- Email: [email protected]
Biologic and physical properties of a zinc polycar☐ylate cement
Operative dentistry
Biologic
and
physical
polycarboxylate
properties
of a zinc
cement
M. D. Jendresen, D.D.S.,* and H. 0. Trowbridge, D.D.S., Ph.D.** School of Dentistry, University of California, San Francisco, Calif.
T
In the past four years, since the development and introduction of a new dental cement by D. C. Smith,’ there have been several reports dealing with this new product, generally referred to as polycarboxylate cementzs6 These reports have dealt mainly with the mechanical, physical, and chemical properties of the carboxylate cements, although some data have been published on the biologic properties for this cement using animal models.8~9 The purpose of this investigation was to characterize one of the recently developed and available carboxylate cements as to both its biologic and physical properties. A zinc polycarboxylate, manufactured by S. S. White Company and sold as PCA,t was chosen. Biologic properties were evaluated by studying responses of the human dental pulp. Physical properties were evaluated by conventional laboratory tests for compressive and tensile strength, solubility, film thickness, and setting time. METHOD-BIOLOGIC
PROPERTIES
A screening-type experimental design was established to evaluate the pulpal response induced by this zinc polycarboxylate cement and two different cements used as controls. A zinc oxide and eugenol cement was used as a standard to illustrate a mild pulpal response, and a zinc phosphate cement was used as an additional control to illustrate a moderate or severe pulpal response. These cements are identified in Table I. The selection and clinical requirements established for this part of the study were those outlined by Stanley.’ Standardized Class V cavity preparations were made on the facial surfaces in the Portions of this article tion for Dental Research, Palo Alto, Calif.
were presented at the annual meeting of the International AssociaChicago, Ill., and at the Pacific Coast Society of Prosthodontics,
*Associate Professor and Chairman, **Associate Professor of Pathology, +Polycarboxylate 264
cement.
Biomaterials Science. School of Dentistry and School of Medicine.
Properties of zinc polycarboxylate
cements
265
Table I. Cements Cement
Manufacturer
We
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate
2200 PCA
L. D. Caulk Company S. S. White Company
Flecks
M&y,
Inc.
Table II. Day 5 Material
Average
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate *Degrees
of pathologic
fR. D., remaining
response* 0.4 1.0 2.4
Average R.D.f (mm.1 0.76 0.75 0.62
response (0 to 4).
dentin
thickness.
cervical region of 45 intact human teeth not previously restored. A No, 3P pearshaped carbide bur was used at a speed of 300,000 r.p.m. with an air-water spray. Fifteen teeth were restored with each of the cements. No cavity liners, varnishes, or pulp protective measures were used in any instance. All restorative procedures were conducted with the aid of a rubber dam to better control the operating site. Four patients were involved, and each patient had nearly equal numbers of test and control restorations placed. The patients were men 35 to 45 years of age who were scheduled for full mouth extractions due to pending prosthodontic treatment. At postoperative intervals of 5, 21, and 90 days, 5 teeth were extracted for each of the three cement types placed. This provided 5 teeth for each category (both experimental and control) and for each time interval. Test and control teeth in the same patient were extracted at the same sitting. Immediately following extraction, the teeth were placed in paraformaldehyde solution (4.0 per cent) and decalcified and processed for histopathologic interpretation. The various cements and time intervals were compared by recording the incidence and average intensities of pulpal response through loss of odontoblasts and the inflammatory response in the superficial tissues (odontoblastic layer) and the deeper tissues of the pulp. The intensity of this pulpal response was recorded according to an arbitrary scale (0 to 4) . RESULTCBIOLOGIC
PROPERTIES
The results for the three cements at 5 days postoperatively are shown in Table If. The specimens restored with zinc oxide and eugenol had a minimal response followed closely by the zinc polycarboxylate, which elicited a mild response in contrast to the zinc phosphate material, which produced a measurably stronger or moderate response. In each category, the average remaining dentin thickness (R.D.) was smaller than 1.0 mm. The results at the 21 day interval showed greater differentiation between the cements compared. Table III illustrates the average response for zinc phosphate cement as 4, which is considered severe and indicates abscess formation; whereas,
266
Jendresen
J. Prosthet. Dent. September, 1972
and Trowbridge
21 days after placement of zinc phosphate cement. The Iremalining Fig. 1. Abscess formation rating is 4 on a 0 to 4 scale dent in thickness is 0.25 mm., and the pathology
Tab de III. Day 21 Material
Average response*
Average R.D.T (mm.)
