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A method for testing denture adhesives
SECTION EDITOR
A m e t h o d for t e s t i n g d e n t u r e a d h e s i v e s F. F l ~ $ y s t r a n d , D r O d o n t , a R. K o p p a n g , D r P h i l o s , a V. D . W i l l i a m s , M S , b a n d J. 0 r s t a v i k , D r O d o n t c
University of 0slo, Dental Faculty, 0slo, Norway, and University of Iowa, College of Dentistry, Iowa City, Iowa An in vitro test m e t h o d is d e s c r i b e d s i m u l a t i n g the in v i v o fate o f a denture a d h e s i v e , i.e., destruction of the a d h e s i v e , dilution, and dissolution, by m e a s u r i n g the bond s t r e n g t h for the a d h e s i v e placed b e t w e e n acrylic r e s i n plates. B e t w e e n each m e a s u r e m e n t , the a d h e s i v e w a s e x p o s e d to isotonic saline. The bond s t r e n g t h for t w o o i n t m e n t denture a d h e s i v e s , S u p e r Corega and Fixodent, w a s m e a s u r e d and the results w e r e c o m p a r e d w i t h those o b t a i n e d for one o f t h e m in a p r e v i o u s in vivo test. The test m e t h o d d e s c r i b e d for denture a d h e s i v e s s e e m s u s e f u l to depict the fate of a denture a d h e s i v e in clinical use. (J PROSTHET DENT 1991;66:501-4.)
A l t h o u g h
use of denture adhesives is worldwide, little attention has been focused on these materials in the dental literature. The studies performed in vivo were on denture movement under function, 14 on denture retention, 4s and on the loss of denture adhesive over time. 7 In vitro studies concentrated on rheology properties of the products. .s An unpublished retention study 9 on individually adjusted acrylic resin palatal test plates was performed over 10 hours oH 25 students in the Department of Prosthetics, Dental Faculty, University of Oslo, and unpublished results are shown in Fig. 1. An investigation was done to determine if the results from the student study were reproducible in an accelerated in vitro test through destruction, dilution, and dissolution of the adhesive as in oral use. MATERIAL
12 Super Corego ®
6
>o
n~ 0
A
aAssociate Professor, Department of Preclinical Techniques and Material Sciences, University of Oslo, Dental Faculty. bAssociate Professor, Department of Family Dentistry, University of Iowa, College of Dentistry. CProfessor, Department of Prosthetic Dentistry, University of Iowa, College of Dentistry. 10/1/26750
THE JOURNAL OF PROSTHETIC DENTISTRY
o
3
6
12
9
Time (~)
120 Super Corego® 90
AND METHODS
Two brands of denture adhesives (Super Corega, Stafford-Miller Ltd., Hatfield Herts, England; and Fixodent, Richardson-Vicks, Inc., Wilton, Conn.) were tested. Judging from the literature and from the pertinent patents, the main components in Super Corega adhesive are carboxymethylcellulose, a-hydroxy-v-hydroxy-poly(oxyethylenes), sodium monophosphate, and dicalciumphosphate. 1° Fixodent adhesive most probably contains sodium carboxymethylcellulose, a-hydroxy-7-hydroxy-poly(oxy-ethylenes), and glycerol. 11B o t h products are mint-flavored.
1
c e~
60
"~
1
30
0
B
0
3
6
9
12
Fig. 1. A, Retention measured as a function of time on individually adjusted acrylic resin palatal test plates with Super Corega adhesive in 25 students# Force required to dislodge plates was directly opposite to the path of insertion and was measured with an electronic bite force recorder. 12 Measurements were performed 5 minutes and 3, 6, and 10 hours after insertion of plates. Each point gives the mean value for 23 measurements, one for each student. Without adhesive, spontaneous loosening of palatal plate resulted. B, Same as for A, but individual results of each measurement have been set to 100% after 3 hours. Mean results in are given in percent after 5 minutes and after 3, 6, and 10 hours.
501
FLOYSTRAND ET AL
F i g . 2. A p p a r a t u s for measuring bond strength of denture adhesives. A, Balance scale; B, bite force recorder; C, sensory unit; D, t h e r m o s t a t e d isotonic saline b a t h with adhesive pressed between acrylic resin plate and acrylic resin b o t t o m of bath; E, two kilogram brass weight to press acrylic resin plate into place; F, bucket (110 gm); G, water reservoir.
