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Proposed specification for impression material; synthetic rubber base, dental
Proposed specification for impression m aterial; synthetic rubber base, dental
W. A, C. Miller, J r.* D.D .S.; W. C. Hansen;f B.S.; George Dickson, f M .A ., and. W. T. Sweeney,% A.B., Washington, D. C.
This proposed specification is based to a large extent on data reported in a paper by the same authors.1 Test procedures for permanent deformation and strain are modifications o f procedures described in Federal Specification U -I-496a for Im pression Material, Hydrocolloidal, Agar Type, Dental; Federal Specification U -I498 for Impression Material, Hydrocol loidal, Alginate Type, Dental; and Amer ican Dental Association Specification No. 11 for Hydrocolloidal Impression Mate rial, Agar Type. T w o types of material, silicone base and polysulfide base, are covered in the specification. Although all requirements with the exception of composition are identical for both types, mixing and handling characteristics do differ and the type to be obtained is left to the choice o f the purchaser. Determinations o f permanent deforma tion and strain at 8 to 10 minutes after the material is mixed serve indirectly as requirements that the material set within this period. A requirement for dimen sional stability is included since these materials have been recommended for procedures where a considerable delay may occur between making the impres sion and pouring the cast.
1.
SCOPE AND CLASSIFICATION
1.1 Scope. This specification covers dental impression materials with a syn thetic rubber base, intended primarily for taking oral impressions. 1.2 Classification. 1.2.1 Grade and type. Impression materials covered by this specification shall be of one grade and o f the following types as specified in the invitation for bids: Type I, Silicone base; Type II, Polysulfide base. 2.
APPLICABLE SPECIFICATIONS
AND STANDARDS
2.1 The following Federal Specifica tions shall form a part of this specifica tion: U-S-746b Stone; Artificial, QuickSetting (Dental) and U -I-498 Impres sion Material, Hydrocolloidal, Alginate Type. 3.
REQUIREMENTS
3.1 Material. Both the base material and the accelerator shall be uniform in consistency and free o f foreign materials and impurities. The manufacturer shall furnish a certificate stating that the mate
M IL L E R A N D O T H E R S .
rial contains no poisonous ingredients in sufficient concentration to be harmful to human beings when used as directed. 3.1.1 Composition. Type I. Silicone base materials shall not reveal any sulfur content when tested by the method in 4.3.1. Type II. Polysulfide base materials shall reveal a sulfur content when tested by the method in 4.3.1. 3.1.2 Suitability. The material when mixed as directed by the manufacturer’s instructions accompanying the package, shall be suitable for taking impressions in the oral cavity. 3.2 Mixing time. The mixing time shall be stated in the manufacturer’s di rections and shall not exceed one minute. 3.3 Working time. The working time when determined by the method in 4.4.2 shall be not less than 2.0 minutes or less than the manufacturer’s stated working time, whichever is greater. 3.4 Detail reproduction. The material shall reproduce a groove 0.0015 inch in width when tested by the method in 4.4.3. 3.5 Compatibility. The material shall be compatible with dental artificial stone when tested by the method in 4.4.4. 3.6 Permanent deformation after com pression. The permanent deformation when tested by the method in 4.4.5 shall not exceed 4.0 per cent. 3.7 Strain in compression. The strain in compression shall be not less than 4.0 per cent nor more than 30.0 per cent when tested by the method in 4.4.6. 3.8 Dimensional stability. The change in linear dimensions shall be not more than 0.2 per cent when measured by the method in 4.4.7. 3.9 Deterioration. The permanent deformation when tested by the method in 4.4.5 shall not exceed 4.0 per cent after the material has been stored at 60° ± 1°C. (140° ± 1.8°F.) for seven days in accordance with 4.4.8. 3.10 Instructions for use. Instructions shall include the proportions of material needed for proper mixing, the mixing
. V O L U M E 60, F E B R U A R Y I960 • 97/225
time, the working time at 23° ± 1°C. and 50 ± 4 per cent relative humidity and the minimum time for leaving the impression in the mouth. 4.
