0099-2399/92/1808-0363/$03.00/0 JOURNAL OF ENDODONTICS Copyright © 1992 by The American Association of Endodontists
Printed in U.S.A.
VOL. 18, NO. 8, AUGUST1992
SCIENTIFIC ARTICLES Effect of Different Sealers on Thermoplasticized Gutta-percha Root Canal Obturations Bamiduro R. Oguntebi, DDS, MS, and Chiayi Shen, PhD
The objective of this study was to test the hypothesis that the apical seal provided by thermoplasticized root canal obturations depends on the film thickness of the sealer used. The root canals of 120 maxillary cuspid teeth were instrumented and divided into six equal groups of 20 teeth. A thermoplasticized gutta-percha root canal obturator was used to make an impression of the lubricated canal and coated with a sealer cement before reseating. Five different sealer cements of known film thickness were studied. They were, in the decreasing order of film thickness, Roth's Type I Cement, Sealapex, Lee Endofil, AH26, and Ketac-Cem. The control group that received no sealer was prepared as recommended by the manufacturer. The degree of microleakage was based on the depth of dye penetration from the apical end measured by two independent examiners. The data collected were analyzed by analysis of variance and Weibull distribution. Analysis of vadance shows that the control group exhibited significantly higher dye penetration depth (p < 0.05) while there were no significant differences among the other five groups. Analysis by Weibull distribution function shows that Lee Endofil and AH26 exhibited a higher percentage of lower linear dye penetration values compared with other groups.
percha cones and to fill accessory canals (3). Several different types of sealers have been tested for their ability to produce an adequate seal, and satisfactory results have been reported for AH26 sealer and Procosol cement (5), zinc oxide-eugenolbased sealers (6), and calcium hydroxide-based sealers (7). These studies, however, have shown that these sealers permit some degree of microleakage and the extent of microleakage that can be tolerated while maintaining successful therapy has not been established. Therefore, the search for a root canal sealer that is nonirritating and produces a bacteria-tight seal has led to the in vitro testing of adhesive materials such as polycarboxylate cements (8), cyanoacrylates (9), glass ionomer cements (10), and dentin-bonding agents (11). Varying degrees of success have been reported but clinical evaluation of some of these sealers has shown them to be unsuitable because of difficulty with clinical manipulation (12). Several techniques of obturating root canals with guttapercha and root canal sealers have been described, and techniques that utilize thermoplasticized gutta-percha have become widely used in the past decade (13). Most investigations have suggested that these thermoplasticized gutta-percha obturation techniques are more successful if a sealer is used (3, 14). The requirements of the ideal root canal sealer have been enumerated (15) and a lot of investigations have examined the ability of different sealers to meet one of those requirements--the ability to render a hermetic seal (16). This property has been shown to be related to a variety of physical characteristics such as flow, solubility, setting time, compressive strength, radiopacity, and adhesive properties (16). One study showed that there is a significant relationship between the film thickness and seating restriction of standardized gutta-percha points (17). This restriction in seating may prevent complete reinsertion of the gutta-percha obturator point to its pre-fit position, causing a greater degree of microleakage. The recent reintroduction of similar techniques (18) has reemphasized the need to reexamine the influence of film thickness on the seal produced in these root canal fillings. The objective of this study was to test the hypothesis that the apical seal of root canals obturated with a thermoplasticized gutta-percha technique can be influenced by the film thickness of the root canal sealer used.
