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Analysis of the Endogrammes Developed during Obturations on Extracted Teeth Using System B
JOURNAL OF ENDODONTICS Copyright © 2001 by The American Association of Endodontists
Printed in U.S.A. VOL. 27, NO. 11, NOVEMBER 2001
Analysis of the Endogrammes Developed during Obturations on Extracted Teeth Using System B J.-Y. Blum, DDS, PhD, C. Cathala, DDS, P. Machtou, DDS, PhD, and J.-P. Micallef, PhD
system is not compounded of a single canal but of one principal and several accessory canals (5). The use of gutta-percha allows the root canal system to be filled in three dimensions; this material, however, when used alone, cannot ensure a fluid-tight seal (6). The main property of gutta-percha, as used in endodontics, is its capacity to be softened under heating and compacted under pressure (2, 6, 7). The main difficulty for the practitioner is to determine the correct compaction forces in relationship to gutta-percha’s plasticity. The relationship between the preparation shape and the plugger is of greatest importance. With this in mind, the GT files system was developed for root canal preparation, along with a new plugger-compactor designed for a new obturation technique called System B. The Endographe is a force-analyzer device that depicts the recorded forces on Endogrammes (8). The Endogrammes not only detail normal obturations by showing the force variations, but also are able to show deficiencies and failures that are revealed on the graphs by characteristic curves. The original Endographe measures the developed forces, which may be analyzed into horizontal and vertical forces (8). A recent modification in the Endographe’s tooth-holder, however, now also allows access to the horizontal intracanal forces that have been labeled the wedging effect (9, 10). The aim of the present study was to analyze the System B technique by measuring the forces applied by the practitioners involved in the study and the resulting wedging effect.
The ability of an obturation technique to fill the root canal system tridimensionally depends partially on the timing and intensity of force applications. The aim of this study was to use the Endographe to analyze the forces and wedging effects developed in the root canal using a new obturation technique: System B. This system uses a heat plugger that simultaneously heats and pushes gutta-percha. The plugger was used to soften and move the gutta-percha apically during the down-pack stage. Two different methods, however, were used to withdraw the plugger from the compacted guttapercha. One used the burst heat method, and the other was cold withdrawal. Five endodontists performed 50 obturations of prepared extracted teeth and 50 obturations of the “wedging effect” holder of the Endographe. The practitioner-obturation assignment was randomized. For each obturation the biggest plugger possible in relationship to the shape of the canal was chosen. For the obturation of the special holder the same tip was chosen. Endogrammes showed the force application and wedging effect sequences. The mean values for the vertical and horizontal forces and the wedging effect were, respectively, 16 ⴞ 2 N, 5 ⴞ 1 N, and 9 ⴞ 1 N. These results suggest that System B is one of the best techniques in terms of the developed vertical forces (low values) and the resulting wedging effect (high values) in relationship to the plasticity of the gutta-percha. The Endogrammes provide a new approach to the analysis of obturation techniques and a means to demonstrate correct and optimal manipulation of the new System B plugger.
MATERIALS AND METHODS The computerized recording system was developed in collaboration with INSERM, XR 103, of Montpellier, France (8, 9). The main components are three force transducers (Captels, St. Mathieu de Treviers, France), electronic amplifiers, analogue-to-digital converters, a PC-compatible computer, and Endopro software (Martens and Garcia, Montpellier, France). The evaluation device is composed of the two perpendicularly linked transducers for the measurement of extracanal forces (8, 9). A new tooth-holder, with a transducer fixed on one of its parts, was connected and fixed in place instead of the original. In this version the tooth-holder itself reproduces a root canal. With this design modification wedging effect can be measured (9). Because the device records obturation forces as a function of time, the duration of obturations can be stored. In the present study start time was determined as the first compaction, and finish time as the last. The three sensors were connected to the data acquisition software, from which the stored
Gutta-percha is currently used for several obturation techniques, such as lateral condensation (1), warm vertical compaction (2), thermomechanical compaction (3), and Thermafil condensation (4). The aim of all these techniques is to achieve a fluid-tight seal of the root canal system to prevent periapical infection. For all of them the greatest problem for the practitioner is that the root canal 661
662
Blum et al.
