- Email: [email protected]
Penetration Depth of Warm Vertical Gutta-Percha Pluggers: Impact of Apical Preparation
Basic Research—Technology
Penetration Depth of Warm Vertical Gutta-Percha Pluggers: Impact of Apical Preparation Franck Diemer, DCD,* Aline Sinan, DCD†, and Paul Calas, DCD, DU* Abstract The warm vertical gutta-percha compaction technique requires canals to be sufficiently flared to allow the tip of the plugger to penetrate to the apical third. The aim of the present study was to determine whether apical preparation or finishing instruments could be used to improve the penetration depth of pluggers. Single-root canals (48) were prepared using different rotary Ni-Ti instruments: M File System (I), ProTaper (II), HEROShaper (III), and EndoK3 (IV). Finger and heat (Endotwinn) pluggers were introduced into the canals, one after the other, and their penetration depths were measured. The apical thirds of the canals were then flared with specific instrumentation and the penetration depths of the pluggers were once again measured. After the initial preparation, the smallest diameter pluggers (No. 1 and F) could be inserted 5 to 7 mm short of working length without difficulty. Apical flaring improved the maximum penetration depth of the finger plugger by 1.76 mm and the heat plugger by 1.52 mm The deepest penetration was obtained with the EndoK3, ProTaper, and HEROShaper instruments. By accentuating the taper, apical flaring facilitated the penetration of warm vertical gutta-percha compaction pluggers. (J Endod 2006;32:123–126)
F
Key Words
X-rays were taken of extracted, single-root teeth stored in 4% formaldehyde. Only those with canal curves under 15 degrees (11) and WL of 17 to 23 mm were selected for the study. Access cavities were prepared in 48 teeth and the cuspids were slightly abraded to provide reference points to compare penetration depths. The teeth were randomly distributed into four groups of 12 teeth. The canals were then prepared using the following rotary Ni-Ti instruments, according to the protocol recommended by each manufacturer:
Apical preparation, plugger penetration, root canal filling
*From the Faculté de Chirurgie Dentaire de Toulouse, Toulouse, France; †Faculté de Chirurgie Dentaire d’Abidjan, Ivory Coast, France. Address requests for reprint to Dr. Franck Diemer, Faculté de Chirurgie Dentaire de Toulouse, 3 chemin des maraîchers, 31400 Toulouse, France. E-mail address: franck. [email protected]. 0099-2399/$0 - see front matter Copyright © 2006 by the American Association of Endodontists. doi:10.1016/j.joen.2005.10.021
illings protect cleaned, shaped canals and prevent infiltration of apical tissue fluids (1). They must seal the apical foramina and accessory canals as well as the entire three-dimensional space of the root canal. A number of filling techniques, most of which involve compacting gutta-percha in the root canal, have been described in the literature. These techniques have been compared in vitro using a number of approaches, including dye and radioactive tracer penetration, bacterial leakage, and fluid filtration (2, 3). Many of these studies have shown that the warm vertical condensation technique provides excellent results (4 –7). The Toronto study confirmed that combining flaring with vertical gutta-percha compaction greatly improves healing (8). Warm vertical condensation was first described by Schilder (1), who used finger pluggers, and was later simplified by Buchanan (9), who introduced electrically heated pluggers. However, this technique requires that the plugger penetrate 5 to 7 mm short of working length (WL) (9). To achieve this, the canal must be sufficiently flared and tapered and the apical portion must be enlarged. Low speed, continuously rotating Ni-Ti instruments with pronounced tapers combined with the crown down technique are ideal for achieving these objectives (10). While there is no doubt that coronal portion needs to be enlarged, the apical portion must also be sufficiently enlarged to allow the plugger to penetrate deeply enough to condense the gutta-percha in the apical portion of the canal. The aim of this study was to evaluate the penetration depth of two types of pluggers in canals prepared using four different instrument sequences, and to determine whether finishing or apical preparation instruments could increase the penetration depth of pluggers.