Successful root canal therapy requires a complete obturation of the root canal system with nonirritating biomaterials. Previous investigations have shown that incomplete canal obturation is one of the major causes of endodontic failure (1, 2). The currently accepted method of obturation of prepared root canals employs a solid or semi-solid core, such as gutta-percha, and a root canal sealer (3). Gutta-percha has been shown to have no adhesive qualities to dentin regardless of the obturation technique used (4). Therefore, sealers are used as a binding agent and as a lubricant to aid in seating the gutta-
363
364
Oguntebi and Shen
MATERIALS AND METHODS
Journal of Endodontics TABLE 1. List of sealers used along with respective film
thickness
One hundred twenty extracted cuspid teeth without canal calcification, fractures, or apical curvatures greater than 20 degrees were selected from a large collection that had been stored in glycerin. The crowns of the teeth were resected near the cementoenamel junction with a lathe to obtain a uniform root length of 15 mm. A working length was determined radiographically 1 mm short of the root apex and the canals were prepared to an apical size of #40 using K files and copious irrigation with 5.25% sodium hypochlorite. The coronal 4-mm portion of the canal was flared using #40 Hedstrom files, after which the canal walls were smoothed circumferentially with #40 K files. The canals were copiously irrigated with 17% EDTA solution first and then 5.25% sodium hypochlorite solution, dried with paper points, and stored in deionized water for 2 wk before obturation in an attempt to achieve some rehydration of the dentin. The prepared teeth were then randomly divided into six groups of 20 teeth each and coded to ensure anonymity. Thermafil (Tulsa Dental Products, Tulsa, Oklahoma) was selected as the thermoplasticized gutta-percha obturation technique in this study because of its simplicity and the possibility of achieving some degree of standardization. The five root canal sealers (Table l) selected for this study included representatives of sealers currently used in endodontic practice and cements that have been advocated for clinical use which appears to be compatible with the selected thermoplasticized gutta-percha obturation technique. The film thickness of these selected root canal sealers was measured using a modification of the American Dental Association Specification No. 8. Briefly, approximately 0.1 ml of freshly mixed cement was placed between two glass plates and then subjected to a 15-kg dead weight until set. The increase in the combined thickness of the assembly compared with the thickness of the two glass plates only was determined as the film thickness of the sealer. The mean value of triplicate measurements is also shown in Table 1. The obturation technique suggested by the Thermafil manufacturer was utilized for the control group, which received no sealer. The Thermafil device was warmed as recommended by the manufacturer and immediately inserted into the canal, which was taken out of the water storage and dried with paper points. To assure uniform distribution of the sealer around the gutta-percha core which had to be warmed for application, a slight modification of the obturation technique was utilized for the teeth in the experimental groups. Following application of a water-soluble lubricant (Separatin; Brophy, Orange, CA) on the canal walls, the Thermafil devices were warmed as recommended by the manufacturer and immediately inserted into the canals to make an impression of the canal space. The devices were left for 5 min to cool to room temperature and then removed after placing a marker on the device and tooth to ensure reseating in proper alignment. The canal walls and the Thermafil impression were irrigated thoroughly with 5.25% sodium hypochlorite to remove the lubricant. The canal was dried with paper points and coated with freshly mixed root canal sealer with a K file. The Thermafil impression was allowed to air dry, coated with the sealer by rolling it in the same sealer mixture, and then reseated into the canal. Each tooth, after completion of obturation, was
Root Canal Sealer
Type
Film Thickness (um)
Roth's 801 Sealapex Ketac-Cem AH26 Lee EndofU Controls (no sealer)
Zinc oxide-eugenol Calcium hydroxide base Glass ionomer cement Epoxy resin base Condensation silicone None
35.0 38.1 25.8 35.6 12.7 NA*
° NA, not applicable.
TABLE 2. Average depth of dye penetration measured by two examiners
No.
