0099-2399/90/1603-0116/$02.00/0 JOURNAL OF I~NOODONTICS Copyright 9 1990 by The American Association of Endodontists
Printed in U.S.A. VOL. 16, No. 3, MARCH 1990
Microleakage of Intermediate Restorative Materials Kian Chong Lim, BDS, MSc, AM
This study compares the microleakage of a glass ionomer cement, Ketac Fil, used without cavity conditioning, with the established intermediate restorative materials, Cavit-W, and a reinforced zinc oxide-eugenol cement, Kalzinol. Microleakage was assessed using an electrochemical technique. At the end of 30 days, the materials tested, listed in decreasing order of microleakage, were Cavit-W, Ketac Fil inserted without cavity conditioning, Kalzinol, and the control group of Ketac Fil inserted into conditioned cavities. There was no significant difference in the microleakage observed in Ketac Fil restorations inserted without cavity conditioning and Kalzinol (p = 0.450), while the differences between the other groups were highly significant (p < 0.001).
Glass ionomer cements on the other hand can adhere to tooth structure, satisfy the requirements of esthetics, and are reasonably durable for restoring occlusal surfaces as an interim measure. The good sealing ability of glass ionomer has been established (14), but this requires careful conditioning or cleaning of the cavity to remove the smear layer. When used as an intermediate restoration, the practitioner may want to eliminate cavity conditioning for expedience. This study was designed to evaluate the effect of eliminating cavity conditioning on the microleakage of a glass ionomer cement restoration and to compare this result with the microleakage of two established intermediate restorative materials, Cavit and a zinc oxide-eugenol cement, over a period of 30 days. MATERIALS AND METHODS Unrestored, extracted human molars with fused roots stored in 10% formalin saline were used. Coronal access to the pulp chamber was created and the apical half of the fused root removed. The pulp chamber was cleaned ultrasonically for 1 h with the teeth immersed in a 1% sodium hypochlorite solution. Ultrasonic cleaning removes the smear layer (15) which improves the contact between the restorative material and the cavity wall to reduce microleakage. Therefore, the access cavities were enlarged to approximately 2.5 m m in diameter to recreate the smear layer which would be present clinically. The teeth were then stored in tap water before filling. The coronal access of 10 teeth per group were filled as follows: Glass ionomer: Ketac Fil (Fabrick Pharmazeutischer), a capsulated glass ionomer cement, was agitated in an amalgamator for 10 sec at 4000 rpm. The material was syringed directly into the cavity, then a plastic #6 instrument was used to pack the cavity and remove excess filling material The restoration was then coated with two layers o f ESPE varnish (Fabrick Pharmazeutischer). In the control group for Ketac Fil, designated Ketac FiI(C), the cavities were conditioned with polyacrylic acid (G-C Dental Industrial Corp., Tokyo, Japan) for 10 sec, washed and dried, then filled with Ketac Fil as described above. Zinc oxide-eugenol cement: Cavities were filled with a reinforced zinc oxide-eugenol cement, Kalzinol (DeTrey, Weybridge, England) mixed to the consistency commonly used for intermediate restorations. Cavit: Cavities were filled with Cavit-W. The positive control was filled with gutta-percha while the negative control did not have an occlusal cavity prepared. All of the materials were inserted into the occlusal cavity to a depth of 3.5 mm. This depth of filling was used as 3.5
Root canal treatment, pulp capping, or indirect pulp capping may require multiple visits, therefore it is important that the cavity is properly sealed between appointments to prevent contamination. Zinc oxide-eugenol cements and Cavit (Fabrik Pharmazeutischer, Seefeld Oberbay, Federal Republic of Germany) are probably the most widely used intermediate restorations. Cavit is a single paste system which is easy and convenient to use and is available as Cavit, Cavit-W, and Cavit-G. The difference between them, according to the manufacturer is their hardness, which is greatest with Cavit and least with Cavit-G. Cavit absorbs water and expands to seal the cavity as it sets (1). Cavit provides a seal that has been generally shown to be good (2-5), and compared with zinc oxideeugenol cements, its seal has proven to be as effective (6, 7) or even better (8-10). A few studies, however, found that Cavit restorations leaked badly (11- ! 3). Microleakage studies of zinc oxide-eugenol cements generally demonstrate some leakage (6, 8-10). Zinc oxide-eugenol cement and Cavit have relatively low compressive strengths and do not adhere to tooth structure. This makes both materials unsuitable for use where insufficient coronal tooth structure remains to provide mechanical retention, or when esthetics is an important consideration because of its poor color. In addition, Cavit requires water sorption to set; this property has been noted to cause hypersensitivity in vital teeth, although spatulating Cavit with a drop of water or inserting it into cavities moistened with water or eugenol overcomes this problem (1).
