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bacteria. T h e pectins, gums, a n d waxes, no doubt, are used up b y t h e m first, t h e nitrogen-containing substances next, a n d , as t h e medium used in our experiments was devoid of carbohydrates, t h e cellulose finally was drawn upon b y t h e bacteria as a source of energy. This probably would not be t h e case in t h e practical application of bacteria t o t h e t r e a t m e n t of cotton cloth before bleaching, as t h e period of incubation would have t o he reduced t o a minimum. T h e weakening of t h e cloth would be eliminated entirely. a n d a cheaper, safer, a n d more convenient process for t h e purification of cotton cloth preliminary t o its bleaching would t h u s be obtained. Since t h e conclusion of t h e above described preliminary experimental investigations, studies have hecn carried on with a view t o applying bacteria t o practical purification of various cellulose fibers. By using different combinations of bacterial species, different media, different reactions of t h e media t o s t a r t with, a n d different temperatures during t h e period of incubation, t h e latter was reduced t o 7 2 , 48, 3 6 , a n d in some cases even t o 24 hrs., all depending upon t h e n a t u r e of t h e fibers used. A number of tests on a large scale were also performed for t h e purification of paper-making stock in connection with one of t h e eastern paper making factories, a n d for t h e purification of cotton yarn a n d cotton cloth in connection with some of t h e Rhode Island bleacheries. I n all cases t h e results obtained were very encouraging.
Vol. 8 ,
KO.4
VI-Bacteria m a y bc profitably employed :LS a substitute for t h e present method of purifying cloth preliminary t o its bleaching. T h e present paper records a p a r t of t h e work done by t h e author along similar lines for Mr. J. .:I Hehden of Providence, R . I., in connection with ;ind under t h e auspices of t h e Biological Laboratory of Brown University. T h e author wishes t o express his gratit u d e t o t h e instructing staff of t h e Brown University Biological Laboratory a n d t o 11r. Hebden for their general and generous assistance in t h e work and for permission t o publish t h e results. BIOLOCICAI. Lneoa~ro~u. BROWN Faovsm!~cl;. R . I.
UNIVERSITY
PHYSICAL PROPERTIES OF DENTAL CEMENTS RY P*U'
POBT.CHBB
Receivcd Decembrr 2 2 . I l l 5
The principal types of dental cement which occupy a useful place in dentistry ?t t h e present time are known technically as t h e silicate, zinc oxyphosphate a n d copper cements. All of these products reach the dentist in t h e f o r m of a powder a n d liquid t o be combined, as occasion requires, by a special process of mixing. The constituents a n d applicatioris of t h e three types a n d t h e various properties upon which their uses in applied dentistry depend. arc given in Table I. I n order t o determine t h c "filncss" of :L dental
SUMMARY
I-Of
all t h e natural impurities of cotton cloth only t h e nitrogencontaining a n d t h e ether-soluble substances, when insufficiently removed from t h e cloth previously t o t h e "chemick," cause yellowing of bleached cloth in t h e steam test or during storage. 11-The nitrogenous substances of t h e fibers were broken down b y bacteria so t h a t t h e y were completely removed from t h e cloth. This transformation i n t h e presence of t h e calcium hydroxide has probably resulted in some cases in t h e formation of either free ammonia or nitrogen, calcium carbonate, a n d water, a n d in some in t h e reduction of t h e nitrogenous substances t o peptones a n d amino acids which are easily oxidized t o nitratcs a n d nitrites. 111-The ether-solublc suhstances of t h e cloth were removed in our experiments by bactekial . t r e a t m e n t more efficiently t h a n is t h e case in t h e ordinary bleaching process. IV-The alcohol-soluble substances were very little attacked by t h e bacteria, probably because of t h e formation of a calcium salt in t h e presence of t h e calcium hydroxide of t h e media. V-Sone of t h e bacteria experimented with havc transformed t h e starch of t h c cloth a n y further t h a n to dextrins.
