S ta tu s
re p o rt o n
p o ly e th e r im p r e s s io n m a te r ia ls
I C o u ncil on D e n ta l M a te ria ls and D e v ic e s
Clinical applications Polyether impression materials were introduced in about 1970. They are a two-paste system con sisting of a base and a catalyst; a thinner paste may be added to alter some of the physical prop erties. The two polyether impression materials commercially available are Impregum* and Polygel.t The following characterization of polyether impression materials and recommendations for their use is based on research cited in the liter ature survey section. The working time of these materials is two minutes with a setting time of three to five min utes. The rate of set may be decreased by a factor of two using equal lengths of base, catalyst, and thinner. Polyethers exhibit non-Newtonian, thixotropic behavior; that is, at low rates of shear it is dif ficult to initiate flow, but high rates of shear will cause the material to flow more readily. This characteristic allows the material to be “ stacked’’ in the impression tray; but as the impressiontaking force is applied, adequate flow will devel op. The amount of flow should be enough for impressions of single or several teeth or possibly relationships between pontics and crowns. How ever, problems might develop if quadrant or fullarch impressions are desired. The coefficient of thermal expansion was found to be greater than that for polysulfide rub ber impression materials. To avoid inaccuracies, one must take care to avoid temperature varia tions. The set material is quite stiff as shown by the 126 ■ REPORTS OF COUNCILS AND BUREAUS / JADA, Vol. 95, July 1977
modulus of elasticity and percent strain in com pression, although the thinner can reduce the stiffness by half. The high stiffness, coupled with medium tear energy (similar to silicones but lower than polysulfide impression materials), makes the impression difficult to withdraw in tact. The stiffness also necessitates increased care when removing gypsum products from the impression. To alleviate these problems, the manufacturers recommend a greater bulk of ma terial between the tray and the surface of the im pression than used in polysulfide or silicone im pressions. The set polyether materials, like the silicones, exhibit properties that closely approximate elas tic behavior. This allows the impression to ex hibit excellent recovery from the deformation or stress caused by handling, shipping, or storage. The dimensional change on polymerization is about the same as that for polysulfide rubbers and only half that experienced by silicone ma terials. The water sorption is quite high (up to 15%), but this seems to be partially compensat ed for by extraction of the water-soluble com ponents. The net outcome is water absorption. This is especially pronounced in thin sections such as the interproximal areas of the impres sion. Consequently, the impressions should be stored under dry conditions; and electroplating, if desired, should be initiated as soon as possible. Studies have shown that dies made from poly ether impressions can be more accurate than those made from polysulfide or silicone if the above recommendations are followed. One case of hypersensitivity to a component of the polyether impression material has been reported in the literature.1 It appeared that the
alkyl benzene sulfonate in the catalyst paste was the cause of the irritation, and therefore, care in handling and mixing should be taken. The tray adhesive consists of a rubber dis solved in ketones and chloroform. Since the sol vents are volatile, they should be used with ade quate ventilation; breathing of the vapors should be avoided as well as prolonged or repeated con tact with the skin. In addition, the Council recommends: —Mix base and catalyst to a uniform color before use. —Avoid skin contact with the unmixed cata lyst, as this may cause sensitization. —In case of skin contact, wash with soap and water. —If an allergic skin reaction occurs, discon tinue use of the material.