116
Microleakage Comparison
Vol. 16, No. 3, March 1990
m m of Cavit is necessary to prevent microleakage (3). A specially made silicone-coated #6 steel fiat fissure bur was inserted from the apical access cavity and positioned with the aid of a W H O design periodontal probe to indicate an occlusal cavity depth of 3.5 ram. The platform was removed after the filling set. The teeth were then placed in a shallow container of water, occlusal surface downward, and left for 1 h in a humidor to simulate the wet oral environment before evaluation of microleakage using an electrochemical technique (16). The bared end of an insulated copper wire of 1 m m in diameter was inserted through the apical access cavity to contact the restoration and it was secured in place with wax. The external surface o f the tooth was coated with a layer of silicone sealant (Silicone RIV; Expandite Ltd., Petone, New Zealand), leaving the restoration exposed. The teeth were immersed in a 1% potassium chloride solution at 370C, along with a stainless steel tape which acted as a cathode. At daily intervals, a stabilized 10-V potential difference was applied across the central cathode and the individual anode projecting from each tooth. The current across an external 100 K-ohm resistor was recorded over 30 days. The leakage currents for each group were analyzed for any differences using multivariate regression and analysis of variance (17).
117
TABLE 1. Means and standard deviations of leakage currents Cavit
Kalzinol
Ketac Fil (C) (control)
Ketac Fil
Day Mean*
SD
Mean*
SD
Mean*
SD
Mean*
SD
0 17 31 43 56 80 108 125 136 167 203 298 318 325 357 362 401 444 449 448 461 480 567 586 660 660 662 655 675 637
1 28 44 70 73 89 116 136 137 187 250 441 483 469 522 512 550 579 567 561 563 592 608 591 557 552 548 537 543 527
4 29 37 39 43 49 58 69 74 83 87 93 102 101 108 113 116 122 133 130 139 136 144 143 148 145 160 150 161 151
7 26 33 37 40 43 50 57 61 76 84 75 85 84 93 91 104 99 106 100 114 110 118 114 114 107 120 108 124 108
40 38 49 45 48 60 69 81 98 102 107 107 113 t18 123 125 130 130 129 132 133 134 136 139 142 145 148 148 157 160
29 33 41 34 32 38 38 42 33 34 31 28 35 38 37 40 35 42 40 41 43 44 42 42 43 54 48 49 64 63
13 16 17 15 15 18 17 17 21 19 14 14 15 24 24 23 23 21 22 20 23 22 24 26 27 27 34 31 32 31
11 12 5 7 11 17 12 11 16 20 12 10 9 22 22 20 12 11 14 11 12 16 19 21 24 27 37 38 37 33
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
RESULTS The mean leakage currents and their standard deviations are shown in Table I. These were transformed to stabilize the variance before statistical analyses (17) and the graph of the mean transformed leakage current with time for each group is shown in Fig. 1, with the results of regression analyses shown in Table 2. The ranking in increasing order of microleakage at the end of 30 days is shown in Table 3.
* Mean current for 10 teeth per group in microamperes.
