0099-2399/90/1606-0253/$02.00/0 JOURNAL OF ENDODONTICS Copyright 9 1990 by The American Association of Endodontists
Printed in U.S.A.
VOL. 16, NO. 6, JUNE 1990
SCIENTIFIC ARTICLES Ultrasonic Condensation of Gutta-percha: An In Vitro Dye Penetration and Scanning Electron Microscopic Study Kirk R. Baumgardner, BS, DDS, and Keith, V. Krell DDS, MS, MA
Lateral condensation of gutta-percha with and without ultrasonic activation of the spreader was compared by use of dye penetration analysis and scanning electron photomicrographs of the gutta-percha fills in extracted human incisors and canines. The root canal fillings in three groups of 10 teeth each were laterally condensed using an ultrasonically activated spreader, a fine finger spreader, or a nonactivated ultrasonic spreader. Significantly less apical dye penetration occurred when teeth were obturated using an ultrasonically activated spreader as compared with manual condensation with fine finger spreaders. The ultrasonically condensed gutta-percha mass was more homogeneous with fewer voids compared with guttapercha masses from the two groups that were condensed without ultrasonic activation. A correlation between apical microleakage and the appearance of the gutta-percha mass was seen. All teeth with well-condensed, more homogeneous fillings had low dye penetration. All teeth with a high extent of dye penetration had poorly condensed, less homogeneous fillings. However, not all teeth that had poorly condensed fillings had high dye penetration.
teeth and, therefore, was largely ignored by the profession as a useful adjunct to obturation. Currently, there are several newer ultrasonic instruments that can be used effectively anywhere in the mouth. The purposes of this study were 3-fold: (a) to compare the apical seal produced by three methods of lateral condensation by using dye penetration; (b) to examine the appearance of the gutta-percha masses from the sealability study with the scanning electron microscope; and (c) to determine whether a correlation exists between the appearance of the guttapercha mass and the extent of apical dye penetration. The three methods of lateral condensation that were investigated used an ultrasonically activated spreader, a fine finger spreader, or a nonactivated ultrasonic spreader.
MATERIALS AND M E T H O D S
Canal Preparation and Obturation Thirty-two extracted human incisors and canines with single canals and mature apices were randomly selected and placed into one of three experimental groups and one control group. All teeth were instrumented, cleaned, and shaped using the step-back technique as described by Walton (6). Five milliliters of 2.5% sodium hypochlorite was used as the irrigant between each successive file size. Preparation of the root canal was deemed adequate when the size of the apical stop was at least as large as a #35 file and a fine finger plugger (Sybron/Kerr Co., Romulus, MI) could pass freely to within 1 m m of the final working length. Canals were dried with paper points and, as a final step prior to obturation, a # I 0 file was passed through the apex to ensure patency. All teeth were obturated with gutta-percha and Roth's 801 sealer (Roth Drug Co., Chicago, IL) using one of three methods of lateral condensation. Root canal fillings in group 1 teeth were condensed with spreader tips supplied with the Enac (Osada Electri c Co., Ltd., Osaka, Japan) ultrasonic unit energized at the #3 setting with no water flow. The ultrasonically energized tip was not used in such a manner as to purposely generate enough heat to thermoplasticize the gutta-
Lateral condensation is a widely accepted method for the obturation of the root canal system. Deeper spreader penetration results in a significantly improved apical seal when using this technique (1). Reports of combining ultrasonic energy with a spreader or plugger as an aid in the condensation of gutta-percha have been largely anecdotal(2-4). Moreno (5) suggested that the energy from an ultrasonic insert (PR 30) could be converted to heat and help in softening gutta-percha when using lateral condensation. He demonstrated significant differences in apical dye penetration between teeth obturated with and without the ultrasonic system. Because of the design, the PR 30 ultrasonic insert could only be used in anterior
253
254
Journal of Endodontics
Baumgardner and Krell
percha. The tip was inserted by hand until slight resistance was encountered. Then it was ultrasonically activated as light apical condensing pressure was applied until the predetermined length was achieved. Teeth in group 2 were obturated using fine finger spreaders, and teeth in group 3 were obturated using an Enac spreader tip that was not energized. As per the criteria for the step-back technique (6), the initial depth of spreader penetration in all teeth was within 1 m m of the working length and was controlled by using rubber stoppers. A 5-7 plugger was heated to remove excess gutta-percha from the coronal area and the access opening temporarily sealed with Cavit (Premier Dental Co.). One tooth, serving as a positive control, was instrumented, cleaned and shaped, left unobturated, and temporized identically to all other teeth. As a negative control, one tooth was not treated. All specimens were randomly assigned code numbers by an independent observer not involved with the instrumentation, photography, or grading.
