Implant for securing a denture

An implant is disclosed for securing a base to be anchored in a jaw bone and formed by two substantially cylindrical hollow sleeves open on both their ends, and an also hollow portion of a pin. The other portion of pin projecting beyond the base forms a column intended for supporting a denture. The outer surfaces of the sleeves are provided with grooves which are distributed over the circumference. At the side remote from the column, the grooves do not extend up to the respective end face of the sleeve, so that at these locations the grooves shallow out by end faces which are capable of transmitting axial pressures occurring in an implant inserted in a jaw. The grooves also contribute to a uniform circumferential distribution of forces which are to be transmitted in a direction transverse to the column axis. With the sleeves open also on the column side, only little bone material over growth is needed for covering the sleeves.

FIELD AND BACKGROUND OF THE INVENTION 
The invention relates, in general, to an implant and, more particularly, an 
implant for securing a denture to a jaw bone of the type having a base to 
be inserted into the bone and at least one column for supporting the 
denture with the base including at least one substantially 
hollow-cylindrical part which is open at a side remote from the column. 
Swiss Pat. No. 604674 discloses a jaw implant comprising a sleeve-like base 
having a substantially circular cylindrical wall and a front wall closing 
one end of the sleeve. At this front wall, the base is connected to a 
column, while on its other end, the base is open. Circumferentially 
distributed bores are provided in the cylindrical wall and in the 
transition zone between this wall and the front wall. A rib extends 
helically on the outer surface of the cylindrical wall. 
Swiss Pat. No. 618870 and the corresponding U.S. Pat. No. 4,180,910 
disclose jaw implants having a base of two or three sleeve-like, 
substantially regular cylindrical parts, and a column which is connected 
by one end to the base and projects to its other end intended for 
supporting a denture, beyond the hollow-cylindrical base parts. The 
hollow, circularly-cylindrical base parts are entirely open on their ends 
remote from the column, but have front walls on their other ends. The 
cylindrical and front walls of the sleeve-like base parts are provided 
with bores having a diameter which is substantially smaller than the 
inside diameter of the sleeve-like base parts. 
If an implant in accordance with one of the aforecited three references is 
inserted in a jaw, considerable forces must be transmitted, for example, 
during biting. Forces or force components both in the longitudinal 
direction of the column and transverse thereto may occur. Particularly, 
the forces acting transversely to the column may produce very high local 
loads capable of causing and developing resporption of the bone material. 
This happens, especially, in instances where the implant base comprises a 
single sleeve-like part or where the forces act on two or three 
sleeve-like parts of an implant base in a plane passing substantially 
through the axes of the two, or of all of the base parts. 
Implants of the above-mentioned kind are inserted into the jaw so deeply 
that even the front wall of the hollow-cylindrical base part or parts is 
embedded in the bone and comes to lie slightly below the initial bone 
surface. To make such an insertion possible, a hole is milled into the 
bone for each of the hollow-cylindrical base parts, the hole has a deep 
portion in the form of an annular gap for receiving the wall of the hollow 
cylinder, and a shallow, fully cylindrical portion for receiving the front 
wall thereof. Upon inserting the implant, the bone grows, in, over the 
front wall or walls again so that eventually only the column projects from 
the bone. 
A rather large amount of bone material must thus be removed in the shallow 
areas where the holes receive the front walls of the bases. This, of 
course, is undesirable, especially with an implant to be inserted into the 
upper jaw. That is, in the upper jaw, the corticalis, that is, the layer 
of relatively solid bone material, is thin as compared to the corticalis 
of the lower jaw. Consequently, with holes as described above made in the 
upper jaw, the implant is held in place by the porous spongiosa alone. 
That is why it is frequently impossible to obtain a satisfactory anchoring 
in the upper jaw. 
SUMMARY OF THE INVENTION 
The invention is primarily directed to an implant in which the forces to be 
transmitted are distributed as far as possible uniformly, even if the 
occurring forces are crosswise of the longitudinal axis of the column. 
Further, the design of the implant is to allow a stable and permanent 
anchoring even in a bone having a relative thin corticalis. 