SAM PLIN G, IN SPECTION
AND T E ST PROCEDURES
4.1 Sampling. Unless otherwise speci fied, a sample consisting o f four packages shall be taken at random from each lot or batch o f material in the delivery. 4.2 Inspection. Compliance with the requirements of 3.1, 3.1.2, 3.2, 3.10 and 5 shall be determined by visual inspection. 4.3 Chemical tests. 4.3.1 Composition. Three to five grams of base material shall be placed into the bottom o f a small glass container. A piece of suitably bent glass tubing shall be connected to the top o f the container. The free end of the glass tubing shall be immersed in approximately 10 ml. o f 5 per cent Pb (A c) 2 which has been acidified with 1 to 2 drops of acetic acid. The base material shall be heated carefully in the glass container until a visible vapor forms. Heating shall be continued for 2 minutes or until a black precipitate forms in the P b (A c ) 2, whichever occurs first. Forma tion of a black precipitate shall be con sidered indicative o f sulfur content. 4.4 Physical tests. 4.4.1 Standard testing conditions. All physical tests shall be made under uni form atmospheric conditions of 23° ± 1.0°C. (73.4° ± 1.8°F.) temperature and 50 ± 4 per cent relative humidity. Mate rial before mixing and testing equipment shall be conditioned in the testing room for not less than 12 hours. Material shall be mixed according to the manufacturer’s instructions. 4.4.2 Working time. Compliance with the requirement o f 3.3 shall be de termined by a penetration test. The pene trometer shall consist o f a flat-ended cylindrical needle 4 mm. in diameter, through which a load o f 50 grams is ap plied to the specimen, and shall be
98/224 • T H E J O U R N A L O F T H E A M E R I C A N D E N T A L A S S O C I A T I O N
equipped with a dial indicator graduated with the working time requirement. 4.4.3 Detail reproduction. The ring in thousandths o f an inch for indicating the depth of penetration. A smooth flat ' specified in 4.4.2 shall be positioned on plate shall be placed under the needle the test block shown in Figure 1, so that the intersection of a crossline and a and a fiducial reading (A ) made. A ring, Ys inch high and approximately 1 '/s 0.0015 inch width groove is in the center inches inside diameter shall be placed o f the ring. The ring shall be slightly over upon the plate beneath the needle and filled with a mix of impression material. filled with material. The top surface shall A flat plate shall be placed on top and the be leveled. At 2.0 minutes from the start excess material squeezed out. At 2 min of the mix, or at the manufacturer’s utes from the start of mix, the entire assembly shall be placed in a water stated working time, whichever is greater, the needle shall be placed in contact with bath maintained at a temperature of the top surface o f the specimen and re 37° ± 1°C. At 7.5 minutes from the leased. At 10 seconds after release, an start of the mix, the assembly shall be removed from the bath. The ring with indicator reading (B) shall be made. The difference between the two readings the impression material shall be separated (B-A ) shall be recorded to the nearest from the test block immediately, and the 0.001 inch. If the average difference for impression shall be examined under low 3 specimens is not more than 0.010 inch, angle illumination without magnifica the material shall be considered to comply tion. The reproduction shall be con-
F
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• T e s t b l o c k f o r d e t a il r e p r o d u c t i o n t e st
M IL L E R A N D O T H E R S . . . V O L U M E 60, F E B R U A R Y I960 • 99/227
sidered to be satisfactory if the 0.0015 inch width groove is continuous for the full inside diameter of the ring. One specimen shall be tested. 4.4.4 Compatibility. An artificial stone cast shall be poured against the impres sion made in 4.4.3 within 10 minutes from the time it is separated from the test block. The artificial stone used shall be capable of reproducing a groove 0.0015 inch in width when tested against a test block similar to that shown in Figure 1 and shall comply with Federal Specification U-S-746b. The impression materials shall be separated after the stone has set. The cast shall be examined under low angle illumination without magnification. The impression material shall be considered to be compatible with the artificial stone if the 0.0015 inch width groove is repro duced in the gypsum continuously for the full inside diameter o f the ring. One specimen shall be tested. 4.4.5 Permanent deformation. 