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Tentative Specifications for Dental Casting Investment*
TEN T A T IV E SPECIFICATIONS FOR D EN TA L CASTING ' INVESTM ENT* By WILMER SOUDERf and WILLIAM T. SWEENEY,J Washington, D. C. H E increased accuracy w ith which dental castings can now be prodisced makes necessary selection of accessory materials of definite physical properties. T h e dental investments offered the profession today show a wide range of dimensional changes when subjected to the treatm ents encountered in the dental laboratory. T h ere are also differences in strength, time of setting, fineness and general suitability for use in dental work. T h e careful operator w ill appreciate defi nite information on this m aterial. U n fortunately, he is not being given this information by all makers of investments. T h e specification offered herewith was prepared at the request of the W a r D e partm ent and is offered for the consid eration of those dental school and research laboratories conducting experi ments or tests on dental m aterials having in mind the selection of the best materials. T h e requirements proposed are not ex cessively rigid, but are regarded as the minimum for use in casting operations.
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*Publication a p proved by the d irector of the B u re au of S tan d ard s of the U. S. D e p a rt m ent of Commerce. *R ead before the Section on Histology, Physiology, Pathology, B acteriology and Chem istry (R esearch) at the Seventy-F irst A nnual Session of the A m erican D en tal A sso ciation, W ashington, D. C., Oct. 9, 1929. ■("Principal Scientist, N ational B u re au of S tandards. ^ J u n io r S c ie n tis t, N a t io n a l B u r e a u of S tandards. J o u r. A . D . A ., M a y , 1930
T h e tests, necessary to insure compliance w ith the specification, are not difficult to perform. A sufficient number of data or references to standard methods are given to enable testing laboratories to perform the tests specified. T h e effort to compensate, as far as is possible, for the shrinkage of gold alloys justifies the length requirements. Reasons for the strength requirement, fineness limits and general requirements are evi dent from a study of the object in m ind; viz., the production of a satisfactory cast ing, to dimension, and w ithout roughness or visible defects. I t is believed that m anufacturers will supply a definite need when they uni formly furnish to the profession exact values for the items mentioned in this specification. Certainly, members of the profession w ill be able to eliminate one more of the uncertainties and variables in their work if they select an investment of known properties. T h e following' specification is offered as the best list of values available at this date. Improvements are expected in ma terials and should be matched by in creased limits in the specification. Dental schools following the plan for laboratory experiments outlined in a recent article1 w ill be able to follow these developments 1. Souder, W ilm e r: Physical P roperties of D ental M a terials (Some L ab o ra to ry E x p eri m ents fo r the D ental School), J.A .D .A ., 16: 1829 (O ct.) 1929.
780
Souder and Sweeney— Specifications for D ental Casting Investm ent and to make definite advances in the re quirements as improvements are evolved in investments and should do so for the benefit of their students and as an encour agement to the m anufacturers who spon sor the development of better products.
PROPOSED TENTATIVE SPECIFICATION FOR DENTAL CASTING INVESTM ENT I. G e n era l Specification: T h is m aterial shall be a pow der composed essentially of p la s te r of P a ris, silica, or other refra c to ries a n d chem icals w hich, w hen m ixed w ith w a ter in p ro p e r ratio, applied to the dental w ax p a tte rn and heated in the usual m anner, will be found satisfactory fo r use in casting dental restorations. II. T y p e s: Only one type of m a te ria l is re qu ired . T im e of setting m ay be m odified to suit the needs of the o p e rato r and section V5 should be changed w hen necessary to meet this special need. III. M a te ria l: T h e m ate ria l shall be u n i form and fre e of fo reig n m ate ria l, p artly set o r caked lum ps. C oloring m ate ria l as such w ill not be re g ard e d as fo reig n m ate ria l. IV . G en eral R equirem ents: 1. T h e m a te ria l shall not crack in heating. 2. T h e m a te ria l shall not contam inate the alloy cast into it and shall not cause p ittin g or roughness of su rfaces on the alloy. 