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Relative Efficiency of Germicidal Cements*
H ill and Boester— Germicidal Cements at a time when dentistry was floundering in a mist of uncertainties, having lived through an era when the profession be came interested in research and educa tional qualifications were thus expanded, it should continue to function as the con necting link between organized dentistry and the promotion of research. T h e discovery of young men and women who are exceptionally qualified and disposed to devote their lives to den tal teaching and research is the most pressing problem confronting the pro fession of dentistry today. By establish ing a fellowship in biology in some in stitution to stimulate and encourage those qualified for w ork in this field should certainly be one of the functions of or ganized dentistry through the Research Commission. Last December, in A tlantic City, I had the pleasure of seeing dentistry as a
1565
profession given its first place on the program of the American Association for the Advancement of Science. T his marked a gratifying stage in the history of the dental profession. T w o decades ago, when the Research Commission was first founded, dentistry had not earned its spurs. Today, it takes its place on the program, side by side w ith 137 other societies representing all fields of science in mathematics, physics, chemistry, zo ology, botany, sociology, astronomy, en gineering, medicine and dentistry. These insistent efforts of many persons and or ganizations united in such a comprehen sive association for the advancement of learning are exerting a most powerful influence for good on national and inter national development. T his professional advance can be said to be the major ac complishment of the Research Commis sion in its twenty years of existence.
RELATIVE EFFICIENCY OF GERMICIDAL CEMENTS* B y T H O M A S J. H I L L , D .D .S ., and K A R L W . B O E S T E R , C leveland, O h io
H E extensive use of germicidal cements in the practice of dentistry suggests that some consideration be given to their relative efficiency and to the conflicting claims of the manufac turers. T h e literature on this subject is almost entirely the product of commercial lab oratories, and the substance of these re
T
*From the Institute of Pathology, Western Reserve University. *Work aided by a grant from the Callahan Memorial A ward Commission. *Read at the Seventieth Annual M idwinter Clinic of the Chicago Dental Society, Feb. 27, 1934.
Jour. A.D.A., September, 1934
ports is so conflicting that the important issues are clouded w ith uncertainty rather than simplified or explained. Commercial germicidal cement pow ders are usually made of zinc oxide to which some form of copper or silver has been added. W a rd 1 reports these addi tions as follows : Ames’: 99% cupric oxide CuO W hite’s: 2% silver chloride Agcl. or silver phosphate AgaPo« Smith’s : 2% cupric silicate Cu Si Oa Fleck’s: 25% cuprous iodide Cm L 1. W ard, M. L. : American Textbook of Operative Dentistry, Philadelphia: Lea and Febiger, 1926, p. 525.
1566
T he Journal of the American D ental Association
T h e liquids are modified orthophosphoric acid. Free cement liquid has been shown by Smirnow 2 to have marked bactericidal properties, and consequently all cements are germicidal during the setting period. Evidence of free phosphoric acid is lack ing after cements have been allowed to T
able
1 .— R
esu lts
from the combination of the incorporated ingredient and the phosphoric acid. I t is well understood that metallic cop per and silver have bacteriostatic proper ties, but the actual germicidal property of set cements is probably the result of the formation of soluble metallic salt. (Ames.4)
o r A d d it io n o f V a r io u s A m o u n t s o f P u l v e r iz e d M to C u l t u r e s o f Sta ph y lo c o c c u s A u r e u s
150 Mg. Cement in 15 C.c. Broth
75 Mg. Cement in 15 C.c. Broth
ix e d
37.5 Mg. Cement in 15 C.c. Broth
C em ents
20 Mg. Cement in 15 C.c. Broth
Cult.
Subcult.
Cult.
Subcult.
Cult.
Subcult.
Cult.
Subcult.
Base cement with phenylmercuric nitrate additions 1-5,000
-
-
-
-
-
-
-
+
Base cement with phenylmercuric nitrate additions 1- 10,000
-
-
-
-
-
• +
+
+
3.
Kryptex
-
-
-
-
-
+
+
+
4.
Ames’ B. C.
-
-
-
-
-
-
-
+
5.
White’s silver B.
-
-
-
-
-
+
+
+
6. Smith’s C. C.
-
-
-
+
+
+
+
+
7.
Stewart’s silver
-
-
-
-
-
+
-
+
8.
Fleck’s R. C.
-
-
-
-
-
-
+
+
9.
