Note: Descriptions are shown in the official language in which they were submitted.
BFN 6650 ~1-
Background of the Invention
This invention relates to the construction and
attachment of partial artificial dentures, and particularly
to the structure of such attachments and the process of
manufacturing them.
The most common form of partial artificial
denture, sometimes referred to as partial plate, involves the
use of wire-like clasps or the like which engage around one
or more of the wearers remaining teeth, and which hold the
denture in position. Considerable difficulty is experienced
with such arrangements breaking, bending and losing their
holding force, or otherwise changing the predetermined
position of the partial denture to the point where it is
uncomfortable and possibly irritates the wearer, and/or is
subjected to unusual stresses which results in breakage,
either of the attachment parts or in some cases the partial
denture itself. Furthermore, existing attachment
arrangements are somewhat limited in their application, and
particu~arly have not been found suitable for partial
dentures which might be required on only one side of the
patient's mouth.
Furthermore, existing retention arrangements involve
silver solder or similar connections which tend to break, and
which are particularly sensitive to flexing which may occur
during usage of the denture, yet it is desirable that the
attachment of the denture to the existing teeth be somewhat
flexible, so that stresses are not transferred to the
anchoring existing teeth, thereby compounding the dental
problem of the wearerO
Various attachment devices of this nature are
disclosed in U. S. Patents Nos. 1,299,364; 1,367,885;
1,423,288; 1,696,422; 1,805,264; 3,309,771; 3,535,787; and
3,990,150. Of these, the most significant is No. 1,299,364
which shows a partial dental bridge having wire or hard metal
anchors embedded therein, and extending in the form of
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BF~N -2-
a vertically orien-ted loop with both of its ends fixed to the
bridge. An abutment is attached to a na-tural tooth, and a
keeper in the form of a hard metal plate is soldered to the
abutment.
The keeper is formed with grooves in its side and
top, to receive the anchor loop, which is arranged to snap
around the generally xectangular extent (in cross-section)
of the groove. Thus any pivoting of the bridge along an
axis transverse to the attachment must overcome the stiff-
ness of the hard wire at the base ends of the loop; and any
rotational motion of the loop around the groove must over-
come (and tend to weaken) the clasping action of the wire
loop against the sides of the groove in tha keeper. Thus,
stresses due to flexing lengthwise of the jaw tend to mis-
lS align -the attachment loop and bend or wor]c the wire, while
torque tending to rotate the loop will tend to transmit into
the keeper.
a rv e i - ~3 Ir ~er ~ion
The present invention provides a novel attachment
?O arrangement whereby a partial denture, either single or
double sided, may be attached to abutting teeth of the wearer
by constructing for the abutting teeth crowns which are built
in conventional manner, but which are provided with a special
anchor member. These crowns are attached to a natural tooth
in the conventional way, for example by cementing~ The
partial denture is provided with a clip which is included
in the denture, and which easily by firmly clasps to the
anchor member formed ln the crown of the abutting tooth.
The anchor/clip attachment i9 appropriately relieved once
it is constructed for the particular patient, such that
the partial denture has adequate flexibility in use, without
transmitting much stress to the crown. ~lso, the anchor/
clip interface is essentially that of mating cylindrical
surfaces, and the clip will tend to rotate on the anchor
surface rather than transmit torque to the crown.
Thus, the denture can seat upon the y~n of the wearer
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sF&N 6650 ~3~
as it is intended and designed to do without transferring
stress through the anchor/clip attachment to the abutting
or anchoring teeth. Furthermore, the present invention
provides a novel process o~ constructing a par-tial denture
S to include such attachment, whereby -the anchor member and
the clip oE the denture are precisely aligned to assure an
accurate fit of the denture each time it is placed in the
wearer 1 5 mouth.
Ln particular, the novel process and the extra
coronal attachment mechanism provided by this invention
includes an anchor member ~hich is cast into, or as part of,
the crown being built for the abutting or attaching tooih.
Thus, as the crowns are ~uilt on the master cast of the
mouth, the anchor member (or a mold fox it), preferably in
the form of a grooved cylinder, is precisely located by
means of a suitable mandrel~ and incorporated into the
pattern for the crown, a~ter which the crown is cast in the
usual way. The crown with the integral anchor member is
then seated on the master c~st and the partial denture is
built up from this point. The region on the cast corres-
ponding to that re~ion of the patient's mouth where the
attachment will ~e located is appropriately blocked off, for
example by constructing a waxed area of appropriate size and
shape,using blocks or parts provided for this purpose. Then
~5 construction o~ the paxkial denture proceeds in conventional
fashion, incorporating the attachment clip, or A socket for
mounting the clip.
