U.S. patent application number 12/167018 was filed with the patent office on 2009-03-05 for dental implant prosthetic device with improved osseointegration and shape for resisting rotation.
Invention is credited to Matthew Lomicka, Srilakshmi Vishnubhotla.
Application Number | 20090061389 12/167018 |
Document ID | / |
Family ID | 40549886 |
Filed Date | 2009-03-05 |
United States Patent
Application |
20090061389 |
Kind Code |
A1 |
Lomicka; Matthew ; et
al. |
March 5, 2009 |
DENTAL IMPLANT PROSTHETIC DEVICE WITH IMPROVED OSSEOINTEGRATION AND
SHAPE FOR RESISTING ROTATION
Abstract
A dental implant has a body that generally defines a
coronal-apical axis and a porous tantalum metal portion that is
disposed at the body for engaging bone and having a non-circular
outer periphery extending around the axis. The non-circular outer
periphery is shaped to engage a bore in a bone to resist a
torsional force that is applied to the dental implant and around
the coronal-apical axis.
Inventors: |
Lomicka; Matthew; (Vista,
CA) ; Vishnubhotla; Srilakshmi; (San Diego,
CA) |
Correspondence
Address: |
FITCH EVEN TABIN AND FLANNERY
120 SOUTH LA SALLE STREET, SUITE 1600
CHICAGO
IL
60603-3406
US
|
Family ID: |
40549886 |
Appl. No.: |
12/167018 |
Filed: |
July 2, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11847476 |
Aug 30, 2007 |
|
|
|
12167018 |
|
|
|
|
Current U.S.
Class: |
433/201.1 |
Current CPC
Class: |
A61C 8/006 20130101;
A61C 8/0043 20130101; A61C 8/0013 20130101; A61C 8/0018 20130101;
A61C 8/0024 20130101; A61F 2220/0041 20130101; A61F 2002/30433
20130101; A61C 8/0006 20130101; A61C 8/0012 20130101; A61C 8/0089
20130101 |
Class at
Publication: |
433/201.1 |
International
Class: |
A61C 8/00 20060101
A61C008/00 |
Claims
1. An implant, comprising: a body generally defining a
coronal-apical axis; and a porous tantalum portion disposed at the
body for engaging bone and having a non-circular outer periphery
extending around the axis.
2. The implant of claim 1 wherein the non-circular outer periphery
is shaped to engage a bore in bone to resist a torsional force
applied to the implant and around the axis while the implant is
disposed within the bore.
3. The implant of claim 2 wherein the non-circular outer periphery
is shaped to resist torsion while disposed in a circular bore.
4. The implant of claim 1 wherein the outer periphery has three or
more distinct face portions.
5. The implant of claim 4 wherein the outer periphery includes a
regular polygon.
6. The implant of claim 1 wherein the outer periphery is asymmetric
about at least one axis of the outer periphery that is transverse
to the coronal-apical axis.
7. The implant of claim 1 wherein the outer periphery has a closed,
curved shape.
8. The implant of claim 1 wherein the outer periphery is at least
one of elliptical, obround, and oval in cross-section.
9. The implant of claim 1 wherein the outer periphery is configured
and dimensioned to grate bone pieces off of a sidewall forming a
bore in bone that receives the dental implant.
10. The implant of claim 1 wherein the outer periphery has a
maximum width dimension that is greater than a diameter dimension
of the bore.
11. The implant of claim 10 wherein the maximum width dimension is
greater than the diameter dimension of the bore by approximately
0.008 to 0.18 mm.
12. The implant of claim 1 wherein the body has a main portion and
a plurality of roots having porous tantalum and extending apically
from the main portion wherein the non-circular outer periphery is
at the main body and the plurality of roots extend below the
non-circular outer periphery.
13. The implant of claim 12 wherein at least one of the extending
roots has a coronal end portion adjacent the main portion and an
apical end portion, and wherein the coronal end portion has a
diameter or width dimension greater than the diameter or width
dimension of the apical end portion.
14. The implant of claim 1 wherein the body comprises a coronal end
portion for receiving a driving tool for press-fit installation of
at least a portion of the body into a bore in bone.
15. The implant of claim 1 wherein the implant has a full length,
and wherein the non-circular outer periphery extends axially along
the implant less than the full-length.
16. The implant of claim 1 wherein the implant has a coronal end
portion, and wherein the outer periphery only extends on the
coronal end portion.
17. The implant of claim 1 wherein the body has at least one
outwardly, radially extending annular tooth made of porous metal
shaped to resist pull-out of the dental implant from a bore in the
bone.
18. The implant of claim 17 wherein the body has an array of the
teeth spaced along the axis.
19. The implant of claim 1 wherein the body has a coronal end
portion and an apical end portion, and wherein the body tapers
inwardly as it extends from the coronal end portion to the apical
end portion.
20. The implant of claim 1 wherein the implant is a dental
implant.
21. The implant of claim 1 wherein the porous tantalum portion is
partially filled with a resorbable material.
22. The implant of claim 21 wherein the resorbable material
comprises at least one of: PLA, PGA, PLGA, PHB, PHV,
polycaprolactone, polyanhydrides, and polyorthoesters.
23. An implant, comprising: a body generally defining a
coronal-apical axis; and a porous tantalum portion disposed at the
body for engaging bone within a bore on an animal or human body and
having a non-circular outer periphery extending around the axis;
wherein the non-circular outer periphery is shaped to engage the
bore in the bone of the animal or human body to resist a torsional
force applied to the implant and around the axis while the implant
is disposed within the bore.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of pending U.S.
patent application Ser. No. 11/847,476, filed Aug. 30, 2007, which
is incorporated herein by reference in its entirety for all
purposes.
FIELD OF INVENTION
[0002] The present invention relates to bone implant prosthetic
devices and, in particular, to a dental prosthetic device with a
shape for resisting torsional force applied to the device.
BACKGROUND
[0003] A dental implant or fixture is surgically implanted into a
patient's upper or lower jaw to directly or indirectly anchor and
support prosthetic devices, such as an artificial tooth. The
implants are usually placed at one or more edentulous sites in a
patient's dentition at which the patient's original teeth have been
lost or damaged in order to restore the patient's chewing function.
In many cases, the implant anchors a dental abutment, which in turn
provides an interface between the implant and a dental restoration.
The restoration is typically a porcelain crown fashioned according
to known methods.
[0004] One form of a prosthetic device is a unitary or one-piece
implant device with a bone-engaging implant portion and an abutment
portion integral with the implant portion. Another form of a
prosthetic device is a multiple piece device where the abutment is
assembled onto the implant. A desire still exists, however, to
improve the osseointegration characteristics of such dental
devices.
[0005] One problem with one-piece dental devices is that the
titanium and other materials used for such devices often are an
unattractive color. Thus, when the abutment portion of the device
below a prosthetic tooth but above the gum or gingival tissue is
visible and does not have the color of natural teeth, the dental
device provides a non-esthetically pleasing appearance in a
person's mouth. Other known dental devices that have the color of
natural teeth typically provide inadequate strength resulting in
relatively frequent replacement or repair of the device.
