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BACKGROUND OF THE INVENTION
The present invention relates to a prosthetic implant attachment system and
method for mounting a dental prosthesis such as a single artificial tooth
or crown, a partial or full denture, or a bridge on an artificial root
implant which has previously been embedded in the jaw bone in place of the
natural root.
There are at present a number of different dental implant systems in use.
Most systems include an artificial root portion or implant cylinder which
is placed into a custom bored hole in the jaw bone. A prosthetic coronal
section is attached to the artificial root portion when healing and bone
integration of the artificial root portion is complete, and a dental
prosthetic appliance such as a crown, denture, partial denture or bridge
is attached to the coronal section. The prosthetic coronal section must
pass through the connective tissue and overlying mucosa for attachment to
the prosthesis. There is no interchangeability between the currently
available implant systems, so that once a prosthesis has been mounted on
one type of artificial root, any future replacements must use the same
implant system to mount on that root. In other words, the prosthetic
section of one implant system can be secured only to the artificial root
of the same system. Since the average lifetime of a prosthesis is of the
order of 10 years, at which time a patient may have moved or be seeing a
different dentist, significant problems can arise when a replacement is
needed. The dental practitioner must always have several implant systems
on hand, since patients may have been fitted with various different types
of implants at different times, and will also need the appropriate set of
tools for mounting the various systems. This problem is likely to become
more acute as the number of individuals fitted with such implant systems
increases.
Another problem with existing attachment systems is that of adjusting for
undesirable placement angulation of the submerged artificial root. Since
the prosthetic coronal section or post normally extends coaxially from the
artificial root, and the prosthesis must be mounted on this post,
undesirable angulation may make it difficult to align the prosthetic tooth
or teeth with the natural tooth line. This is a particular problem with
front teeth, since for cosmetic reasons it is desirable that a screw or
the like securing a crown or artificial tooth to the post does not exit
through a front face of the tooth. Some attempts for adjusting angulation
are provided in various existing systems, for example providing the post
or prosthetic coronal section with a bendable neck portion, but this
results in a weakened area which is liable to break. In other systems
fixed angled portions are provided on the post, but this allows one
angular adjustment only and thus does not allow easy adjustment or a wide
range of angulation adjustment.
Another problem with replacing front teeth with existing implant systems is
that the post or prosthetic section securing the artificial tooth or teeth
to the implant will often be visible between the base of the tooth and the
gum, particularly as the gum recedes naturally with time. This results in
an unattractive gap which can be seen when the wearer smiles.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an implant attachment
system which can be used to secure a prosthesis to any artificial root
implant cylinder.
According to the present invention, a dental implant attachment system for
mounting a dental prosthesis on an artificial root implant comprises a
base member having a lower end sized to seat on the upper end of the root
implant cylinder and an upper end having an outer diameter substantially
equal to that of a tooth for mounting on the implant, and a prosthetic
head having a lower end for mounting on the upper end of the base member
and an upper end for securing to a dental prosthesis. A securing assembly
is provided to secure the base member to the implant cylinder and the
prosthetic head to the base member.
Preferably, a series of different base members and prosthetic heads are
provided in an attachment kit, with a number of different prosthetic heads
in the kit being attachable to each of the base members. The base members
include members sized to seat on any existing artificial implant cylinder,
and members having upper ends of diameter equivalent to a variety of
average natural tooth sizes, for example in the range from 3.5 mm to 7.0
mm. The prosthetic heads have lower end cuff portions sized to seat on the
upper end of each of the base members with no overlap, and each have an
upwardly projecting post portion preferably of tapering conical shape. The
prosthetic heads include post portions at angles between 0 and 30 degrees
to the cuff portion, to allow for angulation adjustment. Alternatively, a
variable angle prosthetic head may be provided which comprises an annular
member and a post section with a swivel engagement with the annular member
to allow the post section to be swiveled into a desired angle relative to
the base member axis before locking it in the desired position.