Caulk’s W. C.
-
+
+
+
+
+
+
+
10. Stratford Cookson
+
+
+
+
+
+
+
+
Cement 1.
2.
set for fifteen minutes .8 A fter the setting period, germicidal properties are depen dent on either the ingredient incorporated in zinc oxide, or a soluble salt resulting 2. Smirnow, M. R .: Germicidal Properties of Dental Cements. D. Cosmos, 57:1209 (Nov.) 1915. 3. Fasoli, G .: Silikatzemente und Pulpaveranderungen, Ztschr. f. Stomatol., 22:225, 1924.
T h e germicidal efficiency is dependent on the value of the agent in the hardened cement and on the solubility of this agent. T h e failure to take both of these factors into consideration may explain some of 4. Ames, W . V-B.: Possible Sterilizing Properties of Filling Materials, D. Rev., 28: 572, 1914.
1567
H ill and Boester— Germicidal Cements the confusion arising from the reports on germicidal cements. T he following commercial cements have been used in these experimental tests : kryptex, Ames’ black copper, W hite’s silver B., Smith’s copper silicate, Fleck’s red copper, C aulk’s w hite copper and Stew art’s silver, in which the liquid T
able
2 .— -R e s u l t s
op to
Cookson base cement was used. T his base cement was not germicidal when 150 mg. of pulverized cement was placed in 15 c.c. of broth. T his cement with its phenylmercuric nitrate additions was made by grinding very finely the phenyl mercuric nitrate crystals in a fine agate m ortar and adding it to the cement pow-
A d d it io n o f V a r io u s A m o u n t s o f U n m ix e d C e m e n t P C u l t u r e s o f S ta ph y lo c o c cu s A u r e u s
150 Mg. Powder in 15 C.c. Broth Cement 1 . Base cement powder with phenylmercuric nitrate additions 1-5,000
75 Mg. Powder in 15 C.c. Broth
37.5 Mg. Powder in 15 C.c. Broth
Cult.
Subcult.
Cult.
Subcult.
Cult.
_
_
_
_
_
Subcult.
ow der
20 Mg. Powder in 15 C.c. Broth
Cult.
Subcult.
_
.
2. Base cement powder with phenylmercuric nitrate additions 1-10,000 3.
Kryptex
-
-
-
-
-
-
-
+
4.
Ames’ B. C.
-
-
-
-
-
+
+
+
S. White’s silver B.
-
-
-
-
-
-
-
+
6.
Smith’s C. C.
-
-
+
+
+
+
+
+
7.
Stewart’s silver
-
-
-
-
-
-
-
-
8.
Fleck’s R. C.
-
-
-
-
-
+
+
+
9.
Caulk’s W. C.
-
+
-
+
+
+
+
+
10. Stratford Cookson
is largely or entirely oil of cloves or eugenol instead of orthophosphoric acid. In addition to these commercial prod ucts, tests were made on a cement com posed of various additions of phenylmer curic nitrate to the powder of a base cement for which no germicidal claims are made. For these tests, Stratford
der in various proportions. U niform dis tribution was obtained by shaking in a mechanical shaker. E. E. Ecker provided the phenylmercuric nitrate and gave ad vice regarding this work. T h e commercial cements used were purchased on the open m arket and care was taken to follow the manufacturers’
1568
The Journal of the American D ental Association
instructions which accompanied their re spective packages relative to the mixing of the cement. T h e mixed cements were allowed to set for tw enty-four hours to eliminate free phosphoric acid. They were then pulverized in a m ortar. T h eir germicidal properties were determined by the least percentage by weight of pulverized ce ment necessary to produce both a bacteri cidal and a bacteriostatic effect in broth.
1.00
_l
n M
r—
100
1
—
1 *»g •«4 0.75
1 1 1 I 1 |
40 , c
u
«0.5 0 *
V a n w%. V a Wa '/A W'A m wa « wm %
6
&
•8 gO.25 « $ 0 .1 3
mg. each. T h e dilutions by weight were approximately 1, 0.5, 0.25 and 0.13 per cent. A ll tubes were incubated for fortyeight hours and from these tubes subcul tures were made. Repeated tests gave uniform results. T able I shows the results obtained. C aulk’s white copper, which contains a low percentage of cuprous iodide, had the lowest germicidal efficiency. Sm ith’s copper silicate had a greater
m /AWA»
—
6 «J* ■Sc
—
75 __
50 —
£ ¡3 25
&
CO o
10 0
1 ,2 3 ,4 ,5 ,6 ,7 ,8 ,9 w " 1 7 £T,..* . 5,6 ,7,6,9,10 No. of cement Ho. of cement ■ Percentage of cement i n broth -necessary to be germicidal Percentage of cement in broth necessary to oe bacteriostatic
£
T—1o o p
c ft
Gemente wïth additions o£ P.M.N.