[0006] Whether or not the dental implant device is a one-piece or
part of a multiple piece device where the abutment is assembled
onto the implant, the implant is usually either threaded or
press-fit into a bore which is drilled into the patient's mandible
or maxilla at the edentulous site. The press-fit implant is
inserted by applying a force to the coronal end of the implant in
an insertion direction. For a threaded implant, self-tapping
threads may be provided for initial stability of the implant
immediately after surgery. Before biologic integration has time to
take place, the threads resist tension, twisting, or bending loads
applied to the implant. Additionally, patients prefer to leave the
initial surgery with some type of restoration and it has further
been shown that the healing of the soft and hard bone tissue is
improved if the implant is loaded after surgery.
[0007] The surgical procedure for inserting the threaded implants,
however, can be complicated and requires that the threaded implants
be turned into place, which further requires the use of special
tools and inserts. The torque needed to place the implant into the
jaw can be high and may require tapping of the bore on the jaw,
which adds yet another step to the surgical procedure where tapping
typically is not desired. Also with threaded implants, it is often
difficult to achieve optimal esthetics where, for example, a
prosthetic is held at an ideal orientation by the implant because
the geometry of the thread establishes a fixed relationship between
the final vertical and rotational orientation of the implant such
that a vertical adjustment requires a rotational adjustment and
vice-versa.
[0008] Alternatively, a press fit implant has a much simpler
surgical procedure. For a press fit implant, the implant is
inserted by applying a force to the coronal end of the implant in
an insertion direction. Unlike the self-tapping, threaded dental
implants, however, the current press fit designs provide
insufficient frictional contact with the bore to adequately
restrict the rotation of the implant within the bore or prevent the
implant from pulling out of the bore that can be caused by
mastication forces. Thus, the current press fit designs provide
very little initial stability and are not well suited for early and
immediate loading procedures that are currently used in dentistry.
A desire still exists, therefore, to provide press fit implants
with greater resistance to mastication forces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a cross-sectional view of a first embodiment of a
one-piece dental implant prosthetic device in accordance with the
present invention;
[0010] FIG. 2 is an enlarged fragmentary view of a porous tantalum
portion for any of the embodiments herein and in accordance with
the present invention;
[0011] FIG. 3 is an enlarged sectional view of a porous tantalum
portion and a filler material for a number of embodiments herein
and in accordance with the present invention;
[0012] FIG. 4 is a cross-sectional view of a second embodiment of a
one-piece dental implant prosthetic device in accordance with the
present invention;
[0013] FIG. 5 is a cross-sectional view of a third embodiment of a
one-piece dental implant prosthetic device in accordance with the
present invention;
[0014] FIG. 6 is a side elevational view of an instrument used to
aid in press-fitting an implant into a jaw bone in accordance with
the present invention;
[0015] FIG. 7 is a side elevational view of an alternative implant
configured for press-fitting in accordance with the present
invention;
[0016] FIG. 8 is a top view of the alternative implant of FIG.
7;
[0017] FIG. 9 is a side elevational view of another implant
configured for press-fitting in accordance with the present
invention;
[0018] FIG. 10 is a top view of the implant of FIG. 9;
[0019] FIG. 11 is a graphical representation of the overall elastic
modulus for a porous metal/composite material structure as a
function of an elastic modulus of a filler material for the
structure;
[0020] FIG. 12 is a schematic diagram showing the boundary
conditions used for computing Young's modulus for the porous
metal/composite material structure shown graphically in FIG.
11;
[0021] FIG. 13 is a side elevational view of another implant
configured for press-fitting in accordance with the present
invention;
[0022] FIG. 14 is a top view of the implant in FIG. 13;
[0023] FIG. 15 a side elevational view of another implant
configured for press-fitting in accordance with the present
invention;
[0024] FIG. 16 is a side, cross-sectional view of a bore holding
the press-fit implant of FIG. 15 in accordance with the present
invention;
[0025] FIG. 17 is a simplified and exaggerated top cross-sectional
view taken along line XVII-XVII on FIG. 16;
[0026] FIG. 18 is a side elevational view of another implant
configured for press-fitting in accordance with the present
invention;
[0027] FIG. 19 is a top view of the implant in FIG. 18;
[0028] FIG. 20 is a side elevational view of a multiple-root
implant in accordance with the present invention;
[0029] FIG. 21 is a top view of the multiple-root implant of FIG.
20 in accordance with the present invention;
[0030] FIG. 22 is a side elevational view of a three-root implant
in accordance with the present invention; and
[0031] FIG. 23 is a side, perspective view of a four-root implant
in accordance with the present invention.
DETAILED DESCRIPTION
[0032] Referring to FIG. 1, there is illustrated a pre-fabricated
one-piece dental prosthetic device 20. The one-piece dental device
20 has a bone engaging endosseous portion or implant portion 22 on
a distal or apical end portion 24 of the device 20 to extend into
the maxillae or mandible (either being otherwise generally referred
to as the jaw bone). The implant portion 22 supports an abutment
portion 26 integrally formed with the implant portion 22 and
disposed at a proximal or coronal end portion 28 of the one-piece
dental device 20. The abutment portion 26 may include an abutment,
an integrally formed dental restoration (i.e., a (near) net-shape
tooth or crown), and/or the transmucosal portion of a single stage
dental implant. In the form shown in FIG. 1, the abutment portion
26 extends through and above the gingival tissue to support and
receive a tooth shaped prosthetic or other types of prosthetic
pieces or devices. The one piece dental device 20 also has a porous
metal portion or matrix 30 to improve the osseointegration of the
bone on at least the implant portion 22. Further, the one piece
dental device 20 may have an outer portion 32 that has a color
generally replicating the color of natural teeth so that if the
abutment portion 26 is still exposed after a prosthetic is placed
on the abutment portion, it will still have an aesthetic appearance
in a person's mouth. The one-piece dental prosthetic device
disclosed herein may also have other geometries, such as those
found in U.S. patent application Ser. No. 11/380,569, which is
incorporated herein by reference. These features are explained in
detail below.
[0033] As mentioned, the porous metal portion 30 extends on the
implant portion 22 where it can be placed in contact with the bone,
and in one form, is a porous tantalum portion 40 which is a highly
porous biomaterial useful as a bone substitute and/or cell and
tissue receptive material. An example of such a material is
produced using Trabecular Metal.TM. technology generally available
from Zimmer, Inc., of Warsaw, Ind. Trabecular Metal.TM. is a
trademark of Zimmer Technology, Inc. Such a material may be formed
from a reticulated vitreous carbon foam substrate which is
infiltrated and coated with a biocompatible metal, such as
tantalum, etc., by a chemical vapor deposition ("CVD") process in
the manner disclosed in detail in U.S. Pat. No. 5,282,861, the
disclosure of which is fully incorporated herein by reference.
Other metals such as niobium, or alloys of tantalum and niobium
with one another or with other metals may also be used.
[0034] Generally, as shown in FIG. 2, the porous tantalum structure
40 includes a large plurality of ligaments 42 defining open spaces
44 therebetween, with each ligament 42 generally including a carbon
core 46 covered by a thin film of metal 48 such as tantalum, for
example. The open spaces or pores 44 between ligaments 42 form a
matrix of continuous channels having substantially no dead ends,
such that growth of cancellous bone through porous tantalum
structure 40 is uninhibited. The porous tantalum may include up to
75%-85% or more void space therein. Thus, porous tantalum is a
lightweight, strong porous structure which is substantially uniform
and consistent in composition, and closely resembles the structure
of natural cancellous bone, thereby providing a matrix into which
cancellous bone may grow to anchor dental device 20 into the
surrounding bone of a patient's jaw.