The prosthetic heads preferably include a 0.5-2 mm wide butt joint which
allows for a thickness of metal and ceramic to be placed between the post
portion and the edge of the base portion. This section may be customized
or shaped as desired to further improve cosmetics by following gingival
form.
Any suitable securing devices such as screw fasteners may be provided for
securing the selected base member to the implant cylinder and for securing
the selected prosthetic head to the base member. The upper end of the base
member and lower end of each prosthetic head include interengageable
indexing formations for securing the prosthetic head against rotation on
the base member in any one of a series of fixed, indexed positions. Thus
the angled prosthetic heads can be rotated through 360 degrees relative to
the base member to select the indexed position providing the best possible
angulation before locking the head to the base member. In one arrangement
the interengageable formations comprise corresponding male and female
configurations each having flats around their outer diameter. The male and
female configurations may, for example, comprise hexagon or octagon nut
and bore formations. With an octagonal locking formations, the prosthetic
head can be engaged in any one of eight possible different angular indexed
orientations relative to the base member. The interengageable locking
formations for providing the fixed, indexed positions may alternatively
comprise a series of teeth, grooves or serrations, for example.
The interengageable formations will prevent rotation between any of the
prosthetic heads and the base member to which they are attached, reducing
the risk of loosening of the attachment structure as a result of dental
forces, and also allow rotation of the angled heads into any one of a
plurality of different possible fixed, indexed positions to adjust for the
optimum orientation of the angled heads in the jaw. The fixed orientation
of interengageable locking formation of the base member when mounted in
the jaw establishes an indexing position for orientation of the finished
prosthesis made in the laboratory. Thus the prosthesis can be precisely
positioned on to the base member in the mouth.
In an alternative embodiment, the prosthetic head includes an annular
member having a concave indent for seating a convex end element of the
post portion. The post portion can be swiveled relative to the concave
indent to adjust the angle of the prosthetic head post as desired. This
embodiment also rests upon and is orientated to a base member by an
interengageable locking formation. A suitable fastener is provided for
locking the seat element in the desired orientation.
Thus, in order to mount any type of prosthesis on any artificial root
implant cylinder, the base member having the appropriate lower and upper
end dimensions is selected. This member is suitably mounted and secured to
the implant cylinder. An impression head is then fastened to the base
member, and impression is taken. The impression head is removed and may be
replaced with a healing cap or with a temporary crown form. An analog of
the base member is then fastened to the impression head and the analog and
impression head are inserted into the impression. A cast is then made,
into which the analog is set at the appropriate orientation. The
impression head is removed, and the cast model of the patient's jaw with
the embedded analog is used in a laboratory on a dental surveyor to orient
an appropriate prosthetic head, either with a straight, angled or
swivelling post section for increased adjustability. The selected
prosthetic head is mounted on the base member analog at the optimum
angular orientation. An appropriate wax pattern is crafted by those
skilled in the art to exactly fit the prosthetic head. The prosthetic cast
is then made from the wax pattern, and the parts are disassembled. The
dentist can then reassemble the parts, mounting the prosthetic head on the
base member in the patient's jaw and then cementing or otherwise attaching
the prosthesis to the prosthetic head.
The indexing locking formations between the prosthetic head and base member
allows indexing between clinical and laboratory work and also allows for
correction of undesired placement angulation of the submerged implant
cylinder by choice of suitable angled prosthetic heads. They also
effectively make the attachment structure into a single fixed unit since
the separate parts cannot rotate relative to one another once they are
secured together. Thus the prosthetic and artificial root implant are
effectively joined together by means of a single fixed unit and will be
more secure.
The sizing of the base member to that of natural teeth improves the
appearance of the attachment, particularly if the outer surface of the
base member is covered with a suitable tooth colored ceramic. Although a
prosthesis such as a crown would originally extend down slightly below the
crest of the gum line around the implant, the gum may recede with time and
thus the base member or transmucosal element may become visible. However,
when the base member is of equivalent size to the crown and is tooth
colored, this ceases to be a significant cosmetic problem. Alternately,
one can make use of the inherent interchangeability of the system and duly
elect a new shorter base member to replace the original member.
