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New American Dental Association specification no. 19 adopted
New American Dental Association specification no. 19 adopted American Dental Spécification No. 19 for Elastomeric Impression M atériel
Council on Dental M a te ria ls and Devices
(Approved November, 1966. Effective November 1, 1 9 6 7 .)
1. Scope and classification T he following new A m erican D ental A ssociation specification no. 19 fo r elastom eric im pression m aterial has been approved by the C oûncil on D ental R esearch of the A m erican D en tal A sso ciation. T he A ssociation’s program fo r form ula tion and revision of specifications, form erly under th a t Council, has now been transferred to the C ouncil on D ental M aterials and Devices. T he form ulation of the specification was carried on through the Specifications C om m ittee of the D ental M aterials G roup, International A ssocia tion for D ental R esearch, and by one of its sub comm ittees. T he C ouncil wishes to acknowl edge, with thanks, the w ork of the subcom m ittee m em bers: G eorge D ickson (c h a irm a n ), N ational B ureau of Standards, W ashington, D .C .; Jam es Cresson, T he L. D . C aulk C om pany, Division of D entists’ Supply C om pany of New Y ork, M il ford, D el.; F . H . Freem an, K err M anufacturing C om pany, D etroit; E ugene M olnar, Coe L ab o ra tories, Inc., Chicago; G. E . M yers, School of D entistry, U niversity of M ichigan, A n n A rbor; G u n n ar Ryge, D ental H ealth C enter, U.S. Public H ealth Service, San Francisco; W. T . Sweeney, N ational B ureau of Standards, W ashington, D.C., and C. L. B um s (se c re ta ry ), N ational B ureau of Standards, W ashington, D .C .
1.1 Scope. This specification is for dental impres sion materials with a polysulfide or a silicone rubber base. 1.2 Types and classes. Impression materials cov ered by this specification shall be of the following types and classes: Type I. Polysulfide base Class 1. Heavy body Class 2. Regular body Class 3. Light body Type II. Silicone base Class 1. Heavy body Class 2. Regular body Class 3. Light body
2. Applicable specifications 2-1 Specifications. The following specification forms a part of this specification. American Dental Association Specification No. 2 for Casting Invest ment for Dental Gold Alloy (first revision). (Copies of American Dental Association specifications may be obtained on application to the Council on Dental Materials and Devices, American Dental Associa tion, 211 East Chicago Avenue, Chicago, 60611.) 3. Requirements 3.1 Material. Both the base and the accelerator shall be homogeneous and free of foreign materials and impurities. When mixed as directed by the man ufacturer’s instructions accompanying the package, the material shall be suitable for taking impressions in the oral cavity. 1039
3.1.1 Toxicity. The manufacturer shall submit a statement that the impression material, used accord ing to the directions supplied with the material, has no toxic effect on the normal healthy person. 3.1.2 Color. The base and accelerator shall be of contrasting colors. 3.2 Physical properties. 3.2.1 The requirements for mixing time, working time, consistency, permanent deformation, dimen sional stability, flow, and strain in compression shall be as listed in the table. 3.2.2 Reproduction. The material shall reproduce a line 0.025 mm. wide when tested by the method outlined in 4.3.10.
3.2.3 Compatibility. 3.2.3.1 Compatibility with gypsum. The material shall impart a smooth surface to and shall separate cleanly from a cast made from unmodified alpha calcium sulfate hemihydrate (6.1) to which has been added, if necessary, sufficient calcium sulfate dihydrate to adjust the setting time to 10 ± 3 minutes. The method for determining the time of setting shall be that given in American Dental Association Specification No. 2 for Casting Investment for Dental Gold Alloy (first revision). A gypsum cast poured against the material in accordance with 4.3.11.1 shall reproduce a line 0.025 mm. wide. The gypsum shall itself be capable of reproducing a line 0.025 mm. wide when allowed to harden against the test block. 3.2.3.2 Compatibility with metalizing baths. The materials shall be compatible with either acid copper plating baths or alkaline silver plating baths when tested by the method outlined in 4.3.11.2. The manu facturer’s instructions shall specify the type of plat ing bath to be used. 3.2.4 Deterioration. The permanent deformation when determined by the method outlined in 4.3.6 shall not exceed 4 percent for Type I and 2 percent for Type II materials that have been stored at 60± 2.0°C . for 7 days in accordance with 4.3.12. After storage the material shall show no gross separation. 3.2.5 Instructions for use. Instructions for use shall include the proportions of base and accelerator to give a proper mix, both by weight and by volume; mixing time; working time; type of metalizing bath to be used, and the minimum time for leaving the impression in the mouth when the material is mixed at 23.0± 2.0°C . and 5 0 ± 1 0 percent relative humidity.
