner sleeve 126. The retentive lip 142
is constructed in the form of a circular ring arranged at a location
approximately 3 millimeters along the length of the inner sleeve 126 and
dividing the inner sleeve into an upper hollow region 148 and a lower
hollow region 150. The inner sleeve 126, in one embodiment, has an overall
length of about 6 millimeters and an outside diameter of about 3
millimeters. A pair of opposed spaced-apart notches 152 are provided
within the upper edge of the inner sleeve 126 in the manner of notches 130
provided within the upper edge of the hollow core 122 of the fixed implant
member 118. The retentive implant member 120 is adapted to be threadingly
received within the bore 114 of the upper portion 106 of the sleeve member
102, in a similar manner as the fixed implant member 118. That is, the
fixed implant member 118 and retentive implant member 120 can be
alternatively threadingly received within the bore 114 of the sleeve
member 102 as desired.
Accompanying the retentive implant member 120 is a retentive implant insert
154 constructed of an elongated cylindrical stem 156 having an enlarged
head 158. The stem 156 has a diameter slightly smaller than the inside
diameter of the core 138 to provide smooth sliding engagement
therebetween. As shown, the stem 156 includes a section 160 of reduced
diameter to provide a longitudinally extending circumscribing channel 162
adapted to receive the retentive lip 142. The channel 162 permits the
retentive implant insert 154 to slide longitudinally within the hollow
core 138 of the retentive implant member 120 in the order of 1 to 2
millimeters inciso-apically. The retentive implant insert 154 is retained
within the core 138 by the lower portion 164 of the stem 156 being
retained by its engagement at ridge 165 with the cam surface 146 of the
retentive lip 142 under normal occlusal and masticatory forces.
The jawbone 166, i.e., cortical bone, is prepared for receiving the implant
system 100 in the manner disclosed in U.S. Pat. No. 4,359,318. Briefly, a
drill (not shown) makes two different cuts in the jawbone 166.
Specifically, the drill forms an annular cut 168 which defines the
upwardly extending stump 170 and a central opening 172, the annular cut
and central opening having a plurality of circumscribing grooves 174. To
insert the sleeve member 102 into the jawbone 166 after it has been
prepared as shown and described, the sleeve member is lowered into the
jawbone so that the lower portion 104 enters the annular cut 168 and the
rib 108 is supported by the stump 170. After the sleeve member 102 has
been introduced into the surgical site, an inert biocompatible submergible
dowel, as shown in FIG. 5, is placed within the upper portion 106 of the
sleeve member. The dowel 176 includes a plurality of external threads 178
and a slot 180 extending within its upper surface 182. The dowel 176 is
threadingly received within the sleeve member 102 using a screwdriver
engaging the slot 180 or other such implement. However, the dowel 176 can
be constructed without threads 178 and secured within the sleeve member
102 using a temporary cementing agent. The dowel 176 prevents the
down-growth of soft gum tissue 184 within the upper portion 106 of the
sleeve member 102 while the jawbone 166 heals.
The sleeve member 102 is retained within the jawbone 166 and buried beneath
the gum tissue 184 for a period of three to six months, and left
undisturbed to allow for complete healing. In this regard, healing can be
promoted by application of an electric current in the manner disclosed in
the aforesaid patent. It will be appreciated that the sleeve member 102
will provide an unusually strong bond with the jawbone 166, once the bone
has knit through the apertures 110. In addition, the grooves 112, being
dimensioned approximately one-third of a millimeter in height and
one-quarter of a millimeter in depth, facilitates the securing of a sleeve
member 102 within the jawbone 166. The grooves 112 along with the
apertures 110, allow the jawbone 166 to mechanically interlock the sleeve
member 102 in a manner known as osseointergration. Once the jawbone 166
has healed, as determined radiologically, so as to secure the sleeve
member 102 therein, the gum tissue 184 is opened and the dowel 176
removed. In its place either the fixed implant member 118 or retentive
implant member 120 is threadingly received within the upper portion 106 of
the sleeve member 102 for the purpose as now to be described.
Referring to FIG. 6, there is shown a portion of a patient's mouth having
three anterior teeth 186, 188, 190 supported within the jawbone 166 by
periodontal ligaments 192. Tooth 190 is prepared at location 193 in a
conventional manner as an abutment tooth for receiving a crown and bridge
prosthesis 194. A sleeve member 102 of the hybrid dental implant system
100 of the present invention is inserted into the jawbone 166 in the
manner as thus far described. A fixed implant member 118 is threadingly
received within the upper portion 106 of the sleeve member 102 using a
screwdriver engaging the notches 130. A fixed implant insert 132 is
secured within the inner sleeve 126 of the fixed implant member 118, such
that head 136 extends above the gum tissue 184. The fixed implant insert
132 functions as an abutment for receiving the crown and bridge prosthesis
194. The crown and bridge prosthesis 194 is secured to the abutment tooth
190 and to the head 136 of the fixed implant insert 132 using any suitable
means, for example, a screw (not shown) provided within an opening
extending through each crown. However, other arrangements may be devised
for removably attaching the crown and bridge prosthesis 194 to the
abutment tooth 190 and fixed implant insert 132.