cement, due consideration must be givcn t o its various properties, individually a n d collectively. A silicate cemcnt which does not possess t h c required color a n d translucency would he lacking in t h e essential requirements of this typc of cemcnt. and no mattcr how perfect in other respects, it would fail to fulfil its main p u r p o s e i t s ability t o match t h e tooth structure in appearance. Likewise. germicidal efficiency is essential in a copper cement. I t is obvious t h a t
Apr., 1916
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
a n investigation of t h e various dental cements, as regards t h e properties enumerated in Table I , is of great importance t o t h e dental profession. T h e chemical composition of a dental cement re-
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cement has a definite a n d uniform effect does not warrant generalizations with respect t o t h a t same constituent when present in another cement. I n other words, t h e effect of various constituents of
TABLE1-CONSTITUENTS, APPLICATIONS A N D IMPORT.4NT PROPERTIES OF DENTALCEMENTS POWDER COSSTITCESTS LIQVIVCOSSTITLIEITS llodifiers and those PRIS- hlodiiiers and those T V P OP ~ PRISUSE IN APPLIEDDENTISTRY not generally used CIPAL not generally used CIPAL CEYEST ZnO NazO HzO Fillings in anterior and posterior teeth. Only type of dental cement which SILICATE 3$!$ Be0 KzO HaPo4 simulates natural dentitic enamel Ah (OH)B MXO ZINC AlzOa Cementation,of caps, crowns, bridges, inlays and facings, ZnO Fillings malnly posterior
{
PHOSPHATE
CuO CuzIz 7
,--
Thermal conductivity Constancy of volume Crushing strength
HzO BiaOs CuSiOs CuHP04 PROPERTIES--PHYSICAL PERMANENTTensile strength Hydraulicity Porosity Translucency Adhesion Permeability
COzOs FezOs MgO
--
Posterior fillings. Treatment of deep-seated caries in children’s teeth. Generally for posterior fillings where thorough cavity preparation is impracticable. Cementation of caps, crowns and bridges. Indicated wherever increased germicidal action is required and possibility of discoloration is unimportant PHYSIOLOGICAL CHEMICAL PROPERTIES -.TEMPORARY PROPSRTIES Hardness Germicidal efficiency Solubility Density Color Plasticity Toxic action on pulp Discoloration
veals b u t meager information with respect t o its physical a n d other properties. Nevertheless, t h e dental literature is replete with articles in which opinions are freely expressed with reference t o t h e ultimate effects of a given constituent on all classes of dental cements. Systematic investigation of every
; :2
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dental cements cannot be predicted a n d must be individually determined, since these effects depend largely upon t h e physical condition and t h e peculiar association of all of t h e constituents. All tests of dental cements must be conducted in accordance with a fixed a n d uniform procedure, and
TABLE11-CRUSHING STRENGTH OF DENTALCEMENTS Liquid used with silicates, 0.20 cc.; liquid used with zinc copper cements, 0.25 cc. Relative Grams Setting CRUSHINGSTRENGTH (Lbs. per 5 mm. cylinder) Room Humidity of Time OIL----SALIVATemp. Per Powder Min. 15 1 7 28 1 7 28 NO. NAME OF PRODUCT OF. cent(a) Required 2OoC. Min. Day Days Days Day Days Days SILICATES-SHOWINGNo RETROGRESSION I N STRENGTH IN SALIVA 1230 1295 1448 628 1235 1385 1445 1-DeTrey’sSyntheticPorcelain.. .................... 72.2 71/a 45 0.800 1243 1350 970 888 1210 915 2-New Ascher’s Artificial Enamel ..................... 