U.S. patent application number 14/631565 was filed with the patent office on 2015-08-20 for medical implant and method of implantation.
The applicant listed for this patent is Nobel Biocare Services AG. Invention is credited to Lars Jorneus, Paulo Malo Carvalho, Henrik Petersson.
Application Number | 20150230890 14/631565 |
Document ID | / |
Family ID | 40514095 |
Filed Date | 2015-08-20 |
United States Patent
Application |
20150230890 |
Kind Code |
A1 |
Malo Carvalho; Paulo ; et
al. |
August 20, 2015 |
MEDICAL IMPLANT AND METHOD OF IMPLANTATION
Abstract
A medical implant and a method of implanting a medical implant
are disclosed. The medical implant (20) is elongate and for
fixation in a patient, and comprises an apical bone anchoring
portion (200) for bone apposition, and an unthreaded coronal
portion (210), wherein said coronal portion (210) has a length
(L.sub.2) exceeding or equaling a length (L.sub.1) of said apical
portion (200), and wherein said apical portion (200) has a maximum
outer diameter (D.sub.1) that is equal to or larger than a maximum
outer diameter (D.sub.2) of said coronal portion. In a method of
implanting a medical implant, an apical part is affixed in the
zygomatic bone, and a coronal part is positioned outside the
maxilla in the mucous membrane.
Inventors: |
Malo Carvalho; Paulo;
(Liboa, PT) ; Jorneus; Lars; (Frillesas, SE)
; Petersson; Henrik; (Goteborg, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nobel Biocare Services AG |
Zurich-Flughafen |
|
CH |
|
|
Family ID: |
40514095 |
Appl. No.: |
14/631565 |
Filed: |
February 25, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13003260 |
Mar 31, 2011 |
|
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PCT/EP2008/005585 |
Jul 9, 2008 |
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14631565 |
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Current U.S.
Class: |
433/174 ;
433/173 |
Current CPC
Class: |
A61C 8/0022 20130101;
A61C 8/0034 20130101; A61C 8/0018 20130101 |
International
Class: |
A61C 8/00 20060101
A61C008/00 |
Claims
1. An elongate zygoma implant for fixation in a patient, said
implant comprising an apical bone anchoring portion configured for
apposition to a zygomatic bone of said patient, and a non-threaded
coronal portion, wherein said coronal portion has a length
(L.sub.2) exceeding or equaling a length (L1) of said apical
portion, wherein said apical portion has a maximum outer diameter
(D1) that is equal to or larger than a maximum outer diameter (D2)
of said coronal portion, and wherein the total length of the apical
bone anchoring portion and the non-threaded coronal portion is in a
range of 30 mm to 55 mm.
2. The implant according to claim 1, wherein a ratio of a length of
said apical portion (L1) to said length of said coronal portion
(L2) is in a range of 0.2 to 0.5.
3. The implant according to claim 2, wherein a ratio
(D.sub.1/D.sub.2) of a said maximum outer diameter (D.sub.1) to
said maximum outer diameter (D.sub.2) of said coronal portion is in
a range of 0.5 to 0.95.
4. The implant according to claim 3, wherein said maximum outer
diameter (D.sub.2) of said coronal portion is smaller than a
diameter of valleys of threads at said apical portion.
5. The implant according to claim 1, wherein said apical bone
anchoring portion comprises a tapered top portion, wherein said
tapered top portion is tapered towards an apical end of said
implant and an apical end diameter is less than half of said
maximum outer diameter of said apical portion (D.sub.1).
6. The implant according to claim 5, wherein said tapered top
portion is tapered with a tapering angle (.alpha.) in a range
between 25 to 75 degrees.
7. The implant according to claim 1, wherein said coronal portion
is rotationally asymmetrical.
8. The implant according to claim 1, wherein said coronal portion
is tapered towards a coronal end of said medical implant.
9. The implant according to claim 1, wherein a recess of a
connection interface at a coronal end of said implant is
substantially oriented in a longitudinal direction of said medical
implant.
10. The implant according to claim 1, wherein said medical implant
is made of a monolithic single piece.
11. The implant according to claim 1, wherein said apical bone
anchoring portion comprises a helical thread for said bone
anchoring.
12. (canceled)
13. The implant according to claim 1, wherein said coronal portion
is configured for gingiva apposition.
14. The implant according to claim 1 any of the preceding claims,
wherein said coronal portion is configured for partial radial
apposition to bone tissue and partial radial apposition to non-bone
tissue along a longitudinal portion of said medical implant.
15-28. (canceled)
Description
PRIORITY INFORMATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/003,260, filed Mar. 31, 2011, which is the
371 National Phase of PCT/EP2008/005585, filed Jul. 9, 2008, the
entirety of which is hereby incorporated by reference herein.
FIELD OF THE INVENTION
[0002] This invention pertains in general to the field of medical
implants and methods for implantation of such implants. In
particular, the invention relates to dental implants and methods
for their implantation.
BACKGROUND OF THE INVENTION
[0003] Various types of medical implants are known, e.g. as
anchoring elements that are intended to be implanted in patients'
jaws. Upon implantation these anchoring elements support e.g.
dental restorations via a connection interface.
[0004] Due to various reasons, such as diseases, bone quality may
be poor in certain bone regions of a patient. In edentulous or
partly edentulous patients jaw bone tissue may be highly resorbed.