Examiner I
Examiner2
(mm)
(mm)
Controls
18
Sealapex Ketac-Cem Roth's 801 AH26 Lee Endofil
13 17 20 18 16
6.79 __ 1.531 4.77 _+ 1.60,1 4.42 _+0.98 4.08 ___1.01 3.05 + 1.02 2.99 _+ 1.60
Sealer
6.59 + 1.55] 3.85___1.35 I 3.94 _+ 1.08 3.73 __0.99 3.20 + 1.12 2.74 __ 1.35
subjected to a 1-1bpressure in a humidor maintained at 370C for 24 h. The teeth were removed from the humidor, air dried for 12 h, coated with two layers of enamel paint on the surface of the cementum only, left to dry at room temperature for 2 h, and then returned to the humidor overnight. Both apical and coronal ends were not coated with any paint to facilitate the escape of air during subsequent immersion. The apical 1 mm of the teeth was resected using a new #557 fissure bur in a high-speed handpiece to expose the tooth/sealer/Thermafil interface. The obturated teeth were stored in 370C water for 4 wk. Each tooth was then individually suspended in a closed container with 2 mm of the apical end immersed in 0.5% aqueous methylene blue solution, and the incubator temperature was maintained at 37°C for 2 wk. The teeth were removed and split into two longitudinal halves through the apical foramen by cutting 2-mm deep labial and lingual grooves and fracturing the teeth using a hammer and a microtome knife. The degree of microleakage was determined by measurement of the linear extent of the methylene blue dye penetration from the apical end coronally into the root canal by two examiners using a Unitron microscope at a magnification of x400. A two-way analysis of variance was used to test the influence of the examiner and the types of sealers on the experimental data for all groups. The depth of dye penetration values was also analyzed by the following Weibull distribution function (19) to characterize the variation of the experimental data for each group by either examiner, Pc = 1 -
exp[(-L/Lo)']
(1)
where Pt is the percentage of specimens that exhibits the depth of dye penetration below the measured value designated, L, L,, is a normalizing parameter that has no physical significance, and m is the shape factor that delineates the extent of the data variation. The values of dye penetration depth were
Vol. 18, No. 8, August 1992
Sealer Film Thickness and Microleakage
365
TABLE 3. Results of Weibull analysis of the depth of penetration Examiner 1 Sealer
No.
Controls Sealapex Ketac-Cem Roth's 801 AH26 Lee Endofil
Examiner 2
Normalizing Parameter
7.60+0.65
18 13 17 20 18 16
5.46 4.79 4.82 3,47 3.45
2.11+0.511111
_+ 0.51 __+0.10 +__0.17 + 0.20 __+0.19
1.57 2.86 1.73 1.20 1.96
TABLE 4. Calculated percentage of the specimens with 2 mm or less of dye penetration by Weibull analysis Sealer
Examiner 1
Examiner 2
Controls Sealapex Ketac-Cem Roth's 801 AH26 Lee Endofil
5.8 18.7 7.9 19.6 40.3 29.1
4.1 27.4 11.3 26.0 37.0 44.7
Normalizing Parameter
m
i
2.s6+o.8411 [
6.93___0.60
_+ 0.32 ~ _____0.26 i ! __+0.18 _____ 0.16 _____ 0.40
I
m
4.41 4.07 4.24 3.57 3.t2
___0.46 + 0.13 __+0.35 __ 0.20 + 0.22
1.44 2.98 1.60 1.33 1.18
_+0.29 + [ __+0.29 __+0.14 __ 0.17
!
04 ji
10090807060.
/,,; /
e-
50.
..,"
o ,,
40-
,•"
1°,k ¢~
,•
/m
-
'
-
[] L
......
o
..........
•
30100-
o/{ 10- //,~7 e~/~'
209080-
o70-
~
1
l ,it , / ,4",, /o
60-
oj ~ "
•
o/;/_--,
50-
#_
•
/
.~L:~
0
, ,"
.......... _
_
,/i '11 •••"
2
i
i
i
i
i
4
6
8
10
12
Depth of Dye Penetration from the
o
C
14
Apex(mm)
F~G2. Experimental data and Weibull distribution of the depth of dye penetration measured by examiner 2.
40-
...... o: 20-
:
...d
20-
t
10
I,
~
~
;
i~___~..°.~.; -.
00
.'
.
.....
o
°
.
.
~
.........
•
J
i
J
i
J
2
4
6
10
12
14
Depth of Dye Penetration from the Apex (mm) F~G 1. Experimental data and Weibull distribution of the depth of dye penetration measured by examiner 1.
first sorted in ascending order, and a value (
Printed in U.S.A.