[0035] The porous tantalum structure 40 may be made in a variety of
densities in order to selectively tailor the structure for
particular applications. In particular, as discussed in the
above-incorporated U.S. Pat. No. 5,282,861, the porous tantalum may
be fabricated to many different desired porosity and pore sizes,
and can thus be matched with the surrounding natural bone in order
to provide an improved matrix for bone in-growth and
mineralization. This includes a gradation of pore size on a single
implant such that pores are larger on an apical end to match
cancellous bone and smaller on a coronal end to match cortical
bone, or even to receive soft tissue in growth. Also, the porous
tantalum could be made denser with fewer pores in areas of high
mechanical stress. Instead of smaller pores in the tantalum, this
can also be accomplished by filling all or some of the pores with a
solid material which is described in further detail below.
[0036] To provide the additional initial mechanical strength and
stability to the porous structure, the porous structure may be
infiltrated with filler material such as a non-resorbable polymer
or a resorbable polymer. Examples of non-resorbable polymers for
infiltration of the porous structure may include a polyaryl ether
ketone (PAEK) such as polyether ketone ketone (PEKK), polyether
ether ketone (PEEK), polyether ketone ether ketone ketone (PEKEKK),
polymethylacrylate (PMMA), polyetherimide, polysulfone, and
polyphenolsulfone.
[0037] Examples of resorbable polymers may include PLA, PGA, PLGA,
PHB, PHV, and copolymers thereof, polycaprolactone, polyanhydrides,
and polyorthoesters. By providing additional initial mechanical
strength and stability with a resorbable filler material, a
titanium reinforcing implant core may not be required. The
resorbable material would resorb titanium as the bone grows in and
replaces it, which maintains the strength and stability of the
implant.
[0038] Referring to FIG. 1, the porous metal portion 30 forms a
sleeve 34 that at least partially surrounds a core 36. The sleeve
34, core 36, or both as shown may form a strong, reinforcing post
that extends into the abutment portion 26 to reinforce the
abutment. Here, the sleeve 34 substantially entirely encapsulates
the core 36 although many other configurations are possible where
the porous metal portion 30 covers only a part of the length or
circumference of the core 36 whether continuously or spaced at
intervals.
[0039] The core 36 is made of a suitable biocompatible material,
such as titanium although the core 36 may also be made of other
biocompatible materials such as at least one of the following:
titanium alloy, stainless steel, zirconium, and
cobalt-chromium-molybdenum alloy to name a few examples. The core
36 can be inserted into the sleeve 34 by various known methods such
as press-fitting, diffusion bonding, or mechanical threading of the
core 36 into the porous metal sleeve 34. Where the core 36 is
press-fit into the sleeve 34, a fastening between the two parts is
achieved by friction after the two parts are pushed together. The
friction that holds the parts together is often greatly increased
by compression of one part against the other, which relies on the
tensile and compressive strengths of the materials of the engaged
parts.
[0040] Diffusion-bonding of the core 36 and sleeve 34 is a
solid-state joining process that involves holding components under
load at an elevated temperature. The process is dependent upon a
number of different parameters, such as time, applied pressure,
bonding temperature and method of heat application. Alternatively,
mechanically threading the core 36 into the sleeve 34 involves
providing the sleeve with a threaded bore formed at its interior 35
which mates with a threaded male portion of the core 36. Direct
Chemical Vapor Deposition (CVD) bonding can also be used to bond
the core 36 with the sleeve 34. This process, like diffusion
bonding, is dependent upon a number of different parameters and
involves bonding the core 36 and sleeve 34 by depositing a
material, such as tantalum, onto the assembly at an elevated
temperature.
[0041] The one-piece device 20 also may have an esthetic material
(also referred to herein as an esthetic portion) 38 that has a
color generally replicating the color of natural teeth. In this
case, if the outer portion 32 has the esthetic portion 38 and is
disposed on the abutment portion 26, for example, and the outer
portion 32 is exposed even when a temporary or final prosthesis is
placed on the abutment portion 26, the exposed outer portion 32
will still provide an esthetically pleasing appearance.
[0042] The esthetic portion 38 may comprise either a polymer, a
composite material as disclosed in detail in commonly owned U.S.
patent application Ser. Nos. 11/420,024 and 11/622,171, which are
fully incorporated herein as mentioned above, or a ceramic
material. When the esthetic portion 38 comprises composite
materials it may include the combination of a matrix material, a
reinforcing material and a colorant. The matrix material may be a
polyaryl ether ketone (PAEK) such as polyether Ketone Ketone
(PEKK), polyether ether ketone (PEEK), polyether ketone ether
ketone ketone (PEKEKK), polymethylmethacrylate (PMMA),
polyetherimide, polysulfone, and polyphenylsulfone. The polymers
can also be a thermoset material including, without limitation,
bisphanol glycidyl methacrylate (Bis-GMA), urethane dimethacrylate
(UDMA), methylmethacrylate (MMA), triethylene glycol dimethacrylate
(TEGDMA), a combination of thermoset plastics, or a combination of
thermoset and thermoplastics. Additionally, they can be comprised
of, without limitation, a large class of monomers, oligomers and
polymers, such as acrylics, styrenics and other vinyls, epoxies,
urethanes, polyesters, polycarbonates, polyamides, radiopaque
polymers and biomaterials.
[0043] The reinforcing material may comprise, to name a few
possible examples, at least one selected from the group comprising
carbon, Al2O3, ZrO2, Y2O3, Y2O3-stabilized ZrO2, MgO-stabilized
ZrO2, E-glass, S-glass, bioactive glasses, bioactive glass
ceramics, calcium phosphate, hydroxyapatite, TiO2, Ti, Ti6Al4V,
stainless steel, polyaryl ether ketones (PAEK) such as polyethyl
ethyl ketone (PEEK), polyethyl ketone ketone (PEKK), and an aramid.
The geometry of the reinforcing material may include fibers,
particulates, variable diameter fibers and fibers fused with
particulates on the fiber surfaces. The colorant may be titanium
dioxide as one example.
[0044] In one example, the esthetic portion 38 may comprise about
55% by weight of the composite material PEKK as the matrix
material, about 35% by weight of the composite material of E-glass
fibers as the reinforcing material, and about 10% by weight of the
composite material of titanium dioxide particles as the colorant.
In another example, the esthetic portion 38 may comprise about 53%
by weight of the composite material PEKK as the matrix material,
about 35% by weight of the composite material of E-glass fibers as
the reinforcing material, and about 12% by weight of the composite
material of titanium dioxide particles as the colorant.