Journal of Endodontics
FIG. 1. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the different forces. (TH) Touch ’n Heat plugger. Note the different phases (A to E).
data were transferred to an EXCEL spreadsheet (Microsoft Corp., Seattle, WA) and then converted into graphs. Data were accessible on-line or off-line. The entire assembly is labeled the Endographe (8, 9). The main advantage of the System B concept lies in the fact that the Buchanan pluggers and master cones have a shape that closely approximates the root canal preparation (11). Until today, because of a lack of adequate analyzers, no data have been reported on System B in terms of developed forces or the resulting wedging effect. The System B technique heat source continuously monitors the temperature at the tip of the heat-pluggers and maintains a stable temperature throughout the downpack. Protocol Canal instrumentation was performed by five endodontists. Each performed 10 preparations with the balanced-force technique using Gates Glidden burs (Maillefer, Ballaigues, Switzerland) for the coronal part of the canal, NiTI files (Maillefer, Ballaigues, Switzerland) for the body of the canal, and GT files (Dentsply Tulsa Dental, Tulsa, OK) for the apical part of the canal. The Gates Glidden burs were fixed on a W&H WD-72 M handpiece with a 1:20 reductor speed head (W & H, Strasbourg, France) and worked by an implantology surgical unit (Friatec, Mannheim, Germany). The rotation speed was fixed at 2000 rpm. In all 50 canals the apical constriction was left intact and the cone was then fitted to full length before a minimal cutback (less than 0.5 mm). System B was used as described by Machtou and Amor (11): a System B plugger was then chosen to match the taper of the gutta-percha point, and a silicone stop was placed on the plugger. The stop was set at the reference point (5 to 7 mm short of full canal length). The canal was dried and the cone was cemented into the canal. The System B heat temperature was set to 200°C and the power at 10. Then the different stages of the method were successively implemented as follows: • Phase A: The cone was seared off at the orifice with the tip of the preheated Buchanan plugger. At this stage the cold Buchanan hand plugger was used to compact the cone at the orifice level.
• Phase B: While depressing the spring to generate heat, the plugger was smoothly driven through the gutta-percha to within 3 to 4 mm of the binding point. • Phase C: At this time, just shy of the binding point, the finger pressure was released. The plugger cooled and slowed its apical movement and stopped just short of the binding point. • Phase D: A vertical force was applied for 10 s to sustain the push. • Phase E: For the heat burst method the practitioner depressed the spring again for 1 s while maintaining apical pressure. The spring was then released, a pause was observed for 1 s, then the plugger was rapidly withdrawn. The heat burst in this portion of the procedure causes rapid severance between the apical part of the gutta-percha (7 mm) and the part of the gutta-percha stuck to the plugger. For cold withdrawal the plugger handle was swiveled back and forth, which caused the plugger to withdraw.
RESULTS Different Endogrammes were obtained for the different phases of this obturation technique (Figs. 1 to 5). A two-way ANOVA was performed using resolution forces (at two levels) and practitioners (at five levels). Significance was fixed at p ⬍ 0.05. When the ANOVA F was significant, a contrast method was applied. The mean values (⫾SEM) were 16 ⫾ 3 N for the vertical forces and 4 ⫾ 1 N for the horizontal forces. For the wedging effect experiments the mean values (⫾SEM) were 7.5 ⫾ 1 N. For all obturations the mean duration was 12 ⫾ 2 s. The Endogrammes were analyzed to show the chronology of force appearances (Figs. 1 to 5). For the final phase of this technique the Endographe generated different Endogrammes (Figs. 1 to 5) that were analyzed in the discussion.
DISCUSSION The aim of this study was to analyze the extra- and intracanal forces developed during a new obturation technique, System B,
Vol. 27, No. 11, November 2001
Obturations Using System B
663
FIG. 2. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the different forces. (H) Coronal push with Buchanan plugger. Note the different phases (A to E).
