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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an endosteal root-form dental implant
system. More specifically, this invention relates to a self-drilling
endosteal hollow-basket implant system with a tissue extension (sometimes
referred to as a transmucosal abutment member) that supports and holds a
keeper with shock-absorbing resilient means. Inserted onto the keeper may
be various dental prosthesis designs.
2. Brief Description of the Prior
It is beyond the scope of this brief description to review the early
attempts of men to replace missing teeth. Studies of Egyptian mummies from
the middle kingdom up to Ptolomy's time revealed different processes of
implantation.
A scientific breakthrough in the area of dental implants was achieved by
Swedish Professor Per-Ingvar Branemark and co-workers. Combining a
two-stage surgical technique with the use of titanium fixtures, these
scientists achieved predictable results in surgical placement of permanent
dental implants. Their continued studies in the early 1960's provided the
basis of modern implantology.
However, because of the lack of periodontal ligaments between the bone and
the titanium fixture, the implant lacked the natural motion and
shock-absorbing capability of natural teeth.
Screw attachments have been employed between bone and fixture but under
great stress they tend to fracture. In a publication titled "Dental
Implant Prosthodontics" (J. B. Lippincott Company 1991 ISBN
0-397-51045-4), Ronald P. Desjardeins observed "The most common prosthesis
problem that the author has thus far noted is the loosening or breakage of
the gold locking screw with the resultant loosening of the prosthesis."
In the early 1970's, Dr. Kirsch from Germany designed an implant system
called IMZ with a plastic shock-absorber called the IME. This device
provides similar elastic properties as a periodontal ligament. The IME,
which is a threaded intermediary sleeve, is installed inside of the
implant by screwing it into the threaded bore of the implant. The sleeve
has a threaded bore, into which a prosthesis is screwed.
However, in the same publication mentioned above, Robert J. Chapman
observed that "the IME must be replaced every year or two, because it is
plastic and will deteriorate somewhat with function."
That deterioration of the plastic sleeve opens a way for bacteria and
changes the mechanical characteristics of this device. U.S. Pat. No.
4,622,010 describes a similar device that avoids the threads on the
plastic sleeve.
U.S. Pat. No. 4,993,950 describes a keeper system which uses an O-ring "to
permit universal `rocking` motion of the keeper member relative to the
true transmucosal cuff."
U.S. Pat. No. 5,006,068 describes a dental implant system with resilient
force dampening means on the prothesis itself.
These designs provide a single means of shock-absorbing capacity and do not
imitate the longitudinal movement of natural teeth. Other implant systems
fail to mirror the movement of natural teeth. Such systems may feel
unnatural to the person using such prior art dental implant systems.
Furthermore, when a prosthesis is cemented to a natural tooth abutment and
an implant abutment, the cement will be placed under great torquing stress
to both ends of the prosthesis. This torquing stress may break the cement
and cause the failure of the prosthesis.
Hollow-basket implants have advantages over the cylinder type. First, they
require a minimum of bone removal that results in a less traumatic
osteotomy. Second, they provide maximum anchoring surface and adequate
mechanical strength. Because of its tubular shape with various
perforations, it is able to withstand tension, compression or shearing
stress and torque. The hollow-basket design also allows a two-sided
growing of the bone tissue through the vents of the implant. Examples of
prior art efforts are shown in one or more of the following U.S. Patents:
U.S. Pat. No. 4,431,416; U.S. Pat. No. 4,951,819; U.S. Pat. No. 4,960,381;
U.S. Pat. No. 4,842,517; U.S. Pat. No. 4,379,694; U.S. Pat. No. 4,657,510.
However, these prior art hollow-basket implants are not self-drilling. The
insertion of prior art dental implant system involves a two-step surgical
procedure. This is typical of endosteal root-form implant and is well
known in the previous art. For the purpose of illustration, however, we
are going to summarize the events of the two steps. First, the surgeon
cuts a flap on the mucosa and drills a socket on the bone where the
implant is then placed with a cover screw. The soft tissue is repositioned
and the implant site is closed to avoid any movement of the implant and to
prevent infection. Later in the second step, after osseointegration is
complete, the surgeon uncovers and removes the cover screw. The surgeon
then installs a healing cap which is later replaced by a tissue extension.
