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Mechanical Amalgamation: Progress Report of Research On Dental Materials*
T HE J O U R N A L of the AM E RIC AN DENTAL ASSOCIATION Vol. 16
APRIL, 1929
N o. 4
Original Communications
MECHANICAL AMALGAMATION: PROGRESS REPORT OF RESEARCH ON DENTAL MATERIALS* By N . O. TAYLO R,f Ph. D ., W ashington, D.C. H E available data on dental amal gam alloys have shown that the alloys available to the dental pro fession vary widely in their composition and properties. Further, the properties of individual alloys were found to vary a great deal as the alloy to mercury ratio was changed and also as the meth ods of amalgamation were varied. In the past, hand mixing with a preliminary trituration in a mortar has been more or less of an elastic procedure, the total
T
■¡■Research A s s o c ia te , B u r e a u o f S ta n d a r d s . * C o o p e r a tiv e B u rea u
of
resea rch
S ta n d a r d s
by
and
th e th e
N a t io n a l A m e r ic a n
D e n t a l A s s o c ia t io n . * P u b lic a t io n
ap p roved
th e B u r e a u o f S ta n d a r d s p a rtm en t o f C om m e rce .
b y th e D i r e c t o r o f o f th e
U.
S. D e
* R e a d b e f o r e th e S e ctio n o n H is t o lo g y , P h y s io lo g y , P a t h o lo g y , B a c t e r io l o g y and C h e m is t r y
(R e s e a r c h )
at
th e
S e v e n tie th
A n n u a l S e ss io n o f th e A m e r ic a n D e n ta l A s s o c ia t io n , M in n e a p o lis , M in n ., A u g . 22,
1. per
1928.
Jour. A. D. A A p r i l , IQ 2 Q
time consumed in mixing being any where from two to ten minutes. It has been shown that excessively long trituration in the mortar or mulling in the hand led to serious shrinkage in the final product.1 W ith this fact in mind, the question of what effects are to be expected when an alloy is mechanicallv mixed with mercury seemed to offer an interesting field for research, as, in most mechanical amalgamating devices, the rapidity of agitation is increased, with a corresponding decrease in mixing time. Little information regarding mechan ical amalgamation is available, and such as is offered consists largely of indefinite claims and not of data as to perform ance. The problem is of sufficient inter est to warrant a careful study of the fundamental effects of representative types of amalgamators such as are being
583
B u rea u o f N o.
157.
S ta n d a r d s T e c h n o l o g i c P a
The Journal of the American Dental Association
584
C. A type combining centrifugal and rolling actions on samples placed in a small irregularly shaped box mounted eccentrically on a motor shaft. A mixer of each type was used in this study. They are listed as Type A, B or C,
sold to the profession from year to year. Accordingly, a study was made of three types of amalgamators and their effects on the properties of alloys as compared with hand mixed specimens mixed under definitely controlled conditions.
T able 1.— P roperties of H and M ixed A lloys *
A llo y
C o n t r a c t io n to
T ota l C hange
P ercen tag e
1st M in im u m in
in 2 4 H r .
o f F lo w
S tre n g th
in 2 4 H r .
L b . p e r S q. In .
M icr o n s p e r C m .
in M i c r o n s p e r C m .
C r u s h in g
1
— 0.5
+ 5.0
3.2
4 6 ,7 0 0
2
— 1.5
—
1.2
2.5
4 5,8 00
3
— 60.0
t
33,500
* T e s ts fB o th
m ade flo w
in
— 6 0 .0
a ccorda n ce
s a m p le s
b rok e
w it h in
F ederal
S p e c ific a t io n
N o . 356.
m ic r o m e te r .
A survey of the available mechanical according to the previous classification. The selection of variable types of devices offered as amalgamators showed them to be of three general types, as alloys for use in the study made neces sary a survey of the properties of current follow s: Three alloys were A. Those of the vibrating or shak amalgam alloys.2 ing type using a gelatin or metal capsule selected for test, as follows: T able 2.— P roperties of A lloy N o . 1, as A ffected b y V ariations in M ix in g T im e and by D if fe r e n t T ypes o f A m alg am ato rs * A m a lg a m a to r P rop erty
Type A
M ix in g T im e (S e co n d s ) 15
30
60
— 0.7 — 1.5
— 3.5
— 4 .0
A
+ 7 .0
+ 2 .7
+ 4 .0
+ 7 .0
B
+ 7.5
+ 2 .2
— 3.0
— 5.5
— 18.0
m ic r o n s p e r cm . P ercen tag e
C A
+ 2 .7
— 1.0
— 1.3
— 0.6
3.2
3 .4
5.8
5.9
7.0
o f flo w in 2 4 h o u rs C r u s h in g str e n g th ,
B C
3.3
2.5 4.5
2.5
2.7
33.7
8.7
5.2 53,500
50,000
4 2 ,6 0 0
30,800
51,900
2 4 h o u rs,
lb . p e r sq. in.
B C
A
3.2 4 5,1 00
4 5 ,9 0 0
B
4 0,7 00
4 6 ,2 0 0
56,000 4 8 ,4 0 0
C
54,200
52,8 00
53,100
* M i x e d fiv e p a r t s o f a llo y to n in e p a rts o f m e r c u r y b y w e ig h t . h a n d m ix e d , 5 :9 , f o r c o m p a r is o n .
— 2.0
120
— 1.0 + 17.0
m ic r o n s p e r cm . C h a n g e in
— 0.7 0.0
— 0.9
45 — 1.5 — 2 .4
C o n t r a c t io n to 1st m in im u m ,
— 5.5
— 5.5 — 18.0
180 — 11.0
+2
9.5
4 7 ,6 0 0
P r o p e r t ie s o f A l l o y N o . 1,
T o firs t m in im u m — 0 .5 ; in t w e n t y - f o u r h o u rs, + 5 ; flo w in
t w e n t y -f o u r h o u rs , 3.2 p e r c e n t ; c r u s h in g s tr e n g th , 4 6 ,7 0 0 p o u n d s p e r s q u a r e in ch .
and operated on an eccentric support No. 1. A first quality material whose driven by a motor. T h e re su lts o f this s u r v e y a re g iv e n B. The mortar or grinding type of 2. in a s e p a r a t e r e p o r t , “ A S u r v e y o f A m a l mixer having a metal mortar and an g a m A l l o y s ,” f o r w a r d e d to th e R e s e a r c h agitator operated by attaching a shaft C o m m is s io n o f th e A m e r ic a n D e n ta l A s s o to the usual dental handpiece. c ia tio n .