Materials and Methods
Group I: M File System (Komet, Besigheim, Germany). The first preparation instrument (M File 1, 0.06, #30) was inserted halfway into the canal. The other two instruments in the sequence (M File 2, 0.04, #30, and M File 3, 0.02, #30) were inserted to WL–2 mm and WL. Group II: ProTaper (Maillefer, Ballaigues, Switzerland). The three instruments in the sequence (S1, S2, F1) were all used for the entire WL down to the apical preparation limit. Group III: HEROShaper No. 30 (Micro Méga, Besançon, France). The two instruments in this sequence were inserted to two-thirds WL (0.06 taper) and to WL (0.04 taper), respectively. Group IV: EndoK3 (SybronEndo, Orange, CA). All the instruments in this sequence (35, 30, 25, 20) have a 0.06 taper. The step down technique was used and the apical preparation was finished with a #25 file. Manufacturer-recommended speeds and preparation techniques were used. A 2.6° sodium hypochlorite irrigating solution was used throughout the canal preparations (30 ml for each canal).
JOE — Volume 32, Number 2, February 2006
Penetration Depth of Warm Vertical Gutta-Percha Pluggers
123
Basic Research—Technology TABLE 1. Penetration depths of four manual (S2815) heat carrier pluggers (P1, P2, P3 and P4).
Once the preparations were completed, vertical condensation pluggers were introduced into the canals of all the teeth. Maximum penetration depths with respect to the coronal reference point used to determine the WL were measured using a 1/100 mm resolution digital caliper (Absolute Digimatic, Mitutoyo, England). A calibration was performed before the measurements. Two warm vertical condensation plugger models were used: a series of four cylindrical S2815 heat carrier pluggers (1, 2, 3, and 4) (Maillefer, Ballaigues, Switzerland) and four heat pluggers (F, FM, ML, and L) (EndoTwinn, Amsterdam, The Netherlands) with the respective tapers: 0.03, 0.05, 0.06, and 0.08. The apical portion of the root canals of teeth from the four groups was then enlarged using the following files:
Group I: M File 3, 0.02, # 35, 40, and 45 (Komet) Group II: ProTaper, F2 et F3 (Maillefer) Group III: HEROApical, # 30, 0.06, and 0.08 (Micro Méga) Group IV: EndoK3, 0.06, # 30 and 35 (SybronEndo) The instruments, which were used according to the manufacturers’ instructions, were all inserted to WL with constant irrigation (30 ml for each canal). The pluggers were once again inserted in the canals and the penetration depths were measured to determine whether the additional treatment steps improved penetration. The measurements were taken in
TABLE 2. Penetration depths of four heat pluggers (EndoTwinn) (ET F, ET FM, ET ML, and ET L).
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JOE — Volume 32, Number 2, February 2006
Basic Research—Technology TABLE 3. Average gain (in mm) of penetration depth by technique Manual pluggers
Group I Group II Group III Group IV Average
Heat pluggers
1
2
3
4
F
FM
ML
L
1.001 2.124 1.868 2.075 1.767
0.434 2.080 1.518 1.661 1.423
0.564 1.573 0.643 1.723 1.780
0.781 0.705 0.463 1.958 0.977
0.574 2.117 1.422 1.958 1.518
0.432 1.796 0.549 1.732 1.127
0.473 1.451 0.413 1.593 0.983
0.448 1.067 0.294 0.937 0.686
duplicate by two independent operators. An analysis of variance and a Student multiple range test were used to analyze the data. The equality of variance between the two operators was evaluated. All the statistical tests were interpreted at the 5% significance level.
