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Description  |
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This invention relates to a universal pin for oral implantoprosthesis
comprising an autonomous double-taper fixing system.
The new pin is defined as "universal" because it can be constructed in
various sizes and dimensions, and completely replaces every missing dental
element, for any variation in anatomy and for any person.
At the present time, oral implantology is directed essentially towards
three types of implant, namely depth, extension and surface.
All these types of oral implant require highly specialised implantologists,
of which there are few compared with requirements and with the number of
dentists, lead to very high cost for the patient, and finally offer little
reliability, particularly in the case of completely edentulous mouths.
In addition to these negative aspects which exist generally for any type of
known implant, there are specific defects in each method, as follows:
DEPTH METHOD
This method comprises essentially
(a) endo-osseous spiral implants
(b) endo-osseous pin implants.
Endo-osseous spiral implants (a) are constituted essentially by hollow,
solid or similar spiral elements having a length of 16 to 21 mm, and
constructed of a suitable metal. These elements are implanted into the
maxilla and/or mandible, and the dental prostheses are mounted thereon
either by screwing or by pressure.
They have the following main drawbacks (Muratori: "L'implantologia orale
multitipo", Publisher Castelli--Bologna 1972--pages 10, 50, 119): they
necessarily require the support of natural teeth, and hence cannot be used
for completely edentulous mouths; they must be fitted very deeply in order
to create a lever arm which is very long relative to the external arm; the
spiral has very little grip in the cancellous bone; the part emerging from
the bone is reduced to a minimum (about 2 mm) for stability reasons, and
consequently makes it very difficult to give the crown of the prosthesis
the exact inclination for correct dental alignment; it is necessary to
await the formation of the fibrous sleeve produced by the body for the
implant to be able to adhere properly to the bone and to become fixed to
it.
As this natural process requires several months, there is a long period in
which the implant remains unstable and exposed to the danger of and damage
deriving from infiltration.
Endo-osseous pin implants (b) are represented essentially by the Verbowsky
pin, which is constituted by a head on which the prosthesis is fitted, a
neck and a downwardly tapering body terminating in a point which is
implanted into the bone. The body comprises a longitudinal slit in its
central region, and a horizontal bore which inevitably weakens its
structure.
Having made a hole in the alveolar bone, the pin is "fired" into its
interior.
Theoretically, on implantation, the two parts into which the pin body is
divided by the longitudinal slit should open outwards to anchor the pin to
the bone, in a manner similar to the natural root. In practice, the
sponginess of the bone does not allow anchoring in the proposed manner,
and the pin remains unstable.
EXTENSION METHOD
This method consists essentially of implanting into the maxilla or mandible
a strip having a length of some cm and of variable depth. One or more pins
form an integral part of the strip, and emerge from the gingiva to allow
fixing of the prosthesis. The main drawbacks of this method are firstly
the difficulty, and indeed impossibility, of making in the bone a
perfectly linear slot to which the strip can adhere with continuity;
consequently, the implant is instable.
Again in this case, stability depends exclusively on the reconstitution of
the osseous tissue. However, as stated the natural process requires
several months, and during the whole of this time not only is the implant
unstable, but is continuously exposed to the danger of infiltration and
its effects.
SURFACE METHOD
This implantation method consists essentially of preparing for each case
metal grids of special shape, for example in the shape of an "eight", from
which the pin for the prosthesis emerges.
These grids are implanted horizontally into the bone by incising it only
superficially; in this case, retention should be ensured essentially by
the periosteum and gingiva.
The surface method, although not having the drawbacks of the extension
method in which the bone is deeply incised, in no way ensures a secure and
durable implantation. Moreover, the implantation must be carried out in
two successive stages, which each time require the opening of the
fibromucosa, with the imaginable negative effects deriving from the
repeated intervention.
The applicant has now created, and forms the subject matter of the present
invention, a pin for endo-osseous depth implantation which is arranged to
constitute the basic element for anchoring fixed prosthesis, and in
particular the autonomous pillar which, when fitted with a prosthetic
crown, replaces any natural tooth.
It has characteristics which are totally different from any type of
implantation element constructed up to the present time, and in particular
any endo-osseous spiral or pin implantation element of known type. The new
pin, as described in detail hereinafter, enables all the drawbacks of the
previously known methods as summarised heretofore to be overcome.