Therefore it may be difficult or impossible to satisfactorily
anchor conventional medical implants in such damaged or resorbed
bone tissue regions. For instance in the maxilla, i.e. the upper
jaw, special elongate anchoring elements may be used that are
anchored both in the maxilla and in the os zygomaticus, i.e. the
zygomatic bone. Conventionally, the anchoring element is affixable
by a double anchoring technique in the maxilla and the zygomatic
bone. Between the maxilla and the zygomatic bone the anchoring
elements extend through a cavity in the skull, the maxillary sinus
cavity.
[0005] In U.S. Pat. No. 5,362,236 and U.S. Pat. No. 5,564,926 such
an elongate anchoring element and a method of implanting the
anchoring element are disclosed. The anchoring element has two
generally cylindrical portions with different diameters. A threaded
apical end portion of the anchoring element has the smaller
diameter thereof, and is intended to be positioned in the zygomatic
bone. A threaded coronal portion of the anchoring element has the
larger diameter thereof, and is intended to be positioned in the
maxilla. The anchoring element is implanted by drilling two aligned
bores in the bone tissue. The apical, smaller diameter, portion of
the anchoring element is passed through the larger diameter bore in
the maxilla and is threaded into the smaller diameter bore in the
zygomatic bone. While self-threading by the apical, smaller
diameter, portion takes place in the second bore, the larger
diameter portion is self-threaded in the first, larger diameter,
bore in the maxilla. Thus, the anchoring element may be reliably
double anchored when applied.
[0006] However, both anchoring elements and methods, such as
disclosed in U.S. Pat. No. 5,362,236 and U.S. Pat. No. 5,564,926
may be further improved or provided with alternatives. An
alternative anchoring element is disclosed in WO2005/079697. The
anchoring element comprises a first fixation portion, disposed at
the apex, a second fixation portion, disposed at the basis of the
anchoring element, and an intermediate portion in between the first
and second fixation portion.
[0007] For instance, working inside and from inside the maxillary
sinus may be difficult due to limited visibility, space etc. Access
hole in the maxillary bone is sometimes opened towards the
maxillary sinus cavity, in order to gain a field of sight into the
maxillary sinus cavity. However, this may be both cumbersome and
imply healing complications for the patient.
[0008] Thus, there is a need for an improved medical implant and/or
medical method for implanting a medical implant. Hence, an improved
medical implant and/or medical method for implanting a medical
implant would be advantageous. In particular a medical implant
and/or medical method for implanting a medical implant allowing
reliable anchoring in bone tissue; increased surgical flexibility;
improved surgical control, e.g. by improved visible feedback of the
medical procedure; and/or cost-effectiveness, e.g. by reduced
surgery time, patient recovery time, potential side effects; etc.
would be advantageous.
SUMMARY OF THE INVENTION
[0009] Accordingly, embodiments of the present invention preferably
seek to mitigate, alleviate or eliminate one or more deficiencies,
disadvantages or issues in the art, such as the above-identified,
singly or in any combination by providing a medical implant and a
method of implanting a medical implant according to the appended
patent claims.
[0010] According to one aspect of the invention, a medical implant
is provided. The medical implant is an elongate medical implant for
fixation in a patient. The implant comprises an apical bone
anchoring portion for bone apposition, and a non-threaded coronal
portion, wherein the coronal portion has a length exceeding a
length of the apical portion, and wherein the apical portion has a
maximum outer diameter that is equal to or larger than a maximum
outer diameter of the coronal portion.
[0011] According to another aspect of the invention, a method of
implanting a medical implant in a patient in a medical procedure is
provided. The method comprises creating a first recess in a facial
surface of bone tissue of a maxilla of the patient; creating an
anchoring bore externally in facial skull bone tissue at a distance
from a location of the first recess in the facial surface of the
maxilla; and implanting a medical implant with an apical anchoring
portion thereof in the anchoring bore, and positioning a
non-threaded coronal part of the medical implant adjacent the first
recess.
[0012] The medical implant and the method enables a more beneficial
position and location of the implant interface against the bridge
or tooth/teeth replacement. This in turn provides for use of a less
voluminous replacement. Furthermore, the implant describes an
alternative path from the zygomatic bone, which does not occupy so
much space in the oral cavity. This is considered advantageous for
esthetic reasons and provides for more space for the tongue. The
beneficial position of the inventive implant, when attached to the
zygomatic bone in accordance with the method, in relation to the
dental restoration allows for a more aligned load transfer, which
may alleviate the surrounding body parts as well. Further
embodiments of the invention are defined in the dependent claims,
wherein features for the second and subsequent aspects of the
invention are as for the first aspect mutatis mutandis.
[0013] Some embodiments of the invention provide for a fixture of a
dental restoration that provides for improved anchoring.
[0014] Some embodiments of the invention also provide for an
improved medical implant that provides reliable anchoring in skull
bone tissue and a connection interface at an alveolar ridge of a
maxilla.
[0015] Some embodiments of the invention provide for a medical
implant that facilitates implantation thereof.
[0016] Some embodiments of the invention provide for a method of
implanting a medical implant, wherein visibility of the
implantation is improved.
[0017] Thus, some embodiments provide for improved precision and
safety of implantation.
[0018] Some embodiments provide for a medical procedure of
implanting a medical implant that is more securely and less
complicated to perform for a surgeon. Some embodiments provide for
increased surgical flexibility. Some embodiments provide for
improved surgical control, e.g. by improved visible feedback of the
medical procedure. Some embodiments provide for cost-effectiveness,
e.g. by reduced surgery time, patient recovery time, potential side
effects, etc.