Results Because there was no significant difference between the measurements taken by the two operators (p ⫽ 0.2247), they were averaged. After the initial preparation (Tables 1 and 2), no difficulty was encountered in inserting the smallest diameter pluggers (No. 1 and F) to under 7 mm short of WL in most cases: 92 to 100% for groups II, III, and IV, and 83 to 91.7% for group I. When all the preparation techniques were taken into consideration, the larger diameter pluggers could be inserted to the same depth 70% of the time with the FM but only 40% of the time with the No. 2. The other pluggers could not be inserted deeper than 7 mm short of WL except for ML (67 to 88% of the time for groups II, III, and IV, and 45% of the time for group I). Flaring the apical portion improved the penetration depth of the pluggers (Tables 1 and 2). Taking all the techniques into consideration, there was a 1.52 mm average gain in penetration depth (Table 3) for plugger F and 1.76 mm for plugger No. 1. Plugger F could even be inserted to less than 5 mm short of WL in all the group II, III, and IV teeth (Table 2). Plugger No. 2 could only be inserted to under 7 mm short of WL in the group II, III, and IV teeth 95% of the time, while plugger FM could be inserted to under 7 mm short of working length in the group II, III, and IV teeth 100% of the time. The penetration depth of the No. 3, No. 4, and L pluggers was insufficient in all cases. However, the ML plugger could be inserted to less than 7 mm short of WL 85% of the time in the group II, III, and IV teeth. The K3, ProTaper, and HeroShaper sequence resulted in the deepest penetration depths. The average gain in penetration depth depended on the plugger (Table 3), and was 0.705 to 2.124 mm for the ProTaper, 0.937 to 2.075 mm for the K3, and 0.294 to 1.868 mm for the HeroShaper.
Discussion The canals of natural teeth were selected to evaluate the penetration depth of the pluggers. The theoretical penetration depth could have been evaluated by comparing the apical diameters of the pluggers with the tip diameters of the preparation instruments, taking into account their respective tapers. However, the use of natural teeth made it possible to take the following two variables into consideration: ●
●
Canal anatomy: Anatomical variations (enlargements, oval root canals, etc.) are frequent and cannot be easily simulated using a linear, theoretical model. Preparation shape: The shape of the canal can vary with the technique. For example, the brushing technique accentuates the taper of
JOE — Volume 32, Number 2, February 2006
Average Plugger 1 to 4
Average EndoTwinn pluggers F to L
0.695 1.621 1.123 1.854 1.487
0.482 1.608 0.669 1.555 1.078
the canal. The diameter of the prepared canal may thus be greater than that of the last instrument used. However, by selecting straight and slightly curved canals, we did not have to contend with the difficulty of inserting a plugger into a highly curved canal. Clinical conditions were not totally reproduced because the pluggers were inserted into the canals without filling material, sealer, or gutta-percha. While the lubrifying action of the sealer may facilitate the insertion of the plugger, this is not the case for gutta-percha, which can not only slow the insertion of the plugger as it is compacted, but the gutta-percha may also get between the canal walls and the plugger. Two techniques can be used to fill canals by warm vertical compaction of gutta-percha. The classic approach, which is based on the technique first described by Schilder (1), involves softening the guttapercha using a heat carrier and then compacting it with a plugger. The two operations can also be performed simultaneously using heat pluggers (9) such as the System B (SybronEndo) and the Endotwinn (EndoTwinn). In the present study, two plugger models, one for each filling technique, were tested. Endotwinn pluggers could be inserted deeper than the finger pluggers because of their marked cylindrical taper compared to the more cylindrical shape of the finger pluggers. Yared and Bou Dagher (12) confirmed that pluggers must be inserted to within 5 to 7 mm of the apex to achieve efficient gutta-percha condensation and a tight apical seal. The smallest pluggers tested in our study (No. 1 finger and F heat) could