Note: Descriptions are shown in the official language in which they were submitted.
1 The present invention relates to soldering and firing
tables for use in soldering a prosthetic crown and firing a cer-
amic material coated on the surface of the prosthetic crown in
the process for preparing prosthetic teeth.
BREIF DESCRIPTION OF THE DRA~INGS
, .
Figs. 1, 2 and 3 are perspective views sho~ing embodi-
ments of the supporting plate of the present invention which can
~e used for either a soldering ta~le or a firing table; in which
Fig~ 1 shows a horseshoe-shaped supporting plate;
Fig, 2 shows an ellipsoidal supporting plate; and
Fig. 3 show~ an arcuate supporting plate.
FigO 4 is a perspective view showing em~odiments of the
supporting pin of the present invention which can be used with
either a soldering table or a firing table; in which
Fig~ 4Ca~ shows a straight supporting pin;
Fig, 4~b~ shows a supporting pin having a flange in the
intermediate portion; and
Fig. 4~c~ is a supporting pin which is eccentric in the
intermediate portion.
Fig. 5 is a perspective view showing a receiving stand
which can he used as an auxiliary member for either a soldering
ta~le or a firing ta~le.
Fig, 6 is a diagram illustrating the state in which a
prosthetic cro~n is soldered by using any one of th~ supporting
plates shown in Figs. 1, 2 and 3.
Fig. 7 is a view showing the section taken along the
line X-X in Fig, 6, in which the state of use of the receiving
stand shown in Fig. 5 is indicated by an ima~inary line~
Fig~ 8 is a diagram illustrating the state in which a
prosthetic crown is suppor-ted on an investment compound according
to the conventional soldering method,
1 Fig. 9 is a top plane view sho~ing anot~er embodiment
of the supporting plate that is used for a soldering table.
Fig. 10 is a side view of the supporting plate shown in
Fig. ~.
Fig. 11 is a view showing the section taken aLong the
line Y-Y in Fig. 9.
Fig. 12 is a diagram illustrating the state in ~hich a
prosthetic crown is soldered by using t~e supporting plate shown
in Fig. q~
Fig. 13 is a view showing the section taken along the
line Z-Z in Fig. 12~
Fig. 14 is an enlarged development showing the state in
which a prosthetic crown is fired by using any one of the support-
ing plates shown in Figs~ 1, 2 and 3~
Fig. 15 is an enlarged development showing the state in
which a prosthetic crown is fired hy using the conventional firing
ta~le.
DESCRIPTION OF THE PRIOR ART
. . _ _ _ _ _ . .,
In the prior art during the process for preparing pros-
thetic teeth for soldering, a dental prosthetic crown, such as a
single crown or a partial denture crown (hereinafter referred to
as "prosthetic crown"), which is tentatively fired for the purpose
of positioning by an unhardened bulk of a dental investment com-
pound (hereinafter refer~ed to as "investment"2, is pressed to
such an extend that the neck portion of the tooth is slightly
embedded~ the investment is naturally hardened, the cro~n is placed
in an electric furnace and the temperature is gradually elevated
from the normal temperature to about 800C over a period of 20 to
30 mînutes to effect soldering.
3Q According to this method, since the investmen-t is in the
form of a relatively large bulk, if heating is performed rapidly,
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.. . .. . . ..... ... . ... ....
1 cracks are formed or breakage is caused, and, there-Fore, heating
should be conducted gradually and a long time is required for com-
pletion of the soldering operation. During this period, the pros-
thetic cro~n is oxidized by gases genera-ted from the investment
which inhibit the flow of the soldering material and a proper
soldering effect cannot be o~tained. Furthermore, deterioration
or discoloration of porcelain is caused by long periods of heating
and, in the bulk of the investment which has a large mass, crack-
ing or deformation is caused by expansion or shrinkage of the
inve~tment due to heating with the resul-t that the dimensional
and spatial precision of the soldered prosthetic cro~m is reduced.