DISCUSSION 9 , o ,
8
When glass ionomer cement is used as an intermediate restoration, the practitioner may want to omit cavity conditioning to expedite its placement. Omitting cavity conditioning prior to placement of Ketac Fil restorations resulted in significantly greater microleakage compared with restorations in conditioned cavities; however, it was not significantly different from the moderate amount of leakage observed for Kalzinol. As the microleakage of Ketac Fil in unconditioned cavities was no worse than the established material Kalzinol, it may be potentially acceptable as an intermediate restoration. However, it cannot be assumed that it will be equally effective as Kalzinol based on microleakage alone. Kalzinol and other zinc oxide-eugenol cements are rarely associated with pulpal inflammation (18) probably because the bactericidal action of eugenol prevents or inhibits bacterial colonization at the tooth-restoration interface. Glass ionomer cements have not been evaluated in this respect as thoroughly as zinc oxide-eugenol cements. According to Plant et al. (19), different proprietary glass ionomer cements vary in their ability to prevent bacteria from colonizing at the tooth-restoration interface, and only some approach the effectiveness of zinc oxide-eugenol cement. This study has evaluated the possible use of glass ionomer cement without cavity condi-
7
CAVIT KALZINOL KE'IAC FIL(C) KETAC FII.
~ ~ o_ . ~ ,
~ 9 9 9 9 9
9 9
6 6 9 435
2
~
9
~ e
o , ...~ " ~ ~ ~
o
" " " " "
~ *
1 '~ ' 4
' 6 " 8 "1(} " 12 ' 1 4
' 16 " 18 " 2 0 '
2 ' 2 ' 2'4" 2'6" 2"8" 3"0
DAYS
FIG 1. Graph of transformed mean leakage currents with time.
tioning, but further studies need to be conducted before recommending its use in this manner. Until such information is available, it will be prudent to condition the cavity wails before using glass ionomer cement. Ketac Fil is admittedly a relatively expensive material for use as an intermediate restoration. It was used in this study as a convenient means of attaining standard powder to liquid
118
Journal of Endodontics
Lim TABLE 2. Results of linear regression analysis
Cavit Kalzinol Ketac Fil Ketac Fil (C) (control) 9Constantsfor the equetiony
a*
b*
Correlation Coefficient
Variance Ratio
P
2.0258 2.7449 3.4696 2.1187
0.2233 0.0948 0.0735 0.0183
0.6015 0.5574 0.6710 0.1426
168.8943 134.2999 244.1020 6.1829
Printed in U.S.A. VOL. 16, No. 3, MARCH 1990
Microleakage of Intermediate Restorative Materials Kian Chong Lim, BDS, MSc, AM
This study compares the microleakage of a glass ionomer cement, Ketac Fil, used without cavity conditioning, with the established intermediate restorative materials, Cavit-W, and a reinforced zinc oxide-eugenol cement, Kalzinol. Microleakage was assessed using an electrochemical technique. At the end of 30 days, the materials tested, listed in decreasing order of microleakage, were Cavit-W, Ketac Fil inserted without cavity conditioning, Kalzinol, and the control group of Ketac Fil inserted into conditioned cavities. There was no significant difference in the microleakage observed in Ketac Fil restorations inserted without cavity conditioning and Kalzinol (p = 0.450), while the differences between the other groups were highly significant (p < 0.001).