In accordance with the invention, this is obtained by providing an implant 
of the above mentioned kind, wherein the cylindrical wall of the 
substantially hollow cylindrical part is provided with recesses and/or 
elevations which extend or are arranged along stright lines parallel to 
the longitudinal axis of the column. 
Particularly advantageous developments of the invention are characterized 
in that the recesses and/or elevations are provided on the outer 
cylindrical surface of the wall, characterized in that at least ten 
grooves are provided which are distributed over the circumference of the 
hollow-cylindrical part and form the recess, characterized in that the 
recesses are formed by grooves which open by one of their ends into the 
end face remote from the column of the hollow-cylindrical part and are 
limited on their other end by the end faces, characterized in that 
considered in a cross-section perpendicular to the longitudinal direction 
of the column, the recesses as well as the elevations therebetween, and 
the transition between the recesses and the elevations, are smoothly 
rounded and characterized in that the recess augment the respective 
cylindrical suface area by at least 50 percent, as compared to a truly 
cylindrical surface area. 
The invention further relates to an implant in accordance with the 
hollow-cylindrical parts completely open even on their ends turned to the 
column. 
Advantageous developments of the implant include an arrangement in which a 
substantial circularly-cylindrical part is aligned with the column, and 
further characterized in that the base includes only parts which are 
substantially circularly cylindrical, and have their axes of rotational 
symmetry extending parallel to each other, and which are tangent to, or 
intersect, each other, and characterized in that all the circularly 
cylindrical parts included in the base are hollow and open on their ends 
remote from the column. 
Thus, in accordance with the invention, there is provided an implant for 
securing a denture to a jaw bone comprising a base to be inserted into the 
bone and at least one column for supporting the denture, the base 
including at least one substantially hollow-cylindrical part open at the 
side remote from the column, said substantially hollow-cylindrical part 
having a cylindrical wall with at least one of recesses and elevations 
which extend along straight lines parallel to the longitudinal axis of the 
column. 
Accordingly, it is an object of the invention to provide an implant for 
securing a denture to a jaw bone which is simple in design, rugged in 
construction and economical to manufacture. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
is made to the accompanying drawings and descriptive matter in which 
preferred embodiments of the invention are illustrated.

DETAILED DESCRIPTION 
FIGS. 1 and 2 show an implant, generally designated 1, for securing a 
denture to a jaw or jaw bone. Implant 1 is made from a metal, such as 
titanium, and includes two sleeves 3, having substantially the shape of 
circular cylinders. Sleeves 3 are open on both their ends, so that they 
only comprise each a cylindrical wall bounded by radial end faces 3a,3b, 
without any cover or bottom. In other words, the sleeves have a circularly 
cylindrical hole of constant cross-section extending therethrough in the 
direction of the central axis or axis of rotational symmetry thereof from 
a first open end to a second open end. A substantially rotationally 
symmetrical pin 5, having its central or longitudinal axis, or axis of 
rotational symmetry, extending in parallel with, and in the same place as, 
the axis of rotational symmetry of sleeves 3 is also provided. Pin 5 is 
disposed centrally between the two sleeves 3. 
A portion 5a of pin 5 is rigidly connected to the two sleeves 3, such as by 
welding, or is made integrally therewith. In the contact area between pin 
portion 5a and sleeves 3, the cylindrical walls of the sleeves intersect 
with portion 5a, or at least fit one another snugly. End face 5b of pin 
portion 5a is flush with the respective end faces 3a of sleeve 3. The two 
sleeves 3 and pin portion 5a form together a base 7 intended to be 
anchored in a jaw bone. A portion of pin 5 projects beyond end faces 3b or 
sleeves 3 and forms a column 5c for supporting a denture. 
The outer surface of each of sleeves 3 is provided with at least ten and, 
for example, twenty grooves 3c which extend parallel to the central axes 
of sleeve 3 and pin 5 and, except for the area of contact with pin 5, are 
uniformly distributed over the circumference of the sleeves. Grooves 3c 
form recesses and, along with the lands, ribs, or ridges therebetween, 
result in a serrated cross-sectional configuration. In cross sections 
perpendicular to the sleeve axes, both grooves 3c and the ridges, as well 
as all of the transition areas, therebetween, are smoothly rounded. 
