Mar., 191;
1
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
c-Apparatus must be standard and easily obtainable, or t h e method must not depend upon t h e details of construction of t h e apparatus used. The present report furnishes only partial information with regard t o a n y of these requirements. It does, however, help t o p u t our knowledge of the process of crude oil distillation on a firmer basis a n d furnishes necessary comparative data with regard t o t h e mechanism of three typical distillation methods. The next phase of t h e problem t o be studied is t h a t of “cracking” a n d i t is proposed t o determine in a n empirical way t h e temperature a n d time factors which fix its minimum limit. A third section of the work will deal with a correlation of technical requirements a n d will also furnish information with regard t o the specifi? advantages of t h e known distillation methods. CHEMICAL SECTION O F PETROLEVM DIVISIOX U S. BUREAUof MINES, PITTSBURGH
THE GERMICIDAL EFFICIENCY OF DENTAL CEMENTS By PAULPOETSCHKE Received January 11. 1915 INTRODUCTION
Dental cements, which are used by t h e dental profession because of their bactericidal properties, are known as “Copper Cements” or “Copper Oxyphosphates.” Their advantage over other dental cements lies in t h e increased germicidal power secured b y t h e use of certain compounds of copper. These cements reach t h e dentist in t h e form of a liquid a n d powder. There are several types of “copper cement’’ on t h e market, these being characterized largely by their color. The powders of t h e cements now in use appear as white, red, black, or varicolored compounds. The liquid supplied with t h e majority of these cements consist essentially of concentrated solutions of orthophosphoric acid, H3P04, modified by t h e addition of hydrated oxide of alumina, A12(OH)6. Occasionally other metallic salts, such as iron and nickel, are added. Hydrated oxide of alumina is used as a modifier in order t o control the reaction of t h e liquid on t h e powder when t h e two are combined by spatulation. White copper cement powder consists of calcined oxide of zinc, magnesia and bismuth, t h e copper being added in t h e form of cuprous iodide, Cuz12, cupric phosphate, CuHP04, cupric silicate, CuSiOs, or other light colored copper salts. Black copper. cement powder consists of either black copper oxide, CuO, a n d cobalt oxide, or black copper oxide a n d zinc oxide with or without other oxides such as magnesia a n d bismuth. Red copper cement powder consists essentially of zinc oxide and cuprous oxide, CuzO, other oxides such as magnesia a n d bismuth being occasionally present. Red pigments are also added t o improve t h e color, which is not a deception, provided sufficient cuprous oxide is used t o give t h e cement mass‘ t h e requisite germicidal power. T h e varicolored cement powders consist essentially of zinc oxide, magnesia, and bismuth, with a small proportion of light colored copper compounds such as cupric silicate, cupric phosphate, or other light colored copper salts. Pigments are added t o obtain t h e various shades.