Taylor— Mechanical Amalgamation
minutes in the hand, are given in Table 1. W ith three mixers available and the three alloys mentioned above selected, the experimental work was started and the following series of tests were made: 1. Alloy No. 1 was used in each type of mixer, the proportion of alloy to mercury varying from 5:5 to 5:13 and the mixing time from fifteen seconds to three minutes. 2. Alloys Nos. 2 and 3 were tested in the shaking type of mixer (type A ).
properties were found to comply with all the requirements of Federal Specifi cation No. 356 for Dental Amalgam Alloys. No. 2. A material showing a slight shrinkage after twenty-four hours but whose percentage of flow was low and whose crushing strength was fairly high. No. 3. A very low grade alloy which showed very great shrinkage, whose flow samples crushed under the light loads used in the tests and whose crushing strength was low. T able
3.— P roperties of A llo y
N o. 1 as A ffected by A lloy an d M ercury *
A m a lg a m a to r P rop erty C o n t r a c t io n
Type
585
V ariations
P roportions
in
of
P r o p o r t i o n o f A l l o y to M e r c u r y b y W e i g h t 5 :7
5:5 0.0
5 :11 — 0.6 — 0.4
5:13 — 0.8
— 0 .4
0.0 0.0
0 .0
0.0
5 :9 t — 0 .7 0.0
0.0
— 0.3
— 1.0
+ 6 .0
+ 16.0 + 7 .9
+ 17.0
+ 6 .0
+ 12.8
+ 7 .5
+ 5 .0
+ 10.7
+ 2 .6 3.5
+ 1.8 3.7
+ 2 .8
+ 2 .5
+ 5 .5
2.8
4.2 3.6
4.6
6.1
3.2 3.3
C
3.2
2.6
2.9
4 4 ,9 0 0
4 2 ,0 0 0
51,800
str e n g th ,
A B
3.2 4 5 ,1 0 0
39,400
4 5 ,4 0 0
4 0 ,7 0 0
4 7,5 00
3.7 52,800 4 7 ,0 0 0
lb . p e r sq. in.
C
50,000
51,600
54,200
52,900
47,2 00
1st m in im u m ,
A B
m ic r o n s p e r cm . C h a n g e in
C A B
+ 8 .5
C A B
to
2 4 h o u rs , m ic r o n s p e r cm . P ercen ta g e o f flo w in 2 4 h o u rs C r u s h in g
0.0
4.2
* M i x i n g tim e, fifte e n s e c o n d s . fP r o p e r tie s
of
A llo y
N o.
1,
hand
m ix e d ,
— 0 .5 ; in t w e n t y - f o u r h o u r s , + 5 ; flo w s tr e n g th , 4 6 ,7 0 0 p o u n d s p e r s q u a r e in ch .
in
The physical properties investigated in the entire study were setting changes which indicated the contraction to the first minimum and the total change in twenty-four hours expressed in microns per centimeter, the percentage of flow in twenty-four hours, and the crushing strength. A ll tests were made in ac cordance with Federal Specification No. 356 for Dental Amalgam Alloys. The physical properties of these alloys mixed five parts by weight of alloy to nine parts of mercury, triturated one minute in a glass mortar and mulled for two
5 :9 ,
fo r
tw e n ty -fo u r
c o m p a r is o n . h ou rs,
3.2
To per
firs t
m in im u m
ce n t;
c r u s h in g
the properties and mixing times varying as in 1. It is interesting to note that no directions were given by the manu facturers of the amalgamators as to proper proportioning or mixing time. Knowing the variations in alloy proper ties produced by changing manipulatory methods, this would seem a serious omis sion, more especially so since we have not one but many different types of materials which can be used in these machines. On the other hand, manu facturers of alloys have not seen fit to outline definite treatment for their own
586
The Journal of the American Dental Association alloy to mercury ratios. These data are given in Tables 3 and 4. The data secured in testing Alloy No,. 1 indicate that: 1. Short mixing times with variable proportions of alloy to mercury give small initial contraction values followed by definite expansion, and, in some in stances, excessive expansion. 2. Longer mixing results in larger shrinkage values followed in most cases by incomplete recovery of the loss in length.
alloys in the various types of amalga mators. The net result is that a variety of mixers have been and are being used without data to prove their limitations and adaptability. It is hoped that this study will give sufficient data to show ( 1 ) the effects produced by mechanical amalgamation; ( 2 ) the necessity for further study of, and the development of directions for, the individual types of amalgamators; (3 ) the need for explicit directions for the use of each and every alloy where the manufacturers find their T able 4.— P roperties of A li .oy
1 as A ffected by A lloy and M ercu ry *
N o.
Type A
P roportions of
in
P r o p o r t i o n o f A l l o y to M e r c u r y b y W e i g h t
A m a lg a m a to r
1st m in im u m ,
B
5:5 — 2.8 — 3.8
• m ic r o n s p e r cm . C h a n g e in
C
— 3.8
P r o p e r t ie s C o n t r a c t io n to
V ariation s
5 :7 — 3.5
5 :9 t
5 :11
5:13 — 2.4
— 2.0
— 3.1
— 10.5
— 5.5
— 2.8
— 2 .4
— 5.5
— 4 .0
— 4.6
— 2.8
A
+ 6 .3
+ 6 .5
+ 4 .0
+ 4 .5
+ 6 .7
B
— 3.8
— 8.0
— 5.5
m ic r o n s p e r cm . P ercen tag e
C A
— 2.5 4.3
— 1.6 5.3
— 0.6 5.9
— 3.1 — 2.4
— 4 .2 + 6 .0
5.4
o f flo w in 2 4 h ou rs C r u s h in g
B
5.3
9.6
2 .7
4.1
24 h ou rs,
C
5.8
6.7
5.8
4 8,2 00
57,700
56,900
52,900
s tr e n g th
A B
5.2 53,500
6.1 7.8 5.5
5 3,600
52,900
4 2 ,6 0 0
54,000
53,200
lb . p e r sq. in.