During the formation of prosthetic teeth by means of
fusion-bonding a ceramic material to a prosthetic crown~ firing
is carred out several times at high temperature, For example~
there is adopted a method including the following firing steps:
Firstly, an opaque ceramic material for hiding a metal-
lic color is coated and baked at a temperature between about 600
and ~60C for 6 minutes.
Secondly, a ceramic material of a color of t~e tooth
crown is coated and ~aked at a temperature between about 600 and
930C for 6 minutes.
Thirdly, firing is carrîed out at a temperature between
about 600 and 960C for 6 minutes to correct the shrinkage of the
ceramic material.
Four~hly, firing is carried out at a temperature between
about 800 and 960C for ~ minutes for the purpose of glazing.
In a firing -table heretofore used for firing, as shown
in Fig 15, the lower end of a supporting pin 20 is tapered and is
inserted in a taper hole 22 of a supporting plate 21 to effect
fixation of the supporting pin 20. Accordingly, the position of
~ ll'7~
1 the top end of the supporting pin is fixed and cannot ~e adjusted
according to the size of a prosthetic crown~ This prior art
firing ta~le can ~e used conveniently in the case of a ~hort pros-
thetic crown such as a single crown or a one-loose-tooth three-
teeth bridge, but in the case of a ~ridge including many connected
teeth, several supporting pins are required and the top ends of
some of them do not reach through the internal cavity to the
furthest portion of the prosthetic cro~n 8. Rather, a space S is
formed ~etween the pin and the solid portion of the crown and,
therefore, the prosthetic crown 8 is not completely supported as
shown in Fig. 15. If firing is carried out in this condition, the
non-supported portions of the prosthetic cro~n tend to hang down
and become deformed during long periods of heating at high temp
eratures,
Moreover~ since the thermal expansion coefficient of the
material constituting the firing table is not taken into account
in the conventional firing table and the thermal expansion coeffi-
cient of the prosthetic crown is different from that of the firing
t~ble~ the prosthetic crown is cracked or deformed. Therefore,
although very high precision is required, it has hitherto ~een very
difficul-t to attain a high degree of precision in preparing pros-
thetic teeth.
SU~ARY OF THE INVENTION
It is, therefore, a primary o~ject of the present inven~
tion to provide soldering and firing tables for prosthetic crowns
which can support a prosthetic crown in a preferred state during
the soldering and firing step and which yield prosthetic teeth
which are excellent in dimensional and spatial precision and qual-
ity~
30Another object of the present invention i~ to provide
soldering and firing table ~or prosthetic crowns which faciliate
.
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L7~
1 the preparation oE prosthetic teeth ~y shortening the operation
time which, therefore, increases the operation efficiency and
reduces the cost of prosthetic teeth.
Still another object of the present invention is to
provide a supporting table for prosthetic crowns which can be used
either as the soldering table or as .the firing table which, there-
fore, elimiates the necessity of installing a soldering table and
a firing table independently~
More specifically, in accordance with one aspect of the
present invention, there is provided a soldering tabIe for pros-
thetic crowns which comprises a supporting plate and a plurality
of supporting pins having the top ends thereof to be capped with
a prosthetic erown to be soldered, wherein the positions or heights
o~ the supporting pins are adjusted according to the prosthetie
crown ~nd the supporting pins are inserted in this state into holes
formed on the supporting plate, and the supporting plate and
supporting pins are fixed by an investment compound.
In aecordance with another aspect of the present inven-
tion~ there is provided a soldering ta~le for prosthetic erowns
~hich comprises a supporting plate having a groove ~ormed on the
top surfaee thereof and sup~orting pins having the top ends to ~e
eapped with a prosthetie crown to ~e soldered and which are im-
planted in an inves~ment eompound filled in the groove of the
supporting plate.
In aceordance with still another aspect of the present
invention, there is provided a firing ta~le for prosthetic crowns
which eomprises a supporting plate and a plurality of supporting
pins having the top ends thereof to ~e capped with a prosthetic
crown to ~e fired, wherein the positions or heights of the support-
ing pins are adjusted according to the prosthe-tic erown and the
supporting pins are inserted in this state into holes formed on
the supporting plate, and the supporting plate and supporting pins
are fixed by an investment compound.