Sealability Study After obturation, all teeth were placed in 100% humidity at 38~ for 48 h. The root surfaces of all teeth, except for the negative control, were then sealed with sticky wax, leaving only a 2 to 3 m m 2 area around the apical foramen exposed. The teeth were placed upright in sealed test tubes with the exposed apices covered by carbon dye (Pelican Ink, Gunther Wagner, Hanover, Germany) for a period of 10 days. Then the teeth were rinsed in water, decalcified with 5% nitric acid, and cleared with methyl salicylate. The dye penetration was measured using a x7 power ocular magnifier (National Tool Co., Cleveland, OH) to the nearest 0.1 mm. The greatest depth of penetration anywhere around (360 degrees) the guttapercha was recorded as the final leakage measurement (Figs. 1 to 3). Two independent measurements were taken of each tooth by different observers. If a difference in measurements between observers was found to be 4 m m or less, the average of the two scores was used as the final recording. If, however, a difference of greater than 4 mm was observed, the tooth was reevaluated by both observers and a final measurement agreed upon. The results were analyzed using a one-factor analysis of variance (ANOVA) statistical test. The Scheffe F test was used for comparisons among the groups.
Scanning Electron Microscopic Analysis The teeth from the sealability study were rinsed in water, dehydrated in 100% alcohol for 1 h, and dried. The teeth were grooved on both the buccal and lingual surfaces and then split with Rongeurs pliers. In 27 of the 30 teeth, a split resulted that extended down the length of the root canal with the gutta-percha mass on one side and the empty canal wall on the other. In three teeth, the gutta-percha was disrupted during the split and could not be used. All specimens were mounted, coated with 20 nm of gold-palladium, and examined using a JEOL 35C scanning electron microscope with secondary electron imaging at 15 kV and a gun bias of 100
FIG 1. Example of a whole tooth that was decalcified and rendered transparent by soaking in methyl salicylate. Dye has penetrated through the apical foramen to point A.
FzA. Photomicrographs were recorded on positive/negative film (Polaroid type 55). Each specimen had one low-power (magnification x l0) photomicrograph showing the apical one-half of the gutta-percha mass. "Split screen" photomicrographs showing the same x 10 low- power image of the apical one-half and an enlarged view of the apical 1 to 2 m m (usually at x320) were subsequently made (Fig. 4). The instant prints were rated by four independent judges using a modification of a grading scheme described by Walton et al. (7). Each examiner was given an identical set of schematic representations with which to rank the homogeneity of the gutta-percha masses (Fig. 5). Grade #1 was nearly perfect, with a wellcondensed, homogeneous gutta-percha mass. Each higher numbered grade showed an increase in the break-up of the gutta-percha mass, with grade #4, the highest grade, showing a total lack of homogeneity of the gutta-percha mass. Typical examples of each grade are shown in Figs. 6 to 10. Nonparametric analysis of the rankings using the Kruskal-Wallis test was performed.
RESULTS The results of the apical dye penetration showed that there were statistically significant differences among the groups. The Scheffe F test showed that group 1, the ultrasonically
Vol. 16, No. 6, June 1990
FIG 2. Example of a tooth with minimal dye penetration.
activated spreader group, was significantly different from group 2, the finger spreader group. Group 2 and group 3, the manual condensing groups, were not significantly different from each other (Table 1). The positive control tooth showed leakage throughout the canal and the negative control tooth showed no leakage. The results of the blind comparison of the scanning electron microscopic photomicrographs are shown in Table 2 and Fig. 11. The ultrasonically condensed group (group 1) had a more consistent, homogeneous fill (p = 0.0007). An example of a group 1 filling is depicted in Fig. 12. Group 2 and group 3 fillings usually exhibited twisting and bending of the accessory points with many points not going to length (Fig. 13). There was no statistical difference between the rankings of groups 2 and 3. The correlation between the photomicrograph rankings and the extent of dye penetration is shown in Table 3. The following trends were noted. The most extensive dye penetration in teeth with rankings of 1 or 2 was 1.9 mm. Any tooth with dye leakage greater than 5.5 m m had a photomicrograph ranking of 3 or 4. In contrast, there were 11 teeth with rankings of 3 or 4 with a maximum leakage of 3.8 m m (all 11 teeth were in group 2 or 3). In other words, teeth that had well-condensed fillings (more homogeneous) had both low dye penetration and low photomicrograph rank. Teeth with poorly condensed fillings (less homogeneous) had high dye penetration and high photomicrograph rank. However, not all teeth that had a high rank had high dye penetration.
Ultrasonic Condensation of Gutta-percha
255
FIG 3. Example of a tooth with gross dye penetration. Penetration of dye extended more than half the length of the canal. Note accessory canal (,4). Entry of dye was restricted to apical foramen.
FIG 4. Typical example of "split screen" photomicrographs that were used to rate the homogeneity of the gutta-percha mass. Sample from group 1, the ultrasonically activated spreader group. Right side, original magnification x l 0 . Left side, area within the box, original magnification x320. G, gutta-percha mass; C, canal wall.