Preferably, the prosthetic head cuff portion is of larger diameter than the
post portion to leave an annular rim or "waxing butt joint", providing for
fabrication of a thicker and thus mechanically stronger layer of ceramic
in the prosthetic crown or bridge. This thickness also allows for more
predictable ceramic color customization. The rim is suitably in the range
of 0.5 to 3 mm in width, depending on the tooth size. The post portion is
preferably conical, and may have suitable rotation resisting formations on
its outer surface to resist rotation of the prosthesis on the prosthetic
head. These formations may comprise opposed flats or grooves, for example.
Such formations are less critical in the prosthetic heads having angled
post portions, which will inherently resist rotation.
The prosthetic head cuff portion annular rim area is made of adequate
thickness or depth to allow customized reshaping of the rim by those
skilled in the art to approximate the exact shape of the gingival cuff,
thus allowing optimal cosmetic prosthetics for anterior teeth to be
achieved.
The prosthesis is cemented or otherwise attached to the prosthetic head.
The prosthesis is preferably removable by means of a retrieval element
fashioned into the prosthesis which allows the prosthesis to be removed
from the prosthetic head. This element consists of an all threaded screw
within a threaded tube cast into the prosthesis above the prosthetic head.
It may be used in two fashions. Once cemented, the prosthesis may be
separated from the prosthetic head by turning the screw which pushes down
on the underlying head and breaks the cement seal. In an alternative
arrangement, a longer screw is threaded through the tube and into an
expansion module fitted into the recess at the top of the straight
prosthetic head. Turning the screw tightens the expansion module against
the walls of the recess and secures the crown without cement. Turning the
screw in the opposite direction releases the prosthesis.
In the event of extreme bony resorption of the alveolar ridges, extension
sections may be inserted between the base member and the prosthetic head
to accomodate the interalveolar distance. These sections are made to
varying appropriate lengths and have matching interengageable formations
to the base elements and prosthetic heads and are thus connected in the
manner previously described to these elements.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be better understood from the following detailed
description of some preferred embodiments, taken in conjunction with the
accompanying drawings, in which like reference numerals refer to like
parts, and in which:
FIG. 1 is a side elevation view showing one version of the dental implant
attachment system according to the invention in place securing a
prosthesis to an artificial root implant embedded in a jaw bone;
FIG. 2 is an enlarged sectional view taken on the line 2--2 of FIG. 1;
FIG. 3 is a perspective view of a first type of head element for use in the
system shown in FIG. 1;
FIG. 4 is a perspective view of a first type of base element for use in the
system shown in FIG. 1;
FIG. 5 is a side elevation view of an alternative, inclined head element;
FIG. 6 is a side elevation view of another inclined head element;
FIG. 7 is a side elevation view of an alternative, offset head element;
FIG. 8 is a side elevation view, with portions cut away, of a base and
adjustable head element according to an alternative embodiment;
FIG. 9 is a side elevation view of an alternative base element according to
the invention with an expandable portion for attachment to an artificial
root implant cylinder;
FIG. 10 is a sectional view taken on line 10--10 of FIG. 9, showing the
base element of FIG. 9 attached to an implant cylinder and assembled with
one of the possible head elements for mounting a prosthesis;
FIG. 11 is a side elevation view, partially cut away, of an impression head
element for use in taking an impression of the location and orientation of
a base element mounted on an implant cylinder;
FIGS. 12 to 19 show successive stages in a method of intraoral impression
taking, transfer to a dental laboratory in a stone mounting, fabrication
of a custom prosthesis and mounting a dental prosthesis in the jaw using
the attachment systems of FIGS. 1 to 10;
FIG. 20 is a side elevation view, partially in section, showing an example
of an incisor temporary crown for use with the attachment system of this
invention;
FIG. 21 is a side elevation view similar to FIG. 1 showing an example of a
bicuspid temperary crown;
FIGS. 22 to 32 show various examples of alternative interengaging
formations for adjustably locking the prosthetic head to the base member
in various angular positions;
FIG. 33 is a side elevational view of an improvement to the base element
illustrated in FIG. 9;
FIG. 34 is a sectional view taken substantially on the line 34--34 of FIG.