Literature survey In 1969 a patent was issued to Schmitt and co workers2 for the making of elastomers from poly ethers terminated with imino groups, which are
//
:H - CH 3 I I N
/
CH 2
\
0
- CH - C - 0 2
CH 2
R I I -£ch
cross-linked with strong acids such as aromatic sulfonic acid esters. The cross-linked rubber was reported to have high dimensional accuracy after polymerization and on storage. A preliminary report in 1971 by Causton and Braden3 showed that the setting reaction of the polyether was more rapid than that for the poly sulfides, and that the system was clean and odor less. They stated that unset poly ether impres sion material had flow properties that might cause clinical difficulties; that the elastic modulus of the set rubber was about twice that of heavy bodied polysulfide rubber; and that the polymer was highly water absorbent. They also proposed that the dimensional change from water sorp tion might be offset by extraction of water-misable components. Braden, Causton, and Clarke4 later described the chemical composition and physical charac teristics of an elastomeric, imine-terminated, polyether impression material (Impregum). The material was supplied as two pastes, a base, and a catalyst. A third paste, labeled thinner, was supplied to alter the viscosity and properties. The structure of the initial low molecular weight polymer in the base paste was:
-fCH f O'} 2 n m-1
R I I CH
0
// //
4CH 2 n
C - 0 - CH - CH - CH 2 1 3, N
/
CH 2
\
R E PO R TS O F C O U N C ILS AN D B U REAU S / JA D A , V o l. 95, J u ly 1977 ■ 127
CH 2
The catalyst paste was believed to consist of an alkyl benzene sulfonate and a glycol ether plasticizer, the former probably being:
s o
3
c h
2
c h
ting time was measured to be five minutes; the linear thermal coefficient was 2.2xlO_4/°C; and the tear energies were similar to silicone and lower than polysulfide impression materials (Table).4 The water absorption at equilibrium was found to be about 15%, which is high when compared with polysulfides and silicones.4 However, when a set sample was immersed in water, the overall weight change was only 1% to 2%, because the water uptake was offset by water extraction of soluble material, presumably the glycol ether from the catalyst paste. No problems were re ported in the preparation of stone dies in several years of clinical use.4 The set polyether exhibited dimensional chang es of less than -0.1% on storage in air for sev eral hours.4 Immersion in water resulted in an initial expansion followed by contraction, the ef fect being more pronounced in thin sections of
3 .
The thinner was mainly a phthalate or a sim ple polyether with silica added as a thickening agent to make a paste. The base paste was de scribed as being cross-linked by cationic polym erization with ring opening of the imine, result ing in an increased molecular weight. The source of the cations was the alkyl group of the alkyl benzene sulfonate. The viscosity or thickness of the base paste was found to be high at low rates of shear, which made it difficult to initiate flow. The use of the thinner did not offset this characteristic. The set
Table
■ Summary of properties of impression materials. P o lye th e r
P o ly s u lfid e (type 1)
S ilic o n e base (type 2)
C lass 1 heavy
C lass 2 re g u la r
C lass 3 lig h t
C lass 1 heavy
C lass 2 re g u la r
C lass 3 lig h t
P ro p e rty
R eg u lar
1-1 T h in n e r
W o rk in g tim e , m in S e ttin g tim e , m in
2* 5 at ro o m te m p t 3.5 at 20°C § 3 at 37°C § 38 at 20°C § 34 a t 2 3 ° C t 32 a t 37°C §
4 .5 f 10 at ro o m te m p t
4 *.
4**
5 *’
4**
4**
5**
37 at 2 3 ° C t
27 ± 5 ”
32±6"
4 0 ± 8 **
27±5"
32 ± 6 **
40 ± 8 **
C o n siste n cy, mm
D im e n s io n a l ch a n g e o n s e ttin g , % in 24 h o u rs P e rm a n e n t d e fo rm a tio n AD A Test, % a t tim e o f re m ova l 1,000-g load a p p lie d fo r th e tim e liste d , % a t o n e h o u r a fte r re m ova l 1,000-g load a p p lie d fo r th e tim e g iven, % a fte r e x te n s io n c ycle ca u se d by 0 -.110 g - 0 , % P e rce n t stra in , AD A,% Flo w , ADA, % S h e ar m o d u lu s , N /m 2 Y o u n g 's m o d u lu s, N /m 2 T e n sile s tre n g th , N /m 2 C ree p c o m p lia n c e (in sta n ta n e o u s), cm 2/N a t tim e o f rem oval fro m th e m o u th o n e h o u r a fte r rem oval L in e a r c o e ffic ie n t o f e xp a n s io n , per °C W e ig h t ch a n g e in w a te r, % 1 Hr 6 Hr * t j § "
-0 .3 *
-0 .2 t
0.40**
0.40**
0.40**
0.60**
0.60**
0.60**
0 .9 f 1.1 at 1.7 at 2.3 at 3.9 at 0.4 at 0.4 at
0 .8 t 1 3t
4**
4**
4**
2*.
2*.
2 *.
2-20** 2"
2-20** 2** 3.8.1 OS*
2-20** 2**
2-20** 2**
2-20** 2** 69.10s*
2-20** 2*.