[0019] It should be emphasized that the term "comprises/comprising"
when used in this specification is taken to specify the presence of
stated features, integers, steps or components but does not
preclude the presence or addition of one or more other features,
integers, steps, components or groups thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] These and other aspects, features and advantages of which
embodiments of the invention are capable of will be apparent and
elucidated from the following description of embodiments of the
present invention, reference being made to the accompanying
drawings, in which
[0021] FIGS. 1A and 1B are perspective views of prior art medical
implants;
[0022] FIGS. 2A, 2B, and 2C are a perspective view and a lateral
view of an embodiment of a medical implant and a coronal end
portion thereof in cross section;
[0023] FIGS. 3A, 3B, and 3C are similar FIGS. 2A-2C illustrating
another embodiment of a medical implant;
[0024] FIGS. 4A, 4B, and 4C are views illustrating a conventional
medical implantation procedure via the sinus cavity;
[0025] FIGS. 5A and 5B are a frontal view and a lateral view
illustrating implanting of a medical implant; and
[0026] FIG. 6 is a flow chart illustrating a medical procedure of
an embodiment.
DESCRIPTION OF EMBODIMENTS
[0027] Specific embodiments of the invention will now be described
with reference to the accompanying drawings. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. The terminology used in the
detailed description of the embodiments illustrated in the
accompanying drawings is not intended to be limiting of the
invention. In the drawings, like numbers refer to like
elements.
[0028] The following description focuses on an embodiment of the
present invention applicable to a dental implant for anchoring in
skull bone, such as the zygomatic bone. Such anchoring dental
implants are also referred to as fixtures. However, it will be
appreciated that the invention is not limited to this
application.
[0029] The medical implants 100, 101 shown in FIG. 1A and FIG. 1B
comprise two longitudinally adjoining cylinder-shaped segments.
FIG. 1A corresponds to FIG. 1 of U.S. Pat. No. 5,362,236 and U.S.
Pat. No. 5,564,926 of the same proprietor as the applicant of the
present application, which hereby are incorporated in their
entirety for all purposes. The implant is essentially composed of
two cylindrical segments bordering each other and being in
alignment, wherein the first, coronal segment 1 has a diameter
larger than that of the second, apical segment 2.
[0030] The outside of the implant is threaded, except for a
mounting portion extending from the coronal end of the implant and
connected to the cylindrical coronal segment 1. The outer threads
comprise first threads 4 on the coronal cylindrical segment 1 and
second threads 5 on the apical cylindrical segment 2. The pitch is
the same for both threads 4, 5 merging at the border zone between
the cylindrical segments. The inner diameter of first threads 4 is
larger than the outer diameter of the second threads 5. Threads 4,
5 are self-tapping.
[0031] A symmetrically centered bore 17 extends from the apical end
6 and has an extension corresponding to about half the length of
the apical segment 2. Two through slits 7, 8 arranged symmetrically
in segment 2 and in its longitudinal direction extend from a plane
perpendicular to the central axis near the apical end 6. Slits 7, 8
establish communication between the outside of apical segment 2 and
the symmetrically centered bore 17 arranged therein for transport
of bone material removed by ablation. The outside of apical segment
2 is beveled (beveling 16) towards apical end 6.
[0032] The mounting section 3 is contained within a cylindrical
chamber with a diameter corresponding to the outer diameter of
coronal cylindrical segment 1. The mounting segment 3 comprises a
base portion 9 having the form of a cylindrical body dissected by a
plane at an angle of 45 DEG in respect of the cylinder axis. The
circular basis of base portion 9 is connected to the coronal end of
the coronal cylindrical segment 1 with which it merges. Nearest to
the coronal cylindrical segment 1 base portion 9 has an annular
flange 14 to which an annular groove 15 connects in direction of
the coronal end. End face 10 of base portion 9 is defined by a
dissecting plane and, at its coronal zone, smoothly rounded joins
the cylinder mantle of base section 9, the beading decreasing
gradually towards the apical portion of the base section. Because
of the beveling the profile of end face 10 is substantially
circular. In its center end face 10 has a bore 12 running at an
angle of 45 degrees in respect of longitudinal axis A of the
implant 100. At bore 12 base section 9 is extended under formation
of a frustum of a cone 11 tapering in direction away from base
section 9. Mantle surface 13 of the cone frustum 11 and the annular
end face 10 are designed for sealing abutment of a dental
prosthesis or bridge (not shown) that can be mounted on the base
portion by screw means.
[0033] The implant 101 shown in FIG. 1B differs from the implant
100 of FIG. 1A in that the connection interface comprises a
hexagonal unit 111 instead of the frusto conical part 11.
[0034] FIGS. 2A and 2B illustrate embodiments of an elongate
medical implant 20. The elongate medical implant 20 is devised for
fixation in bone tissue in a patient.
[0035] The implant 20 comprises a helically threaded apical bone
anchoring portion 200 for bone apposition. A tapered top portion
201 is provided at the apical portion 200. The top portion is
tapered towards an apical end of the implant 20. The tapered top
portion 201 of the implant 20 is tapered with a tapering angle in
the range between 25 to 75 degrees. Thanks to the tapered top
portion, entry into a bore is readily found upon implantation. The
implant 20 is homing and self-centering in the bore. This is
particularly advantageous, when the bore is partly hidden or
obscured. Thus, the tapered top portion 201 facilitates insertion
of the apical end of implant 20 into a bore.
[0036] The apical portion 200 may be cylindrical except for the
tapered top portion 201. The apical portion 200 may also be
slightly tapering towards the top portion 201 for improved primary
stability of the implant upon implantation.
[0037] A diameter of the apical end by the tapered top portion 201
is less than half of the maximum outer diameter of the apical
portion (D1).