DISCUSSION The reduced apical microleakage with the ultrasonically activated spreader probably is related to the ultrasonic energy plus deep spreader penetration rather than deep spreader
256
Baumgardner and Krell
NO individual a ~ o r / c o n ~ s need Uniform m;c~s wdh ~$y min,o~"crevice rnar~" breaking up ~ ~ f f a ~ t e x ~ e
Journal of Endodontics
Grade 1
:::ii!ii'::iii "Ctewce marks" and/or individual cones. No se~a~abon or fwisting of cones Uniform mass of gult~ perc~a
Grade 2
NO cr~pce marks, indwidual cones ~ either twisting or separaton of cores from mass, or
bothAdecreaseintheuniformitof y rnassof Grade 3
me gul~a pefcha
Lack of und~rmlty of mass Individual cones wrth laroe separat~ns end twisting, OR $i,~:Jle m~r~r c ~ o wdh incoml~eto accedoPt ~ i n t
FIG 6. Typical example of a gutta-percha mass judged "grade 1 ." Note the uniformity of the gutta-percha mass with the surface texture displaying only minor discrepancies termed "crevice marks" (A). This specimen is from group 1, the ultrasonically activated spreader group. B, apex; C , canal wall. Right side, original magnification • Left side, original magnification x 3 2 0 of area within rectangle.
Grade 4
~ace~tn dep~
FIG 5. Schematic representations used t)y examiners to rank the photomicrographs. Each grade is bordered by two schematics that act as boundaries to separate one from the other. The first schematic, that of an "ideal" GP mass, and the second schematic, that of a homogeneous GP mass whose surface texture has only minor discrepancies ("crevice marks"), are the boundaries for the #1 grade. The # 2 grade has the second schematic as its lower boundary and a third schematic, whose surface texture has a less homogeneous mass, as its upper boundary . The # 3 grade follows in sequence using the third schematic that is the upper boundary from the # 2 grade as its lower boundary. The drawing representing the upper boundary of the # 3 grade and the lower boundary of the # 4 grade is a gutta-percha schematic that shows increasingly less uniformity of mass. Individual accessory cones display bending and twisting. Photomicrographs that were ranked grade 4 had a total lack of uniformity of the gutta-percha mass with large separations, twisting, and bending of the cones. Specimens with a single master cone with inadequate accessory point placement depth were also placed in the # 4 grade.
penetration alone. In using the ultrasonically activated spreader, the operator had a distinct impression o f using less force on the spreader. However, spreader loads were not measured during this study. Although accessory points were measured to ensure placement to depth, it was apparent from the photomicrographs that in groups 2 and 3, many times the accessory points were not going to length (Fig. 13). It is unclear from this study why
FIG 7. Typical example of a gutta-percha mass judged "grade 2 : Note the decreased homogeneity of the mass as compared with Fig. 6. This specimen is from group 1, the ultrasonically activated spreader group. C, canal wall. G, gutta-percha mass. A, the apex. Right side, original magnification • Left side, original magnification x320 of area shown in rectangle.
this never occurred in the ultrasonically activated spreader group, but was a c o m m o n occurrence in groups 2 and 3. If the first or second accessory point bends at the tip, a void may occur. The presence of voids in the root canal filling in the apical one-third is thought to be an undesirable situation. The inability of dye penetration to screen out this occurrence in our study raises the same doubts that others (8) have had in using dye penetration as the sole criterion by which to judge a technique (Fig. 14). Other studies (9) using only the physical appearance of the gutta-percha mass as the criterion for a "good fill" have also been challenged (10). By using a
Vol. 16, No. 6, June 1990
FIG 8. Typical example of a gutta-percha mass judged "grade 3." There is an increased lack of homogeneity of the mass with individual accessory points evident. This specimen is from group 2. C, canal wall; G, gutta-percha. Right side, original magnification x l 0. Left side, original magnification x 3 2 0 of area displayed in rectangle.
Ultrasonic Condensation of Gutta-percha
257
FIG 10. Another example of a gutta-percha mass judged grade 4. Apex is on the right. Note single master cone (M) with the twisted accessory cones (A) far short of the apex (B). This specimen is from group 2 (original magnification x l 0).
TABLE 1. One-factor analysis of variance--X: groups 1, 2, and 3; Y: dye measurements Analysis of Variance Source df
Sum Squares
Mean Square
F test
Between groups 2 124.904 62.452 3.699 Within groups 27 455.868 16.884 p = 0.038 Total 29 580.772 Model 11 estimate of between component variance = 22.784 Group
Mean
SD
SE
1, Ultrasonic condensation 2, Finger spreader 3, Enac tip nonactivated
1.2 5.96 2.26
0.79 6.749 2.116
0.25 2.134 0.669
Comparison
FIG 9. Typical example of a gutta-percha mass judged "grade 4." Notice increase in the lack of homogeneity of mass from Figs. 6 to 9. Individual gutta-percha cones (G) are evident. This specimen is from group 2. C, canal wall. Right side, original magnification x l 0 . Left side, original magnification x320 of area displayed in rectangle.
combination of evaluation criteria, it is hoped that the limitations of one evaluation technique are acknowledged and then minimized by using an additional technique. As noted in the results, all teeth that had a high dye penetration also had a high photomicrograph ranking, but not all teeth with a high ranking had high dye penetration. This discrepancy may have occurred because the photomicrograph ranking evaluated the appearance of the entire apical half of the filling, whereas dye penetration only highlighted the discrepancies in the seal at the apical foramen. This study established a correlation between these two evaluation techniques.