both be inserted to this depth. Apical flaring also made it possible for larger diameter pluggers (No. 2 finger, FM, and, in certain cases, ML heat) to be inserted to within 5 to 7 mm of the apex. However, the ease of penetration of the pluggers depended on the size and taper of the preparation instruments. The M File instruments were the least effective. The smaller taper and shorter length of the active portion limited their ability to flare the canal and thus the depth to which the pluggers could penetrate. It is important to remember that in the present study only the result, that is, the shape of the preparation, was taken into consideration for comparison purposes. However, other criteria such as the strength of the Ni-Ti alloy and the cutting efficiency could have been used. Further research is warranted to study subtle differences between the four systems. To obtain a good seal, the gutta-percha master cone must be sufficiently soft to adapt perfectly to the shape of the canal walls (11). This depends on heating temperature, application time, and insertion depth (13). Smith et al. (14) showed that the heat must be applied to within 3 mm short of WL to soften the master cone and ensure good adaptation to the canal wall. This was confirmed by Bowman and Baumgartner (15). Given this, if pluggers are used in combination with a heat source, they may have to be inserted to less than 5 mm short of the WL. This would be possible after apical flaring using the group II, III, and IV techniques with the F Endotwinn plugger. However, Smith et al. (14) obtained this result using a two-step technique: heating followed by
Penetration Depth of Warm Vertical Gutta-Percha Pluggers
125
Basic Research—Technology compaction with a plugger. Heat pluggers reduce cooling of the guttapercha before compaction. In addition, with combination systems, heating is more homogeneous and can be applied simultaneously with the compaction. Compaction plays an important role. Venturi and al. showed that “a better quality of apical filling can be obtained using vertical compaction with apical back-fill” (16). Enlarging the apical third facilitates plugger penetration. However, enlarging the apical portion may compromise the integrity of the filling. Yared and Bou Dagher (11) reported that the seal is tighter when the apical portion of the canal is smaller. Apical infiltration is less common with canals prepared with No. 25 files than those prepared with No. 40 files. Wu et al. (17) also reported that the greater the width of the apical root canal, the more difficult it was to completely fill the canal with gutta-percha. To facilitate the penetration of pluggers, it is thus preferable to flare the canal while keeping the width of the apical portion to a minimum. This can be achieved using Ni-Ti instruments with large tapers. The results of the present study show that apical flaring using instruments with large tapers facilitates the penetration of warm vertical gutta-percha compaction pluggers. This type of preparation also limits the risk of apical infiltration and promotes good adaptation of the master cone to the canal walls.
Acknowledgment The authors would like to especially thank Dr. Jean Philippe Mallet for his valuable advice and comments on the manuscript.
References 1. Schilder H. Filling root canals in three dimensions. Dent Clin North Am 1967;11:723– 44.
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2. Barthel CR, Moshonov J, Shuping G, Orstavik D. Bacterial leakage versus dye leakage in obturated root canals. Int Endod J 1999;32:370 –5. 3. Pommel L, Jacquot B, Camps J. Lack of correlation among three methods for evaluation of apical leakage. J Endod 2001;27:347–50. 4. Wong M, Peters DD, Lorton L. Comparison of gutta percha filling techniques, compaction (mechanical), vertical (warm) and lateral condensation techniques. Part 1. J Endod 1981;7:551– 8. 5. Yared GM, Bou Dagher F. Sealing ability of the vertical condensation with different root canal sealers. J Endod 1996;22:6 – 8. 6. Pommel L, Camps J. In vitro apical leakage of system B compared with other filling techniques. J Endod 2001;27:449 –51. 7. Lea CS, Apicella MJ, Mines P, Yancich PP, Parker MH. Comparison of the obturation density of cold lateral compaction versus warm vertical compaction using the continuous wave of condensation technique. J Endod 2005;31:37–9. 