4.4.5.1 Preparation of the test speci men. A lubricated metal ring mold, 0.5 inch inside diameter, 1 inch outside diameter, and 0.75 inch high, shall be overfilled with impression material. The mold shall be placed on a flat plate and another flat plate shall be pressed on top of the mold to remove the excess material. At 2.0 minutes from the beginning of the mix the mold and accompanying plates shall be immersed in a 37° ± 1°C. water bath. At 7.5 minutes from the beginning of the mix the specimen shall be removed from the water bath and separated from the mold, and at 8.0 minutes it shall be tested by the method described in 4.4.5.2. 4.4.5.2 Test procedure. The speci men shall be placed in an instrument con sisting essentially of a dial gauge grad uated in thousandths o f an inch, mounted to a steady base and equipped with a screw positioned in such a manner that sufficient pressure can be applied to the specimen to produce the required amount o f strain as described in Federal Specifi cation U-I-498. At 8.0 minutes from the
beginning of the mix a lightweight plate shall be placed on top o f the specimen and the foot of the dial gauge shall be brought into contact with the plate. The weight o f the plate plus the force o f the spring in the gauge shall be 50 ± 5 grams. , 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 0.090 inch by means of the screw and shall be maintained in this position on the specimen for 1.0 minute, then the foot of the dial gauge shall be raised and the specimen allowed to rest under no load for 1.0 minute. The dial gauge foot shall again be brought into contact with the plate on the specimen for 30 seconds and a second reading shall be taken. This value shall be recorded as “ Reading B.” The difference between “ Reading A ” and “ Reading B” in inches, divided by 0.75 inch (considered to be the original height of the specimen) and multiplied by 100 shall be considered to be the per cent of permanent deformation. The value shall be reported as the average of tests on three specimens and shall be recorded to the nearest 0.1 per cent. 4.4.6 Strain in compression. A speci men prepared as described in 4.4.5.1 shall be transferred to an appropriate instru ment equipped with a dial gauge that will indicate the height of the specimen to one thousandth inch, and at 8.0 min utes from beginning of the mix shall be subjected to a load calculated to produce a stress of 100 grams per square centi meter (1.42 pounds per square inch). Thirty seconds later the dial indicator shall be read. This value shall be desig nated as “ Reading A .” Sixty seconds after application of a stress of 100 grams per square centimeter, an additional load calculated to produce a total stress on the specimen of 1000 grams per square centi meter (14.2 pounds per square inch) shall be applied gradually during an in terval of 10 seconds. Thirty seconds after initiation of the application of this load,
100/228 • T H E J O U R N A L O F T H E A M E R I C A N D E N T A L A S S O C I A T I O N
A L L D I M E N S I O N S IN I N C H E S
Fig. 2
M o ld
fo r dimensional stab ility specim en
a reading o f the dial indicator shall be taken. This reading shall be designated as “ Reading B.” T h e difference between “ Reading A ” and “ Reading B” in inches, divided by 0.75 inch (considered to be the original height o f the specimen) and multiplied by 100 shall be considered to be the per cent o f strain. T h e value shall be reported as the aver age o f tests on three specimens and shall be recorded to the nearest 0.1 per cent. 4.4.7 Dimensional stability. 4.4.7.1 Preparation o f the mold. Th e mold shown in Figure 2 may be made from metal, polymethyl methacrylate or Teflon. 4.4.7.2 Preparation o f the specimen. T h e mold shall be lubricated with silicone grease and placed on a flat surface which has been covered with a sheet o f 0.001 inch-thick polyethylene. Small pieces of metal on which crosslines have been ruled shall be placed with ruled lines down as near as possible to each end o f the mold. T h e two pieces shall be not less than 1.75 inches apart. T h e metal pieces may be held in position with minute quantities o f utility wax or similar substances. Th e mold shall be slightly overfilled with im pression material. Another sheet o f 0.001 inch-thick polyethylene shall be placed
over the impression material and the ex cess pressed out with a flat plate. A t 12.0 minutes from the beginning o f the mix, the polyethylene shall be stripped o ff and the flash trimmed away before separating the halves o f the mold. 4.4.7.3 Test procedure. T h e specimen shall be dusted with talc on the surface opposite that in which the metal pieces are imbedded, and placed on a smooth glass surface which has also been dusted with talc. T h e distance between the cross lines on the two pieces o f metal shall be measured with a measuring microscope to the nearest 0.001 inch 15.0 minutes after the beginning o f the mix and 6 hours after the beginning o f the mix. Th e difference between the two measure ments, divided by the 15.0 minute measurement and multiplied by 100, shall be considered to be the change in linear dimension in per cent. T h e value shall be reported as the average of tests on three specimens and shall be recorded to the nearest 0.1 per cent. 4.4.8 Deterioration test. O ne un opened package o f the material shall be stored at 60° ± 1°C. (140° ± 1.8°F.) for one week. A t the end o f the storage period, test specimens shall be made and