In accordance ~ith a further aspect of the present in-
vention there is provided a soldering or firing ta~le having the
a~ove-mentioned structure in which the supporting plate and
supporting pins are composed of a metal or ceramic material having
a thermal expansion coefficient equal or close to that of a metal
of the prosthetic crown.
In accordance ~ith a stilI further aspect of the present
invention~ there is provided a soldering or firing table having
- the a~ove-mentioned structure in which three kinds of supporting
pins, that is, straight pins, pins having a flange in the inter-
mediate portion thereof and pins which are eccentric in the inter-
mediate portion thereof, are selected depending on the prosthetic
cro~n to be soldered or fired and used as the supporting pins.
In accordance with a still further aspect of the'present
in~ention~ there is provided a soldering or firing tahle having
the a~ove--mentioned structure in ~hich the investment compound is
filled in a concave portion formed on the top ~ace of a receiving
st~nd arr~nged as an auxiliary member, wherein the supporting
plate is placed,on the filled investment compound to cause the
investment compound to adhere closely to the ~ack surface of the
supporting plate; the supporting pins are implanted in the invest-
ment compound through the holes of the supporting plate and tne
receiving stand is dismounted after the investment com~ound has
been hardened.
DETAILED DESCRIPTION OF THE INVENTION
The presenk invention provides soldering and ~iring
ta~les which can suppork a prosthetîc crown in a preferred state
~7g9~
1 during the soldering or firing step in the process for manufact-
uring prosthetic teeth and which yields prosthetic teeth which
are excellent in dimensional and spatial precision and quality.
The soldering table of the pres~nt invention using the
~upporting plates shown in Figs, 1, 2 and 3 will no~ be descri~ed
in detail with reference to the accompanying drawings.
As to the shape of the supporting plate which can be
used for both the soldering table and the firing ta~le described
hereinafter, there can be a horseshoe shape shown in Fig~ l; an
ellipsoidal shape shawn in Fig, 2; or an arcuate shape shown in
Fig. 3; but the shape of the supporting plate is not particularly
critical and other shapes may be adopted~
A plurality of small holes 2 and long holes 3 are formed
on the surface of the supporting plate 1, and a plurality of legs
4 which extend past the back surface are formed such that the
suppoxting plate 1 can be used when placed on an appropriate oper-
ation stand or when it is placed on a receiving stand 6 as
described hereinafter.
The lo~er ends of supporting p:ins 5 sho~l in Fig. 4 are
inserted into the small holes 2 and long holes 3 so that the top
ends of the pins 5 are fitted with a prosthetic cro~n 8 to support
the crown 8 thereon. Appropriate small holes are chosen and used
according to the size or configuration of the prosthetic crown 8.
Since the supporting pins 5 can freely move in the long holes 3,
the long holes 3 are used for a prosthetic crown 8 for which del-
icate adjustment is required~ Three kinds of supporting pins 5;
that is~ straight pins shown in Fig~ 4~a); pins having a flange
5' in the intermediate portion thereof as shown in Fig, 4(b); and
pins haying an eccentric part 5" in the intermediate portion
thereof f as shown in Fig~ 4(cl; are supplied which can ~e approp-
riately selected and used.
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1 For example, in the case of straight supporting pins the height
of the top and of the pin can be freely adjusted in the vertical
direction; in the case of the supporting pin having a ~lange 5',
the height of the top end can be adjusted by causing the flange
5' to impinge against the top surface of the supporting plate;
and in the case of the supporting pin having an eccentric part 5",
the eccentric part 5' impinges against the top surface of the
supporting plate to determine the height, and horizontal adjust
ment of the position according to dentition can ~e attained by
turning the supporting pin.