4. Sampling, inspection, and testing procedures 4.1 Sampling. A sample consisting of four pack ages shall be procured at retail by a member of the American Dental Association. This sample shall be forwarded in the original unopened package or pack ages to the American Dental Association Council on Dental Materials and Devices, 211 East Chicago Avenue, Chicago, 60611. 1040 ■ JADA, Vol. 74, April 1967
4.2 Inspection. Compliance with the requirements of 3.1, 3.1.2, 3.2.5, and 5 shall be determined by visual inspection. 4.3 Physical tests. 4.3.1 Standard test conditions. All physical tests shall be made under uniform atmospheric conditions of 23.0± 2.0°C . and 5 0 ± 10percent relative humidity. Materials and test equipment shall be conditioned in the test room for not less than 10 hours before testing. The materials shall be mixed according to the manufacturer’s instructions. All test mixes shall be proportioned by weight with a weighing tolerance of ± 0.1 Gm. 4.3.2 Standard mixes. Two sizes of standard mixes shall be used depending on the size of the test speci men to be made. A small standard mix shall consist of amounts of base and accelerator to give 8± 0.5 Gm. of the mixed material. A large standard mix shall consist of amounts of base and accelerator to give 20 ± 1 Gm. of the mixed material. 4.3.3 Mixing time. Sufficient materials to make a large standard mix shall be mixed according to the manufacturer’s instructions. The mix shall be con sidered to be satisfactory if a uniform, essentially streak-free mix is obtained within 1 minute. 4.3.4 Working time. A small standard mix shall be prepared and retained on the mixing pad in a com pact layer approximately 3 mm. thick. A steel rod, 2.4 mm. in diameter with flat ends and weighing 10 Gm., shall be applied to the surface at 20-second intervals and raised slowly. The needle shall be withdrawn from the test material at approximately (no faster than) the rate at which the needle pene trated the material. The end of the rod shall be wiped clean after each application. The working time shall be recorded as the time elapsed from the start of the mix to the time at which the material fails to string and an indentation persists when the rod is withdrawn. The value for working time shall be the average of three determinations and shall be recorded to the nearest 30 seconds. 4.3.5 Consistency. A volume of 0.5 ml. of a small standard mix of material shall be deposited on a cellophane-covered glass plate. Two minutes after the start of mix, the 0.5 ml. of material shall be covered with another cellophane sheet and a glass plate (approximately 75 G m .) plus a 500-Gm. weight. At 12 minutes after the start of mix, the load (glass plus 500-Gm weight) shall be removed, and the major and minor diameters of the slumped mass of material shall be measured. The value for consistency shall be the average of three determina tions and shall be recorded to the nearest millimeter.
4.3.6 Permanent deformation. 4.3.6.1 Preparation of test specimens. Test speci mens shall be made from a small standard mix by placing a ring 30 mm. inside diameter and 16 mm. high on a flat glass or metal plate and filling the ring slightly more than half full with the impression ma-
terial. A mold, 12.7 mm. inside diameter, 25.4 mm. outside diameter, and 19 mm. high, shall be placed immediately inside the ring and forced into the material until the mold touches the plate and the material has exuded onto the top of the mold. A flat glass or metal plate shall be pressed on the top of the mold to remove excess material. At 2 minutes from the start of mix, the mold and accom panying plates shall be immersed in a 3 7± 1°C . water bath. The mold and plates shall remain in the water bath the minimum time recommended by the manufacturer for leaving the impression material in the mouth (3.2.5). One minute after removal of the specimen from the water bath, the specimen shall be tested by the method described in 4.3.6.2. [The molds may be lubricated With a silicone grease (highvacuum type) to prevent the impression material from adhering to the mold.] 4.3.6.2 Test procedure. The specimen shall be placed in an instrument consisting essentially of a dial gauge graduated in 0.02 mm., mounted to a steady base and equipped with a screw, positioned in such a manner that sufficient force can be ap plied to the specimen to produce the required amount of strain (Fig. 1). One minute after removal from the water bath, a plate weighing 2.5± 0.5 Gm. shall be placed on top of the specimen and the foot of the dial gauge shall be brought into contact with the plate. The weight of the plate plus the force of the spring in the gauge shall be 5 0 ± 5 Gm. The dial gauge shall be read 30 seconds after the foot of the gauge contacts the plate and the value recorded as reading A. The dial gauge foot shall be lowered 2.3 mm. by means of the screw and shall be main tained in this position on the specimen for 30 sec onds; then the foot of the dial gauge shall be raised and the specimen allowed to rest under no load (except that of the lightweight plate) for 30 seconds. The dial gauge foot shall again be brought into contact with the plate on the specimen for 30 sec onds and a second reading shall be taken. This value shall be recorded as reading B. The difference be tween readings A and B, divided by the original length of the specimen and multiplied by 100, shall be considered to be the percentage of permanent deformation. The height of the mold (19.0 mm.) shall be considered to be the original length of the specimen. The value for permanent deformation shall be the average of three determinations and shall be recorded to the nearest 0.1 percent. 4.3.7 Strain in compression. 4.3.7.1 Preparation o f specimens. Specimens shall be prepared as described in 4.3.6.1 (permanent deform ation). 4.3.7.2 Test procedure. Six minutes after removal from the water bath, the specimen shall be placed in a suitable instrument (Fig. 2) and shall be sub jected to a load calculated to produce a stress of 100 G m ./cm .2 Thirty seconds later, the dial indi-
Fig. 1 ■ Instrument for measuring permanent deforma tion. A : Screw, B: Dial indicator. C: Specimen. D: Rachet. E: Specimen mold
Fig. 2 ■ Fixture for determining properties in com pression
REPORTS OF COUNCILS AND BUREAUS ■ 1041
cator, graduated in 0.02 mm., shall be read. This value shall be reading A. Sixty seconds after appli cation of a stress of 100 G m ./cm 2., an additional load calculated to produce a total stress on the speci men of 1,000 G m ./cm .2 shall be gradually applied during an interval of 10 seconds. Thirty seconds after initiation of the stress of 1,000 G m ./cm 2., a reading of the dial indicator shall be taken. This value shall be reading B. The difference between readings A and B, divided by the original length of the specimen and multiplied by 100, shall be recorded as the percentage of strain between the stresses of 100 and 1,000 G m ./cm .2 The height of the mold (19.0 mm.) shall be considered to be the original length of the specimen. The value for strain in compression shall be the average of three deter minations and shall be recorded to the nearest 0.1 percent.
