The
contact
angles
impression
of die
stone
on
materials
Robert A. Lorren, D.D.S.,* Douglas J. Salter,** and Carl W. Fairhurst, Ph.D.*** Medical College of Georgia, School of Dentistry, Augusta, Ga.
0
bservations in the clinic at the Medical College of Georgia, School of Dentistry, indicated that certain impression materials appeared to yield casts that contained more entrapped air bubbles than appeared with other impression materials when the same die stone was used. As a result of these observations, an investigation was performed to determine the advancing contact angle of die stone on silicone, polysulfide, polyether, and colloidal impression materials. The rationale of this approach is that if the die stone forms an advancing contact angle with the impression material approximating or greater than 90 degrees, there is a high probability for entrapment of air bubbles during the pouring of the impression. If the contact angle is relatively low, there is less chance of air entrapment. MATERIALS
AND
METHODS
Table I lists the representative types of silicone, polysulfide, polyether, and hydrocolloid impression materials that were used. The die stone chosen was representative of the ADA Specification No. 25, Type IV, high-strength dental st0ne.t Each impression material was formed into sheets measuring 8 cm. in diameter and 3 mm. thick. The material was allowed to set between two glass slabs, thus creating smooth, flat surfaces. The Teflon volumetric dispenser used to release 2 ml. of die stone onto the impression material surface is shown in Fig. 1. Three specimens of die stone on each sheet of impression material from the same mix are shown in Fig. 2. The water-tostone ratio used was 25 ml. of water per 100 Gm. of powder as prescribed by the manufacturer. The stone was vacuum-mixed for 20 seconds, and specimens were made 1 minute after beginning the mix. Low-frequency vibration for 2 seconds was used to cause *Assistant
Professor,
**Certified
Dental
***Professor tVel-Mix,
176
Department Technician,
and Coordinator Kerr
Manufacturing
of Restorative Department of Dental Company,
Dentistry.
of Restorative
Materials. Romulus,
Mich.
Dentistry.
Volume Number
36 2
Die stone/impression
Fig. 1. The die stone is dispensed onto the impression dispenser Fig. 2. Three
specimens
have been produced
material
material
contact
angles
surface with a Teflon
on each sheet of impression
177
volumetric
material.
Fig. 3. A thin abrasive disc is used to groove the top side of each specimen. Fig. 4. The contact angle of a specimen was marked and measured with a compass.
the stone to flow. The frequency and time of vibration were constant for all impression materials. The die stone specimens were allowed to set for at least 1 hour before sectioning. A thin abrasive disc was used to cut a groove in the top side of each specimen (Fig. 3). The specimen was fractured along the groove, and the contact angles of both ends of one half were measured. This provided six measurements for each material. Each section was placed in a holder, set on the stage of a toolmaker’s mirroscope. and photographed, and a 4 by 5 inch print was produced. The contact angle was marked and measured with a compass on these prints (Fig. 4). Impressions of an ivorine cast were made to demonstrate the possible correlation bet!veen the observed differences in contact angles and the number of air bubble de-
178
Lorren,
A I
B
J. Prostl~et. Drnt. Augu\t, 19X
and Fairhurst
Salter,
C V
D
E
I
I
Silicone
F
H
I
I. Representative
I
w Polyether
Polysulfide
Fig. 5. Contact
Table
G
J I Hydrocolloid (reversible)
angle of die stone specimens.
types of impression
materials Batch Nos.
Materials Silicone A. Citricon* B. Silct C. Xantopren blue$ D. Traycon* Poiysulfide E. Permlastic* F. Coe-flex5 G. Mim 11 Polyether H. Polyjell I. Impregum # Hydrocolioid J. Reversible** K. Irreversible-Jeltrate *Kerr
Manufacturing
+Teledyne $Unitek
Dental
§Coe Laboratories,
41087 B 973 4083 23556
Romulus,
Company,
Monrovia, Dental
Company,
Albany,
31313 04033
72343 A021
72313 A031
Mich.
Elk Grove Village,
Ill.
111.
Products
I[The L. D. Caulk Company, Milford, #Premier Dental Products Company, **Ticonium
31304 03453 037101
Calif.
Inc., Chicago,
/IS. S. White Company,
5082 E
5712 733212
1
Company, Products
Corporation,
Accelerator
Base
N. Y.
Division,
Del. Norristown,
Philadelphia, Pa.
Pa.