FIG. 3. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the different forces. Note the different phases (B to E). The transition phase C is particularly evident on this Endogramme.
using the Endographe. After measurement by force transducers, Endogrammes were plotted to show the forces, wedging effects, and obturation durations specific to this technique. The first analysis was a qualitative analysis. The different phases of this technique, as described by Buchanan, appeared on the Endogrammes (Figs. 1 to 4) and are as follows: • Phase A began by heating the gutta-percha either with the tip of the Touch ’n Heat (Fig. 1, TH) or with the tip of the Buchanan plugger (Fig. 2, H). Then with the cold Buchanan plugger, the cone was compacted at the orifice level (Figs. 1A and 2A). During this phase the developed forces had a mean value of 8 ⫾ 2 N. This indicates that the role of these forces is to adapt the cone to the walls of the root canal system in the coronal aspect of the shaped canal. In no case during the following steps was the cone withdrawn. • During phase B the operator depressed the spring to heat the
plugger, and the heated plugger was smoothly driven through the gutta-percha to within 3 to 4 mm of the binding point (Figs. 1B, 2B, and 3B). The vertical forces increased during this phase. The cone was pushed against the wall, preparing for the following phase. At this point the wedging effect was low, indicating that the main forces are vertical with apical progression of the cone (Fig. 4). • At phase C the finger pressure was released (Fig. 1C) and the heat source was cut off. The plugger slowed its apical movement and stopped just short of the binding point (Fig. 2C). During this phase the vertical forces increased even though the cone was stopped in its apical progression. The wedging forces increased but did not reach maximal values (Fig. 4). This was due to the change in hand position during the transition from phase B through to phase D. This stage should be as brief as possible to prevent any withdrawal of the cone during the down-pack phase.
664
Blum et al.
Journal of Endodontics
FIG. 4. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the vertical forces in relationship to the wedging effect. Note the nonsynchronous appearance of the vertical forces and the wedging effect.
FIG. 5. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the different forces. Note the different phases (A to E). The two types of deinsertion of the Buchanan plugger are observable. E burst: withdrawal with the burst movement. E rotation: withdrawal with rotation of the cold Buchanan plugger.
• In phase D a vertical force was applied for 10 s to sustain the push (Fig. 1D). The gutta-percha cooling must occur under pressure to avoid any shrinkage (2) (Fig. 2D). System B allows the practitioner to push the gutta-percha during cooling with enough force to prevent this shrinkage. During this stage the wedging effect reached its maximal value. The time lag between the beginning of pushing and the resulting wedging effect throughout the canal is explained by the transmission of forces from a vertical axis (vertical forces) to a horizontal axis (wedging effect) (8, 9) (Fig. 4). • For phase E two different methods were used (Fig. 5). With the heat burst method the plugger was rapidly withdrawn with the delivery of a burst of high heat (Fig. 5 E, burst). In the second method the plugger handle was swiveled back and forth to withdraw the plugger (Fig. 4 E, rotation). The Endogrammes stored these two types of withdrawal, which differed in terms of developed forces. The forces and wedging effects developed by different methods of obturation were compared by Blum et al. (8, 9). The values showed that the greatest wedging effect occurred during lateral compaction (6.5 (⫾ 0.7) N for warm vertical compaction, 8 (⫾ 1) N for lateral compaction, 6 (⫾0.8) N for thermomechanical compaction, and 0.3 (⫾0.1) N for Thermafil compaction). Value was not significantly different from that obtained with System B was 7.5 (⫾1) N. Because of the different working temperatures the gutta-percha cones had different plasticities during lateral compac-
tion, System B and warm vertical compaction, and thus different microadaptations to the wall of the canal. These slight differences will have different repercussions on the wedging of the guttapercha and the sealer, and thus for the tridimensional obturation capability of the technique (7). The Endogrammes of the other obturation techniques revealed that the wedging effect was relatively constant during obturation by warm vertical compaction (8). This result confirmed the importance of the softened gutta-percha wave during the down-pack (6). For System B the wedging effect was highest during phase E, demonstrating the importance of prefitting the plugger for this technique. After heating with the plugger the adaptation of guttapercha to the wall of the canal is of critical importance to obtain the wedging effect and thus the tridimensional obturation described by Schilder (2). These observations support the contention that preparation of the root canal system, and especially the deep shaping of the preparation, is the most important step to ensure a complete tridimensional obturation (2, 6, 12). As reported by Hatton et al. (13) a condensation pressure of 10 N for the lateral compaction technique seems to be enough to ensure an adequate apical seal. Their experiments, however, were based only on the penetration of methylene blue dye into the main canal to assess sealing. For the endodontist, on the other hand, the overriding challenge is to perform a tridimensional obturation of the entire root canal system, accessory canals included, and not only the main canal. Thus the main advantage of the Endographe—
Vol. 27, No. 11, November 2001
Obturations Using System B
more than its usefulness to analyze the quality of the apical seal—is that it can capture all the hand movements of the best endodontists as they perform tridimensional obturations. Because the heated plugger of System B is adjusted closely to the shape of the canal, the wedging effect is applied with a minimum of space between the plugger, the gutta-percha cone, and the wall of the canal. System B seems to be a very interesting technique because of the high wedging effect that is produced. Although the time of manipulation is very short (20 s) the Endographe allowed an analysis of the movement and its analysis into elementary steps. This greatly facilitates our understanding of the technique and will be useful for optimizing the use of the System B plugger.