33, showing show the base element or member is secured in position;
FIG. 35 is a side elevational view of an implant analog pin to replace the
base member analog illustrated in FIGS. 15 through 18;
FIG. 36 is a side elevational view of an orthodontic prosthetic head for
use with the base members of FIGS. 1 and 2 and FIGS. 9, 10 and 12; and
FIG. 37 is a top plan view of the orthodontic prosthetic head illustrated
in FIG. 36.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The dental implant attachment system shown in the drawings is designed to
allow a prosthesis to be mounted on any existing implant cylinder or
artificial root. The attachment system 10 when in place as shown in FIGS.
1 and 2 comprises several basic parts, including a base member 12 designed
to seat on the upper end of an implant cylinder 14 embedded in the jawbone
16, and a prosthetic head or post 18 designed to seat on the upper end of
member 12 and to form a mounting for seating a prosthesis such as a crown
20 or other prosthetic device.
A first fastener or securing device is provided for securing the base
member 12 to the implant cylinder 14. The fastener may be of any suitable
type depending on the internal configuration of the implant cylinder. In
the version shown in FIGS. 1 and 2, the implant cylinder is of a type
having internal screw threads and a hexagonal projection 22 at its upper
end for interengagement with the appropriate connecting part. Thus, in the
embodiment of FIG. 1, the base member 12 has a corresponding hexagonal
indent 24, as best shown in FIG. 4, for mating engagement with projection
22 to secure the base member against rotation.
In the version of the system shown in FIGS. 1 and 2, the base member is
secured to the implant cylinder and the head element 18 is secured to the
base member by the same fastener device, a single headed screw fastener 26
which projects through an axial bore 28 in the head 18, through an aligned
axial bore 30 in base member 12, and into the screw-threaded bore in the
implant cylinder. The dimensions of the screw threaded end of the fastener
26 correspond to those of the screw threaded bore in cylinder 16. The head
32 at the upper end of fastener 26 seats on an internal shoulder 34 in
head bore 28.
FIGS. 9 and 10 show an alternative fastener arrangement for securing the
attachment system to the implant cylinder. In this arrangement a second
type of base member 35 is provided, which has an expansion fastener 36
projecting from its lower end and dimensioned to fit closely into the bore
of implant cylinder 38, which may have internal screw threads as shown or
alternative configurations. The fastener has fingers 40 separated by slits
42 at its lower end. A headed expansion screw 44 is designed to extend
through axial bore 46 in base member 36 and into a threaded bore in
expansion fastener 35 to urge fingers 40 outwardly into gripping
engagement with the implant cylinder bore. The fastener may have screw
threads or other formations on its outer surface for improved gripping
engagement with the implant cylinder bore. The expansion fastener
dimensions are chosen according to the dimensions of the implant cylinder
bore to which it is to be attached, and different diameter expansion
fasteners may be provided on different base members for attaching to
different types of implant cylinders. The expansion fastener will restrict
rotation of the base member relative to the implant cylinder as well as
axial movement of the base member out of the cylinder.
The same prosthetic heads 18 can be secured to a base member 12 of the type
shown in FIGS. 1, 2 and 4 or the base member 35 with an expansion fastener
projection as shown in FIGS. 9 and 10. Thus, the appropriate base member
can be selected according to the type of implant cylinder to which the
prosthesis is to be secured. In practice any appropriate type of fastener
for securing the base member to the implant cylinder may be provided,
which both restricts rotation of the base member and also movement of the
base member out of the cylinder. The expansion fastener of FIGS. 9 and 10
provides a positive but reversible lock to the walls of the artificial
root recess. Permanent retention may be achieved, if desired, by cementing
the fastener into the recess.