T a b l e I. Bond strength for Fixodent and Super Corega denture adhesives T i m e (rain)
Number
M e a n (N)
Range (N)
Std D e v
SEM
CV (%)
10 10 10 10 10 10
10.2 21.1 11.9 4.9* 2.3t 0c
8.0-13.0 17.0-27.5 9.0-14.0 3.0-8.0 1.0-3.0
1.8 3.6 1.7 1.4 0.6
0.6 1.1 0.5 0.5 0.2
17.5 17.0 14.4 29.2 26.2
10 10 10 10 10 10
9.3 18.6 11.7 9.3* 6.1t 2.4
6.5-11.0 15.0-21.5 9.0-14.0 6.5-12.0 2.0-10.5 0c-5.0
1.3 2.2 1.5 1.8 2.9 1.6
0.4 0.7 0.5 0.6 0.9 0.5
13.7 11.7 13.1 19.9 48.6 65.7
Fixodent 0 a 0b
2 2 3 5 4 9 5 14 6 20
Super Corega 0 0 2 2 3 5 4 9 5 14 6 20
Adhesives measured were pressed between two acrylic resin surfaces with a diameter of 3 cm. CV, Coefficient of variation. *, tMeans are significantly different at the 0.05 level of confidence (Duncan's multiple range test). aBond strength of adhesive was measured at time 0 and at intervals of 2, 3, 4 and 6 minutes in contact with isotonic saline (applies to all values in this column). bTotal time of adhesive exposure to isotonic saline before bond strength measurement (applies to all values in this column). CResults below 1 N are not measurable and have been set at zero.
Test
apparatus
A balance scale giving a tensile stress for the adhesive was used to test the bond strength of the denture adhesives (Fig. 2). The tensile stress was raised with 2 N / m i n by use of a hydrostatic head of water adjusted to deliver a smooth stream of water to a bucket. The tensile stress was recorded
502
with a bite force recorder previously described 12 and a strip-chart recorder. The bite force recorder was adjusted to deliver 2.5 V at 10 mA to the silicone beam semiconductor in the bite fork. The speed of the strip-chart recorder was set at 0.5 cm/min.
OCTOBER 1991 VOLUME 66 NUMBER 4
TESTING
OF DENTURE
ADHESIVES
Experimental procedure The denture adhesives were tested by applying 0.3 gm of paste to a highly polished acrylic resin plate 3 cm in diameter. The acrylic resin plate was pressed into place against the polished acrylic resin bottom surface of a dry acrylic resin vessel (diameter = 11 cm) with a 2 kg brass weight for a period of 15 seconds, whereupon the first measurement was made. One hundred milliliters of isotonic saline at 37 _+ 1° C was then added to the vessel. After the acrylic surfaces with adhesive had been exposed to isotonic saline for 2 minutes, the acrylic resin plate was reseated with the 2 kg brass weight, and a new measurement was made. Subsequently the adhesive was exposed to the isotonic saline for 3 minutes. The acrylic resin plate was reseated as described previously and the adhesive bond strength was measured. This described procedure was followed with the adhesive in contact with 100 ml isotonic saline for 1 additional minute until no bond strength could be recorded (Table I). The bath of isotonic saline was kept at a constant temperature of 37 -+ 1 ° C. Ten consecutive test series were carried out for both adhesives. Between each test series, the acrylic resin plates were cleaned with tap water, by hand dried with a paper towel, wiped off with 95% ethanol, and dried once more with a paper towel. The acrylic resin plates were examined under a stereomicroscope before and after testing. No changes were observed in the surface of the plates during testing.
