The bond strength of elastomer tray adhesives thermoplastic and acrylic resin tray materials William Walter
R. Hogans
III,
Reed Army Medical
DDS,a
and John
Center, Washington,
R. Agar,
DDS,
to
MSb
D.C.
This study evaluated the bond strength of selected impression materials (Permlastic, Express, and Hydrosil) to a thermoplastic custom tray material as a function of drying time of the adhesive after application to a tray material. In addition, bond strengths of a polysulfide impression material to an acrylic resin tray material and to a thermoplastic tray material made directly against wax were evaluated. Bond strengths were obtained directly from values of applied load at failure and important conclusions were drawn. (J PROSTHET DENT 1992;67:541-3.)
S
everal investigators have concluded that the most consistently accurate impressions were obtained with the adhesive-lined resin custom tray.le4 Davis et a1.5investigated the bonding properties of elastomer tray adhesives and concluded that surface preparation of the tray significantly affected the retention of the impression material. Trays prepared over a wax spacer yielded lower bond strength values than those prepared over a wax spacer covered with tinfoil. Furthermore, their study suggested that drying time variances of 15 minutes to 72 hours did not significantly affect the tray adhesive bond strengths. However, drying times of less than 15 minutes reduced the bond strength values for polysulfide materials to a custom acrylic resin tray with the appropriate adhesive. A new thermoplastic material, E-Z Tray (Oral Dynamics Inc., Seattle, Wash.), was recently marketed as a rapid, simple method for making stable custom impression trays. In a recent study, Gordon et a1.6investigated the effect of tray selection on the accuracy of elastomeric impression materials. Their results suggested that custom-made trays of acrylic resin or thermoplastic material produced equally acceptable clinical results. However, they found that the use of stock plastic trays produced impressions exhibiting greater dimensional change than those made from the custom trays. This study evaluated the bond strengths of selected impression materials to a thermoplastic custom tray material
Commercial materials and equipment are identified in this report to specify the investigative procedures. Such identification does not imply recommendation or endorsement or that the material and equipment are necessarily the best available for the purpose. The opinions expressed herein are those of the authors and are not to be construed as official or as reflecting the views of the U.S. Army Medical Department. aLieutenant Colonel, U.S. Army, DC; Senior resident, Advanced Education Program in Prosthodontics. bColonel, U.S. Army, DC; Director, Advanced Education Program in Prosthodontics. 1011125744
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table
I.
Impression material and adhesives used in
study Material and manufacturer 1 Express 3M 3M Dental Products Division, St. Paul, Minn. 2 Kerr Permlastic Kerr/Sybron, Romulus, Mich. 3 Hydrosil L. D. Caulk Co., Milford, Del.
Batch No.
Adhesive
P89011 Regular body
Express 3M
92054 Regular body
Kerr
111788
Caulk
as a function of drying time of the adhesive after application to the tray material. In addition, bond strengths of a polysulfide impression material to an acrylic resin tray material and to a thermoplastic tray material made directly against wax were evaluated. MATERIAL
AND
METHODS
The impression materials, their manufacturers, and respective tray adhesives are listed in Table I. One-inchsquare perforated brass plates were constructed with a brass hook soldered to the center opposite the test surface (Fig. 1). The thermoplastic material was placed in a water bath at 180’ F for 60 seconds until it was plastic and easily deformed without recovery. Specimens for the evaluation of adhesive drying time were made by molding the thermoplastic and acrylic resin tray materials over a tinfoilcovered wax sheet in a l-inch “square silicone mold.” A brass hook with retentive threads was embedded in the tray material (VSI Fasteners, Inc., Stanton, Calif.) (Fig. 2). The tray samples and perforated brass plates were painted with the appropriate adhesive and were permitted to air dry for selected time intervals of 5 minutes, 15 minutes, 1 hour, and 24 hours. At the end of the specific time interval, the impression materials were dispensed and hand spatulated in
541
HOGANS
Fig.
AND
AGAR
1. Perforated brass plate with brass hook.
Fig. 3. Schematic diagram of specimen on mechanical testing machine.