8. Farzaneh M, Abitbol S, Lawrence HP, Friedman S. Treatment outcome in endodontics: the Toronto study. Phase II : initial treatment. J Endod 2004;30:302–9. 9. Buchanan LS. The continuous wave of obturation technique: ‘centered’ condensation warm gutta-percha in 12 seconds. Dent Today 1996;15:60 –7. 10. Marlin J, Schilder H. Physical properties of gutta-percha when subjected to heat and vertical condensation. Oral Surg Oral Med Oral Pathol 1973;36:872–9. 11. Yared GM, Bou Dagher F E. Apical enlargement: influence on the sealing ability of the vertical compaction technique. J Endod 1994;20:313– 4. 12. Yared GM, Bou Dagher FE. Influence of plugger penetration on the sealing ability of vertical condensation. J Endod 1995;21:152–3. 13. Venturi M, Pasquantonio G, Falconi M, Breschi L. Temperature change within guttapercha induced by the system-B heat source. Int Endod J 2002;35:740 – 6. 14. Smith RS, Weller RN, Loushine RJ, Kimbrough WF. Effect of varying the depth of heat application on the adaptability of gutta-percha during warm vertical compaction. J Endod 2000;26:668 –72. 15. Bowman CJ, Baumgartner JC. Gutta-percha obturation of lateral grooves and depressions. J Endod 2002;28:220 –3. 16. Venturi M, Breschi L. Evaluation of apical filling after warm vertical gutta-percha compaction using different procedures. J Endod 2004;30:436 – 40. 17. Wu MK, van der Sluis LW, Wesselink PR. A preliminary study of the percentage of gutta-percha filled area in the apical canal filled with vertically compacted warm gutta-percha. Int Endod J 2002;35:527–35.
JOE — Volume 32, Number 2, February 2006
Penetration Depth of Warm Vertical Gutta-Percha Pluggers: Impact of Apical Preparation Franck Diemer, DCD,* Aline Sinan, DCD†, and Paul Calas, DCD, DU* Abstract The warm vertical gutta-percha compaction technique requires canals to be sufficiently flared to allow the tip of the plugger to penetrate to the apical third. The aim of the present study was to determine whether apical preparation or finishing instruments could be used to improve the penetration depth of pluggers. Single-root canals (48) were prepared using different rotary Ni-Ti instruments: M File System (I), ProTaper (II), HEROShaper (III), and EndoK3 (IV). Finger and heat (Endotwinn) pluggers were introduced into the canals, one after the other, and their penetration depths were measured. The apical thirds of the canals were then flared with specific instrumentation and the penetration depths of the pluggers were once again measured. After the initial preparation, the smallest diameter pluggers (No. 1 and F) could be inserted 5 to 7 mm short of working length without difficulty. Apical flaring improved the maximum penetration depth of the finger plugger by 1.76 mm and the heat plugger by 1.52 mm The deepest penetration was obtained with the EndoK3, ProTaper, and HEROShaper instruments. By accentuating the taper, apical flaring facilitated the penetration of warm vertical gutta-percha compaction pluggers. (J Endod 2006;32:123–126)
F
Key Words
X-rays were taken of extracted, single-root teeth stored in 4% formaldehyde. Only those with canal curves under 15 degrees (11) and WL of 17 to 23 mm were selected for the study. Access cavities were prepared in 48 teeth and the cuspids were slightly abraded to provide reference points to compare penetration depths. The teeth were randomly distributed into four groups of 12 teeth. The canals were then prepared using the following rotary Ni-Ti instruments, according to the protocol recommended by each manufacturer:
Apical preparation, plugger penetration, root canal filling
*From the Faculté de Chirurgie Dentaire de Toulouse, Toulouse, France; †Faculté de Chirurgie Dentaire d’Abidjan, Ivory Coast, France. Address requests for reprint to Dr. Franck Diemer, Faculté de Chirurgie Dentaire de Toulouse, 3 chemin des maraîchers, 31400 Toulouse, France. E-mail address: franck. [email protected]. 0099-2399/$0 - see front matter Copyright © 2006 by the American Association of Endodontists. doi:10.1016/j.joen.2005.10.021