F ig . 1.— Relative bactericidal and bacteriostatic value of pulverized mixed cements in cultures of Staphylococcus aureus and relative diffusibility of germicidal agents to cements in agar. 1, base cement w ith phenylmercuric nitrate additions, 1-5,000; 2, base cement w ith phenylmercuric nitrate additions, 1-10,000; 3, kryptex; 4, Ames’ black copper; 5, W hite’s silver B . ; 6, Smith’s copper silicate; 7, Stewart’s silver; 8, Fleck’s red copper; 9, Caulk’s white copper; 10, Stratford Cookson base cement.
T ubes containing 15 c.c. of standard broth were inoculated w ith one 4-mm. loop of a 24-hour culture of Staphylococ cus aureus. T o these tubes were added the various pulverized cements in the fol lowing am ounts: 150, 75, 37.5 and 20
bactericidal effect, being germicidal in di lutions of 1 per cent and bacteriostatic in dilutions of 0.5 per cent. Stratford Cookson cement containing phenylmercuric nitrate, 1 part in 5,000 parts of pow der; Ames’ black copper, and
H i l l an d B o ester— G e rm ic id a l C em en ts
Fleck’s red copper were germicidal when 37.5 mg. of cement was added to 15 c.c. of broth (0.25 per cent by weight) and bacteriostatic w ith 20 mg. of cement in 15 c.c. of broth (0.13 per cent by w eight). M ost of the remaining cements were nearly equal, being germicidal in dilu tions of 0.5 per cent and bacteriostatic in dilutions of 0.25 per cent. A nother series of tests were conducted in which the germicidal value of the various cement powders not mixed with phosphoric acid was determined. Ames’ black copper powder and Sm ith’s copper silicate were slightly less bactericidal
F ig. 2.— 61, Sm ith’s copper silica te; 62, A m es’ black copper; 63, C aulk’s w h ite copper; 72, kryptex.
when tested in this manner. A ll the other powders were slightly more efficient, as shown in T ab le 2. T h e change in the germicidal value of these powders when mixed w ith phosphoric acid is probably due to the formation of a metallic salt other than the one incorporated. T his new salt must have a greater or lesser solubility or a different bactericidal value. I t is probable th at all of these cements are sufficiently germicidal for clinical
1569
purposes.5 T h eir practical efficiency is de pendent on their bactericidal value plus their solubility. A n effort was made to measure their solubility by determining the penetration into agar of their germi cidal salt. T h e penetration into agar is not comparable to the penetration into the dentin of the tooth, but would indi cate the solubility of the germicidal agent of the cement. M ixed cements were placed in glass tubing 15 mm. long and having a bore of 1.5 mm. T h e cements were allowed to set for twenty-four hours to eliminate the presence of free phosphoric acid. T h e
F ig. 3.— 8, Fleck’s red copper; 3, S tew art’s silv e r ; 10, Stratford Cookson b ase; 1, Strat ford Cookson w ith phenylm ercuric nitrate, 11 0 ,000.
cement cylinders were removed from the glass tubes. A flask of standard agar was melted and inoculated by the addition of a 24-hour culture of Staphylococcus aureus. Petri plates were then poured. A fter the agar had hardened, two cylin drical pieces of agar 1.5 mm. in diameter were punched from each plate by the use 5. Portschke, P . : G erm icid al Efficiency o f D en tal Cem ents, Ind. & E n g. Chem ., 7:195, 1915.