[0038] Alternatively, the apical portion 200 may be conical or at
least partly conical, tapering towards the tapered portion 201.
Tapered portion 201 may in some embodiments comprise a bevel at the
apical end.
[0039] The thread of the helically threaded apical bone anchoring
portion 201 is, upon implantation in bone tissue, used to convert
between rotational and linear movement. That means by rotating the
implant 20 the implant 20 is screwed into the bore in longitudinal
direction thereof. The peak and valley structure of the thread
provides a primary stability of the implant 20 in the bone
tissue.
[0040] In other embodiments the implant may alternatively, or in
addition, comprise other bone anchoring structures than a helical
thread. The apical portion may be provided with other bone
engagement interfaces. The apical portion may for instance be
devised to provide fixation by frictional engagement in the bore.
Fixation of the apical portion to bone tissue may also be provided
by structures providing pressure towards the appositioned bone
tissue, similar like a plug or peg. Such structures may be annular
ribs. A trade off between implantation time and primary stability,
as well as long-term osseointegration of the implant may be
made.
[0041] The implant 20 further comprises an unthreaded coronal
portion 210. Unthreaded means that no thread is present along the
coronal portion 210. An alternative term to unthreaded in this
context is non-threaded, i.e. there is no peak and valley structure
of a thread provided at the coronal portion 210. The coronal
portion 210 is substantially smooth on a macro level. The macro
roughness (explained below) of the coronal portion 210 is
substantially lower than that of the anchoring portion.
[0042] This provides for a portion of the implant 20 that is
arranged to not irritate or damage appositioned soft tissue, such
as gingiva, including embedded muscles, blood vessels, or nerves.
However, the surface of the non-threaded coronal portion may be
provided with a surface roughness on a micro level, as is
elucidated below.
[0043] In other embodiments the term unthreaded comprises that the
substantially smooth extension of the coronal portion 210 is free
of bone anchoring structures. The coronal portion 210 is free of
projections that may affect appositioned soft tissue.
[0044] Conventional anchoring elements, such as disclosed in U.S.
Pat. No. 5,362,236 and U.S. Pat. No. 5,564,926, may comprise
threaded portions that are appositioned to tissue when applied.
However, threaded portions of the anchoring element may irritate or
damage the tissue, e.g. in the maxillary sinus cavity. Also, tissue
from the maxillary sinus may be caught by the thread of the apical
part of the anchoring element, which might lead to impaired
osseointegration and secondary stability in the zygomatic bone and
eventually loosening of the anchored implant.
[0045] Embodiments of the invention provide for improved soft
tissue apposition. Thanks to the unthreaded portion 210, a normal
physiological function of the soft tissue is provided when
appositioned to the implant at that portion of the dental implant.
Conditions, such as soft tissue irritation or damage, catarrh or
irritation of the mucous membrane are effectively prevented. A
prophylactic treatment is comprised in this prevention.
[0046] The coronal portion 210 may have a surface with a coarse
micro roughness, wherein the coronal portion 210 is adapted to
provide a tissue friendly portion.
[0047] The outer surface of the implant 20, hereinafter also called
"surface" for the sake of simplicity, may have a topography with a
macro roughness, e.g. in the form of one or several threads at the
anchoring portion 200 in order to mechanically anchor the medical
implant in surrounding bone tissue. Topography is amongst others
defined as the study or detailed description of the surface
features of a region of an object, here of the medical implant. The
medical implant has an outer surface and the geometry thereof
follows a defined topography both on a macro scale and a micro
scale.
[0048] The macro roughness defines the outer geometry of the
medical implant. In FIGS. 2A and 3A, the macro roughness is
illustrated in the form of a threaded part of the medical implant
20 or 30. Additionally, the macro roughness of the threaded outer
surface 40 may in itself have a surface roughness, for instance
defined as a porosity of the surface, but this is referred to below
as micro roughness. The macro roughness of the surface lies for
instance for a medical implant in the mm range, wherein the macro
roughness may further be subdivided into finer structures, such as
grooves on threaded portions, or non-threaded portions in the sub
mm range.
[0049] Furthermore, the outer surface of the medical implant may
have a micro roughness in the .mu.m range. The micro roughness
defines the topography of the surface of embodiments of medical
implants in the present context. In contrast, the above-described
macro roughness is defined by the outer contour of the medical
implant.
[0050] For instance, in case the implant 20 is a ceramic implant,
the outer surface topography may be machined and densely sintered
without a processed outer surface thereof, i.e. after sintering the
ceramic medical implant, has a very fine micro roughness. Coronal
portion 210 may advantageously have such a surface. However, such a
smooth outer surface has disadvantageous properties with regard to
osseointegration of the medical implant. Therefore, the anchoring
portion may be provided with a more coarse or rough outer surface
having an increased micro roughness compared to the untreated
sintered outer surface, which improves osseointegration thereof.
Such a coarse or rough outer surface may for instance be provided
in the form of a porous, rough surface layer, having an outer
surface roughness, for instance with a Ra value (explained below)
in the .mu.m range. For example, in WO 2005/027771, of the same
applicant as the present application, which is incorporated herein
by reference in its entirety, discloses a densely sintered ceramic
medical implant having a ceramic layer arranged thereon. The
ceramic layer, and thus an outer surface of the dental implant, is
provided with a surface that has a porosity, which is larger or has
more pores than in the underlying densely sintered ceramic
material. In this manner, a ceramic medical implant is provided
that fulfills the requirement of mechanical strength, and a
considerable improvement of osseointegration is achieved. At the
same time advantageous properties are achieved at the portion
having a fine micro roughness at the coronal portion 210.