illings protect cleaned, shaped canals and prevent infiltration of apical tissue fluids (1). They must seal the apical foramina and accessory canals as well as the entire three-dimensional space of the root canal. A number of filling techniques, most of which involve compacting gutta-percha in the root canal, have been described in the literature. These techniques have been compared in vitro using a number of approaches, including dye and radioactive tracer penetration, bacterial leakage, and fluid filtration (2, 3). Many of these studies have shown that the warm vertical condensation technique provides excellent results (4 –7). The Toronto study confirmed that combining flaring with vertical gutta-percha compaction greatly improves healing (8). Warm vertical condensation was first described by Schilder (1), who used finger pluggers, and was later simplified by Buchanan (9), who introduced electrically heated pluggers. However, this technique requires that the plugger penetrate 5 to 7 mm short of working length (WL) (9). To achieve this, the canal must be sufficiently flared and tapered and the apical portion must be enlarged. Low speed, continuously rotating Ni-Ti instruments with pronounced tapers combined with the crown down technique are ideal for achieving these objectives (10). While there is no doubt that coronal portion needs to be enlarged, the apical portion must also be sufficiently enlarged to allow the plugger to penetrate deeply enough to condense the gutta-percha in the apical portion of the canal. The aim of this study was to evaluate the penetration depth of two types of pluggers in canals prepared using four different instrument sequences, and to determine whether finishing or apical preparation instruments could increase the penetration depth of pluggers.
Materials and Methods
Group I: M File System (Komet, Besigheim, Germany). The first preparation instrument (M File 1, 0.06, #30) was inserted halfway into the canal. The other two instruments in the sequence (M File 2, 0.04, #30, and M File 3, 0.02, #30) were inserted to WL–2 mm and WL. Group II: ProTaper (Maillefer, Ballaigues, Switzerland). The three instruments in the sequence (S1, S2, F1) were all used for the entire WL down to the apical preparation limit. Group III: HEROShaper No. 30 (Micro Méga, Besançon, France). The two instruments in this sequence were inserted to two-thirds WL (0.06 taper) and to WL (0.04 taper), respectively. Group IV: EndoK3 (SybronEndo, Orange, CA). All the instruments in this sequence (35, 30, 25, 20) have a 0.06 taper. The step down technique was used and the apical preparation was finished with a #25 file. Manufacturer-recommended speeds and preparation techniques were used. A 2.6° sodium hypochlorite irrigating solution was used throughout the canal preparations (30 ml for each canal).
JOE — Volume 32, Number 2, February 2006
Penetration Depth of Warm Vertical Gutta-Percha Pluggers
123
Basic Research—Technology TABLE 1. Penetration depths of four manual (S2815) heat carrier pluggers (P1, P2, P3 and P4).
Once the preparations were completed, vertical condensation pluggers were introduced into the canals of all the teeth. Maximum penetration depths with respect to the coronal reference point used to determine the WL were measured using a 1/100 mm resolution digital caliper (Absolute Digimatic, Mitutoyo, England). A calibration was performed before the measurements. Two warm vertical condensation plugger models were used: a series of four cylindrical S2815 heat carrier pluggers (1, 2, 3, and 4) (Maillefer, Ballaigues, Switzerland) and four heat pluggers (F, FM, ML, and L) (EndoTwinn, Amsterdam, The Netherlands) with the respective tapers: 0.03, 0.05, 0.06, and 0.08. The apical portion of the root canals of teeth from the four groups was then enlarged using the following files:
Group I: M File 3, 0.02, # 35, 40, and 45 (Komet) Group II: ProTaper, F2 et F3 (Maillefer) Group III: HEROApical, # 30, 0.06, and 0.08 (Micro Méga) Group IV: EndoK3, 0.06, # 30 and 35 (SybronEndo) The instruments, which were used according to the manufacturers’ instructions, were all inserted to WL with constant irrigation (30 ml for each canal). The pluggers were once again inserted in the canals and the penetration depths were measured to determine whether the additional treatment steps improved penetration. The measurements were taken in
TABLE 2. Penetration depths of four heat pluggers (EndoTwinn) (ET F, ET FM, ET ML, and ET L).
