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An evaluation of the number of condenser insertions needed with warm lateral condensation of guttapercha
0099-2399/93/1902-0079/$03.00/0 Printed in U.S.A. VOL. 19, NO. 2, FEBRUARY1993
JOURNAL OF ENDODONTICS
Copyright © 1993 by The American Association of Endodontists
An Evaluation of the Number of Condenser Insertions Needed with Warm Lateral Condensation of Guttapercha Van T. Himel, DDS, and Christopher W. Cain, DDS
lateral canals and foramina. This method uses a modified canal preparation, sequential placement of gutta-percha, and heated instruments to vertically compact the gutta-percha. The warm lateral condensation technique arose as a combination of the two previous techniques. It attempts to combine the advantages of cold lateral and warm vertical techniques to produce a homogenous mass of gutta-percha with adaptation to canal walls and fewer voids (9).
The purpose of this investigation was to determine the number of condenser insertions needed to obturate root canal systems using warm lateral condensation. Forty epoxide blocks with one major and five lateral canals placed at varying angles were used. The blocks received either one, three, five, or seven insertions of the warm instrument. The findings revealed gutta-percha and or sealer in every lateral canal. Cold compaction of the heated guttapercha produced more material in the lateral canals than did the use of the heated condenser alone. The optimum number of condenser insertions depended upon the position of the lateral canal, the size of the canal, and the bulk of material being heated. The areas of the main canal with a smaller diameter required fewer insertions of the warm condenser to push the gutta-percha into the lateral canals located in those areas.
MATERIALS AND METHODS Forty clear epoxide blocks (Kilgore Int'l Inc., Coldwater, MI) with five lateral canals, labeled A through E, placed at varying angles were used for this study. Each block was manufactured to the specifications of a #50 instrumented main canal. Dimensions and the placement of the lateral canals are noted in Fig. 1. All lateral canals were of equal dimensions. The patency of all lateral canals were evaluated by the placement of a # 10 K-type file through the side of the 1.5era
According to Schilder, "the final objective of endodontic procedures is the total three dimensional filling of the root canal system" (1). Various techniques and materials have been used in an attempt to achieve this goal (1-4). Most currently used filling techniques employ either a solid core and cementing substance or a material which can be adapted to the shape of the root canal system (1, 5). Gutta-percha is now the filling material of choice because of its biological and mechanical properties (6-8). Several gutta-percha techniques have been used in an attempt to achieve a void-free, homogeneous filling. While advances have been made in alternate obturation techniques, the cold lateral condensation technique is still one of the most frequently used techniques today. One stated disadvantage of cold lateral condensation is that at no time is a homogenous mass of gutta-percha developed (1). The final filling is composed of a large number of gutta-percha cones tightly pressed together and joined by frictional grip and cementing substance. Warm vertical condensation of gutta-percha is claimed by Schilder (1) to provide a greater density of gutta-percha at the apical portion of the filling and to consistently obturate
T
2 . 0 c~
O.l~
E ~
/ A
.,,,.