References
The authors wish to thank Frantz Martens and Augustin Garcia for the use of their Endopro acquisition software and Catherine Stott Carmeni for technical assistance. Dr. Blum is affiliated with the CHU of Montpellier, Montpellier, France. Dr. Cathala is currently in private practice in Montagnac, France. Dr. Machtou is professor, School of Dentistry, Paris VII University, Paris, France. Dr. Micallef is a senior research scientist at the INSERM, Montpellier, France. Address requests for reprints to Dr. Jean-Yves Blum, rue Eyminy, 30800 St. Gilles, France.
665
1. Ingle JI, Beveridge EE. Endodontics. 2nd ed. Philadelphia: Lea & Febiger, 1976. 2. Schilder H. Filling the root canal in three dimensions. Dent Clin North Am 1974;11:723– 44. 3. MacSpadden JT. Self study course of the thermal condensation of gutta percha. Form no. 8 337 V.S., 1980:80 –90. 4. Johnson W. A new gutta-percha technique. J Endodon 1978;4:184 – 8. 5. Dedeus QD. Frequency, localization and direction of the lateral, secondary and accessory canals. J Endodon 1975;1:361– 6. 6. Machtou P. L’obturation du syste`me canalaire. In: Machtou endodontie. Paris: CDP, 1993. 7. Camps JJ, Pertot WJ, Escavy JY, Pravaz M. Young’s modulus of warm and cold gutta-percha. Endod Dent Traumatol 1996;12:50 –3. 8. Blum JY, Esber S, Micallef JP. Analysis of forces developed during obturations: comparison of three techniques. J Endodon 1997;5:340 –5. 9. Blum JY, Machtou P, Micallef JP. Analysis of forces developed during obturations: wedging effect. Part I. J Endodon 1998;4:217–22. 10. Blum JY, Machtou P, Micallef JP. Analysis of forces developed during obturations: wedging effect. Part II. J Endodon 1998;4:223–30. 11. Machtou P, Amor J. The System B. Endo 1999;1:34 –7. 12. Buchanan LS. Cleaning and shaping the root canal system. In: Cohen S, Burns RC, eds. Pathways of the pulp. 5th ed. St. Louis: CV Mosby, 1991:273–324. 13. Hatton JF, Ferrillo PJ, Wagner G, Stewart GP. The effect of condensation pressure on the apical seal. J Endodon 1988;14:305– 8.
Printed in U.S.A. VOL. 27, NO. 11, NOVEMBER 2001
Analysis of the Endogrammes Developed during Obturations on Extracted Teeth Using System B J.-Y. Blum, DDS, PhD, C. Cathala, DDS, P. Machtou, DDS, PhD, and J.-P. Micallef, PhD
system is not compounded of a single canal but of one principal and several accessory canals (5). The use of gutta-percha allows the root canal system to be filled in three dimensions; this material, however, when used alone, cannot ensure a fluid-tight seal (6). The main property of gutta-percha, as used in endodontics, is its capacity to be softened under heating and compacted under pressure (2, 6, 7). The main difficulty for the practitioner is to determine the correct compaction forces in relationship to gutta-percha’s plasticity. The relationship between the preparation shape and the plugger is of greatest importance. With this in mind, the GT files system was developed for root canal preparation, along with a new plugger-compactor designed for a new obturation technique called System B. The Endographe is a force-analyzer device that depicts the recorded forces on Endogrammes (8). The Endogrammes not only detail normal obturations by showing the force variations, but also are able to show deficiencies and failures that are revealed on the graphs by characteristic curves. The original Endographe measures the developed forces, which may be analyzed into horizontal and vertical forces (8). A recent modification in the Endographe’s tooth-holder, however, now also allows access to the horizontal intracanal forces that have been labeled the wedging effect (9, 10). The aim of the present study was to analyze the System B technique by measuring the forces applied by the practitioners involved in the study and the resulting wedging effect.