C
55,700
55,900
51,900
50,500
53,000
* M i x i n g tim e, s ix ty s e c o n d s . ■("Properties o f A l l o y N o . 1, — 0 .5 ;
in
tw e n ty -fo u r
h ou rs,
hand
+ 5 ;
m ix e d ,
flo w
in
5 :9 ,
fo r
tw e n ty -fo u r
c o m p a r is o n . h ou rs,
3.2
To
firs t
m in im u m
per
ce n t;
c r u s h in g
s tr e n g th , 4 6 ,7 0 0 p o u n d s p e r s q u a r e in ch .
product adapted to mechanical amalga mation. The tests of Alloy No. 1 with Amal gamators A, B and C gave three series of data. Samples were made using five parts of alloy to nine of mercury, and the mixing time varied from fifteen sec onds to three minutes. This series shows the effect of variations in mixing time independently of other variables. These data are given in Table 2. The second and third series were run with constant mixing times of fifteen seconds and sixty seconds and variable
3. Flow is increased by increasing mixing time and by increasing the pro portion of mercury in the mix. 4. Crushing strength generally in creases with mixing time and passes through a maximum point as the pro portion of mercury in the mix is in creased. The values obtained in the three mixers are not comparable as the oper ating characteristics vary widely. The following observations are given to indi cate some of these variables.
Tayloi---- Mechanical Amalgamation The type A mixer gave unsatisfactory results, at times due to the characteris tics of the gelatin capsules used. These scaled badly, leaving flakes of gelatin in the amalgam when the mixing time was long and the proportion of mercury low. Rapid agitation causes heating and, in mixing for a minute or more, the cap sules often fall, scattering amalgam widely. The gelatin capsules also con ceal blackening to a considerable extent, although not so completely as if metal
587
any evidence of blackening. Only six samples made in this mixer would pass the Federal specification. The type C mixer gave more nearly uniform results than either of the other types, but, in this case, it was still evi dent that conditions must be carefully defined to produce a satisfactory amal gam. Despite the more nearly uniform characteristic, only six of the samples made would pass all requirements. It is evident that, even when using
Table 5.— A Comparison of Properties of Alloys Nos. 1, 2 and 3 as Influenced by the T y p e A M ixer * M ix in g T im e (S e c o n d s ) P rop erty
A llo y N o.
15 — O.S
— 0.9
45 — 1.5
— 2.0
— 0.5
— 1.0
— 1.5
— 4 .2
— 6.5
— 1.5
1
t + 17.0
+ 7 .0
+ 2 .7
+ 4 .0
+ 5.0
2
+ 3 .5
— 0.6
— 5.2
— 7.5
— 1.2
m ic r o n s p e r cm . P ercen ta g e
3 1
3.2
3.4
5.8
5.9
— 60.0 3.2
o f flo w in 2 4 h o u rs C r u s h in g
2 3
2.0 + -t4 5 ,1 0 0
2.1
1.8
3.1
2.5
45,9 00
56,000
53,500
4 6 ,7 0 0
s tr e n g th ,
2 3
4 5 ,2 0 0
50,100
4 9 ,3 0 0
52,700
45,8 00
34,300
§
C o n t r a c t io n
to
1
1st m in im u m ,
2 3
m ic r o n s p e r cm . C h a n g e in 24 h ou rs,
lb . p e r sq. in .
1
30
60
H a n d M ix e d
— 60.0
33,500
* A U o y t o m e r c u r y ra tio , 5 :9. f P r e l i m i n a r y ru n s in d ic a t e d th a t fu r t h e r tre a tm e n t w o u ld
n o t, u n d e r a n y c o m b in a t io n
o f c ir c u m s t a n c e s , ca u s e th e s e tt in g c h a r a c t e r is t ic s o f th is a llo y to m e e t th e s p e c ific a t io n . f F l o w s p e c im e n s w e r e m a d e o f A l l o y e v e r y c a s e b u t o n e , b o th s a m p le s f a il e d in § C r u s h i n g s tr e n g t h s e c o n d s ’ d u r a t io n .
s p e c im e n s
of
A llo y
capsules are used. In addition, mixes in the same proportion but of varying size were not uniformly mixed. In all, only four samples of Alloy No. 1, mixed in this amalgamator, could be considered as having satisfactory properties. The type B or grinding type of amal gamator was somewhat more unsatisfac tory. Duplicate samples made in it were often characterized by a lack of uniformity caused by a mechanical loss of mercury. This mixer also conceals
N o . 3 f o r a ll p r o p o r t io n s th e m ic r o m e te r . N o.
3 w ere
m ade
o n ly
in d ic a t e d , in
m ix e s
of
and
in
fifte e n
a first quality material, mechanical amal gamation is of rather doubtful value. Satisfactory amalgams can be made only by carefully defining the proper propor tions and mixing times, and even slight variations from these may destroy the valuable properties of our alloys. All types of mixers gave abnormally large expansion values when the mercury con tent was low and the mixing time short. This would indicate that there is the re mote possibility of amalgamating under
588
I'he Journal of the American Dental Association
very special conditions an alloy which would normally shrink slightly and cause it to pass this part of the specifi cation. It will be interesting to keep this point in mind as we consider the results obtained by testing three types of alloys in the type A mixer. A series of tests were made using only the type A mixer but with alloys Nos. 1, 2 and 3, mixed in a variety of pro portions and mixed for various lengths T a b le
6.— A
C om p arison
The data point to the fact that longer mixing times (30 to 45 seconds) may give good results with this alloy pro vided the proportion of mercury to alloy is low. Alloy No. 3 is so uniformly bad that comments are ^not in order. The conclusions drawn from this series of tests of amalgamators and al loys are: 1. Properties of alloys, having satis factory properties when hand mixed,
Nos.
o f P r o p e r tie s o f A l l o y s 1, 2 an d P r o p o r tio n s o f A l l o y t o M e r c u r y *
3 as I n f l u e n c e d
by
P r o p o r t i o n o f A l l o y to M e r c u r y b y W e i g h t H a n d M ix e d P r o p e r t ie s C o n t r a c t io n to
A llo y N o. 1
5:5 0.0
5 :7 0.0
5 :9 — 1.0
5 :1 1 — 0.6 — 0.8
5 :9 — 0.5 — 1.5 — 60.0 + 5.0
— 0.8
1st m in im u m ,
2
0.0
m ic r o n s p e r cm .