These various dental cements are mixed for use by t h e dentist on a glass slab, upon which t h e powder a n d liquid are separately placed, t h e powder being subsequently incorporated in small amounts at a time, with a nickel-plated or agate spatula, until a certain consistency is obtained. The proper consistency is dependent upon t h e character of t h e individual cement, a n d is generally given by t h e manufacturer in t h e descriptive matter accompanying t h e package of cement. Very little information is contained in dental literature on t h e subject of germicidal efficiency of dental cements, a n d t h e little information which has been circulated is very often of a misleading character, having been presented largely for advertising purposes. It is possible t o measure t h e germicidal efficiency of material of this character in precisely t h e same way as i t is possible t o measure t h e germicidal efficiency of disinfectants. It is therefore obvious, especially in view of t h e varied composition of these cements, t h a t a thorough investigation of this subject is of immediate interest t o t h e dental profession, as well as t o chemists and bacteriologists who may be called upon t o report on t h e germicidal power of dental cements. The object of this paper is t o show t h e comparative germicidal power of these cements. and also some of t h e compounds used in their production. E X P E R I M E NT ALS E R I E S I-CUPROUS
G E R MIClD A L E F F I C I E N C Y T E ST S OXIDE, CUPRIC O X I D E , A K D CAL-
OXIDE-The object of these tests was t o determine, if possible, t h e comparative germicidal efficiency of t h e red a n d black copper oxide, as compared with calcined zinc oxide. Saliva was obtained from one individual by means of khewing unflavored gum. Glass beads were added t o j o cc. of saliva, in a sterile 4 oz. glass-stoppered bottle, a n d t h e bacteria separated by shaking for a period of I O minutes; I O cc. of t h e saliva were transferred t o each of five sterile I oz. glass-stoppered bottles; I cc. of t h e saliva was removed from each bottle, a n d t h e various dilutions plated in standard agar. One gram of each of t h e samples t o be tested was added t o t h e bottles in t h e order described below. T h e fifth bottle remained as a control on t h e number of bacteria present in the saliva during t h e test. All five bottles were shaken and then incubated a t 37’ C. for 24 hours. The bottles were then removed from the incubator a n d shaken thoroughly for one minute, a n d t h e sediment caused b y t h e samples .under examination was allowed t o settle for 5 minutes. At t h e end of this time I cc. was removed from each of t h e five bottles a n d various dilutions plated in standard infusion agar. The plates in both series of determinations were incubated a t 37 O C. for a period of 48 hours, with t h e results given in Table I. The results of these tests indicate t h a t t h e amount of red copper oxide a n d black copper oxide which was dissolved by t h e saliva was suffici’ent t o produce practical sterilization, a n d t h a t t h e zinc oxide in itself, while not sufficient t o produce practical sterilization, shows a germicidal efficiency of 96.z per cent. CINED
ZIKC
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
196 CUPROUS
OXIDE,
IODIDE,
IN
CUPRIC
PHOSPHATE,
ADMIXTURES
WITH
AND
CUPROUS
CALCINED
ZINC
OXIDE
a-The object of this test was t o determine, if possible, t h e relative germicidal efficiency of cupric phosphate a n d cuprous iodide in comparison with cuprous oxide when these different compounds of copper were mixed with calcined oxide of zinc. The manner in which these tests were conducted was precisely t h e same as used in Series I a n d t h e results given in Table I show t h a t t h e cuprous oxide and cuprous iodide in t h e quantities used, a n d in t h e presence of Z ~ R C oxide, produce practical sterilization in 2 4 hours. It is also shown t h a t the cupric phosphate is less efficient under similar conditions t h a n cuprous oxide or cuprous iodide. SERIES 3-These tests were conducted with t h e object of determining still more definitely what t h e efSERIES
TABLE I-TESTS
OF COPPERCOMPOUNDS AND ZINC OXIDE Per cent No. LIVINGBACTERIA PER Cc. Per cent calc,ined Just before After incuba- Germicidal copper zinc addition of 1 tion for 24 efficiency compound oxide g. of sample hrs. a t 37’ C. per cent
SERIES1 : Copper red’ 100 None Oxide black 100 None None 100 Control Saliva (Blank) SERIES2: I 99 ; ; y s 5 95
1
)
Cupric Phosphate}
3iY
}
10 1 5 10 1 5
10 Control Saliva (Blank) SERIES3 : 0.1 0.5 1.0
p?ty
0.1 0.5
%zghate}
::x2@
}
1.0 0.1 0.5
1.0 Control Saliva (Blank)
90 99 9i
99.9 99.5 99.0 99.9 99.5 99.0 99.9 99.5 99.0
9,000,000 8,200,000 10,500,000 9,400.000
Lessthan 100 Less than 100
99.9 99.9 96.2
8,800,000 9,500,000 8,400,000 12,900,000 10,300,000 9,000,000 10,900,000 13,000,000 11,900.000 10,700,000
Less than 50 Less than 50 Less than 50
99.9 99.9 99.9 98.9 99.9 99.9 99.9 99.9 99.9
5,600,000 5,100 000 5,500,000 7,400,000 6,100,000 6,200,000 5,900,000 7,600,000 7,000,000 3,900,000
550,000 17,900
~
394,000 12,900,000
142,000
-.. 200
130
Less than 50 Less than 50 Less than 50
..