Mean Difference Scheffe F test
Group 1, Ultrasonic condensation versus group 2, finger plugger Group 2, Finger plugger versus group 3 Enac tip nonactivated
-4.76
3.355*
3.7
2.027
* Significant at 95%.
TABLE 2. Kruskal-Wallis Xl: experimental groupings/Y~: photo ranking df No. of groups No. of cases H H corrected for ties No. of tied groups
1, Ultrasonic 2, Finger spreader 3, Enac nonactive
2 3 27 13.324 14.42 4
p = 0.0013 p = 0.0007
No. of Cases
~, Rank
Mean Rank
7 10 10
32.5 180.5 165
-0.001 -0.008 -0.007
258
Baumgardner and Krell 4-
3.5-
•
1•
~. 2.5.
._o IE 1.5O
"6
I•
'
Journal of Endodontics TABLE 3. Spearman correlation coefficient--X1: dye measurements; YI: photo ranking* n T.D2 p Z p corrected for ties Z corrected for ties No. of X tied groups: 5
27 1767 0.461 2.349 p = 0.0188 0.438 2.234 p = 0.0255 No, of Y tied groups: 4
* Three teeth deleted because of technique failures.
UltrasonicActive Spreader
FingerSpreader
ENACSpreaderNOT Activated
FIG 11. Mean scores for the photomicrographs by groups. The higher the grade, the less homogeneous the gutta-percha mass.
FIG 14. Photomicrograph of the same tooth as in Fig. 2. Although this specimen had a rank of grade 3, there was minimal dye leakage. This specimen is from group 3 (original magnification x36). A, apicat area; G, gutta-percha; C, canal wall.
FIG 12. High power (original magnification x100) of an ultrasonically activated spreader fill (group 1) approximately 1 mm from the apex. Note the typical appearance of the crevice marks (C) that mark the boundary between the first accessory cone (A) and the master cone (M). This was a common finding in this group. Large arrow points toward the apex of the root.
CONCLUSIONS The results of this study demonstrated that significantly less apical dye penetration occurred when teeth were obturated using an ultrasonically activated spreader as compared with manual condensation with fine finger spreaders. The ultrasonically condensed gutta-percha mass was more homogeneous with fewer voids as compared with gutta-percha masses from the two groups that were condensed without ultrasonic activation. A correlation was established between apical microleakage and the appearance of the gutta-percha mass among the three groups.
Dr. Baumgardner is supported by the Dentist-Scientist program (Grant 1 k16-DE0175). The authors would like to acknowledge the assistancegiven by Dr. Richard Walton, professor and chairman, Department of Endodontics, College of Dentistry, University of Iowa, and by Randy Nessler, BS RA2, for his technical assistance with the JOEL 35C. Dr. Baumgardnerand Dr. Krell are affiliated with the Department of Endodontics, College of Dentistry, University of Iowa, Iowa City, IA.
FIG 13. Example of an accessory cone (A) bending at the tip and stopping short of the spreader placement depth. This specimen is from group 3. S, spreader indentation of the master cone (M). C, canal wall. Large arrow points toward apex (original magnification xl0).
References 1. Allison D, Michelich R, Walton R. The influence of master cone adaptation on the quality of the apical seal. J Endodon 1979;5:298-304.
Vol. 16, No. 6, June 1990 2. Laurichesse J, Canal obturation by means of ultrasonic systems. A new concept: combined ultrasonics thermomechanical and ultrasonic sound vibration technics of obturation. Actual Odontostomato11984;146:233-44. 3, Soulie J. Technic for canal filling using ultrasond. Actual Odontostomatol 1975; 112:591-600, 4. Pelie J, Oriez D, et al. A technique for endodontic obturation: guttapercha and ultrasonics. Rev Odonto-Stornatol Midi FR 1982;40:29-33. 5. Moreno A. Thermomechanically softened gutta-percha root canal filling. J Endodon 1977;3:186-8. 6. Walton R. Histological evaluation of different methods of enlarging the pulp canal space. J Endodon 1976;2:204-11.
Ultrasonic Condensation of Gutta-percha
259
7. Walton R, O'Deil N, Myers D, Lake F, Shimp R. External bleaching of tetracycline stained teeth in dogs, J Endodon 1982;8:536-42. 8. LaCombe J, Campbell A, Hicks L, Pelleu G. A comparison of the apical seal produced by two thermoplasticized injectable gutta-percha techniques. J Endodon 1988;14:445-50. 9. Micanowicz AE, Czonstowsky M, Piesco NP. Low-temperature (70~ injection gutta-percha: a scanning electron microscopic investigation. J Endodon 1986; 12:64-7. 10. Evans J, Simon J. Evaluation of the apical seal produced by injected thermoplasticized gutta-percha in the absence of smear layer and root canal sealer. J Endodon 1986; 12:101-7.