The hybrid dental implant system 100, as described with reference to FIG.
6, functions as a fixed implant system for supporting the crown and bridge
prosthesis 194 to help the dentist more naturally recreate a dentition in
patients who have lost some or all of their teeth. The occlusal and
masticatory forces exerted upon the fixed implant 118 are absorbed by the
resilient spacer 128, which functions as a stress breaking device, and
more specifically, as an artificial periodontal ligament. The resilient
spacer 128, unlike the periodontal ligament, is isolated from the jawbone
166 by being provided within the annular space provided between the inner
sleeve 126 and hollow core 122 of the fixed implant member 118. Thus, for
the first time, a fixed implant system, as sued for supporting a crown and
bridge prosthesis 194, is predictable by being able to support an
occlusion.
In the event of failure of the crown and bridge prosthesis 194, for
example, as a result of gum disease, occlusal trauma, jawbone breakdown,
or extraction of an abutment tooth, it is often required that the crown
and bridge prosthesis be replaced by a full or partial denture.
Previously, it would have been required that the sleeve member 102 be
surgically removed and replaced with a suitable implant adapted for
retaining a denture. However, the hybrid dental implant system 100 of the
present invention avoids the need of having to remove both the failed
crown and bridge prosthesis 194 and sleeve member 102 of the fixed implant
member 118.
As shown in FIG. 7, after the crown and bridge prosthesis 194 has been
removed, the fixed implant member 118 is removed from the upper portion
106 of the sleeve member 102 and replaced with a retentive implant member
120 using a suitable screwdriver engaging notches 152. A cylindrical
centering member 196 is positioned about the upper portion of stem 156 of
the retentive implant insert 154. The stem 156 is inserted as fully as
possible into the hollow core 138 by urging its lower portion 164 past the
retentive lip 142, which is accommodated as by the resilient construction
of the retentive implant insert 154. As more clearly shown in FIG. 2, the
lower portion 164 of the retentive implant insert 154 is retained within
the lower region 150 while the retentive lip 142 is captured within the
channel 162 provided along the stem 156. The centering member 196 prevents
the retentive implant insert 154 from bending when securing a denture to
its head 158 using a suitable adhesive, i.e., an acrylic. Specifically, a
"pick-up" technique, using a quick setting acrylic adhesive is employed to
capture the head 158 of the retentive implant insert 154 on the under
surface of a denture 198 which supports a plurality of teeth 200, as shown
in FIG. 7. After the acrylic adhesive has set up and hardened, and the
capturing process completed, the centering member 196 is discarded. In
order to support a full or partial denture 198, a plurality of retentive
implant members 120 are provided within sleeve members 102 secured within
the jawbone 166 of the patient.
Unlike the fixed implant member 118, the retentive implant member 120
permits the denture 198 to be, for the most part, supported by the
underlying gum tissue 184. Thus, occlusal and masticatory forces are
mostly distributed to the underlying gum tissue 184, as opposed to being
entirely supported by the denture 196 and retentive implant member 120, as
would be the case when employing the fixed implant member 118 as shown in
FIG. 6. That is, the occlusal and masticatory forces being supported
directly by the crown and bridge prosthesis 194, abutment tooth 190 and
fixed implant member 118. The retentive implant member 120 prevents
dislodgement of the denture 198 when it is subjected to apico-incisal
forces, yet minimizes the stresses placed upon the implant by allowing the
soft gum tissue 184 to absorb most of the incisal-apico forces. The
retentive lip 142 of the retentive implant member 120, being captured
within the channel 162 of the fixed implant insert 132, permits sliding
movement of up to 1 to 2 millimeters inciso-apically, thereby allowing the
underside of the denture 198 to exert force upon the underlying soft gum
tissue 184, thereby dissipating it before any such force is transmitted to
the implant itself. Should these forces be applied directly to the
retentive implant member 120, for example, due to the settling of the
denture 194, these forces are minimized due to the retentive implant
insert 154 being constructed of flexible resilient material such as nylon.
In addition, inciso-apical and apico-incisal forces are minimized by
placing the fulcrum point, i.e., the lower portion 164 of the retentive
implant insert 154, below the surface of the jawbone 106 within the lower
region 150 of the sleeve member 102. That is, by reducing the fulcrum arm,
as designated by letter F in FIG. 2, the transmission of these forces to
the jawbone 166 and sleeve member 102 is substantially reduced.
As will be readily apparent to those skilled in the art, the invention may
be used in other specific forms without departing from its spirit or
essential characteristics. The present embodiments are, therefore, to be
considered as illustrative and not restrictive, the scope of the invention
being indicated by the claims rather than the foregoing description, and
all changes which come within the meaning and range of equivalence of the
claims are therefore intended to be embraced therein.
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