3. W h en heated, the m a te ria l shall not give off poisonous or offen sive odors. V. D etail R equirem ents: 1. T h e setting ex pansion shall be 0.05 per cent or o ver at the end of tw en ty -fo u r hours. 2. T h e therm al expansion shall be 0.6 per cent or over w hen h eated fro m room tem p e ra tu re to 700 C. 3. D u rin g the p receding test (V2) the specimen shall not at any tem p eratu re above 200 C. show a length shorter th an the o rig in a l length a t room tem perature, and shall not at any h ig h er tem p eratu re show a shrinkage or de crease in length of m ore th an 0.15 p e r cent of the m axim um length a t any lo w er tem p e ratu re. 4. T h e com pressive stren g th shall be 350 pounds per square inch or over. 5. T h e tim e of setting shall be not less th an fifteen nor m ore th an th irty m inutes. (See p a ra g r a p h II fo r m odification in tim e of setting.) 6. Ninetyfive percent shall pass a No. 100 sieve, and 100 per cent shall pass a No. 30 sieve. VI. M ethods of Inspection and T e sts: 1. Sam pling. T e n pounds of m ate ria l taken at
781
random shall be subm itted fo r test. T h e m a terial, if taken from o rig in a l packages, shall be subm itted in m oisture-proof containers b e a rin g the nam e of the m an u fa ctu re r. 2. T estin g consistency. T h e investm ent used in m aking all test sam ples w ill be m ixed w ith sufficient w a te r to produce a mix of “testing consistency” in accordance w ith the follow ing directions to give a “ slum p” w ithin the fo l low ing lim its: H an d m ixes w ill be spatulated th irty seconds, m echanical mixes fifteen sec onds. A cylindrical m old 2 inches long w ith an in tern al diam eter of 13/i inches w ill be placed on a glass p late and filled. T w o m in utes from the tim e of sta rtin g the mix, the m old w ill be lifted a n d the m ixture allowed to slum p o r sp read o ver the plate. T h e a v e r age of the m axim um and m inim um diam eters of sp read of the slum ped m ixture shall come betw een the lim its of 254 a n d 3 inches. T hese m easurem ents w ill be m ade one m inute a fte r the cylinder is lifted. 3. Setting expansion. T h e change in dim en sion on setting w ill be determ ined on a 30-cm. specim en by observ in g the change w ith a m icrom eter m icroscope com parator or equip m ent of equal accuracy.2 4. T h erm al E xpansion. T h e th erm al ex pansion w ill be m easured on a specim en (1.2 cm. in d iam eter by 20 cm. long, ap p ro x i m ately) by the “fused q u artz expansion a p p a ra tu s ” m ethod, or by the use of equipm ent of equal accuracy. T h is test shall be com pleted in three hours or less.3 5. T im e of Setting. T w o hu n d red g ram s of the sam ple w ill be m ixed w ith enough w a te r to m ake a paste of “ testing consistency” (See V I2) and tested w ith a v icat needle. Setting is considered com plete w hen the needle no longer penetrates to the bottom of the speci m en.4 6. Fineness. Fineness w ill be determ ined by screening 100 gm. of the d ried sam ple through 2. Colem an, R. L .: D ent. Cosmos, 68:746 (A ug.) 1926. B u re au of S ta n d ard s R esearch P a p e r No. 32, D ecem ber, 1928 ; price, 35 cents, Supt. of Docum ents, U. S. G overnm ent P rin t ing Office. 3. H id n ert, P., and Sweeney, W . T . : B ureau of S tan d ard s R esearch P a p e r No. 29, N ovem ber, 1928; price, 10 cents; Supt. of D ocu m ents, U. S. G o v ern m en t P rin tin g Office. 4. A .S.T .M . S ta n d ard s, P a rt II, page 32, 1927, or U. S. G overnm ent M a ste r Specifica tion No. 248.
782
T he Journal of the American D ental Association
the sieves specified, and d eterm ining the am ount of m aterial rem ain in g on each sieve. T h e m ate ria l w ill be shaken through the sieve w ith as little abrasion as possible. 7. Com pressive strength. T w o thousand g ra m s of the sam ple w ill be m ixed w ith enough w a te r to m ake a paste of “testing con sistency” and poured into five cylindrical molds, 2 inches in d iam eter by 4 inches high, the c o ntaining vessel being m oved back and fo rth o ver the m old d u rin g pouring. T h e sam ple will be w orked slightly to rem ove air bubbles and struck off level. T h e cylinders will be rem oved from the m olds as soon as they are h a rd enough to handle, and stored in air at a tem p e ra tu re betw een 60 and 100 F. T ests w ill be m ade a fte r seven days. In com puting the average strength, any cyl in d er w hose strength v a rie s more than IS per cent from the av era g e w ill be discarded. In
case three or m ore cylinders v a ry m ore th an 15 per cent from the av erag e, the lot w ill be discarded and the test repeated.