M IL L E R A N D O T H E R S . . . V O L U M E 60, F E B R U A R Y I960 • 101/22*
tested for permanent deformation in ac in each package shall be such that, when cordance with 4.4.5. the contents are mixed in accordance 4.5 Compliance. Each lot or batch ofwith the manufacturer’s directions, the material included in the delivery shall resulting mix shall have a volume o f not be accepted or rejected individually. If less than 130 cc. when measured to the the sample (4.1) complies with all o f the nearest cubic centimeter. requirements of this specification, the lot 5.1.3 Lot numbers. Each container or batch shall be accepted. If the sample shall be marked with a serial number or fails to comply with any requirement, combination o f letters and numbers which two additional samples shall be tested. If shall refer to the manufacturer’s records both comply with all requirements, the lot for the particular lot or batch o f impres or batch shall be considered to comply sion material. with the specification. 5.1.4 Date o f manufacture. The date o f manufacture (year and month) shall be indicated on the container as a sepa 5. PREPARATION FOR DELIVERY rate item or a part of the lot number (5.1.3). 5.1 Packaging. The material shall be supplied in sealed airtight containers from which no leakage shall be dis cernible. 5.1.1 Instructions. Adequate instruc •G u e st worker, U. S. A i r Force, dental research se c tions for manipulation and use of the tion, N a tio n a l Bureau o f Sta n d a rd s. fPhysicist, dental research section, N a t io n a l .Bureau o f Stand ard s. material shall accompany each package. JC hief, dental research section, N a tio n a l Bureau of (See 3.10.) Stan d ard s. I. M ille r, W . A . C ., Jr., a nd others. Physical p ro p e r 5.1.2 Amount o f material in indi ties o f syn th e tic-rub be r-base dental im pre ssio n m a te vidual package. The amount of material rials. J .A .D .A . 60:211 Feb. I960.
Oral Examinations • For early cancer diagnosis, inclusion of an oral denial examination in the physical evaluation given patients on hospital admission is proving valuable, according to Veterans Administration. V A hospitals adopted the technic about two and a half years ago, and have since reported some 700 cases of malignancies of the mouth, tongue and throat which might otherwise have developed unnoticed until too late for successful treatment. Hospitals 33:21:66 Nov. 1, 1959.
W. A, C. Miller, J r.* D.D .S.; W. C. Hansen;f B.S.; George Dickson, f M .A ., and. W. T. Sweeney,% A.B., Washington, D. C.
This proposed specification is based to a large extent on data reported in a paper by the same authors.1 Test procedures for permanent deformation and strain are modifications o f procedures described in Federal Specification U -I-496a for Im pression Material, Hydrocolloidal, Agar Type, Dental; Federal Specification U -I498 for Impression Material, Hydrocol loidal, Alginate Type, Dental; and Amer ican Dental Association Specification No. 11 for Hydrocolloidal Impression Mate rial, Agar Type. T w o types of material, silicone base and polysulfide base, are covered in the specification. Although all requirements with the exception of composition are identical for both types, mixing and handling characteristics do differ and the type to be obtained is left to the choice o f the purchaser. Determinations o f permanent deforma tion and strain at 8 to 10 minutes after the material is mixed serve indirectly as requirements that the material set within this period. A requirement for dimen sional stability is included since these materials have been recommended for procedures where a considerable delay may occur between making the impres sion and pouring the cast.
1.
SCOPE AND CLASSIFICATION
1.1 Scope. This specification covers dental impression materials with a syn thetic rubber base, intended primarily for taking oral impressions. 1.2 Classification. 1.2.1 Grade and type. Impression materials covered by this specification shall be of one grade and o f the following types as specified in the invitation for bids: Type I, Silicone base; Type II, Polysulfide base. 2.
APPLICABLE SPECIFICATIONS
AND STANDARDS
2.1 The following Federal Specifica tions shall form a part of this specifica tion: U-S-746b Stone; Artificial, QuickSetting (Dental) and U -I-498 Impres sion Material, Hydrocolloidal, Alginate Type. 3.