81.0 63/4 548 65 0.550 3-New Harvardid Translucent Enamel.. 76.3 70 0.500 10 505 788 975 993 705 745 990 918 85.1 330 1073 788 835 838 55 0.750 12I/r 733 4--Dr. Abrahamy’sTranslucin.. ...................... 78.7 955 240 270 80 0.625 51/4 380 760 878 225 5-dental porcelain Cement .......................... IN STRENGTH IN SALIVA SILICATES-SHOWINGRETROGRESSION 6-Ames’ Berylite,(No. 7 Slow-Setting Liquid) . . . . . . . . . . 78.1 85 0.700 10 ( b ) 563 1120 1338 1388 1073 1243 1200 7-Schoenbeck’sSilicate Cement. ...................... 81.4 60 0.600 6l/4 353 932 1130 I120 743 890 830 IN SALIVA ZINC OXYPHOSPHATES-SHOWING No RETROGRESSION IN STRENGTH ‘908 15 0.900 22 980 1230 1185 768 833 968 8-Petroid Improved.. ............................... 66.1 1063 23 1053 1233 945 660 853 955 25 0.800 9-Harvard Cement.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.3 24 873 1023 778 675 450 730 943 75 0.600 10-Caulk’s New Diamond Cement.. . . . . . . . . . . . . . . . . . . . 75.5 22 50 1.150 780 703 883 440 658 798 810 11-Caulk’s Crown & Bridge & Gold Inlay Cement. . . . . . . 77.0 16 653 623 819 608 663 45 0.800 440 772 73.6 l2-vyvex ........................................... 633 615 69 7 688 65 685 0.800 10 13-D. C. C. Hydraulic Inlay Crown & Bridge Cement.. . . 76.8 583 328 600 630 605 555 652 20 0.800 11 14-Ames’ Special Crown & Bridge Cements (Liquid ‘“2”). 70.4 565 493 393 368 23 , 35 0.800 757 15-J. B. Moyer’s Imp. Crown & Bridge Cement.. . . . . . . . 75 .O 382 425 343 427 ZINC OXYPHOSPHATES-SHOWING RETROGRESSION IN STRENGTH IN SALIVA 843 16-Lithos Oxyphosphate of Zinc Cement.. . . . . . . . . . . . . . . 77 .O 70 0.800 21 933 1235 1070 715 965 955 700 16 898 17-Ajax Crown & Bridge Cement.. .................... 81.7 65 0.750 383 700 848 988 895 867 1123 20 945 998 18-Dun’s Cement.. ................................. 58.0 0.800 10 498 895 795 1010 17 840 19-Fellowship Cement.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57.7 20 0.800 860 510 683 748 510 720 773 20-Fleck’s Cement for Crown & Bridge & Inlay Work.. . . 76.5 80 0.900 630 18 433 680 778 757 21-Akme SDecial Crown & Bridee Cement.. . . . . . . . . . . . . 74.5 9 655 ~. 75 0.800 ._. 378 765 723 9 83.4 22-Alston phosphate Cement.. .: . . . . . . . . . . . . . . . . . . . . . . 70 0.650 660 663 420 223 583 545 50 658 385 23-Goldsmith’s C. & B. & Inlay Cement.. . . . . . . . . . . . . . . 8 3 . 6 0.800 10 643 280 540 353 24-Miller’s C. & B. & Inlay Cement. . . . . . . . . . . . . . . . . . . . 74.4 702 468 35 0.800 15 298 378 340 665 375 25-Gibraltar Crown & Bridge Cement.. . . . . . . . . . . . . . . . . 76.2 255 218 190 78 218 65 0.800 88 190 165 _ ~ COPPERCEMENTS-SHOWING N O RETROGRESSION I N STRENGTH I N SALIVA 2 6 P e t r o i d Improved with Copr-Zinc.. . . . . . . . . . . . . . . . . . 82.0 60 0.900 21 635 920 1190 1183 955 833 955 27-Caulk’s Black Copper Cement ...................... 81.5 60 1.000 24 430 693 928 1030 685 920 940 28-Copr-Zinc with Caulk’s C. & B. & Gold Inlay Cement Liquid.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75.5 35 1.150 15 563 785 825 963 870 799 930 29-Caulk’s Red Copper Cement.. . . . . . . . . . . . . . . . . . . . . . 80.3 50 1.000 11 473 808 885 1000 788 800 918 30-Caulk’s New Diamond Cement with Copr-Zinc.. . . . . . 78.2 65 0.600 24 448 735 970 1035 683 750 840 31-Caulk’s C. & B. Gold & Inlay Cement with Copr-Zinc. . 73.8 45 1.150 18 507 660 698 845 595 755 833 32-Fleck’sRed Copper Cement ........................ 