1 minU 3 m in i! 6 m in fl 12 m in fl 6 minU 12 m in fl
0 .3 t
0.5 at 10 m in § 0.2 at 48 hr§ 2* 0.03* 2 2 .7 X 1 0 5* 43-57X105 (10 m in, 48 hr)§
4t 0 .0 3 t 1 0 .6 x 1 0 5t
5X10-311
5 .7 X 1 0 - 3t
2 .5 X 1 0
2 .9 x 1 0 ~ 3t
16- 18x 105§
2 .2 X 1 0 -4*
Craig, R .G ., and others, reference 9. Tolley, L .G ., and C raig, R.G . V isco elastic measurem ent ofim pression materials.Unpublished data, Braden, M.; Causton, B .; and C larke, R .L ., reference 3. Kaloyannides, T.M ., references 4-6; Kaloyannides, T.M ., and Kapari,D .J., reference Goldberg. A .J., reference 8. ed. 7, reference 19.
Guide to Dental Materials and Devices,
128 ■ REPO R TS OF C O U NC ILS AND BU REAU S / JAD A, V o l. 95, J u ly 1977
7.
the rubber.4 The set polyether rubber had a high modulus of elasticity compared with that of other rubber impression materials, although the thinner re duced the modulus by about half.4 After the initial evaluations of polyether rub ber by Causton and Braden3 and Braden and others,4 a number of reports were published about the properties and use of polyether im pression materials.5'10 A summary of those val ues is listed in the Table. These reports showed the polyether material had a short working time of two minutes and confirmed a short setting time of 3 to 3.5 minutes. The high stiffness was confirmed by Young’s modulus values, and a high tensile strength was listed for a low but un reported rate of strain. The high stiffness also was shown by the percent strain value according to ADA Specification No. 19. The excellent re covery from deformation of the set rubber and low flow also supported previous reports.6-7 The creep compliance, recovery, and perma nent deformation were reported by Goldberg.9 He showed the material was linearly viscoelas tic; that instantaneous elastic, retarded elastic, and viscous flow all decreased with continued polymerization; and that the permanent defor mation resulted from lack of recovery of elastic deformation and viscous flow. He found the set polyether material to closely approach elastic behavior, which should minimize dimensional changes as a result of deformation of the impres sion on removal. Craig and co-workers10 found the dimensional change on setting was comparable with that for polysulfides and smaller than that for regular sil icone impression materials. The addition of thinner in equal lengths to the base and catalyst pastes did not result in signifi cant differences in critical properties as can be seen in the Table; although Braden and others4 claimed that major changes occurred in water sorption, solubility, and modulus when a thinner was used. Since dimensional accuracy is such an impor tant quality of impression materials, a number of studies have been made of this property.11'16 Brown11 measured the dimensional differences between stone dies made from impressions of both undercut and nonundercut metal dies at intervals between one hour and one week. He found the polyether and polysulfide catalyzed by lead dioxide produced the most accurate dies
when undercuts were present in the master die. He also showed that the polyether impressions should be kept dry during storage to maintain their accuracy. Sawyer and others12,13 took impressions of a stainless steel master die simulating a prepara tion for a three-unit bridge, poured stone models, and compared the vertical and horizontal chang es between the master and stone models. They found that the polyether impression material pro duced the most accurate models, followed by silicone and polysulfide impression materials. The polyether was the only impression material that resulted in models with good accuracy when a second pour was made or when the pouring of the model was delayed one to seven days. Henry and Hamist14 took impressions of a four-posted master stone model of the maxillary arch, poured stone models, and measured the horizontal discrepancies between them. They reported the polyether single-mix impressions were more accurate than the double-mix poly sulfide impressions and were comparable with the double impressions obtained with silicone putty-wash systems. Some difficulty was exper ienced in the removal of the poured stone models from the set poly ether impression material. Hembree15 reported little difference in accur acy in polyether impressions, regardless of whether a custom or stock tray was used. He al so found that the polyether impressions were not particularly susceptible to change on storage but should be poured within the first hour. Later, Hembree and Nunez16 measured the effect of moisture on the accuracy of polyether impres sions of a stainless steel model. The most accur ate stone models were obtained when an impres sion was taken of a dry surface and poured im mediately. The accuracy of the stone models was decreased when the pouring was delayed one hour and was decreased further when the impression was stored one hour in 100% relative humidity. The least accurate model was pre pared from an impression of a wet master model poured immediately in stone. Since the dimensional stability of polyether materials is affected by water, researchers have investigated the accuracy of silver-plated dies made from polyether impressions. In a recent study, Vermilyea and others1718 evaluated the quality of silver-plated dies and the accuracy of silver platings of polyether impressions using a simulated model of a bridge preparation. Plat R EPO R TS OF C O U N C ILS AND B U R E A U S /J A D A , V o l. 95, J u ly 1977 ■
129
ing was accomplished using silver metalizing powder and 10 ma per unit for 15 hours. Plating made on polyether materials was discolored, but the discoloration could be removed by wiping with tissue. N o tackiness of the surface of the rubber was observed, and the rubber separated readily from the silver plating. The silver plating reproduced a 0.026-mm groove in the impres sion, and no surface irregularities were observed. The most accurate silver-plated impressions were obtained from polyether impressions (+0.005%), followed by the putty-wash silicone (+0.021%), and then the tray-syringe polysulfide rubber (+0.056%).