1570
T h e J o u rn a l of th e A m erica n D e n ta l A ssociation
of sterile glass tubing. In these holes were inserted the cylinders of hardened cement. T h e plates were incubated at 37 C. (F o u r plates containing tw o pel lets each of every cement were poured. T h e results for each cement were quite uniform ). O n examination of the plates after tw enty-four hours, clear areas of varying sizes were found around the ce ment pellets. (Figs. 2-3.) T h e aver age penetration of the germicidal agent measured in tenths of a millimeter w e re : Stratford Cookson base cement with phenylmercuric nitrate addition 110,000 .........................................
plate was unwashed and one was washed for tw enty minutes in running distilled w ater. No marked change was shown in the washed and unwashed pellets, al though the more soluble cements showed some slight difference in penetration. (Fig. 4.) In the first chart in Figure 1, the per centage of pulverized mixed cement nec essary to destroy bacteria in broth is shown in black and the shaded area repre sents the percentage of the same material necessary to produce bacteriostatic effects. T h e second portion of this chart (Fig. 1)
Fig. +.— VI, Stratford Cookson base; VIII, Stratford Cookson with phenylmercuric ni trate, 1-10,000. W , pellet washed for twenty minutes in running distilled water.
Fig. 5.—52, Stratford Cookson base with phenylmercuric nitrate, 1-2,000; 53, Stratford Cookson base with phenylmercuric nitrate, 15,000; 54, Stratford Cookson with phenylmer curic nitrate, 1-10,000; 55, Stratford Cookson with phenylmercuric nitrate, 1-20,000.
S tra tfo rd Cookson base cement w ith phenylm ercuric nitrate addition 120,000 ......................................................... 87.5 K ry p te x .........................................................67.0 A m e s ’ black cop per......................................41.0 W h it e ’s silver B .......................................... 50.0 S m ith ’s copper silicate...............................25.0 S te w a rt’s s i l v e r .......................................... 75.0 F le ck ’s red cop per......................................38.0 C a u lk ’s w h ite copper................................. 2.0
T h is experiment was repeated w ith the exception th at one pellet in each petri
represents the penetration into agar of the germicidal agent of mixed cements mea sured in tenths of a millimeter. T h e ce ment used in N o. 10 is Stratford Cook son base, for which no germicidal claims are made. N o. 1 is Stratford Cookson base ce m ent to which additions of phenylmer curic nitrate 1-50,000 parts of powder have been made.
H ill and Boester— Germicidal Cements No. 2 is the same cement w ith addi tions of phenylmercuric nitrate 1- 10,000 parts of powder. No. 7 is Stew art’s silver, the liquid of which is not phosphoric acid, but chiefly eugenol. As this cement sets only to a putty consistency, the liquid probably plays some p art in its penetration. Base cements were mixed w ith phenyl mercuric nitrate in different percentages to determine the variation in their pene trability. T h e results obtained (Fig. 5) are given in T able 3. T
a b l e
3 .— V
a r ia t io n s
in
P
e n e t r a b il it y
Percentage of P h enylm ercuric N itra te in P o w d e r
Penetration in T e n th s of a M illim e te r
0 .0 5 0
1 0 2 .5
0.020 0.010 0 .0 0 5
9 9 .5 8 7 .5 8 2 .0
T his is graphically shown in the second chart in Figure 1. T ests of relative diffusibility of phenyl mercuric nitrate and phenylmercuric acetate, one p art each, in 50,000 parts of powder gave comparable results. Tests were made to determine that the clear areas in the petri plates were the result of the inhibition of bacterial growth by the germicidal agent. Broth cultures were made from both the clear and the clouded areas. In all cases, the clear areas gave negative reactions and the clouded areas gave positive. I t was also noted that plates incubated for a longer period than forty-eight hours showed no change in the size of the clear areas. Although cultures of Staphylococcus
1571
aureus were used throughout these ex periments in order to provide uniform and comparable data, a few tests were made by using mixed cultures made from saliva. T h e results in all of these tests were identical w ith the results obtained when Staphylococcus aureus was used. CONCLUSIONS
1. Commercial germicidal cements are germicidal in broth cultures when mixed in dilutions ranging between 1 and 0.13 per cent. 2. T h e germicidal value of cement powders is changed by the liquid of the cement. Ames’ black copper and Smith’s copper silicate are more germicidal after the addition of the cement liquid. A ll of the other commercial cements and base cement containing additions of phenyl mercuric nitrate are slightly less germici dal after mixing w ith cement liquid. 3. T h eir relative efficiency is depen dent on their solubility as well as on their bactericidal value. 4. T h ere is a wide variation in the solubility of commercial germicidal ce ments as measured by their diffusibility in agar. Some having high germicidal efficiency in broth show little penetration in agar. 5. A nongermicidal base cement w ith additions of phenylmercuric nitrate to the powder, in amounts of from one part in 5,000 to one part in 10,000, is com parable in its germicidal properties to any commercial cement and the germicidal property is vastly more diffusible in agar than w ith cements which depend on the salts of copper and silver for their germi cidal efficiency.