Alternatively, the outer micro roughness of a ceramic medical
implant may be provided on a ceramic substrate thereof by modifying
the sintered outer surface, e.g. by chemical or mechanical abrasion
methods, as for instance disclosed in US-A1-2005/0106534.
[0051] The medical implant 20 may be manufactured of other
biocompatible materials, such as titanium oxide. In this case, the
implant may be provided with a desired surface roughness. For
instance the TiUnite.RTM. surface may be provided, as disclosed in
WO0174412 or WO03003936 of same applicant as the present
application, which are hereby incorporated in their entirety by
reference for all purposes. The TiUnite.RTM. surface has a
relatively high surface roughness and porosity.
[0052] Medical implants having such a suitable surface roughness
reach immediately upon implantation a primary stability in bone
tissue by the macro roughness, i.e. the macro structure of e.g.
threads of the implant. The medical implant then osseointegrates
with the surrounding bone tissue within a healing time of about 3
to 4 months, so that a secondary stability is provided, i.e. a
permanent bond between the threaded anchoring part 200 of the
medical implant screwed into the bone tissue and the bone tissue is
provided. However during a certain time following the implantation,
the total stability of the medical implant in the bone tissue
decreases to a certain stability that is lower than the initial
stability, i.e. the stability of the medical implant shows a
stability dip after implantation. Then bone growth accelerates and
osseointegration is achieved. Pores of the rough surface, into
which the bone tissue is growing firmly, provide the secondary
stability. In addition, also a mucous membrane may advantageously
be in apposition to a surface having a coarse micro roughness, but
a fine macro roughness.
[0053] A measure for surface roughness is parameters, such as Ra
value (mean roughness), Rt value (maximum roughness), Sa value etc.
The mean or average roughness (Ra) is defined as the average of
absolute distance values of a number of measurements across a
surface of interest. Sa is the equivalent amplitude parameter on a
3D or areal basis.
[0054] Roughness measurements may for instance be performed
according to procedures as determined in international standards.
However, measurements in accordance with such international ISO
standards may prove difficult to implement on dental implants, e.g.
due to the small surfaces thereof.
[0055] Attempts have been made to define and measure surface
roughness of prior art dental abutment and dental implants (see
e.g., Wennerberg, Ann et al., Design and Surface Characteristics of
13 Commercially Available Oral Implant Systems, JOMI, Vol. 8, No. 6
pages 622-633, (1993), which hereby is incorporated by reference in
its entirety). The Wennerberg article defines two surface roughness
parameters: (i) Rt, which is the maximum peak to valley height of
the profile of the surface (see page 623) and (ii) Ra, which is the
mean value of the peak to valley distance.
[0056] Using the Wennerberg definitions, smooth machined and/or
polished surface of implants have a Rt of approximately 10 microns
or less and a Ra of approximately 0.6 microns or less.
[0057] The coronal portion 210 has a length L.sub.2 exceeding a
length L.sub.1 of the apical portion 200. The apical portion 200
has a maximum outer diameter D.sub.1 that is larger than a maximum
outer diameter D.sub.2 of the coronal portion 210. In a specific
embodiment D.sub.1 is equal to D.sub.2.
[0058] The apical bone-anchoring portion 200 is devised for
apposition to a zygomatic bone of the patient, as will be
illustrated below.
[0059] The coronal portion 210 is at least partly devised for
apposition to soft tissue, including gingiva and muscle tissue, of
the cheek exterior of the maxilla. In an embodiment the coronal
portion 210 is cylindrical along its entire length.
[0060] The coronal portion 210 may be devised for partial
apposition to bone tissue and partial apposition to non-bone
tissue. For instance the radial portion of the coronal portion
oriented towards the maxilla upon implantation may be appositioned
to the maxilla. As the implant 20 will be positioned outside of the
maxilla, the outer radial part of the coronal portion 210 oriented
away from the maxilla, towards the soft tissue may be devised for
radial apposition to this soft tissue.
[0061] In embodiments the coronal portion 210 has a diameter
D.sub.2 that is smaller than an inner diameter of a thread of the
apical portion 200 at the maximum outer diameter thereof,
D.sub.1.
[0062] As D.sub.2 is smaller than D.sub.1, a plurality of implants
may be positioned with their coronal ends close to each other.
Thus, stability of a dental restoration may be improved in that a
plurality of implants fits in the narrow space at hand for
this.
[0063] In embodiments, the coronal portion may be rotationally
asymmetrical (not shown). This provides for improved anatomical
flexibility when positioning the implant.
[0064] In practical embodiments the dental implant, as shown in
FIGS. 2A-2C and 3A-3C may have the following approximate ranges
and/or values of length and diameter thereof:
[0065] Total length (L.sub.1+L.sub.2): 30 mm to 55 mm
[0066] L.sub.1 typically 15 mm
[0067] L.sub.2: 15 to 40 mm
[0068] Ratio (L.sub.1/(L.sub.1+L.sub.2)): approx 0.25 to 0.50
[0069] Ratio (L.sub.1/L.sub.2)): approx 0.35 to 1.0
[0070] D.sub.2: is typically smaller than the diameter of the
valleys of the threads or other grooves at the apical portion
200
[0071] Ratio (D.sub.1/D.sub.2)): 0.5 to 0.95
[0072] In embodiments, a ratio of the length of the apical portion
(L1) to the length of the coronal portion (L2) is in the range of
0.2 to 0.5.