Printed in U.S.A.
VOL. 16, NO. 6, JUNE 1990
SCIENTIFIC ARTICLES Ultrasonic Condensation of Gutta-percha: An In Vitro Dye Penetration and Scanning Electron Microscopic Study Kirk R. Baumgardner, BS, DDS, and Keith, V. Krell DDS, MS, MA
Lateral condensation of gutta-percha with and without ultrasonic activation of the spreader was compared by use of dye penetration analysis and scanning electron photomicrographs of the gutta-percha fills in extracted human incisors and canines. The root canal fillings in three groups of 10 teeth each were laterally condensed using an ultrasonically activated spreader, a fine finger spreader, or a nonactivated ultrasonic spreader. Significantly less apical dye penetration occurred when teeth were obturated using an ultrasonically activated spreader as compared with manual condensation with fine finger spreaders. The ultrasonically condensed gutta-percha mass was more homogeneous with fewer voids compared with guttapercha masses from the two groups that were condensed without ultrasonic activation. A correlation between apical microleakage and the appearance of the gutta-percha mass was seen. All teeth with well-condensed, more homogeneous fillings had low dye penetration. All teeth with a high extent of dye penetration had poorly condensed, less homogeneous fillings. However, not all teeth that had poorly condensed fillings had high dye penetration.
teeth and, therefore, was largely ignored by the profession as a useful adjunct to obturation. Currently, there are several newer ultrasonic instruments that can be used effectively anywhere in the mouth. The purposes of this study were 3-fold: (a) to compare the apical seal produced by three methods of lateral condensation by using dye penetration; (b) to examine the appearance of the gutta-percha masses from the sealability study with the scanning electron microscope; and (c) to determine whether a correlation exists between the appearance of the guttapercha mass and the extent of apical dye penetration. The three methods of lateral condensation that were investigated used an ultrasonically activated spreader, a fine finger spreader, or a nonactivated ultrasonic spreader.
MATERIALS AND M E T H O D S
Canal Preparation and Obturation Thirty-two extracted human incisors and canines with single canals and mature apices were randomly selected and placed into one of three experimental groups and one control group. All teeth were instrumented, cleaned, and shaped using the step-back technique as described by Walton (6). Five milliliters of 2.5% sodium hypochlorite was used as the irrigant between each successive file size. Preparation of the root canal was deemed adequate when the size of the apical stop was at least as large as a #35 file and a fine finger plugger (Sybron/Kerr Co., Romulus, MI) could pass freely to within 1 m m of the final working length. Canals were dried with paper points and, as a final step prior to obturation, a # I 0 file was passed through the apex to ensure patency. All teeth were obturated with gutta-percha and Roth's 801 sealer (Roth Drug Co., Chicago, IL) using one of three methods of lateral condensation. Root canal fillings in group 1 teeth were condensed with spreader tips supplied with the Enac (Osada Electri c Co., Ltd., Osaka, Japan) ultrasonic unit energized at the #3 setting with no water flow. The ultrasonically energized tip was not used in such a manner as to purposely generate enough heat to thermoplasticize the gutta-
Lateral condensation is a widely accepted method for the obturation of the root canal system. Deeper spreader penetration results in a significantly improved apical seal when using this technique (1). Reports of combining ultrasonic energy with a spreader or plugger as an aid in the condensation of gutta-percha have been largely anecdotal(2-4). Moreno (5) suggested that the energy from an ultrasonic insert (PR 30) could be converted to heat and help in softening gutta-percha when using lateral condensation. He demonstrated significant differences in apical dye penetration between teeth obturated with and without the ultrasonic system. Because of the design, the PR 30 ultrasonic insert could only be used in anterior
253
254
Journal of Endodontics
Baumgardner and Krell
percha. The tip was inserted by hand until slight resistance was encountered. Then it was ultrasonically activated as light apical condensing pressure was applied until the predetermined length was achieved. Teeth in group 2 were obturated using fine finger spreaders, and teeth in group 3 were obturated using an Enac spreader tip that was not energized. As per the criteria for the step-back technique (6), the initial depth of spreader penetration in all teeth was within 1 m m of the working length and was controlled by using rubber stoppers. A 5-7 plugger was heated to remove excess gutta-percha from the coronal area and the access opening temporarily sealed with Cavit (Premier Dental Co.). One tooth, serving as a positive control, was instrumented, cleaned and shaped, left unobturated, and temporized identically to all other teeth. As a negative control, one tooth was not treated. All specimens were randomly assigned code numbers by an independent observer not involved with the instrumentation, photography, or grading.