[0045] In one form, the outer portion 32 has an exterior separate
from the porous tantalum portion so that the outer portion is
substantially free of the porous tantalum portion. This results in
the exterior of the outer portion 32 forming a smooth skin layer
comprised substantially of the esthetic material, where the skin
layer of esthetic material may have a thickness of approximately
0.05 to about 3.0 mm. Furthermore, the smooth skin layer of the
outer portion 32, when placed along the implant portion 22 or
within the transmucosal layer 52 (i.e., gingival region of the
prosthetic) on the abutment portion 26, forms a relatively solid,
pore-free outer layer. This limits attachment of soft tissue and
bacteria onto the outer portion 32 and limits the in-growth of the
epithelium so that it does not interfere with bone growth against
the implant portion 22. The outer portion 32 may be disposed on at
least one of a coronal end of the coronal end portion 28, a side of
the coronal end portion 28, and the transmucosal layer 52 on the
abutment portion 26, but preferably on substantially all three
areas. Thus, a smooth, non-porous outer portion 32 may be provided
from the upper end 50 on the abutment portion 26, along the
transmucosal region 52 of the abutment portion, and in one case,
down to the point where the abutment portion 26 narrows and ends
and the implant portion 22 begins. In another form, as shown, a
smooth surface 54 may also be provided on the coronal end 56 of the
implant portion 22 if desired.
[0046] Referring to FIGS. 1 and 3, in another form, the esthetic
portion 38 may at least partially impregnate the porous metal
portion 30 so that the esthetic portion acts as a filler material
and/or the porous metal portion 30 reinforces the esthetic portion
38. In such cases, the esthetic portion 38 fills at least a portion
of the pores 44 of the porous metal portion 30. In one form, the
esthetic portion 38 substantially completely fills the pores 44
near the coronal end 56 of the implant portion 22 and forms the
smooth exterior skin layer 54 mentioned above. The pores 44 of the
porous metal portion 30 near the distal end or apical end 24 of the
implant portion 22 are substantially free of the esthetic material
38, which allows in-growth of bone to anchor the one-piece dental
device 20 to the jaw. Accordingly, there can be a general, internal
dividing line above which the porous tantalum is substantially
impregnated with esthetic material and below which it is not,
similar to the diagram in FIG. 3, and applicable to any of the
dental implant devices described herein.
[0047] To impregnate the porous metal portion 30 with the esthetic
portion 38, the polymers or composites that make up the esthetic
material can be injection-molded into the porous metal portion 30
such as on the sleeve 34, so that the polymer or composite material
infiltrates the vacant open spaces 44 forming a solid mass of the
polymer or composite material with metal reinforcement.
Furthermore, injection-molding of the polymer or composite material
may also be used to form the non-porous skin layer with the outer
portion 32 as described above.
[0048] The esthetic portion 38 can also be reinforced by the porous
metal portion 30 by an insert-molding process. Insert molding is an
injection molding process whereby the esthetic portion 38 is
injected into a cavity and around an insert piece, such as the
sleeve 34 of porous tantalum, placed into the same cavity just
prior to molding, resulting in a single piece with the insert
encapsulated by the esthetic portion 38. The impregnation of the
porous tantalum portion 30 as shown in FIG. 3 was performed by
insert-molding. Other molding processes such as compression
molding, resin transfer molding or any other process known in the
art may be employed.
[0049] Mechanical bonding also takes place during the insert
molding process. Mechanical bonding can occur by shrinking of the
esthetic portion 38 around the sleeve 34 as the esthetic portion
cools or by filling in irregularities in the surface of the sleeve
34. Mechanical bonding further can occur when the esthetic material
38 infiltrates the open spaces within the pores 44 of the porous
sleeve 34.
[0050] When the esthetic portion 38 is composed of a ceramic
material, such as dental porcelain, the ceramic material can be
placed in the porous metal portion 30 via sintering and an
enameling process. The enameling process includes fusing powdered
glass to the porous metal portion 30 by firing at extremely high
temperatures. The ceramic powder can melt and flow, and hardens
into a smooth, durable ceramic coating that can be placed on the
porous tantalum portion and can be inlaid within the pores 44 of
the porous tantalum portion. The ceramic material, after firing and
cooling, becomes a smooth, hard and very durable material.
[0051] A microscopic model can be obtained to predict the overall
mechanical properties of the porous metal/composite material-filled
structure. For instance, a relationship between the strength of the
porous metal/composite material and the strength of a particular
filler material (shown in FIG. 11) can be obtained by using a
finite element model (as shown in FIG. 12). More specifically, the
prediction of the porous metal/composite material structure's
overall mechanical behavior can be based on Representative Volume
Element (RVE) theory. The RVE theory comprises constructing a
representative portion of the material's microstructure (an "RVE")
and subjecting it to virtual testing. The overall mechanical
behavior of the RVE is found to be equivalent to the composite
material it represents.
[0052] As an example, an RVE program such as commercially available
FE software, ANSYS version 10 (available from ANSYS, Inc.,
Canonsburg, Pa., USA) is used to generate a two-dimensional
stochastic Voronoi cell structure based on RVE theory to simulate
random microscopic struts of the porous metal at the microscopic
level. Specifically, the porous metal/composite material structure
was meshed using 8-node hexagon mesh. The porous metal structure
was simulated using tantalum metal material properties as a
bi-linear, elasto-plastic material (i.e., having Young's Modulus
E=179 GPa, Poisson's ratio .mu.=0.34, Yield stress .sigma.y=190 MPa
and Tangent Modulus Et=17 GPa). The pores between the struts were
modeled to be impregnated with a composite material as a filler
material similar to that shown in FIG. 3 except all pores were
filled for the test. The filler composite material was modeled as a
linear elastic material having a varied elastic modulus and
Poisson's ratio equal to 0.4.
[0053] To compute the overall Young's modulus (E) of the structure,
a boundary condition was applied to the finite element model as
shown in FIG. 12 to simulate compression testing. The finite
element model has a fixed, constrained face with an area (Axx)
formed by a length in the x direction (Dx) and a length in the y
direction (Dy). All other faces are unconstrained along the
x-direction. The boundary or test condition used was to apply a
uniform strain field with 0.1% strain along the x-direction to the
RVE and the finite element model. For instance, in order to compute
Exx (Young's modulus along the x-direction), a displacement Ux
represents an applied strain where Ux=0.001Dx. Therefore, Exx can
be computed as follows:
E xx = 1000 .times. R x A xx ##EQU00001##
where .SIGMA.R.sub.x represents the summation of reaction forces at
the constrained faces. Due to its structural symmetry, the Young's
modulus along the x, y and z directions is the same. Therefore,
E=E.sub.xx=E.sub.yy=E.sub.zz. As a result, the overall elastic
modulus, E, of the porous metal impregnated with the composite
material was plotted versus the filler (i.e., composite material)
elastic modulus, Ef, and is shown in FIG. 11. A linear regression
was used to fit the data points and an equation was obtained
expressing the overall elastic modulus, E, for the porous
metal/composite material structure as a function of the filler
elastic modulus, Ef, or E=1760+1.6563 E.sub.f, and further having
an R-squared value of 0.9935, where R-squared is a statistical
measure of the fraction of variance expressed by the model.
