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Патент USA US2858578

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Nov. 4, 1958
vs. MYERsoN
Filed Oct. 27. 1955
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United StatesI Patent O " fit:
Patented Nov. 4i, 1958
i ñask, thereby insuring that the trial denture will be much
I Simon Myerson, Waban, Mass.
Application October 27, 1953, Serial No. 388,494
1 Claim. (ci. 1st-_33)
more accurately reproduced in the finished product than
heretofore. Moreover, this considerable improvement in
accuracy will be accompanied by a substantial saving of
In this invention, I have provided a press for forcing
the two halves of the flask together which has a meas
uring means which may be used to determine accurately
whether or not the ñask is properly closed.
A further object and advantage of the present invention
is that it enables the technician or operator to use efû
ciently the plastic material which forms the dentures,
and to compensate for any known shrinkage or expan
sion of this material while it is being used. In my method
The present invention relates to a means for accu
rately reproducing original models or trial dentures.
In the practice of prosthetic dentistry when preparing
of preparing dentures, a trial denture is first formed
and secured to a cast and is then invested into one-half
of the flask as is ordinarily done. A melted layer of
Wax, preferably very soft, is then painted onto the land
dentures, the dentist first prepares a trial plate consist
to a thickness of between .005 and .020 of an inch. The
ing of wax or other similar components in which vari
ous teeth are set in their proper positions. When this 20 upper half of the flask is then placed in the correct
position and in Contact with the lower half,- and plaster '
trial denture has been made and fitted to the mouth of
is poured into the second half of the flask, forming a
the patient and found satisfactory to esthetics, fit and
ycomplete investment. The flask is then placed in a screw
articulation, it is then subjected to a process hereinafter
press. The screw thereof is provided with a member
more fully described in which a permanent plastic mate
25 which contacts the upper member of the flask by means
rial is substituted for the wax. .
of which the ñask members are pressed together.
The reproduction of the trial wax denture into a per
In this invention, I provide a press having means for
manent plastic denture has llong been a recognized prob
lem particularly with respect to proper articulation. In
the ordinary process of producing a denture, the trial
measuring the particular position of the pressing mem
ber when the flask is properly closed.
After noting or
dentures are attached by wax to a cast which is then 30 setting the particular reading on the measuring element
at which the two halves of the flask are held firmly to
placed in one-half of a container known as a flask, and
after this portion of the investment has set, the top sur
gether in position, the flask is removed and opened. The
face or land is painted with a film of soap or other
wax is then removed in the usual manner and the invest
ment is painted with an alginate or a type of tin foil
separating medium to the edge of the trial denture which
projects above the investment. The upper half of the 35 substitute. The denture resin is then packed in „the ordi
nary fashion into the cavity of the investment containing
flask is then secured over the first mentioned half and
‘a second section of plaster is poured into the flask cov
the teeth with more than enough material to form the
ering the trial denture. When this upper part of the
investment has hardened, the flask containing the invest
the screw is turnedto force the two halves of the ñask
The flask is closed and placed in the press and
ment, cast and trial denture is placed in warm or hot 40 together until the reading on the measuring device is
the same as it was previously. When the sections of the
Water until the wax has softened enough to be removed.
flask are forced together, the excess denture resin is forced
The two halves of the investment thereby form a cavity
out of the investment cavity into the space between the
mould already containing the artificial teeth in proper
lands formed by the application of the soft waX. This
position in which a permanent plastic material, such as
a resin of methyl methacrylate, is packed after first plac 45 space is of the same magnitude as the thickness of the
ing a thin sheet of cellophane or the like over the cast.
Ordinarily much more plastic material is placed in the
cavity than is needed. The two halves of the investment
layer of wax applied. The thickness of the space required
between the lands will depend on the flowability of the
particular resin being used, The denture is then cured
in the usual manner.
are then fitted together and the halves of the flask con
One of the important merits -of the present invention is
taining them are then forced together in a press device. 50
the preservation of thev correct articulation of the arti
As the two halves of the flask are forced together, excess
ficial teeth as established lby the dentist. If the flask
plastic material will ooze out between the two opposite
containing the denture has not been properly closed,
faces or lands of the investment. The flask is then re
the increased thickness of the denture in the area of the
moved from the press and excess plastic material is re
moved. This process, which is called trial packing, is 55 posterior teeth will be increased, resulting in what is
repeated several times until the operator believes just
enough plastic material has been removed for the flask
to completely close. Ordinarily he determines the ñask
is closed when >he can no longer ’detect plastic mate
rial being forced onto the land. This method of deter 60
mining whether the flask is properly closed is, however,
usually termed as “opening of the bite.”