Sealability Study After obturation, all teeth were placed in 100% humidity at 38~ for 48 h. The root surfaces of all teeth, except for the negative control, were then sealed with sticky wax, leaving only a 2 to 3 m m 2 area around the apical foramen exposed. The teeth were placed upright in sealed test tubes with the exposed apices covered by carbon dye (Pelican Ink, Gunther Wagner, Hanover, Germany) for a period of 10 days. Then the teeth were rinsed in water, decalcified with 5% nitric acid, and cleared with methyl salicylate. The dye penetration was measured using a x7 power ocular magnifier (National Tool Co., Cleveland, OH) to the nearest 0.1 mm. The greatest depth of penetration anywhere around (360 degrees) the guttapercha was recorded as the final leakage measurement (Figs. 1 to 3). Two independent measurements were taken of each tooth by different observers. If a difference in measurements between observers was found to be 4 m m or less, the average of the two scores was used as the final recording. If, however, a difference of greater than 4 mm was observed, the tooth was reevaluated by both observers and a final measurement agreed upon. The results were analyzed using a one-factor analysis of variance (ANOVA) statistical test. The Scheffe F test was used for comparisons among the groups.
Scanning Electron Microscopic Analysis The teeth from the sealability study were rinsed in water, dehydrated in 100% alcohol for 1 h, and dried. The teeth were grooved on both the buccal and lingual surfaces and then split with Rongeurs pliers. In 27 of the 30 teeth, a split resulted that extended down the length of the root canal with the gutta-percha mass on one side and the empty canal wall on the other. In three teeth, the gutta-percha was disrupted during the split and could not be used. All specimens were mounted, coated with 20 nm of gold-palladium, and examined using a JEOL 35C scanning electron microscope with secondary electron imaging at 15 kV and a gun bias of 100
FIG 1. Example of a whole tooth that was decalcified and rendered transparent by soaking in methyl salicylate. Dye has penetrated through the apical foramen to point A.
FzA. Photomicrographs were recorded on positive/negative film (Polaroid type 55). Each specimen had one low-power (magnification x l0) photomicrograph showing the apical one-half of the gutta-percha mass. "Split screen" photomicrographs showing the same x 10 low- power image of the apical one-half and an enlarged view of the apical 1 to 2 m m (usually at x320) were subsequently made (Fig. 4). The instant prints were rated by four independent judges using a modification of a grading scheme described by Walton et al. (7). Each examiner was given an identical set of schematic representations with which to rank the homogeneity of the gutta-percha masses (Fig. 5). Grade #1 was nearly perfect, with a wellcondensed, homogeneous gutta-percha mass. Each higher numbered grade showed an increase in the break-up of the gutta-percha mass, with grade #4, the highest grade, showing a total lack of homogeneity of the gutta-percha mass. Typical examples of each grade are shown in Figs. 6 to 10. Nonparametric analysis of the rankings using the Kruskal-Wallis test was performed.
RESULTS The results of the apical dye penetration showed that there were statistically significant differences among the groups. The Scheffe F test showed that group 1, the ultrasonically
Vol. 16, No. 6, June 1990
FIG 2. Example of a tooth with minimal dye penetration.
activated spreader group, was significantly different from group 2, the finger spreader group. Group 2 and group 3, the manual condensing groups, were not significantly different from each other (Table 1). The positive control tooth showed leakage throughout the canal and the negative control tooth showed no leakage. The results of the blind comparison of the scanning electron microscopic photomicrographs are shown in Table 2 and Fig. 11. The ultrasonically condensed group (group 1) had a more consistent, homogeneous fill (p = 0.0007). An example of a group 1 filling is depicted in Fig. 12. Group 2 and group 3 fillings usually exhibited twisting and bending of the accessory points with many points not going to length (Fig. 13). There was no statistical difference between the rankings of groups 2 and 3. The correlation between the photomicrograph rankings and the extent of dye penetration is shown in Table 3. The following trends were noted. The most extensive dye penetration in teeth with rankings of 1 or 2 was 1.9 mm. Any tooth with dye leakage greater than 5.5 m m had a photomicrograph ranking of 3 or 4. In contrast, there were 11 teeth with rankings of 3 or 4 with a maximum leakage of 3.8 m m (all 11 teeth were in group 2 or 3). In other words, teeth that had well-condensed fillings (more homogeneous) had both low dye penetration and low photomicrograph rank. Teeth with poorly condensed fillings (less homogeneous) had high dye penetration and high photomicrograph rank. However, not all teeth that had a high rank had high dye penetration.
Ultrasonic Condensation of Gutta-percha
255
FIG 3. Example of a tooth with gross dye penetration. Penetration of dye extended more than half the length of the canal. Note accessory canal (,4). Entry of dye was restricted to apical foramen.
FIG 4. Typical example of "split screen" photomicrographs that were used to rate the homogeneity of the gutta-percha mass. Sample from group 1, the ultrasonically activated spreader group. Right side, original magnification x l 0 . Left side, area within the box, original magnification x320. G, gutta-percha mass; C, canal wall.