REQUIREMENTS
3.1 Material. Both the base material and the accelerator shall be uniform in consistency and free o f foreign materials and impurities. The manufacturer shall furnish a certificate stating that the mate
M IL L E R A N D O T H E R S .
rial contains no poisonous ingredients in sufficient concentration to be harmful to human beings when used as directed. 3.1.1 Composition. Type I. Silicone base materials shall not reveal any sulfur content when tested by the method in 4.3.1. Type II. Polysulfide base materials shall reveal a sulfur content when tested by the method in 4.3.1. 3.1.2 Suitability. The material when mixed as directed by the manufacturer’s instructions accompanying the package, shall be suitable for taking impressions in the oral cavity. 3.2 Mixing time. The mixing time shall be stated in the manufacturer’s di rections and shall not exceed one minute. 3.3 Working time. The working time when determined by the method in 4.4.2 shall be not less than 2.0 minutes or less than the manufacturer’s stated working time, whichever is greater. 3.4 Detail reproduction. The material shall reproduce a groove 0.0015 inch in width when tested by the method in 4.4.3. 3.5 Compatibility. The material shall be compatible with dental artificial stone when tested by the method in 4.4.4. 3.6 Permanent deformation after com pression. The permanent deformation when tested by the method in 4.4.5 shall not exceed 4.0 per cent. 3.7 Strain in compression. The strain in compression shall be not less than 4.0 per cent nor more than 30.0 per cent when tested by the method in 4.4.6. 3.8 Dimensional stability. The change in linear dimensions shall be not more than 0.2 per cent when measured by the method in 4.4.7. 3.9 Deterioration. The permanent deformation when tested by the method in 4.4.5 shall not exceed 4.0 per cent after the material has been stored at 60° ± 1°C. (140° ± 1.8°F.) for seven days in accordance with 4.4.8. 3.10 Instructions for use. Instructions shall include the proportions of material needed for proper mixing, the mixing
. V O L U M E 60, F E B R U A R Y I960 • 97/225
time, the working time at 23° ± 1°C. and 50 ± 4 per cent relative humidity and the minimum time for leaving the impression in the mouth. 4.
SAM PLIN G, IN SPECTION
AND T E ST PROCEDURES
4.1 Sampling. Unless otherwise speci fied, a sample consisting o f four packages shall be taken at random from each lot or batch o f material in the delivery. 4.2 Inspection. Compliance with the requirements of 3.1, 3.1.2, 3.2, 3.10 and 5 shall be determined by visual inspection. 4.3 Chemical tests. 4.3.1 Composition. Three to five grams of base material shall be placed into the bottom o f a small glass container. A piece of suitably bent glass tubing shall be connected to the top o f the container. The free end of the glass tubing shall be immersed in approximately 10 ml. o f 5 per cent Pb (A c) 2 which has been acidified with 1 to 2 drops of acetic acid. The base material shall be heated carefully in the glass container until a visible vapor forms. Heating shall be continued for 2 minutes or until a black precipitate forms in the P b (A c ) 2, whichever occurs first. Forma tion of a black precipitate shall be con sidered indicative o f sulfur content. 4.4 Physical tests. 4.4.1 Standard testing conditions. All physical tests shall be made under uni form atmospheric conditions of 23° ± 1.0°C. (73.4° ± 1.8°F.) temperature and 50 ± 4 per cent relative humidity. Mate rial before mixing and testing equipment shall be conditioned in the testing room for not less than 12 hours. Material shall be mixed according to the manufacturer’s instructions. 4.4.2 Working time. Compliance with the requirement o f 3.3 shall be de termined by a penetration test. The pene trometer shall consist o f a flat-ended cylindrical needle 4 mm. in diameter, through which a load o f 50 grams is ap plied to the specimen, and shall be
98/224 • T H E J O U R N A L O F T H E A M E R I C A N D E N T A L A S S O C I A T I O N
equipped with a dial indicator graduated with the working time requirement. 4.4.3 Detail reproduction. The ring in thousandths o f an inch for indicating the depth of penetration. A smooth flat ' specified in 4.4.2 shall be positioned on plate shall be placed under the needle the test block shown in Figure 1, so that the intersection of a crossline and a and a fiducial reading (A ) made. A ring, Ys inch high and approximately 1 '/s 0.0015 inch width groove is in the center inches inside diameter shall be placed o f the ring. The ring shall be slightly over upon the plate beneath the needle and filled with a mix of impression material. filled with material. The top surface shall A flat plate shall be placed on top and the be leveled. At 2.0 minutes from the start excess material squeezed out. At 2 min of the mix, or at the manufacturer’s utes from the start of mix, the entire assembly shall be placed in a