These and other advantages and objects of the present
invention will be more fully understood when considered
in connection with the drawings 4in which:
Figure 1 is a plan view of a press containing a ñask.
Figure 2 is a fragmentary sectional view of the meas
uring ‘elements of Figure. 1.
inaccurate as the ñask is not necessarily completely
Figure 3 is a cross sectional view of the flask containing
closed merely because there ,is no more plastic material
an investment and denture.
being forced onto the land. In fact when trial packing,
Figure 4 is a fragmentary view of a modification of the
the two halves of the ñask do not ordinarily approxi 65
elements of Figure 2.
mate each other within .015 of an inch, as the acrylic
Referring to Figure l, there is shown a press embody
resins which are used to form the denture tend not to
ing my invention in which an .accurate and full closure of
ñow through gaps of such narrow dimensions. vThe pres
ent invention overcomes these difliculties by providing
the ñask may beachieved ruring the processing of the
forming a denture may readily and properly close the
flat, fixed to a frame 2. The frame 2 is provided with two
a method and equipment by means of which a technician 70 denture. The press is provided with a base 1 preferably
upwardly extending opposite legs 3 and 4 and a trans
verse span 5. The span 5 has acentrally located threaded
The denture resin in a flowable state is then packed over
the teeth and surrounding cavity in the investment.
Enough material is pressed into position to insure that
hole 6 extending perpendicularly through it. This hole
6 may be provided at its >upper end with a concentric
hardened steel bearing plate 7.
when the lflask is closed there will be more than enough
resin to occupy the denture cavity. The flask is then
Through this hole is
threaded a crew -8 which is free to be moved .up -and
down. At the lower end of this screw Ais secured Va freely
closed and any excess resin will be squeezed out in a
thin ribbon between the lands lof the two parts of the in
vestment, which because of the coating of soft wax
prises an inner barrel 10 and an outer barrel 11, said
there during the forming of this investment are
barrel 11 having an outwardly extending circular base 10 placed
apart between .O05 and .020 of an inch. When
12. Suitably secured to this base is a plate 13 of hardened
is thus forced into a closed position in the press,
steel. The upper end of the screw is provided with a
the operator can be certain that the flask is properly
head 14 having ya hole through which >a bar or lever 15
closed if he turns the screw down to a point at which the
is secured by a set screw 16. Instead of the rigid lever
19 comes into contact with the locknut 22 when the
herein illustrated, a torque wrench lever capable of `being 15 locknut
22 is in contact with the bearing plate 7. This
set to exert a pre-determined force may be employed.
is the same position established by the original setting.
A cylinder 17 having a central threaded «aperture
`If the operator can rotate the nut 19 he will know the
through it is fitted onto the screw 8 in a position at the
llask is still open. By means of the micrometer cylinder
upper end of the screw. This cylinder, although it is
threaded on the screw 8, has sufliciently tight a fit so 20 17 and nut 19, he can determine to what extent it is
open and make correction accordingly. When the flask
that it may not readily change its position relative to the
closed, the denture is cured and then removed from
screw 8 unless intentionally turned. Normally it will
the investment; any excess plastic material in the form
turn with the screw 8. In order to facilitate the moving
of a ribbon may then readily be removed.
of this cylinder when desired, a marginal section 18 near
In the modification .as illustrated in Figure 4, the
the top of the side wall may be knurled. Also fitted on 25
screw 41 is threaded through the bridge member 42
the screw is a nut 19 which is threaded to lit onto the
corresponding respectively to the screw S and the bridge
screw 8. At the upper end of this nut 19 is an annular
member 5 of Figure l. Secured to the bridge member
upwardly extending peripheral flange 20 which forms an
42 is a bracket 43 supporting yan indicator device having
inner recess 21 at the center of the nut. The upper edge
scale member 44 and an indicator 45, pivoted at 46.