It is into the tissue extension that the restoration is installed. On
occasion the restoration is attached to an intermediate device, located
between the tissue extension and the restoration, which we have referred
to as a keeper.
SUMMARY OF THE INVENTION
This invention relates to a dental implant system comprising an implant
with self-drilling capabilities. The self-drilling implant of the present
invention is tubular in shape and contains a basket socket and an internal
threaded socket. The basket socket is defined by cutting tooth edges
designed to finish the osteotomy sinking the implant into its definitive
place. Circular openings between the cutting tooth edges of the basket
socket are equally spaced around the circumference of one end of the
implant and they define the spaces between the cutting teeth. Their
function is to collect some of the bone chips from the osteotomy and to
provide space for the bone to grow out of this external socket in order to
provide additional support for the implant.
The capability of saving bone chips from the osteotomy is a very important
one since these bone chips will encourage the formation of a blood clot,
help to immobilize the implant, and provide an absorbable, autogenous
substance to precipitate recalcification. A restriction between the basket
and internal sockets has a circular opening which allows the circulation
of a cooling fluid during the drilling operation and serves as an opening
to provide medication.
The internal socket of the implant is located opposite of the basket socket
and has internal threads and serves four purposes. First, it receives an
auxiliary hollow threaded adapter or driver which makes it possible to
drive the implant into the jawbone using a standard, low-speed,
internally-irrigated handpiece. Second, it receives a cover screw which is
used to seal the threaded socket of the implant and the central
restriction, during the initial integration period, to prevent bone
ingrowth. Third, it receives a healing cap, which is a temporary extension
used to maintain the opening through the gum tissue following second stage
surgery. Finally, it receive the tissue extension.
The tissue extension serves two purposes. First, it extends the length of
the implant from bone level to the gum level. This length is different for
different patients, and for that reason, the tissue extension is
manufactured in different lengths. Second, it holds and supports the
keeper.
The tissue extension has four outside sections. First, a frustum section
which fills and seals the internal restriction which defines the two
implant sockets. The second section is a threaded area which allows the
tissue extension to be securely threaded to the threaded socket of the
implant. The third section has a conical shape which extends out of the
implant's socket, sealing the opening and relieving stress from the
threaded area. The last area has a cylindrical shape with a diameter
slightly larger than the diameter of the implant. On top of the
cylindrical section, the tissue extension has a deep socket, and an
internal shoulder at the opening of the socket in order to hold the
root-part of the keeper which is encapsulated in a resilient member.
Beyond the shoulder, the socket has a void that is conical in shape with
longitudinal grooves to avoid the rotation of the resilient member. The
socket ends with a cylindrical hollow core that finishes close to the
bottom of the tissue extension.
The keeper has a bi-frustum shape with a central hollow core and a tubular
extension on one end. The tubular extension and the first frustum section
next to it are the root-area of the keeper. The tubular extension provides
additional leverage to avoid a "rocking" motion of some prior art designs
and encourages the longitudinal motion of natural teeth. The frustum
section of the root-area has longitudinal grooves to avoid the rotation of
the keeper in the shock-absorbing member. The outside dimensions of the
root-area of the keeper are smaller than the inside dimensions of the
tissue extension's socket, leaving an empty space between both parts which
is going to be filled by the resilient member. The last section of the
keeper is the tooth stump which exits the tissue extension into the oral
cavity in order to support, by different means, a variety of prostheses.
This might include crowns, bridges, overdentures, et cetera. The tooth
stump has a frustum shape with a hexagonal section in the central area.
This hexagonal section serves two purposes: first, it receives an
instrument to securely thread the tissue extension into the implant; and
second, it avoids the rotation of the restoration on the keeper. The
hollow core of the keeper has internal threads in the stump area to
receive a screw. The restoration is attached to the stump by that screw,
it can be cemented, or a combination of both.
With the root-area of the keeper in a concentric position, inside of the
tissue extension's socket, a high quality silicone rubber-like compound is
injected, as a fluid, to fill the space between both parts After "curing"
this elastic resilient member, which completely encapsulates the root-area
of the keeper, has a large surface area in intimate contact with the
tissue extension's socket and the root-area of the keeper itself. This
provides a shock-absorbing means for compression, shearing, torque, and
tension stress; allowing for a limited movement of the keeper similar to
the movement of natural teeth. Using different silicone rubber compounds
and different pressures of injection, the resilience of the resilient
member can be "tuned" to obtain differential elasticity. This is an
important feature of the present invention, since dependent upon the
location of a tooth in the oral cavity, the teeth function under varying
occlusal pressures.