SUMM ARY 1. F or setting expansion (24 h o u rs), the m inim um is 0.05 per cent. 2. For therm al expansion (700 C .), the m inim um is 0.6 p e r cent. 3. T h e re m ust be no shrinkage from h e at ing (0.15 per cent reversal p erm itted ). 4. T h e com pressive strength, minimum, shall be 350 pounds to the square inch. 5. T im e of setting (as specified or) shall be from fifteen to th irty m inutes. 6. As re g ard s fineness, 95 per cent shall pass a No. 100 siev e; 100 p e r cent shall pass a No. 30 sieve. 7. All general featu res m ust be satisfactory.
RELA TIO N OF D IET TO T H E SKELETAL DEVELOPM ENT OF SW INE, IN C L U D IN G T H E DEVELOPM ENT OF TEETH* By HENRY KLEIN and E. V. McCOLLUM, Baltimore, Md., and S. S. BUCKLEY and PAUL E. HOWE, Washington, D. C. H A T the quality of the diet is an im portant factor in determining the structural characteristics of the teeth and bones of animals has been reported by a number of workers. A detailed re
T
*W ork aided by g ra n ts from the R esearch Com m ission of the A m erican D ental A ssocia tion a n d by g ra n ts from m em bers of the d e n tal staff of the Johns H opkins H ospital. *R ead before the Section on Histology, Physiology, Pathology, Bacteriology and C hem istry (R esearch) a t the Seventy-F irst A nnual Session of the A m erican D ental A s sociation, W ashington, D. C., Oct. 10, 1929. *From the D ep artm en t of Chemical H y giene, School of H ygiene and Public H ealth, the Johns H opkins U niversity, B altim ore, M d., and the A nim al H u sb an d ry D ivision, B u re au of A nim al Industry, U. S. D e p a rt m ent of A griculture, W ashington, D. C. Jo u r. A . D. A ., M a y, IQ30
view of the subject will not be attempted. M ay M ellanby1 has recently reviewed the literature in some detail. W ell controlled investigations of the relation of diet to dentition, and to the incidence of dental defects, are small in number as indicated by an analysis of the dental literature.2 In experiments dealing with this subject, the dog, guinea-pig and rat have been used here tofore as the experimental animals. W hether or not such animals are com parable to human beings in their reac tions to dietary changes and deficiencies, 1. M ellanby, M ay: Physiol. Rev., 8:545 (O ct.) 1928. 2. K lein, H e n ry : J. D ent. Res., 9:5 (Feb.) 1929.
T
*Publication a p proved by the d irector of the B u re au of S tan d ard s of the U. S. D e p a rt m ent of Commerce. *R ead before the Section on Histology, Physiology, Pathology, B acteriology and Chem istry (R esearch) at the Seventy-F irst A nnual Session of the A m erican D en tal A sso ciation, W ashington, D. C., Oct. 9, 1929. ■("Principal Scientist, N ational B u re au of S tandards. ^ J u n io r S c ie n tis t, N a t io n a l B u r e a u of S tandards. J o u r. A . D . A ., M a y , 1930
T h e tests, necessary to insure compliance w ith the specification, are not difficult to perform. A sufficient number of data or references to standard methods are given to enable testing laboratories to perform the tests specified. T h e effort to compensate, as far as is possible, for the shrinkage of gold alloys justifies the length requirements. Reasons for the strength requirement, fineness limits and general requirements are evi dent from a study of the object in m ind; viz., the production of a satisfactory cast ing, to dimension, and w ithout roughness or visible defects. I t is believed that m anufacturers will supply a definite need when they uni formly furnish to the profession exact values for the items mentioned in this specification. Certainly, members of the profession w ill be able to eliminate one more of the uncertainties and variables in their work if they select an investment of known properties. T h e following' specification is offered as the best list of values available at this date. Improvements are expected in ma terials and should be matched by in creased limits in the specification. Dental schools following the plan for laboratory experiments outlined in a recent article1 w ill be able to follow these developments 1. Souder, W ilm e r: Physical P roperties of D ental M a terials (Some L ab o ra to ry E x p eri m ents fo r the D ental School), J.A .D .A ., 16: 1829 (O ct.) 1929.