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate
0.4 1.4 4.0
0.35 0.49 0.32
*Degrees
of pathologic
tR. D., remaining
response (0 to 4).
dentin thickness.
the other two cements showed little change from the previous time interval. Again, note the remaining dentin thickness. Fig. 1 shows a specimen restored with zinc phosphate cement at the 21 day interval. The R.D. is 0.25 mm., and the pathology rating is 4. The abscess formation is well defined. Fig. 2 is a specimen containing zinc polycarboxyIate at the same time and magnification with an R.D. of 0.20 mm. which produced a pulpal response noted as 1.
Properties
of zin(.
polycarhorylate
Fig. 2. Pulpal response to zinc polycarboxylate at 21 days. The rtmainirq 0.2 mm. The tissue response, considered minimal, was rated a, 1.
c‘emrnf,i
dentin
thickness
lab de IV. Day 90 Material
of pathologic
jR. D.. remaining
I-
-.. Acerage
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate *Degrees
267
response* 0.0 0.3 4.0
I /
,4r’erage R.D.t (mm.) 0.44 o.i5 0.44
response (0 to 4)
dentin thickness,
Ninety-day data indicate a reduction in average intensity scores for the zinc polpcarboxylate and a continued high intensity of response for the zinc phosphate cwnent. These data are shown in Table IV. It is not unusual that any restorative material registers a higher reaction w intensity score than zinc oxide and eugenol. Although the other materials, when used, may initially produce a higher average response than the zinc oxide and eugenol con-
268
Jendresen
Fig. 3. Localized phosphate
cement.
and Trowbridge
J. Prosthet. Dent. September,
1972
chronic inflammatory cells shown at 90 days following placement of zinc The remaining dentin thickness is 0.7 mm. The tissue response was 4.
trol, their average intensity scores should decrease significantly in the longer postoperative intervals in order to be considered as eliciting a favorable response. This favorable situation is seen for the zinc polycarboxylate and is not seen for the more irritating zinc phosphate cement. An example is shown in Fig. 3: zinc phosphate cement at 90 days with an R.D. of 0.7 mm., an abscess formation, and a rating of 4. A contrast is seen in Fig. 4: the zinc polycarboxylate at 90 days with an R.D. of 0.6 mm. and a pulpal response of 0. Table V shows the average responses in each category for the total sample. This illustrates the trend of pulpal response for the various cements. The average responses for zinc oxide and eugenol and zinc polycarboxylate cements are mild throughout the test period, but the pulp responses to the zinc phosphate cement go from moderate to severe. PHYSICAL
PROPERTIES
To further characterize this zinc polycarboxylate, selected physical properties were evaluated in the conventional manner. Table VI illustrates the results for tests of film
ProperGs
of
zinc polycarboxylate
ceme7zt.r
cement at 90 days. The remaining Fig. 4. Pulpal response to zinc polycarboxylate ness is 0.6 mm., and the pulpal response was graded as I),
dentin
269
thick-
thickness, solubility, and setting tiine obtained as prescribed in the A.D.A. Specification NO. 8 for zinc phosphate cement. Working-time data were obtained from a subjective test that indicated a time when the cement became stringy and less desirable to handle from a clinical viewpoint. In all tests, the powder/liquid ratio was 1.5;‘1 .O by weight. Compressive strength data were obtained on cylindrical specimens 6 by 12 mm. according to A.D.A. Specification No. 8. The diametral tensile strength values were determined from specimens of the sarne dimensions using the Instron universal testing machine at a loading rate of 0.02 inch per minute. The adhesion properties for this zinc polycarboxylatr were drtermined for metalto-metal adhesion and for metal-to-tooth enamel adhesion. The metal-to-metal specimens were orthodontic lingual buttons of stainless steel. The surfaces were sandblasted and cemented together. Prior to the actual adhesion test, the specimens were stored in water at 37’ C. for 3 hours. The adhesion test-frame apparatus consisted of keyed aluminum clamps affixed to the top of the crosshead of an Instron machine in such a manner as to permit eas:
270
Jendresen
J. Prosthet. Dent. September, 1972
and Trowbridge
Table V. Summary
of average responses
Cement
Day 5
I
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate
I
0.4 1.0 2.4
Day 21
I
0.4 1.4 4.0
Day 90 0.0 0.5 4.0
Table VI. Zinc polycarboxylate Powder/liquid Film thickness Solubility Setting time Working time* *Subjective
1.5/1.0 22 p 0.1 per cent 7% minutes 2 minutes
test.