The framework of the partial denture is thus
located with respect to the attachment, the clips being
attached to the anchor members during this time, and the
appropriate sockets (where used) for receiving the clips on
the frame of the partial denture being appropriately align-
ed, such that after the partial denture is constructed,
removal of the clips from the anchors on the crowns, and
attachment of the clips to the completed partial denture
in the case of replaceable clips, results in a finished
attachment ready for fitting of the mouth of the wearer.
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BF~N 6650 ^-4-
The attachment between the clip and the anchor member is
preferably ln the form of a hvrse-shoe shaped clip which
snaps around a relieved or undercut section of the cylin-
drlcal anchor member, such that the clip can snap endwise,
from above or below as the case may be, onto and around the
groo~e in the anchor me~ber, thereby locating the partial
denture both len~t.hwise and crosswise. A surface of the
anchor memher farthest ~xom the gum preferably is Cllt away
slightly, to relieve the connection between the clip and
the anchor member to the extent of permitting a slight
rocking motion of the base of the clip, where it is attach-
ed to the denture, in a direction generally transverse to
the jaw line and the axis o~ the cylindri.cal anchor member.
This allows for flexure or the clip, especially in a
downward-rearward direction, on the anchor mel~ber without
subjecting the anchor member, and -thus the crown on which
it is formed, to stress as force is exerted against the
partial d.enture at a location remote, usually .re~rward~
from the attachment point.
In one form the rem~vable clips are provided with
a threaded shank in their base, and these shanks extend
through an appropriate hole formed in the socket in the
frame o~ the partial denture, and may be held in place by
suitable locking nuts or the like, as a result of which the
clips can be easily and quickly replaced if -the clips should
be bent or broken at any time. In another embodiment the
clip is fitted into, bu~ removable from, the socket which is
cast into the denture rame.
The primary object of the present invention there-
Eore is to provide a novel attachment for a partial denture,
commonly referred to as an extra coronal attachment, and a
process of constructin~ the same, whereby the partial
denture is easily attached and detached by means of clips
to one or more anchor members formed on crowns which are
construc-ted on the abutting or anchoring teeth of the
wearer and attached thereto in conventional fashion, and
wherein the clip/anchor connection essen~ially isolates the
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BF~N 6650 -5
crowns from flexure or torsional forces due to movements of
the denture; to provide such an attachment which is adapt-
able for attaching partial dentures either to one or both
sides of the wearer's mouth; to provide such an attachment
and process which is quickly constructed using conventional
tools and techniques, with the excepti.on of a few parts that
are readily available in kit form to the dental laboratory.
Other objects and advantages will be apparen-t
from the following descrlption, the accompanying drawings
and the appended claims.
Brief Description of the Drawings
Fig. 1 is a perspective view showing the align-
ment of the anchor me~ber of the attachment to the mold
from which a cro~n is made,
Fig. 2 is an enlarged perspective vlew showing
the anchor member waxed up to the crown mold;
Fig. 3 illustrates the crown, having been molded
and with the anchor rnember now an integral part, positioned
on the master cast, with th~ attachment clip for the denture
located above the anchor member;
Fig. 4 is a view showing the manner in which the
clip and socket are positioned on the master cast for proper
alignment in the construction of the resulting denture;
Fig. S is a perspective view showi~g the skeleton
or frame of the partial denture, with the clips positioned
on the anchor members of the crowns, and illustrating the
manner in which the clips are attached to the frame prior
to construction of the artificia:L dentures thereon;
Fig. 6 is a perspective view of one of the crowns
with the integral anchor member showing the relief to the
anchor member which allows flexing of the completed denture
in use;
Fig. 7 illustrates the application of the inven-
tion to a bar type prosthesis;
Fig. 8 shows another form of socket pattern;
Fig. 9 shows the pattern of Fig. 8 located over
the anchor member on a master cast;
BF~N 6550 -6-
Fig, 10 shows the manner of using the socket
par.tern in ~axing up;
Fig. 11 shows the anchor attachment pattern of
this form;
Fig. 12 shows the anchor attachment pattern in
place for completing the internal configuration of the
socket;
Fiq. 13 is a view of the attachment clip which is
applied to the finished socket; and
Fig. 14 is a cross-sectional view o~ the modified
clip on the anchor memberO
Description of the Preferred Embodiment
~ eferring to Figs. 1 and 2, there is shown a
master cast 10 o a patient's lower jaw, from which the
molars have been removed, and on which the bicus~ids are
being repaired by conventional crowns ~shown as patterns 12)
constructed in the conventional way, to be cemented in place
over the properly formed base of the natural tooth,
indicated by the dotted outline 13~ The outline is shown
only on the left side for purposes of simplification;
however, it will be undexstood that a crown is constructed
for two of thèse anchoxing or abutting teeth to form the
necessary support for the artificial denture on both sides
of the wearer's mouth. The waxed up pattern 12 of the crown
is formed in the conventional way on the member 13, which is
a part of the master cast, and as part o forming the crown
pattern a cylindrical metal anchor member 15 is located in a
precise position, and at a precise anyle with respect to the
master cast, by holdiny the anchor member 15 in a mandrel 17.
