US 2457114 A
Description (OCR text may contain errors)
Dec. 28, 1948. s. AMENTA 2,457,114
PROCESS OF FORMING DENTURES FROM POLYMERIZABLE ACRYLIC MATERIALS Filed July 12, 1944 2 Sheets-Sheet l s. AMENTA 2,457,114 PROCESS OF FORMING DENTURES FROM POLYMERIZABLE ACRYLI IG MATERIALS Filed July 12, 1944 2 Sheets-Sheet 2 Dec. 28, 1948.
Inventor Patented Dec. 28, 1948 PROCESS OF FORMING DENTURES FROM POLYMERIZABLE ACRYLIC MATERIALS Sam Amenta, Chicago, 111. Application July 12, 1944, Serial No. 544,557
This invention relates to a system of processing methyl methacrylate resin for use in dentures. It is a positive system of curing methyl methacrylate resin, and is time saving, eliminating breakage of anterior and posterior porcelain teeth as I well as porosity. The system is distinguished by the fact that acrylic is constantly under control while manufacturers of acrylic resin dentures generally use bench cooling after a case has been cured.
The main object of this invention is to eliminate porosity acrylic resin dentures and prevent breakage during the manufacture of porcelain teeth set therein and thus produce a practically perfect and faultless article. With this purpose in mind deep study of the different steps has been made, to find the temperatures required and duration of each particular step, their sequence and above all the kind of material utilized with proportions and mixing.
The construction and assembling of the flask used has also been given considerable thought and is now believed to be the best possible.
The curing step has had particular attention and in all every angle and feature in connection with this method has been carefully looked into.
The temperature of the hot bath used should preferably be lowered from 212 F. to between 130 and 140 F. and held there for about half an hour to make sure that no internal changes occur. Then the flask is to be opened immediately, when the acrylic is fixed. This fact makes it possible to process a case in less than four hours.
In the accompanying drawings one embodiment of the invention is illustrated, like numerals representing like details in the different views.
Figure l is a perspective view of the model from which the actual denture is going to be made;
Figure 2 is the bottom half of a flask in longitudinal section on line 22 of Figure 3;
Figure 3 is a plan view of the bottom half of a flask shown in Figure 2;
Figure 4 is the top half of the flask in longitudinal section along line 4--4 of Figure 5;
Figure 5 is a plan view of the top half of the flask shown in Figure 4;
Figure 6 is a transverse section of the flask assembled with the model Figure 1 deposited therein upside down, and a sheet of tin foil for easy separation and plaster above and below where the flask halves meet;
Figure 7 shows a water vessel in which the flask is disposed for the last operation.
In carrying out the invention, a wax case is 2 Claims. (01. 18-55.1) I
2 preferred which is somewhat heavier than usua in order to obtain proper finishing.
The model 14 shown in Figure 1 is invested in plaster and has a convex body or bottom, the front of which is wax i5 and the rest is plaster l6 reaching to the edge I! of the wax and imbedded therein are the teeth l8. The model I4 is painted in its entirety with a separating or parting medium of soapy water preferably consisting of one part of ordinary soap powder and three parts of water, well mixed, and set with its convex portion down in the plaster 16 in the lower half I9 of the flask with a concave bottom 190. From the inner edge of the flask 19 to the edge of the teeth I8 is spread a tin foil 2! (see Figure 6) which must not touch the teeth. The tin foil, gage is best suitable for this. The upper half 20 of the flask has vents 20a and a pair of fingers 20b for engaging in corresponding apertures, recesses or seats l9b in the lower half IQ of the flask when assembled.
Over this is next poured the top plaster to incisal and occlusal of teeth whereupon the top cover is adjusted and closed very slowly and clamped and left in press 22 until final set occurs.
The next operation is now to boil out the wax I5. For this purpose the flask is carefully opened and placed in boiling water in a vessel 23 (see Figure '7) for about 5 minutes to boil out the wax. Thereupon the teeth are well cleaned with carbon tetrachloride and dipped in cold water for not more than 10 minutes in order to obviate absorption of water, and then wiped dry. All small particles are carefully removed. Then tin foil, gage is applied up to inner edge of flask using mucilage sparingly and then surface wiped with chloroform. The flask should be of room temperature 72 to F.