1565
profession given its first place on the program of the American Association for the Advancement of Science. T his marked a gratifying stage in the history of the dental profession. T w o decades ago, when the Research Commission was first founded, dentistry had not earned its spurs. Today, it takes its place on the program, side by side w ith 137 other societies representing all fields of science in mathematics, physics, chemistry, zo ology, botany, sociology, astronomy, en gineering, medicine and dentistry. These insistent efforts of many persons and or ganizations united in such a comprehen sive association for the advancement of learning are exerting a most powerful influence for good on national and inter national development. T his professional advance can be said to be the major ac complishment of the Research Commis sion in its twenty years of existence.
RELATIVE EFFICIENCY OF GERMICIDAL CEMENTS* B y T H O M A S J. H I L L , D .D .S ., and K A R L W . B O E S T E R , C leveland, O h io
H E extensive use of germicidal cements in the practice of dentistry suggests that some consideration be given to their relative efficiency and to the conflicting claims of the manufac turers. T h e literature on this subject is almost entirely the product of commercial lab oratories, and the substance of these re
T
*From the Institute of Pathology, Western Reserve University. *Work aided by a grant from the Callahan Memorial A ward Commission. *Read at the Seventieth Annual M idwinter Clinic of the Chicago Dental Society, Feb. 27, 1934.
Jour. A.D.A., September, 1934
ports is so conflicting that the important issues are clouded w ith uncertainty rather than simplified or explained. Commercial germicidal cement pow ders are usually made of zinc oxide to which some form of copper or silver has been added. W a rd 1 reports these addi tions as follows : Ames’: 99% cupric oxide CuO W hite’s: 2% silver chloride Agcl. or silver phosphate AgaPo« Smith’s : 2% cupric silicate Cu Si Oa Fleck’s: 25% cuprous iodide Cm L 1. W ard, M. L. : American Textbook of Operative Dentistry, Philadelphia: Lea and Febiger, 1926, p. 525.
1566
T he Journal of the American D ental Association
T h e liquids are modified orthophosphoric acid. Free cement liquid has been shown by Smirnow 2 to have marked bactericidal properties, and consequently all cements are germicidal during the setting period. Evidence of free phosphoric acid is lack ing after cements have been allowed to T
able
1 .— R
esu lts
from the combination of the incorporated ingredient and the phosphoric acid. I t is well understood that metallic cop per and silver have bacteriostatic proper ties, but the actual germicidal property of set cements is probably the result of the formation of soluble metallic salt. (Ames.4)
o r A d d it io n o f V a r io u s A m o u n t s o f P u l v e r iz e d M to C u l t u r e s o f Sta ph y lo c o c c u s A u r e u s
150 Mg. Cement in 15 C.c. Broth
75 Mg. Cement in 15 C.c. Broth
ix e d
37.5 Mg. Cement in 15 C.c. Broth
C em ents
20 Mg. Cement in 15 C.c. Broth
Cult.
Subcult.
Cult.
Subcult.
Cult.
Subcult.
Cult.
Subcult.
Base cement with phenylmercuric nitrate additions 1-5,000
-
-
-
-
-
-
-
+
Base cement with phenylmercuric nitrate additions 1- 10,000
-
-
-
-
-
• +
+
+
3.
Kryptex
-
-
-
-
-
+
+
+
4.
Ames’ B. C.
-
-
-
-
-
-
-
+
5.
White’s silver B.
-
-
-
-
-
+
+
+
6. Smith’s C. C.
-
-
-
+
+
+
+
+
7.
Stewart’s silver
-
-
-
-
-
+
-
+
8.
Fleck’s R. C.
-
-
-
-
-
-
+
+
9.
Caulk’s W. C.
-
+
+
+
+
+
+
+
10. Stratford Cookson
+
+
+
+
+
+
+
+
Cement 1.