I
'
T
B
FIG 1. Epoxide block with a main canal and five lateral canals labeled AtoE. 79
80
Journal of Endodontics
Himel and Cain
lateral canal into the main canal. Working lengths of the main canals were established by inserting a #50 K-type file into the canals. The length from the canal apex to the coronal orifice was measured. The blocks were covered with foil and tape to prevent visual inspection during obturation. They were then numbered and randomly divided into four groups. The groups were differentiated by the number of Endotec condenser (Caulk/Dentsply, Milford, DE) insertions used during obturation: group 1, one Endotec insertion at 12 s each; group 2, three Endotec insertions at 12 s each; group 3, five Endotec insertions at 12 s each; and group 4, seven Endotec insertions at 12 s each. To ensure consistency, the four groups were treated by a clinician with experience using this obturation technique. Each block was fitted with a #50 master apical cone seated to the working length. Roth's 801 elite grade sealer (Roth Drug Co., Chicago, IL) was mixed according to the manufacturer's recommendation and placed into the canal with a #30 K-type file. The apical third of the file was coated with sealer, inserted into the canal at working length, and rotated in a counterclockwise direction to coat the canal walls. The master apical cone, with sealer placed on the apical one third, was inserted to the working length. A cold condenser was inserted followed by a #20 accessory cone to within 1 m m of working length prior to the insertion of the Endotec. The accessory cone provided additional bulk of gutta-percha in the apical third and is a technique suggested by the manufacturer. The Endotec condenser was placed into the canal until resistance was met and then the heat activator button was depressed for 12 s. The tip was pressed in an apical direction with a lateral and circumferential rotary motion to a depth of 2 m m from the working length. After the 12-s interval the heat activator was released and the tip of the heated instrument was removed. A #20 accessory point was then placed into the prepared space. This process was repeated as prescribed for each group. Cold lateral condensation of additional accessory cones was used to complete obturation after the specified number of warm condenser insertions per group was completed. Number 25 accessory cones were used in the coronal half of the canal. The blocks were back filled to within 4 m m of the orifice. Upon completion of obturation, each block was stored for a m i n i m u m of 7 days at room temperature and 100% humidity. The foil was removed from each clear block and the lateral canals microscopically evaluated with a Meiji EMT microscope at x l0 magnification. The length of filling material, either sealer or gutta-percha, extruded into the lateral canals from the main canal was measured in 0.5-mm increments. The data obtained were statistically analyzed using a one-way analysis of variance (ANOVA). The groups were shown to be statistically different at the p<0.05 level of significance.
The total length of gutta-percha found in all lateral canals increased with additional use of the warm condenser, up to five insertions. The greatest increase occurred between one and three insertions, with no statistical difference (ANOVA, p<0.05) between five and seven insertions (Fig. 3). When the lateral canals were evaluated individually, a difference was noted. Canal A, the most apical canal, had less gutta-percha with increased use of the warm condenser while all other canals tended to have more gutta-percha with increased use (Fig. 4). DISCUSSION The choice of sealer seems to affect the ease of manipulating gutta-percha when using warm lateral condensation. During the process of obturation, the zinc oxide and eugenol sealer had a tendency to become sticky, causing the gutta-percha and sealer to adhere to the warm instrument. This made obturation of the root canal system and cleaning of the
M E A N G u ' r r A - P E R C H A AND S E A L E R 8
FIVE INSERTIONS I SEVEN INSER'I3ONSJ
6
=
4
I
2
0
A
B
C
D
E
CANALS
FIG 2. Graph representing the mean length of filling with gutta-percha and sealer in each lateral canal. A statistical difference (ANOVA,
p<0.05) was noted in group D (1D to 3D, 3D to 5D), and group E (1E to 3E, 1E to 5E). I I P
i
|I
~ I
I
~
•
R P R h I
•
I
o ntu Q. <
o 11
O
RESULTS 0
The obturation produced either gutta-percha and/or sealer in all lateral canals (Fig. 2). The most consistent results were found in canals A and B when gutta-percha and/or sealer were measured. Lateral canals C, D, and E were not as consistent. Sealer was in all lateral canals and always preceded gutta-percha regardless of the number of warm condenser insertions.
1
3
5
7
N u m b e r of Insertions
FIG 3. Graph showing the mean gutta-percha (mm) in all lateral canals for each group of insertions. A statistical difference (ANOVA, p<0.05) was noted between insertions 1 to 3, 5, and 7 and insertions 3-1, 5, and 7. Five and seven insertions were not statistically different. No gutta-percha was found in groups A5 or El.