K I Alginate
Volume 36 Number2
Fig. 6. Typical
Die stone/impression
dispersion
material
of air bubbles in die stone casts poured
contact
angles
in selected impression
179
ma-
terials.
fects in die stone casts. This cast contained nine onlay preparations. Three impressions each of three of the impression materials were made-Xantopren (a silicone) ,* Coeflex (a polysulfide) ,+ and Polyjel (a polyether) .$ These impressions were poured by one of the authors (D. J. S.) . The die stone was mixed in a manner similar to that used for the contact angle specimens and was allowed to flow around the arch of the impression from one end to the other, while small amounts of stone were added as needed. After separation, all bubbles on tooth surfaces prepared for restorations were counted for each cast. The same procedure was repeated, with an experienced dental assistant pouring the casts. RESULTS The contact angle observed for each material is listed in Fig. 5. The differences in contact angles among the silicone, polysulfide, and polyether as generic material groups were statistically significant at a 99 per cent confidence level. The differences between brands within each generic group were not significant. Twenty-seven die stone preparations were inspected for air bubbles in each group (Fig. 6). Fig. 7 lists the total bubble counts for the three stone casts produced from each of the three different impression material groups (silicone, polysulfide, and polyether). The total bubble count was 69 for the silicone material, 39 for the polysulfide material, and 28 for the polyether material when the casts were poured by the dental laboratory technician. The total bubble count was 56 for the silicone *Unitek Corporation, Monrovia, Calif. ‘Woe Laboratories, Inc., Chicago, Ill. $Tbe L. D. Caulk Company, Milford, Del
180
Lorren, Salter, and Fairhurst m
Dental Asst.
m
Lab. Tech
Polysulfide
I
0
IO
20
30
40 Total
50
60
70
4
80
Bubbles
Fig. 7. Total bubble count. material, 43 for the polysulfide material, and 9 for the polyether casts were poured by an experienced dental assistant.
material
when the
DISCUSSION This study demonstrates that there are distinct differences in contact angles among stone specimens dispensed against various types of impression materials. The silicone materials produced specimens with the greatest contact angles and also produced casts with greatest number of air bubbles when the die stone was mixed at the water-powder ratio normally used in clinical situations. The contact angles on the die stone specimens produced from polysulfide materials were intermediate to those of the silicone and polyether impression materials. The polyether materials produced specimens with the lowest contact angles and the fewest number of bubbles. The hydrocolloid impression materials exhibited the lowest contact angles of all impression materials. However, because they are not widely used for restorative procedures, casts were not produced from these materials. The data collected seem to correlate well with the observations derived from the clinical use of these materials. A marked increase in dies with bubble defects was found with the silicone materials. Conversely, dies poured with polyether materials seemed to contain fewer defects. CONCLUSIONS Due to the relative nonwetting characteristics (i.e., high contact angle) between die stone and silicone impression materials, a greater probability exists for air bubble defects occurring on casts produced from silicone than on casts from polysulfide or polyether materials. It is least probable that air bubble defects will be incorporated in casts produced from polyether impression materials. MEDICAL COLLEGE OF GEORGIA SCHOOL OF DENTISTRY AUGUSTA, GA. 30902
contact
angles
impression
of die
stone
on
materials
Robert A. Lorren, D.D.S.,* Douglas J. Salter,** and Carl W. Fairhurst, Ph.D.*** Medical College of Georgia, School of Dentistry, Augusta, Ga.
0
bservations in the clinic at the Medical College of Georgia, School of Dentistry, indicated that certain impression materials appeared to yield casts that contained more entrapped air bubbles than appeared with other impression materials when the same die stone was used. As a result of these observations, an investigation was performed to determine the advancing contact angle of die stone on silicone, polysulfide, polyether, and colloidal impression materials. The rationale of this approach is that if the die stone forms an advancing contact angle with the impression material approximating or greater than 90 degrees, there is a high probability for entrapment of air bubbles during the pouring of the impression. If the contact angle is relatively low, there is less chance of air entrapment. MATERIALS
AND
METHODS
Table I lists the representative types of silicone, polysulfide, polyether, and hydrocolloid impression materials that were used. The die stone chosen was representative of the ADA Specification No. 25, Type IV, high-strength dental st0ne.t Each impression material was formed into sheets measuring 8 cm. in diameter and 3 mm. thick. The material was allowed to set between two glass slabs, thus creating smooth, flat surfaces. The Teflon volumetric dispenser used to release 2 ml. of die stone onto the impression material surface is shown in Fig. 1. Three specimens of die stone on each sheet of impression material from the same mix are shown in Fig. 2. The water-tostone ratio used was 25 ml. of water per 100 Gm. of powder as prescribed by the manufacturer. The stone was vacuum-mixed for 20 seconds, and specimens were made 1 minute after beginning the mix. Low-frequency vibration for 2 seconds was used to cause *Assistant
Professor,
**Certified
Dental
***Professor tVel-Mix,
176
Department Technician,
and Coordinator Kerr
Manufacturing
of Restorative Department of Dental Company,
Dentistry.
of Restorative
Materials. Romulus,
Mich.
Dentistry.
Volume Number
36 2
Die stone/impression
Fig. 1. The die stone is dispensed onto the impression dispenser Fig. 2. Three
specimens
have been produced
material
material
contact
angles
surface with a Teflon
on each sheet of impression
177
volumetric
material.