124
Diemer et al.
JOE — Volume 32, Number 2, February 2006
Basic Research—Technology TABLE 3. Average gain (in mm) of penetration depth by technique Manual pluggers
Group I Group II Group III Group IV Average
Heat pluggers
1
2
3
4
F
FM
ML
L
1.001 2.124 1.868 2.075 1.767
0.434 2.080 1.518 1.661 1.423
0.564 1.573 0.643 1.723 1.780
0.781 0.705 0.463 1.958 0.977
0.574 2.117 1.422 1.958 1.518
0.432 1.796 0.549 1.732 1.127
0.473 1.451 0.413 1.593 0.983
0.448 1.067 0.294 0.937 0.686
duplicate by two independent operators. An analysis of variance and a Student multiple range test were used to analyze the data. The equality of variance between the two operators was evaluated. All the statistical tests were interpreted at the 5% significance level.
Results Because there was no significant difference between the measurements taken by the two operators (p ⫽ 0.2247), they were averaged. After the initial preparation (Tables 1 and 2), no difficulty was encountered in inserting the smallest diameter pluggers (No. 1 and F) to under 7 mm short of WL in most cases: 92 to 100% for groups II, III, and IV, and 83 to 91.7% for group I. When all the preparation techniques were taken into consideration, the larger diameter pluggers could be inserted to the same depth 70% of the time with the FM but only 40% of the time with the No. 2. The other pluggers could not be inserted deeper than 7 mm short of WL except for ML (67 to 88% of the time for groups II, III, and IV, and 45% of the time for group I). Flaring the apical portion improved the penetration depth of the pluggers (Tables 1 and 2). Taking all the techniques into consideration, there was a 1.52 mm average gain in penetration depth (Table 3) for plugger F and 1.76 mm for plugger No. 1. Plugger F could even be inserted to less than 5 mm short of WL in all the group II, III, and IV teeth (Table 2). Plugger No. 2 could only be inserted to under 7 mm short of WL in the group II, III, and IV teeth 95% of the time, while plugger FM could be inserted to under 7 mm short of working length in the group II, III, and IV teeth 100% of the time. The penetration depth of the No. 3, No. 4, and L pluggers was insufficient in all cases. However, the ML plugger could be inserted to less than 7 mm short of WL 85% of the time in the group II, III, and IV teeth. The K3, ProTaper, and HeroShaper sequence resulted in the deepest penetration depths. The average gain in penetration depth depended on the plugger (Table 3), and was 0.705 to 2.124 mm for the ProTaper, 0.937 to 2.075 mm for the K3, and 0.294 to 1.868 mm for the HeroShaper.