Statistical analysis Statistical variance analysis of the measured bond strength values was based on Duncan's multiple range test. RESULTS Bond strengths (mean, range, standard deviation, standard error of the mean, and coefficient of variation) are given in Table I. Super Corega adhesive showed significantly higher mean bond strengths than Fixodent adhesive (p < 0.05) after 9 and 14 minutes of being in contact with isotonic saline, as shown in Table I and Fig. 3. Both products gave an initial high bond strength at the 2-minute level. At the 5-minute juncture, i.e., 2 plu s 3 minutes in contact with isotonic saline, the mean bond strength of Super Corega adhesive tended to level off and declined much more slowly than that of Fixodent adhesive, giving some measure of bond strength until a total of 20 minutes of being in contact with the isotonic saline had elapsed from the onset of testing. The mean bond strength of Fixodent adhesive at the juncture of 5 minutes continued to decrease quite rapidly, and at 20 minutes from the onset of testing no measurable bond strength remained. DISCUSSION A previous study (Fig. 1) and the present investigation (Fig. 3) showed that the retention values for a denture with an ointment adhesive both in in vivo tests and in simulated
THE JOURNAL
OF PROSTHETIC
DENTISTRY
24
20
/ j~x\
16
' 7 ~ / ~ ',
Super Corega® - Fixodent~
\.T
O ~
m
~D l 0
~"
2
5
8
11
'
'
'
. . . . . .
14 17 ]]me (rain)
20
Fig. 3. Measured bond strength for Super Corega and Fixodent adhesives as a function of the total time in which adhesives were in contact with isotonic saline. Values for 20 minutes were not measurable for Fixodent adhesive. Adhesives were pressed between two acrylic resin surfaces with a diameter of 3 cm.
laboratory tests reached a maximum and then declined as a function of time. The interpretation of a similar relationship for the viscosity of an adhesive in contact with water s should explain the presently observed bond strengths. From time zero (to), the adhesive slowly absorbs water and swells with increasing viscosity until the hydrophilic high polymer particles in the adhesive attain contact with each other to form a continuous polymer matrix. This explanation agrees well with results obtained in a Texturometer evaluation test. u The subsequent decline in viscosity values s may result from a dilution effect together with destruction of the gel matrix. The fall in measured bond strengths with time as presently observed may therefore result from both dilution and destruction of the adhesive gel formed by the adhesive, together with a dissolution of the adhesive in the isotonic saline (saliva). Based on patent literature, denture adhesives appear homogeneous with respect to chemical composition. This is also indicated by the present in vitro retention tests, where the maximum bonding strength for two different adhesives coincided after 2 minutes of contact with isotonic saline. It is therefore assumed that the maximum bonding strength for both materials tested corresponds with the achieved maximum at 3 hours found for one of them in an in vivo test, 9 indicating that 2 minutes in the in vitro test is the equivalent of 3 hours in the in vivo test. Further, for Super Corega adhesive, 5 hours (Fig. 1) elapsed before the bond strength declined to the starting value in the in vivo measurement, while a total of 9 minutes in the in vitro situation brought the same result. These time values presumably are parallel for Super Corega adhesive. If this approximation is correct, Fixodent adhesive should in practical use give a better retention than the starting result (i.e., 5-minute result) for approximately the first 4.2 hours, and Super Corega adhesive likewise for the first 5 hours, with Fixodent adhesive giving some improved retention corn-
503
FL~YSTRAND ET AL
pared with Super Corega adhesive for approximately the first 3.8 hours. CONCLUSIONS The results of retention measurements obtained in an accelerated laboratory test imitating the retention of a denture with a denture ointment adhesive in vivo concur with results from in vivo experiments. 9 They parallel those of viscosity measurements on ointment denture adhesives 8 when dissolution effects are neglected. The test method described for denture adhesives seems useful to depict the fate of denture adhesives. Results obtained with this method may be taken into consideration in the choice of an adhesive with respect to its effectiveness over various periods of time. SUMMARY A method feasible for testing the retention effect, i.e., the bond strength, of denture adhesives has been presented. Two brands of adhesives were shown to have different retention properties using this method. REFERENCES 1. Chew CL, Boone ME, Swartz ML, Phillips RW. Denture adhesives: their effect on denture retention and stability. J Dent 1985;13:152-9. 2. Karlsson S, Swartz B. Denture adhesives--their effect on the mobility of full upper dentures during chewing. Swed Dent J 1981;5:207-11.