5. Kaloyannides, T.M . Elasticity of elastom er im pression m a terials: I. M easurem ent of Y o u n g ’s m odulus of elasticity and the coefficient of elasticity. J D ent Res 52:439 M ay-June 1973. 6. Kaloyannides, T.M . Elasticity of elastom er im pression m a terials: II. Perm anent deform ation. J Dent Res 52:719 July-Aug 1973. 7. Kaloyannides, T.M . Elasticity of elastom er im pression m a terials: breaking lim it and ultim ate strength. J D ent Res 53:630 M ay-June 1974. 8. Kaloyannides, T.M ., and Kapari, D.J. Setting tim e and con sistency of elastom er im pression materials. J Dent Res 53:653 M ay-June 1974. 9. G o ldberg, A.J. V iscoelastic properties of silicone, polysul fid e and polyether im pression materials. J D ent Res 53(part 1): 1033 S ept-O ct 1974. 10. C raig, R.G.; O ’Brien, W.J.; and Powers, J.M . Dental m ater ials: properties and m anipulation. St. Louis, C. V. M osby Co., 1975, p 142. 11. B row n, D. Factors affecting the dim ensional stability of elastic im pression m aterials. J Dent (Bristol) 1 :265 Aug 1973. 12. Sawyer, H.F., and others. A ccuracy of casts produced from seven rubber im pression m aterials. JADA 87:126 July 1973.
This report was prepared at th e request of th e Council on D en
13. Sawyer, H.F., and others. Accuracy of casts produced
tal M aterials and Devices by R obert G. Craig, PhD, professor and chairm an of th e departm ent of dental m aterials at the Uni versity of M ichigan School of Dentistry, Ann Arbor, 48109.
from th re e classes of elastom er im pression materials. JADA 89: 644 Sept 1974.
*lm preg um , Espe Fabrik Pharm azeutishe Präparate G M B H , Seefeld, O ber-B ayern, Germany. tP olyg el, L. D. C au lk Co., M ilford, Del 19963. 1. Nally, F.F., and Storrs, J. Hypersensitivity to a dental im pression m aterial. Br D ent J 134:224 March 1973. 2. S chm itt, W., and others. (Espe Fabrik Pharm azeutischer P räparate G M B H .) Elastom ers from polyethers and ethylene im in e derivatives. US Patent 3,453,242 (July 1, 1969). 3. Causton, B., and Braden, M. Polyether im pression rubber. A bstracted, IADR Program and Abstracts No. 42 May-June 1971. 4. B raden, M.; Causton, B.; and Clarke, R.L. A polyether im pression m aterial. J Dent Res 5 1 :889 July-Aug 1972.
130 ■ R EPO R TS OF C O U N C ILS AN D BU R EAU S / JAD A, V o l. 95, J u ly 1977
14. Henry, P.J., and Harnist, D.J.R. Dim ensional stability and accuracy of rubber im pression materials. Aust Dent J 19:162 June 1974. 15. H em bree, J.H., Jr. A ccuracy of elastom er im pression ma terials. J D en t Res 53 (special issue):69 abstract no. 57 Feb 1974. 16. H em bree, J.H., Jr., and Nunez, L.J. Effect of m oisture on polyether im pression m aterials. JADA 89:1134 Nov 1974. 17. Verm ilyea, S.G.; Powers, J.M .; and Craig, R.G. Polyether, polysulfide and silicone rubber im pression m aterials. Part I. Quality of silverplated dies. M ich Dent A J in press. 18. Verm ilyea, S.G.; Powers, J.M .; and Craig, R.G. Polyether, polysulfide and silicone rubber im pression m aterials. Part II. A c curacy of silverplated dies. M ich Dent A J in press. 19. Guide to Dental M aterials and Devices, ed 7. Chicago, A m erican Dental Association, Council on Dental M aterials and Devices, 1974, p 223.