4.3.8 Dimensional stability. 4.3.8.1 Preparation of specimens. The mold (Fig. 3) shall be lubricated with silicone grease (highvacuum type) and placed on a flat surface on which two reference crosslines have been ruled. The refer-
0F RULED LINES
Fig. 4 ■ Block for detail reproduction. Width of line: A = 0.025, B = 0.050, C = 0.075, D = 0.100, E = 0.150, F = 0.200, G = 0.300
1042 ■ JADA, Vol. 74, April 1967
ence lines shall be approximately 60-degree grooves, 0.05 mm. wide. The two reference lines shall be not less than 4.5 cm. apart. The mold shall be slightly overfilled with impression material from a large standard mix. A sheet of polyethylene shall be placed over the impression material and the excess pressed out with a flat plate. Two minutes from the begin ning of mix, the mold and plates shall be placed in a 3 7± 1°C . water bath. The mold and plates shall remain in the water bath the minimum time recom mended by the manufacturer for leaving the impres sion material in the mouth (3.2.5). The polyethylene shall be stripped off and the flash trimmed away before separating the halves of the mold. 4.3.8.2 Test procedure. The specimen shall be dusted with talcum powder on the surface opposite that on which the reference marks appear and placed on a smooth glass surface that has also been dusted with talcum powder. The distance between the crosslines shall be measured to the nearest 0.01 mm. 2 minutes after removal from the water bath (reading A ). Additional measurements shall be made at 24 hours (reading B) after the initial reading. The distance between the reference lines on the plate shall be recorded as reading C. The difference between readings A and B divided by reading C and multiplied by 100 shall be recorded as the value for percentage of dimensional change. The average of three determinations shall be re corded to the nearest 0.05 percent.
4.3.9 Flow. 4.3.9.1 Preparation of specimens. Specimens shall be prepared as described in 4.3.6.1 (permanent deformation) except that on removal from the mold the specimens shall be stored at room temperature until 1 hour from the start of mix. 4.3.9.2 Test procedure. The specimens shall be placed in an instrument consisting essentially of a dial gauge graduated in 0.02 mm., mounted to a steady base. At 1 hour from the start of mix, a plate weighing 2.5± 0.5 Gm. shall be placed on top of the specimen, and the foot of the dial gauge shall be brought into contact with the plate. The force exerted by the dial gauge plus the weight of the plate shall be 100 Gm. The dial gauge shall be read 30 seconds after the foot of the gauge contacts the plate and the value recorded as reading A. A second reading shall be taken 15.0 minutes after the foot of the dial gauge contacts the plate and the value recorded as reading B. The difference between reading A and reading B divided by the original length of the specimen and multiplied by 100 shall be considered to be the percentage of flow. The height of the mold (19.0 mm.) shall be considered to be the original length of the specimen. The value for flow shall be the average of three determinations and shall be recorded to the nearest 0.1 percent. 4.3.10 Reproduction. A ring 16 mm. high and approximately 3 cm. inside diameter shall be placed
Table 1 Requirements for mixing time, working time, consistency, permanent deformation, dimensional stability, flow, and strain in compression Maximum change of dimensional stability a t 24 hours (% )
Strain in compres sion (% )
Maximum mixing time (minutes)
Minimum working time (minutes)
Diameter of consistency disk (mm.)