Table VII. Zinc polycarboxylate Age (hours)
p.s.i.
SD*
nt
Compressive
24
8900
500
30
Tensile
24
700
160
30
3 3
1300 800
260 195
15 58
Strength
(diametral)
Adhesive (tensile) Metal to metal Metal to tooth enamel *SD, Standard tn, number
deviation.
of specimens tested.
centering of the test button under the lifting hook suspended from the tensile load cell. The lifting hook was connected to the load cell through a short length of flexible steel chain in order to compensate for minor variations in orientation. This provided that the applied force was as close to being purely tensile as possible. A loading rate of 0.02 inch per minute was used for the adhesion tests. The metal-to-tooth enamel specimens were tested in a similar fashion with the same mechanical arrangement. Extracted human teeth were used. They were mounted in dental stone with the labial surfaces positioned on a plane with the top surface of the mounting ring and stone. The specimens were kept wet until testing. The surfaces of the test teeth were prepared by polishing with a pumice-water slurry solution using a dental handpiece at slow speed. Specimens were rinsed with water, and this was followed by a scrubbing with an alcohol-soaked cotton swab. The cleaned surfaces dried through evaporation as the cement mix was made. Again, stainless steel orthodontic lingual buttons were used. These were cemented and positioned so as to fit in the previously described adhesion test-frame apparatus. Care was taken during cementation to achieve a uniform film thickness. The specimens were stored in water at 37’ C. for 3 hours before testing. The results for these tests are shown in Table VII.
Properties
of zinc
polycarboxylate
cement.c
271
From the data presented in this report on selected biologic and physical propertirs of a zinc polycarboxylate cement, it appears that this cement is well tolerated by the human pulp tissue and has good physical properties. References 1. Smith, D. C.: A New Dental Cement, Br. Dent. J. 125: 381-384, 1968. 2. Mizrahi, E., and Smith, D. C.: The Bond Strength of a Zinc Polycarboxylate Cement, Hr. Dent. J. 127: 410-414, 1969. 3. Friend, L. A.: Handling Properties of a Zinc Polycarboxylate Cement, Br. Dent. J. 127: 3.59-364, 1969. Laboratory Evaluation of Pc~lv4. Mortimer, K. V., and Tranter, T. C.: A Preliminary carboxylate Cements, Br. Dent. J. 127: 365-370, 1969. 5. Mizrahi, E., and Smith, D. C.: Direct Cementation of Orthodontic Brackets to Dental Enamel, Br. Dent. J. 127: 371-375, 1969. 6. Phillips, R. W., Swartz, M. L., and Rhodes, B.: An Evaluation of a Carboxylate Adhesive Cement, J. Am. Dent. Assoc. 81: 1353-1359, 1970. 7. Stanley, H. R.: Design for a Human Pulp Study, Part I, Oral Surg. 25: 633-647, 1968. 8. Truelove, E. L., Mitchell, D. F., and Phillips, R. W.: Biologic Evaluation of a Carboxylatc Cement, J. Dent. Res. 50: 166, 1971. 9. Klotzer, W. T., Dowden, W. E., and Lang-eland, K.: Paper No. 795, 48th General Meeting I. A. D. R., New York, 1970. UNIVERSITY OF CALIFORNIA, SAN FRANCXSCO SCHOOL OF DENTISTRY SAN FRANCISCO, CALIF. 94122
Biologic
and
physical
polycarboxylate
properties
of a zinc
cement
M. D. Jendresen, D.D.S.,* and H. 0. Trowbridge, D.D.S., Ph.D.** School of Dentistry, University of California, San Francisco, Calif.