DISCUSSION The reduced apical microleakage with the ultrasonically activated spreader probably is related to the ultrasonic energy plus deep spreader penetration rather than deep spreader
256
Baumgardner and Krell
NO individual a ~ o r / c o n ~ s need Uniform m;c~s wdh ~$y min,o~"crevice rnar~" breaking up ~ ~ f f a ~ t e x ~ e
Journal of Endodontics
Grade 1
:::ii!ii'::iii "Ctewce marks" and/or individual cones. No se~a~abon or fwisting of cones Uniform mass of gult~ perc~a
Grade 2
NO cr~pce marks, indwidual cones ~ either twisting or separaton of cores from mass, or
bothAdecreaseintheuniformitof y rnassof Grade 3
me gul~a pefcha
Lack of und~rmlty of mass Individual cones wrth laroe separat~ns end twisting, OR $i,~:Jle m~r~r c ~ o wdh incoml~eto accedoPt ~ i n t
FIG 6. Typical example of a gutta-percha mass judged "grade 1 ." Note the uniformity of the gutta-percha mass with the surface texture displaying only minor discrepancies termed "crevice marks" (A). This specimen is from group 1, the ultrasonically activated spreader group. B, apex; C , canal wall. Right side, original magnification • Left side, original magnification x 3 2 0 of area within rectangle.
Grade 4
~ace~tn dep~
FIG 5. Schematic representations used t)y examiners to rank the photomicrographs. Each grade is bordered by two schematics that act as boundaries to separate one from the other. The first schematic, that of an "ideal" GP mass, and the second schematic, that of a homogeneous GP mass whose surface texture has only minor discrepancies ("crevice marks"), are the boundaries for the #1 grade. The # 2 grade has the second schematic as its lower boundary and a third schematic, whose surface texture has a less homogeneous mass, as its upper boundary . The # 3 grade follows in sequence using the third schematic that is the upper boundary from the # 2 grade as its lower boundary. The drawing representing the upper boundary of the # 3 grade and the lower boundary of the # 4 grade is a gutta-percha schematic that shows increasingly less uniformity of mass. Individual accessory cones display bending and twisting. Photomicrographs that were ranked grade 4 had a total lack of uniformity of the gutta-percha mass with large separations, twisting, and bending of the cones. Specimens with a single master cone with inadequate accessory point placement depth were also placed in the # 4 grade.
penetration alone. In using the ultrasonically activated spreader, the operator had a distinct impression o f using less force on the spreader. However, spreader loads were not measured during this study. Although accessory points were measured to ensure placement to depth, it was apparent from the photomicrographs that in groups 2 and 3, many times the accessory points were not going to length (Fig. 13). It is unclear from this study why
FIG 7. Typical example of a gutta-percha mass judged "grade 2 : Note the decreased homogeneity of the mass as compared with Fig. 6. This specimen is from group 1, the ultrasonically activated spreader group. C, canal wall. G, gutta-percha mass. A, the apex. Right side, original magnification • Left side, original magnification x320 of area shown in rectangle.
this never occurred in the ultrasonically activated spreader group, but was a c o m m o n occurrence in groups 2 and 3. If the first or second accessory point bends at the tip, a void may occur. The presence of voids in the root canal filling in the apical one-third is thought to be an undesirable situation. The inability of dye penetration to screen out this occurrence in our study raises the same doubts that others (8) have had in using dye penetration as the sole criterion by which to judge a technique (Fig. 14). Other studies (9) using only the physical appearance of the gutta-percha mass as the criterion for a "good fill" have also been challenged (10). By using a
Vol. 16, No. 6, June 1990
FIG 8. Typical example of a gutta-percha mass judged "grade 3." There is an increased lack of homogeneity of the mass with individual accessory points evident. This specimen is from group 2. C, canal wall; G, gutta-percha. Right side, original magnification x l 0. Left side, original magnification x 3 2 0 of area displayed in rectangle.
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257
FIG 10. Another example of a gutta-percha mass judged grade 4. Apex is on the right. Note single master cone (M) with the twisted accessory cones (A) far short of the apex (B). This specimen is from group 2 (original magnification x l 0).
TABLE 1. One-factor analysis of variance--X: groups 1, 2, and 3; Y: dye measurements Analysis of Variance Source df
Sum Squares
Mean Square
F test
Between groups 2 124.904 62.452 3.699 Within groups 27 455.868 16.884 p = 0.038 Total 29 580.772 Model 11 estimate of between component variance = 22.784 Group
Mean
SD
SE
1, Ultrasonic condensation 2, Finger spreader 3, Enac tip nonactivated
1.2 5.96 2.26
0.79 6.749 2.116
0.25 2.134 0.669
Comparison
FIG 9. Typical example of a gutta-percha mass judged "grade 4." Notice increase in the lack of homogeneity of mass from Figs. 6 to 9. Individual gutta-percha cones (G) are evident. This specimen is from group 2. C, canal wall. Right side, original magnification x l 0 . Left side, original magnification x320 of area displayed in rectangle.
combination of evaluation criteria, it is hoped that the limitations of one evaluation technique are acknowledged and then minimized by using an additional technique. As noted in the results, all teeth that had a high dye penetration also had a high photomicrograph ranking, but not all teeth with a high ranking had high dye penetration. This discrepancy may have occurred because the photomicrograph ranking evaluated the appearance of the entire apical half of the filling, whereas dye penetration only highlighted the discrepancies in the seal at the apical foramen. This study established a correlation between these two evaluation techniques.