re p o rt o n
p o ly e th e r im p r e s s io n m a te r ia ls
I C o u ncil on D e n ta l M a te ria ls and D e v ic e s
Clinical applications Polyether impression materials were introduced in about 1970. They are a two-paste system con sisting of a base and a catalyst; a thinner paste may be added to alter some of the physical prop erties. The two polyether impression materials commercially available are Impregum* and Polygel.t The following characterization of polyether impression materials and recommendations for their use is based on research cited in the liter ature survey section. The working time of these materials is two minutes with a setting time of three to five min utes. The rate of set may be decreased by a factor of two using equal lengths of base, catalyst, and thinner. Polyethers exhibit non-Newtonian, thixotropic behavior; that is, at low rates of shear it is dif ficult to initiate flow, but high rates of shear will cause the material to flow more readily. This characteristic allows the material to be “ stacked’’ in the impression tray; but as the impressiontaking force is applied, adequate flow will devel op. The amount of flow should be enough for impressions of single or several teeth or possibly relationships between pontics and crowns. How ever, problems might develop if quadrant or fullarch impressions are desired. The coefficient of thermal expansion was found to be greater than that for polysulfide rub ber impression materials. To avoid inaccuracies, one must take care to avoid temperature varia tions. The set material is quite stiff as shown by the 126 ■ REPORTS OF COUNCILS AND BUREAUS / JADA, Vol. 95, July 1977
modulus of elasticity and percent strain in com pression, although the thinner can reduce the stiffness by half. The high stiffness, coupled with medium tear energy (similar to silicones but lower than polysulfide impression materials), makes the impression difficult to withdraw in tact. The stiffness also necessitates increased care when removing gypsum products from the impression. To alleviate these problems, the manufacturers recommend a greater bulk of ma terial between the tray and the surface of the im pression than used in polysulfide or silicone im pressions. The set polyether materials, like the silicones, exhibit properties that closely approximate elas tic behavior. This allows the impression to ex hibit excellent recovery from the deformation or stress caused by handling, shipping, or storage. The dimensional change on polymerization is about the same as that for polysulfide rubbers and only half that experienced by silicone ma terials. The water sorption is quite high (up to 15%), but this seems to be partially compensat ed for by extraction of the water-soluble com ponents. The net outcome is water absorption. This is especially pronounced in thin sections such as the interproximal areas of the impres sion. Consequently, the impressions should be stored under dry conditions; and electroplating, if desired, should be initiated as soon as possible. Studies have shown that dies made from poly ether impressions can be more accurate than those made from polysulfide or silicone if the above recommendations are followed. One case of hypersensitivity to a component of the polyether impression material has been reported in the literature.1 It appeared that the
alkyl benzene sulfonate in the catalyst paste was the cause of the irritation, and therefore, care in handling and mixing should be taken. The tray adhesive consists of a rubber dis solved in ketones and chloroform. Since the sol vents are volatile, they should be used with ade quate ventilation; breathing of the vapors should be avoided as well as prolonged or repeated con tact with the skin. In addition, the Council recommends: —Mix base and catalyst to a uniform color before use. —Avoid skin contact with the unmixed cata lyst, as this may cause sensitization. —In case of skin contact, wash with soap and water. —If an allergic skin reaction occurs, discon tinue use of the material.