Maximum permanent deformation (% )
(Polysulfide base) Type 1 Class 1 Class 2 Class 3
1 1 1
3 3 4
27 ± 5 32 ± 6 40 =fc 8
4 4 4
0.40 0.40 0.40
0.2 0.2 0.2
2 to 20 2 to 20 2 to 20
(Silicone base) Type II Class 1 Class 2 Class 3
1 1 1
3 3 4
27 ± 5 32 ± 6 40 ± 8
2 2 2
0.60 0.60 0.60
0.2 0.2 0.2
2 to 20 2 to 20 2 to 20
Base
M ax imum flow 1%)
*W orking time shall be not m ore than 1 minute less than the time stated by the manufacturer.
on a test block shown in Figure 4 so that the inter section of a crossline and a groove 0.025 mm. wide is in the center of the ring. If the material adheres to the test block, the block may be lightly dusted with talcum powder and the excess talcum powder blown off. The ring shall be slightly overfilled with the mixed material from a small standard mix. A flat plate shall be placed on top and the excess material squeezed out. Two minutes from the start of mix, the entire assembly shall be placed in a water bath at 37 ± 1 °C . The assembly shall remain in the water bath the minimum tim e recommended by the manufacturer for leaving the impression material in the mouth (3.2.5). T he ring with the impression material shall be separated from the test block immediately, and the impression shall be examined under low-angle illumination without mag nification. The reproduction shall be considered to be satisfactory if the 0.025-mm.-wide line is con tinuous for the full inside diameter of the ring.
4.3.11 Compatibility. 4.3.11.1 Compatibility with gypsum. A gypsum slurry, under gentle vibration, shall be poured against the impression made in 4.3.10 within 10 minutes from the time it is separated from the test block. [The gypsum shall be unmodified alpha calcium sulfate hemihydrate adjusted for setting time if necessary (3.2.3.1). This type of calcined gypsum usually requires about 100 Gm. of powder in 30 ml. of water to produce a mix of workable consistency.] The poured impression shall be stored in air at 23.0±2.0°C . and 5 0 ± 1 0 percent relative humidity for 30 minutes. The gypsum cast shall be separated from the impression material and examined under low-angle illumination without magnification. The impression material shall be considered to be com patible with gypsum if the groove 0.025 mm. wide is reproduced continuously for the full inside diam eter of the ring. 4.3.11.2 Compatibility with metalizing baths. If the manufacturer specifies an acid copper plating bath the following test solution shall be used:
Copper plating bath Copper sulfate Sulfuric acid Phenol 90 percent Ethyl alcohol Distilled water
125 Gm. 37.5 Gm. 5 ml. 25 ml. 500 ml.
If the manufacturer specifies an alkaline silver plat ing bath the following test solution shall be used: Silver plating bath Silver cyanide Potassium cyanide Potassium carbonate Distilled water
28 Gm. 53 Gm. 42 Gm. 950 ml.
A large standard mix of impression material shall be made and spread out to form a layer approxi mately 3 mm. thick. Thirty minutes after mixing, a strip, approximately 25 mm. wide and 50 mm. long, shall be cut from the layer of material. The strip of the material shall be suspended in the metalizing bath. Approximately half of the strip shall be in the solution and half in air above the solution. After immersion for 16 hours in the solu tion, the strip shall be removed, rinsed in water, blown dry with a gentle air blast, and inspected. Discoloration and slight softening shall be accept able, but the material shall be rejected if blistering, wrinkling, gross softening, etching, sloughing, or swelling occurs. After the inspection, a mix of un modified alpha calcium sulfate hemihydrate (3.2.3.1) shall be poured over one side of the test specimen. One hour later, the impression material shall be stripped from the set stone. A slight color transfer to the stone shall be acceptable, but the material shall be rejected if a gross transfer of rubber, ad hering to the gypsum surface, occurs. 4.3.12 Deterioration (shelf life). Tubes of base and accelerator shall be stored at 60±2°C . for 7 days. Permanent deformation tests as described in 4.3.6 shall then be conducted on these materials. REPORTS OF COUNCILS AND BUREAUS ■ 1043
5. Preparation for delivery 5.1 Packaging. The material shall be supplied in sealed, airtight containers made of materials that shall not contaminate or permit the contamination of the contents. The containers shall be suited to the purpose for which they are intended. 5.2 Instructions for use. Adequate instructions (3.2.5) for the manipulation and use of the ma terial shall accompany each package.
5.3 Marking. 5.3\l Lot numbers. Each container of material shall be marked with a serial number or a combi nation of letters and numbers that refer to the manu facturer’s records for that particular lot or batch. 5.3.2 Date of manufacture. The date of m anu facture (year and month) shall bê given on each container of material as a separate item or as a part of the lot number (5.3.1). 5.3.3 Volume after mixing. The minimum volume after mixing, according to the manufacturer’s in structions (3.2.5), shall be given in legible type on
1044 ■ JADA, Vol. 74, April 1967
the container to the nearest 10 ml. 5.3.4 Type and class. The type, class (1.2), and the generic name (polysulfide or silicone) of the impression material shall be indicated on all con tainers.
6. Notes 6.1 Source of unmodified alpha calcium sulfate hemihydrate. One trade brand of unmodified alpha calcium sulfate hemihydrate is “Hydrocal B-Base” manufactured by the U. S. Gypsum Company, 300 West Adams Street, Chicago, 60606.
6.2 Instrument for measuring strain in compres sion. Working drawings of the fixture for determin ing properties in compression (Fig. 2: 4.3.7) may be obtained from the Dental Research Section, N a tional Bureau of Standards, Washington, D.C. 20234,
6.3 Conversion factors 25.4 mm. = 1 inch (°C. x 1.8) + 32°= °F . 453.59 Gm. = 1 pound
Council on Dental M a te ria ls and Devices
(Approved November, 1966. Effective November 1, 1 9 6 7 .)