Fig. 2. Thermoplastic sample with hook (left) and acrylic resin sample with hook (‘right).
accordance with the respective manufacturer’s instructions. The mixed materials were placed between the perforated plate and the tray samples. The plate and tray material were separated by G-inch-thick spacers to maintain a constant thickness of impression material. The assembled specimens were placed in a humidor at 37OC and 50 + 10% relative humidity and were permitted to set for 10 minutes. Upon removal from the humidor, excessmaterial was removed with a sharp knife. Samples for the evaluation of tray fabrication technique as well as the acrylic resin specimens were made in a similar manner, except that one group of thermoplastic tray sections was formed directly against the wax spacer. A drying time of 15 minutes for the adhesive was selected for this portion of the study. Each specimen assembly was placed in a mechanical testing machine (Universal Testing Machine, Instron Corp., Canton, Mass.) and tensile forces were applied at a cross-
542
head speed of 20 in/min (Fig. 3). Bond strengths were obtained directly from values of applied load at failure. Specimens that failed at the perforated brass plate and elastomeric material interface were discarded. The failure of the Express 3M was at the interface between the adhesive and the impression or tray material. Polysulfide had some cohesive failure of the impression material. Ten specimens were reported for each material, time interval, and fabrication technique. Bond strength values as a function of time and impression material were subjected to a fixed-model two-way analysis of variance and means were compared using Scheffe’s method at the 5 % level of significance. Comparisons of fabrication technique for the thermoplastic material and the acrylic resin material were subjected to a one-way analysis of variance and mean values were compared using Scheffe’s method at the 5% level of significance. RESULTS The bond strength of the impression materials to the thermoplastic tray material as a function of time is shown in Table II. Mean bond strength values for Permlastic and Express 3M ranged from about 50 to 57 psi and from 81 to 91 psi, respectively. Coefficients of variation ranged from 7 % (Express 3M at 24 hours) to 25 % (Permlastic at 5 minutes). Time was not a significant variable for either of the impression materials (p > 0.05).
APRIL
1992
VOLUME
67
NUMBER
4
BOND
Table
STRENGTH
OF TRAY
ADHESIVES
II. Bond strengths as function of impression material and adhesive drying times Drying 5 min
Material
Permlastic Express
49.9(12.3)* 81.4(7.9)
times
15 min
24 hr
1 hr
55.8(8.3)
51.2(8.4)
57.3(14.4)
86.9(12.8)
82.8(11.3)
90.6(6.7)
*Mean values (in pounds _ per square _ inch lpsil) with standard deviations in parentheses. Scheff(?allowances were calculated to be 4.8 psi and 9.7 psi for materials and time, respectively, at the 5% level of significance.
Bond strength values for Express 3M impression material were significantly higher (p > 0.05) than those for Permlastic at any given time interval. Bond strength values for the addition-silicone material ranged from 56% (at 15 minutes) to 63% (at 5 minutes) higher than those for the polysulfide material. The values for the Hydrosil impression material/tray adhesive system were not included in the analysis because their high adhesive tensile strength exceeded the design of the experiment. Data for the bonding of Permlastic impression material/ adhesive to the thermoplastic tray materials as a function of the fabrication technique and to the acrylic resin material formed over tinfoil are shown in Table III. Values for the Permlastic impression material/adhesive system bonded to the thermoplastic material formed directly over a wax spacer were significantly lower than those for Permlastic bonded to the thermoplastic material or to the acrylic resin tray material formed over tinfoil. DISCUSSION From the available data, it would appear that the thermoplastic tray material exhibited bond strength values similar to those observed for acrylic resin tray materials when a polysulfide impression material was used with the appropriate adhesive. Furthermore, the amount of time that the adhesive was permitted to dry prior to application of the impression material had no significant effect on the bond strength values for either impression material/adhesive system. These data suggest that the tray adhesive may be applied any time between 5 minutes or 1 day prior to using a custom tray with no adverse effects on the bonding of the impression material to the tray. When the thermoplastic material was heated to 180” F and formed over wax, as suggested by the instructions supplied with the material, a significant decrease was found in bond strength of the polysulfide/adhesive system. Thermoplastic material should not contact wax during the construction of custom impression trays. CONCLUSIONS 1. In the systems evaluated, the drying times of tray adhesives 5 minutes prior to application of the impression material had no significant effect upon bond strength of the impression material to the impression tray.