Grooves 3c open into the end faces 3a of sleeves 3, however, on their 
other ends, they do not extend up to end faces 3b. As shown in FIG. 3, 
shortly before end face 3b, grooves 3c shallow out into the outer 
cylindrical envelope by curved end faces 3h. A smooth cylindrical surface 
strip 3d is thus formed between end face 3b and ends of grooves 3c, as 
shown in FIG. 1. A number of through holes 3e is provided in sleeves 3, 
which are distributed over the cylindrical walls. The holes are formed by 
bores which have a diameter exceeding the width of grooves 3c, and thus 
partly interrupt the grooves. As compared to a smooth cylindrical surface, 
grooves 3c enlarge the outer surface area of the sleeve walls. 
The maximum outer diameters D and the lengths or heights of sleeves 3 are 
approximately equal to each other and of a magnitude of five to six 
millimeters, for example. The thickness W of the sleeve walls and thus the 
radial width of end faces 3b is at least 7% and at most 15%, for example 
about 10%, of the maximum outer diameter D. This means that the minimum 
wall thickness W is about 0.35 mm and the maximum is about 0.9 mm, and may 
be 0.5 to 0.6 mm, for example. Grooves 3c are by about 0.1 to 1. mm 
shorter than sleeves 3. The depth t of grooves 3c may be 30% to 70%, 
preferably 40 to 60%, of the wall thickness W, thus about 0.1 to 0.3 mm. 
Shape and dimensions of the grooves are generally provided so as to 
increase the outer surface area of the sleeve all by 50%, for example, as 
compared to an apertured smooth surface without grooves. 
Pin portion 5a is hollow, and the circularly cylindrical cavity 5d extends 
from pin end face 5b up to the level of sleeve end faces 3b. Pin portion 
5a is thus also designed as a sleeve which, however, is open only on its 
end remote from column 5c. The wall of pin portion 5a is also perforated, 
by bores or holes 5e. The outer diameter of pin portion 5a is the largest 
diameter of pin, which, however, is smaller than sleeve diameter D, and 
may amount to 2.5 to 3.5 mm, for example. 
In the proximity of sleeve end face 3b, column 5c may be provided with a 
neck 5f smoothly merging into the adjacent portions of pin 5. The free end 
portion of column 5c tapers conically toward the end. 
FIGS. 4, 5 and 6, illustrate a portion of an upper jaw bone 9. In an upper 
jaw bone, the relatively compact and stable corticalis 9a forms a rather 
thin boundary zone. The interior of the bone is a relatively porous 
spongiosa 9b, the transition between these two structures of the bone 
being more or less continuous. In FIGS. 5, 6 and 7, the corticalis is 
indicated by stippling, and the spongiosa as a coarse grain. 
To insert an implant 1 into an upper jaw, initially the soft tissues (not 
shown) are removed as far as necessary, and the upper jaw bone 9 is 
exposed. Then, first, a full-diameter bore 9c is milled in bone 9, having 
a diameter corresponding to that of pin portion 5a which will later be 
received therein. Temporarily, a gage plug is inserted in bore 9c. Then, 
with the aid of this plug, two annular grooves 9d are drilled or milled 
into the bone, in which sleeves 3 will be received. In surgery, such 
annular grooves 9d are frequently termed trephined or trapan bores. The 
inner diameter of annular grooves 9d is approximately equal to the inner 
diameter of sleeves 3. The outer diameter of annular grooves 9d is 
approximately equal to the outer diameter D of the sleeves, and preferably 
smaller by the depth t of grooves 3c, so that to introduce the base, 
sleeve 3 must be forced in and the bone material penetrates into grooves 
3c already at the insertion of the implant. The depth of annular grooves 
9d is dimensioned so as to embed sleeves 3 in bone 9 completely but to 
have the sleeve portions and grooves 3c adjacent end faces 3b still 
located in the corticalis 9a, as particularly clearly shown in FIG. 5. 