[0054] In another form, the one-piece dental device 20, as well as
the other implants described below, may have multiple textured
surfaces as described in detail in U.S. Pat. No. 5,989,027,
assigned to the assignee of the present invention, the disclosure
of which is expressly incorporated herein by reference. For
example, the sleeve 34 of porous tantalum may have an increasing
porosity from the proximal end 28 toward the distal end 24 of the
one-piece dental device 20. Thus, the sleeve 34 may be formed of
substantially solid, non-porous tantalum near the proximal end 28,
within the transmucosal region 52 on the abutment portion 26,
and/or slightly distally of the abutment portion 26 to provide a
seal with the surrounding gingiva such that plaque or bacteria
cannot lodge on or deposit within the sleeve 34 near the gumline of
the patient should the upper portion of the sleeve 34 be exposed to
the oral cavity. Alternatively, the surface of the abutment portion
26 of the core 36 could be formed of smooth, polished titanium or
other materials providing such a smooth, solid finish to allow
ready removal of bacterial plaque deposits by conventional oral
hygiene techniques. As another option, bands of titanium or other
materials may be provided with a solid yet roughened surface, such
as at the coronal end 56 of the implant portion 22 to promote some
bone growth while still limiting at least some soft-tissue and
bacterial growth.
[0055] In addition to these approaches, the porosity of the porous
metal portion 30 of the sleeve 34 can increase gradually or at
intervals as desired and as the sleeve 34 extends distally to
promote maximum bone in-growth and osseointegration at the distal
end portion 24 of the one-piece dental device 20. For this purpose,
the pores 44 of the porous metal structure 30 may be formed with
increasingly larger sizes from the proximal end portion 28 to the
distal end portion 24 of the one-piece dental device 20.
[0056] Also, the sleeve 34 may be attached to the core 36 of the
one-piece dental device 20 in a manner wherein, after
osseointegration of the sleeve 34 into the surrounding bone, the
core 36 is slightly movable relative to the sleeve 34 in order to
dissipate forces which are imposed upon the one-piece dental device
20, such as mastication forces, for example. In one embodiment, the
sleeve 34 may be secured to the core 36 via an adhesive or cement
material which is slightly compressible, such that when mastication
or other forces are imposed upon the abutment portion 26, the core
36 may move slightly relative to the sleeve 34 whether within the
abutment portion 26 or within the implant portion 22. Such adhesive
or cement materials include acid-base reaction formulations such as
zinc phosphate, zinc oxide/eugenol, zinc polycarboxylate, glass
ionomer, or resin based formulations similar to that of resin-based
dental restorative filling materials. One specific example is a
dental adhesive/bonding agent that is composed of monomers of
hydroxyethyl methacrylate (HEMA), 4-methacryloxyethyl trimellitate
anhydride (4-META) and an organophosphate (e.g.,
10-methacryloyoxydecamethylene phosphoric acid, MDP). In other
embodiments, a compression ring, a spring, or another type of
"shock absorbing" structure may be fitted between the core 36 and
the sleeve 34 to allow for relative movement therebetween.
[0057] Referring to FIG. 4, there is illustrated a one-piece dental
device 120 that similarly includes a core 122 and a porous metal
portion 124 in the form of a sleeve 138 that at least partially
surrounds the core 122 and may be made of a porous tantalum such as
Trabecular Metal.TM.. The dental device 120 also has an abutment
portion 126 at a proximal end portion 128 of the one-piece dental
device 120 and an implant portion 130 at a distal end portion 132
of the one-piece dental device 120. An outer portion 134 having an
esthetic material 142, similar to esthetic material 38, has a color
generally replicating the color of natural teeth and is disposed at
least at the abutment portion 126 of the device 120 as described
further below.
[0058] For the one-piece dental device 120, the core 122 also is
made of a porous metal such as tantalum and may be received by an
interior or bore 137 of the sleeve 138. The core 122 can be
inserted into the sleeve 138 by various methods such as press-fit
or mechanical threading as described above. Alternatively, the
sleeve 138 may be integrally formed with the core 122. While the
porous metal portion 124 generally remains on the implant portion
130 (i.e. it does not extend substantially onto the abutment
portion 126 in this example), the porous metal core 122, in one
form, widens and forms the bulk of the abutment portion 126 and
forms a strong, reinforcing post that extends from within the
implant portion 130 to within the abutment portion 126. Thus, in
this case, the porous metal, and therefore, the porous metal
portion 134, may be described as generally extending throughout the
prosthetic device 120.
[0059] For the dental device 120, the core 122 is impregnated with
a filler while the porous metal portion 124 forming the sleeve 138
and that forms the exterior of the implant portion 130 for engaging
bone is substantially free of the esthetic material. The filler may
be a composite or polymer material, which may be the same as the
esthetic material 142, and may fill in the vacant open spaces in
the porous tantalum as previously discussed above with the
embodiment of FIG. 1 and as shown in FIG. 3, except that here, the
composite or polymer material fills the pores of the entire length
of the core 122 from the proximal end portion 128 to the distal end
portion 132. The core 122 may be impregnated by any of the
previously discussed methods, such as by injection-molding.
[0060] The esthetic material or esthetic portion 142 of the
one-piece dental device 120, as mentioned above for the dental
device 20, may be disposed at least the outer portion 134 at the
abutment portion 126 for esthetics and to at least partially cover
the porous tantalum portion of the core 122 at the proximal portion
128 to limit gingival tissue growth there. Thus, at the proximal
end portion 128 of the core 122, the outer portion 134 forms a
smooth esthetic skin layer that is substantially free of porous
tantalum, and is located around substantially the entire abutment
portion 126. The outer portion 134 may have a skin layer that is
approximately 0.05 to about 3.0 mm thick. With this configuration,
the porous sleeve 138 substantially covers the implant portion 130
of the outer layer of the implant 120 to promote bone growth while
the exposed abutment portion 126 with a solid, smooth esthetic
outer surface limits the in-growth of soft tissue and bacterial
growth against the abutment portion 126.
[0061] In one variation of the one-piece dental device 120, a
thickened, outer and upper portion or layer 140 is formed coronally
of the core 122 at the coronal end portion 128 and is made of the
esthetic material. The upper layer 140 can be formed by injecting
the esthetic material onto the porous structure of the tantalum
core 122 until a coronal or terminal end 136 of the core 122 is
coated with several millimeters of esthetic material. The layer 140
is substantially free of porous metal so that it can be easily
shaped by a practitioner for receiving another dental device or
restoration such as a dental prosthesis or final crown, for
example.
[0062] In another alternative, one or more gaps 144 within the
upper layer 140 encourages soft tissue in-growth to form a seal
around the perimeter of the implant 120 at the location of the gap
144. This seal coupled with the non-porous outer surface formed by
the esthetic portion 142 on the abutment portion 126 forms a
barrier that limits bacteria, epithelium or other contaminants from
passing through the porous metal and into a bone integration area
along the implant portion 130. While the gap 144 is shown as a
continuous gap around the upper layer 140 it will be appreciated
that many other forms are possible, such as non-continuous gaps,
spaced holes, or other uniform or more randomly placed openings, to
name a few examples.
[0063] Referring to FIG. 5, there is illustrated a third embodiment
of a one-piece dental device 220 including a porous metal portion
222 of tantalum or other materials as described above, and an outer
portion 240 having a color generally replicating the color of
natural teeth and formed by an esthetic portion or material 224 on
an abutment portion 232. The porous tantalum portion 222 forms an
implant portion 230 at a distal or apical end portion 228 of the
dental device 220. The porous metal portion 222 also forms a
reinforcing core 236 of the abutment portion 232 at the coronal end
portion 234 of the dental device 220. While the core 236 is shown
to extend approximately half the height of the abutment portion
232, it will be understood that other variations are possible
including the core 236 extending at or near the terminal coronal
end 234 of the abutment portion 232 or being much shorter such that
the core 236 extends a relatively small distance into the abutment
portion 232. In the form illustrated, the core 236 does not extend
near the terminal coronal end 234 so that the esthetic portion 224
disposed coronally of the core 236 is separate from the porous
metal portion 222 and is substantially free of porous metal so that
the end 234 is easily shaped similar to coronal upper layer 140 of
dental device 120 (FIG. 4).