[0073] The total length of the implant is the length of the apical
portion plus the length of the coronal portion thereof. Any except
further portions, e.g. protruding from the coronal portion are not
included in the total length. Further protruding portions may for
instance be mounting portions extending from a coronal end of the
implant.
[0074] Conventionally, anchoring elements, such as disclosed in
U.S. Pat. No. 5,362,236 and U.S. Pat. No. 5,564,926, have a bore
having internal threads formed about an axis that is tilted with
respect to a common axis for the cylindrical segments. External
threads on prosthesis threadably engage the internal threads to
secure such prosthesis to the anchoring element. However, due to
the tilting angle, the mounting process may be cumbersome.
[0075] Traditionally, the conventional zygoma implants have their
coronal end positioned at a distance from the alveolar ridge in a
palatal direction, i.e. towards the inside of the oral cavity, such
as shown in FIG. 4a, 4B or 4C. Thus, it may be difficult to provide
a dental restoration at an anatomically correct position, as a
distance from the coronal end of the zygoma implant to the position
of the original alveolar ridge of the maxilla has to be
bridged.
[0076] However, according to embodiments of the invention, these
issues are solved. A connection interface of a medical implant may
be provided close to or at the alveolar ridge of the maxilla.
[0077] In more detail, the implant 20 moreover comprises a
connection interface 220 for attachment of an abutment and/or a
dental restoration, such as a tooth prosthesis or a bridge.
[0078] The connection interface 220 may comprise an inner helical
thread at the coronal end of the implant 20 that is arranged
substantially in direction of the longitudinal direction of the
medical implant
[0079] Conventional implants, such as shown in FIGS. 1A and 1B have
a bore 12 running at an angle of e.g. 45 degrees in respect of
longitudinal axis of the implant 100. The bore 12 defines the
orientation of a connection interface for receiving an abutment
carrying a dental restoration. The orientation of the bore 12, due
to the angular orientation, is dependent on the rotational position
of the implant upon implantation. Therefore, care has to be taken
that the implant is screwed into a defined position towards an
ideal occlusion plane.
[0080] As shown in FIG. 2C, the threaded internal bore 221 of the
connection interface 220 of the embodiment is oriented
substantially in line with the longitudinal axis of implant 20.
Thus an abutment connection interface is arranged substantially
perpendicular to a longitudinal direction of the medical implant
20. Mounting of an abutment is thus advantageously facilitated,
irrespectively of the rotational orientation of the implant upon
implantation. The abutment may have a second connection interface
that is angled in relation to the longitudinal axis of the implant
20, e.g. for attachment of a bridge, tooth prosthesis or similar
dental restoration.
[0081] The implant 20 may be produced in a single monolithic piece.
The implant 20 may alternatively be split in at least two
interconnectable parts. For instance a connection interface may be
provided between the apical and the coronal portion.
[0082] An application of implants 20, 30 will now be described with
reference to a surgical method.
[0083] FIGS. 4A, 4B, and 4C are views illustrating a conventional
medical procedure for implantation of a medical implant by double
anchoring via the sinus cavity. Anchoring elements, such as
described above with reference to FIG. 1A and FIG. 1B, have two
portions with different diameters. The threaded apical end portion
2' of the anchoring element 1' has the smaller diameter thereof,
and is intended to be positioned interiorly in the zygomatic bone
Z. The threaded coronal portion 4' of the anchoring element 1' has
the larger diameter thereof, and is intended to be positioned in
the palatal region of the maxilla M. The anchoring element 1' is
implanted by drilling two aligned bores in the bone tissues. A
first bore, having a diameter suitable for anchoring the coronal
portion, is drilled through the maxilla M. Drilling is continued
through the maxillary sinus cavity 17 in the skull. Subsequently a
second bore 5', having an appropriate diameter for anchoring the
apical portion of the anchoring element, is drilled in the
zygomatic bone Z from inside the maxillary sinus 17. The apical,
smaller diameter, portion of the anchoring element is passed into
the bore in the maxilla M and is threaded into the bore in the
zygomatic bone Z. While self-threading by the apical, smaller
diameter, portion takes place in the second bore, the larger
diameter portion is self-threaded in the first bore in the maxilla.
Thus, the anchoring element is double anchored. In FIG. 4B a dental
bridge 410 is shown affixed to a plurality of implants 101 and 400,
401, 402, 403.
[0084] However, this conventional method has some drawbacks, as
described above. In contrast to this conventional method, an
improved method is provided. In an embodiment of the method, a
first recess is made in the exterior bone surface of the maxilla,
which is oriented towards the facial side of the maxilla, i.e.
outside of the oral cavity. Removing bone tissue from the maxilla
surgically creates the first recess. The first recess is made to
provide a passage for the coronal portion of an anchoring element
on the outside of the maxilla towards the alveolar crest thereof.
The first recess does usually not extend into the maxillary sinus
cavity and a remaining amount of bone tissue underlying the first
recess is kept. The first recess commonly has a longitudinal
extension oriented towards the exterior of a bone tissue at the
zygomatic bone located on the same side of the skull as the first
recess. Along its longitudinal extension, the first recess may be
provided as a guide channel for a tool when creating an anchoring
bore at the zygomatic bone. For instance a drill may be guided by
the first recess towards an entry site of the anchoring bore when
drilling a bore in the zygomatic bone. Thus, the longitudinal
extension of the first recess in the outer surface of the maxilla
is aligned with the longitudinal extension of the anchoring bore in
the zygomatic bone. Creating the anchoring bore, such as by a
drilling operation in accordance with the invention, may be made
under good visibility of the surgical working area. Subsequent
implantation of a medical implant in the anchoring bore is made.