The ability of an obturation technique to fill the root canal system tridimensionally depends partially on the timing and intensity of force applications. The aim of this study was to use the Endographe to analyze the forces and wedging effects developed in the root canal using a new obturation technique: System B. This system uses a heat plugger that simultaneously heats and pushes gutta-percha. The plugger was used to soften and move the gutta-percha apically during the down-pack stage. Two different methods, however, were used to withdraw the plugger from the compacted guttapercha. One used the burst heat method, and the other was cold withdrawal. Five endodontists performed 50 obturations of prepared extracted teeth and 50 obturations of the “wedging effect” holder of the Endographe. The practitioner-obturation assignment was randomized. For each obturation the biggest plugger possible in relationship to the shape of the canal was chosen. For the obturation of the special holder the same tip was chosen. Endogrammes showed the force application and wedging effect sequences. The mean values for the vertical and horizontal forces and the wedging effect were, respectively, 16 ⴞ 2 N, 5 ⴞ 1 N, and 9 ⴞ 1 N. These results suggest that System B is one of the best techniques in terms of the developed vertical forces (low values) and the resulting wedging effect (high values) in relationship to the plasticity of the gutta-percha. The Endogrammes provide a new approach to the analysis of obturation techniques and a means to demonstrate correct and optimal manipulation of the new System B plugger.
MATERIALS AND METHODS The computerized recording system was developed in collaboration with INSERM, XR 103, of Montpellier, France (8, 9). The main components are three force transducers (Captels, St. Mathieu de Treviers, France), electronic amplifiers, analogue-to-digital converters, a PC-compatible computer, and Endopro software (Martens and Garcia, Montpellier, France). The evaluation device is composed of the two perpendicularly linked transducers for the measurement of extracanal forces (8, 9). A new tooth-holder, with a transducer fixed on one of its parts, was connected and fixed in place instead of the original. In this version the tooth-holder itself reproduces a root canal. With this design modification wedging effect can be measured (9). Because the device records obturation forces as a function of time, the duration of obturations can be stored. In the present study start time was determined as the first compaction, and finish time as the last. The three sensors were connected to the data acquisition software, from which the stored
Gutta-percha is currently used for several obturation techniques, such as lateral condensation (1), warm vertical compaction (2), thermomechanical compaction (3), and Thermafil condensation (4). The aim of all these techniques is to achieve a fluid-tight seal of the root canal system to prevent periapical infection. For all of them the greatest problem for the practitioner is that the root canal 661
662
Blum et al.
Journal of Endodontics
FIG. 1. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the different forces. (TH) Touch ’n Heat plugger. Note the different phases (A to E).
data were transferred to an EXCEL spreadsheet (Microsoft Corp., Seattle, WA) and then converted into graphs. Data were accessible on-line or off-line. The entire assembly is labeled the Endographe (8, 9). The main advantage of the System B concept lies in the fact that the Buchanan pluggers and master cones have a shape that closely approximates the root canal preparation (11). Until today, because of a lack of adequate analyzers, no data have been reported on System B in terms of developed forces or the resulting wedging effect. The System B technique heat source continuously monitors the temperature at the tip of the heat-pluggers and maintains a stable temperature throughout the downpack. Protocol Canal instrumentation was performed by five endodontists. Each performed 10 preparations with the balanced-force technique using Gates Glidden burs (Maillefer, Ballaigues, Switzerland) for the coronal part of the canal, NiTI files (Maillefer, Ballaigues, Switzerland) for the body of the canal, and GT files (Dentsply Tulsa Dental, Tulsa, OK) for the apical part of the canal. The Gates Glidden burs were fixed on a W&H WD-72 M handpiece with a 1:20 reductor speed head (W & H, Strasbourg, France) and worked by an implantology surgical unit (Friatec, Mannheim, Germany). The rotation speed was fixed at 2000 rpm. In all 50 canals the apical constriction was left intact and the cone was then fitted to full length before a minimal cutback (less than 0.5 mm). System B was used as described by Machtou and Amor (11): a System B plugger was then chosen to match the taper of the gutta-percha point, and a silicone stop was placed on the plugger. The stop was set at the reference point (5 to 7 mm short of full canal length). The canal was dried and the cone was cemented into the canal. The System B heat temperature was set to 200°C and the power at 10. Then the different stages of the method were successively implemented as follows: • Phase A: The cone was seared off at the orifice with the tip of the preheated Buchanan plugger. At this stage the cold Buchanan hand plugger was used to compact the cone at the orifice level.