T
In the past four years, since the development and introduction of a new dental cement by D. C. Smith,’ there have been several reports dealing with this new product, generally referred to as polycarboxylate cementzs6 These reports have dealt mainly with the mechanical, physical, and chemical properties of the carboxylate cements, although some data have been published on the biologic properties for this cement using animal models.8~9 The purpose of this investigation was to characterize one of the recently developed and available carboxylate cements as to both its biologic and physical properties. A zinc polycarboxylate, manufactured by S. S. White Company and sold as PCA,t was chosen. Biologic properties were evaluated by studying responses of the human dental pulp. Physical properties were evaluated by conventional laboratory tests for compressive and tensile strength, solubility, film thickness, and setting time. METHOD-BIOLOGIC
PROPERTIES
A screening-type experimental design was established to evaluate the pulpal response induced by this zinc polycarboxylate cement and two different cements used as controls. A zinc oxide and eugenol cement was used as a standard to illustrate a mild pulpal response, and a zinc phosphate cement was used as an additional control to illustrate a moderate or severe pulpal response. These cements are identified in Table I. The selection and clinical requirements established for this part of the study were those outlined by Stanley.’ Standardized Class V cavity preparations were made on the facial surfaces in the Portions of this article tion for Dental Research, Palo Alto, Calif.
were presented at the annual meeting of the International AssociaChicago, Ill., and at the Pacific Coast Society of Prosthodontics,
*Associate Professor and Chairman, **Associate Professor of Pathology, +Polycarboxylate 264
cement.
Biomaterials Science. School of Dentistry and School of Medicine.
Properties of zinc polycarboxylate
cements
265
Table I. Cements Cement
Manufacturer
We
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate
2200 PCA
L. D. Caulk Company S. S. White Company
Flecks
M&y,
Inc.
Table II. Day 5 Material
Average
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate *Degrees
of pathologic
fR. D., remaining
response* 0.4 1.0 2.4
Average R.D.f (mm.1 0.76 0.75 0.62
response (0 to 4).
dentin
thickness.
cervical region of 45 intact human teeth not previously restored. A No, 3P pearshaped carbide bur was used at a speed of 300,000 r.p.m. with an air-water spray. Fifteen teeth were restored with each of the cements. No cavity liners, varnishes, or pulp protective measures were used in any instance. All restorative procedures were conducted with the aid of a rubber dam to better control the operating site. Four patients were involved, and each patient had nearly equal numbers of test and control restorations placed. The patients were men 35 to 45 years of age who were scheduled for full mouth extractions due to pending prosthodontic treatment. At postoperative intervals of 5, 21, and 90 days, 5 teeth were extracted for each of the three cement types placed. This provided 5 teeth for each category (both experimental and control) and for each time interval. Test and control teeth in the same patient were extracted at the same sitting. Immediately following extraction, the teeth were placed in paraformaldehyde solution (4.0 per cent) and decalcified and processed for histopathologic interpretation. The various cements and time intervals were compared by recording the incidence and average intensities of pulpal response through loss of odontoblasts and the inflammatory response in the superficial tissues (odontoblastic layer) and the deeper tissues of the pulp. The intensity of this pulpal response was recorded according to an arbitrary scale (0 to 4) . RESULTCBIOLOGIC
PROPERTIES
The results for the three cements at 5 days postoperatively are shown in Table If. The specimens restored with zinc oxide and eugenol had a minimal response followed closely by the zinc polycarboxylate, which elicited a mild response in contrast to the zinc phosphate material, which produced a measurably stronger or moderate response. In each category, the average remaining dentin thickness (R.D.) was smaller than 1.0 mm. The results at the 21 day interval showed greater differentiation between the cements compared. Table III illustrates the average response for zinc phosphate cement as 4, which is considered severe and indicates abscess formation; whereas,
266
Jendresen
J. Prosthet. Dent. September, 1972
and Trowbridge
21 days after placement of zinc phosphate cement. The Iremalining Fig. 1. Abscess formation rating is 4 on a 0 to 4 scale dent in thickness is 0.25 mm., and the pathology
Tab de III. Day 21 Material
Average response*
Average R.D.T (mm.)