The medical implant, when thus applied, extends from its apical end
in the anchoring bore to its coronal portion at the first recess
towards the alveolar crest of the maxilla.
[0085] Further embodiments of this method of implanting a medical
implant in a patient will now be described. A specific embodiment
will be elucidated further below with reference to FIGS. 5A, 5B and
FIG. 6. FIG. 5A is a frontal view illustrating a medical implant 20
implanted extra maxillary. FIG. 5B is a lateral view illustrating
the same situation. In addition, a conventional implant 101 is
indicated, purely for illustrative purposes, in order to illustrate
the difference between the present extra maxillary method and the
conventional maxillary sinus cavity crossing method. For
illustrative purposes the conventional implant is disclosed as
attached for interconnecting with a bridge or similar at
substantially the same location in the mouth as the inventive
implant. This illustration discloses that the apical portions in
such hypothetical case, end up at a very different locations.
Since, the bone quality of the anchoring bone is decisive for how
and where the implant can be affixed it would probably have been
more correct to illustrate the different resulting positions of the
coronal end portion of the respective implants instead. However,
this situation is not illustrated and needs to be imagined. It is
not considered difficult to understand, with hindsight, that there
is a risk for the implant of the conventional type and hence
applied by conventional methods to occupy more space by the palate
cavity than is needed by shifting to the herein claimed
technique.
[0086] In the present medical procedure, a medical implant is
implanted in a patient. The medical procedure comprises creating a
first recess in a facial surface of bone tissue of a maxilla of the
patient; creating an anchoring bore externally in facial skull bone
tissue at a distance from a location of the first recess in the
facial surface of the maxilla; and implanting a medical implant
with an apical anchoring portion thereof in the anchoring bore, and
positioning a non-threaded coronal part of the medical implant
adjacent the first recess.
[0087] The skull is normally made up of a number of skull bones.
For instance the adult human skull comprises twenty-two bones.
Except for the mandible, i.e. the lower jaw, all of the skull bones
are joined together by sutures, semi-rigid articulations formed by
bony ossification, whereby the presence of Sharpey's fibres permits
a little flexibility between the skull bones.
[0088] In embodiments of the method, the facial skull bone tissue
is comprised in the zygomatic process at the zygomatic bone. The
zygomatic process is a protrusion from the rest of the skull. Most
of it belongs to the zygomatic bone, but there are other bones
contributing to it too, namely the frontal bone, maxilla and
temporal bone.
[0089] When creating the anchoring bore, caution has to be made not
to injure any anatomical sensitive structures, like nerves or
vessels, e.g. passing through foramen in the maxilla or zygomatic
bone.
[0090] The method may comprise embedding the coronal part of the
medical implant under gingival tissue, once the anchoring in the
anchoring bore is made. The method may comprise embedding the
coronal part of the medical implant between the gingival tissue and
the first recess. A flap of gingival tissue may be put back to its
original position for this purpose and sutured for healing.
[0091] The method may comprise creating the first recess with a
longitudinal extension, and wherein the creating the anchoring bore
comprises creating the anchoring bore substantially in line with
the longitudinal extension of the first recess. In an embodiment
creating the anchoring bore is made by drilling a cylindrical bore
with a bore diameter, bore length, and bore longitudinal
orientation.
[0092] Preferably, the bore diameter is made in a dimension between
that of the diameter of the apical end portion and the diameter of
the apical (threaded portion) portion itself. The threads of the
tapered apical portion may initially be easily introduced into the
anchoring bore of the bone. The anchoring stability is then assured
in accordance with a preferred method due to the larger diameter of
the apical portion in relation to that of the bore when the implant
is further introduced. The helical threads starting from the
tapered portion thereof will assure during introduction of the
implant in the bore that the implant may be tapped further down the
hole. The tapering angle is defined in the drawings with the symbol
a and is between 25 and 70 degrees.
[0093] Creating the first recess may in an embodiment be creating
an indentation in the facial surface of the maxilla having a
longitudinal extension, a maximum depth, and a maximum width. The
maximum width is equal to or less than the bore diameter. The skull
bone is in an embodiment the maxilla at a facial side of the skull
of the patient at the indentation, and wherein the drilling a
cylindrical bore is drilling the cylindrical bore in the maxilla at
a zygomatic process, wherein the drilling the bore is made
substantially aligned with the longitudinal extension of the
indentation.
[0094] The anchoring may be made with an apical part of a medical
implant having a larger diameter than the coronal portion thereof.
Thus reliable anchoring is provided in a large anchoring bore. At
the same time, a narrower coronal portion provides for several
advantages. The first recess needs not be as large, i.e. the amount
of bone tissue removed is limited. This is both patient friendly,
and leaves sufficient remaining bone tissue of the maxilla such
that mechanical strength thereof is not threatened. In addition, as
the coronal portion takes less volume, potential irritation of
surrounding tissue is minimized. Moreover, it is facilitated to
implant a plurality of such medical implants in the narrow space
available. Mechanical stability of the dental implant and precision
of dental restorations attached thereto are maintained.
[0095] In an embodiment the skull bone is a zygomatic bone of a
facial side of the skull of the patient at the indentation, and
wherein the drilling a cylindrical bore is drilling the cylindrical
bore in the zygomatic bone, wherein the drilling the bore is made
substantially aligned with the longitudinal extension of the
indentation. The first recess may be used as a guide channel for a
drill when drilling the bore in the zygomatic bone, whereby the
first recess in the outer surface of the maxilla is aligned with
the bore in the zygomatic bone.