[0064] In one form, pores are provided generally throughout the
porous tantalum portion 222 from a coronal or proximal end 226 of
the porous metal portion 222 to the apical end portion 228, and
through the implant portion 230. The porous metal portion 222 has
pores at least partially impregnated with the esthetic portion 224.
The pores at the apical end portion 228 are substantially free of
esthetic material while the pores at the coronal end portion 226
are at least partially impregnated with the esthetic material. In
one form of device 220, the pores that are substantially free of
esthetic material form the majority of the implant portion 230
although other variations are contemplated.
[0065] It will also be appreciated that while the porous metal
portion 222 is shown to form substantially the entire implant
portion 230, other outer sleeves or layers on the porous metal
portion 222, whether presenting a solid and/or porous outer
surface, may be provided as with the other alternative embodiments
described.
[0066] It will further be appreciated that the outer portion 240
may be located on any outer part of the abutment portion 232 and
may be substantially free of the porous tantalum portion as with
the other embodiments herein. The outer portion 240 may contain a
smooth exterior layer that has a minimal width of about 1 mm on the
sides of the core 236 and/or may have a substantial thickness of
about 1 to about 5 mm above the coronal end 226 of the core
236.
[0067] Referring again to FIG. 1, to surgically implant the
one-piece dental device 20, or any of the implant devices herein,
the one-piece dental device 20 may be fitted into a bore drilled
into a patient's jaw bone at an edentulous site. In particular, the
one-piece dental device 20 may be impacted or press-fitted into the
bore to provide a firm initial seating of the one-piece dental
device 20 into the bore. For this purpose, the dental device 20 may
have a tool or driver-engaging structure 60 such as a bore (shown
in dashed line) for receiving a driver to insert the dental device
20 into the bone tissue. The bore 60 may use structures, such as an
interference fit, for releasably engaging the driver. Thereafter,
the bone tissue surrounding the one-piece dental device 20 may
osseointegrate into the open spaces 44 of the porous sleeve 34,
thereby firmly anchoring the sleeve 34 and the one-piece dental
device 20 into the surrounding bone structure. Thereafter, a
temporary or permanent prosthesis may be secured to the esthetic
portion 38 in a known manner when the esthetic portion 38 includes
an abutment.
[0068] Referring to FIGS. 6-10, a press-fitting driver 300 may be
used to press fit one-piece dental devices such as those described
above or other implants such as implants 320 and 340. Thus, while
driver 300 is described with the use of implant 320, any of the
implant-devices described herein may be used similarly with the
driver 300.
[0069] When press-fitting a dental device 320, for example, into a
bore on the jaw, it may be desirable to make the fit between the
surgical site and the press-fit implant very tight so that the
dental device 320 can achieve the required degree of stability for
immediate or early loading. To achieve the desired tight fit, it
may be difficult to press-fit the dental device 320 into the bore
by hand pressure alone. Therefore, a driver 300 may be used to
apply pressure to properly press-fit the implant into the bore to
achieve a tight fit. In contrast to osteotomes, the driver 300 is
fastened directly to the dental device 320 or to an implant
carrier, rather than to the jaw site. A single drill can be used to
create a pilot hole, or bore, in the jaw and the tip 324 of an
implant 320 can be placed into the hole. The driver 300 can be
attached to the implant 320 on the end 322 that is opposite the
apical tip 324 and a proximal portion or handle 310 of the driver
300 can then be struck with a mallet or other driving tool to
deliver a greater force to the implant 320 than could be done by
hand in order to achieve the tight fit with the hole. The driver
300 may have a bent portion 312 that extends to, and orients, the
proximal portion 310. So configured, the proximal portion 310 is
oriented in a certain position and direction (i.e., facially of the
jaw) so that an object, such as the mallet, other tool, or even a
person's hand has convenient access to the proximal portion 310
away from the area directly between the teeth and outside of the
mouth where there is more space to maneuver. The coronal end 322 of
the implant 320 may be flat to engage the driver 300 or may have a
bore similar to bore 60 on the one-piece dental device 20 (FIG. 1)
for receiving the driver 300.
[0070] Referring to FIGS. 7-10 and 13-23, implant devices also made
of porous material as mentioned above are further provided with a
shape to increase stability for early and long-term loading as well
as to limit unintentional pull out of the implant devices. More
specifically, while the implant devices may be generally or
substantially cylindrical, in one form, a porous implant device 400
as shown in FIG. 18 has a body 402 that tapers inwardly as it
extends from a coronal end portion 404 of the body 402 to an apical
end portion 406 of the body 402. With this structure, the implant
device 400 is configured to have the coronal end portion 404 with a
larger width dimension than the width dimension of the apical end
portion 406. This allows the implant device 400 to expand the bone
as the body 402 is inserted into a bore that has a diameter smaller
than the maximum width of the body 402, which forms an interference
fit. Implant 340 (FIG. 7) also is provided with such an optional
taper.
[0071] This tapered structure also provides a geometry that is
closer to the geometry of the natural tooth. Thus, the slope of the
taper may be customized to more closely match the slope of the
natural tooth being replaced by the implant device 400. It will be
understood that any of the forms of the implant device provided
herein may have a taper that forms an interference fit.
[0072] Referring to FIGS. 7-8, additionally or alternatively, the
implant devices may have an outer periphery shaped to restrict
rotation of the implant device within a bore in the jaw bone to
create a further interference fit. In one form, implant device 340
has a body portion or body 350 that generally defines a central,
coronal-apical axis L1. The implant device 340 also has a porous
portion 352 at the body 350 as described above. The porous portion
352 also is disposed at a non-circular, outer periphery portion 354
on the body 350. The non-circular outer periphery 354 at least
extends generally around the coronal-apical axis L1. Thus, while
the non-circular outer periphery 354 is at least partially made of
the porous material, it is entirely made of the porous material in
the illustrated form.
[0073] The non-circular outer periphery portion 354 is shaped to
resist a torsional force that is applied to the implant device 340
and about the axis L1 when the device 340 is disposed within a bore
in the jaw bone. The non-circular outer periphery portion 354 has
at least three distinct face portions 356. In one form, the outer
periphery forms a polygonal portion 342 with vertices 344 at the
edges of sidewalls 346 (i.e., the face portions 356). The face
portions 356 may be made partially or entirely of the porous
material or porous tantalum metal that extends along at least one
of the face portions 356. With this configuration, the vertices 344
at the edges of face portions 356 penetrate the usually cylindrical
or circular sides of a bore in the jaw bone formed by a dental
drill.