In the embodiment of FIGS. 9 and 10, the head is secured to the base member
by means of an additional screw fastener 48 which extends through bore 28
in the head 18 and into a screw threaded bore at the upper end of base
member 35. Thus the base member in FIGS. 9 and 10 is provided with a screw
threaded configuration at its upper end sized to receive screw fastener
48, and a counterbore at its lower end with a screw threaded configuration
for receiving the expansion screw.
In the embodiment of FIGS. 1, 2 and 4 and in the embodiment of FIGS. 9 and
10, the lower end of the base member is of diameter corresponding to the
external diameter of the upper end of the implant cylinder on which it is
to be seated, so that there is no overlap for ingress of bacteria or the
like. The upper end of the base member is of diameter substantially
corresponding to the average tooth diameter of the tooth which is to be
mounted on the implant. Thus the base member may be a straight cylinder,
but is more likely to be of inverted frusto-conical shape as shown in
FIGS. 1, 2, 4, 9 and 10 with the diameter of the lower end being less than
that of the upper end. The external diameter averages of natural teeth
generally range between 3 and 7 mm (Black's anatomical tooth averages) and
preferably a range of base members is provided with upper diameters in
this range, for example 3.5 mm, 5 mm and 7 mm, and with lower diameters
for fitting all standard implant cylinders. Thus the lower diameter of the
base members may range from about 2.8 mm to 7 mm, but may be outside these
dimensions in some cases. Base members of varying height will also be
provided, to allow for varying gingival thicknesses and natural recession
of the gingiva. For example, base members of three or more different
heights may be provided, such as 2 mm, 3 mm and 4 mm.
The base member 12 or 35 is designed to extend from the top of the implant
cylinder embedded in the jawbone through the overlying gingiva 50 as shown
in FIG. 1 for attachment to a prosthetic head. Preferably, a series of
different straight and angled prosthetic heads of appropriate dimensions
for fitting the various base members is provided. FIGS. 3,5 and 6 show
three different prosthetic heads 18, 118 and 218. Each head 18, 118 and
218 is of the same basic shape, comprising an annular cuff portion 52
designed to seat on the upper end of the base member and a post portion
54, 154 and 254 projecting upwardly from the cuff portion. In head 18 the
post portion 54 is straight, or at 0 degrees to the head axis. In the head
118 shown in FIG. 5 the post portion 154 is angled at about 10 degrees to
the head axis, and head 218 shown in FIG. 6 has a post portion 254 angled
at about 20 degrees to the head axis. The prosthesis 20, which may
comprise a crown or other dental prosthetic device, can be cemented or
otherwise attached over the straight head 18 as indicated in FIG. 1, or
over either of the angled heads shown in FIGS. 5 and 6.
Extension sections of an additional 2 mm, 3 mm and 4 mm may further be
inserted between the base member and prosthetic head to accomodate
excessive interalveolar distance created by extreme alveolar ridge
atrophy. These sections may be straight or may be angled to allow offset
extension of the prosthetic heads. FIG. 7 shows an angled extension 49
secured between base member 12 and prosthetic head 18.
The cuff portion 52 of each prosthetic head has an external diameter
corresponding to that of the upper end of the selected head member, so
that it sits on the head member with no overlap which could form a site
for bacteria growth. It may be a straight cylinder as shown, or may have a
tapered outer surface. The post portion 54, 154 and 254 of each head is
preferably of tapering, frusto-conical formation as shown in FIGS. 1 to 3,
5 and 6 and of smaller dimensions than the cuff portion to leave an
annular rim 56 forming a waxing butt joint providing for creation of a
thicker, stronger and more cosmetic ceramo-metal prosthesis. The thickness
of the annular rim to the base section is designed to allow custom
recontouring of the rim to match gingiva cuff form.