2.
set for fifteen minutes .8 A fter the setting period, germicidal properties are depen dent on either the ingredient incorporated in zinc oxide, or a soluble salt resulting 2. Smirnow, M. R .: Germicidal Properties of Dental Cements. D. Cosmos, 57:1209 (Nov.) 1915. 3. Fasoli, G .: Silikatzemente und Pulpaveranderungen, Ztschr. f. Stomatol., 22:225, 1924.
T h e germicidal efficiency is dependent on the value of the agent in the hardened cement and on the solubility of this agent. T h e failure to take both of these factors into consideration may explain some of 4. Ames, W . V-B.: Possible Sterilizing Properties of Filling Materials, D. Rev., 28: 572, 1914.
1567
H ill and Boester— Germicidal Cements the confusion arising from the reports on germicidal cements. T he following commercial cements have been used in these experimental tests : kryptex, Ames’ black copper, W hite’s silver B., Smith’s copper silicate, Fleck’s red copper, C aulk’s w hite copper and Stew art’s silver, in which the liquid T
able
2 .— -R e s u l t s
op to
Cookson base cement was used. T his base cement was not germicidal when 150 mg. of pulverized cement was placed in 15 c.c. of broth. T his cement with its phenylmercuric nitrate additions was made by grinding very finely the phenyl mercuric nitrate crystals in a fine agate m ortar and adding it to the cement pow-
A d d it io n o f V a r io u s A m o u n t s o f U n m ix e d C e m e n t P C u l t u r e s o f S ta ph y lo c o c cu s A u r e u s
150 Mg. Powder in 15 C.c. Broth Cement 1 . Base cement powder with phenylmercuric nitrate additions 1-5,000
75 Mg. Powder in 15 C.c. Broth
37.5 Mg. Powder in 15 C.c. Broth
Cult.
Subcult.
Cult.
Subcult.
Cult.
_
_
_
_
_
Subcult.
ow der
20 Mg. Powder in 15 C.c. Broth
Cult.
Subcult.
_
.
2. Base cement powder with phenylmercuric nitrate additions 1-10,000 3.
Kryptex
-
-
-
-
-
-
-
+
4.
Ames’ B. C.
-
-
-
-
-
+
+
+
S. White’s silver B.
-
-
-
-
-
-
-
+
6.
Smith’s C. C.
-
-
+
+
+
+
+
+
7.
Stewart’s silver
-
-
-
-
-
-
-
-
8.
Fleck’s R. C.
-
-
-
-
-
+
+
+
9.
Caulk’s W. C.
-
+
-
+
+
+
+
+
10. Stratford Cookson
is largely or entirely oil of cloves or eugenol instead of orthophosphoric acid. In addition to these commercial prod ucts, tests were made on a cement com posed of various additions of phenylmer curic nitrate to the powder of a base cement for which no germicidal claims are made. For these tests, Stratford
der in various proportions. U niform dis tribution was obtained by shaking in a mechanical shaker. E. E. Ecker provided the phenylmercuric nitrate and gave ad vice regarding this work. T h e commercial cements used were purchased on the open m arket and care was taken to follow the manufacturers’
1568
The Journal of the American D ental Association
instructions which accompanied their re spective packages relative to the mixing of the cement. T h e mixed cements were allowed to set for tw enty-four hours to eliminate free phosphoric acid. They were then pulverized in a m ortar. T h eir germicidal properties were determined by the least percentage by weight of pulverized ce ment necessary to produce both a bacteri cidal and a bacteriostatic effect in broth.
1.00
_l
n M
r—
100
1
—
1 *»g •«4 0.75
1 1 1 I 1 |
40 , c
u
«0.5 0 *
V a n w%. V a Wa '/A W'A m wa « wm %
6
&
•8 gO.25 « $ 0 .1 3
mg. each. T h e dilutions by weight were approximately 1, 0.5, 0.25 and 0.13 per cent. A ll tubes were incubated for fortyeight hours and from these tubes subcul tures were made. Repeated tests gave uniform results. T able I shows the results obtained. C aulk’s white copper, which contains a low percentage of cuprous iodide, had the lowest germicidal efficiency. Sm ith’s copper silicate had a greater
m /AWA»
—
6 «J* ■Sc
—
75 __
50 —
£ ¡3 25
&
CO o
10 0
1 ,2 3 ,4 ,5 ,6 ,7 ,8 ,9 w " 1 7 £T,..* . 5,6 ,7,6,9,10 No. of cement Ho. of cement ■ Percentage of cement i n broth -necessary to be germicidal Percentage of cement in broth necessary to oe bacteriostatic
£
T—1o o p
c ft
Gemente wïth additions o£ P.M.N.