780
Souder and Sweeney— Specifications for D ental Casting Investm ent and to make definite advances in the re quirements as improvements are evolved in investments and should do so for the benefit of their students and as an encour agement to the m anufacturers who spon sor the development of better products.
PROPOSED TENTATIVE SPECIFICATION FOR DENTAL CASTING INVESTM ENT I. G e n era l Specification: T h is m aterial shall be a pow der composed essentially of p la s te r of P a ris, silica, or other refra c to ries a n d chem icals w hich, w hen m ixed w ith w a ter in p ro p e r ratio, applied to the dental w ax p a tte rn and heated in the usual m anner, will be found satisfactory fo r use in casting dental restorations. II. T y p e s: Only one type of m a te ria l is re qu ired . T im e of setting m ay be m odified to suit the needs of the o p e rato r and section V5 should be changed w hen necessary to meet this special need. III. M a te ria l: T h e m ate ria l shall be u n i form and fre e of fo reig n m ate ria l, p artly set o r caked lum ps. C oloring m ate ria l as such w ill not be re g ard e d as fo reig n m ate ria l. IV . G en eral R equirem ents: 1. T h e m a te ria l shall not crack in heating. 2. T h e m a te ria l shall not contam inate the alloy cast into it and shall not cause p ittin g or roughness of su rfaces on the alloy. 3. W h en heated, the m a te ria l shall not give off poisonous or offen sive odors. V. D etail R equirem ents: 1. T h e setting ex pansion shall be 0.05 per cent or o ver at the end of tw en ty -fo u r hours. 2. T h e therm al expansion shall be 0.6 per cent or over w hen h eated fro m room tem p e ra tu re to 700 C. 3. D u rin g the p receding test (V2) the specimen shall not at any tem p eratu re above 200 C. show a length shorter th an the o rig in a l length a t room tem perature, and shall not at any h ig h er tem p eratu re show a shrinkage or de crease in length of m ore th an 0.15 p e r cent of the m axim um length a t any lo w er tem p e ratu re. 4. T h e com pressive stren g th shall be 350 pounds per square inch or over. 5. T h e tim e of setting shall be not less th an fifteen nor m ore th an th irty m inutes. (See p a ra g r a p h II fo r m odification in tim e of setting.) 6. Ninetyfive percent shall pass a No. 100 sieve, and 100 per cent shall pass a No. 30 sieve. VI. M ethods of Inspection and T e sts: 1. Sam pling. T e n pounds of m ate ria l taken at
781
random shall be subm itted fo r test. T h e m a terial, if taken from o rig in a l packages, shall be subm itted in m oisture-proof containers b e a rin g the nam e of the m an u fa ctu re r. 2. T estin g consistency. T h e investm ent used in m aking all test sam ples w ill be m ixed w ith sufficient w a te r to produce a mix of “testing consistency” in accordance w ith the follow ing directions to give a “ slum p” w ithin the fo l low ing lim its: H an d m ixes w ill be spatulated th irty seconds, m echanical mixes fifteen sec onds. A cylindrical m old 2 inches long w ith an in tern al diam eter of 13/i inches w ill be placed on a glass p late and filled. T w o m in utes from the tim e of sta rtin g the mix, the m old w ill be lifted a n d the m ixture allowed to slum p o r sp read o ver the plate. T h e a v e r age of the m axim um and m inim um diam eters of sp read of the slum ped m ixture shall come betw een the lim its of 254 a n d 3 inches. T hese m easurem ents w ill be m ade one m inute a fte r the cylinder is lifted. 3. Setting expansion. T h e change in dim en sion on setting w ill be determ ined on a 30-cm. specim en by observ in g the change w ith a m icrom eter m icroscope com parator or equip m ent of equal accuracy.2 4. T h erm al E xpansion. T h e th erm al ex pansion w ill be m easured on a specim en (1.2 cm. in d iam eter by 20 cm. long, ap p ro x i m ately) by the “fused q u artz expansion a p p a ra tu s ” m ethod, or by the use of equipm ent of equal accuracy. T h is test shall be com pleted in three hours or less.3 5. T im e of Setting. T w o hu n d red g ram s of the sam ple w ill be m ixed w ith enough w a te r to m ake a paste of “ testing consistency” (See V I2) and tested w ith a v icat needle. Setting is considered com plete w hen the needle no longer penetrates to the bottom of the speci m en.4 6. Fineness. Fineness w ill be determ ined by screening 100 gm. of the d ried sam ple through 2. Colem an, R. L .: D ent. Cosmos, 68:746 (A ug.) 1926. B u re au of S ta n d ard s R esearch P a p e r No. 32, D ecem ber, 1928 ; price, 35 cents, Supt. of Docum ents, U. S. G overnm ent P rin t ing Office. 3. H id n ert, P., and Sweeney, W . T . : B ureau of S tan d ard s R esearch P a p e r No. 29, N ovem ber, 1928; price, 10 cents; Supt. of D ocu m ents, U. S. G o v ern m en t P rin tin g Office. 4. A .S.T .M . S ta n d ard s, P a rt II, page 32, 1927, or U. S. G overnm ent M a ste r Specifica tion No. 248.