3. Tarbet WJ, Boone M, Schmidt NF. Effect of denture adhesive on complete denture dislodgement during mastication. J PROSTHET DENT 1980;44:374-8. 4. Mirza FD, Dikshit JV, Murdia NS. Effectiveness of denture adhesives at different time intervals. J Indian Dent Assoc 1983;55:9-13. 5. Mirza FD, Dikshit JV, Murdia NS. Comparative study of effectiveness of denture adhesives at different time intervals. J Indian Dent Assoc 1984;56:335-7. 6. Ow RKK, Beam EM. A method of studying the effect of adhesive on denture retention. J PROSTHET DENT 1983;50:332-7. 7. Swartz ML, Norman RD, Phillips RW. A method for measuring retention of denture adherents: an in vivo study. J PROSTHET DENT 1967;17:456-63. 8. Ellis B, A1-Nakash S. The composition and rheology of denture adhesives. J Dent 1980;8:109-18. 9. FlCystrand F, 0rstavik J. An experimental model for testing denture adhesives in vivo [Abstract]. J Dent Res 1985;64:768 and unpublished results. 10. Blomdahl M, Erichson A. Proteseadhesiver. Tandlakartidningen 1980;72:680-2. 11. Dhabhar DJ, Schmidt NF. Denture adhesive composition. European Patent Application EP 1982; 64,672 and Karaya gum adhesive in a hydrophilic denture vehicle. European Patent Application EP 1984;113,079. 12. FlCystrand F, Kleven E, Oilo G. A novel miniature bite force recorder and its clinical application. Acta Odontol Scand i982;40:209-14. Reprint requests to: DR. ROLF KOPPANG UNIVERSITYOF OSLO BOX 1052 BLINDERN 0316 OSLO 3, NORWAY
B o u n d v o l u m e s a v a i l a b l e to s u b s c r i b e r s Bound volumes of T H E JOURNAL OF PROSTHETIC DENTISTRYare available to subscribers (only) for the 1991 issues from the publisher at a cost of $50.00 ($63.00 international) for Vol. 65 (January-June) and Vol. 66 (July-December). Shipping charges are included. Each bound volume contains a subject and author index, and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Volumes 63 and 64 are also available. Payment must accompany all orders. Contact Mosby-Year Book, Inc., Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, USA; phone (800) 325-4177, ext. 4351. S u b s c r i p t i o n s m u s t be in f o r c e to q u a l i f y . B o u n d v o l u m e s a r e n o t a v a i l a b l e in p l a c e o f a r e g u l a r JOURNAL s u b s c r i p t i o n .
504
OCTOBER 1991
VOLUME 66
NUMBER 4
A m e t h o d for t e s t i n g d e n t u r e a d h e s i v e s F. F l ~ $ y s t r a n d , D r O d o n t , a R. K o p p a n g , D r P h i l o s , a V. D . W i l l i a m s , M S , b a n d J. 0 r s t a v i k , D r O d o n t c
University of 0slo, Dental Faculty, 0slo, Norway, and University of Iowa, College of Dentistry, Iowa City, Iowa An in vitro test m e t h o d is d e s c r i b e d s i m u l a t i n g the in v i v o fate o f a denture a d h e s i v e , i.e., destruction of the a d h e s i v e , dilution, and dissolution, by m e a s u r i n g the bond s t r e n g t h for the a d h e s i v e placed b e t w e e n acrylic r e s i n plates. B e t w e e n each m e a s u r e m e n t , the a d h e s i v e w a s e x p o s e d to isotonic saline. The bond s t r e n g t h for t w o o i n t m e n t denture a d h e s i v e s , S u p e r Corega and Fixodent, w a s m e a s u r e d and the results w e r e c o m p a r e d w i t h those o b t a i n e d for one o f t h e m in a p r e v i o u s in vivo test. The test m e t h o d d e s c r i b e d for denture a d h e s i v e s s e e m s u s e f u l to depict the fate of a denture a d h e s i v e in clinical use. (J PROSTHET DENT 1991;66:501-4.)