8,900,000
1 on
12,600 8,900 41,000 335,000
Less than 100 5,100 18,300,000
90.1 99.6 99.9 99.8 99.8 99.3 94.3 99.9 99.9
..
fect of cuprous oxide, cupric phosphate, and cuprous iodide would be in t h e presence of smaller quantities of these copper compounds in admixture with calcined zinc oxide. T h e tests were conducted in t h e same manner as in Series 2 , except t h a t 2 0 cc. of saliva were used for one gram of t h e powder, instead of I O cc. for one gram, as in Series 2 . T h e object of making this greater dilution was t o reduce the quantity of powder in proportion t o t h e saliva, so t h a t t h e germicidal efficiency obtained in t h e different materials would be more pronounced. The results indicate t h a t these compounds of copper produce a marked effect in increasing t h e germicidal power. It will, however, be observed t h a t t h e period of incubation of 2 4 hours is too long, or else t h a t t h e dilutions are not sufficiently great to give definite information as t o the germicidal efficiencies of t h e various compounds. The object of this work was largely t o determine whether a n increase in germicidal efficiency could be obtained with small quantities of copper compounds. The results of t h e tests, given in Table I, show without question t h a t t h e various compounds of copper used in t h e tests show powerful germicidal action. It is, however, necessary t o conduct these tests under
I
V O ~7. , NO. 3
t h e conditions in which t h e compounds will actually exist when used in a dental cement, since in t h e three series just described, t h e powders alone have been tested, and not the powders mixed into a cement mass with a balanced liquid and allowed t o set. For this reason t h e work on the uncombined powder was discontinued, and a further series of tests were CORducted with t h e powder in combination with a n appropriate liquid as a cement. VARYIKG P E R C E N T A G E S O F CUPROUS IODIDE ADDED T O
A DENTAL CEMEKT, COMPARED W I T H T W O COPP E R CEMEKTS A K D OKE C E M E N T F R E E FROM COPPER
4-The tests were conducted in t h e same manner as Series 3, except t h a t the periods of exposure were I hour and 24 hours. The powders were prepared by combining t h e cement powders with the liquid, allowing t h e mass t o set between glass plates for 48 hours, and then reducing t h e mass in an agate mortar, after which t h e powder was carefully sifted through a S O . 2 j bolting silk. The results are given in Table 11. They show t h a t the various additions of cuprous iodide t o Caulk’s Crown & Bridge & Gold Inlay Cement produce complete sterilization in I and in 2 4 hours. It will be noted t h a t Caulk’s Crown & Bridge & Gold Inlay Cement, which does not carry any copper, is markedly germicidal. Ames’ New Process Oxyphosphate of Copper also produces complete sterilization in I and in 2 4 hours. Smith’s Copper Cement is shown t o be deficient in germicidal power, since i t fails t o produce practical sterilization in I hour. An analysis of Smith’s Copper Cement shows t h a t i t contains t h e equivalent of 0 . 