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table III. Bond strengths for Permlastic as a function of surface preparation and tray material after 15 minutes of adhesive drying time Bond Material
E-Z Tray/foil E-Z Tray/wax Acrylic resin/foil
strength (psi)
55.7(8.3)* 23.7(6.5)
48.2(9.1)
*Mean values with standard deviations in parentheses. Scheffb allowances were calculated to be 9.3 psi at 5% level of significance.
2. The bond strength of the addition-silicone material/ adhesive, Express 3M, was significantly higher than that of the polysulfide material/adhesive, Permlastic. 3. The bonding of the polysulfide impression material/ adhesive system to the thermoplastic tray material was not different from the bonding to the acrylic resin tray material. 4. Making thermoplastic tray materials directly against wax spacers significantly reduced the bond strength of the polysulfide impression material/adhesive system to the tray. REFERENCES 1. Nicholson JW, Porter KH, Dolan T. Strength of tray adhesives for elastomeric impression materials. Oper Dent 1985;10:12-6. 2. Tjan AHL, Whang SB. Comparing effects of tray treatment on the accuracy of dies. J PROSTHET DENT 1987;58:175-8. 3. Grant BE, Tjan AHL. Tensile and peel bond strengths of tray adhesives. J PROSTHET DENT 1988,59:165-S. 4. Bomberg TJ, Goldfogel MH, Hoffman W, Bomberg SE. Considerations for adhesion of impression materials to impression trays. J PROSTHET DENT 1988;60:681-4. 5. Davis GB, Moser JB, Brinsden GI. The bonding properties of elastomer tray adhesives. J PROSTHET DENT 1976;36:278-85. 6. Gordon GE, Johnson GH, Drennon DG. The effect of tray selection on the accuracy of elastomeric impression materials. J PROSTHET DENT 1990:63:12-5. Reprint requests to: DR. WILLIAM R. HOGANS, III US. ARMY DENTAL ACTIVITY HOSPITAL DENTAL CLINIC WALTER REED ARMY MEDICAL CENTER WASHINGTON, DC 20307.5400
543
R. Hogans
III,
Reed Army Medical
DDS,a
and John
Center, Washington,
R. Agar,
DDS,
to
MSb
D.C.
This study evaluated the bond strength of selected impression materials (Permlastic, Express, and Hydrosil) to a thermoplastic custom tray material as a function of drying time of the adhesive after application to a tray material. In addition, bond strengths of a polysulfide impression material to an acrylic resin tray material and to a thermoplastic tray material made directly against wax were evaluated. Bond strengths were obtained directly from values of applied load at failure and important conclusions were drawn. (J PROSTHET DENT 1992;67:541-3.)
S
everal investigators have concluded that the most consistently accurate impressions were obtained with the adhesive-lined resin custom tray.le4 Davis et a1.5investigated the bonding properties of elastomer tray adhesives and concluded that surface preparation of the tray significantly affected the retention of the impression material. Trays prepared over a wax spacer yielded lower bond strength values than those prepared over a wax spacer covered with tinfoil. Furthermore, their study suggested that drying time variances of 15 minutes to 72 hours did not significantly affect the tray adhesive bond strengths. However, drying times of less than 15 minutes reduced the bond strength values for polysulfide materials to a custom acrylic resin tray with the appropriate adhesive. A new thermoplastic material, E-Z Tray (Oral Dynamics Inc., Seattle, Wash.), was recently marketed as a rapid, simple method for making stable custom impression trays. In a recent study, Gordon et a1.6investigated the effect of tray selection on the accuracy of elastomeric impression materials. Their results suggested that custom-made trays of acrylic resin or thermoplastic material produced equally acceptable clinical results. However, they found that the use of stock plastic trays produced impressions exhibiting greater dimensional change than those made from the custom trays. This study evaluated the bond strengths of selected impression materials to a thermoplastic custom tray material
Commercial materials and equipment are identified in this report to specify the investigative procedures. Such identification does not imply recommendation or endorsement or that the material and equipment are necessarily the best available for the purpose. The opinions expressed herein are those of the authors and are not to be construed as official or as reflecting the views of the U.S. Army Medical Department. aLieutenant Colonel, U.S. Army, DC; Senior resident, Advanced Education Program in Prosthodontics. bColonel, U.S. Army, DC; Director, Advanced Education Program in Prosthodontics. 1011125744
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table
I.