Consequently, at the time the implant is inserted into a bone 9, bone studs 
9e are still present which penetrate and fill out the cavity of sleeve 3 
and, preferably, even protrude some therefrom. Upon inserting implant 1, 
the bone material grows through holes 3e, 5e and also over the annular end 
faces 3b of the sleeves. Further, the bone material grows into grooves 3c 
except that it has been forced therein already during the insertion. After 
the regeneration and growth of the bone, base 7 is completely embedded in 
and penetrated by the bone material, as shown in FIGS. 6 and 7. To cover 
sleeves 3, relatively little further growth of the bone material is 
sufficient, since only end faces 3b are to be overgrown. Therefore, base 7 
of the implant is completely covered by the bone material within a 
relatively short time after inserting the implant, except for pin portion 
5a connected to column 5c. The soft tissues (not shown in FIGS. 4 to 7) 
surrounding the bone also regenerate and grow into neck 5t. Then, a 
denture 11 such as a bridge, can be secured to column 5c. 
After bone 9 is, so to speak, grown into base 7, the curved end faces 3h of 
grooves 3c are embedded in the corticalis. These end faces contribute to 
an effective transmission of forces acting in the longitudinal direction 
of column 5c, to the bone, since they bear against the corticalis which, 
as mentioned above, is more compact and stable than the spongiosa. 
Furthermore, grooves 3c are very important to the transmission of forces 
acting on column 5c transversely. FIG. 8 is intended to illustrate how a 
force P acting crosswise of the axis of symmetry of column 5c is 
transmitted from bone 9 to a sleeve 3 after the bone is grown into grooves 
3c as explained above. Force P is assumed to act in a direction 
perpendicular to the axis of rotational symmetry of sleeve 3, or parallel 
to this direction. In the left half of FIG. 1, the serrated circumference 
of sleeve 3 is shown. Even at a location which is remotest from the 
diameter 15, the flanks of the respective ribs form faces which are not 
parallel to the direction of force P and form therewith angles between 
about 45.degree. and 135.degree.. This makes sure that forces are still 
transmitted from the bone to sleeve 3 and vice versa even at locations 
which are remotest from diameter 15. The force P, to be transmitted, is 
split into components which are distributed as indicated by vector arrows 
17. In this way, the force P to be transmitted is distributed over a large 
portion of the circumference of sleeve 3 relatively uniformly. The faces 
bounding holes 3e, 5e also contribute to this transmission of forces of 
course. This results in a uniform local distribution of forces and loading 
of the bone material. 
With the outer surface of the sleeve being a smooth cylindrical surface, 
the distribution of the force components would be such as indicated in the 
right hand half of FIG. 8 by arrows 19. The sleeve locations remote from 
diameter 15 would remain substantially ineffective in the transmission of 
a force P. 
The implant shown in FIG. 9 includes a substantially hollow-cylinder 
sleeves 23 which are open on both ends and similar in design to sleeves 3, 
particularly also provided with grooves 23c corresponding to grooves 3c, 
and with through holes 23d. Between the two inner sleeves 23, a longer pin 
25 is provided having its portion 25a rigidly connected to the two 
adjacent sleeves 23 and forming therewith a base 27 which can be anchored 
in a jaw. The axes of the sleeves and of pin 25 lie in a common plane. Pin 
portion 25a has approximately the same diameter as sleeves 23 and is also 
designed as a hollow cylinder which is open on its end flush with the 
respective ends of the sleeves. The cylindrical wall of pin portion 25a is 
provided with through holes 25e. The end portion projecting beyond sleeves 
23 of pin 25 forms a column 23c for supporting a denture. 
The implant 31 shown in FIG. 10 includes two hollow-cylindrical sleeves 33 
which are open on both their ends and are provided with grooves 33c 
corresponding to grooves 3c. The cylindrical walls of sleeves 33 are 
provided with apertures 33e in the form of slots which extend 
substantially in planes perpendicular to the central axis of the sleeves. 