VOL. 18, NO. 8, AUGUST1992
SCIENTIFIC ARTICLES Effect of Different Sealers on Thermoplasticized Gutta-percha Root Canal Obturations Bamiduro R. Oguntebi, DDS, MS, and Chiayi Shen, PhD
The objective of this study was to test the hypothesis that the apical seal provided by thermoplasticized root canal obturations depends on the film thickness of the sealer used. The root canals of 120 maxillary cuspid teeth were instrumented and divided into six equal groups of 20 teeth. A thermoplasticized gutta-percha root canal obturator was used to make an impression of the lubricated canal and coated with a sealer cement before reseating. Five different sealer cements of known film thickness were studied. They were, in the decreasing order of film thickness, Roth's Type I Cement, Sealapex, Lee Endofil, AH26, and Ketac-Cem. The control group that received no sealer was prepared as recommended by the manufacturer. The degree of microleakage was based on the depth of dye penetration from the apical end measured by two independent examiners. The data collected were analyzed by analysis of variance and Weibull distribution. Analysis of vadance shows that the control group exhibited significantly higher dye penetration depth (p < 0.05) while there were no significant differences among the other five groups. Analysis by Weibull distribution function shows that Lee Endofil and AH26 exhibited a higher percentage of lower linear dye penetration values compared with other groups.
percha cones and to fill accessory canals (3). Several different types of sealers have been tested for their ability to produce an adequate seal, and satisfactory results have been reported for AH26 sealer and Procosol cement (5), zinc oxide-eugenolbased sealers (6), and calcium hydroxide-based sealers (7). These studies, however, have shown that these sealers permit some degree of microleakage and the extent of microleakage that can be tolerated while maintaining successful therapy has not been established. Therefore, the search for a root canal sealer that is nonirritating and produces a bacteria-tight seal has led to the in vitro testing of adhesive materials such as polycarboxylate cements (8), cyanoacrylates (9), glass ionomer cements (10), and dentin-bonding agents (11). Varying degrees of success have been reported but clinical evaluation of some of these sealers has shown them to be unsuitable because of difficulty with clinical manipulation (12). Several techniques of obturating root canals with guttapercha and root canal sealers have been described, and techniques that utilize thermoplasticized gutta-percha have become widely used in the past decade (13). Most investigations have suggested that these thermoplasticized gutta-percha obturation techniques are more successful if a sealer is used (3, 14). The requirements of the ideal root canal sealer have been enumerated (15) and a lot of investigations have examined the ability of different sealers to meet one of those requirements--the ability to render a hermetic seal (16). This property has been shown to be related to a variety of physical characteristics such as flow, solubility, setting time, compressive strength, radiopacity, and adhesive properties (16). One study showed that there is a significant relationship between the film thickness and seating restriction of standardized gutta-percha points (17). This restriction in seating may prevent complete reinsertion of the gutta-percha obturator point to its pre-fit position, causing a greater degree of microleakage. The recent reintroduction of similar techniques (18) has reemphasized the need to reexamine the influence of film thickness on the seal produced in these root canal fillings. The objective of this study was to test the hypothesis that the apical seal of root canals obturated with a thermoplasticized gutta-percha technique can be influenced by the film thickness of the root canal sealer used.