Preferably a number of different straight and angled heads are provided
with lower ends dimensioned for fitting the upper end of each available
base member. More than two different angled heads may be provided, with
angles varying between 0 and 30 degrees to the cuff portion. The straight
head of FIG. 3 and the angled heads of FIGS. 5 and 6 secure to the
selected base member in an equivalent manner. Like reference numerals have
therefore been used where appropriate. The inclined heads shown in FIGS. 5
and 6 allow adjustment of the angulation of the implant cylinder, as
explained in more detail below.
The post portion is preferably provided with suitable resistance formations
to resist rotation of the attached crown or other prosthesis 20 relative
to the head. In the embodiment shown in FIGS. 1 and 2, the resistance
formations comprise opposed flats 60 on opposite side faces of the post
portion. The provision of resistance formations is more critical in the
straight head version of FIG. 3 than with the inclined heads of FIGS. 5
and 6, where the angled post portions will themselves inherently resist
rotation of the secured crown.
Suitable interengageable formations are provided between the upper end of
the base member and the lower end of the head to allow the head to be
locked in any one of a plurality of fixed, indexed positions relative to
the base member and to prevent relative rotation between the head and base
member which could result from dental forces. In the embodiments shown in
FIGS. 1 to 6, 9 and 10, the interengageable formations comprise
corresponding male and female configurations 62, 64 at the upper end of
the base member and the lower end of the head, respectively. The extension
section 49 of FIG. 7 will have corresponding male and female
configurations 65, 67 at its upper and lower ends, respectively for
connection to the selected prosthetic head and base. The configurations in
the preferred embodiment shown comprise a male and female configuration
each having an octagonal outer surface, but clearly alternative formations
may be used, for example hexagonal or other multifaceted forms as well as
ribs, teeth, star shapes, serrations, grooves and other formations. Also,
the male formation may be provided on the head and the female on the base,
if desired.
FIGS. 22 to 32 show various possible alternative formations for adjustably
interlocking the head to the base. In FIGS. 22 and 23, for example, the
prosthetic head 140 has a sawtooth or grooved pattern 142 on its lower end
face, while the base member 144 has a corresponding, interengageable tooth
pattern 146 on its upper end face. The head and base member are otherwise
the same as shown in FIGS. 3 and 4. Clearly several angled heads may be
provided with the same tooth pattern for engagement with base member 144.
The teeth on head 140 and base member 144 will engage to allow the head to
be locked against rotation in any one of a plurality of fixed, indexed
positions relative to the base member.
FIGS. 24 to 26 show another alternative interlocking formation. As shown in
FIGS. 24 and 25, angled or straight prosthetic heads 148, 150,
respectively, are provided with a series of holes or blind lines 152 in
their lower end faces 158. The holes are arranged in a circular array, as
can be seen in FIG. 25. The base member 160 has one or more pins 162
projecting from its lower end face (see FIG. 26) for selective engagement
in one or more of the vores in the end face of the selected prosthetic
head. This arrangement also allows the head to be locked against rotation
in any one of a number of fixed angular positions relative to the base
member.
Another alternative is shown in FIGS. 27 to 29. In this version the
straight and angled prosthetic heads 164 (FIG. 27) and 166 (FIG. 29) each
have a star-shaped, indented formation 168 in their end face 170 while the
base member 172 (FIG. 28) has a corresponding star-shaped projection 174
in its end face 176. The indented and projecting formations interengage in
a plurality of fixed, indexed positions to lock the prosthetic head
against rotation on the base member.