A pin 35 is provided having its portion 35a rigidly connected to sleeves 
33 by webs 39, with the axes of sleeves 33 and pin 35 being parallel to 
one another and extending in a common plane. Sleeves 33, pin portion 35c, 
and webs 39 form together a base 37 to be anchored in a jaw bone. Pin 
portion 35a is hollow and its cylindrical wall is provided with through 
holes 35e in the form of slots extending crosswise of the longitudinal 
axis of the pin. Webs 39 are provided each with at least one circular 
through hole 39e. The portion protruding beyond base 37 of pin 35 forms a 
column 35c for supporting a denture. 
The implant 41 shown in FIG. 11 includes two hollow-cylindrical sleeves 43 
which are open on both their ends and have end faces 43a, 43b, grooves 43c 
and circular holes 43e, and a pin 45 comprising a hollow portion 45a which 
is provided with circular holes 45e and connected to sleeves 43 by webs 49 
having a circular hole 49e. Base 47 of implant 41 thus includes two 
sleeves, one pin portion, and two webs in the same way as base 37 of 
implant 31. However, it differs from the latter particularly in that the 
height of webs 49 is smaller than the height of length of sleeves 43. Webs 
49 extend from end faces 43b of sleeves 43 only to about half the height 
of the sleeves. End face 45b of pin portion 45a is flush with the web 
edges which extend about at the middle of the sleeves. The portion 
projecting beyond base 47 of pin 45 again forms a column 45c for 
supporting a denture. 
The implant 51 shown in FIG. 12 includes two hollow-cylindrical sleeves 53 
which are open on both their ends. Like in sleeves 3, the cylindrical 
walls are provided in grooves 53c and circular holes 53e. Two pins 55 are 
provided, and their portions 55a form together with the two sleeves 33 the 
base 67 of the implant. The axes of rotational symmetry of sleeves 53 and 
pins 55 are parallel to each other and extend in a common plane. The two 
sleeves 53 are disposed between the two pins 55 and the connections 
therebetween are rigid. Pin portions 55a are cylindrical and hollow and 
provided with grooves 55c which are the same design and extension as 
grooves 53c. The cylindrical walls of pin portions 55 are provided with 
circular through holes 55e. The pin portions projecting beyond base 57 
form columns 55d for anchoring a denture. 
The implant 61 shown in FIG. 13 includes two pins 65 having their lower 
portions, as viewed in FIG. 13, designed as hollow-cylindrical sleeves 63 
which are downwardly open. Sleeves 63 along with a rigid connecting web 69 
form a base 67 to be anchored in a jaw bone. The pin portions shown above 
web 69 in FIG. 13 form columns 65c for supporting a denture. The axes of 
rotational symmetry of the two pins 65 are parallel to each other and lie 
in the same plane, while web 69 is slightly bent out of this plane. The 
implant is thus slightly arcuate as viewed in the direction of the pin 
axes. The outer surface of each of the sleeves is provided with grooves 
63c distributed over the circumference. The grooves extend from the end 
face 63a of the sleeve up to about the level of the upper edge (FIG. 13) 
of web 69 where they terminate in a shallowing out curved end face. The 
sleeves are provided with circular through holes 63e and the web with 
circular through holes 69e. 
The implant 71 in FIGS. 14 and 15 comprises a stepped, substantially 
rotational symmetrical pin in one piece. The thicker portion shown below 
in FIG. 14 is formed by a substantially hollow-cylindrical sleeve 73 and 
serves as a base to be anchored in a jaw. The remaining portion of the pin 
forms the column 75 for supporting a denture. A preferably rounded 
shoulder is provided between sleeve 73 and column 75. On its side remote 
from column 75, sleeve 73 is open, on its other end the sleeve is closed 
by column 75 and the mentioned shoulder. The outside surface of the sleeve 
wall is provided with circumferentially distributed grooves 73c. The 
grooves extend parallel to the axis of rotational symmetry of implant 71, 
and from the radial, annular end face 73a of sleeve 73 to locations not 
quite adjacent the mentioned shoulder, where they terminate in curved 
shallowing out end faces. The cylindrical wall of sleeve 73 is provided 
with through holes 73e, i.e., bores, with further holes being provided in 
the zone of the mentioned shoulder. Column 75 is designed with a blind, 
tapped hole. 
