Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
i) Field of the Invention
The invention relates to medicine, namely to stomatology and more
especially concerns a dental implant for supporting a dental prosthesis.
ii) Brief Description of Prior Art
The variety of the dental implants used nowadays for the solution of
various problems of oral reconstruction, which employ the remarkable
advancements in modern technology and material engineering, has become so
diverse that they can be categorized by their shape, material, localization,
the
technique of the manufacture, etc. as shown in Manual of Orthopedic
Stomatology, ed. by V. N. Kopeikin, Moscow: Medicine, 1993, p.419.
A first known device includes a cylindrical dental implant as described
in Endosseous Dental Prosthesis, The USSR Copyright No. 1557709,
consisting of an endosseous part, a neck and a supporting head to which a
tooth
prosthesis is fastened later. The core of the implant is made of solid TiNi
alloy
and rings made of porous and dense TiNi alloy are supported or strung on the
core. Wire elements arranged in tiers are built into some rings for the
reinforcement of the periodontal bonds. A device of this type is illustrated
in
Fig. 1.
This known device is of complicated structure; it has poor integration
with the periodontium, specially in the dense pericervical area, is highly
subjected to the penetration of infection into the bone socket of the implant,
with such subsequent response of the organism as the proliferation and the
migration of the epithelium, the formation of micro-abscesses and the
development of granulation.
A second known implant also includes a cylindrical dental implant
containing an endosseous part, a neck and a supporting head as described in
The Application of Shape Memory Alloys in Stomatology, M. Z. Mirgazimov,
V. K. Polenichkin, V. E. Gunter, V. I. Itin, Moscow: Medicine, 1991, p. 192.
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The endosseous part possesses a supporting core made of dense TiNi alloy
with porous coating and a supporting head on which a tooth is fastened. This
device is simpler in its structure and technology compared to the known device
described above and illustrated in Fig. 1.
The disadvantage of this second implant is its poor osseointegration due
to the low mass of the porous material present as a coating on a solid core,
and
the failure of the prosthesis caused by the poor integration of the implant
into
the periodontium in its cervical part.
A third implant is the dental implant described in Russian Patent
2,098,043, which consists of an endosseous part, and a neck with a fastened
supporting head. The endosseous part contains a supporting core made of
dense TiNi alloy having a porous coating on the base and the neck. Unlike
the second known device described above, the porous coating and the elaborate
shape of the neck of this third device contribute to the success of the
prosthesis
due to the improvement of the osseointegration at the cervical part and the
reduction of the bone tissue resorption. The disadvantage of this third
implant
is its poor osseointegration due to the low mass of the porous material
forming
a coating on the endosseous part.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention there is provided a dental
implant comprising a unitary member comprising an endosseous body and a
supporting head, said unitary member being of permeable porous TiNi alloy,
said supporting head being adapted to support a dental prosthesis.
In another aspect of the invention there is provided use of a dental
implant of the invention to support a dental prosthesis in a patient having
need
of such dental prosthesis.
In still another aspect of the invention there is provided a method of
fitting a dental prosthesis in a dental site in the oral cavity of a patient
comprising inserting in a bone socket at the dental site, an implant of the
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invention with the endosseous body innermost and the head outermost in said
bone socket, and mounting a dental prosthesis on said head such that the
prosthesis extends outwardly of the dental site.
In a further aspect of the invention there is provided in combination an
implant of the invention, and a dental prosthesis supported on and affixed to
said head.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In a preferred embodiment of the invention there is provided a dental
implant comprising a unitary member consisting of an endosseous part, a neck
and a supporting head, the unitary member being of permeable porous TiNi
alloy and reinforced along its length with at least one wire, preferably a
single
wire, made of dense TiNi alloy; preferably the implant is provided with a
coating, for example, a polymer or ceramic coating, on the neck and the
supporting head to prevent the infiltration of body fluids and micro-
organisms.
The permeable porous TiNi alloy of the unitary member suitably has a
porosity of 8 to 80%, and more especially comprises a porous body, in which
the porosity extends throughout the body. In particular, the body may be
formed with a controllable and variable porosity.
Preferably the porosity is at least 30% and preferably not more than
70%.
Preferably the permeability is derived from capillarity in the network of
passageways which define the porosity.
The capillarity is present in the article because of the inclusion therein of
a large number of pores of interconnected fine size.
Capillarity is advantageous in that it promotes migration of a desired
fluid material into the network of passageways, and retention of the fluid
material in the network, without the need to apply external hydraulic forces.
In general the network provides permeability and this permeability is
isotropic.
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The capillarity and the isotropic character are, in particular, achieved
when the network defining the porosity comprises pores of different pore size,
the pore size distribution being as follows:
Pore Size in Microns uanti
10-2 - 10-' 1 - 5
10-1 - 10 S - 10%
- 100 10 - 20%
100 - 400 20 - 50%
400 - 1000 10 - 50%
above 1000 remainder to 100%
In an especially preferred iment the pore size distribution
embod is as
follows:
Pore Size in Microns uanti
10-2-10 5-15%
10 - 400 15 - 70%
400 - 1000 10 - 70%
above 1000 remainder to 100%
The porosity of a material affects its physio-mechanical qualities, for
example, mechanical durability, corrosion resistance, super-elasticity and
deformational cyclo-resistivity.
The porous nickel-titanium alloy (TiNi) suitably comprises 40 to 60%,
preferably 48 to 52%, by atomic weight, titanium, 40 to 60%, preferably 48 to
52%, by atomic weight, nickel, less than 2%, by atomic weight, molybdenum,
less than 2%, by atomic weight, iron and minor or trace amounts of other
elements, to a total of 100%. Desirably the alloy contains each of molybdenum
and iron in an amount of more than 0%, by atomic weight and less than 2%, by
atomic weight.