For practical purposes, the tissue extension, the resilient member, and the
keeper can be considered a single unit, since the internal shoulder at the
opening of the tissue extension holds the elastic resilient member in its
place which in turn holds the keeper. However, if an extreme frontal
force, as in an accident, hits the restoration thereby endangering the
integrity of the jawbone, the keeper will exit the tissue extension as
natural teeth do to avoid further damage to the Jawbone.
Presently, there is also a second preferred embodiment of the tissue
extension-resilient member-keeper assembly, and it is going to be
described thusly:
The outside shape of the tissue extension of the second preferred
embodiment has the same characteristics of the outside shape of the tissue
extension of the first preferred embodiment; however, the socket has three
differences. First, the internal shoulder becomes a groove which is going
to hold an elastomeric seal. Second, the grooves of the void conical area
are eliminated. Third, the cylindrical hollow core at the end of the
socket is changed into a hexagonal socket which will serve two purposes.
First, it is going to receive an Allen wrench to securely thread the
tissue extension to the implant; secondly, it is going to receive the
tubular extension of the keeper.
The overall shape of the keeper of the second preferred embodiment is
similar to the shape of the keeper of the first preferred embodiment
except in two details. First, the frustum section of the root-area does
not have grooves but has many holes at different levels all around its
circumference, which are connected to the central core. Second, it has a
transverse groove all around its circumference to hold the seal where the
keeper exits the tissue extension. The groove also is connected to the
central core of the keeper. The tooth stump of the second preferred
embodiment has the same shape as the tooth stump of the first preferred
embodiment, except that the hexagonal section is not necessary since the
tissue extension itself has a hexagonal socket as mentioned above.
The shock-absorbing resilient member of the second preferred embodiment
differs substantially from the shock-absorbing resilient member of the
first preferred embodiment. The shock-absorbing member of the second
embodiment has three well-defined features. The first element is a boot
that covers the extension on the root-area of the keeper. This boot
isolates and holds in a concentric position the extension, respective to
the socket, of the tissue extension. The second element consists
essentially of many suction cups all around and at different levels of the
frustum on the root-area of the keeper. These suction cups are tension and
compression shock-absorbers, working as the periodontal ligament does. The
last element is a seal positioned on the transverse groove of the keeper
where the keeper exits the tissue extension. This seal closes the opening
of the tissue extension's socket, thus preventing any foreign substance
entrance. The seal is going to have a hexagonal section, and the groove of
the tissue extension will have an internal hexagonal section to prevent
the rotation of the keeper in those particular cases that rotation should
be avoided, as in a single tooth restoration. However, when more than one
implant are going to hold a restoration, the seal and the groove in the
tissue extension will have a circular section, which is easy to
manufacture, since rotation of the keeper is not a problem in these cases.
All these elements of the shock-absorbing member are formed in a single
operation by injecting the silicone rubber-like compound, as a fluid under
pressure, through the central core of the keeper, which is in a multi-part
mold.
The keeper of the second preferred embodiment can be removed by the patient
for purposes of personal hygiene, allowing the use of a Water Pik (or
similar deep cleaning device) to clean the socket of the tissue extension.
The keeper of the second preferred embodiment has the same safety feature
as the keeper of the first preferred embodiment. Both are designed to exit
the tissue extension in the event of an extreme frontal impact that may
put in jeopardy the integrity of the jaw bone.
An object of the present invention is to provide a dental implant system
which is able to relieve the prosthesis if stricken by excessive frontal
force, avoiding damage to the jawbone.
A principle object of the present invention is to provide a self-drilling
implant that saves the bone granulate from the final stages of the
drilling step. This provides several advantages. First, a scaffold to
facilitate blood clotting is formed. Second, the bone granulates provide a
physical means to immobilize the implant in its socket. Finally, the bone
granulates provide an absorbable matter not foreign to the patient.
An additional object of the present invention is to provide an implant
system which mimics the shock-absorbing capabilities of natural teeth.
Another object of the present invention is to provide an implant system
which mimics the longitudinal movement of natural teeth.