Literature survey In 1969 a patent was issued to Schmitt and co workers2 for the making of elastomers from poly ethers terminated with imino groups, which are
//
:H - CH 3 I I N
/
CH 2
\
0
- CH - C - 0 2
CH 2
R I I -£ch
cross-linked with strong acids such as aromatic sulfonic acid esters. The cross-linked rubber was reported to have high dimensional accuracy after polymerization and on storage. A preliminary report in 1971 by Causton and Braden3 showed that the setting reaction of the polyether was more rapid than that for the poly sulfides, and that the system was clean and odor less. They stated that unset poly ether impres sion material had flow properties that might cause clinical difficulties; that the elastic modulus of the set rubber was about twice that of heavy bodied polysulfide rubber; and that the polymer was highly water absorbent. They also proposed that the dimensional change from water sorp tion might be offset by extraction of water-misable components. Braden, Causton, and Clarke4 later described the chemical composition and physical charac teristics of an elastomeric, imine-terminated, polyether impression material (Impregum). The material was supplied as two pastes, a base, and a catalyst. A third paste, labeled thinner, was supplied to alter the viscosity and properties. The structure of the initial low molecular weight polymer in the base paste was:
-fCH f O'} 2 n m-1
R I I CH
0
// //
4CH 2 n
C - 0 - CH - CH - CH 2 1 3, N
/
CH 2
\
R E PO R TS O F C O U N C ILS AN D B U REAU S / JA D A , V o l. 95, J u ly 1977 ■ 127
CH 2
The catalyst paste was believed to consist of an alkyl benzene sulfonate and a glycol ether plasticizer, the former probably being:
s o
3
c h
2
c h
ting time was measured to be five minutes; the linear thermal coefficient was 2.2xlO_4/°C; and the tear energies were similar to silicone and lower than polysulfide impression materials (Table).4 The water absorption at equilibrium was found to be about 15%, which is high when compared with polysulfides and silicones.4 However, when a set sample was immersed in water, the overall weight change was only 1% to 2%, because the water uptake was offset by water extraction of soluble material, presumably the glycol ether from the catalyst paste. No problems were re ported in the preparation of stone dies in several years of clinical use.4 The set polyether exhibited dimensional chang es of less than -0.1% on storage in air for sev eral hours.4 Immersion in water resulted in an initial expansion followed by contraction, the ef fect being more pronounced in thin sections of
3 .
The thinner was mainly a phthalate or a sim ple polyether with silica added as a thickening agent to make a paste. The base paste was de scribed as being cross-linked by cationic polym erization with ring opening of the imine, result ing in an increased molecular weight. The source of the cations was the alkyl group of the alkyl benzene sulfonate. The viscosity or thickness of the base paste was found to be high at low rates of shear, which made it difficult to initiate flow. The use of the thinner did not offset this characteristic. The set
Table
■ Summary of properties of impression materials. P o lye th e r
P o ly s u lfid e (type 1)
S ilic o n e base (type 2)
C lass 1 heavy
C lass 2 re g u la r
C lass 3 lig h t
C lass 1 heavy
C lass 2 re g u la r
C lass 3 lig h t
P ro p e rty
R eg u lar
1-1 T h in n e r
W o rk in g tim e , m in S e ttin g tim e , m in
2* 5 at ro o m te m p t 3.5 at 20°C § 3 at 37°C § 38 at 20°C § 34 a t 2 3 ° C t 32 a t 37°C §
4 .5 f 10 at ro o m te m p t
4 *.
4**
5 *’
4**
4**
5**
37 at 2 3 ° C t
27 ± 5 ”
32±6"
4 0 ± 8 **
27±5"
32 ± 6 **
40 ± 8 **
C o n siste n cy, mm
D im e n s io n a l ch a n g e o n s e ttin g , % in 24 h o u rs P e rm a n e n t d e fo rm a tio n AD A Test, % a t tim e o f re m ova l 1,000-g load a p p lie d fo r th e tim e liste d , % a t o n e h o u r a fte r re m ova l 1,000-g load a p p lie d fo r th e tim e g iven, % a fte r e x te n s io n c ycle ca u se d by 0 -.110 g - 0 , % P e rce n t stra in , AD A,% Flo w , ADA, % S h e ar m o d u lu s , N /m 2 Y o u n g 's m o d u lu s, N /m 2 T e n sile s tre n g th , N /m 2 C ree p c o m p lia n c e (in sta n ta n e o u s), cm 2/N a t tim e o f rem oval fro m th e m o u th o n e h o u r a fte r rem oval L in e a r c o e ffic ie n t o f e xp a n s io n , per °C W e ig h t ch a n g e in w a te r, % 1 Hr 6 Hr * t j § "
-0 .3 *
-0 .2 t
0.40**
0.40**
0.40**
0.60**
0.60**
0.60**
0 .9 f 1.1 at 1.7 at 2.3 at 3.9 at 0.4 at 0.4 at
0 .8 t 1 3t
4**
4**
4**
2*.
2*.
2 *.
2-20** 2"
2-20** 2** 3.8.1 OS*
2-20** 2**
2-20** 2**
2-20** 2** 69.10s*
2-20** 2*.