FIGS. 30 to 32 show yet another alternative in which the straight and
angled prosthetic heads 180 (FIG. 30) and 182 (FIG. 31) each has an
indentical, multi-sided or polygonal indent 184 in its lower end face 186
while the base member 188 has a corresponding polygonal projection 190
from upper end fase 192. This is similar to the version shown in FIGS. 3
to 6, except that the polygonal formations 184, 190 have a greater number
of facets or flats. In practice any desired number of flats or sides may
be provided in the polygonal formations, with the number of sides
determining the number of different, fixed indexed positions of the
prosthetic head relative to the base member.
The prosthetic heads and base members of FIGS. 22 to 32 are otherwise the
same as those shown in FIGS. 3 to 6 and are secured together in an
equivalent manner.
In the embodiment shown in FIGS. 1 to 6, the head may be locked against
rotation in any one of eight possible different angular positions relative
to the base member. Thus, with the angled versions of the head shown in
FIGS. 5 and 6, the head can be rotated relative to the base until the
optimum orientation for the angled post is located, at which point the
female octagon 64 on the head can be mated with the male octagon on the
base member to lock the head against rotation out of that optimum
position. This allows for correction of undesirable placement of the
submerged root implant cylinder, for example.
Once the head and base member are interlocked via formations 62 and 64,
relative rotation is prevented and thus the parts cannot become loose as a
result of inadvertent unscrewing of the fastener screw or screws. The head
and base member act as a single fixed unit when secured together, and the
prosthetic and implant cylinder are securely joined together by this fixed
unit. Thus the risk of loosening of the prosthetic fixture as a result of
dental forces during normal use is reduced. Extension section 49 of FIG. 7
may be secured to the base and prosthetic head with fastener screws in a
similar fashion.
FIG. 8 of the drawings shows an alternative version of the head for
allowing a greater degree of angle adjustment. In this version of the post
76 of the head 66 has a swivelling attachment to the cuff portion 68. The
base member 12 is the same as that shown in FIG. 4, and the cuff portion
has a female interengaging configuration 64 at its lower end for
interengagement with the male configuration 62 at the upper end of the
base member. The lower end of the base member in FIG. 8 may be the same as
that shown in FIGS. 1, 2 and 4 or as shown in FIGS. 8 and 9, and its
external dimensions are chosen in the same way.
The cuff portion of head 66 has a conical indent 72 in its upper end face
70. The post has a hollow, convex seat portion 74 for seating in concave
indent 72, and a post or head portion 76 which has a screw threaded
projection 78 for securing it in corresponding internal screw threads 80
in the seat portion. The seat portion 74 has a through bore 82 at its
lower end through which headed fastener screw 84 projects to secure the
prosthetic head seat portion to both the cuff portion 64 and the base
member 12 and to secure the base member to the implant cylinder bore, as
described above in connection with FIGS. 1 and 2. Alternatively, screw 84
may simply secure the seat portion and cuff portion to the base member,
with an expansion fastener and screw securing the base member to the
implant cylinder as in FIGS. 9 and 10.
The dimensions of bore 82 are larger than those of screw 84, as seen in
FIG. 8, so that the seat portion 74 can be swivelled when the screw is
loosened. The seat portion 74 is swivelled into different angular
orientations relative to the cuff portion until the optimum angulation is
found. Preferably, the dimensions of bore 82 allow the post portion to be
tilted up to about 20 degrees relative to the cuff portion and it can be
rotated through 360 degrees around the cuff portion indent to determine
the optimum orientation. Thus, rather than providing several different
heads at different fixed angles, as in FIGS. 1 to 6, a single swivelling
head can be provided as shown in FIG. 7 to provide a greater degree of
angulation adjustment.
The convex portion and concave indent may have cooperating star-shaped or
ther interengageable formations for improved locking engagement when the
selected angular orientation is achieved.
In the version shown in FIG. 8, the base member will first be mounted on
the implant cylinder. The cuff portion 68 will then be mounted on the base
member via interengaging formations 62, 64. Seat portion 74 will then be
loosely secured in the cuff portion indent, and swivelled and tilted until
the optimum orientation is located. At this point the screw will be
tightened to lock the seat in the selected orientation, and the post
portion will be screwed into the seat portion to secure the parts
together. The post portion in FIG. 8 may also be provided with suitable
resistance formations such as opposed flats as in FIG. 1 to resist
rotation of the prosthesis on the post.