F ig . 1.— Relative bactericidal and bacteriostatic value of pulverized mixed cements in cultures of Staphylococcus aureus and relative diffusibility of germicidal agents to cements in agar. 1, base cement w ith phenylmercuric nitrate additions, 1-5,000; 2, base cement w ith phenylmercuric nitrate additions, 1-10,000; 3, kryptex; 4, Ames’ black copper; 5, W hite’s silver B . ; 6, Smith’s copper silicate; 7, Stewart’s silver; 8, Fleck’s red copper; 9, Caulk’s white copper; 10, Stratford Cookson base cement.
T ubes containing 15 c.c. of standard broth were inoculated w ith one 4-mm. loop of a 24-hour culture of Staphylococ cus aureus. T o these tubes were added the various pulverized cements in the fol lowing am ounts: 150, 75, 37.5 and 20
bactericidal effect, being germicidal in di lutions of 1 per cent and bacteriostatic in dilutions of 0.5 per cent. Stratford Cookson cement containing phenylmercuric nitrate, 1 part in 5,000 parts of pow der; Ames’ black copper, and
H i l l an d B o ester— G e rm ic id a l C em en ts
Fleck’s red copper were germicidal when 37.5 mg. of cement was added to 15 c.c. of broth (0.25 per cent by weight) and bacteriostatic w ith 20 mg. of cement in 15 c.c. of broth (0.13 per cent by w eight). M ost of the remaining cements were nearly equal, being germicidal in dilu tions of 0.5 per cent and bacteriostatic in dilutions of 0.25 per cent. A nother series of tests were conducted in which the germicidal value of the various cement powders not mixed with phosphoric acid was determined. Ames’ black copper powder and Sm ith’s copper silicate were slightly less bactericidal
F ig. 2.— 61, Sm ith’s copper silica te; 62, A m es’ black copper; 63, C aulk’s w h ite copper; 72, kryptex.
when tested in this manner. A ll the other powders were slightly more efficient, as shown in T ab le 2. T h e change in the germicidal value of these powders when mixed w ith phosphoric acid is probably due to the formation of a metallic salt other than the one incorporated. T his new salt must have a greater or lesser solubility or a different bactericidal value. I t is probable th at all of these cements are sufficiently germicidal for clinical
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purposes.5 T h eir practical efficiency is de pendent on their bactericidal value plus their solubility. A n effort was made to measure their solubility by determining the penetration into agar of their germi cidal salt. T h e penetration into agar is not comparable to the penetration into the dentin of the tooth, but would indi cate the solubility of the germicidal agent of the cement. M ixed cements were placed in glass tubing 15 mm. long and having a bore of 1.5 mm. T h e cements were allowed to set for twenty-four hours to eliminate the presence of free phosphoric acid. T h e
F ig. 3.— 8, Fleck’s red copper; 3, S tew art’s silv e r ; 10, Stratford Cookson b ase; 1, Strat ford Cookson w ith phenylm ercuric nitrate, 11 0 ,000.
cement cylinders were removed from the glass tubes. A flask of standard agar was melted and inoculated by the addition of a 24-hour culture of Staphylococcus aureus. Petri plates were then poured. A fter the agar had hardened, two cylin drical pieces of agar 1.5 mm. in diameter were punched from each plate by the use 5. Portschke, P . : G erm icid al Efficiency o f D en tal Cem ents, Ind. & E n g. Chem ., 7:195, 1915.
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T h e J o u rn a l of th e A m erica n D e n ta l A ssociation
of sterile glass tubing. In these holes were inserted the cylinders of hardened cement. T h e plates were incubated at 37 C. (F o u r plates containing tw o pel lets each of every cement were poured. T h e results for each cement were quite uniform ). O n examination of the plates after tw enty-four hours, clear areas of varying sizes were found around the ce ment pellets. (Figs. 2-3.) T h e aver age penetration of the germicidal agent measured in tenths of a millimeter w e re : Stratford Cookson base cement with phenylmercuric nitrate addition 110,000 .........................................
plate was unwashed and one was washed for tw enty minutes in running distilled w ater. No marked change was shown in the washed and unwashed pellets, al though the more soluble cements showed some slight difference in penetration. (Fig. 4.) In the first chart in Figure 1, the per centage of pulverized mixed cement nec essary to destroy bacteria in broth is shown in black and the shaded area repre sents the percentage of the same material necessary to produce bacteriostatic effects. T h e second portion of this chart (Fig. 1)
Fig. +.— VI, Stratford Cookson base; VIII, Stratford Cookson with phenylmercuric ni trate, 1-10,000. W , pellet washed for twenty minutes in running distilled water.