1 minU 3 m in i! 6 m in fl 12 m in fl 6 minU 12 m in fl
0 .3 t
0.5 at 10 m in § 0.2 at 48 hr§ 2* 0.03* 2 2 .7 X 1 0 5* 43-57X105 (10 m in, 48 hr)§
4t 0 .0 3 t 1 0 .6 x 1 0 5t
5X10-311
5 .7 X 1 0 - 3t
2 .5 X 1 0
2 .9 x 1 0 ~ 3t
16- 18x 105§
2 .2 X 1 0 -4*
Craig, R .G ., and others, reference 9. Tolley, L .G ., and C raig, R.G . V isco elastic measurem ent ofim pression materials.Unpublished data, Braden, M.; Causton, B .; and C larke, R .L ., reference 3. Kaloyannides, T.M ., references 4-6; Kaloyannides, T.M ., and Kapari,D .J., reference Goldberg. A .J., reference 8. ed. 7, reference 19.
Guide to Dental Materials and Devices,
128 ■ REPO R TS OF C O U NC ILS AND BU REAU S / JAD A, V o l. 95, J u ly 1977
7.
the rubber.4 The set polyether rubber had a high modulus of elasticity compared with that of other rubber impression materials, although the thinner re duced the modulus by about half.4 After the initial evaluations of polyether rub ber by Causton and Braden3 and Braden and others,4 a number of reports were published about the properties and use of polyether im pression materials.5'10 A summary of those val ues is listed in the Table. These reports showed the polyether material had a short working time of two minutes and confirmed a short setting time of 3 to 3.5 minutes. The high stiffness was confirmed by Young’s modulus values, and a high tensile strength was listed for a low but un reported rate of strain. The high stiffness also was shown by the percent strain value according to ADA Specification No. 19. The excellent re covery from deformation of the set rubber and low flow also supported previous reports.6-7 The creep compliance, recovery, and perma nent deformation were reported by Goldberg.9 He showed the material was linearly viscoelas tic; that instantaneous elastic, retarded elastic, and viscous flow all decreased with continued polymerization; and that the permanent defor mation resulted from lack of recovery of elastic deformation and viscous flow. He found the set polyether material to closely approach elastic behavior, which should minimize dimensional changes as a result of deformation of the impres sion on removal. Craig and co-workers10 found the dimensional change on setting was comparable with that for polysulfides and smaller than that for regular sil icone impression materials. The addition of thinner in equal lengths to the base and catalyst pastes did not result in signifi cant differences in critical properties as can be seen in the Table; although Braden and others4 claimed that major changes occurred in water sorption, solubility, and modulus when a thinner was used. Since dimensional accuracy is such an impor tant quality of impression materials, a number of studies have been made of this property.11'16 Brown11 measured the dimensional differences between stone dies made from impressions of both undercut and nonundercut metal dies at intervals between one hour and one week. He found the polyether and polysulfide catalyzed by lead dioxide produced the most accurate dies
when undercuts were present in the master die. He also showed that the polyether impressions should be kept dry during storage to maintain their accuracy. Sawyer and others12,13 took impressions of a stainless steel master die simulating a prepara tion for a three-unit bridge, poured stone models, and compared the vertical and horizontal chang es between the master and stone models. They found that the polyether impression material pro duced the most accurate models, followed by silicone and polysulfide impression materials. The polyether was the only impression material that resulted in models with good accuracy when a second pour was made or when the pouring of the model was delayed one to seven days. Henry and Hamist14 took impressions of a four-posted master stone model of the maxillary arch, poured stone models, and measured the horizontal discrepancies between them. They reported the polyether single-mix impressions were more accurate than the double-mix poly sulfide impressions and were comparable with the double impressions obtained with silicone putty-wash systems. Some difficulty was exper ienced in the removal of the poured stone models from the set poly ether impression material. Hembree15 reported little difference in accur acy in polyether impressions, regardless of whether a custom or stock tray was used. He al so found that the polyether impressions were not particularly susceptible to change on storage but should be poured within the first hour. Later, Hembree and Nunez16 measured the effect of moisture on the accuracy of polyether impres sions of a stainless steel model. The most accur ate stone models were obtained when an impres sion was taken of a dry surface and poured im mediately. The accuracy of the stone models was decreased when the pouring was delayed one hour and was decreased further when the impression was stored one hour in 100% relative humidity. The least accurate model was pre pared from an impression of a wet master model poured immediately in stone. Since the dimensional stability of polyether materials is affected by water, researchers have investigated the accuracy of silver-plated dies made from polyether impressions. In a recent study, Vermilyea and others1718 evaluated the quality of silver-plated dies and the accuracy of silver platings of polyether impressions using a simulated model of a bridge preparation. Plat R EPO R TS OF C O U N C ILS AND B U R E A U S /J A D A , V o l. 95, J u ly 1977 ■
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ing was accomplished using silver metalizing powder and 10 ma per unit for 15 hours. Plating made on polyether materials was discolored, but the discoloration could be removed by wiping with tissue. N o tackiness of the surface of the rubber was observed, and the rubber separated readily from the silver plating. The silver plating reproduced a 0.026-mm groove in the impres sion, and no surface irregularities were observed. The most accurate silver-plated impressions were obtained from polyether impressions (+0.005%), followed by the putty-wash silicone (+0.021%), and then the tray-syringe polysulfide rubber (+0.056%).