• Phase B: While depressing the spring to generate heat, the plugger was smoothly driven through the gutta-percha to within 3 to 4 mm of the binding point. • Phase C: At this time, just shy of the binding point, the finger pressure was released. The plugger cooled and slowed its apical movement and stopped just short of the binding point. • Phase D: A vertical force was applied for 10 s to sustain the push. • Phase E: For the heat burst method the practitioner depressed the spring again for 1 s while maintaining apical pressure. The spring was then released, a pause was observed for 1 s, then the plugger was rapidly withdrawn. The heat burst in this portion of the procedure causes rapid severance between the apical part of the gutta-percha (7 mm) and the part of the gutta-percha stuck to the plugger. For cold withdrawal the plugger handle was swiveled back and forth, which caused the plugger to withdraw.
RESULTS Different Endogrammes were obtained for the different phases of this obturation technique (Figs. 1 to 5). A two-way ANOVA was performed using resolution forces (at two levels) and practitioners (at five levels). Significance was fixed at p ⬍ 0.05. When the ANOVA F was significant, a contrast method was applied. The mean values (⫾SEM) were 16 ⫾ 3 N for the vertical forces and 4 ⫾ 1 N for the horizontal forces. For the wedging effect experiments the mean values (⫾SEM) were 7.5 ⫾ 1 N. For all obturations the mean duration was 12 ⫾ 2 s. The Endogrammes were analyzed to show the chronology of force appearances (Figs. 1 to 5). For the final phase of this technique the Endographe generated different Endogrammes (Figs. 1 to 5) that were analyzed in the discussion.
DISCUSSION The aim of this study was to analyze the extra- and intracanal forces developed during a new obturation technique, System B,
Vol. 27, No. 11, November 2001
Obturations Using System B
663
FIG. 2. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the different forces. (H) Coronal push with Buchanan plugger. Note the different phases (A to E).
FIG. 3. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the different forces. Note the different phases (B to E). The transition phase C is particularly evident on this Endogramme.
using the Endographe. After measurement by force transducers, Endogrammes were plotted to show the forces, wedging effects, and obturation durations specific to this technique. The first analysis was a qualitative analysis. The different phases of this technique, as described by Buchanan, appeared on the Endogrammes (Figs. 1 to 4) and are as follows: • Phase A began by heating the gutta-percha either with the tip of the Touch ’n Heat (Fig. 1, TH) or with the tip of the Buchanan plugger (Fig. 2, H). Then with the cold Buchanan plugger, the cone was compacted at the orifice level (Figs. 1A and 2A). During this phase the developed forces had a mean value of 8 ⫾ 2 N. This indicates that the role of these forces is to adapt the cone to the walls of the root canal system in the coronal aspect of the shaped canal. In no case during the following steps was the cone withdrawn. • During phase B the operator depressed the spring to heat the
plugger, and the heated plugger was smoothly driven through the gutta-percha to within 3 to 4 mm of the binding point (Figs. 1B, 2B, and 3B). The vertical forces increased during this phase. The cone was pushed against the wall, preparing for the following phase. At this point the wedging effect was low, indicating that the main forces are vertical with apical progression of the cone (Fig. 4). • At phase C the finger pressure was released (Fig. 1C) and the heat source was cut off. The plugger slowed its apical movement and stopped just short of the binding point (Fig. 2C). During this phase the vertical forces increased even though the cone was stopped in its apical progression. The wedging forces increased but did not reach maximal values (Fig. 4). This was due to the change in hand position during the transition from phase B through to phase D. This stage should be as brief as possible to prevent any withdrawal of the cone during the down-pack phase.
664
Blum et al.
Journal of Endodontics
FIG. 4. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the vertical forces in relationship to the wedging effect. Note the nonsynchronous appearance of the vertical forces and the wedging effect.