Mean Difference Scheffe F test
Group 1, Ultrasonic condensation versus group 2, finger plugger Group 2, Finger plugger versus group 3 Enac tip nonactivated
-4.76
3.355*
3.7
2.027
* Significant at 95%.
TABLE 2. Kruskal-Wallis Xl: experimental groupings/Y~: photo ranking df No. of groups No. of cases H H corrected for ties No. of tied groups
1, Ultrasonic 2, Finger spreader 3, Enac nonactive
2 3 27 13.324 14.42 4
p = 0.0013 p = 0.0007
No. of Cases
~, Rank
Mean Rank
7 10 10
32.5 180.5 165
-0.001 -0.008 -0.007
258
Baumgardner and Krell 4-
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Journal of Endodontics TABLE 3. Spearman correlation coefficient--X1: dye measurements; YI: photo ranking* n T.D2 p Z p corrected for ties Z corrected for ties No. of X tied groups: 5
27 1767 0.461 2.349 p = 0.0188 0.438 2.234 p = 0.0255 No, of Y tied groups: 4
* Three teeth deleted because of technique failures.
UltrasonicActive Spreader
FingerSpreader
ENACSpreaderNOT Activated
FIG 11. Mean scores for the photomicrographs by groups. The higher the grade, the less homogeneous the gutta-percha mass.
FIG 14. Photomicrograph of the same tooth as in Fig. 2. Although this specimen had a rank of grade 3, there was minimal dye leakage. This specimen is from group 3 (original magnification x36). A, apicat area; G, gutta-percha; C, canal wall.
FIG 12. High power (original magnification x100) of an ultrasonically activated spreader fill (group 1) approximately 1 mm from the apex. Note the typical appearance of the crevice marks (C) that mark the boundary between the first accessory cone (A) and the master cone (M). This was a common finding in this group. Large arrow points toward the apex of the root.
CONCLUSIONS The results of this study demonstrated that significantly less apical dye penetration occurred when teeth were obturated using an ultrasonically activated spreader as compared with manual condensation with fine finger spreaders. The ultrasonically condensed gutta-percha mass was more homogeneous with fewer voids as compared with gutta-percha masses from the two groups that were condensed without ultrasonic activation. A correlation was established between apical microleakage and the appearance of the gutta-percha mass among the three groups.
Dr. Baumgardner is supported by the Dentist-Scientist program (Grant 1 k16-DE0175). The authors would like to acknowledge the assistancegiven by Dr. Richard Walton, professor and chairman, Department of Endodontics, College of Dentistry, University of Iowa, and by Randy Nessler, BS RA2, for his technical assistance with the JOEL 35C. Dr. Baumgardnerand Dr. Krell are affiliated with the Department of Endodontics, College of Dentistry, University of Iowa, Iowa City, IA.
FIG 13. Example of an accessory cone (A) bending at the tip and stopping short of the spreader placement depth. This specimen is from group 3. S, spreader indentation of the master cone (M). C, canal wall. Large arrow points toward apex (original magnification xl0).
References 1. Allison D, Michelich R, Walton R. The influence of master cone adaptation on the quality of the apical seal. J Endodon 1979;5:298-304.
Vol. 16, No. 6, June 1990 2. Laurichesse J, Canal obturation by means of ultrasonic systems. A new concept: combined ultrasonics thermomechanical and ultrasonic sound vibration technics of obturation. Actual Odontostomato11984;146:233-44. 3, Soulie J. Technic for canal filling using ultrasond. Actual Odontostomatol 1975; 112:591-600, 4. Pelie J, Oriez D, et al. A technique for endodontic obturation: guttapercha and ultrasonics. Rev Odonto-Stornatol Midi FR 1982;40:29-33. 5. Moreno A. Thermomechanically softened gutta-percha root canal filling. J Endodon 1977;3:186-8. 6. Walton R. Histological evaluation of different methods of enlarging the pulp canal space. J Endodon 1976;2:204-11.
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7. Walton R, O'Deil N, Myers D, Lake F, Shimp R. External bleaching of tetracycline stained teeth in dogs, J Endodon 1982;8:536-42. 8. LaCombe J, Campbell A, Hicks L, Pelleu G. A comparison of the apical seal produced by two thermoplasticized injectable gutta-percha techniques. J Endodon 1988;14:445-50. 9. Micanowicz AE, Czonstowsky M, Piesco NP. Low-temperature (70~ injection gutta-percha: a scanning electron microscopic investigation. J Endodon 1986; 12:64-7. 10. Evans J, Simon J. Evaluation of the apical seal produced by injected thermoplasticized gutta-percha in the absence of smear layer and root canal sealer. J Endodon 1986; 12:101-7.