1. Scope and classification T he following new A m erican D ental A ssociation specification no. 19 fo r elastom eric im pression m aterial has been approved by the C oûncil on D ental R esearch of the A m erican D en tal A sso ciation. T he A ssociation’s program fo r form ula tion and revision of specifications, form erly under th a t Council, has now been transferred to the C ouncil on D ental M aterials and Devices. T he form ulation of the specification was carried on through the Specifications C om m ittee of the D ental M aterials G roup, International A ssocia tion for D ental R esearch, and by one of its sub comm ittees. T he C ouncil wishes to acknowl edge, with thanks, the w ork of the subcom m ittee m em bers: G eorge D ickson (c h a irm a n ), N ational B ureau of Standards, W ashington, D .C .; Jam es Cresson, T he L. D . C aulk C om pany, Division of D entists’ Supply C om pany of New Y ork, M il ford, D el.; F . H . Freem an, K err M anufacturing C om pany, D etroit; E ugene M olnar, Coe L ab o ra tories, Inc., Chicago; G. E . M yers, School of D entistry, U niversity of M ichigan, A n n A rbor; G u n n ar Ryge, D ental H ealth C enter, U.S. Public H ealth Service, San Francisco; W. T . Sweeney, N ational B ureau of Standards, W ashington, D.C., and C. L. B um s (se c re ta ry ), N ational B ureau of Standards, W ashington, D .C .
1.1 Scope. This specification is for dental impres sion materials with a polysulfide or a silicone rubber base. 1.2 Types and classes. Impression materials cov ered by this specification shall be of the following types and classes: Type I. Polysulfide base Class 1. Heavy body Class 2. Regular body Class 3. Light body Type II. Silicone base Class 1. Heavy body Class 2. Regular body Class 3. Light body
2. Applicable specifications 2-1 Specifications. The following specification forms a part of this specification. American Dental Association Specification No. 2 for Casting Invest ment for Dental Gold Alloy (first revision). (Copies of American Dental Association specifications may be obtained on application to the Council on Dental Materials and Devices, American Dental Associa tion, 211 East Chicago Avenue, Chicago, 60611.) 3. Requirements 3.1 Material. Both the base and the accelerator shall be homogeneous and free of foreign materials and impurities. When mixed as directed by the man ufacturer’s instructions accompanying the package, the material shall be suitable for taking impressions in the oral cavity. 1039
3.1.1 Toxicity. The manufacturer shall submit a statement that the impression material, used accord ing to the directions supplied with the material, has no toxic effect on the normal healthy person. 3.1.2 Color. The base and accelerator shall be of contrasting colors. 3.2 Physical properties. 3.2.1 The requirements for mixing time, working time, consistency, permanent deformation, dimen sional stability, flow, and strain in compression shall be as listed in the table. 3.2.2 Reproduction. The material shall reproduce a line 0.025 mm. wide when tested by the method outlined in 4.3.10.
3.2.3 Compatibility. 3.2.3.1 Compatibility with gypsum. The material shall impart a smooth surface to and shall separate cleanly from a cast made from unmodified alpha calcium sulfate hemihydrate (6.1) to which has been added, if necessary, sufficient calcium sulfate dihydrate to adjust the setting time to 10 ± 3 minutes. The method for determining the time of setting shall be that given in American Dental Association Specification No. 2 for Casting Investment for Dental Gold Alloy (first revision). A gypsum cast poured against the material in accordance with 4.3.11.1 shall reproduce a line 0.025 mm. wide. The gypsum shall itself be capable of reproducing a line 0.025 mm. wide when allowed to harden against the test block. 3.2.3.2 Compatibility with metalizing baths. The materials shall be compatible with either acid copper plating baths or alkaline silver plating baths when tested by the method outlined in 4.3.11.2. The manu facturer’s instructions shall specify the type of plat ing bath to be used. 3.2.4 Deterioration. The permanent deformation when determined by the method outlined in 4.3.6 shall not exceed 4 percent for Type I and 2 percent for Type II materials that have been stored at 60± 2.0°C . for 7 days in accordance with 4.3.12. After storage the material shall show no gross separation. 3.2.5 Instructions for use. Instructions for use shall include the proportions of base and accelerator to give a proper mix, both by weight and by volume; mixing time; working time; type of metalizing bath to be used, and the minimum time for leaving the impression in the mouth when the material is mixed at 23.0± 2.0°C . and 5 0 ± 1 0 percent relative humidity.