FIG. 5. Endogramme generated by the System B obturation. Line represents the gauge tracing over time and shows the appearance of the different forces. Note the different phases (A to E). The two types of deinsertion of the Buchanan plugger are observable. E burst: withdrawal with the burst movement. E rotation: withdrawal with rotation of the cold Buchanan plugger.
• In phase D a vertical force was applied for 10 s to sustain the push (Fig. 1D). The gutta-percha cooling must occur under pressure to avoid any shrinkage (2) (Fig. 2D). System B allows the practitioner to push the gutta-percha during cooling with enough force to prevent this shrinkage. During this stage the wedging effect reached its maximal value. The time lag between the beginning of pushing and the resulting wedging effect throughout the canal is explained by the transmission of forces from a vertical axis (vertical forces) to a horizontal axis (wedging effect) (8, 9) (Fig. 4). • For phase E two different methods were used (Fig. 5). With the heat burst method the plugger was rapidly withdrawn with the delivery of a burst of high heat (Fig. 5 E, burst). In the second method the plugger handle was swiveled back and forth to withdraw the plugger (Fig. 4 E, rotation). The Endogrammes stored these two types of withdrawal, which differed in terms of developed forces. The forces and wedging effects developed by different methods of obturation were compared by Blum et al. (8, 9). The values showed that the greatest wedging effect occurred during lateral compaction (6.5 (⫾ 0.7) N for warm vertical compaction, 8 (⫾ 1) N for lateral compaction, 6 (⫾0.8) N for thermomechanical compaction, and 0.3 (⫾0.1) N for Thermafil compaction). Value was not significantly different from that obtained with System B was 7.5 (⫾1) N. Because of the different working temperatures the gutta-percha cones had different plasticities during lateral compac-
tion, System B and warm vertical compaction, and thus different microadaptations to the wall of the canal. These slight differences will have different repercussions on the wedging of the guttapercha and the sealer, and thus for the tridimensional obturation capability of the technique (7). The Endogrammes of the other obturation techniques revealed that the wedging effect was relatively constant during obturation by warm vertical compaction (8). This result confirmed the importance of the softened gutta-percha wave during the down-pack (6). For System B the wedging effect was highest during phase E, demonstrating the importance of prefitting the plugger for this technique. After heating with the plugger the adaptation of guttapercha to the wall of the canal is of critical importance to obtain the wedging effect and thus the tridimensional obturation described by Schilder (2). These observations support the contention that preparation of the root canal system, and especially the deep shaping of the preparation, is the most important step to ensure a complete tridimensional obturation (2, 6, 12). As reported by Hatton et al. (13) a condensation pressure of 10 N for the lateral compaction technique seems to be enough to ensure an adequate apical seal. Their experiments, however, were based only on the penetration of methylene blue dye into the main canal to assess sealing. For the endodontist, on the other hand, the overriding challenge is to perform a tridimensional obturation of the entire root canal system, accessory canals included, and not only the main canal. Thus the main advantage of the Endographe—
Vol. 27, No. 11, November 2001
Obturations Using System B
more than its usefulness to analyze the quality of the apical seal—is that it can capture all the hand movements of the best endodontists as they perform tridimensional obturations. Because the heated plugger of System B is adjusted closely to the shape of the canal, the wedging effect is applied with a minimum of space between the plugger, the gutta-percha cone, and the wall of the canal. System B seems to be a very interesting technique because of the high wedging effect that is produced. Although the time of manipulation is very short (20 s) the Endographe allowed an analysis of the movement and its analysis into elementary steps. This greatly facilitates our understanding of the technique and will be useful for optimizing the use of the System B plugger.
References
The authors wish to thank Frantz Martens and Augustin Garcia for the use of their Endopro acquisition software and Catherine Stott Carmeni for technical assistance. Dr. Blum is affiliated with the CHU of Montpellier, Montpellier, France. Dr. Cathala is currently in private practice in Montagnac, France. Dr. Machtou is professor, School of Dentistry, Paris VII University, Paris, France. Dr. Micallef is a senior research scientist at the INSERM, Montpellier, France. Address requests for reprints to Dr. Jean-Yves Blum, rue Eyminy, 30800 St. Gilles, France.
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