[0074] The implant device 340 may have a coronal end portion 348 on
the body 350 that is configured to receive the driving tool 300
that allows press-fit installation of at least a portion of the
body 350 into a bore into the jaw bone. The body 350 can be
press-fit into a bore in the bone by using the drive tool 300 or by
exerting other types of pressure on the coronal end portion 348 of
the dental implant 340 until an interference fit is created between
the body 350 and the bone. So configured, the non-circular outer
periphery 354 can give the implant device 340 additional stability
to resist a rotational or torsional force that is applied to the
implant device 340 around the coronal-apical axis L1 while the
implant device 340 is disposed within a bore in the jaw bone.
[0075] While the non-circular portion 354 may be sized and shaped
to resist rotation, it should also have a shape that does not
create an unmanageable resistance to translating the implant device
340 for vertically inserting the implant 340 into the bore in the
bone. Thus, it will also be understood that while the non-circular
portion 354 may axially extend the entire length of the implant
340, or any other length that is advantageous for resisting
rotation, the longer the non-circular shape along the implant 340,
the more difficult it may be to insert the implant 340 into a
circular bore.
[0076] In another aspect, as shown in FIGS. 9 and 10, the implant
device 320 has a non-circular outer periphery 358 forming a
polygonal portion 318 that is stopped short of the full axial
length of the implant device 320 to provide space for a plurality
of (but at least one) radially extending annular teeth 326. The
teeth 326 taper outwardly from the coronal-apical axis as the teeth
extend coronally. The annular teeth 326 can be configured to
securely contact a bone in a bore and to fasten the implant device
320 within the bore. A porous portion 360 may also be disposed
partially or entirely on the body portion 358 or the non-circular
outer periphery, including the annular teeth 326, in order to
increase the friction between the implant device 320 and the bone
and provide a more secure interference fit. In this configuration,
the annular teeth 326 are placed into contact with the sidewalls of
the bore as the implant device is press-fit into the bore to
provide greater stability and increased resistance to the pull-out
of the implant device 320 from a bore in the bone.
[0077] Referring to FIGS. 13-14, while the cross-section of the
outer periphery in the form of the polygonal portion 318 or 342 is
shown to be a regular polygon, alternatively, implant device 500
has an outer periphery 502 that is an irregular polygon or other
multi-sided shape with distinct face portions 504 that is
asymmetrical about an axis T traverse to the coronal-apical axis
L2. In the illustrated form, an irregular hexagon is shown with
three small face portions 506 and three wide face portions 508.
Otherwise, the structure is that of the implant device 340. It will
be understood that many other multi-sided shapes are
contemplated.
[0078] Referring to FIGS. 15-19, rather than distinct face portions
that form flat sides, implant devices 400 and 600 respectively have
bodies 402 and 602 with non-circular outer peripheries 408 and 604
that have a closed, curved shape extending around a coronal-apical
axis L3 and L4, respectively. For example, outer periphery 604 of
implant device 600 is generally oval for fitting tightly into a
circular bore in a jaw bone to resist a torsional force applied to
the implant device 600 and about axis L4. Tapered implant device
400 is similarly oval (FIGS. 18-19). It will be understood that the
non-circular periphery may be any other convexly curved shape such
as elliptical or obround. Alternatively, the outer peripheries may
have a closed, curved shape that is concavely curved such that a
portion on the non-circular outer periphery is shaped to extend
inwardly toward the center of the implant device. In another
alternative configuration, the non-circular outer periphery may
have a number of curves to form a bumped, scalloped, and/or
serrated shape. It should also be understood that the non-circular
outer periphery could contain a variety of other cross sectional
shapes including peripheries that are a combination of flat sides
or face portions and curved sections.
[0079] Whether or not the non-circular, outer periphery is curved
or has distinct sides, the mechanical fixation of the implant
device within a bore by interference fit is strengthened by forming
the porous material at the outer periphery because the porous
material has such a relatively high co-efficient of friction with
bone.
[0080] To further strengthen the interference fit, the outer
periphery may be provided with a maximum width slightly greater
than the diameter of the bore in the jaw bone that receives the
implant device. So configured, as the implant device is inserted
into the bore in a jaw bone, the larger outer periphery roughened
by the porous material will bite into the bone by grating, chipping
and/or flaking bone pieces off of the sidewalls of the bore in
which the implant device is being placed. This "rasping" action
forms slight recesses or indents within the bore sidewall in which
the implant device sits. This further restricts rotational or
twisting motion of the implant device within the bore since the
implant device does not have the clearance to rotate out of the
indents and within the bore.
[0081] The rasping action also accelerates osseointegration onto
the implant device and into the pores of the porous material due to
the bone compaction into the pores. First, the grating of the bone
structure causes the bone to bleed which stimulates bone growth by
instigating production of beneficial cells such as osteoblasts and
osteoclasts. Second, the bone pieces that fall into the pores on
the porous material assist with bone remodeling. In the process of
bone remodeling, osteoblast cells use the bone pieces as
scaffolding and create new bone material around the bone pieces.
Meanwhile osteoclast cells remove the bone pieces through
resorption by breaking down bone and releasing minerals, such as
calcium, from the bone pieces and back into the blood stream. The
osteoblast cells will continue to replace the grated bone pieces
from the pores and around the implant device with new and healthy
bone within and surrounding the extraction site. Thus, with the
porous material, the implant device has increased resistance to
twisting or rotation, allows for immediate or very early loading,
and increases long-term stability due to the improved
osseointegration.
[0082] Referring again to FIGS. 15-17, in one specific example, the
implant device 600 is disposed within a bore 606 in a jaw bone 608.
The non-circular outer periphery 604 may be dimensioned to
penetrate the usually cylindrical side 610 of the bore 606 formed
by a dental drill. Thus, the maximum width dimension W of the
implant device 600 is greater than the diameter D of the bore 606.
The difference between W and D (or 2.times. the interference length
`x`--or 2x as shown on FIG. 17) should not be too small or too
large. If the difference is too large (i.e., the maximum implant
device width W is much longer than the bore diameter D), the
practitioner will not be able to press fit implant device 600 into
bore 606 without using a force that could damage the jaw bone or
dental implant device 600. If the difference between W and D is too
small, the implant device 600 will lack sufficient initial
stability and will not grate or scrape a sufficient amount of bone
tissue from the bore sidewall 610 to stimulate significant bone
growth. In one form, the difference between W and D (or in other
words, 2.times.) should be about 0.008 to 0.18 mm when W is 3.7 mm
to 6.0 mm. This corresponds to an interference volume of about 5-20
mm.sup.3 where 2.times. forms the total width of the interference
volume as shown on FIG. 17, and the volume extends generally the
height of the implant device 600 as shown in dash line on FIG. 16.
These dimensions apply to implants having typical axial lengths of
about 8 mm to about 16 mm.
[0083] It will be understood that implant device 600, as well as
any of the other implant devices with anti-rotational features, may
have transgingival extensions 612 (shown in dash-line on FIG. 15)
including one-piece implants with integral abutments or
single-stage surgery implants with an integral emergence profile
that attaches to a separate abutment.
[0084] It will also be understood that many of the features shown
on implants 320, 340, 400, 500, and 600 may be provided for any of
the implant devices described herein.