Fig. 3. A thin abrasive disc is used to groove the top side of each specimen. Fig. 4. The contact angle of a specimen was marked and measured with a compass.
the stone to flow. The frequency and time of vibration were constant for all impression materials. The die stone specimens were allowed to set for at least 1 hour before sectioning. A thin abrasive disc was used to cut a groove in the top side of each specimen (Fig. 3). The specimen was fractured along the groove, and the contact angles of both ends of one half were measured. This provided six measurements for each material. Each section was placed in a holder, set on the stage of a toolmaker’s mirroscope. and photographed, and a 4 by 5 inch print was produced. The contact angle was marked and measured with a compass on these prints (Fig. 4). Impressions of an ivorine cast were made to demonstrate the possible correlation bet!veen the observed differences in contact angles and the number of air bubble de-
178
Lorren,
A I
B
J. Prostl~et. Drnt. Augu\t, 19X
and Fairhurst
Salter,
C V
D
E
I
I
Silicone
F
H
I
I. Representative
I
w Polyether
Polysulfide
Fig. 5. Contact
Table
G
J I Hydrocolloid (reversible)
angle of die stone specimens.
types of impression
materials Batch Nos.
Materials Silicone A. Citricon* B. Silct C. Xantopren blue$ D. Traycon* Poiysulfide E. Permlastic* F. Coe-flex5 G. Mim 11 Polyether H. Polyjell I. Impregum # Hydrocolioid J. Reversible** K. Irreversible-Jeltrate *Kerr
Manufacturing
+Teledyne $Unitek
Dental
§Coe Laboratories,
41087 B 973 4083 23556
Romulus,
Company,
Monrovia, Dental
Company,
Albany,
31313 04033
72343 A021
72313 A031
Mich.
Elk Grove Village,
Ill.
111.
Products
I[The L. D. Caulk Company, Milford, #Premier Dental Products Company, **Ticonium
31304 03453 037101
Calif.
Inc., Chicago,
/IS. S. White Company,
5082 E
5712 733212
1
Company, Products
Corporation,
Accelerator
Base
N. Y.
Division,
Del. Norristown,
Philadelphia, Pa.
Pa.
K I Alginate
Volume 36 Number2
Fig. 6. Typical
Die stone/impression
dispersion
material
of air bubbles in die stone casts poured
contact
angles
in selected impression
179
ma-
terials.
fects in die stone casts. This cast contained nine onlay preparations. Three impressions each of three of the impression materials were made-Xantopren (a silicone) ,* Coeflex (a polysulfide) ,+ and Polyjel (a polyether) .$ These impressions were poured by one of the authors (D. J. S.) . The die stone was mixed in a manner similar to that used for the contact angle specimens and was allowed to flow around the arch of the impression from one end to the other, while small amounts of stone were added as needed. After separation, all bubbles on tooth surfaces prepared for restorations were counted for each cast. The same procedure was repeated, with an experienced dental assistant pouring the casts. RESULTS The contact angle observed for each material is listed in Fig. 5. The differences in contact angles among the silicone, polysulfide, and polyether as generic material groups were statistically significant at a 99 per cent confidence level. The differences between brands within each generic group were not significant. Twenty-seven die stone preparations were inspected for air bubbles in each group (Fig. 6). Fig. 7 lists the total bubble counts for the three stone casts produced from each of the three different impression material groups (silicone, polysulfide, and polyether). The total bubble count was 69 for the silicone material, 39 for the polysulfide material, and 28 for the polyether material when the casts were poured by the dental laboratory technician. The total bubble count was 56 for the silicone *Unitek Corporation, Monrovia, Calif. ‘Woe Laboratories, Inc., Chicago, Ill. $Tbe L. D. Caulk Company, Milford, Del
180
Lorren, Salter, and Fairhurst m
Dental Asst.
m
Lab. Tech
Polysulfide
I
0
IO
20
30
40 Total
50
60
70
4
80
Bubbles
Fig. 7. Total bubble count. material, 43 for the polysulfide material, and 9 for the polyether casts were poured by an experienced dental assistant.
material
when the
DISCUSSION This study demonstrates that there are distinct differences in contact angles among stone specimens dispensed against various types of impression materials. The silicone materials produced specimens with the greatest contact angles and also produced casts with greatest number of air bubbles when the die stone was mixed at the water-powder ratio normally used in clinical situations. The contact angles on the die stone specimens produced from polysulfide materials were intermediate to those of the silicone and polyether impression materials. The polyether materials produced specimens with the lowest contact angles and the fewest number of bubbles. The hydrocolloid impression materials exhibited the lowest contact angles of all impression materials. However, because they are not widely used for restorative procedures, casts were not produced from these materials. The data collected seem to correlate well with the observations derived from the clinical use of these materials. A marked increase in dies with bubble defects was found with the silicone materials. Conversely, dies poured with polyether materials seemed to contain fewer defects. CONCLUSIONS Due to the relative nonwetting characteristics (i.e., high contact angle) between die stone and silicone impression materials, a greater probability exists for air bubble defects occurring on casts produced from silicone than on casts from polysulfide or polyether materials. It is least probable that air bubble defects will be incorporated in casts produced from polyether impression materials. MEDICAL COLLEGE OF GEORGIA SCHOOL OF DENTISTRY AUGUSTA, GA. 30902