— 35.0
— 0.5 — 4 0.0
C h a n g e in
3 1
+ 6 .0
+ 16.0
t + 17.0
+ 6 .0
24 h ou rs,
+ 3.5
+ 2 .8
— 1.2
2
+ 4 .5
+ 5.5
m ic r o n s p e r cm . P ercen tag e
3
— 35.0 3.5
— 4 0 .0
o f flo w in 2 4 h o u rs C r u s h in g
2 3
2.3
1
4 7 ,9 0 0
4 2 ,0 0 0
45,1 00
51,800
4 6,7 00
s tr e n g th ,
2 3
2 9 ,7 0 0
4 4 ,0 0 0
4 5 ,2 0 0
4 9 ,1 0 0
4 5 ,8 0 0
3 2,500
33,7 00
34,300
34,000
33,5 00
lb . p e r sq. in .
1
3.7 2.4
— 60.0 3.2 2.5
4 .2 2.0
3.2 2.0
t
* M i x i n g tim e, fifte e n s e c o n d s . ■¡■Prelim inary ru n s in d ic a t e d th a t fu r t h e r tr e a tm e n t w o u ld n o t , u n d e r a n y c o m b in a t io n o f c ir c u m s t a n c e s , c a u s e th e s e tt in g c h a r a c t e r is t ic s o f th is a llo y to m e e t th e s p e c ific a t io n . J F l o w s p e c im e n s w e r e m a d e o f A l l o y N o . 3 f o r a ll p r o p o r t io n s e v e r y c a s e b u t o n e , b o th s a m p le s f a i l e d in th e m ic r o m e te r . § C r u s h i n g s tr e n g t h s e c o n d s ’ d u r a t io n .
s p e c im e n s
of
A llo y
of times. These data are summarized in Tables V, V I and V II. The results of these tests show that under special conditions as previously mentioned, it may be possible to modify the properties of an alloy that shrinks slightly in hand mixing and actually make it show up better than it would otherwise. The data on A lloy No. 1 have been previously considered. Alloy No. 2 gave satisfactory results as long as the mixing time was fairly short.
N o.
3 w ere
m ade
o n ly
i n d ic a t e d , in
m ix e s
of
and
in
fifte e n
may be varied to give unsatisfactory re sults by mechanical amalgamation. 2. In some particular cases slight shrinkage in certain types of alloys may be overcome by a special carefully worked out mechanical amalgamation technic. 3. Manufacturers of amalgamators should supply definite information as to the use of their product. 4. Manufacturers of alloys to be used in amalgamators should furnish the
589
Taylor— Survey of Amalgam Alloys
dentist with the welfare of his patients necessary information to enable their alloys to be satisfactorily used in me in view. These conclusions must not be taken chanical amalgamators. 5. Mechanical amalgamation, in its as a wholesale condemnation of mechan present state of development and stand ical amalgamation. The field is a com ardization, is both a doubtful and a paratively new one, and our data point to further study and development of dangerous method and, until more defi detailed directions for use as a means nite data are available for the special of making the process useful and valu type of amalgamator in question, should not be employed by the conscientious able. T a b le
7.— A
Nos. 1, 2
C om p arison
o f P r o p e r tie s o f A l l o y s P r o p o r tio n s o f A l l o y t o M e r c u r y *
an d
3
as I n f l u e n c e d
by
P r o p o r t i o n o f A l l o y to M e r c u r y b y W e i g h t H a n d M ix e d — 2.8
5 :7 — 3.5
2
— 3.3
— 5.2
3 1
t + 6 .3
+ 6 .5
2
— 2.0
— 7.0
A llo y N o. 1
1st m in im u m , m ic r o n s p e r cm . C h a n g e in
P r o p e r t ie s C o n t r a c t io n
to
24 h ou rs, m ic r o n s p e r cm . P ercen ta g e
3 1
o f flo w in 2 4 h o u rs C r u s h in g
2
s tr e n g th ,
3 1 2
lb . p e r sq . in .
3
5 :5
5 :9
5 :11
5 :9
— 2.0
— 3.1
— 0.5
— 6.5
— 4 .0
— 1.5
+ 4 .0
+ 4 .5
— 60.0 + 5 .0
— 7.5
— 5.0
— 1.2 — 6 0 .0
4.3 3.0
5.3
5.9
5.4
3.3
3.1
2.5
3.2 2.5
36.8 48,2 00
57,700 .
53,500
56,900
24,8 00
4 8,4 00
52,700
51,500
t 46 ,7 0 0 4 5 ,8 0 0 33,5 00
§
* M i x i n g tim e , s ix ty s e c o n d s . f P r e l i m i n a r y ru n s in d ic a t e d th a t fu r t h e r t r e a tm e n t w o u ld
n o t, u n d e r a n y c o m b in a tio n
o f c ir c u m s t a n c e s , ca u s e th e s e ttin g c h a r a c t e r is t ic s o f th is a llo y to m e e t th e s p e c ific a t io n . J F lo w e v e r y case
s p e c im e n s
w ere
b u t o n e , b o th
§ C ru s h in g
s tr e n g t h
s e c o n d s ’ d u r a t io n .
m ade
s a m p le s s p e c im e n s
of
A llo y
f a il e d of
in
A llo y
N o.
3
fo r
a ll
p r o p o r t io n s
in d ic a t e d ,
and
in
th e m ic r o m e t e r . N o.