water stated working time, whichever is greater, the needle shall be placed in contact with bath maintained at a temperature of the top surface o f the specimen and re 37° ± 1°C. At 7.5 minutes from the leased. At 10 seconds after release, an start of the mix, the assembly shall be removed from the bath. The ring with indicator reading (B) shall be made. The difference between the two readings the impression material shall be separated (B-A ) shall be recorded to the nearest from the test block immediately, and the 0.001 inch. If the average difference for impression shall be examined under low 3 specimens is not more than 0.010 inch, angle illumination without magnifica the material shall be considered to comply tion. The reproduction shall be con-
F
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OF RULED LIN E S F ig . I
• T e s t b l o c k f o r d e t a il r e p r o d u c t i o n t e st
M IL L E R A N D O T H E R S . . . V O L U M E 60, F E B R U A R Y I960 • 99/227
sidered to be satisfactory if the 0.0015 inch width groove is continuous for the full inside diameter of the ring. One specimen shall be tested. 4.4.4 Compatibility. An artificial stone cast shall be poured against the impres sion made in 4.4.3 within 10 minutes from the time it is separated from the test block. The artificial stone used shall be capable of reproducing a groove 0.0015 inch in width when tested against a test block similar to that shown in Figure 1 and shall comply with Federal Specification U-S-746b. The impression materials shall be separated after the stone has set. The cast shall be examined under low angle illumination without magnification. The impression material shall be considered to be compatible with the artificial stone if the 0.0015 inch width groove is repro duced in the gypsum continuously for the full inside diameter o f the ring. One specimen shall be tested. 4.4.5 Permanent deformation. 4.4.5.1 Preparation of the test speci men. A lubricated metal ring mold, 0.5 inch inside diameter, 1 inch outside diameter, and 0.75 inch high, shall be overfilled with impression material. The mold shall be placed on a flat plate and another flat plate shall be pressed on top of the mold to remove the excess material. At 2.0 minutes from the beginning of the mix the mold and accompanying plates shall be immersed in a 37° ± 1°C. water bath. At 7.5 minutes from the beginning of the mix the specimen shall be removed from the water bath and separated from the mold, and at 8.0 minutes it shall be tested by the method described in 4.4.5.2. 4.4.5.2 Test procedure. The speci men shall be placed in an instrument con sisting essentially of a dial gauge grad uated in thousandths o f an inch, mounted to a steady base and equipped with a screw positioned in such a manner that sufficient pressure can be applied to the specimen to produce the required amount o f strain as described in Federal Specifi cation U-I-498. At 8.0 minutes from the
beginning of the mix a lightweight plate shall be placed on top o f the specimen and the foot of the dial gauge shall be brought into contact with the plate. The weight o f the plate plus the force o f the spring in the gauge shall be 50 ± 5 grams. , 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 0.090 inch by means of the screw and shall be maintained in this position on the specimen for 1.0 minute, then the foot of the dial gauge shall be raised and the specimen allowed to rest under no load for 1.0 minute. The dial gauge foot shall again be brought into contact with the plate on the specimen for 30 seconds and a second reading shall be taken. This value shall be recorded as “ Reading B.” The difference between “ Reading A ” and “ Reading B” in inches, divided by 0.75 inch (considered to be the original height of the specimen) and multiplied by 100 shall be considered to be the per cent of permanent deformation. The value shall be reported as the average of tests on three specimens and shall be recorded to the nearest 0.1 per cent. 4.4.6 Strain in compression. A speci men prepared as described in 4.4.5.1 shall be transferred to an appropriate instru ment equipped with a dial gauge that will indicate the height of the specimen to one thousandth inch, and at 8.0 min utes from beginning of the mix shall be subjected to a load calculated to produce a stress of 100 grams per square centi meter (1.42 pounds per square inch). Thirty seconds later the dial indicator shall be read. This value shall be desig nated as “ Reading A .” Sixty seconds after application of a stress of 100 grams per square centimeter, an additional load calculated to produce a total stress on the specimen of 1000 grams per square centi meter (14.2 pounds per square inch) shall be applied gradually during an in terval of 10 seconds. Thirty seconds after initiation of the application of this load,
100/228 • T H E J O U R N A L O F T H E A M E R I C A N D E N T A L A S S O C I A T I O N