The new pin for oral implantology according to the invention is
characterised by being constituted by two separate elements, and, when
assembled, by presenting in its lower endo-osseous part a particular
structure which comprises two frusto-conical segments of opposing
orientation, namely an upper pre-existing segment with its major base
facing upwards, and a lower segment which is formed at the moment of
assembly and has its major base facing downwards.
The assembly of this double-taper structure ensures perfect retention of
the pin in the bone, independently of the reconstitution of the bone
tissue, and further ensures an absolutely autonomous implantation, i.e.
without support by the natural teeth being necessary.
The application of the pin is also very simple, as it requires only very
limited drilling of the bone, which is carried out in a single sitting.
The invention will be more apparent from the description given hereinafter
of two possible embodiments thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1a is a view toward the bottom of FIG. 1b;
FIG. 1b is a longitudinal sectional view;
FIG. 1c is a sectional view taken on the arrowheaded line of FIG. 1b;
FIG. 2a is a view toward the bottom of FIG. 2b;
FIG. 2b is a side elevation, partly in section, of the solid element;
FIG. 3a is a view from below of FIG. 3b;
FIG. 3b is a side elevation, partly in section, of the element of FIGS. 1b
and 2b assembled together;
FIGS. 4, 5, 6a and 6b show the device for giving the pin the required
inclination;
FIGS. 7 and 8 are side views, partly in section, of the upper element of a
second embodiment;
FIG. 9 is a side view of assembly of the upper and lower elements; and
FIGS. 10 and 11 are front and side views of the lower element.
The first embodiment of the pin is illustrated on the first drawing, which
comprises FIGS. 1, 2 and 3. The other embodiment is illustrated on the
third drawing, which comprises 7, 8 and 9.
The illustrated pins are constructed of titanium alloy and in various
sizes. They can however be constructed of different metals or metal
alloys.
The pin illustrated on the first drawing comprises a hollow element 1,
which is shown in FIG. 1a as a view from below and as a central
longitudinal section in FIG. 1b, and a solid element 7 which is shown in
FIG. 2a as a view from below and in FIG. 2b as a partly sectional side
view.
FIG. 3a shows a view from below and in FIG. 3b a partly sectional side view
of the pin in its final assembled state, resulting from fitting the
element 1 and the element 7 together.
The following functionally separate parts are visible in the hollow element
1: an upwardly flared frusto-conical upper part 4, in which the outer wall
and inner wall can have equal or different inclination; a cylindrical
central part 3 with its outer wall and inner wall parallel; and a lower
part 6 with its outer cylindrical wall of diameter equal to the diameter
of the central part, and with its inner wall narrowing downwards to form a
smooth or threaded taper.
The lower part 6 comprises two through slots 2 which are orthogonal to each
other, and are shown in detail at the foot of FIG. 1.
On its upper part 4, the element 1 comprises a projecting rim 5.
With particular reference to FIG. 2, the following functionally separate
parts are visible in the solid element 7, which is inserted into the
hollow part of the element 1: a frusto-conical upper part or head 13 which
has its major base at the bottom, and which projects from the gingiva in
order to support the prosthesis; a frusto-conical central part or neck 11
with its major base at the bottom and having a cavity 12 worked into its
upper part as shown in the figure; and a lower part or body in which three
segments can be distinguished, namely an upper frusto-conical segment 10
with its outer profile exactly corresponding to the inner profile 4 of the
element 1 with which it has to mate perfectly, a central cylindrical part
9 of diameter such as to enable it to be perfectly inserted in a sealed
manner into the central part 3 of the element 1, and a terminal part 8
which can be a simple extension identical to the part 9 or can be threaded
to correspond to a possible thread on the terminal part 6 of the element 1
into which it is to be inserted and to project below it by a few tenths of
a millimeter.
The new pin according to the present invention is fitted as follows:
(a) the gingiva is incised, and a hole is made in the maxilla or mandible
with a diameter equal to the diameter of the central part 3 of the element
1. The element 1 is pressed into this hole so that the rim 5 rests by its
lower part on the bone, and seals against it to prevent any possibility of
infiltration.