5. Kaloyannides, T.M . Elasticity of elastom er im pression m a terials: I. M easurem ent of Y o u n g ’s m odulus of elasticity and the coefficient of elasticity. J D ent Res 52:439 M ay-June 1973. 6. Kaloyannides, T.M . Elasticity of elastom er im pression m a terials: II. Perm anent deform ation. J Dent Res 52:719 July-Aug 1973. 7. Kaloyannides, T.M . Elasticity of elastom er im pression m a terials: breaking lim it and ultim ate strength. J D ent Res 53:630 M ay-June 1974. 8. Kaloyannides, T.M ., and Kapari, D.J. Setting tim e and con sistency of elastom er im pression materials. J Dent Res 53:653 M ay-June 1974. 9. G o ldberg, A.J. V iscoelastic properties of silicone, polysul fid e and polyether im pression materials. J D ent Res 53(part 1): 1033 S ept-O ct 1974. 10. C raig, R.G.; O ’Brien, W.J.; and Powers, J.M . Dental m ater ials: properties and m anipulation. St. Louis, C. V. M osby Co., 1975, p 142. 11. B row n, D. Factors affecting the dim ensional stability of elastic im pression m aterials. J Dent (Bristol) 1 :265 Aug 1973. 12. Sawyer, H.F., and others. A ccuracy of casts produced from seven rubber im pression m aterials. JADA 87:126 July 1973.
This report was prepared at th e request of th e Council on D en
13. Sawyer, H.F., and others. Accuracy of casts produced
tal M aterials and Devices by R obert G. Craig, PhD, professor and chairm an of th e departm ent of dental m aterials at the Uni versity of M ichigan School of Dentistry, Ann Arbor, 48109.
from th re e classes of elastom er im pression materials. JADA 89: 644 Sept 1974.
*lm preg um , Espe Fabrik Pharm azeutishe Präparate G M B H , Seefeld, O ber-B ayern, Germany. tP olyg el, L. D. C au lk Co., M ilford, Del 19963. 1. Nally, F.F., and Storrs, J. Hypersensitivity to a dental im pression m aterial. Br D ent J 134:224 March 1973. 2. S chm itt, W., and others. (Espe Fabrik Pharm azeutischer P räparate G M B H .) Elastom ers from polyethers and ethylene im in e derivatives. US Patent 3,453,242 (July 1, 1969). 3. Causton, B., and Braden, M. Polyether im pression rubber. A bstracted, IADR Program and Abstracts No. 42 May-June 1971. 4. B raden, M.; Causton, B.; and Clarke, R.L. A polyether im pression m aterial. J Dent Res 5 1 :889 July-Aug 1972.
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14. Henry, P.J., and Harnist, D.J.R. Dim ensional stability and accuracy of rubber im pression materials. Aust Dent J 19:162 June 1974. 15. H em bree, J.H., Jr. A ccuracy of elastom er im pression ma terials. J D en t Res 53 (special issue):69 abstract no. 57 Feb 1974. 16. H em bree, J.H., Jr., and Nunez, L.J. Effect of m oisture on polyether im pression m aterials. JADA 89:1134 Nov 1974. 17. Verm ilyea, S.G.; Powers, J.M .; and Craig, R.G. Polyether, polysulfide and silicone rubber im pression m aterials. Part I. Quality of silverplated dies. M ich Dent A J in press. 18. Verm ilyea, S.G.; Powers, J.M .; and Craig, R.G. Polyether, polysulfide and silicone rubber im pression m aterials. Part II. A c curacy of silverplated dies. M ich Dent A J in press. 19. Guide to Dental M aterials and Devices, ed 7. Chicago, A m erican Dental Association, Council on Dental M aterials and Devices, 1974, p 223.