4. Sampling, inspection, and testing procedures 4.1 Sampling. A sample consisting of four pack ages shall be procured at retail by a member of the American Dental Association. This sample shall be forwarded in the original unopened package or pack ages to the American Dental Association Council on Dental Materials and Devices, 211 East Chicago Avenue, Chicago, 60611. 1040 ■ JADA, Vol. 74, April 1967
4.2 Inspection. Compliance with the requirements of 3.1, 3.1.2, 3.2.5, and 5 shall be determined by visual inspection. 4.3 Physical tests. 4.3.1 Standard test conditions. All physical tests shall be made under uniform atmospheric conditions of 23.0± 2.0°C . and 5 0 ± 10percent relative humidity. Materials and test equipment shall be conditioned in the test room for not less than 10 hours before testing. The materials shall be mixed according to the manufacturer’s instructions. All test mixes shall be proportioned by weight with a weighing tolerance of ± 0.1 Gm. 4.3.2 Standard mixes. Two sizes of standard mixes shall be used depending on the size of the test speci men to be made. A small standard mix shall consist of amounts of base and accelerator to give 8± 0.5 Gm. of the mixed material. A large standard mix shall consist of amounts of base and accelerator to give 20 ± 1 Gm. of the mixed material. 4.3.3 Mixing time. Sufficient materials to make a large standard mix shall be mixed according to the manufacturer’s instructions. The mix shall be con sidered to be satisfactory if a uniform, essentially streak-free mix is obtained within 1 minute. 4.3.4 Working time. A small standard mix shall be prepared and retained on the mixing pad in a com pact layer approximately 3 mm. thick. A steel rod, 2.4 mm. in diameter with flat ends and weighing 10 Gm., shall be applied to the surface at 20-second intervals and raised slowly. The needle shall be withdrawn from the test material at approximately (no faster than) the rate at which the needle pene trated the material. The end of the rod shall be wiped clean after each application. The working time shall be recorded as the time elapsed from the start of the mix to the time at which the material fails to string and an indentation persists when the rod is withdrawn. The value for working time shall be the average of three determinations and shall be recorded to the nearest 30 seconds. 4.3.5 Consistency. A volume of 0.5 ml. of a small standard mix of material shall be deposited on a cellophane-covered glass plate. Two minutes after the start of mix, the 0.5 ml. of material shall be covered with another cellophane sheet and a glass plate (approximately 75 G m .) plus a 500-Gm. weight. At 12 minutes after the start of mix, the load (glass plus 500-Gm weight) shall be removed, and the major and minor diameters of the slumped mass of material shall be measured. The value for consistency shall be the average of three determina tions and shall be recorded to the nearest millimeter.
4.3.6 Permanent deformation. 4.3.6.1 Preparation of test specimens. Test speci mens shall be made from a small standard mix by placing a ring 30 mm. inside diameter and 16 mm. high on a flat glass or metal plate and filling the ring slightly more than half full with the impression ma-
terial. A mold, 12.7 mm. inside diameter, 25.4 mm. outside diameter, and 19 mm. high, shall be placed immediately inside the ring and forced into the material until the mold touches the plate and the material has exuded onto the top of the mold. A flat glass or metal plate shall be pressed on the top of the mold to remove excess material. At 2 minutes from the start of mix, the mold and accom panying plates shall be immersed in a 3 7± 1°C . water bath. The mold and plates shall remain in the water bath the minimum time recommended by the manufacturer for leaving the impression material in the mouth (3.2.5). One minute after removal of the specimen from the water bath, the specimen shall be tested by the method described in 4.3.6.2. [The molds may be lubricated With a silicone grease (highvacuum type) to prevent the impression material from adhering to the mold.] 4.3.6.2 Test procedure. The specimen shall be placed in an instrument consisting essentially of a dial gauge graduated in 0.02 mm., mounted to a steady base and equipped with a screw, positioned in such a manner that sufficient force can be ap plied to the specimen to produce the required amount of strain (Fig. 1). One minute after removal from the water bath, a plate weighing 2.5± 0.5 Gm. shall be placed on top of the specimen and the foot of the dial gauge shall be brought into contact with the plate. The weight of the plate plus the force of the spring in the gauge shall be 5 0 ± 5 Gm. The dial gauge shall be read 30 seconds after the foot of the gauge contacts the plate and the value recorded as reading A. The dial gauge foot shall be lowered 2.3 mm. by means of the screw and shall be main tained in this position on the specimen for 30 sec onds; then the foot of the dial gauge shall be raised and the specimen allowed to rest under no load (except that of the lightweight plate) for 30 seconds. The dial gauge foot shall again be brought into contact with the plate on the specimen for 30 sec onds and a second reading shall be taken. This value shall be recorded as reading B. The difference be tween readings A and B, divided by the original length of the specimen and multiplied by 100, shall be considered to be the percentage of permanent deformation. The height of the mold (19.0 mm.) shall be considered to be the original length of the specimen. The value for permanent deformation shall be the average of three determinations and shall be recorded to the nearest 0.1 percent. 4.3.7 Strain in compression. 4.3.7.1 Preparation o f specimens. Specimens shall be prepared as described in 4.3.6.1 (permanent deform ation). 4.3.7.2 Test procedure. Six minutes after removal from the water bath, the specimen shall be placed in a suitable instrument (Fig. 2) and shall be sub jected to a load calculated to produce a stress of 100 G m ./cm .2 Thirty seconds later, the dial indi-
Fig. 1 ■ Instrument for measuring permanent deforma tion. A : Screw, B: Dial indicator. C: Specimen. D: Rachet. E: Specimen mold
Fig. 2 ■ Fixture for determining properties in com pression
REPORTS OF COUNCILS AND BUREAUS ■ 1041
cator, graduated in 0.02 mm., shall be read. This value shall be reading A. Sixty seconds after appli cation of a stress of 100 G m ./cm 2., an additional load calculated to produce a total stress on the speci men of 1,000 G m ./cm .2 shall be gradually applied during an interval of 10 seconds. Thirty seconds after initiation of the stress of 1,000 G m ./cm 2., a reading of the dial indicator shall be taken. This value shall be reading B. The difference between readings A and B, divided by the original length of the specimen and multiplied by 100, shall be recorded as the percentage of strain between the stresses of 100 and 1,000 G m ./cm .2 The height of the mold (19.0 mm.) shall be considered to be the original length of the specimen. The value for strain in compression shall be the average of three deter minations and shall be recorded to the nearest 0.1 percent.