Glass ionomer cements on the other hand can adhere to tooth structure, satisfy the requirements of esthetics, and are reasonably durable for restoring occlusal surfaces as an interim measure. The good sealing ability of glass ionomer has been established (14), but this requires careful conditioning or cleaning of the cavity to remove the smear layer. When used as an intermediate restoration, the practitioner may want to eliminate cavity conditioning for expedience. This study was designed to evaluate the effect of eliminating cavity conditioning on the microleakage of a glass ionomer cement restoration and to compare this result with the microleakage of two established intermediate restorative materials, Cavit and a zinc oxide-eugenol cement, over a period of 30 days. MATERIALS AND METHODS Unrestored, extracted human molars with fused roots stored in 10% formalin saline were used. Coronal access to the pulp chamber was created and the apical half of the fused root removed. The pulp chamber was cleaned ultrasonically for 1 h with the teeth immersed in a 1% sodium hypochlorite solution. Ultrasonic cleaning removes the smear layer (15) which improves the contact between the restorative material and the cavity wall to reduce microleakage. Therefore, the access cavities were enlarged to approximately 2.5 m m in diameter to recreate the smear layer which would be present clinically. The teeth were then stored in tap water before filling. The coronal access of 10 teeth per group were filled as follows: Glass ionomer: Ketac Fil (Fabrick Pharmazeutischer), a capsulated glass ionomer cement, was agitated in an amalgamator for 10 sec at 4000 rpm. The material was syringed directly into the cavity, then a plastic #6 instrument was used to pack the cavity and remove excess filling material The restoration was then coated with two layers o f ESPE varnish (Fabrick Pharmazeutischer). In the control group for Ketac Fil, designated Ketac FiI(C), the cavities were conditioned with polyacrylic acid (G-C Dental Industrial Corp., Tokyo, Japan) for 10 sec, washed and dried, then filled with Ketac Fil as described above. Zinc oxide-eugenol cement: Cavities were filled with a reinforced zinc oxide-eugenol cement, Kalzinol (DeTrey, Weybridge, England) mixed to the consistency commonly used for intermediate restorations. Cavit: Cavities were filled with Cavit-W. The positive control was filled with gutta-percha while the negative control did not have an occlusal cavity prepared. All of the materials were inserted into the occlusal cavity to a depth of 3.5 mm. This depth of filling was used as 3.5
Root canal treatment, pulp capping, or indirect pulp capping may require multiple visits, therefore it is important that the cavity is properly sealed between appointments to prevent contamination. Zinc oxide-eugenol cements and Cavit (Fabrik Pharmazeutischer, Seefeld Oberbay, Federal Republic of Germany) are probably the most widely used intermediate restorations. Cavit is a single paste system which is easy and convenient to use and is available as Cavit, Cavit-W, and Cavit-G. The difference between them, according to the manufacturer is their hardness, which is greatest with Cavit and least with Cavit-G. Cavit absorbs water and expands to seal the cavity as it sets (1). Cavit provides a seal that has been generally shown to be good (2-5), and compared with zinc oxideeugenol cements, its seal has proven to be as effective (6, 7) or even better (8-10). A few studies, however, found that Cavit restorations leaked badly (11- ! 3). Microleakage studies of zinc oxide-eugenol cements generally demonstrate some leakage (6, 8-10). Zinc oxide-eugenol cement and Cavit have relatively low compressive strengths and do not adhere to tooth structure. This makes both materials unsuitable for use where insufficient coronal tooth structure remains to provide mechanical retention, or when esthetics is an important consideration because of its poor color. In addition, Cavit requires water sorption to set; this property has been noted to cause hypersensitivity in vital teeth, although spatulating Cavit with a drop of water or inserting it into cavities moistened with water or eugenol overcomes this problem (1).
116
Microleakage Comparison
Vol. 16, No. 3, March 1990
m m of Cavit is necessary to prevent microleakage (3). A specially made silicone-coated #6 steel fiat fissure bur was inserted from the apical access cavity and positioned with the aid of a W H O design periodontal probe to indicate an occlusal cavity depth of 3.5 ram. The platform was removed after the filling set. The teeth were then placed in a shallow container of water, occlusal surface downward, and left for 1 h in a humidor to simulate the wet oral environment before evaluation of microleakage using an electrochemical technique (16). The bared end of an insulated copper wire of 1 m m in diameter was inserted through the apical access cavity to contact the restoration and it was secured in place with wax. The external surface o f the tooth was coated with a layer of silicone sealant (Silicone RIV; Expandite Ltd., Petone, New Zealand), leaving the restoration exposed. The teeth were immersed in a 1% potassium chloride solution at 370C, along with a stainless steel tape which acted as a cathode. At daily intervals, a stabilized 10-V potential difference was applied across the central cathode and the individual anode projecting from each tooth. The current across an external 100 K-ohm resistor was recorded over 30 days. The leakage currents for each group were analyzed for any differences using multivariate regression and analysis of variance (17).