A l t h o u g h
use of denture adhesives is worldwide, little attention has been focused on these materials in the dental literature. The studies performed in vivo were on denture movement under function, 14 on denture retention, 4s and on the loss of denture adhesive over time. 7 In vitro studies concentrated on rheology properties of the products. .s An unpublished retention study 9 on individually adjusted acrylic resin palatal test plates was performed over 10 hours oH 25 students in the Department of Prosthetics, Dental Faculty, University of Oslo, and unpublished results are shown in Fig. 1. An investigation was done to determine if the results from the student study were reproducible in an accelerated in vitro test through destruction, dilution, and dissolution of the adhesive as in oral use. MATERIAL
12 Super Corego ®
6
>o
n~ 0
A
aAssociate Professor, Department of Preclinical Techniques and Material Sciences, University of Oslo, Dental Faculty. bAssociate Professor, Department of Family Dentistry, University of Iowa, College of Dentistry. CProfessor, Department of Prosthetic Dentistry, University of Iowa, College of Dentistry. 10/1/26750
THE JOURNAL OF PROSTHETIC DENTISTRY
o
3
6
12
9
Time (~)
120 Super Corego® 90
AND METHODS
Two brands of denture adhesives (Super Corega, Stafford-Miller Ltd., Hatfield Herts, England; and Fixodent, Richardson-Vicks, Inc., Wilton, Conn.) were tested. Judging from the literature and from the pertinent patents, the main components in Super Corega adhesive are carboxymethylcellulose, a-hydroxy-v-hydroxy-poly(oxyethylenes), sodium monophosphate, and dicalciumphosphate. 1° Fixodent adhesive most probably contains sodium carboxymethylcellulose, a-hydroxy-7-hydroxy-poly(oxy-ethylenes), and glycerol. 11B o t h products are mint-flavored.
1
c e~
60
"~
1
30
0
B
0
3
6
9
12
Fig. 1. A, Retention measured as a function of time on individually adjusted acrylic resin palatal test plates with Super Corega adhesive in 25 students# Force required to dislodge plates was directly opposite to the path of insertion and was measured with an electronic bite force recorder. 12 Measurements were performed 5 minutes and 3, 6, and 10 hours after insertion of plates. Each point gives the mean value for 23 measurements, one for each student. Without adhesive, spontaneous loosening of palatal plate resulted. B, Same as for A, but individual results of each measurement have been set to 100% after 3 hours. Mean results in are given in percent after 5 minutes and after 3, 6, and 10 hours.
501
FLOYSTRAND ET AL
F i g . 2. A p p a r a t u s for measuring bond strength of denture adhesives. A, Balance scale; B, bite force recorder; C, sensory unit; D, t h e r m o s t a t e d isotonic saline b a t h with adhesive pressed between acrylic resin plate and acrylic resin b o t t o m of bath; E, two kilogram brass weight to press acrylic resin plate into place; F, bucket (110 gm); G, water reservoir.
T a b l e I. Bond strength for Fixodent and Super Corega denture adhesives T i m e (rain)
Number
M e a n (N)
Range (N)
Std D e v
SEM
CV (%)
10 10 10 10 10 10
10.2 21.1 11.9 4.9* 2.3t 0c
8.0-13.0 17.0-27.5 9.0-14.0 3.0-8.0 1.0-3.0
1.8 3.6 1.7 1.4 0.6
0.6 1.1 0.5 0.5 0.2
17.5 17.0 14.4 29.2 26.2
10 10 10 10 10 10
9.3 18.6 11.7 9.3* 6.1t 2.4
6.5-11.0 15.0-21.5 9.0-14.0 6.5-12.0 2.0-10.5 0c-5.0
1.3 2.2 1.5 1.8 2.9 1.6
0.4 0.7 0.5 0.6 0.9 0.5
13.7 11.7 13.1 19.9 48.6 65.7
Fixodent 0 a 0b
2 2 3 5 4 9 5 14 6 20
Super Corega 0 0 2 2 3 5 4 9 5 14 6 20
Adhesives measured were pressed between two acrylic resin surfaces with a diameter of 3 cm. CV, Coefficient of variation. *, tMeans are significantly different at the 0.05 level of confidence (Duncan's multiple range test). aBond strength of adhesive was measured at time 0 and at intervals of 2, 3, 4 and 6 minutes in contact with isotonic saline (applies to all values in this column). bTotal time of adhesive exposure to isotonic saline before bond strength measurement (applies to all values in this column). CResults below 1 N are not measurable and have been set at zero.
Test
apparatus
A balance scale giving a tensile stress for the adhesive was used to test the bond strength of the denture adhesives (Fig. 2). The tensile stress was raised with 2 N / m i n by use of a hydrostatic head of water adjusted to deliver a smooth stream of water to a bucket. The tensile stress was recorded
502
with a bite force recorder previously described 12 and a strip-chart recorder. The bite force recorder was adjusted to deliver 2.5 V at 10 mA to the silicone beam semiconductor in the bite fork. The speed of the strip-chart recorder was set at 0.5 cm/min.