Impression material and adhesives used in
study Material and manufacturer 1 Express 3M 3M Dental Products Division, St. Paul, Minn. 2 Kerr Permlastic Kerr/Sybron, Romulus, Mich. 3 Hydrosil L. D. Caulk Co., Milford, Del.
Batch No.
Adhesive
P89011 Regular body
Express 3M
92054 Regular body
Kerr
111788
Caulk
as a function of drying time of the adhesive after application to the tray material. In addition, bond strengths of a polysulfide impression material to an acrylic resin tray material and to a thermoplastic tray material made directly against wax were evaluated. MATERIAL
AND
METHODS
The impression materials, their manufacturers, and respective tray adhesives are listed in Table I. One-inchsquare perforated brass plates were constructed with a brass hook soldered to the center opposite the test surface (Fig. 1). The thermoplastic material was placed in a water bath at 180’ F for 60 seconds until it was plastic and easily deformed without recovery. Specimens for the evaluation of adhesive drying time were made by molding the thermoplastic and acrylic resin tray materials over a tinfoilcovered wax sheet in a l-inch “square silicone mold.” A brass hook with retentive threads was embedded in the tray material (VSI Fasteners, Inc., Stanton, Calif.) (Fig. 2). The tray samples and perforated brass plates were painted with the appropriate adhesive and were permitted to air dry for selected time intervals of 5 minutes, 15 minutes, 1 hour, and 24 hours. At the end of the specific time interval, the impression materials were dispensed and hand spatulated in
541
HOGANS
Fig.
AND
AGAR
1. Perforated brass plate with brass hook.
Fig. 3. Schematic diagram of specimen on mechanical testing machine.
Fig. 2. Thermoplastic sample with hook (left) and acrylic resin sample with hook (‘right).
accordance with the respective manufacturer’s instructions. The mixed materials were placed between the perforated plate and the tray samples. The plate and tray material were separated by G-inch-thick spacers to maintain a constant thickness of impression material. The assembled specimens were placed in a humidor at 37OC and 50 + 10% relative humidity and were permitted to set for 10 minutes. Upon removal from the humidor, excessmaterial was removed with a sharp knife. Samples for the evaluation of tray fabrication technique as well as the acrylic resin specimens were made in a similar manner, except that one group of thermoplastic tray sections was formed directly against the wax spacer. A drying time of 15 minutes for the adhesive was selected for this portion of the study. Each specimen assembly was placed in a mechanical testing machine (Universal Testing Machine, Instron Corp., Canton, Mass.) and tensile forces were applied at a cross-
542
head speed of 20 in/min (Fig. 3). Bond strengths were obtained directly from values of applied load at failure. Specimens that failed at the perforated brass plate and elastomeric material interface were discarded. The failure of the Express 3M was at the interface between the adhesive and the impression or tray material. Polysulfide had some cohesive failure of the impression material. Ten specimens were reported for each material, time interval, and fabrication technique. Bond strength values as a function of time and impression material were subjected to a fixed-model two-way analysis of variance and means were compared using Scheffe’s method at the 5 % level of significance. Comparisons of fabrication technique for the thermoplastic material and the acrylic resin material were subjected to a one-way analysis of variance and mean values were compared using Scheffe’s method at the 5% level of significance. RESULTS The bond strength of the impression materials to the thermoplastic tray material as a function of time is shown in Table II. Mean bond strength values for Permlastic and Express 3M ranged from about 50 to 57 psi and from 81 to 91 psi, respectively. Coefficients of variation ranged from 7 % (Express 3M at 24 hours) to 25 % (Permlastic at 5 minutes). Time was not a significant variable for either of the impression materials (p > 0.05).