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate
0.4 1.4 4.0
0.35 0.49 0.32
*Degrees
of pathologic
tR. D., remaining
response (0 to 4).
dentin thickness.
the other two cements showed little change from the previous time interval. Again, note the remaining dentin thickness. Fig. 1 shows a specimen restored with zinc phosphate cement at the 21 day interval. The R.D. is 0.25 mm., and the pathology rating is 4. The abscess formation is well defined. Fig. 2 is a specimen containing zinc polycarboxyIate at the same time and magnification with an R.D. of 0.20 mm. which produced a pulpal response noted as 1.
Properties
of zin(.
polycarhorylate
Fig. 2. Pulpal response to zinc polycarboxylate at 21 days. The rtmainirq 0.2 mm. The tissue response, considered minimal, was rated a, 1.
c‘emrnf,i
dentin
thickness
lab de IV. Day 90 Material
of pathologic
jR. D.. remaining
I-
-.. Acerage
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate *Degrees
267
response* 0.0 0.3 4.0
I /
,4r’erage R.D.t (mm.) 0.44 o.i5 0.44
response (0 to 4)
dentin thickness,
Ninety-day data indicate a reduction in average intensity scores for the zinc polpcarboxylate and a continued high intensity of response for the zinc phosphate cwnent. These data are shown in Table IV. It is not unusual that any restorative material registers a higher reaction w intensity score than zinc oxide and eugenol. Although the other materials, when used, may initially produce a higher average response than the zinc oxide and eugenol con-
268
Jendresen
Fig. 3. Localized phosphate
cement.
and Trowbridge
J. Prosthet. Dent. September,
1972
chronic inflammatory cells shown at 90 days following placement of zinc The remaining dentin thickness is 0.7 mm. The tissue response was 4.
trol, their average intensity scores should decrease significantly in the longer postoperative intervals in order to be considered as eliciting a favorable response. This favorable situation is seen for the zinc polycarboxylate and is not seen for the more irritating zinc phosphate cement. An example is shown in Fig. 3: zinc phosphate cement at 90 days with an R.D. of 0.7 mm., an abscess formation, and a rating of 4. A contrast is seen in Fig. 4: the zinc polycarboxylate at 90 days with an R.D. of 0.6 mm. and a pulpal response of 0. Table V shows the average responses in each category for the total sample. This illustrates the trend of pulpal response for the various cements. The average responses for zinc oxide and eugenol and zinc polycarboxylate cements are mild throughout the test period, but the pulp responses to the zinc phosphate cement go from moderate to severe. PHYSICAL
PROPERTIES
To further characterize this zinc polycarboxylate, selected physical properties were evaluated in the conventional manner. Table VI illustrates the results for tests of film
ProperGs
of
zinc polycarboxylate
ceme7zt.r
cement at 90 days. The remaining Fig. 4. Pulpal response to zinc polycarboxylate ness is 0.6 mm., and the pulpal response was graded as I),
dentin
269
thick-
thickness, solubility, and setting tiine obtained as prescribed in the A.D.A. Specification NO. 8 for zinc phosphate cement. Working-time data were obtained from a subjective test that indicated a time when the cement became stringy and less desirable to handle from a clinical viewpoint. In all tests, the powder/liquid ratio was 1.5;‘1 .O by weight. Compressive strength data were obtained on cylindrical specimens 6 by 12 mm. according to A.D.A. Specification No. 8. The diametral tensile strength values were determined from specimens of the sarne dimensions using the Instron universal testing machine at a loading rate of 0.02 inch per minute. The adhesion properties for this zinc polycarboxylatr were drtermined for metalto-metal adhesion and for metal-to-tooth enamel adhesion. The metal-to-metal specimens were orthodontic lingual buttons of stainless steel. The surfaces were sandblasted and cemented together. Prior to the actual adhesion test, the specimens were stored in water at 37’ C. for 3 hours. The adhesion test-frame apparatus consisted of keyed aluminum clamps affixed to the top of the crosshead of an Instron machine in such a manner as to permit eas:
270
Jendresen
J. Prosthet. Dent. September, 1972
and Trowbridge
Table V. Summary
of average responses
Cement
Day 5
I
Zinc oxide and eugenol Zinc polycarboxylate Zinc phosphate
I
0.4 1.0 2.4
Day 21
I
0.4 1.4 4.0
Day 90 0.0 0.5 4.0
Table VI. Zinc polycarboxylate Powder/liquid Film thickness Solubility Setting time Working time* *Subjective
1.5/1.0 22 p 0.1 per cent 7% minutes 2 minutes
test.