The top ends of these supporting pins 5 ma~ ~e snarpened
by dou~le~face shaving, whereby the supporting pins 5 can easily
be implanted in an investment compound 7 filled in the inner cav-
ity o~ the prosthetic crown 8 at the soldering step and after
hardening of the investment compound 7~ the supporting pins 5 can
be prevented from turning. Furthermore, the top ends of the
supporting pins 5 may be sharpened in a conical form 50 that the
top ends reach the furthest sold portion of the prosthetic crown
8. Moreover~ the portions of the suppor~ing pins 5 near the lo~er
ends thereof can be squarely cut or partially notched, or have one
side thereof shaved of~ so that these portions have a non-cicular
sect~on and the supporting pins are prevented from turnîng when
they are fixed by the investment compound 7.
Several supporting pins of each o~ the above~mentioned
three kinds can be prepared and held in reserve so that appropri-
ate pins can be selected and used at the appropriate time in the
present invention.
The supporting plates 1 and supporting pins 5 are pre~
pared from a metal or ceramic material having a thermal expansion
coefficient equal or close to that of the prosthetic crown 8.
~7~
1 As the metal for the prosthetic cro~n~ a nickel~chromium alloy is
often used as the metal for the pros-thetic crown and the thermal
expansion coefficient of this alloy i~ a~out 12 x 10 6 to
13 x 10 6/oC. If the supporting plates 1 and supporting pins 5
are prepared from this alloy, a soldering table having the same
thermal expansion coeffiçient as that of the prosthetic crown can
be obtained. In the case of ceramic supporting plates and .
supporting pins, two or more ceramic materi.als can be appropriately
compounded so that a thermal expansion coefficient equal to or
close to that of the prosthetic crown can be obtained. 0~ course,
a practically satisfactory ~oldering table may be formed of a
single ceramic material if the thermal expansion coefficient of
the ceramic material is close to that of the metal of the pros
thetic crown. For example, the following ceramic materials, may
be used: alumina (A1203~ having a thermal expansion coefficient
of 7 x 1~ 6/oC, forsterite (2~gO.SiO2~ having a thermal expansion
coefficient of 10 x 1~ 6/oC, titanium ox.ide ~Tio2i having a ther-
mal expansion coefficient of 11 x 10 6/oC and magnesium oxide
(MgOl ha~ing a thermal expansion coefficient o~ 14 x 10 6/C.
~ mixture formed by kneading an lnorganic po~der ~ith a
binder and a hardening agent i5 ordinarily used as the investment
compound 7. A heat-resistant rapid-hardening cement can also ~e
used as the investment compound.
The soldering method using the above~mentioned soldering
ta~le will now be described.
An embodiment using the horseshoe-shaped supporting
plate 1 sho~n in Fig, 1 and the supportlng pins 5 is first de
scribed, Appropriate supporting pins are selected from the above-
mentioned three kinds of the supporting pins 5 according to the
configuration of the inner cavity of a prosthetic crown 8 to be
soldered, The prosthetic cro~n is temporarily soldered according
~7~
1 to the conventional me-thod and the lo~er ends of the supporting
pins 5 are inserted into small holes 2 and long holes 3 of the
supporting plate 1 which is placed on an appropriate operation
stand, The prosthetic cro~n 8 is f~tted on the top ends of the
supporting pins, The positions of the supporting pins 5 are
adjusted so that the top ends of the supporting pins impinge
against the furthest solid portion of the prosthetic crown 8. The
supporting plate is turned over and the inve~tment compound 7 i~
applied to the back surface thereof in between the pro;ecting
1~ portions of the lower ends o~ the supporting pins 5. The assembl~
is allo~ed to stand in this state for a while, and when the invest-
ment compound 7 is considerably hardened to such an extent that
the supporting pins 5 are not mova~le, the supporting plate 1 is
turned over again to the original position and the investment
compound 7 is applied to ~he base portions of the supporting pins
5 and on the surface of the supporting plate 1 so that the invest~
ment compound 7 surrounds the flanges 5' or eccentric parts 5" of
the supporting pins 5. After the investment compound 7 has been
allo~ed to harden, the supporting plate 1 and supporting pins 5
are firmly fixed,
The inner cavity o~ the prosthetic crown 8 i5 then filled
~ith the investment compound 7 and the prosthetic cro~n 8 is ~itted
on the top ends of the supporting pins 5 as ~efore~
The investment compound 7 is allowed to harden naturally.