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The porous nickel titanium alloy implant of the invention displays
mechanical behavior very similar to that of live tissue and demonstrates high
biomechanical compatibility.
The porosity and permeability of the implant of the invention are
defined by a network of interconnected passageways extending throughout the
unitary member. The network exhibits a permeability for fluid material
effective to permit complete migration of the fluid material throughout the
network, and the implant is elastically deformable.
Most suitably the permeability arises from a capillarity effect in the
network and in particular a capillarity resulting from pores of different pore
sizes with a defined pore size distribution in accordance with the preferred
embodiments defined herein.
The network of pores renders the implant fully permeable to biological
tissue thereby facilitating the osseointegration of the implant in the bone
socket. After being implanted in the dental site, living tissue and bone cells
grow throughout the implant and even blood circulation systems develop
throughout the implant.
The implant of the invention may be used for substitution of missing
individual teeth and dentitions by endosseous implantation of the prosthesis
in
a prepared bone socket.
The combination of all these features produces a successful technical
outcome. The unitary structure of the implant facilitates its technology: that
is
simultaneous manufacture of all the implant structure, including the
reinforcing
wires by means of agglomeration. At the same time the cross-section of the
implant can have any desired shape as required by the specificity of the
concrete prosthesis; however, the circular shape is prompted by the technology
of the operation, so the implant is preferably cylindrical.
Depending on the concrete indications and characteristics of the edentia
the preferable transverse shape of the endosseous part is circular, this
facilitates
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the manufacture and the installation of the implant with totally cylindrical
shape, including its endosseous part, neck and the supporting head.
Longitudinal reinforcement along the entire length of the implant with at
least one wire made of dense TiNi alloy strengthens the implant and performs
the function of the solid core in the known devices. The wire, or wires,
unlike
the solid core of known devices, occupies less space, so there is more space
for
the porous material which promotes the osseointegration. At the same time, it
has been demonstrated that the mechanical durability of this preferred
construction is sufficient for the extended and full-value functioning of the
implant.
The unitary structure of the implant means that the supporting head is
present immediately after the implantation of the endosseous part, that is the
first stage of the operation. In contrast known implants need to be covered
with
the gingival tissue for four months after the first stage of the implantation
in
order to prevent the penetration of infection into the bone socket through its
pores. The present implant is preferably provided with a polymer coating of
its
supporting head and its neck, the area generally subjected to the penetration
of
the infection, to avoid such infection.
The invention is illustrated by reference to the accompanying drawings
in which:
Fig.l shows a prior art dental implant with the wire elements extending
from rings to form the periodontal bonds.
Fig.2 shows a prior art dental implant with a screw head.
Fig.3 shows a prior art dental implant with a porous coating on the neck.
Fig 4a shows a dental implant of the invention.
Fig. 4b shows the implant of Fig. 4a in a cross-section; and
Fig.S is an X-ray of installed dental implants.
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With particular reference to Figs. 4a and 4b, the dental implant 10 of the
invention has a unitary member 1 of porous NiTi reinforced by wire 2 along its
length.
Unitary member 1 has an endosseous body 12, a neck 14 and a head 16.
A polymer coating 3 extends over neck 14 and head 16.
With particular reference to Fig. 5, the implant of this invention is
shown at 21, implants of the third kind referred to above are shown at 22 and
implants of the invention with teeth installed are shown at 23.
EXAMPLE
The use of the implant of the present invention for the prosthesis of lost
teeth is illustrated by a concrete case of the clinical use of the implant in
the
Clinic of Dental Implantology of Medical Material Engineering Research
Institute.
Case description. Female patient R., 42 years old, diagnosed with 3d
class edentia of the maxilla and the mandible according to Kennedy. Two
years prior to the trial the patient had a two-stage implantation of dental
implants of cylindrical shape with removable supporting head and reinforcing
core (Fig.2 and Fig.S. position 22).
The control examination of the implants detected their mobility and the
presence of peri-implantation sulcus resulting from the low porous mass and
the deficit of the osseointegration, and also the drift of the supporting head
and
the reinforcing core developing during the mastication at the site of their
threaded connection.
The patient underwent implantation of the implant of the invention
(Fig.4 and Fig.S, position 21) with the following characteristics:
Material of member 1 - porous TiNi alloy;
The total length of implant ( 10) 17 mm;
Diameter of implant ( 10) 3.5 mm;
Material of the wire (2) - solid TiNi alloy;
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Diameter of the wire (2) 0.1 mm;
The length of the coated distal part -(neck 14 and head 16)
with polymer coating (3) 7 mm;
The thickness of the polymer coating (3) 0.2 mm.
The implantation was performed in the following way:
The bone socket was created under local trans-mucous anesthesia by
perforating a cylindrical hole with a diameter less than the implant's
diameter
by 0.1 mm. The implant sterilized in an autoclave was carefully hammered into
the bone socket. The gingival area adjoining the implant was dressed with
Solcoseryl for 6 postoperative hours in order to protect it from the intraoral
infection. A provisional plastic crown was fastened on the head of the implant
in order to provide the occlusal adaptation.
In 4 months the osteosynthesis in the endosseous part of the implant was
complete, and the dental prosthesis was fastened on the supporting head. The
roentgenogram (Fig.S - 23) made in 4 months postoperatively demonstrates no
peri-implantation sulcus, and is evidence of successful osseointegration and
the
guarantee of extended and effective functioning of the dental implant.