25 of this llange is beveled inwardly towards the outer 30 aThe
indicator has one end positioned to point to the scale
face of the cylinder 17.
49 and the other end adapted to contact the
The recess 21 has a sufliciently wide diameter as to
lower lsurface of the nut 47 whereby the longitudinal
permit the lower end of the cylinder 17 to fit within it as
movement' of the nut 47 may readily be registered 'on
the nut 19 and cylinder 17 are screwed towards each
the scale Imember 44.l
movable press element generally designated 9 which Acom
Alternatively, the indicator 45 may be used as an actu
yOn the surface of the cylinder 17 is provided calibra
ator for a microswitch, which may be connected to a
tions comprising a series of horizontal parallel lines each
light circuit which will signal the` closing of the flask.
at an equal distance apart, preferably J/10 of an inch
Although I have illustrated my invention using screw
apart. A vertical line divides these horizontal lines in
equal sections. «On the edge 25 of the nut 19 is provided 40 pressure means because this type of press is most common
ly used, it is obvious that the pressing member may be
a series of twenty-five vertical equi-distant lines. -If the
operated `by a lever, air, or hydraulic pressure. Other
screw 8 has ten threads to the inch, each calibration on
modifications may be made without departing from this
nut 19 will indicate a relative change in the positions be
Having now described my invention, I claim:
tween cylinder 17 and nut 19 of .004 of an inch. There
may also be positioned on the screw 8 a case hardened
A press for closing a dental flask comprising a base, a
locknut 22.
bridge member arching over and supported from said
base, said bridge member having a threaded hole fthere
through, a screw threaded through said hole and extend
ing downwardly toward -said base, a plate supportedion
çIn the operation of this press after the trial denture 50
has been placed in `a flask 23 and with au investment 52
surrounding it, in the manner briefly mentioned above,
with a layer of soft wax 53 separating the opposite lands 50
the lower end of the screw for closing a flask supported
54 of the investment, the flask is then placed upon the
on the base, a nut threaded on the screw above the bridge
base 1 and the screw is turned down until the platey 13
member and having a recess formed on its upper sur
comes into contact with the top of the flask 23. The
face, a cylinder threaded on the screw above the 4nut and
operator then tightens the screw so that the edges of the
adapted to move in and out of the recess when the nut
two parts «of the flask meet firmly as shown at 49, Figure
and cylinder are moved relative to one another on the
1. To properly position this flask each time, the base
screw, said nut and cylinder each being movable on the
1 of the press m-ay be provided with a series of upwardly
extending pins 24 which may be used to center the flask
screw, ‘and calibrations formed on the adjacent portions
of the nut and the cylinder indicating relative positions
at lall times. Having closed the flask firmly, the operator
then turns the locknut 22 until it comes into contact with 60 of the nut and cylinder and the condition of the flask.
the hardened bearing plate 7. He then screws the nut
References Cited in the ñle of this patent
19 downward until it contacts the locknut 22. He may
take the reading at this point, or he may rotate the cylin
der 17 downward until it reaches a point at which the
Schleicher __________ __ Aug. 1, 1922
horizontal calibration marked “zero” on the cylinder 17
registers with the “zero” on the upper edge of the cali 65
brated nut 19. This establishes the position at which
the flask was closed. The screw 8 is then loosened and
the flask is removed and opened. The wax forming the
trial denture and the soft wax which was placed on the
lower portion of the investment before the upper part of 70
the investment was formed in then removed by boiling
Laserson '_ ___________ __ Jan. 19, 1954
Myerson ____________ __ Sept. 4, 1956
Sweden ______________ __ Apr. 1, 1909
Germany __________ __ May 29, 1926
France ______________ __ July 1, 1953
water or warm water. If boiling water is used, the wax
may be removed in about four minutes, after which any
remaining traces of wax are cleaned out by flushing.
Angell ______________ __ Jan. 2,
Roelofs ______________ __ July 2,
Mandel ______________ __ June 1,
Nelson et al. ________ __ Sept .19,
Zahn ______________ __ Dec. 13,
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