3
w ere
m ade
o n ly
in
m ix e s
of
fifte e n
APRIL, 1929
N o. 4
Original Communications
MECHANICAL AMALGAMATION: PROGRESS REPORT OF RESEARCH ON DENTAL MATERIALS* By N . O. TAYLO R,f Ph. D ., W ashington, D.C. H E available data on dental amal gam alloys have shown that the alloys available to the dental pro fession vary widely in their composition and properties. Further, the properties of individual alloys were found to vary a great deal as the alloy to mercury ratio was changed and also as the meth ods of amalgamation were varied. In the past, hand mixing with a preliminary trituration in a mortar has been more or less of an elastic procedure, the total
T
■¡■Research A s s o c ia te , B u r e a u o f S ta n d a r d s . * C o o p e r a tiv e B u rea u
of
resea rch
S ta n d a r d s
by
and
th e th e
N a t io n a l A m e r ic a n
D e n t a l A s s o c ia t io n . * P u b lic a t io n
ap p roved
th e B u r e a u o f S ta n d a r d s p a rtm en t o f C om m e rce .
b y th e D i r e c t o r o f o f th e
U.
S. D e
* R e a d b e f o r e th e S e ctio n o n H is t o lo g y , P h y s io lo g y , P a t h o lo g y , B a c t e r io l o g y and C h e m is t r y
(R e s e a r c h )
at
th e
S e v e n tie th
A n n u a l S e ss io n o f th e A m e r ic a n D e n ta l A s s o c ia t io n , M in n e a p o lis , M in n ., A u g . 22,
1. per
1928.
Jour. A. D. A A p r i l , IQ 2 Q
time consumed in mixing being any where from two to ten minutes. It has been shown that excessively long trituration in the mortar or mulling in the hand led to serious shrinkage in the final product.1 W ith this fact in mind, the question of what effects are to be expected when an alloy is mechanicallv mixed with mercury seemed to offer an interesting field for research, as, in most mechanical amalgamating devices, the rapidity of agitation is increased, with a corresponding decrease in mixing time. Little information regarding mechan ical amalgamation is available, and such as is offered consists largely of indefinite claims and not of data as to perform ance. The problem is of sufficient inter est to warrant a careful study of the fundamental effects of representative types of amalgamators such as are being
583
B u rea u o f N o.
157.
S ta n d a r d s T e c h n o l o g i c P a
The Journal of the American Dental Association
584
C. A type combining centrifugal and rolling actions on samples placed in a small irregularly shaped box mounted eccentrically on a motor shaft. A mixer of each type was used in this study. They are listed as Type A, B or C,
sold to the profession from year to year. Accordingly, a study was made of three types of amalgamators and their effects on the properties of alloys as compared with hand mixed specimens mixed under definitely controlled conditions.
T able 1.— P roperties of H and M ixed A lloys *
A llo y
C o n t r a c t io n to
T ota l C hange
P ercen tag e
1st M in im u m in
in 2 4 H r .
o f F lo w
S tre n g th
in 2 4 H r .
L b . p e r S q. In .
M icr o n s p e r C m .
in M i c r o n s p e r C m .
C r u s h in g
1
— 0.5
+ 5.0
3.2
4 6 ,7 0 0
2
— 1.5
—
1.2
2.5
4 5,8 00
3
— 60.0
t
33,500
* T e s ts fB o th
m ade flo w
in
— 6 0 .0
a ccorda n ce
s a m p le s
b rok e
w it h in
F ederal
S p e c ific a t io n
N o . 356.
m ic r o m e te r .
A survey of the available mechanical according to the previous classification. The selection of variable types of devices offered as amalgamators showed them to be of three general types, as alloys for use in the study made neces sary a survey of the properties of current follow s: Three alloys were A. Those of the vibrating or shak amalgam alloys.2 ing type using a gelatin or metal capsule selected for test, as follows: T able 2.— P roperties of A lloy N o . 1, as A ffected b y V ariations in M ix in g T im e and by D if fe r e n t T ypes o f A m alg am ato rs * A m a lg a m a to r P rop erty
Type A
M ix in g T im e (S e co n d s ) 15
30
60
— 0.7 — 1.5
— 3.5
— 4 .0
A
+ 7 .0
+ 2 .7
+ 4 .0
+ 7 .0
B
+ 7.5
+ 2 .2
— 3.0
— 5.5
— 18.0
m ic r o n s p e r cm . P ercen tag e
C A
+ 2 .7
— 1.0
— 1.3
— 0.6
3.2
3 .4
5.8
5.9
7.0
o f flo w in 2 4 h o u rs C r u s h in g str e n g th ,
B C
3.3
2.5 4.5
2.5
2.7
33.7
8.7
5.2 53,500
50,000
4 2 ,6 0 0
30,800
51,900
2 4 h o u rs,
lb . p e r sq. in.
B C
A
3.2 4 5,1 00
4 5 ,9 0 0
B
4 0,7 00
4 6 ,2 0 0
56,000 4 8 ,4 0 0
C
54,200
52,8 00
53,100
* M i x e d fiv e p a r t s o f a llo y to n in e p a rts o f m e r c u r y b y w e ig h t . h a n d m ix e d , 5 :9 , f o r c o m p a r is o n .
— 2.0
120
— 1.0 + 17.0
m ic r o n s p e r cm . C h a n g e in
— 0.7 0.0
— 0.9
45 — 1.5 — 2 .4
C o n t r a c t io n to 1st m in im u m ,
— 5.5
— 5.5 — 18.0
180 — 11.0
+2
9.5
4 7 ,6 0 0
P r o p e r t ie s o f A l l o y N o . 1,
T o firs t m in im u m — 0 .5 ; in t w e n t y - f o u r h o u rs, + 5 ; flo w in
t w e n t y -f o u r h o u rs , 3.2 p e r c e n t ; c r u s h in g s tr e n g th , 4 6 ,7 0 0 p o u n d s p e r s q u a r e in ch .
and operated on an eccentric support No. 1. A first quality material whose driven by a motor. T h e re su lts o f this s u r v e y a re g iv e n B. The mortar or grinding type of 2. in a s e p a r a t e r e p o r t , “ A S u r v e y o f A m a l mixer having a metal mortar and an g a m A l l o y s ,” f o r w a r d e d to th e R e s e a r c h agitator operated by attaching a shaft C o m m is s io n o f th e A m e r ic a n D e n ta l A s s o to the usual dental handpiece. c ia tio n .