117
TABLE 1. Means and standard deviations of leakage currents Cavit
Kalzinol
Ketac Fil (C) (control)
Ketac Fil
Day Mean*
SD
Mean*
SD
Mean*
SD
Mean*
SD
0 17 31 43 56 80 108 125 136 167 203 298 318 325 357 362 401 444 449 448 461 480 567 586 660 660 662 655 675 637
1 28 44 70 73 89 116 136 137 187 250 441 483 469 522 512 550 579 567 561 563 592 608 591 557 552 548 537 543 527
4 29 37 39 43 49 58 69 74 83 87 93 102 101 108 113 116 122 133 130 139 136 144 143 148 145 160 150 161 151
7 26 33 37 40 43 50 57 61 76 84 75 85 84 93 91 104 99 106 100 114 110 118 114 114 107 120 108 124 108
40 38 49 45 48 60 69 81 98 102 107 107 113 t18 123 125 130 130 129 132 133 134 136 139 142 145 148 148 157 160
29 33 41 34 32 38 38 42 33 34 31 28 35 38 37 40 35 42 40 41 43 44 42 42 43 54 48 49 64 63
13 16 17 15 15 18 17 17 21 19 14 14 15 24 24 23 23 21 22 20 23 22 24 26 27 27 34 31 32 31
11 12 5 7 11 17 12 11 16 20 12 10 9 22 22 20 12 11 14 11 12 16 19 21 24 27 37 38 37 33
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
RESULTS The mean leakage currents and their standard deviations are shown in Table I. These were transformed to stabilize the variance before statistical analyses (17) and the graph of the mean transformed leakage current with time for each group is shown in Fig. 1, with the results of regression analyses shown in Table 2. The ranking in increasing order of microleakage at the end of 30 days is shown in Table 3.
* Mean current for 10 teeth per group in microamperes.
DISCUSSION 9 , o ,
8
When glass ionomer cement is used as an intermediate restoration, the practitioner may want to omit cavity conditioning to expedite its placement. Omitting cavity conditioning prior to placement of Ketac Fil restorations resulted in significantly greater microleakage compared with restorations in conditioned cavities; however, it was not significantly different from the moderate amount of leakage observed for Kalzinol. As the microleakage of Ketac Fil in unconditioned cavities was no worse than the established material Kalzinol, it may be potentially acceptable as an intermediate restoration. However, it cannot be assumed that it will be equally effective as Kalzinol based on microleakage alone. Kalzinol and other zinc oxide-eugenol cements are rarely associated with pulpal inflammation (18) probably because the bactericidal action of eugenol prevents or inhibits bacterial colonization at the tooth-restoration interface. Glass ionomer cements have not been evaluated in this respect as thoroughly as zinc oxide-eugenol cements. According to Plant et al. (19), different proprietary glass ionomer cements vary in their ability to prevent bacteria from colonizing at the tooth-restoration interface, and only some approach the effectiveness of zinc oxide-eugenol cement. This study has evaluated the possible use of glass ionomer cement without cavity condi-
7
CAVIT KALZINOL KE'IAC FIL(C) KETAC FII.
~ ~ o_ . ~ ,
~ 9 9 9 9 9
9 9
6 6 9 435
2
~
9
~ e
o , ...~ " ~ ~ ~
o
" " " " "
~ *
1 '~ ' 4
' 6 " 8 "1(} " 12 ' 1 4
' 16 " 18 " 2 0 '
2 ' 2 ' 2'4" 2'6" 2"8" 3"0
DAYS
FIG 1. Graph of transformed mean leakage currents with time.
tioning, but further studies need to be conducted before recommending its use in this manner. Until such information is available, it will be prudent to condition the cavity wails before using glass ionomer cement. Ketac Fil is admittedly a relatively expensive material for use as an intermediate restoration. It was used in this study as a convenient means of attaining standard powder to liquid
118
Journal of Endodontics
Lim TABLE 2. Results of linear regression analysis
Cavit Kalzinol Ketac Fil Ketac Fil (C) (control) 9Constantsfor the equetiony
a*
b*
Correlation Coefficient
Variance Ratio
P
2.0258 2.7449 3.4696 2.1187
0.2233 0.0948 0.0735 0.0183
0.6015 0.5574 0.6710 0.1426
168.8943 134.2999 244.1020 6.1829