4.3.8 Dimensional stability. 4.3.8.1 Preparation of specimens. The mold (Fig. 3) shall be lubricated with silicone grease (highvacuum type) and placed on a flat surface on which two reference crosslines have been ruled. The refer-
0F RULED LINES
Fig. 4 ■ Block for detail reproduction. Width of line: A = 0.025, B = 0.050, C = 0.075, D = 0.100, E = 0.150, F = 0.200, G = 0.300
1042 ■ JADA, Vol. 74, April 1967
ence lines shall be approximately 60-degree grooves, 0.05 mm. wide. The two reference lines shall be not less than 4.5 cm. apart. The mold shall be slightly overfilled with impression material from a large standard mix. A sheet of polyethylene shall be placed over the impression material and the excess pressed out with a flat plate. Two minutes from the begin ning of mix, the mold and plates shall be placed in a 3 7± 1°C . water bath. The mold and plates shall remain in the water bath the minimum time recom mended by the manufacturer for leaving the impres sion material in the mouth (3.2.5). The polyethylene shall be stripped off and the flash trimmed away before separating the halves of the mold. 4.3.8.2 Test procedure. The specimen shall be dusted with talcum powder on the surface opposite that on which the reference marks appear and placed on a smooth glass surface that has also been dusted with talcum powder. The distance between the crosslines shall be measured to the nearest 0.01 mm. 2 minutes after removal from the water bath (reading A ). Additional measurements shall be made at 24 hours (reading B) after the initial reading. The distance between the reference lines on the plate shall be recorded as reading C. The difference between readings A and B divided by reading C and multiplied by 100 shall be recorded as the value for percentage of dimensional change. The average of three determinations shall be re corded to the nearest 0.05 percent.
4.3.9 Flow. 4.3.9.1 Preparation of specimens. Specimens shall be prepared as described in 4.3.6.1 (permanent deformation) except that on removal from the mold the specimens shall be stored at room temperature until 1 hour from the start of mix. 4.3.9.2 Test procedure. The specimens shall be placed in an instrument consisting essentially of a dial gauge graduated in 0.02 mm., mounted to a steady base. At 1 hour from the start of mix, a plate weighing 2.5± 0.5 Gm. shall be placed on top of the specimen, and the foot of the dial gauge shall be brought into contact with the plate. The force exerted by the dial gauge plus the weight of the plate shall be 100 Gm. The dial gauge shall be read 30 seconds after the foot of the gauge contacts the plate and the value recorded as reading A. A second reading shall be taken 15.0 minutes after the foot of the dial gauge contacts the plate and the value recorded as reading B. The difference between reading A and reading B divided by the original length of the specimen and multiplied by 100 shall be considered to be the percentage of flow. The height of the mold (19.0 mm.) shall be considered to be the original length of the specimen. The value for flow shall be the average of three determinations and shall be recorded to the nearest 0.1 percent. 4.3.10 Reproduction. A ring 16 mm. high and approximately 3 cm. inside diameter shall be placed
Table 1 Requirements for mixing time, working time, consistency, permanent deformation, dimensional stability, flow, and strain in compression Maximum change of dimensional stability a t 24 hours (% )
Strain in compres sion (% )
Maximum mixing time (minutes)
Minimum working time (minutes)
Diameter of consistency disk (mm.)