81.2 65 0.900 17 418 653 763 950 640 773 804 33-Fellowship Oxyphosphate of Copper Cement, Black.. . 83.4 70 .0.600 20 213 540 658 775 530 570 705 3 P D . C. C. Zinc Copper Cement, Black . . . . . . . . . . . . . . . . 78.5 65 0.700 16 255 480 695 780 430 540 660 35-Fellowship Copper Cement, White . . . . . . . . . . . . . . . . . . 84.5 55 0.750 24’/a 105 100 95. 145 18n 26.1 R5n .---” ”” COPPERCEMENTS-SHOWINGRETROGRESSION IN STRENGTH t~ SALIVA 36-Smith‘s Copper Cement ............................ 65.5 25 0.900 22 628 970 923 1027 970. 903 797 37-Ames’ New ProcessOxyphosphateof Copper Cement .... 82.0 65 1.400 17 465 983 930 1125 935 1000 788 38-Amalgam Cement(c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.3 70 0.900 8 405 655 755 768 718 803 730 39-J. B. Moyer’s White Copper Cement . . . . . . . . . . . . . . . . 86.3 55 0.800 19 275 363 468 555 398 503 430 4 G D e c i d o Copper Cement, Black . . . . . . . . . . . . . . . . . . . . . . 79.6 ‘70 1.000 25 230 458 468 538 280 270 000(d\ ( a ) Obtained frqm wet and dry bulb hygrometer readings in still air, using the Bureau of Standards Psychrometer charts (B. of O., Ciuc. 55, 117). ( b ) Average of eight determinations. Setting not constant. ( c ) This product is not a true copper cement, b u t is included among the copper cements because the liquid contained copper. It does not contain the metals present in dental amalgams and the name is therefore an illusion. ( d ) Disintegrated.
+
--
..............
~~~
~~~
.
property of merely one dental cement, in order t o determine t h e precise effect of various additions t o t h e basic constituents, is an immense undertaking. T h e mere fact t h a t a certain constituent in one dental
I
this must be in harmony with mouth conditions. T h e object of laboratory tests is t o secure trustworthy evidence regarding t h e behavior of these materials in t h e mouth, a n d i t is precisely this requirement
.
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which complicates t h e work a n d makes i t exceedingly difficult to devise suitable methods of testing. T h e object of this paper is to present a method for determining the crushing strength of dental cements; a s t u d y Of various factors related thereto; t h e results obtained on f o r t y commercial dental cements. repre-
Vol. 8 , No, 4
weight. The main difficulty encountered was that a film of cement (the excess) attached itself to the cylinder and this threw the opposite faces out of parallel. This was especially the case with the first molds, the two shown to the left of Fig. 3. An attempt to correct this defect was made by cutting a ridge around the openings (to receive the excess of cement) as shown in the third mold from the left. This also failed to accomplish the purpose. The next change in the molds is shown in the mold at the right in Fig. 3. In this case
Gb. Fir. ~-MVLDS-ADOPTIID FORM
the openings were brought to a knife edge even with the PIC;. 2 C,lS:hT'>-.i T l i > , r ~ a x n r , . . a l l l x r r l : %.AR ,11111 ' i . l l l i X W l l l l i T l i X * \ ? I CIIX. flat faces of the mold. This gave fairly perfect cylinders. * I ! C T 1 0 9 . 1 v o x \\nrr:a r X o U 'rI3r:X"oL; ,k,TT,.W I t was soon found. however, that uniform results could sentinp. t h e silicatc, zinc osyphosphatc, a n d copper not he obtained by using a Kana-mold of this type. and also, t y p e s ; a n d finnlly, t h e utility of t h e