A further object of the present invention is to provide an implant system
that is easy to clean by the patient without the necessity of a dental
visit.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully comprehended when considered with
reference to the accompanying drawings and the explanations thereof.
FIG. 1 is a perspective view of the first preferred embodiment of the
dental implant system of the present invention.
FIG. 1A is a bottom perspective view of the first preferred embodiment of
the dental implant system of the present invention.
FIG. 2 is a section view of the first preferred embodiment taken along line
2--2 of FIG. 1.
FIG. 3 is a perspective view of the first preferred embodiment keeper
affixed inside the tissue extension.
FIG. 4 is a sectional view of the first preferred embodiment taken along
line 4--4 of FIG. 3.
FIG. 5 is a perspective view of the tissue extension with the second
preferred embodiment of the keeper affixed inside.
FIG. 6 is a sectional view of the second preferred embodiment keeper and
tissue extension taken along line 6--6 of FIG. 5.
FIG. 7 is a sectional view of the second preferred embodiment keeper and
tissue extension taken along line 7--7 of FIG. 5.
FIG. 8 is a sectional view of the second preferred embodiment keeper and
tissue extension taken along line 8--8 of FIG. 5.
FIG. 9 is a perspective view of the second preferred embodiment of the
keeper and the tissue extension disassembled.
FIG. 10 is a perspective cut-away view of the mold that is used to form the
second preferred embodiment of the keeper.
FIG. 11 is a perspective view of the driver and implant before the adaptor
is inserted into the implant.
FIG. 12 is a perspective view of the cover screw.
FIG. 13 is a perspective view of the healing cap.
FIG. 14 shows four different sectional views of the drilling procedure
accomplished during the first surgical stage. "A" is a view of the pilot
osteotomy made with a pilot drill (drill not shown). "B" is a view of the
second stage osteotomy made with a blade drill (drill not shown). "C" is a
view of the implant fixture driven to its final placement showing a
section of the driver shaft in place. "D" is a view of the implants'
fixture after replacing the driver shaft with the cover screw.
DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS
FIG. 1 and FIG. 1A illustrate a fully assembled dental implant system of
the present invention which can be implanted in the upper or lower jaw.
The fully implanted system consists of three main elements and a
shock-absorbing member. The three main parts are: the implant 40, the
tissue extension 20 and the keeper 10. These parts are made of material
with chemical, physical and biological characteristics adapted for
implantation in the oral cavity. Commercially pure titanium and certain
medical grade titanium alloys are preferred for the implant 40, the tissue
extension 20 and the keeper 10. The shock-absorbing member 30 is made of a
high quality silicone rubber-like compound.
Three auxiliary parts help the implantation process during the two-stage
surgical procedure. The three auxiliary parts are the adapter driver 50,
the cover screw 90 and the healing cap 130. These three auxiliary parts
are made of the same material as the three main elements to avoid
galvanism, and will be explained later in this description.
The self-drilling implant 40, shown in FIGS. 1, 1A, 2, 11, 14C and 14D has
a tubular shape with internal surfaces 44 and 49 which define two sockets
meeting at an orifice 45. This orifice 45 provides a passage for the
cooling fluid during the drilling operation and serves as an opening for
medication to fight local infection or pain. The first socket extends from
wall 49 vertically to adjacent cutting tooth edges 47 which is almost
horizontal and 48 which is approximately perpendicular thereto. They are
adapted to finish the osteotomy by sinking the implant to its definitive
place. The cutting teeth are defined by this inclined lip surface 47, the
nearly vertical surface 48, and the openings 46 between the teeth. While
this is similar to a surgical trephine bur, the preferred embodiment of
the implant of the present invention has several new features. First, it
has fewer teeth since it only works in the spongiosa 89, which is a less
dense section of bone. Also, the lip surface 47 has a minor inclination
angle to provide better support after osseointegration. Each tooth or
cutting edge 48, of the implant 40, is spaced apart by a definitive
collecting hole 46 where most of the bone granulate produced during the
drilling are collected.
To avoid overheating and provide space between the implant and the bone
socket, a clearance 86 is provided by the alternate bending of the implant
teeth or by increasing the width at the edge 47 of the teeth 48. Circular
openings 46 between the teeth of the first socket have their outside
periphery defined by the cylindrical surface 42 which as seen in FIG. 1
defines the lower portion of the implant. The function of these openings
46 and the first socket is to save some of the bone chips 87 (at FIGS. 14C
and D) from the osteotomy and to provide a space within which the bone
from both sides 88 and 89 (FIGS. 14C and D) of the bone socket can grow to
support and anchor the implant.