Discussion The canals of natural teeth were selected to evaluate the penetration depth of the pluggers. The theoretical penetration depth could have been evaluated by comparing the apical diameters of the pluggers with the tip diameters of the preparation instruments, taking into account their respective tapers. However, the use of natural teeth made it possible to take the following two variables into consideration: ●
●
Canal anatomy: Anatomical variations (enlargements, oval root canals, etc.) are frequent and cannot be easily simulated using a linear, theoretical model. Preparation shape: The shape of the canal can vary with the technique. For example, the brushing technique accentuates the taper of
JOE — Volume 32, Number 2, February 2006
Average Plugger 1 to 4
Average EndoTwinn pluggers F to L
0.695 1.621 1.123 1.854 1.487
0.482 1.608 0.669 1.555 1.078
the canal. The diameter of the prepared canal may thus be greater than that of the last instrument used. However, by selecting straight and slightly curved canals, we did not have to contend with the difficulty of inserting a plugger into a highly curved canal. Clinical conditions were not totally reproduced because the pluggers were inserted into the canals without filling material, sealer, or gutta-percha. While the lubrifying action of the sealer may facilitate the insertion of the plugger, this is not the case for gutta-percha, which can not only slow the insertion of the plugger as it is compacted, but the gutta-percha may also get between the canal walls and the plugger. Two techniques can be used to fill canals by warm vertical compaction of gutta-percha. The classic approach, which is based on the technique first described by Schilder (1), involves softening the guttapercha using a heat carrier and then compacting it with a plugger. The two operations can also be performed simultaneously using heat pluggers (9) such as the System B (SybronEndo) and the Endotwinn (EndoTwinn). In the present study, two plugger models, one for each filling technique, were tested. Endotwinn pluggers could be inserted deeper than the finger pluggers because of their marked cylindrical taper compared to the more cylindrical shape of the finger pluggers. Yared and Bou Dagher (12) confirmed that pluggers must be inserted to within 5 to 7 mm of the apex to achieve efficient gutta-percha condensation and a tight apical seal. The smallest pluggers tested in our study (No. 1 finger and F heat) could both be inserted to this depth. Apical flaring also made it possible for larger diameter pluggers (No. 2 finger, FM, and, in certain cases, ML heat) to be inserted to within 5 to 7 mm of the apex. However, the ease of penetration of the pluggers depended on the size and taper of the preparation instruments. The M File instruments were the least effective. The smaller taper and shorter length of the active portion limited their ability to flare the canal and thus the depth to which the pluggers could penetrate. It is important to remember that in the present study only the result, that is, the shape of the preparation, was taken into consideration for comparison purposes. However, other criteria such as the strength of the Ni-Ti alloy and the cutting efficiency could have been used. Further research is warranted to study subtle differences between the four systems. To obtain a good seal, the gutta-percha master cone must be sufficiently soft to adapt perfectly to the shape of the canal walls (11). This depends on heating temperature, application time, and insertion depth (13). Smith et al. (14) showed that the heat must be applied to within 3 mm short of WL to soften the master cone and ensure good adaptation to the canal wall. This was confirmed by Bowman and Baumgartner (15). Given this, if pluggers are used in combination with a heat source, they may have to be inserted to less than 5 mm short of the WL. This would be possible after apical flaring using the group II, III, and IV techniques with the F Endotwinn plugger. However, Smith et al. (14) obtained this result using a two-step technique: heating followed by
Penetration Depth of Warm Vertical Gutta-Percha Pluggers
125
Basic Research—Technology compaction with a plugger. Heat pluggers reduce cooling of the guttapercha before compaction. In addition, with combination systems, heating is more homogeneous and can be applied simultaneously with the compaction. Compaction plays an important role. Venturi and al. showed that “a better quality of apical filling can be obtained using vertical compaction with apical back-fill” (16). Enlarging the apical third facilitates plugger penetration. However, enlarging the apical portion may compromise the integrity of the filling. Yared and Bou Dagher (11) reported that the seal is tighter when the apical portion of the canal is smaller. Apical infiltration is less common with canals prepared with No. 25 files than those prepared with No. 40 files. Wu et al. (17) also reported that the greater the width of the apical root canal, the more difficult it was to completely fill the canal with gutta-percha. To facilitate the penetration of pluggers, it is thus preferable to flare the canal while keeping the width of the apical portion to a minimum. This can be achieved using Ni-Ti instruments with large tapers. The results of the present study show that apical flaring using instruments with large tapers facilitates the penetration of warm vertical gutta-percha compaction pluggers. This type of preparation also limits the risk of apical infiltration and promotes good adaptation of the master cone to the canal walls.
Acknowledgment The authors would like to especially thank Dr. Jean Philippe Mallet for his valuable advice and comments on the manuscript.
References 1. Schilder H. Filling root canals in three dimensions. Dent Clin North Am 1967;11:723– 44.
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JOE — Volume 32, Number 2, February 2006