Successful root canal therapy requires a complete obturation of the root canal system with nonirritating biomaterials. Previous investigations have shown that incomplete canal obturation is one of the major causes of endodontic failure (1, 2). The currently accepted method of obturation of prepared root canals employs a solid or semi-solid core, such as gutta-percha, and a root canal sealer (3). Gutta-percha has been shown to have no adhesive qualities to dentin regardless of the obturation technique used (4). Therefore, sealers are used as a binding agent and as a lubricant to aid in seating the gutta-
363
364
Oguntebi and Shen
MATERIALS AND METHODS
Journal of Endodontics TABLE 1. List of sealers used along with respective film
thickness
One hundred twenty extracted cuspid teeth without canal calcification, fractures, or apical curvatures greater than 20 degrees were selected from a large collection that had been stored in glycerin. The crowns of the teeth were resected near the cementoenamel junction with a lathe to obtain a uniform root length of 15 mm. A working length was determined radiographically 1 mm short of the root apex and the canals were prepared to an apical size of #40 using K files and copious irrigation with 5.25% sodium hypochlorite. The coronal 4-mm portion of the canal was flared using #40 Hedstrom files, after which the canal walls were smoothed circumferentially with #40 K files. The canals were copiously irrigated with 17% EDTA solution first and then 5.25% sodium hypochlorite solution, dried with paper points, and stored in deionized water for 2 wk before obturation in an attempt to achieve some rehydration of the dentin. The prepared teeth were then randomly divided into six groups of 20 teeth each and coded to ensure anonymity. Thermafil (Tulsa Dental Products, Tulsa, Oklahoma) was selected as the thermoplasticized gutta-percha obturation technique in this study because of its simplicity and the possibility of achieving some degree of standardization. The five root canal sealers (Table l) selected for this study included representatives of sealers currently used in endodontic practice and cements that have been advocated for clinical use which appears to be compatible with the selected thermoplasticized gutta-percha obturation technique. The film thickness of these selected root canal sealers was measured using a modification of the American Dental Association Specification No. 8. Briefly, approximately 0.1 ml of freshly mixed cement was placed between two glass plates and then subjected to a 15-kg dead weight until set. The increase in the combined thickness of the assembly compared with the thickness of the two glass plates only was determined as the film thickness of the sealer. The mean value of triplicate measurements is also shown in Table 1. The obturation technique suggested by the Thermafil manufacturer was utilized for the control group, which received no sealer. The Thermafil device was warmed as recommended by the manufacturer and immediately inserted into the canal, which was taken out of the water storage and dried with paper points. To assure uniform distribution of the sealer around the gutta-percha core which had to be warmed for application, a slight modification of the obturation technique was utilized for the teeth in the experimental groups. Following application of a water-soluble lubricant (Separatin; Brophy, Orange, CA) on the canal walls, the Thermafil devices were warmed as recommended by the manufacturer and immediately inserted into the canals to make an impression of the canal space. The devices were left for 5 min to cool to room temperature and then removed after placing a marker on the device and tooth to ensure reseating in proper alignment. The canal walls and the Thermafil impression were irrigated thoroughly with 5.25% sodium hypochlorite to remove the lubricant. The canal was dried with paper points and coated with freshly mixed root canal sealer with a K file. The Thermafil impression was allowed to air dry, coated with the sealer by rolling it in the same sealer mixture, and then reseated into the canal. Each tooth, after completion of obturation, was
Root Canal Sealer
Type
Film Thickness (um)
Roth's 801 Sealapex Ketac-Cem AH26 Lee EndofU Controls (no sealer)
Zinc oxide-eugenol Calcium hydroxide base Glass ionomer cement Epoxy resin base Condensation silicone None
35.0 38.1 25.8 35.6 12.7 NA*
° NA, not applicable.
TABLE 2. Average depth of dye penetration measured by two examiners
No.