Taylor— Mechanical Amalgamation
minutes in the hand, are given in Table 1. W ith three mixers available and the three alloys mentioned above selected, the experimental work was started and the following series of tests were made: 1. Alloy No. 1 was used in each type of mixer, the proportion of alloy to mercury varying from 5:5 to 5:13 and the mixing time from fifteen seconds to three minutes. 2. Alloys Nos. 2 and 3 were tested in the shaking type of mixer (type A ).
properties were found to comply with all the requirements of Federal Specifi cation No. 356 for Dental Amalgam Alloys. No. 2. A material showing a slight shrinkage after twenty-four hours but whose percentage of flow was low and whose crushing strength was fairly high. No. 3. A very low grade alloy which showed very great shrinkage, whose flow samples crushed under the light loads used in the tests and whose crushing strength was low. T able
3.— P roperties of A llo y
N o. 1 as A ffected by A lloy an d M ercury *
A m a lg a m a to r P rop erty C o n t r a c t io n
Type
585
V ariations
P roportions
in
of
P r o p o r t i o n o f A l l o y to M e r c u r y b y W e i g h t 5 :7
5:5 0.0
5 :11 — 0.6 — 0.4
5:13 — 0.8
— 0 .4
0.0 0.0
0 .0
0.0
5 :9 t — 0 .7 0.0
0.0
— 0.3
— 1.0
+ 6 .0
+ 16.0 + 7 .9
+ 17.0
+ 6 .0
+ 12.8
+ 7 .5
+ 5 .0
+ 10.7
+ 2 .6 3.5
+ 1.8 3.7
+ 2 .8
+ 2 .5
+ 5 .5
2.8
4.2 3.6
4.6
6.1
3.2 3.3
C
3.2
2.6
2.9
4 4 ,9 0 0
4 2 ,0 0 0
51,800
str e n g th ,
A B
3.2 4 5 ,1 0 0
39,400
4 5 ,4 0 0
4 0 ,7 0 0
4 7,5 00
3.7 52,800 4 7 ,0 0 0
lb . p e r sq. in.
C
50,000
51,600
54,200
52,900
47,2 00
1st m in im u m ,
A B
m ic r o n s p e r cm . C h a n g e in
C A B
+ 8 .5
C A B
to
2 4 h o u rs , m ic r o n s p e r cm . P ercen ta g e o f flo w in 2 4 h o u rs C r u s h in g
0.0
4.2
* M i x i n g tim e, fifte e n s e c o n d s . fP r o p e r tie s
of
A llo y
N o.
1,
hand
m ix e d ,
— 0 .5 ; in t w e n t y - f o u r h o u r s , + 5 ; flo w s tr e n g th , 4 6 ,7 0 0 p o u n d s p e r s q u a r e in ch .
in
The physical properties investigated in the entire study were setting changes which indicated the contraction to the first minimum and the total change in twenty-four hours expressed in microns per centimeter, the percentage of flow in twenty-four hours, and the crushing strength. A ll tests were made in ac cordance with Federal Specification No. 356 for Dental Amalgam Alloys. The physical properties of these alloys mixed five parts by weight of alloy to nine parts of mercury, triturated one minute in a glass mortar and mulled for two
5 :9 ,
fo r
tw e n ty -fo u r
c o m p a r is o n . h ou rs,
3.2
To per
firs t
m in im u m
ce n t;
c r u s h in g
the properties and mixing times varying as in 1. It is interesting to note that no directions were given by the manu facturers of the amalgamators as to proper proportioning or mixing time. Knowing the variations in alloy proper ties produced by changing manipulatory methods, this would seem a serious omis sion, more especially so since we have not one but many different types of materials which can be used in these machines. On the other hand, manu facturers of alloys have not seen fit to outline definite treatment for their own
586
The Journal of the American Dental Association alloy to mercury ratios. These data are given in Tables 3 and 4. The data secured in testing Alloy No,. 1 indicate that: 1. Short mixing times with variable proportions of alloy to mercury give small initial contraction values followed by definite expansion, and, in some in stances, excessive expansion. 2. Longer mixing results in larger shrinkage values followed in most cases by incomplete recovery of the loss in length.
alloys in the various types of amalga mators. The net result is that a variety of mixers have been and are being used without data to prove their limitations and adaptability. It is hoped that this study will give sufficient data to show ( 1 ) the effects produced by mechanical amalgamation; ( 2 ) the necessity for further study of, and the development of directions for, the individual types of amalgamators; (3 ) the need for explicit directions for the use of each and every alloy where the manufacturers find their T able 4.— P roperties of A li .oy
1 as A ffected by A lloy and M ercu ry *
N o.
Type A
P roportions of
in
P r o p o r t i o n o f A l l o y to M e r c u r y b y W e i g h t
A m a lg a m a to r
1st m in im u m ,
B
5:5 — 2.8 — 3.8
• m ic r o n s p e r cm . C h a n g e in
C
— 3.8
P r o p e r t ie s C o n t r a c t io n to
V ariation s
5 :7 — 3.5
5 :9 t
5 :11
5:13 — 2.4
— 2.0
— 3.1
— 10.5
— 5.5
— 2.8
— 2 .4
— 5.5
— 4 .0
— 4.6
— 2.8
A
+ 6 .3
+ 6 .5
+ 4 .0
+ 4 .5
+ 6 .7
B
— 3.8
— 8.0
— 5.5
m ic r o n s p e r cm . P ercen tag e
C A
— 2.5 4.3
— 1.6 5.3
— 0.6 5.9
— 3.1 — 2.4
— 4 .2 + 6 .0
5.4
o f flo w in 2 4 h ou rs C r u s h in g
B
5.3
9.6
2 .7
4.1
24 h ou rs,
C
5.8
6.7
5.8
4 8,2 00
57,700
56,900
52,900
s tr e n g th
A B
5.2 53,500
6.1 7.8 5.5
5 3,600
52,900
4 2 ,6 0 0
54,000
53,200
lb . p e r sq. in.