APRIL
1992
VOLUME
67
NUMBER
4
BOND
Table
STRENGTH
OF TRAY
ADHESIVES
II. Bond strengths as function of impression material and adhesive drying times Drying 5 min
Material
Permlastic Express
49.9(12.3)* 81.4(7.9)
times
15 min
24 hr
1 hr
55.8(8.3)
51.2(8.4)
57.3(14.4)
86.9(12.8)
82.8(11.3)
90.6(6.7)
*Mean values (in pounds _ per square _ inch lpsil) with standard deviations in parentheses. Scheff(?allowances were calculated to be 4.8 psi and 9.7 psi for materials and time, respectively, at the 5% level of significance.
Bond strength values for Express 3M impression material were significantly higher (p > 0.05) than those for Permlastic at any given time interval. Bond strength values for the addition-silicone material ranged from 56% (at 15 minutes) to 63% (at 5 minutes) higher than those for the polysulfide material. The values for the Hydrosil impression material/tray adhesive system were not included in the analysis because their high adhesive tensile strength exceeded the design of the experiment. Data for the bonding of Permlastic impression material/ adhesive to the thermoplastic tray materials as a function of the fabrication technique and to the acrylic resin material formed over tinfoil are shown in Table III. Values for the Permlastic impression material/adhesive system bonded to the thermoplastic material formed directly over a wax spacer were significantly lower than those for Permlastic bonded to the thermoplastic material or to the acrylic resin tray material formed over tinfoil. DISCUSSION From the available data, it would appear that the thermoplastic tray material exhibited bond strength values similar to those observed for acrylic resin tray materials when a polysulfide impression material was used with the appropriate adhesive. Furthermore, the amount of time that the adhesive was permitted to dry prior to application of the impression material had no significant effect on the bond strength values for either impression material/adhesive system. These data suggest that the tray adhesive may be applied any time between 5 minutes or 1 day prior to using a custom tray with no adverse effects on the bonding of the impression material to the tray. When the thermoplastic material was heated to 180” F and formed over wax, as suggested by the instructions supplied with the material, a significant decrease was found in bond strength of the polysulfide/adhesive system. Thermoplastic material should not contact wax during the construction of custom impression trays. CONCLUSIONS 1. In the systems evaluated, the drying times of tray adhesives 5 minutes prior to application of the impression material had no significant effect upon bond strength of the impression material to the impression tray.
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Table III. Bond strengths for Permlastic as a function of surface preparation and tray material after 15 minutes of adhesive drying time Bond Material
E-Z Tray/foil E-Z Tray/wax Acrylic resin/foil
strength (psi)
55.7(8.3)* 23.7(6.5)
48.2(9.1)
*Mean values with standard deviations in parentheses. Scheffb allowances were calculated to be 9.3 psi at 5% level of significance.
2. The bond strength of the addition-silicone material/ adhesive, Express 3M, was significantly higher than that of the polysulfide material/adhesive, Permlastic. 3. The bonding of the polysulfide impression material/ adhesive system to the thermoplastic tray material was not different from the bonding to the acrylic resin tray material. 4. Making thermoplastic tray materials directly against wax spacers significantly reduced the bond strength of the polysulfide impression material/adhesive system to the tray. REFERENCES 1. Nicholson JW, Porter KH, Dolan T. Strength of tray adhesives for elastomeric impression materials. Oper Dent 1985;10:12-6. 2. Tjan AHL, Whang SB. Comparing effects of tray treatment on the accuracy of dies. J PROSTHET DENT 1987;58:175-8. 3. Grant BE, Tjan AHL. Tensile and peel bond strengths of tray adhesives. J PROSTHET DENT 1988,59:165-S. 4. Bomberg TJ, Goldfogel MH, Hoffman W, Bomberg SE. Considerations for adhesion of impression materials to impression trays. J PROSTHET DENT 1988;60:681-4. 5. Davis GB, Moser JB, Brinsden GI. The bonding properties of elastomer tray adhesives. J PROSTHET DENT 1976;36:278-85. 6. Gordon GE, Johnson GH, Drennon DG. The effect of tray selection on the accuracy of elastomeric impression materials. J PROSTHET DENT 1990:63:12-5. Reprint requests to: DR. WILLIAM R. HOGANS, III US. ARMY DENTAL ACTIVITY HOSPITAL DENTAL CLINIC WALTER REED ARMY MEDICAL CENTER WASHINGTON, DC 20307.5400
543