OCTOBER 1991 VOLUME 66 NUMBER 4
TESTING
OF DENTURE
ADHESIVES
Experimental procedure The denture adhesives were tested by applying 0.3 gm of paste to a highly polished acrylic resin plate 3 cm in diameter. The acrylic resin plate was pressed into place against the polished acrylic resin bottom surface of a dry acrylic resin vessel (diameter = 11 cm) with a 2 kg brass weight for a period of 15 seconds, whereupon the first measurement was made. One hundred milliliters of isotonic saline at 37 _+ 1° C was then added to the vessel. After the acrylic surfaces with adhesive had been exposed to isotonic saline for 2 minutes, the acrylic resin plate was reseated with the 2 kg brass weight, and a new measurement was made. Subsequently the adhesive was exposed to the isotonic saline for 3 minutes. The acrylic resin plate was reseated as described previously and the adhesive bond strength was measured. This described procedure was followed with the adhesive in contact with 100 ml isotonic saline for 1 additional minute until no bond strength could be recorded (Table I). The bath of isotonic saline was kept at a constant temperature of 37 -+ 1 ° C. Ten consecutive test series were carried out for both adhesives. Between each test series, the acrylic resin plates were cleaned with tap water, by hand dried with a paper towel, wiped off with 95% ethanol, and dried once more with a paper towel. The acrylic resin plates were examined under a stereomicroscope before and after testing. No changes were observed in the surface of the plates during testing.
Statistical analysis Statistical variance analysis of the measured bond strength values was based on Duncan's multiple range test. RESULTS Bond strengths (mean, range, standard deviation, standard error of the mean, and coefficient of variation) are given in Table I. Super Corega adhesive showed significantly higher mean bond strengths than Fixodent adhesive (p < 0.05) after 9 and 14 minutes of being in contact with isotonic saline, as shown in Table I and Fig. 3. Both products gave an initial high bond strength at the 2-minute level. At the 5-minute juncture, i.e., 2 plu s 3 minutes in contact with isotonic saline, the mean bond strength of Super Corega adhesive tended to level off and declined much more slowly than that of Fixodent adhesive, giving some measure of bond strength until a total of 20 minutes of being in contact with the isotonic saline had elapsed from the onset of testing. The mean bond strength of Fixodent adhesive at the juncture of 5 minutes continued to decrease quite rapidly, and at 20 minutes from the onset of testing no measurable bond strength remained. DISCUSSION A previous study (Fig. 1) and the present investigation (Fig. 3) showed that the retention values for a denture with an ointment adhesive both in in vivo tests and in simulated
THE JOURNAL
OF PROSTHETIC
DENTISTRY
24
20
/ j~x\
16
' 7 ~ / ~ ',
Super Corega® - Fixodent~
\.T
O ~
m
~D l 0
~"
2
5
8
11
'
'
'
. . . . . .
14 17 ]]me (rain)
20
Fig. 3. Measured bond strength for Super Corega and Fixodent adhesives as a function of the total time in which adhesives were in contact with isotonic saline. Values for 20 minutes were not measurable for Fixodent adhesive. Adhesives were pressed between two acrylic resin surfaces with a diameter of 3 cm.