C
55,700
55,900
51,900
50,500
53,000
* M i x i n g tim e, s ix ty s e c o n d s . ■("Properties o f A l l o y N o . 1, — 0 .5 ;
in
tw e n ty -fo u r
h ou rs,
hand
+ 5 ;
m ix e d ,
flo w
in
5 :9 ,
fo r
tw e n ty -fo u r
c o m p a r is o n . h ou rs,
3.2
To
firs t
m in im u m
per
ce n t;
c r u s h in g
s tr e n g th , 4 6 ,7 0 0 p o u n d s p e r s q u a r e in ch .
product adapted to mechanical amalga mation. The tests of Alloy No. 1 with Amal gamators A, B and C gave three series of data. Samples were made using five parts of alloy to nine of mercury, and the mixing time varied from fifteen sec onds to three minutes. This series shows the effect of variations in mixing time independently of other variables. These data are given in Table 2. The second and third series were run with constant mixing times of fifteen seconds and sixty seconds and variable
3. Flow is increased by increasing mixing time and by increasing the pro portion of mercury in the mix. 4. Crushing strength generally in creases with mixing time and passes through a maximum point as the pro portion of mercury in the mix is in creased. The values obtained in the three mixers are not comparable as the oper ating characteristics vary widely. The following observations are given to indi cate some of these variables.
Tayloi---- Mechanical Amalgamation The type A mixer gave unsatisfactory results, at times due to the characteris tics of the gelatin capsules used. These scaled badly, leaving flakes of gelatin in the amalgam when the mixing time was long and the proportion of mercury low. Rapid agitation causes heating and, in mixing for a minute or more, the cap sules often fall, scattering amalgam widely. The gelatin capsules also con ceal blackening to a considerable extent, although not so completely as if metal
587
any evidence of blackening. Only six samples made in this mixer would pass the Federal specification. The type C mixer gave more nearly uniform results than either of the other types, but, in this case, it was still evi dent that conditions must be carefully defined to produce a satisfactory amal gam. Despite the more nearly uniform characteristic, only six of the samples made would pass all requirements. It is evident that, even when using
Table 5.— A Comparison of Properties of Alloys Nos. 1, 2 and 3 as Influenced by the T y p e A M ixer * M ix in g T im e (S e c o n d s ) P rop erty
A llo y N o.
15 — O.S
— 0.9
45 — 1.5
— 2.0
— 0.5
— 1.0
— 1.5
— 4 .2
— 6.5
— 1.5
1
t + 17.0
+ 7 .0
+ 2 .7
+ 4 .0
+ 5.0
2
+ 3 .5
— 0.6
— 5.2
— 7.5
— 1.2
m ic r o n s p e r cm . P ercen ta g e
3 1
3.2
3.4
5.8
5.9
— 60.0 3.2
o f flo w in 2 4 h o u rs C r u s h in g
2 3
2.0 + -t4 5 ,1 0 0
2.1
1.8
3.1
2.5
45,9 00
56,000
53,500
4 6 ,7 0 0
s tr e n g th ,
2 3
4 5 ,2 0 0
50,100
4 9 ,3 0 0
52,700
45,8 00
34,300
§
C o n t r a c t io n
to
1
1st m in im u m ,
2 3
m ic r o n s p e r cm . C h a n g e in 24 h ou rs,
lb . p e r sq. in .
1
30
60
H a n d M ix e d
— 60.0
33,500
* A U o y t o m e r c u r y ra tio , 5 :9. f P r e l i m i n a r y ru n s in d ic a t e d th a t fu r t h e r tre a tm e n t w o u ld
n o t, u n d e r a n y c o m b in a t io n
o f c ir c u m s t a n c e s , ca u s e th e s e tt in g c h a r a c t e r is t ic s o f th is a llo y to m e e t th e s p e c ific a t io n . f F l o w s p e c im e n s w e r e m a d e o f A l l o y e v e r y c a s e b u t o n e , b o th s a m p le s f a il e d in § C r u s h i n g s tr e n g t h s e c o n d s ’ d u r a t io n .
s p e c im e n s
of
A llo y
capsules are used. In addition, mixes in the same proportion but of varying size were not uniformly mixed. In all, only four samples of Alloy No. 1, mixed in this amalgamator, could be considered as having satisfactory properties. The type B or grinding type of amal gamator was somewhat more unsatisfac tory. Duplicate samples made in it were often characterized by a lack of uniformity caused by a mechanical loss of mercury. This mixer also conceals
N o . 3 f o r a ll p r o p o r t io n s th e m ic r o m e te r . N o.
3 w ere
m ade
o n ly
in d ic a t e d , in
m ix e s
of
and
in
fifte e n
a first quality material, mechanical amal gamation is of rather doubtful value. Satisfactory amalgams can be made only by carefully defining the proper propor tions and mixing times, and even slight variations from these may destroy the valuable properties of our alloys. All types of mixers gave abnormally large expansion values when the mercury con tent was low and the mixing time short. This would indicate that there is the re mote possibility of amalgamating under
588
I'he Journal of the American Dental Association
very special conditions an alloy which would normally shrink slightly and cause it to pass this part of the specifi cation. It will be interesting to keep this point in mind as we consider the results obtained by testing three types of alloys in the type A mixer. A series of tests were made using only the type A mixer but with alloys Nos. 1, 2 and 3, mixed in a variety of pro portions and mixed for various lengths T a b le
6.— A
C om p arison
The data point to the fact that longer mixing times (30 to 45 seconds) may give good results with this alloy pro vided the proportion of mercury to alloy is low. Alloy No. 3 is so uniformly bad that comments are ^not in order. The conclusions drawn from this series of tests of amalgamators and al loys are: 1. Properties of alloys, having satis factory properties when hand mixed,
Nos.
o f P r o p e r tie s o f A l l o y s 1, 2 an d P r o p o r tio n s o f A l l o y t o M e r c u r y *
3 as I n f l u e n c e d
by
P r o p o r t i o n o f A l l o y to M e r c u r y b y W e i g h t H a n d M ix e d P r o p e r t ie s C o n t r a c t io n to
A llo y N o. 1
5:5 0.0
5 :7 0.0
5 :9 — 1.0
5 :1 1 — 0.6 — 0.8
5 :9 — 0.5 — 1.5 — 60.0 + 5.0
— 0.8
1st m in im u m ,
2
0.0
m ic r o n s p e r cm .