Since the upper ends of the prosthetic heads in FIGS. 1 to 6, 9 and 10 are
open to receive a suitable fastener, a cementation cap 86 may be provided
for mounting over the open end of the head before cementing or otherwise
attaching a prosthesis to the head, as shown in FIG. 2. The cap suitably
comprises a short cylindrical shaft with a short flat head which slips
into and down flush with the upper end of the prosthetic head, for use
when a crown, bridge or other prosthesis is to be cemented onto the head.
a Alternatively, as indicated in FIG. 8, a female threaded recess 88 may
be provided to accept various standard locking systems for securing custom
crowns to posts, such as a simple screw. A screw having a head containing
a spherical snap-lock indent for a snap-in anchor type attachment as
described in U.S. Pat. No. 3,787,975 of Zuest may be provided for fitting
in the upper end of the prosthetic head. Alternatively, a specialized
prosthetic head may be provided with a recess for receiving a snap-lock
attachment of this type directly, which may be used as a transitional
attachment between removeable and fixed prosthetics, for example. Another
type of base member may also be provided with a spherical snap-in recess
for receiving a snap-in anchor attachment, for example.
FIG. 1 shows an alternative arrangement including a disengaging or
retrieval means for dismounting a prosthesis from the assembly. The
retrieval means consists of an expansion module 92 inserted into the upper
end recess of the head and an "all-thread" screw member 94 within a
threaded tube 95 cast into the prosthesis 20.
Turning screw 94 in a first direction tightens the expansion module 92
against the walls of the recess and secures the crown without cement. When
the screw is turned in the opposite direction, the expansion module
loosens and the prosthesis is released.
In an alternative, the separation or retrieval system may simply comprise
an "all-thread" screw in a threaded tube cast in the prosthesis above the
top of the prosthetic head. Once cemented, the prosthesis may be separated
from the prosthetic head by turning the screw, pushing down on the head or
cementation cap and breaking the cement seal.
In each case, the upper end of the screw 94 will be provided with a
suitable slot or the like for receiving a screwdriver, or preferably with
a hexagonal indent for receiving an Allen wrench for rotating the screw.
Each of the fastener screws securing the base member and prosthesis head
together, either the single screw fastener of FIGS. 1 and 2 or the two
fastener screws of FIGS. 9 and 10, are provided with suitable
configurations on the upper face of their heads for receiving a tool for
tightening and loosening the screws as desired. Instead of the standard
screwdriver slots, the screw heads are preferably provided with hexagonal
indents 90, one of which can be seen in the expansion fastener screw of
FIG. 10, for example, for receiving the hexagonal end of an Allen wrench
of suitable dimensions for tightening or loosening the screw. This allows
for easy positive engagement between the tool and the screw head, unlike a
standard slot for receiving a screw driver which can sometimes be
difficult to locate and may become scored, particularly in small scale
parts of this nature.
The parts of the attachment system described above will all be made of a
suitable metal such as titanium. However, parts which may be exposed may
be coated with a suitable tooth colored ceramic for cosmetic purposes.
Thus the base external surface may be ceramic coated.
The attachment system is preferably provided in the form of a kit
containing base members of various heights, tapers and upper and lower end
diameters, and with different fastener devices for securing the various
base members to root implant cylinders of various standard types and
dimensions, and prosthetic heads of various dimensions and angles, as well
as swivelling heads, for mounting on the selected base members, along with
the appropriate screw fasteners for securing the base members to the
implant cylinders and the heads to the base members. The kit also
preferably includes tools for tightening and loosening the screw
fasteners, as well as other specialized parts for use in dental laboratory
work, as described in more detail below.
The method of attaching a prosthesis to any artificial root cylinder | | |