While implants 1,21,31,51 and 61 are suitable primarily for securing tooth 
bridges, implant 71 may also be used for securing individual artifical 
teeth. 
The implants may be modified in different ways. 
For example, in implants 1,21,31,41 and 51, the sleeves and columns may be 
displaced relative to each other to have the parallel axes extending in a 
curved surface. 
Implants 1,21,31 and 41 may have their pin portions 5a,25a,35a,45a 
belonging to the base provided with grooves similar to grooves 3c. 
Further, the outer surfaces of the sleeves provided with longitudinal 
grooves may be provided with additional grooves extending circularly or 
helically around the sleeves. Such additional grooves would cross with the 
longitudinal ones and interrupt the ridges or elevations therebetween. 
Another possibility is to provide the inner surface of the sleeves with 
grooves extending parallel to the axis of rotational symmetry of the 
sleeve. 
The implant can be inserted both in the upper and lower jaw. Thus, in 
accordance with the invention there is provided an implant for securing a 
denture 11 to a jaw bone 9 comprising a base 7 to be inserted into the 
bone and at least one column 5c for supporting the denture 11, with the 
base 7 including at least one substantially hollow-cylindrical part 3 
which is open at the side remote from the column 5c, characterized in that 
the cylindrical wall of the substantially hollow-cylindrical part 3 is 
provided with recesses 3c or elevations, or both, which extend or are 
arranged along straight lines parallel to the longitudinal axis of the 
column. 
The implant may be further characterized in that the recesses 3c and/or 
elevations are provided on the outer cylindrical surface of the wall. 
The implant may be even further characterized in that at least ten grooves 
3c are provided which are distributed over the circumference of the 
hollow-cylindrical part 3 and form the recesses. 
The implant may be still even further characterized in that the recesses 
are formed by grooves 3c which open by one of their ends into the end face 
3a remote from the column of the hollow-cylindrical part 3 and are limited 
on their other ends by end faces 3h. 
The implant is preferably characterized in that considered in a 
cross-section perpendicular to the longitudinal direction of the column, 
the recesses 3c as well as the elevations therebetween, and the 
transitions between the recesses 3c and the elevations, are smoothly 
rounded. 
In accordance with a preferred embodiment, the implant is still 
characterized in that the recesses 3c augment the respective cylindrical 
surface area by at least 50%, as compared to a truly cylindrical surface 
area. 
An implant, in accordance with another embodiment of the invention for 
securing a denture 11 to a jaw bone 9, comprises a base 7 to be inserted 
in the jaw bone and at least one column 5c for supporting the denture 11, 
with the base 7 including at least two substantially hollow-cylindrical 
parts 3 which are axially parallel and are open on their sides remote from 
the column 5c, characterized in that said hollow-cylindrical parts 3 are 
completely open even on their ends turned to the column 5c. The alternate 
embodiment may be further characterized in that the base 7 includes a 
substantially circularly-cylindrical part 5a which is aligned with the 
column 5c. The alternatie embodiment may be even further characterized in 
that the base 7 includes only parts 3, 5a which are substantially 
circularly cylindrical, and have their axes of rotational symmetry 
extending parallel to each other, and which are tangent to, or intersect, 
each other. The alternate embodiment may be even still further 
characterized in that all the circularly cylindrical parts 3, 5a included 
in the base 7 are hollow and open on their ends from the column 5c. 
Finally, in accordance with the invention, there is provided a method of 
securing a denture to a jaw bone, with the base of an implant comprising a 
column 4 supporting the denture being inserted into the jaw bone, and the 
base of the implant including at least two substantially circularly 
cylindrical, hollow sleeves which are open on both their ends, and with an 
annular groove being milled into the mone for each of the sleeves in such 
a manner that a bone stud is formed extending through the sleeve and 
projecting therefrom. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.