This angle places the longitudinal centerline of the anchor
member in a position e~tending rearward and downward over
the jaw lineO
The anchor member is then a-ttached to the crown
pattern 12 by an appropriate shaped mass of wax or the like,
shown generally in Fig. 2 by the referen~e numeral 18. It
should be noted in Fig. 1 that the end of the anchor member
around which the temporary holdiny wax i5 applied includes
~F&N 6550 -7-
one or more cylindrical grooves or the like, indicated
generally at 19, and the other end of the anchor member is
provided with a preclsely undercut cylindrical groove 20.
The groove 20 is engaged by a horseshoe shape retainer 22
at the end oE mandrel 17, thereby locating the anchor
member exactly in position, and at the correct angle,
duriny this operation. The crown pattern 12 with the
anchor member attached, ls then removed from the master
cast and the ac-tual crown is cast, using known techniques.
]0 If the anchor member 15 is of a material compatible with
the crown, the anchor member can be cast into the crown.
Alternatively, the member 15 can be a suitable pattern, as
of polyprop~lene or an acrylic (e.g. Lucite), and the
entire crown and anchor cast together.
The crown itself is shown :in Fig. 3 at 25, with
the anchor member now integral with the crown, projecting
at the proper angle therefrom, and with the cylindrical
groove or anchor surface 20 exposed. This crown/anchor
memher combination is there~ore adapted to provide the
precige attachment point for the partial denture, and the
attachment to the anchor member is made by a horseshoe
shaped clip 28, shown separated from the anchor member in
Fig. 3, and apart from the partial denture.
The clip includes a pair of downwardly extending
arms 29 which ara shaped to surround the anchor me~ber,
fitting within the groove 20 and tightly engaging the
surfaces of that groove. The base section 30 of the clip is
generally rectangular in cross-section, in the preferred
embodiment, and extending upwardly from it is a threaded
attachment stud 32. The clip is snapped onto the anchor
member with the crown 25 in the master cast, and the region
surrounding the attachment is then prepared for blocking up,
as part of the subse~uent construction of the partial den-
tureO
For this purpose a small box or socket 35 is
provided having an apertuxe 36 which is sized to fit closely
around the shank 32 of the clip. The box is placed around
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BF&N 6650 -8-
the cllp and the anchor member, with the shank ex-tending
through the hole 35, and the interior of the box i5 ~illed
with wax. The sicles of the bo~ are then cut, for example by
forming dovetailed or grooved slots therein, and the lower
edges of the box are trimmed as necessary to fit to the
reyion of the gum line of the master cast. The purpose of
this is that the boY~ (one on each side) eventually becomes
cast into the ~ramework of the partial denture, thus pro~
viding an accura-te socket to engage the denture with the
clip 28 when finally assembled.
The dovetails are indicated generally at 38 in
the sides of the box 35, and their purpose is to provide a
secure joint hetween the box and the framework of the
denture which is next formed. This is done in conven-tional
fashion, by making a mold of the master cast, and withdraw-
iny the mold there~rom, taking the boxes 35 into the mold.
In some instances it is desirable to provide small balls of
sticky wax on the outex surfaces of the boxes, to assure
that they remove cleanly from the master cast into the mold.
The framework for the denture is then mo:Lded, in conven
tional manner, using the thus formed mold with the boxes
therein, and the cast framework thereby incorporates the
boxes.
Such framework is shown by the general reference
numeral 40 in Fig. 5. The boxes trimmed and incorporated
as sockets into the framework, are shown in alignment with
the clips 2~. Each clip, however, is illus~rated xemoved
from the framework r but aligned therewith as shown by the
dot-dash center lines, and attached to the anchor member on
the crowns 25 and 25a which are, at this time, fitted onto
the master cast. Above the denture framework 40 there are
shown the retainer nuts 42 whi~h are provided to thread onto
the stud.s 32 of the clips, thereby retainin~ the clips to
the framework, securely seated such that they will not twist
or mo~e out oF alignment with the framework.