Maximum permanent deformation (% )
(Polysulfide base) Type 1 Class 1 Class 2 Class 3
1 1 1
3 3 4
27 ± 5 32 ± 6 40 =fc 8
4 4 4
0.40 0.40 0.40
0.2 0.2 0.2
2 to 20 2 to 20 2 to 20
(Silicone base) Type II Class 1 Class 2 Class 3
1 1 1
3 3 4
27 ± 5 32 ± 6 40 ± 8
2 2 2
0.60 0.60 0.60
0.2 0.2 0.2
2 to 20 2 to 20 2 to 20
Base
M ax imum flow 1%)
*W orking time shall be not m ore than 1 minute less than the time stated by the manufacturer.
on a test block shown in Figure 4 so that the inter section of a crossline and a groove 0.025 mm. wide is in the center of the ring. If the material adheres to the test block, the block may be lightly dusted with talcum powder and the excess talcum powder blown off. The ring shall be slightly overfilled with the mixed material from a small standard mix. A flat plate shall be placed on top and the excess material squeezed out. Two minutes from the start of mix, the entire assembly shall be placed in a water bath at 37 ± 1 °C . The assembly shall remain in the water bath the minimum tim e recommended by the manufacturer for leaving the impression material in the mouth (3.2.5). T he ring with the impression material shall be separated from the test block immediately, and the impression shall be examined under low-angle illumination without mag nification. The reproduction shall be considered to be satisfactory if the 0.025-mm.-wide line is con tinuous for the full inside diameter of the ring.
4.3.11 Compatibility. 4.3.11.1 Compatibility with gypsum. A gypsum slurry, under gentle vibration, shall be poured against the impression made in 4.3.10 within 10 minutes from the time it is separated from the test block. [The gypsum shall be unmodified alpha calcium sulfate hemihydrate adjusted for setting time if necessary (3.2.3.1). This type of calcined gypsum usually requires about 100 Gm. of powder in 30 ml. of water to produce a mix of workable consistency.] The poured impression shall be stored in air at 23.0±2.0°C . and 5 0 ± 1 0 percent relative humidity for 30 minutes. The gypsum cast shall be separated from the impression material and examined under low-angle illumination without magnification. The impression material shall be considered to be com patible with gypsum if the groove 0.025 mm. wide is reproduced continuously for the full inside diam eter of the ring. 4.3.11.2 Compatibility with metalizing baths. If the manufacturer specifies an acid copper plating bath the following test solution shall be used:
Copper plating bath Copper sulfate Sulfuric acid Phenol 90 percent Ethyl alcohol Distilled water
125 Gm. 37.5 Gm. 5 ml. 25 ml. 500 ml.
If the manufacturer specifies an alkaline silver plat ing bath the following test solution shall be used: Silver plating bath Silver cyanide Potassium cyanide Potassium carbonate Distilled water
28 Gm. 53 Gm. 42 Gm. 950 ml.
A large standard mix of impression material shall be made and spread out to form a layer approxi mately 3 mm. thick. Thirty minutes after mixing, a strip, approximately 25 mm. wide and 50 mm. long, shall be cut from the layer of material. The strip of the material shall be suspended in the metalizing bath. Approximately half of the strip shall be in the solution and half in air above the solution. After immersion for 16 hours in the solu tion, the strip shall be removed, rinsed in water, blown dry with a gentle air blast, and inspected. Discoloration and slight softening shall be accept able, but the material shall be rejected if blistering, wrinkling, gross softening, etching, sloughing, or swelling occurs. After the inspection, a mix of un modified alpha calcium sulfate hemihydrate (3.2.3.1) shall be poured over one side of the test specimen. One hour later, the impression material shall be stripped from the set stone. A slight color transfer to the stone shall be acceptable, but the material shall be rejected if a gross transfer of rubber, ad hering to the gypsum surface, occurs. 4.3.12 Deterioration (shelf life). Tubes of base and accelerator shall be stored at 60±2°C . for 7 days. Permanent deformation tests as described in 4.3.6 shall then be conducted on these materials. REPORTS OF COUNCILS AND BUREAUS ■ 1043
5. Preparation for delivery 5.1 Packaging. The material shall be supplied in sealed, airtight containers made of materials that shall not contaminate or permit the contamination of the contents. The containers shall be suited to the purpose for which they are intended. 5.2 Instructions for use. Adequate instructions (3.2.5) for the manipulation and use of the ma terial shall accompany each package.
5.3 Marking. 5.3\l Lot numbers. Each container of material shall be marked with a serial number or a combi nation of letters and numbers that refer to the manu facturer’s records for that particular lot or batch. 5.3.2 Date of manufacture. The date of m anu facture (year and month) shall bê given on each container of material as a separate item or as a part of the lot number (5.3.1). 5.3.3 Volume after mixing. The minimum volume after mixing, according to the manufacturer’s in structions (3.2.5), shall be given in legible type on
1044 ■ JADA, Vol. 74, April 1967
the container to the nearest 10 ml. 5.3.4 Type and class. The type, class (1.2), and the generic name (polysulfide or silicone) of the impression material shall be indicated on all con tainers.
6. Notes 6.1 Source of unmodified alpha calcium sulfate hemihydrate. One trade brand of unmodified alpha calcium sulfate hemihydrate is “Hydrocal B-Base” manufactured by the U. S. Gypsum Company, 300 West Adams Street, Chicago, 60606.
6.2 Instrument for measuring strain in compres sion. Working drawings of the fixture for determin ing properties in compression (Fig. 2: 4.3.7) may be obtained from the Dental Research Section, N a tional Bureau of Standards, Washington, D.C. 20234,
6.3 Conversion factors 25.4 mm. = 1 inch (°C. x 1.8) + 32°= °F . 453.59 Gm. = 1 pound