The surface 49 of the first socket is convex in order to seat the concave
surface 85 of the bone socket, shown in FIG. 14B, of the osteotomy.
The second socket of the implant as shown in FIG. 2 is angled and sloped at
surface 41 extending above the internal threads 43 to provide a sealing
surface and relieve compression and shearing stress from the threaded area
43.
The internal threads 43 serve four purposes: first, to secure the driver 50
during the self-drilling operation; second, to secure the cover screw 90
on the first surgical stage; third, to secure the healing cap 130 in the
second surgical stage; and, finally, to secure either tissue extension 20
or 70 after healing of the soft tissue is completed.
The outside surface 42 of the implant 40 may be textured or a coating of a
bio-compatible compound such as hydroxyapatite or titanium plasma may be
sprayed on it to increase the surface area and allow bone ingrowth.
This orifice 45 will be closed by the cover screw 90 in the first stage of
surgery and later by the lower portion 136 of the healing cap 130 and
finally by the lower portion 29 of the tissue extension 20 or 79 for
extension 70 to isolate the bone. This prevents ingrowth of the bone
tissue from the first socket to the interior of the implant.
The present invention improves the multiple step drilling operation for
endosteal root-form implants that use continuous irrigation by a cooling
fluid. The process of this invention begins by drilling a pilot hole
defined by 82 and 83 in the jawbone 80 for the osteotomy as shown in FIG.
14A. It is possible to insert a parallel pin (not shown) to check proper
angularity. In step two, as shown in FIG. 14B, a bigger drill is driven to
line 81 correcting any minor error of parallelism. The diameter of this
drill is similar to the implant's diameter. In step three, FIG. 14C, the
procedure differs substantially from the prior art, in that the implant
itself, rather than an extraneous drill bit, is driven by the driver 50
shown in FIG. 11 and FIG. 14C finishing the osteotomy.
Referring to FIG. 11, this driver 50 has a hollow core 51 to deliver the
cooling fluid irrigation during the drilling procedure. A groove 52 and a
cutout section 53 in the shaft allow the use of a standard handpiece (not
shown). The outside diameter of the shaft 54 can be increased
substantially to reduce vibration. The threads 55 at the end of the driver
50 are manufactured with enough clearance to facilitate the unscrewing of
the driver 50 from the implant 40 without removing the fixture from the
bone socket defined by 84 and 85 in FIG. 14B. The driver 50 is intended to
be pre-installed in the implant 40 to facilitate handling. This reduces
surgical time and avoids contamination.
A portion of the bone granulate is moved, by the cooling fluid, to
positions (FIGS. 14C and 14D) within the clearance 86 between the implant
outer surface 42 and bone socket 84.
The bone granulate in the clearance 86 between the implant fixture 40 and
the bone socket 84 and the bone granulate 87 in the collecting holes 46
encourage the formation of capillary blood vessels and new bone tissue
with a laminar structure.
The technique for driving the implant differs from prior art techniques
which recommend that "Profuse internal irrigation is required to keep the
drill from clogging" and which recommend to ". . . clean drill head often
to remove debris and ensure a sharp cutting surface." That is, the
self-drilling implant of the present invention does not require a profuse
internal irrigation to keep the drill from clogging since the implant is
itself the drill. The debris need not be removed to ensure sharp cutting
because collecting holes 46 serve to receive and disperse the bone
granulate into clearance 86. The irrigation needed for the implant of the
present invention is merely that required for cooling purposes only and
may be kept at a minimum volume using a previously refrigerated cooling
fluid. This characteristic saves in evacuation and helps reduce the amount
of cooling fluid used.
The preferred embodiment of the implant fixture 40 does not have to be
cleaned of debris to ensure a sharp cutting surface. One reason is that
the self-drilling implant 40 is going to finish the osteotomy of only one
socket. Regular drills usually make twenty-five sockets. Thus, the process
of the present invention assures a perfectly sharp cutting edge every time
and saves the time of having to "clean the head often".
Those skilled in the art can appreciate that one of the most important
features of the present invention is that it saves bone granulate from the
final drilling stage. As previously stated, this has three advantages.