Next, the artificial dentures are bullt on the
frame 40, in known manner, preferably leaving the frame
BF&N 6650 -9-
at~ached to the master cast for the best alignmen-t. Then,
once the partial denture is comple-ted and removed, the ends
of the anchor members are provided wi~h a tapered cut across
their upper portion, as shown in Fig. 6, this cut prefer-
ably extending at approximately fort~-five degrees to the
longitudinal center line of the cylindrical members, and
being deep enough that a portion of the top of the slot 20
is removed. This cut is illustrated in ~ig. 6 by the gener-
al reference numeral 45. The purpose is to permit a small
amount of rucking action of the clip 28 within -the tops of
the slots when the wearer of the partial denture exerts
pressure ayainst the molars, rearward of the attachment
connection. This enables sufficient flexure o~ the denture
that it will~seat securely on the gums, but will not trans-
mit appreciable twistiny force through the attachment
connection to the abuttiny crowns 25 and 25a which form the
ultimate support of the denture to the mouth of the wearer.
Furthermore, the cylindrical surface interface
between the clip and the anchor surface (groove 20) allows
for rotational movement in the attachment. This is desir-
able since the wearer ~ight bite hard on one side, thereby
producing a torque at the attachment points. The accom-
modation of rotation at the attachment interface effectively
isolates the crowns from this torque.
Fig. 7 shows a modification of the invention
applied to a bar~type prosthesis, for example where a
partial denture is to be constructed to fill a space
between two teeth on the same side of the mouth. Here a
first crown 50 and a second ~rown 52 are constructed in
conventional fashion by building them up on the master cast
and then casting the crowns from the wax. The anchor
member 55 is provided as a bar of suitable length having
gripping grooves, or the like (not shown) near its ends,
and which is waxed up the crown pat~erns on the cast, and
then form~d as an integral part of both crowns, joining
them and bridging the space between them. The anchor
member is also provided with a cylindrical recess 56 sized
8~3
BF&N 6650 -10-
to receive the clip of the partial denture in the same
manner as previou~ly described. I'hus, the framework and
the attachment fox this partial denture is built in the
same way, and is clipped to the anchor bar 55, in the same
fashion as previously described.
Figs. 8-14 illustrate another embodiment of the
i.nvention. The parts shown in Fig. 8, Fig. 11 and Fig. 13
can be molded of a suitable plastic material such as poly-
propylene, and can be provided in a kit along with a plastic
anchor-forming cylinder 15. The block shown in Fig. 8 has
a generally rectangular outer dimensi.on as shown at 60, and
it is provided with a part cylinclrical passage 6~ into which
is molded a rib or ring 64. The block 60 is adapted to
snap onto the anchor formed integrally with the crown, with
the rib 64 entering the anchor surface or groove 20, as
shown generally in Flgs. 9 and 10. In Fig. 9 the part is
in position to be snapped onto the anchor, and in Flg. 10
the part is shown snapped into position with wax applied at
65 around the base of the part 60.
~o The standard procedure for building up the bridge-
work then is followed, and the paxt 60 acts to mold an
appropriate rectangular socket into the bridgework, as
shown genexally in Fig. 12. At this point the part 60 may be
disposed of r and a part as shown in Fig. 11 is used to fit
the bridgework to the master cast and the anchors formed on
the crowns as shown in Fig. 12~
Referring to ~ig. 11, the part 70 is similar in
appearance to the part 60, having an internal cylindrical
opening 72 and a rib 74, however, the top o this paxt is
relieved at the upper edges, as indicated at 75, and
beneath each relieved upper edge there is a slot 77. Also,
the transverse outer dimension oE the part 70 is slightly
undersized with respect to the part 60, so that the part 70
slips tightly into the sockets in the denture.
~ith the part 70 itted into the sockets, or
alternatively fitted onto the anchors, a quantity of a
self-curiny polymeric mat~rial is applied between the
BF&N 6650 -11-
socket and the part 70, and the denture is pressed tightly
onto the parts 70 while in place on the anchors. As the
material cures, it forms a pair of opposed ridges along the
upper interior sides of the socket, these being shown gen-
e.rally at 78 in Fig. 14.
With the denture removed frorn the master cast,
after the ma-terial ls cured, the parts 70 are then carefully
pried from the sockets, and the final clip 80, as shown in
Fig. 13, is snappad into the socket. This clip has the
same longitudinal cylindrical opening 82 and i.nternal rib
84. ~t is provided with a head 85 shaped generally to the
configuration of the top of the part 70, and recesses 87
provided to engage over the ribs 78 in the socket, locking
the clip in place. The outer w~lls of the clip 80 are
curved at both upper and lower sides, providing sufficient
relief that the head 85 can snap into place, and also pro-
viding clearance as shown at 88 in Fig. 14. This allows
the lower sides of the clip to flex sufficient].y in the
socket as the denture is applied and removed from the
anchors during normal use.
While the process and forms of apparatus herein
described constitute preferred embodiments of this invention,
it is to be understood that the invention is not limited to
this precisa process and forms of apparatus, and that
changes may be made therein without departing from the
scope of the invention.