[0096] The method may further comprise using the first recess as a
guide channel for a tool creating the anchoring bore, whereby
aligning the anchoring bore with the first recess is provided. The
anchoring bore may be s created along a line of sight from the
first recess. Creating the anchoring bore may be made under full
visibility, thus preventing damage of sensitive anatomical
structures, such as nerves or blood vessels in the surgical working
area of the medical procedure.
[0097] The facial bone tissue of the maxilla may be located on the
external side of the maxilla adjacent to the alveolar ridge
thereof.
[0098] Implanting the medical implant with the apical anchoring
portion thereof may comprise bringing the apical anchoring portion
into bone apposition in the anchoring bore. The coronal end portion
of the medical implant may be brought into apposition to the bone
tissue at the first recess. Thus, the first recess when implanted
may support the medical implant.
[0099] As can be seen in the comparison shown in FIGS. 5A and 5B, a
lever arm may be minimized and bending moments on the medical
implant may be minimized, compared to conventional implants. The
minimization of bending moments is advantageous for long-term
stability of the implant-supported dental restoration. The aligned
implant according to the invention even allows for use of an
aligned abutment.
[0100] The method may comprise marking a position of a bone entry
site in the skull bone prior to creating the anchoring bore.
[0101] They may comprise positioning a non-threaded portion of the
medical implant under a mucous membrane, prophylactically treating
or preventing conditions such as catarrh or irritation of the
mucous membrane.
[0102] Remaining teeth of the maxilla of the patient may be
extracted prior to the creating the first recess.
[0103] The method may comprise incising a gingiva of the maxilla at
an alveolar crest of the maxilla.
[0104] The method may comprise creating gingiva flaps interior and
exterior of an alveolar crest of the maxilla; expanding the
exterior gingiva flap from the alveolar crest of the maxilla to a
zygomatic bone of the patient adjoining the maxilla.
[0105] The inner gingiva flap may be temporary sutured temporary
together in order to create a well visible surgical working
area.
[0106] A substantially planar bone surface may be created at the
alveolar crest of the maxilla by removing soft bone tissue for
creating a bone foundation. Thereby a good basis for affixing
dental restoration is provided.
[0107] Suturing the gingiva after the implanting concludes the
medical procedure.
[0108] The medical implant applied in the medical procedure may be
a medical implant according to embodiments described above.
[0109] In a specific embodiment, the method of implanting a medical
implant in a patient comprises the following steps, wherein some of
the steps may be made in another order or omitted in other
embodiments:
[0110] 610: extracting remaining teeth of a maxilla of the
patient;
[0111] 620: incising a gingiva of the maxilla;
[0112] 630: creating gingiva flaps interior and exterior of an
alvolear crest of the maxilla;
[0113] 640: expanding the exterior gingiva flap from the maxilla to
an os zygomaticus of the patient adjoining the maxilla;
[0114] 650: temporary suturing inner gingiva flap together to
create a line of sight;
[0115] 660: removing still existing tooth fragments from the
maxilla;
[0116] 670: creating a substantially planar bone surface at the
alveolar crest by removing soft bone tissue for creating a bone
foundation;
[0117] 680: marking a position of a drill hole entry in the os
zygomaticus;
[0118] 690: creating a recess in the maxilla external side that is
aligned with the position of the drill hole entry in the os
zygomaticus; the recess is created in the exterior bone surface of
the maxilla, which is oriented towards the facial side of the
maxilla; the recess is made to have a longitudinal extension
oriented towards the zygomatic bone;
[0119] 700: drilling a hole in the os zygomaticus from the position
of the drill hole entry in the os zygomaticus, aligned with the
recess; the recess may be used as a guide channel for a drill when
drilling a bore in the zygomatic bone, whereby the recess in the
outer surface of the maxilla is aligned with the bore in the
zygomatic bone; the drilling operation is performed under full
visibility, thus avoiding damage of sensitive anatomical structures
such as nerves or blood vessels in the surgical working area of the
medical procedure;
[0120] 710: implanting a medical implant with an apical part into
bone apposition in the drill hole, and positioning a coronal part
of the medical implant at the recess; the unthreaded portion of the
medical implant is positioned under the mucous membrane, thus
avoiding catarrh or irritation of the mucous membrane; the mucous
membrane may at least partly embed a rough surface of the
unthreaded portion of the medical implant; and
[0121] 720: the medical procedure is finalized by suturing the
gingiva together, leaving the coronal end of the medical implant
extending through the gingiva for fixation of abutments or dental
restorations.
[0122] The medical implant may for instance be of the type
described above with reference to FIGS. 2 and 3.
[0123] In a method of creating a dental restoration, the method of
implanting a medical implant in a patient as described above is
applied. Considering the position in space of the connection
interface of the implant at the coronal end thereof, a dental
restoration, such as a bridge is prepared. A plurality of medical
implants may be provided in the patient. Subsequently the dental
restoration is affixed to the connection interface of the at least
one medical implant, at a coronal side thereof positioned at a
alveolar crest of the maxilla.
[0124] A further advantage of the above-described method is that
the patient does not need to have clinically symptom-free sinuses.
Pre-surgical examination is facilitated. A wider range of patients
may be treated.
[0125] The present invention has been described above with
reference to specific embodiments. However, other embodiments than
the above described are equally possible within the scope of the
invention. Different method steps than those described above,
different order of the method steps, etc. may be provided within
the scope of the invention. In addition, the different features and
steps of the invention may be combined in other combinations than
those described above. The scope of the invention is only limited
by the appended patent claims.
* * * * *