Thus, the prosthetic cro~n 8 is integrally secured by the support-
ing plate 1 and supporting pins 5. This state is illustrated i~
Fig, 6.
According to another embodiment of the soldering method,
a receiving stand 6 shown in Fig. S is used~ In this em~odiment,
as shown in Fig. 7, the investment compound 7 is filled in a con-
cave portion 6' formed on the top surface of the receiving stand 6 t
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~: L79~4
1 and the supporting plate 1 is placed on the concave portion 6' so
that the investment compound 7 adheres closely to the back sur-
face of the supporting plate 1~ The lo~er ends of the supporting
pins are shallowly inserted into the investment compound 7 through
the small holes 2 and long holes 3 of the supporting plate 1
according to the layout tentatively determined according to the
configuration of the prosthetic crown ~, The prosthetic crown 8
is fitted on the top ends of the supporting pins 5 and the posi-
tions of the supporting pins S are delicately adiusted, In this
state, the prosthetic cro~n 8 is pressed down, whereby the top
ends of the respective supporting pins 5 are caused to impinge
against the furthest solid portion of the prosthetic cro~n ~ and
the lo~er ends of the supporting pins 5 are embedded into the
investment compound.7. Two or three supporting pins are stopped
at the point where the flanges 5' or eccentric parts 5" impinge
on the top surface of the supporting plate 1, The investment com-
pound 7 is allowed to harden in this cinfiguration and tne hase
portions of the supporting pins are then coated with the invest~
ment compound 7. After this coating of investment compaund 7
has hardened the inner cavity of the prosthetic cro~n 8 is filled
with the investment compound 7 in the same manner as described
above~ The prosthetic crown 8 is then fitted on the top ends of
the supporting pins 5 as before and after the investment compound
has hardened the receiving stand 6 is removed.
If the receiving stand 6 is used, it is not necess~ry
to turn the supporting plate 1 over and fix the supporting pins by
coating khe base portions of the supporting pins ~ith investment
compound, Therefore, the overall operation is faciliated.
Ordinarily, the investment compound 7 is naturally hard-
ened ~ith~n about 20 to 30 minutes, after ~hich the lo~er ends of
., .
L~3~
1 the suppor~ing pins 5, the flanges 5' and eccentric parts 5" actas turn-prevention means, and the double-face-shaved portions of
the top ends of the supporting pins 1 exert a turn-preventlon
effect in the inner cavity of the prosthetic crown 8. The support-
ing plate 1, supporting pins 5 and prosthetic crown 8 are thus
integrated to form a tightly connected structure in ~hich the
respective members are not moved even if certain external forces
are applied thereto,
In this state, the connected assem~ly is placed in an
electric furnace heated at a~out 820C wherein the prosthetic
crown 8reaches a temperature suita~le for soldering within about
30 to 6Q seconds~ A molten gold solder 10 i5 applied by a blow
pipe to the top ~nd of a soldering tool 9 comprising a long nickle-
chromium line and an appropriate handle attached thereto as shown
in Fig, 6. When a small droplet of the gold solder l~`whiah is
applied to the top end of the soldering tool ~ is transferred to
a seam of the prosthetic crown, that is, the portion to be soldered
the gold solder 10 flows smoothly to effect soldering~ In this
manner, seams are soldered in succession. After completion of
2~ -the soldering operation~ the assembly is taken out from the elec-
tric furnace and cooled, The prosthetic crown 8 is then separated
~rom the supporting pins 5 and a soldered prosthetic crown is
obtained. The investment compound is then removed ~rom the
supporting plate 1 and the supporting pins 5 ~hich may be used
again in another cycle.
According to the present invention, the heating time for
the soldering operation is remarka~ly shortened as compared with
the heating time required in the conventional method. Therefore,
oxidation of the metallic portion or deterioration or discolor-
ation of the ceramic portion is considerably reduced, and a beau-
tiful soldered finish is o~tained. Furthermore, the amount of
- . .. .. .. .. .. .. .