(b) the element 7 is introduced into the element 1, and its lower part 8 is
forced into the lower part 6 of the element 1 either by simple vertical
pressure if the facing walls are smooth, or by screwing if they are
threaded. By means of this operation, the four parts into which the
segment 6 is divided are forced outwards, and the profile of this latter
segment is changed from cylindrical to downwardly flared frusto-conical.
In its final state, which is clearly visible in FIG. 3, the new pin thus
comprises two tapers in the endo-osseous part which open in opposite
directions to create solid fixing both in the compact bone region and in
the cancellous bone region. The pin also comprises a slight rim 5 which
"closes" on to the bone, and a slight groove 12 which "closes" on to the
gingiva. The terminal part 13 emerges completely, and constitutes the
absolutely stable and secure connection point for the prosthesis.
The second embodiment of the new universal pin according to the invention
is shown in FIGS. 7, 8 and 9.
With particular reference to FIGS. 7 and 10, it can be seen that in this
case the two constituent elements of the double-taper pin are the
following:
a first base element 1 constituted by a wedge of trapezoidal cross-section
terminating in a rounded base part in the form of a spherical cap 4 (this
element is shown in frontal view in FIG. 10 and side view in FIG. 11); and
a second element 2, comprising three segments with different functions,
namely a head 6 of frusto-conical structure forming the part which emerges
the gingiva and creates the support for the prosthesis, a neck which is
also of frusto-conical structure and is connected to the head by a groove
7 which ensures perfect "closure" on to the gingiva, and the actual body
which comprises an upper part having a frusto-conical structure which is
inverted relative to that of the neck and slightly withdrawn from it in
such a manner as to leave a rim which rests on the bone to form a "seal"
thereon, and a lower cylindrical part which is traversed over its entire
length by a slot of such a width as to allow insertion of the element 1.
The new pin is clearly visible in its final state in FIG. 9, from which it
can be seen that mounting the second element over the first causes the
lower part of the element 2 to widen outwards and to create a terminal
frusto-conical structure which together with that existing in the upper
part of the body forms the double taper which is characteristic of the new
pin, and which ensures absolute stability and rigidity of the osseous
implantation.
The pin is fitted in the following manner:
the gingiva is incised, and a hole of diameter equal to that of the pin is
made in the bone. The two elements 1 and 2, previously coupled to each
other by simple contact, are introduced together into this hole. The pin
is then inserted until it touches the bottom of the hole.
This operation causes the two parts into which the slot 3 divides the lower
part of the element 2 to widen outwards, and thus to form the second taper
of oval cross-section which together with the first, which is of circular
cross-section and is already present in the upper part of the body of the
element 2, provides absolutely stable fixing of the pin to the bone.
The new pin, both in the embodiment shown in FIG. 3 and in the embodiment
shown in FIG. 9, can comprise in its lower part a groove as shown at the
point 5 of FIG. 7. Such a groove further enhances the fixing of the pin to
the bone, with the formation in its interior of new fibrous or osseous
tissues.
It is apparent that modifications and improvements can be made to the new
pin, without leaving the scope of the claimed invention.
The table reproduced hereinafter by way of example gives the characteristic
measurements of some pins of the type illustrated in FIGS. 1, 2 and 3.
The numerical symbols used for identifying the various pins indicate the
ratio of the length in millimeters of the first element 1 to the length in
millimeters of the second element 7.