Table VII. Zinc polycarboxylate Age (hours)
p.s.i.
SD*
nt
Compressive
24
8900
500
30
Tensile
24
700
160
30
3 3
1300 800
260 195
15 58
Strength
(diametral)
Adhesive (tensile) Metal to metal Metal to tooth enamel *SD, Standard tn, number
deviation.
of specimens tested.
centering of the test button under the lifting hook suspended from the tensile load cell. The lifting hook was connected to the load cell through a short length of flexible steel chain in order to compensate for minor variations in orientation. This provided that the applied force was as close to being purely tensile as possible. A loading rate of 0.02 inch per minute was used for the adhesion tests. The metal-to-tooth enamel specimens were tested in a similar fashion with the same mechanical arrangement. Extracted human teeth were used. They were mounted in dental stone with the labial surfaces positioned on a plane with the top surface of the mounting ring and stone. The specimens were kept wet until testing. The surfaces of the test teeth were prepared by polishing with a pumice-water slurry solution using a dental handpiece at slow speed. Specimens were rinsed with water, and this was followed by a scrubbing with an alcohol-soaked cotton swab. The cleaned surfaces dried through evaporation as the cement mix was made. Again, stainless steel orthodontic lingual buttons were used. These were cemented and positioned so as to fit in the previously described adhesion test-frame apparatus. Care was taken during cementation to achieve a uniform film thickness. The specimens were stored in water at 37’ C. for 3 hours before testing. The results for these tests are shown in Table VII.
Properties
of zinc
polycarboxylate
cement.c
271
From the data presented in this report on selected biologic and physical propertirs of a zinc polycarboxylate cement, it appears that this cement is well tolerated by the human pulp tissue and has good physical properties. References 1. Smith, D. C.: A New Dental Cement, Br. Dent. J. 125: 381-384, 1968. 2. Mizrahi, E., and Smith, D. C.: The Bond Strength of a Zinc Polycarboxylate Cement, Hr. Dent. J. 127: 410-414, 1969. 3. Friend, L. A.: Handling Properties of a Zinc Polycarboxylate Cement, Br. Dent. J. 127: 3.59-364, 1969. Laboratory Evaluation of Pc~lv4. Mortimer, K. V., and Tranter, T. C.: A Preliminary carboxylate Cements, Br. Dent. J. 127: 365-370, 1969. 5. Mizrahi, E., and Smith, D. C.: Direct Cementation of Orthodontic Brackets to Dental Enamel, Br. Dent. J. 127: 371-375, 1969. 6. Phillips, R. W., Swartz, M. L., and Rhodes, B.: An Evaluation of a Carboxylate Adhesive Cement, J. Am. Dent. Assoc. 81: 1353-1359, 1970. 7. Stanley, H. R.: Design for a Human Pulp Study, Part I, Oral Surg. 25: 633-647, 1968. 8. Truelove, E. L., Mitchell, D. F., and Phillips, R. W.: Biologic Evaluation of a Carboxylatc Cement, J. Dent. Res. 50: 166, 1971. 9. Klotzer, W. T., Dowden, W. E., and Lang-eland, K.: Paper No. 795, 48th General Meeting I. A. D. R., New York, 1970. UNIVERSITY OF CALIFORNIA, SAN FRANCXSCO SCHOOL OF DENTISTRY SAN FRANCISCO, CALIF. 94122