~79~8^~
1 expensive gold solder used can he reduced to a minimum, resulting
in a great economical advantage. Moreover, the prosthetic crown
can be positioned precisely and easily by using the supporting
plate and supporting pins; and the thermal expansion coe~ficient
of these members is adjusted so tnat cracking or deformation due
to expansion or shrinkage by heating or cooling does not occur.
Therefore, prosthetic teeth which are of excellent quality can ~e
obtained. Furthermore, the time required for the series of oper-
ation can be remarkably shortened as compared ~ith the time re
quired in the conventional method. Accordingly, the production
yield can ~e efficiently increased according to the present inven-
tion. Thus, various advantages can be attained ~y the soldering
table of the present invention~
For convenience sake, the soldering table descri~ed
herein~efore will be referred to as "soldering ta~le A" ~erein-
after.
Another embodiment of the soldering table, including a
supporting plate, having a structure shown in Fig, 9 ~hereinafter
referred to as "soldering table B"~ will now be described with
re~erence to the accompanying drawings.
Fig. ~ sho~s a horseshoe-shaped supporting plate 11~
However~ the shape of the supporting plate 11 is not particularly
critical and the supporting plate 11 may have an ellipsoidal shape
an arcuate shape or any other optional shape. In the same manner
as descri~ed hereinbefore, t~e supporting plate 11 of this em~odi-
ment is formed of a metal or ceramic material having a thermal
expansion coefficient equal to or close to that of the metal of
the prosthetic crown,
The above-mentioned supporting pins 5 shown in Fig, 4 are
also used for supporting plate 11. A groove 12 is formed on the
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~7~4
1 top surface of the suppoxting plate 11 so that an investment
compound 7 can be Eilled in the groove 12 for impl.anting the
supporting pins. As sho~n in Fig. 11, this groove 12 includes
upper and lo~er steps, and the upper step has a ~road width and
the lo~er step has a narrow ~idth A shelf 13 is formed in the
portion connecting the upper and lower steps to each other so
that flanges 5' or eccentric parts 5l of the supporting pins 5
impinge against this shelf 13. The edge of the upper step of the
groove 12 is slightly expanded in~ardly to form a return 14 for
preventing the investment compound from rising~ At least one air
esPapehole 15 for removing air when the investment compound is ;-
filled in the bottom portion of the groove is provided, Such
return 1~ or air escape hole 15 need not ~e formed in the case of
a certain groove~ Furthermore~ appropriate legs 16 may be formed
on the back surface of the supporting plate 11 ~o that the support-
ing plate 11 can ~e conveniently placed and used on an operation
stand The configuration of the groove 12 is not limited to the
two-stepped configuration illustrated in the drawings, An angu-
lar groove or a U-shaped groove can be adopted if an appropriate
usage is adopted~ alothough, in tho~e cases, the flanges 5' or -
eccentric parts 5" of the supporting pins will not impinge against
the groove~ Moreover, a supporting plate having no legs can ~e
used.
The method of using this soldering table B for the sold~
ering operation is not fundamentally different from the method
described hereinbefore with respect to the soldering table A~
Ho~ever~ because the structure of tha supporting plate of the sold-
ering table B is different from the structure of the supporting
plate of the soldering table Ar the method adopted for the solder-
ing ta~le B is different from the method adopted for the solderin~
14
~L~794~
1 table A in the following point.
In case of the soldering table B, the groove 12 formedon the top surface of the supporting plate 11 is filled with the
investment compound and the lower ends of the supporting pins 5
are shallowly implanted in the investment compound 7 in a pattern
similiar to the pa~tern predetermined by to the prosthetic crown
8. The prosthetic crown 8 is fitted over the top ends of the
supporting pins 5 and the position~ of the suppoxting pins which
are not properly aligned are adjusted. The prosthetic crow~ 8 is
pressed down whereby the top ends of all the supporting pins are
caused to impinge against the furthest solid portion of the pros-
thetic crown 8, A~.ong these supporting pins 5, two or three of
them are positioned such that the flanges 5' or eccentric parts
5" impinge on the shelf 13 of the supporting plate 11.