TABLE
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Models and Dimensions
7/17 10/20 14/24
Total &
Diameter
Total &
Diameter
Total &
Diameter
partial
at points
partial
at points
partial
at points
PIN ELEMENTS AND heights
indicated
heights
indicated
heights
indicated
NOMENCLATURE OF PARTS
mm mm mm mm mm mm
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1st ELEMENT (1) 7.0 10.0 14.0
Upper part (4) 3.0 3.0 3.0
Safety ring (stop) (5)
0.3 0.3 0.3
point of support of 2nd outer element
3.3 3.3 3.3
point of support at outer bone
3.5 3.5 3.5
upper point of outer taper
3.2 3.2 3.2
Outer taper 2.7 2.7 2.7
upper 3.2 3.2 3.2
lower 3.0 3.0 3.0
Inner taper 3.0 3.0 3.0
upper 1.9 1.9 1.9
lower 1.6 1.6 1.6
Central part (3) 1.0 4.0 8.0
outer 3.0 3.0 3.0
inner 1.6 1.6 1.6
Lower part (2) 3.0 3.0 3.0
Outer 3.0 3.0 3.0
Inner taper (threaded or not)
3.0 3.0 3.0
upper 1.6 1.6 1.6
lower 0.8 0.8 0.8
"Nascent" taper 3.0 3.0 3.0
outer upper 3.0 3.0 3.0
outer lower 3.8 3.8 3.8
inner upper and lower 1.6 1.6 1.6
2nd ELEMENT (7) 17.2 20.2 24.2
Frusto-conical head (13)
7.0 7.0 7.0
upper 3.0 3.0 3.0
lower 3.3 3.3 3.3
Irregularly concave neck (11-12)
3.0 3.0 3.0
upper 2 2 2
lower 3.3 3.3 3.3
Body
Upper part (10) 7.2 10.2 14.2
Taper 3.0 3.0 3.0
upper 1.9 1.9 1.9
lower 1.6 1.6 1.6
Central cylindrical part (9)
1.0 1.6 4.0 1.6 8.0 1.6
Lower part (threaded or not) (8)
3.2 1.6 3.2 1.6 3.2 1.6
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It is not essential for the various parts of the pin to be of circular
cross-section, in that equally good results are obtained by making the
parts with inner or outer polygonal cross-sections.
Because of the optimum dimensions both of the emerging part and of the
endo-osseous part, the applicant has found that it is possible to give the
pin, in a simple and precise manner, the most suitable inclination to
enable the prosthesis fixed thereon to be inserted perfectly between the
natural teeth, or to replace them totally, thus providing prostheses which
are perfect both from the functional and appearance aspects.
The device used by the applicant for giving the pin the required
inclination is shown in FIGS. 4, 5 and 6.
Said device consists essentially of a rectangular frame 5 which, by way of
example, has a major side of 30-35 cm on a minor side of 10-15 cm. Along
one of the major sides a slot is formed into which a goniometer 4 is
inserted in a plane perpendicular to the plane of the frame, the
goniometer having a centrally indicated zero, and arc measurements
decreasing from the outside towards the zero indicated on the two lateral
circle quarters.
Adjacent to the major side which lies opposite the side into which the
goniometer is inserted, there is disposed, aligned with the base centre of
the goniometer, a block 6 into which there is centrally inserted, and thus
aligned with the goniometer zero marking, a sheath 7 which is arranged to
receive the second pin element according to the invention, over its entire
height. The neck and element head 8 emerge from this sheath, and the head
8 can be inserted into the socket head 2 of the lever 1, by means of which
the element head can be given the required inclination by adjusting it
with reference to the graduated goniometer dial.
The element head 7 is preferably given two inclinations at 90.degree.
apart, one corresponding to inclination in the mesio-distal direction and
the other corresponding to inclination in the vestibulo-lingual direction
of the natural teeth. In this manner, it is possible to obtain best
possible mastication, phonation and appearance when the prosthesis is
fixed to the pin.
Summarising, the new universal pin for oral implantoprosthesis, comprising
an autonomous double-taper fixing system, according to the invention, has
the following characteristics, all of which represent advantageous aspects
of the invention:
a first upper taper which creates a solid point of fixing in the compact
bone, in line with the periosteum
a second lower taper which arises on fitting together the two component
parts of the pin, to create a second very solid point of fixing in the
cancellous bone. As this second taper has a maximum diameter greater than
that of the upper taper, any linear movement of the pin along its vertical
or horizontal axes or any rotation about said axes is prevented
it requires no external supports nor cementing, and constitutes an
autonomous support to which any prosthesis can be fixed
it can be constructed in a large range of sizes, including very small,
which enables it to be inserted into any point of the mandible or maxilla
it does not require reconstitution of the bone in order to become stable
it does not require special instruments for its implantation. The normal
drill together with a number of graduated spiral drill bits are sufficient
to create the holes of the necessary depth
when fitted with the appropriate prosthesis crown, the pin can support
considerable stress, even exceeding that to which a tooth is normally
subjected.
Numerous modifications can be made to the pin according to the invention,
all lying within the scope of the following claims.
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