A L L D I M E N S I O N S IN I N C H E S
Fig. 2
M o ld
fo r dimensional stab ility specim en
a reading o f the dial indicator shall be taken. This reading shall be designated as “ Reading B.” T h e difference between “ Reading A ” and “ Reading B” in inches, divided by 0.75 inch (considered to be the original height o f the specimen) and multiplied by 100 shall be considered to be the per cent o f strain. T h e value shall be reported as the aver age o f tests on three specimens and shall be recorded to the nearest 0.1 per cent. 4.4.7 Dimensional stability. 4.4.7.1 Preparation o f the mold. Th e mold shown in Figure 2 may be made from metal, polymethyl methacrylate or Teflon. 4.4.7.2 Preparation o f the specimen. T h e mold shall be lubricated with silicone grease and placed on a flat surface which has been covered with a sheet o f 0.001 inch-thick polyethylene. Small pieces of metal on which crosslines have been ruled shall be placed with ruled lines down as near as possible to each end o f the mold. T h e two pieces shall be not less than 1.75 inches apart. T h e metal pieces may be held in position with minute quantities o f utility wax or similar substances. Th e mold shall be slightly overfilled with im pression material. Another sheet o f 0.001 inch-thick polyethylene shall be placed
over the impression material and the ex cess pressed out with a flat plate. A t 12.0 minutes from the beginning o f the mix, the polyethylene shall be stripped o ff and the flash trimmed away before separating the halves o f the mold. 4.4.7.3 Test procedure. T h e specimen shall be dusted with talc on the surface opposite that in which the metal pieces are imbedded, and placed on a smooth glass surface which has also been dusted with talc. T h e distance between the cross lines on the two pieces o f metal shall be measured with a measuring microscope to the nearest 0.001 inch 15.0 minutes after the beginning o f the mix and 6 hours after the beginning o f the mix. Th e difference between the two measure ments, divided by the 15.0 minute measurement and multiplied by 100, shall be considered to be the change in linear dimension in per cent. T h e value shall be reported as the average of tests on three specimens and shall be recorded to the nearest 0.1 per cent. 4.4.8 Deterioration test. O ne un opened package o f the material shall be stored at 60° ± 1°C. (140° ± 1.8°F.) for one week. A t the end o f the storage period, test specimens shall be made and
M IL L E R A N D O T H E R S . . . V O L U M E 60, F E B R U A R Y I960 • 101/22*
tested for permanent deformation in ac in each package shall be such that, when cordance with 4.4.5. the contents are mixed in accordance 4.5 Compliance. Each lot or batch ofwith the manufacturer’s directions, the material included in the delivery shall resulting mix shall have a volume o f not be accepted or rejected individually. If less than 130 cc. when measured to the the sample (4.1) complies with all o f the nearest cubic centimeter. requirements of this specification, the lot 5.1.3 Lot numbers. Each container or batch shall be accepted. If the sample shall be marked with a serial number or fails to comply with any requirement, combination o f letters and numbers which two additional samples shall be tested. If shall refer to the manufacturer’s records both comply with all requirements, the lot for the particular lot or batch o f impres or batch shall be considered to comply sion material. with the specification. 5.1.4 Date o f manufacture. The date o f manufacture (year and month) shall be indicated on the container as a sepa 5. PREPARATION FOR DELIVERY rate item or a part of the lot number (5.1.3). 5.1 Packaging. The material shall be supplied in sealed airtight containers from which no leakage shall be dis cernible. 5.1.1 Instructions. Adequate instruc •G u e st worker, U. S. A i r Force, dental research se c tions for manipulation and use of the tion, N a tio n a l Bureau o f Sta n d a rd s. fPhysicist, dental research section, N a t io n a l .Bureau o f Stand ard s. material shall accompany each package. JC hief, dental research section, N a tio n a l Bureau of (See 3.10.) Stan d ard s. I. M ille r, W . A . C ., Jr., a nd others. Physical p ro p e r 5.1.2 Amount o f material in indi ties o f syn th e tic-rub be r-base dental im pre ssio n m a te vidual package. The amount of material rials. J .A .D .A . 60:211 Feb. I960.
Oral Examinations • For early cancer diagnosis, inclusion of an oral denial examination in the physical evaluation given patients on hospital admission is proving valuable, according to Veterans Administration. V A hospitals adopted the technic about two and a half years ago, and have since reported some 700 cases of malignancies of the mouth, tongue and throat which might otherwise have developed unnoticed until too late for successful treatment. Hospitals 33:21:66 Nov. 1, 1959.