Examiner I
Examiner2
(mm)
(mm)
Controls
18
Sealapex Ketac-Cem Roth's 801 AH26 Lee Endofil
13 17 20 18 16
6.79 __ 1.531 4.77 _+ 1.60,1 4.42 _+0.98 4.08 ___1.01 3.05 + 1.02 2.99 _+ 1.60
Sealer
6.59 + 1.55] 3.85___1.35 I 3.94 _+ 1.08 3.73 __0.99 3.20 + 1.12 2.74 __ 1.35
subjected to a 1-1bpressure in a humidor maintained at 370C for 24 h. The teeth were removed from the humidor, air dried for 12 h, coated with two layers of enamel paint on the surface of the cementum only, left to dry at room temperature for 2 h, and then returned to the humidor overnight. Both apical and coronal ends were not coated with any paint to facilitate the escape of air during subsequent immersion. The apical 1 mm of the teeth was resected using a new #557 fissure bur in a high-speed handpiece to expose the tooth/sealer/Thermafil interface. The obturated teeth were stored in 370C water for 4 wk. Each tooth was then individually suspended in a closed container with 2 mm of the apical end immersed in 0.5% aqueous methylene blue solution, and the incubator temperature was maintained at 37°C for 2 wk. The teeth were removed and split into two longitudinal halves through the apical foramen by cutting 2-mm deep labial and lingual grooves and fracturing the teeth using a hammer and a microtome knife. The degree of microleakage was determined by measurement of the linear extent of the methylene blue dye penetration from the apical end coronally into the root canal by two examiners using a Unitron microscope at a magnification of x400. A two-way analysis of variance was used to test the influence of the examiner and the types of sealers on the experimental data for all groups. The depth of dye penetration values was also analyzed by the following Weibull distribution function (19) to characterize the variation of the experimental data for each group by either examiner, Pc = 1 -
exp[(-L/Lo)']
(1)
where Pt is the percentage of specimens that exhibits the depth of dye penetration below the measured value designated, L, L,, is a normalizing parameter that has no physical significance, and m is the shape factor that delineates the extent of the data variation. The values of dye penetration depth were
Vol. 18, No. 8, August 1992
Sealer Film Thickness and Microleakage
365
TABLE 3. Results of Weibull analysis of the depth of penetration Examiner 1 Sealer
No.
Controls Sealapex Ketac-Cem Roth's 801 AH26 Lee Endofil
Examiner 2
Normalizing Parameter
7.60+0.65
18 13 17 20 18 16
5.46 4.79 4.82 3,47 3.45
2.11+0.511111
_+ 0.51 __+0.10 +__0.17 + 0.20 __+0.19
1.57 2.86 1.73 1.20 1.96
TABLE 4. Calculated percentage of the specimens with 2 mm or less of dye penetration by Weibull analysis Sealer
Examiner 1
Examiner 2
Controls Sealapex Ketac-Cem Roth's 801 AH26 Lee Endofil
5.8 18.7 7.9 19.6 40.3 29.1
4.1 27.4 11.3 26.0 37.0 44.7
Normalizing Parameter
m
i
2.s6+o.8411 [
6.93___0.60
_+ 0.32 ~ _____0.26 i ! __+0.18 _____ 0.16 _____ 0.40
I
m
4.41 4.07 4.24 3.57 3.t2
___0.46 + 0.13 __+0.35 __ 0.20 + 0.22
1.44 2.98 1.60 1.33 1.18
_+0.29 + [ __+0.29 __+0.14 __ 0.17
!
04 ji
10090807060.
/,,; /
e-
50.
..,"
o ,,
40-
,•"
1°,k ¢~
,•
/m
-
'
-
[] L
......
o
..........
•
30100-
o/{ 10- //,~7 e~/~'
209080-
o70-
~
1
l ,it , / ,4",, /o
60-
oj ~ "
•
o/;/_--,
50-
#_
•
/
.~L:~
0
, ,"
.......... _
_
,/i '11 •••"
2
i
i
i
i
i
4
6
8
10
12
Depth of Dye Penetration from the
o
C
14
Apex(mm)
F~G2. Experimental data and Weibull distribution of the depth of dye penetration measured by examiner 2.
40-
...... o: 20-
:
...d
20-
t
10
I,
~
~
;
i~___~..°.~.; -.
00
.'
.
.....
o
°
.
.
~
.........
•
J
i
J
i
J
2
4
6
10
12
14
Depth of Dye Penetration from the Apex (mm) F~G 1. Experimental data and Weibull distribution of the depth of dye penetration measured by examiner 1.
first sorted in ascending order, and a value (