— 35.0
— 0.5 — 4 0.0
C h a n g e in
3 1
+ 6 .0
+ 16.0
t + 17.0
+ 6 .0
24 h ou rs,
+ 3.5
+ 2 .8
— 1.2
2
+ 4 .5
+ 5.5
m ic r o n s p e r cm . P ercen tag e
3
— 35.0 3.5
— 4 0 .0
o f flo w in 2 4 h o u rs C r u s h in g
2 3
2.3
1
4 7 ,9 0 0
4 2 ,0 0 0
45,1 00
51,800
4 6,7 00
s tr e n g th ,
2 3
2 9 ,7 0 0
4 4 ,0 0 0
4 5 ,2 0 0
4 9 ,1 0 0
4 5 ,8 0 0
3 2,500
33,7 00
34,300
34,000
33,5 00
lb . p e r sq. in .
1
3.7 2.4
— 60.0 3.2 2.5
4 .2 2.0
3.2 2.0
t
* M i x i n g tim e, fifte e n s e c o n d s . ■¡■Prelim inary ru n s in d ic a t e d th a t fu r t h e r tr e a tm e n t w o u ld n o t , u n d e r a n y c o m b in a t io n o f c ir c u m s t a n c e s , c a u s e th e s e tt in g c h a r a c t e r is t ic s o f th is a llo y to m e e t th e s p e c ific a t io n . J F l o w s p e c im e n s w e r e m a d e o f A l l o y N o . 3 f o r a ll p r o p o r t io n s e v e r y c a s e b u t o n e , b o th s a m p le s f a i l e d in th e m ic r o m e te r . § C r u s h i n g s tr e n g t h s e c o n d s ’ d u r a t io n .
s p e c im e n s
of
A llo y
of times. These data are summarized in Tables V, V I and V II. The results of these tests show that under special conditions as previously mentioned, it may be possible to modify the properties of an alloy that shrinks slightly in hand mixing and actually make it show up better than it would otherwise. The data on A lloy No. 1 have been previously considered. Alloy No. 2 gave satisfactory results as long as the mixing time was fairly short.
N o.
3 w ere
m ade
o n ly
i n d ic a t e d , in
m ix e s
of
and
in
fifte e n
may be varied to give unsatisfactory re sults by mechanical amalgamation. 2. In some particular cases slight shrinkage in certain types of alloys may be overcome by a special carefully worked out mechanical amalgamation technic. 3. Manufacturers of amalgamators should supply definite information as to the use of their product. 4. Manufacturers of alloys to be used in amalgamators should furnish the
589
Taylor— Survey of Amalgam Alloys
dentist with the welfare of his patients necessary information to enable their alloys to be satisfactorily used in me in view. These conclusions must not be taken chanical amalgamators. 5. Mechanical amalgamation, in its as a wholesale condemnation of mechan present state of development and stand ical amalgamation. The field is a com ardization, is both a doubtful and a paratively new one, and our data point to further study and development of dangerous method and, until more defi detailed directions for use as a means nite data are available for the special of making the process useful and valu type of amalgamator in question, should not be employed by the conscientious able. T a b le
7.— A
Nos. 1, 2
C om p arison
o f P r o p e r tie s o f A l l o y s P r o p o r tio n s o f A l l o y t o M e r c u r y *
an d
3
as I n f l u e n c e d
by
P r o p o r t i o n o f A l l o y to M e r c u r y b y W e i g h t H a n d M ix e d — 2.8
5 :7 — 3.5
2
— 3.3
— 5.2
3 1
t + 6 .3
+ 6 .5
2
— 2.0
— 7.0
A llo y N o. 1
1st m in im u m , m ic r o n s p e r cm . C h a n g e in
P r o p e r t ie s C o n t r a c t io n
to
24 h ou rs, m ic r o n s p e r cm . P ercen ta g e
3 1
o f flo w in 2 4 h o u rs C r u s h in g
2
s tr e n g th ,
3 1 2
lb . p e r sq . in .
3
5 :5
5 :9
5 :11
5 :9
— 2.0
— 3.1
— 0.5
— 6.5
— 4 .0
— 1.5
+ 4 .0
+ 4 .5
— 60.0 + 5 .0
— 7.5
— 5.0
— 1.2 — 6 0 .0
4.3 3.0
5.3
5.9
5.4
3.3
3.1
2.5
3.2 2.5
36.8 48,2 00
57,700 .
53,500
56,900
24,8 00
4 8,4 00
52,700
51,500
t 46 ,7 0 0 4 5 ,8 0 0 33,5 00
§
* M i x i n g tim e , s ix ty s e c o n d s . f P r e l i m i n a r y ru n s in d ic a t e d th a t fu r t h e r t r e a tm e n t w o u ld
n o t, u n d e r a n y c o m b in a tio n
o f c ir c u m s t a n c e s , ca u s e th e s e ttin g c h a r a c t e r is t ic s o f th is a llo y to m e e t th e s p e c ific a t io n . J F lo w e v e r y case
s p e c im e n s
w ere
b u t o n e , b o th
§ C ru s h in g
s tr e n g t h
s e c o n d s ’ d u r a t io n .
m ade
s a m p le s s p e c im e n s
of
A llo y
f a il e d of
in
A llo y
N o.
3
fo r
a ll
p r o p o r t io n s
in d ic a t e d ,
and
in
th e m ic r o m e t e r . N o.
3
w ere
m ade
o n ly
in
m ix e s
of
fifte e n