If spaces are formed in the investment compound by intru-
sion of the flanges or eccentric parts of the supporting pins it
is possible to fill these spaces, because the investment compound
is still in a soft and pasty state, by acljusting the position of
the pins or by pressing down on the prosthetic crown. If these
2~ spaces do not easily fill up then the investment compound can be
lightl~ pres~ed ~y the finger tip or a fresh investment compound
can ~e applied additionally.
After the positions of the supporting pins have been
determined the assem~ly is allo~ed to stand allowing the invest-
ment compound 7 to harden~ The prosthetic crown i5 than removed.
and the inner cavity of the prosthetic crown is filled with the
investment compound and once again fitted over the top ends of the
supporting pins 5. These procedures are the same as those de-
scribed herein~efore with respect to the soldering ta~le ~ and the
same effects can be attained~ The supporting state of the pros-
thetic cro~n 8 and the state of the soldering operation are shown
~7~
1 in Fig, 12 and 13.
The methad adopted for soldering table B is different
from the method adopted for table A in that for the case of sold-
ering table A, the investment compound is applied after the
supporting pins 5 are positioned, whereas in the case of solder-
-ing table B, the supporting pins 5 are implanted in the pasty
investment compound ~hich has already been applied to the sup-
porting plate 11. However, both the me-thods are similiar to each
o-ther in the a-ttainable desirable effects which are ob-tained.
1~ The firing table for prosthetic crowns according to the
present invention will IlOW be described ~7ith reference to the
accompany drawings.
~ he firing table has the same structure as that of the
above-mentioned soldering table A and includes the supporting
plates 1 shown in Figs. 1, 2 and 3 and the suppor-ting pins 5 shown
in Fig. 4. In other words~ the soldering table A can also be used
as the firing table, Accordingly, description of the structure
of the f~ring table is omitted.
The method for using the firing tahle is substantially
the same as the above-mentioned method for using the soldering
table A, In the case of the ~oldering tahle A~ the inner cavity
of the prosthetic crown 8 ~hich i5 to be 501dered is filled ~ith
the investmen-t compound and the prosthetic crown 8 is fitted on the
top ends of the supporting pins 5 to effect fixation. In case of
the firing table, the intended objec-t can be attained only by
supporting the furthest solid portion of the prosthe-tic cro~n 8
which is to be fired by the top end~ of the supporting pins 5.
Therefore~ it is not necessary to fill the inner cavlty of the
prosthetic crown 8 with the investment compound, Rather, it is
sufficient if the firing table supporting the prosthetic crown 8
which is to be fired is placed in an electric furnace and firing
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~ ~94~
1 is carried out. Other procedures are the same as those adopted
for soldexing table A Therefore~ description of these proced-
ures is omitted.
After completion of the firing operation, the invest-
ment compound fixing the supporting pins 5 to the supporting plate
1 is removed, and the supporting plate 1 and supporting pins 5
may be used again in another cycle.
When the a~ove-mentioned firing table is employed, since
the top ends of all the supporting pins 5 impinge on the furthest
1~ solid portion of the prosthetic cro~n 8 as shown in Fig 14, the
prosthetic cro~n 8 can ~e supported precisely and assuredly~ In
the conventional method ~hown in Fig. 15, the top ends of the
supporting pins do not al~ays impinge on the furthest solid portion
of the prosthetic crown and spaces S are formed with the result
thatnon-supported portion of the prosthetic cro~n tend to hang
do~n and become deformed during heating at high temperatures~
Also, undesirable results occur due to e~pansion and shrinkage
during heating and cooling In the present invention, since such
space~ S are not formed at all, the~e disadvantages obser~ed in
the conventional method do not result. Moreover, dimen~ional and
spatial precision is not degraded ~y firing. There~ore, the pre-
sent inYention can provide a firing ta~le capa~le of yielding
prosthetic teeth of e~cellent quality.
~ hile the invention has been illustrated and described
with reference to preferred embodiments thereof~ it ~ill ~e obv-
ious to those s~illed in the art that variou~ changes and modi-
ications may be made therein without departing from the scope of
the invention as defined hy the following claimsO
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