782
T he Journal of the American D ental Association
the sieves specified, and d eterm ining the am ount of m aterial rem ain in g on each sieve. T h e m ate ria l w ill be shaken through the sieve w ith as little abrasion as possible. 7. Com pressive strength. T w o thousand g ra m s of the sam ple w ill be m ixed w ith enough w a te r to m ake a paste of “testing con sistency” and poured into five cylindrical molds, 2 inches in d iam eter by 4 inches high, the c o ntaining vessel being m oved back and fo rth o ver the m old d u rin g pouring. T h e sam ple will be w orked slightly to rem ove air bubbles and struck off level. T h e cylinders will be rem oved from the m olds as soon as they are h a rd enough to handle, and stored in air at a tem p e ra tu re betw een 60 and 100 F. T ests w ill be m ade a fte r seven days. In com puting the average strength, any cyl in d er w hose strength v a rie s more than IS per cent from the av era g e w ill be discarded. In
case three or m ore cylinders v a ry m ore th an 15 per cent from the av erag e, the lot w ill be discarded and the test repeated.
SUMM ARY 1. F or setting expansion (24 h o u rs), the m inim um is 0.05 per cent. 2. For therm al expansion (700 C .), the m inim um is 0.6 p e r cent. 3. T h e re m ust be no shrinkage from h e at ing (0.15 per cent reversal p erm itted ). 4. T h e com pressive strength, minimum, shall be 350 pounds to the square inch. 5. T im e of setting (as specified or) shall be from fifteen to th irty m inutes. 6. As re g ard s fineness, 95 per cent shall pass a No. 100 siev e; 100 p e r cent shall pass a No. 30 sieve. 7. All general featu res m ust be satisfactory.
RELA TIO N OF D IET TO T H E SKELETAL DEVELOPM ENT OF SW INE, IN C L U D IN G T H E DEVELOPM ENT OF TEETH* By HENRY KLEIN and E. V. McCOLLUM, Baltimore, Md., and S. S. BUCKLEY and PAUL E. HOWE, Washington, D. C. H A T the quality of the diet is an im portant factor in determining the structural characteristics of the teeth and bones of animals has been reported by a number of workers. A detailed re
T
*W ork aided by g ra n ts from the R esearch Com m ission of the A m erican D ental A ssocia tion a n d by g ra n ts from m em bers of the d e n tal staff of the Johns H opkins H ospital. *R ead before the Section on Histology, Physiology, Pathology, Bacteriology and C hem istry (R esearch) a t the Seventy-F irst A nnual Session of the A m erican D ental A s sociation, W ashington, D. C., Oct. 10, 1929. *From the D ep artm en t of Chemical H y giene, School of H ygiene and Public H ealth, the Johns H opkins U niversity, B altim ore, M d., and the A nim al H u sb an d ry D ivision, B u re au of A nim al Industry, U. S. D e p a rt m ent of A griculture, W ashington, D. C. Jo u r. A . D. A ., M a y, IQ30
view of the subject will not be attempted. M ay M ellanby1 has recently reviewed the literature in some detail. W ell controlled investigations of the relation of diet to dentition, and to the incidence of dental defects, are small in number as indicated by an analysis of the dental literature.2 In experiments dealing with this subject, the dog, guinea-pig and rat have been used here tofore as the experimental animals. W hether or not such animals are com parable to human beings in their reac tions to dietary changes and deficiencies, 1. M ellanby, M ay: Physiol. Rev., 8:545 (O ct.) 1928. 2. K lein, H e n ry : J. D ent. Res., 9:5 (Feb.) 1929.