First, it provides a scaffold for formation of a blood clot. Secondly, it
provides a physical means to help immobilize the fixture in the socket.
Finally, it provides an absorbable substance not foreign to the patient.
For purpose of illustration, FIGS. 14C and 14D show the bone granulate 87
in the collecting holes 46 and throughout the clearance 86. They also show
the bone core 88 that remains inside the drilling cavity defined by the
inner surface of teeth 48. This core 88 remains attached to the bone and
provides support and blood irrigation. During osseointegration, the bone
core 88 is going to grow through the collecting holes 46 providing
additional support and anchorage to hold the fixture in place.
If desired, additional rows of collecting holes 46 can be added. To finish
the osteotomy the surgeon reverses the handpiece rotation to remove the
adaptor 50 without disturbing the self-drilling implant 40, and install
the cover screw 90.
The cover screw 40 of the present invention FIG. 12 and FIG. 14d has a slot
92 in its conical head 93 to allow the use of a screwdriver. External
threads 91 engage the internal threads 43 of the implant 40. The lower end
has a conical shape 92 and a circular tip 95 which closes the opening 45
between the two sockets. The function of the screw 90 is to seal the
coronal opening 41 of the implant 40 and seal the opening 45 between the
two sockets to avoid the growth of bone over the implant.
In the second surgical stage, after osseointegration has been achieved, the
cover screw 90 is uncovered and replaced with the healing cap as shown in
FIG. 13 to maintain the opening through the tissue and cover the orifice
45 in the implant 40 socket defined by 41, 43 and 44.
The lower end of the healing cap 133-136 is similar in shape and dimensions
to the cover screw 90 since both are designed to screw into the implant
internal socket 41; however, the healing cap 130 has a cylindrical
extension 132 which maintains the opening through the tissue following
second stage surgery. The hexagonal head 131 of the healing cap 130
allowed the use of a hexagonal instrument (not shown) for its installation
and removal after the healing of the tissue when it is replaced with the
tissue extension 20 or 70. The tissue extension 20 or 70 is inserted into
the implant fixture 40. The tissue extension 20 or 70 holds the keeper 10
or 110, respectively.
The first preferred embodiment of the tissue extension 20 (FIGS. 2 and 3)
of the present invention has a highly polished intramucosal surface 24 and
a highly polished surface 21 to the oral cavity which better control
plaque. External threads 26 securely hold the tissue extension 20 to the
internal threads 43 of the implant fixture 40. A conical section 25
extending above the threads 26 provides an airtight stop, which seals or
locks the extension 20 and protects the threaded area 26 from compression
and shearing stress. A second conical section 28 extending below the
threads 26 performs the same function but also serves as a closure for
fixture orifice opening 45. The inside section 23 of the extension 20
defines the hollow interior of 20. Section 23 can be polygonal shaped at
its lower end 69 seen in FIG. 9, when the implant is designed for single
tooth prosthesis. This shape avoids rotation of the keeper end 66 which
would also be polygonal. However, when the tissue extension 20 is intended
for a bridge or overdenture, this lower end section 69 can be cylindrical
with a cylindrical end 66 for the keeper, since torsion is not a problem
in bridge or overdenture prothesis.
FIGS. 2 and 3 show the first preferred embodiment of the keeper 10
assembled within the tissue extension 20. The keeper 10 and tissue
extension 20 function as a single unit in this embodiment. A resilient
compound such as silicone rubber is injected in a fluid state through the
main shaft 13 of the keeper 10 to form a coating 30, 31 which is in the
form of a cocoon in intimate contact with the keeper 10 and tissue
extension 20.
The FIGS. 2 and 3 show the keeper 10, at its proximal end 11 through 14, is
designed to support a variety of dental prostheses. Its main shaft 13
opens at its distal end 19, through which the injected silicone rubber
compound 32 exits and coats the keeper exterior surfaces 30 and 31.
A shoulder 22 underneath the surface 21 on the tissue extension 20 holds
and conforms the resilient silicone compound 30 to surround the body
portion 16 of the keeper 10.