7 5 j per cent copper oxide, CuO, which is apparently present either as copper hydrate or copper silicate. This quantity of copper and the nature of t h e compound is such t h a t high germicidal power cannot be obtained from t h e quantity which is used. SERIES 5-This series is a duplication of Series 4, except t h a t t h e exposure periods were reduced t o 5 minutes, 1 5 minutes, a n d I hour, in order t o more clearly show t h e germicidal efficiency,, since, as observed in t h e case of Series 4, t h e various percentages of cuprous iodide did not show a n y difference, for t h e simple reason t h a t t h e exposure period of I hour is sufficient t o destroy all of t h e bacteria, whereas a shorter exposure period will not do so. The results of Series j are given in Table 11, where they are also expressed in terms of germicidal efficiency, which represents t h e percentage of organisms originally present which were killed b y t h e cement. A study of t h e d a t a found in Series 5 shows t h a t t h e addition of I t o 5 per cent of cuprous iodide to Caulk’s Crown & Bridge & Gold Inlay Cement gives practical sterilization in j minutes exposure a n d complete sterilization in 15 minutes exposure. Ames’ New Process Oxyphosphate of Copper apparently shows a higher efficiency when mixed with a nickel spatula t h a n when mixed with a n agate spatula. With t h e exception of t h e results obtained with this cement when mixed with a n agate spatula, it i s eviSERIES
Mar., 1915
T H E J O U R N A L O F I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
dent t h a t practical sterilization is obtained in j minutes exposure and complete sterilization in 1 5 minutes exposure. Smith’s Copper Cement shows incomplete sterilization throughout, and it is also seen t h a t a slightly higher efficiency is obtained with this cement when mixed with a nickel, t h a n when mixed with an agate spatula. This is true in both the j-minute and I jminute exposure. There is apparently a slightly higher efficiency when mixed with a n agate spatula in the I-hour exposure, b u t in this case t h e results are so
I97
Cement are both much weaker in germicidal power t h a n these cements. Smith’s White Copper Cement shows the lowest germicidal power of the entire series. TESTS O F T H R E E CEMENTS AND ONE M I X T U R E
SERIES 7-Caulk’s Copr-Zinc is a preparation containing IO per cent cuprous iodide, and therefore has j times the concentration of Caulk’s White Copper Cement. It is not used alone as a cement, b u t is used in the proportion of one part of Copr-Zinc t o four parts of Crown & Bridge & Gold Inlay Cement. The plates in each case after incubation were counted
TABLE 11-GERMICIDALEFFICIENCY TESTS ON SEVERAL CEMENTSWITH VARYINGPERIODSOR EXPOSURE SERIES 4 No. OF LIVINGBACTERIA PER Cc.
SERIES5 NO. OR LIVINGBACTERIA PER CC. Just before After exposure of addition of 1 5 15 g. of sample min. min.
hr.
Per cent germicidal efficiency after exposure of 5 min. 15 min. 1 hr.
0 0
99.8 95.8
100 99.9
1,000,000 56.9 500,000 35.8
62.0 47.1
87.3 90.5
100 100 100 100 100 45.7
100 100 100 100 100 71.4
Just before After exposure of SAMPLE addition of 1 1 24 SERIES 4 AND 5: g. of sample hr. hrs. Ames’ New Process Oxyphosphate of Copper: Mixed with Nickel Spatula.. . . . 7,000,000 0 0 Mixed with Aeate Soatula.. . . . 9.000.000 0 0 , , Smith’s Copper Cement:& Mixed with Nickel Spatula.. 15,000,000 2,000,000 0 Mixed with Agate Spatula.. . . . 15,000,000 770,000 0 Caulk’s Crown & Bridge & Gold Inlay Cement Containing Per Cent Cuprous Iodide: 1 ....................... 14,000,000 0 0 2 ....................... 10,000,000 0 0 3 ....................... 7,400,000 0 0 4 8,900,000 0 0 1,800 0 5 ....................... 12,000,000 0 ....................... 11,000,000 4,500,000 0 Control Saliva (Blank). 12,000,000 10,000,000 17,400,000 SERIES6: Smith’s White Copper Cement. . . . . . . . . . . . . . . Caulk’s White Copper Cement.. ............. ...................... Caulk’s Red C o m e r Cement.. ...................... Ames’ New Pro& Oxyphosphate of Copper Cement.. Decido Copper Cement.. Fellowship Oxyphosphate of Copper Cement..