laboratory tests reached a maximum and then declined as a function of time. The interpretation of a similar relationship for the viscosity of an adhesive in contact with water s should explain the presently observed bond strengths. From time zero (to), the adhesive slowly absorbs water and swells with increasing viscosity until the hydrophilic high polymer particles in the adhesive attain contact with each other to form a continuous polymer matrix. This explanation agrees well with results obtained in a Texturometer evaluation test. u The subsequent decline in viscosity values s may result from a dilution effect together with destruction of the gel matrix. The fall in measured bond strengths with time as presently observed may therefore result from both dilution and destruction of the adhesive gel formed by the adhesive, together with a dissolution of the adhesive in the isotonic saline (saliva). Based on patent literature, denture adhesives appear homogeneous with respect to chemical composition. This is also indicated by the present in vitro retention tests, where the maximum bonding strength for two different adhesives coincided after 2 minutes of contact with isotonic saline. It is therefore assumed that the maximum bonding strength for both materials tested corresponds with the achieved maximum at 3 hours found for one of them in an in vivo test, 9 indicating that 2 minutes in the in vitro test is the equivalent of 3 hours in the in vivo test. Further, for Super Corega adhesive, 5 hours (Fig. 1) elapsed before the bond strength declined to the starting value in the in vivo measurement, while a total of 9 minutes in the in vitro situation brought the same result. These time values presumably are parallel for Super Corega adhesive. If this approximation is correct, Fixodent adhesive should in practical use give a better retention than the starting result (i.e., 5-minute result) for approximately the first 4.2 hours, and Super Corega adhesive likewise for the first 5 hours, with Fixodent adhesive giving some improved retention corn-
503
FL~YSTRAND ET AL
pared with Super Corega adhesive for approximately the first 3.8 hours. CONCLUSIONS The results of retention measurements obtained in an accelerated laboratory test imitating the retention of a denture with a denture ointment adhesive in vivo concur with results from in vivo experiments. 9 They parallel those of viscosity measurements on ointment denture adhesives 8 when dissolution effects are neglected. The test method described for denture adhesives seems useful to depict the fate of denture adhesives. Results obtained with this method may be taken into consideration in the choice of an adhesive with respect to its effectiveness over various periods of time. SUMMARY A method feasible for testing the retention effect, i.e., the bond strength, of denture adhesives has been presented. Two brands of adhesives were shown to have different retention properties using this method. REFERENCES 1. Chew CL, Boone ME, Swartz ML, Phillips RW. Denture adhesives: their effect on denture retention and stability. J Dent 1985;13:152-9. 2. Karlsson S, Swartz B. Denture adhesives--their effect on the mobility of full upper dentures during chewing. Swed Dent J 1981;5:207-11.
3. Tarbet WJ, Boone M, Schmidt NF. Effect of denture adhesive on complete denture dislodgement during mastication. J PROSTHET DENT 1980;44:374-8. 4. Mirza FD, Dikshit JV, Murdia NS. Effectiveness of denture adhesives at different time intervals. J Indian Dent Assoc 1983;55:9-13. 5. Mirza FD, Dikshit JV, Murdia NS. Comparative study of effectiveness of denture adhesives at different time intervals. J Indian Dent Assoc 1984;56:335-7. 6. Ow RKK, Beam EM. A method of studying the effect of adhesive on denture retention. J PROSTHET DENT 1983;50:332-7. 7. Swartz ML, Norman RD, Phillips RW. A method for measuring retention of denture adherents: an in vivo study. J PROSTHET DENT 1967;17:456-63. 8. Ellis B, A1-Nakash S. The composition and rheology of denture adhesives. J Dent 1980;8:109-18. 9. FlCystrand F, 0rstavik J. An experimental model for testing denture adhesives in vivo [Abstract]. J Dent Res 1985;64:768 and unpublished results. 10. Blomdahl M, Erichson A. Proteseadhesiver. Tandlakartidningen 1980;72:680-2. 11. Dhabhar DJ, Schmidt NF. Denture adhesive composition. European Patent Application EP 1982; 64,672 and Karaya gum adhesive in a hydrophilic denture vehicle. European Patent Application EP 1984;113,079. 12. FlCystrand F, Kleven E, Oilo G. A novel miniature bite force recorder and its clinical application. Acta Odontol Scand i982;40:209-14. Reprint requests to: DR. ROLF KOPPANG UNIVERSITYOF OSLO BOX 1052 BLINDERN 0316 OSLO 3, NORWAY
B o u n d v o l u m e s a v a i l a b l e to s u b s c r i b e r s Bound volumes of T H E JOURNAL OF PROSTHETIC DENTISTRYare available to subscribers (only) for the 1991 issues from the publisher at a cost of $50.00 ($63.00 international) for Vol. 65 (January-June) and Vol. 66 (July-December). Shipping charges are included. Each bound volume contains a subject and author index, and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Volumes 63 and 64 are also available. Payment must accompany all orders. Contact Mosby-Year Book, Inc., Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, USA; phone (800) 325-4177, ext. 4351. S u b s c r i p t i o n s m u s t be in f o r c e to q u a l i f y . B o u n d v o l u m e s a r e n o t a v a i l a b l e in p l a c e o f a r e g u l a r JOURNAL s u b s c r i p t i o n .
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OCTOBER 1991
VOLUME 66
NUMBER 4