[0085] Referring to FIGS. 20-23, another way to restrict rotational
movement of an implant device embedded in the jaw bone is to
provide the implant device with multiple roots which makes the
implant asymmetric at least along the roots. When such a multi-root
implant device is placed in a bore in the jaw bone that is shaped
to correspond to the shape of the implant device, the roots are
each placed in a bore branching off of a main bore. In this case,
the dental implant does not have the clearance within the bores to
rotate about its coronal-apical axis when a torsional force is
applied to the implant device and about its axis.
[0086] A multi-root implant may also simplify the surgery when the
implant has the same number of roots and general configuration as
the natural tooth it is replacing. For instance, the implant may
have two or three roots to correspond to the configuration of a
molar or pre-molar with the same number of roots. In this case, the
bore receiving the multiple-root implant may require minimal
drilling to shape the bore when the bore is at the extraction site
of the molar or pre-molar being replaced by the implant. This
allows the implant device to be immediately placed into the
extraction site, preserves more of the natural gum tissue for the
patient, and presents a more aesthetic result.
[0087] Referring to FIGS. 20-21, in one specific example, a
multiple-root implant device 700 has a body 702 that generally
defines a coronal-apical axis L5 and a porous portion 704, such as
the porous tantalum portion described above, disposed at the body
702. The body 702 has a main portion 706 and roots 708 and 710
extending outwardly from the main portion 706 and to free, distal
ends 712 and 714, respectively. The porous portion 704 may form
substantially the whole body 702, at least part of one or more
roots 708, and 710, and/or at least part of the main portion
706.
[0088] The main portion 706 includes an intermediate portion 716
relative to the full coronal-apical length of the implant device
700. The roots 708 and 710 extend or branch out from the
intermediate portion 716. The roots 708 and 710 extend in a general
apical direction, and in one form generally parallel to the
coronal-apical axis L5 of the implant device 700. Implant device
700 is shown with two roots to generally correspond to a natural
tooth with two roots such as the mandibular molars or maxillary
premolars. It will be understood, therefore, that the roots 708 and
710 could be modified to extend more laterally to match the exact
configuration of a particular natural tooth, and in turn, the
extraction site to receive the implant device 700. Thus, it will be
understood that any of the multiple-root implant devices described
herein can be configured such that the multiple roots are arranged
and extend in a general direction that corresponds to the
arrangement of the roots on the natural tooth that the dental
implant replaces.
[0089] In one form, at least one of the plurality of distinct roots
708 and 710 can be integrally formed with the main portion 706 but
may otherwise be separately formed and connected to the main
portion 706.
[0090] To insert the multi-root implant device 700 into a bore at
an extraction site, the roots should be aligned with the separate
branch bores. Pressure is then applied to a coronal tip portion 718
of the implant device 700 and in an insertion direction as
explained above for other press-fit implant devices. As the
pressure is applied, the plurality of distinct roots 708 and 710
may engage the bone and fasten the implant device 700 into the
bore(s) and create an interference fit as well as a mechanical
fixation between the implant device 700 and the bone that restricts
substantial rotation of the implant device 700 about its
coronal-apical axis L5.
[0091] As mentioned above, the implant device 700 can have a porous
portion disposed on at least one of the plurality of roots 708 and
710 to strengthen the interference fit with the bore. In one
alternative, the roots 708 and 710 can be configured to taper
inwardly as the roots extend outwardly from the main portion 706.
Specifically, the root or roots have a coronal end portion 720
adjacent to the main portion 706 and an apical end portion 722. In
this alternative, the coronal end portion 720 has a width dimension
w1 greater than the width dimension w2 of the apical end portion
722. Thus, as the implant device 700 is inserted into a bore in the
bone, the root will expand the branch bore in which it is inserted,
forming a very strong interference fit.
[0092] In addition, or in the alternative, at least one of the
plurality of distinct roots 708 and/or 710 can have a
cross-sectional dimension greater than a corresponding
cross-sectional dimension of a branch bore in bone for receiving
the root 708 and/or 710 similar to the oversizing provided on the
implant devices 320, 340, 400, 500, and 600 described above. So
dimensioned, as the implant device 700 is moved in an insertion
direction, the porous portion 704 grates pieces of bone off of a
sidewall of the branch bore as described above to stimulate bone
remodeling and increase initial stability. This dimensioning also
can be applied to the main portion 706 as well.
[0093] Referring to FIG. 21, the main portion 706 of the
multiple-root dental implant device 700 also can include a
non-circular outer periphery 724 to restrict rotation of the
implant device 700 within a bore as previously described above for
the other forms of the implant device. In this case, the
non-circular outer periphery 724 extends about the coronal-apical
axis and may have a plurality of convexly curved portions 726 where
each curved portion 726 coronally aligns with a different one of
the plurality of roots 708 or 710. This forms an elongated indent
or groove 728 at the intersection of adjacent curved portions 726
and provides the non-circular out periphery with an asymmetric
cross-section to resist rotation (where asymmetric means asymmetric
about an axis transverse to the apical-coronal axis L5). It will be
understood that the roots 708 and 710 could also have any of the
non-circular outer peripheries described above.
[0094] Referring briefly to FIG. 22, a three root dental implant
device 800 has three distinct roots 802, 804, and 806 but is
otherwise the same or similar to implant device 700. Implant device
800 is particularly useful for replacing natural maxillary first,
second, or third molars with three roots or a single or double root
tooth that may have grown an extra supernumerary root.
[0095] Referring to FIG. 23, a dental implant device 900 can have
three or more roots. In this case, a four root implant device 900
is shown. The structure of the implant device 900 is similar or the
same as to that described above for the other multi-root implant
devices except that here implant device 900 has roots 902, 904,
906, and 908. A dental device 900 may provide more than the normal
number of roots to correspond to natural teeth with supernumerary
roots. Oftentimes, this condition occurs in mandibular canines,
premolars, and maxillary molars, and especially third molars. Thus,
the multi-root dental implant devices may match the number of roots
no matter what that number or configuration is on the natural
tooth, and in turn, at the extraction site. It also will be
appreciated that more than the usual number of roots may be used
when such structure is deemed beneficial for anchoring the tooth in
the jaw bone regardless of the number of roots on the natural tooth
to be replaced, if the tooth even existed. This may be used when
more surface area on the implant device is desired.
[0096] While the implant devices 320, 340, 400, 500, 600, 700, 800,
and 900 may be substantially made of the porous material, it will
be understood that the implant devices may alternatively have a
titanium core with a porous sleeve placed around the core. The
porous material may be assembled or bonded to the core by diffusion
bonding or direct chemical vapor deposition processes. The porous
material and core may also be press-fit together. The stress
required to disassemble the bonded or press-fit core to porous
material interface, if present, should exceed 20 MPa. The
non-porous parts of the dental implants may be machined, EDM cut,
or made by using net-shape (custom) manufacturing processes.
[0097] While the illustrated forms are shown to be dental implants,
it will be understood that such structures, with porous metal or
porous tantalum portions on an implant with a non-circular
periphery or multi-root implant to restrict rotation in a bore, may
be applied to implants used on other areas of a human body or
animal, whether or not such an implant is to be inserted into
bone.
[0098] Those skilled in the art will recognize that a wide variety
of modifications, alterations, and combinations can be made with
respect to the above described embodiments without departing from
the spirit and scope of the invention, and that such modifications,
alterations, and combinations are to be viewed as being within the
ambit of the inventive concept.
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