This configuration of the resilient compound acts as a shock-absorber able
to control compression, shearing and tensile stresses applied over the
keeper 10 imitating the shock-absorbing characteristics and movement of
natural teeth. For instance, depending on the location in the oral cavity,
the textural composition of the silicone compound will vary from soft for
frontal teeth prosthesis and progress to medium and hard for molar
prosthesis. This characteristic is very desirable and has been attempted
many times in the prior art with varying degrees of success.
The first preferred embodiment keeper 10 design of the present invention
facilitates ease of manufacture. That is, since the encapsulated keeper
16, 17 is not in direct contact with the tissue extension 20, broader
tolerances during manufacturing are allowed. Minor variations in width of
the keeper 10 can be compensated for by the resilient silicone rubber at
30 and 31.
This first preferred keeper design 10 also facilitates ease of maintenance.
The resilient silicone rubber 32 is injected from the inner main shaft 13
which therefore displaces air while filling the voids. This produces an
airtight seal that prevents the entrance of bacteria, saliva, or food
after the silicone rubber sets.
The first embodiment keeper of the present invention 10 incorporates two
safety features to protect the integrity of the jawbone at 80 and 89. That
is, if an extreme frontal force hits the prosthesis and endangers the
integrity of the jawbone, that force will disengage the keeper from its
silicone rubber at 30 and the keeper 10 would then be expelled from the
tissue extension 20. The conical shape 16 of the keeper helps to promote
this purpose. If an extreme frontal force hits the prosthesis, the keeper
is going to break off at its narrower end thus protecting the jawbone from
that force, assuming the keeper has not been expelled by the force. In
either case, the keeper can be replaced as simply as an electric fuse can
be replaced after an overload condition.
These safety features are distinct from and an improvement over the prior
art.
In the second preferred embodiment of the keeper which is illustrated in
FIGS. 5, 6, 7, 8, 9 and 10, the silicone resilient member 60 to 66 is also
injected through the main shaft 113 of the keeper 110. FIG. 10 shows a
section of the mold which surrounds the keeper 110 during injection. After
the silicone rubber is cured in the mold, then the mold is removed. A base
support 118 located below the lower end of the keeper 110 is formed by the
silicone rubber as it exits the keeper 110 through the opening 119 located
at the bottom end.
The keeper 110 has a plurality of shock-absorbing members 60-66 along the
keeper periphery. A plurality of mini-suction cups 64 are among the
shock-absorbing members. These suction cups 64 extend from all around the
main body 117 of the keeper 110 at different levels. They are formed by
the injection molding process described above and illustrated in FIG. 10.
The resilient silicone rubber exits throughout the vents 116 along the
outer surface of the keeper 110 to fill each of a plurality of cavities
124 in the mold where the suction cups 64 are formed. Collectively, the
suction cups 64 function like the periodontal ligament of natural tooth
absorbing tensile, compression and shearing stress from the masticatory
forces.
Also among the shock-absorbing members is a seal 61 located at the keeper
midsection to interface where the keeper 110 exits the tissue extension 70
above the cylinder 75. The seal 61 under-surface is beveled at section 62
to facilitate its introduction through the extension 70 opening. The
tissue extension is further defined by grooves 71, 72 and 73 that engage
and retain the elastic-resilient seal 61, and the keeper 110 in a central
upright position.
The outside shape of the tissue extension 70 for the second preferred
embodiment of the keeper 110 is similar to the outside shape of the tissue
extension 20 for the first preferred embodiment. However, the second
preferred embodiment extension 70 as illustrated differs on the inside in
two ways. First, it has a hexagonal socket 69 at its lower inside that is
designed for the use of an allen wrench to secure the abutment to a
foundation fixture. That socket 69 later on is going to receive the keeper
base support 66 which, although cylindrical in FIG. 9, can also be
hexagonal. Second, it has grooves 71, 72 and 73 to hold the seal members
61, 62 and 63 in place.
The second preferred embodiment keeper 110 has the same safety features of
the first preferred embodiment 10, but the keeper 110 of the second
embodiment can be mechanically removed by the patient to perform thorough
hygiene cleaning and self-inspection of the abutment's socket and the
keeper-prosthesis itself. The keeper 110 is engaged by mechanical suction
and engagement rather than by composition adhesion used for the keeper 10
of the first preferred embodiment.
This capability will enable the oral hygiene of the patient even though the
socket is sealed from air.
The implant 40 of the second preferred embodiment is the same foundation
fixture of the first preferred embodiment.
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