This temperature must be maintained in using powder (polymer) and liquid (monomer) as a resin-forming or poylmerizable acrylic compound is slow in setting. Mixed powder and liquid is kept in a covered jar and mixed until the desired heavy gum consistency is obtained of the acrylic. The same is then placed over the teeth well divided all over the case. More is added if necessary and flask closed and permitted to stand 5 to 10 minutes before the flask is placed in Warm water. To begin the curing all Cellophane must have been removed and in closing the flask pressure should be applied from front to rear slowly with the final closing in center. Any surplus material is permitted to escape from the rear of the flask.
The curing step consists in placing the clamped flask in a bath of water 23 at a temperature between 150 and 160 F. for 50 to 60 minutes, but heavy cases require longer time, up to about 100 minutes. Thereupon the flask is transferred into a similar bath of boilin water for 30 minutes. Then the flask is removed to a fixing bath with a temperature between 130 and 140 F. for another 30 minutes. This is illustrated in Figure '7.
When thereupon the flask is taken out, it must be opened immediately, without bench cooling, when the acrylic has become fixed, so that there can be no chance of distortion either by contraction or expansion.
If a knife is used for pryingthe flask open, care must be taken that it does not enter further than the edge of the flask. In case the model remains in the upper half of the flask, the latter should be tapped lightly with a metal instrument'to jar the model loose from the flasks. The casewill now be found to be perfectly cured, anterior and posterior. teeth unbroken and .neithenporosity nor shrinkage will be found.
To simplify. separation of flask, bottomof .model should 'be concave. The case must not absorb water and the tinfoil onmodel is .to be .cleaned by chloroform.
The packing must be .done with great carein order. not to distort the teeth.
The acrylicmust be. of correct consistency. and heavy before applied in .flask and all Cellophane removed.
.Before starting the curing, the case should standforb to .10 .minutes.
.The time of curing must be closely Watched and the v.fiask opened immediately afterremoval from the third or fixing bath. Bench cooling is not permitted. 7
.The following ingredients are used:
'1."The separating medium consists of about one part ordinary soap powder and three parts water, well mixed.
2. 'Acrylic, strictly speaking, is methyl methacrylate resin.
'3. The plastic composition consists-of powdered polymer, three cubic centimeters, and monomerin liquid form, one cubic centimeter.
4. In a suitable jar the polymer powder is firs deposited thru the liquid monomer and mixed well, the jar is covered and intermittent mixing\ continued until a gummy, rolling consistency of heavy dough is attained. An accelerator may be added to hasten the polymerizing and setting time It is to be understood that the invention as here-disclosed -=is not limited to the details here describedbut that-the same may be varied Widely Without departing from the spirit of the invenftion as defined bythe subjoined claims.
v1.;Iin :a process of forming dentures, in which polymerizable "acrylic materials are placed over -;ar.tificial-=teeth set in mold forming materials in ametal flask and cured, the improvement in the curingoperation comprising immersing the flask containing the said materials in a bath of water having a temperature between and F. for .fromfifty .to sixty minutes, .then in .a .bathof boiling .waterior thirty minutes, then in .afbath of .water having .a 'temperaturebetween' and 140.F. anda'fter the .jflask hasbeen'in said last named bath approximately .thirty minutes removing the .flask therefrom and immediately. removing the denturefro-m the flask.
2. ,Ihe process o'fclaim 1 whereinithepolymerizable acrylic materialis methyl methacrylate.
'RTEFERENCES CITED The following references are of :record in the file of this patent:
UNITED STATES-PATENTS Number Name Date 1,817,363 -Gibbons Aug. .4, 19.31 1,967,830 .Lemmerman July.24, 1934 1,980,483 Hill .Nov. 13, 1934 2,234,993 Vernon .Mar...18,.1941 2,358,730 Nelsonv Sept. 19, 194.4
FOREIGN 'PA'IENTS Number Country Date 484,343 Great Britain May 4, 1938