5,200,000 6,000,000 5,000,000 8,000,000 10,000;000 7,000,000 6,000,000
0 0 0 0 0 2,000,000 8,000,000
9,000,000 10,000,000 7,000,000 10,000,000 10,000,000 7,000,000
1,500,000 0 0 96.3 0 97.1 96.0 0 200,000 10.0 0 200,000
closely identical t h a t the conclusion appears warranted t h a t this cement will give in precisely the same manner as with Ames’ New Process Oxyphosphate of Copper, a slightly higher efficiency when mixed with a nickel spatula. Caulk’s Crown & Bridge & Gold Inlay Cement, while showing a slightly lower efficiency t h a n Smith’s Copper Cement in the 5-minute and I-hour exposure, apparently shows approximately the same efficiency in t h e I j-minute exposure, and as far as the general results show there is but little difference between this cement and Smith’s Copper Cement, as far as the germicidal efficiency is concerned. It must be remembered, however, t h a t Caulk’s Crown & Bridge & Gold Inlay Cement is not a copper cement, and therefore it will be seen t h a t Smith’s Copper Cement is deficient in the germicidal power t o be expected of a copper cement.
and then photographed, and are shown in t h e accompanying photographs, Nos. I , 2 3, 4, j and 7. The technique followed in Series 7 varied slightly from t h a t followed in t h e other tests, particularly in t h a t only Ij-minute exposures were made, and t h a t the powder and saliva were thoroughly shaken immediately before plating. Only one dilution was plated, representing I/IO,OOO cc. of the original saliva. I n dividual controls were eliminated, one control serving for this series. The photographs show very plainly the growth of colonies in the saliva itself, as well as in the saliva expose$ t o Caulk’s Crown & Bridge & Gold Inlay Cement and Smith’s Copper Cement. It will, however, be observed t h a t in t h e case of Caulk’s Crown & Bridge & Gold Inlay Cement t o which Copr-Zinc was added, and Ames’ New Process Oxyphosphate of Copper Cement, the plates were both sterile.
...
.......................
.......
......................
............... ,. . . . . . . . . . . . . . .......................................... .......................
S E R I E S O F C O P P E R CEMENTS N O W ON T H E MARKET
6-These tests were conducted with the cement mixed in all cases by means of an agate spatula. I n other respects the technique was t h e same as t h a t employed in the tests in Series 5. The results, given in Table 11, show t h a t Caulk’s White Copper Cement, Caulk’s Red Copper Cement, and Ames’ New Process Oxyphosphate of Copper Cement are almost identical in germicidal power. Decido Copper Cement and Fellowship Oxyphosphate of Copper Cement require I j minutes exposure in which t o secure t h e germicidal efficiency obtained from Caulk’s White Copper Cement, Caulk’s Red Copper Cement, and Ames’ New Process Oxyphosphate of Copper Cement in only 5 minutes exposure. This shows t h a t Decido Copper Cement and Fellowship Oxyphosphate of Copper SERIES
6,800,000 5,000,000 7,900,000 5,300,000
11,000 210,000
0 100
3,400,000 3,000,000 3,400,000 2,800,000
1
95.3 99.4 99.9 99.9 99.9 28.5
..
...
100 100
...
83.3 100 100 100 100 96.0 98.0 96.4 9 7 . 1 66.6 99.9 100
METHODS I N USE FOR D E T E R M I N I N G T H E BACTERICIDAL P R O P E R T I E S O F DENTAL CEMENTS
The experimental part of this paper clearly shows t h a t the germicidal power of a dental cement can be determined. I t is evident t h a t a standard or uniform method of testing should be employed in work of this character, and unless the technique is given, it is obvious t h a t such work would be of little value. AUTHOR’S METHOD
The following method has been developed as a result of the experimental work given in this paper: PREPARATION O F T H E CEMENT-The manufacturers of dental cements almost invariably give t h e instructions t o be followed in the mixing of a given cement, and therefore it is only fair t h a t these instructions
,
198
T H E J O U R N A L OF I N D U S T R I A L AiVD ENGINEERIING C H E M I S T R Y
he rigidly observed. The cement is therefore mixed in accordance with t h e instructions, using whatever character of spatula is recommended, a n d t h e cement mass placed between glass plates. separated b y glass guides so a s t o form a disk of t h e cement. I t is then allowed t o set for a period of 48 hours, after n7hich it is powdered in a n agate mortar a n d carefully bolted through Yo. 2 5 bolting silk. Metallic sieves should never be used for t h e purpose. A sufficient number of mixes are made t o yield approximately 3 g. of powder. This powder is placed in a glass vial a n d is now ready for t h e test for germicidal efficiency. . SALIVA is obtained from one or more individuals by means of chewing paraffin. The individual is instructted t o rinse t h e mouth with water, and then to chew a piece of paraffin, rejecting t h e saliva until t h e mass o i p a r a f i n is soft and adherent, a f t e r which t h e saliva is collectcd in a sterile glass-stoppered bottle until a
SEUCrS 7
Petri dish showins colonies of bacterin from 1110,000 cc. oi saliva. 1022colonier or 10,220,000 bacteria per CE.