Fig. 5.—52, Stratford Cookson base with phenylmercuric nitrate, 1-2,000; 53, Stratford Cookson base with phenylmercuric nitrate, 15,000; 54, Stratford Cookson with phenylmer curic nitrate, 1-10,000; 55, Stratford Cookson with phenylmercuric nitrate, 1-20,000.
S tra tfo rd Cookson base cement w ith phenylm ercuric nitrate addition 120,000 ......................................................... 87.5 K ry p te x .........................................................67.0 A m e s ’ black cop per......................................41.0 W h it e ’s silver B .......................................... 50.0 S m ith ’s copper silicate...............................25.0 S te w a rt’s s i l v e r .......................................... 75.0 F le ck ’s red cop per......................................38.0 C a u lk ’s w h ite copper................................. 2.0
T h is experiment was repeated w ith the exception th at one pellet in each petri
represents the penetration into agar of the germicidal agent of mixed cements mea sured in tenths of a millimeter. T h e ce ment used in N o. 10 is Stratford Cook son base, for which no germicidal claims are made. N o. 1 is Stratford Cookson base ce m ent to which additions of phenylmer curic nitrate 1-50,000 parts of powder have been made.
H ill and Boester— Germicidal Cements No. 2 is the same cement w ith addi tions of phenylmercuric nitrate 1- 10,000 parts of powder. No. 7 is Stew art’s silver, the liquid of which is not phosphoric acid, but chiefly eugenol. As this cement sets only to a putty consistency, the liquid probably plays some p art in its penetration. Base cements were mixed w ith phenyl mercuric nitrate in different percentages to determine the variation in their pene trability. T h e results obtained (Fig. 5) are given in T able 3. T
a b l e
3 .— V
a r ia t io n s
in
P
e n e t r a b il it y
Percentage of P h enylm ercuric N itra te in P o w d e r
Penetration in T e n th s of a M illim e te r
0 .0 5 0
1 0 2 .5
0.020 0.010 0 .0 0 5
9 9 .5 8 7 .5 8 2 .0
T his is graphically shown in the second chart in Figure 1. T ests of relative diffusibility of phenyl mercuric nitrate and phenylmercuric acetate, one p art each, in 50,000 parts of powder gave comparable results. Tests were made to determine that the clear areas in the petri plates were the result of the inhibition of bacterial growth by the germicidal agent. Broth cultures were made from both the clear and the clouded areas. In all cases, the clear areas gave negative reactions and the clouded areas gave positive. I t was also noted that plates incubated for a longer period than forty-eight hours showed no change in the size of the clear areas. Although cultures of Staphylococcus
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aureus were used throughout these ex periments in order to provide uniform and comparable data, a few tests were made by using mixed cultures made from saliva. T h e results in all of these tests were identical w ith the results obtained when Staphylococcus aureus was used. CONCLUSIONS
1. Commercial germicidal cements are germicidal in broth cultures when mixed in dilutions ranging between 1 and 0.13 per cent. 2. T h e germicidal value of cement powders is changed by the liquid of the cement. Ames’ black copper and Smith’s copper silicate are more germicidal after the addition of the cement liquid. A ll of the other commercial cements and base cement containing additions of phenyl mercuric nitrate are slightly less germici dal after mixing w ith cement liquid. 3. T h eir relative efficiency is depen dent on their solubility as well as on their bactericidal value. 4. T h ere is a wide variation in the solubility of commercial germicidal ce ments as measured by their diffusibility in agar. Some having high germicidal efficiency in broth show little penetration in agar. 5. A nongermicidal base cement w ith additions of phenylmercuric nitrate to the powder, in amounts of from one part in 5,000 to one part in 10,000, is com parable in its germicidal properties to any commercial cement and the germicidal property is vastly more diffusible in agar than w ith cements which depend on the salts of copper and silver for their germi cidal efficiency.