sufficient quantity has been obtained. If t h e saliva from more t h a n onc individual is collected, it is all finally mixed a n d strained through several thicknesses of sterile cheese-cloth, in order t o remove large particles from t h e saliva. Sterile glass beads are then added t o t h e strained saliva a n d t h e bacteria separntcd by shaking vigorously. TEcHmQuE-Turenty cc. of saliva are measured into a sterile I oz. glass-stoppered bottle and t h e hottie placed in a water bath maintained a t a tempcral u r e of 3 7 - C. One gram of t h e prepared cement powder is weighed on a clock glass, a n d held in readiness for its addition t o t h e saliva. The bottle containing t h e saliva is t h e n shaken for one minute, I cc. withdrawn a n d plated in t h e proper dilution a s a n individual control. One gram of powder is then added to t h e bottle, t h e hottie thoroughly shaken for one minute, a n d transfers made a t intervals of 5 and 1 5 minutes, proper dilutions of these transfers being plated.
Vol. 7, No. 3
During t h e exposure period, t h e bottles are shaken for a minute a t intervals of 5 minutes, t h e final shaking of one minute being made heiore t h e final transfer. The proper dilution is then plated in nutrient agar-agar a n d incubated a t 3 7 O C. for 48 hours. If more t h a n one test is t o he conducted a t one time, i t is simply necessary t o repeat t h e above procedure. Experience with this method has shown t h a t dilutions of I/Ia,oaa cc. invariably yield plates which can be properly countcd, although in some instances a dilution of I/roa,ooo cc. is preferable in the case of t h e saliva itself. NOTES-The object of using a hardened ccment, one in which t h e chemical reactions involved have reached equilibrium, is t h a t in this condition all of t h e cements t o be compared have reached a fixed state. The results are not influenced b y such factors a s t h e setting time. A cement which could only act
SBRIBS 7 Petri dish piatrcl with Ir10,OOO cc. oi saliva exposed to Caulk's Crown 8: Bridge & Gold lolay Cement with Copr-Zinc added. cdonies. eermicidai loo per
-
germicidally in a plastic condition, loses this property on setting, and would obviously be of no permanent value. Any liqud disinfcctant applied t o t h e cavity before inserting t h c cement would d o a s much work. It is t h e continued giving off of germicidal salts after the ccment mass has set, which i s the important factor. This is accomplished through t h e gradual y e t infinitesimal solubility of the cement. A cement which is germicidal in t h c hardened state will ccrtainly be germicidal in t h e plastic state, if not more so. From a practical standpoint, i t would be impossible t o determine germicidal efficiency accurately by using a cement in t h e plastic state. First: It would be almost impossible t o use a fixed and uniform amount of such a plastic in all of t h e tests; any variation in t h e amount of t h e plastic would introduce a variable. Second: It would be practically impossible t o control t h e s t a t e of t h e mix, since this is continually varying whilc in the plastic state, and therefore, another varia-
hlar.,
1915
2"E J O CR.V.I 1. OF 12v13 L'STkI '4 L A N D E.VGI