Warm Lateral Condensation
Vol. 19, No. 2, February 1993
MEAN GUTTA-PERCHA 1.S- IN LATERAL CANALS
(I ONEr~ER'nON [i nEE,NSER'rDNSI FIVE INSERTIONS I SEVEN INSERTIONS,,~
A
B
C
D
E
CANALS FIG 4. Graph illustrating the mean gutta-percha in each lateral canal as labeled A to E. A statistical difference (ANOVA, p<0.05) was noted in group A (1-5, 1-7), group C (1-5, 1-7), group D (1-3, 1-5, 1-7, 3-5, 3-7), and group E (1-3, 1-5, 1-7).
instrument difficult. The problem was overcome using alcohol wipes to clean sealer from the instrument. In a follow-up pilot study, the authors used a different sealer which decreased in viscosity with heat, resulting in increased flow properties. The use of the second sealer (AH26; De Trey/Dentsply, Milford, DE) would seem to overcome the problem of material sticking to the instrument. Warm lateral condensation was effective in the obturation of artificial canals as all lateral canals contained either guttapercha and/or sealer. The irregular positioning and the small size of these lateral canals seem to indicate that this technique would fill root canal irregularities such as fenestrations in as equally an effective manner. The use of a file to place sealer into these relatively large curved canals seemed to be an effective method as sealer was always seen in advance of the gutta-percha. The technique of sealer placement and the amount inserted could be as critical a factor to its movement as the obturation technique and is an area in need of additional research. The number of insertions of the warm spreader did not seem to have a consistent effect on the material in canals when sealer was combined with gutta-percha. Canals with less gutta-percha tended to have more sealer while canals with more more gutta-percha had less sealer. This could be due to the displacement of sealer by the gutta-percha or by the inhibition of gutta-percha movement by the sealer. Such displacement is desirable unless gutta-percha is pushed into the periapical tissues in large quantities and/or into critical anatomical structures such as the mandibular canal. As Luccy et al. (9) have suggested, an ideal temperature may exist which would allow for the production of an optimal homogeneous mass of gutta-percha. This ideal temperature may also help the clinician restrict the flow of filling materials to canal systems avoiding periapical inflammatory responses. Schilder has stated (8) that less change in volume occurs upon cooling when lower temperatures are used. Any technique which uses heat above 45°C predisposes to shrinkage of the gutta-percha and requires compaction (8). Being able to accurately control the temperature could possibly help the clinician control the direction and amount of gutta-percha flow. When gutta-percha alone was analyzed, a definite relationship was noticed between gutta-percha and the number of
81
condenser insertions. Figure 3 shows the results when guttapercha was totaled in all lateral canals. It would seem that statistically (ANOVA, p<0.05) more movement of material occurred with increased insertions of the warm condenser up to five insertions. Differences were observed when the canals were evaluated individually (Fig. 4). The size of the canal, the bulk of material in the main canal, the orientation of lateral canal to main canal, and the compaction of cooling gutta-percha with a cold spreader represent possible causes of these differences. Additional insertions of the heated condenser caused an increased movement of gutta-percha in all canals except in A, the most apical canal (Fig. 1). This apical position made it the only canal which would require more of a vertical than a lateral vector of force to be placed on the filling material. In the single insertion group, the warm instrument was placed to within 2 m m of the working length and a cold spreader inserted into the heated mass. This spreader compacted the cooling material, pushing it farther into canal A than the multiple insertion groups in which the cold spreader was not used in the more apical portions of the main canal. When the heated spreader was used three or more times before a cold spreader was used, less vertical movement of gutta-percha occurred. Canal B was in a position to receive both vertical and horizontal forces. Canals C, D, and E were positioned so that more gutta-percha flowed into them as a result of the lateral forces. More insertions were necessary for heating the greater mass of gutta-percha as the main canal became wider in the more coronal sections. The larger diameter made movement of gutta-percha into lateral canals more difficult than in the narrower, more apical portions of the canal. With a large mass of gutta-percha present, the heated condenser was unable to thermoplasticize the gutta-percha on the periphery of the canal walls as efficiently as in the more apical portion containing a smaller mass of material. The lateral forces exerted by the condenser are dissipated over a larger diameter and are therefore less effective in forcing gutta-percha into these lateral canals. Increased numbers of insertions were necessary to overcome these problems. The cold spreader pushed the heated gutta-percha laterally during the cooling phase. This would seem to be in agreement with Schilder and others (1, 6-8) that when gutta-percha is heated, it must be compacted while cooling to prevent shrinkage and to assure maximum sealing of root canal systems. The availability of a larger warm condenser might help with the efficiency of obturating large canals. At present the only sizes available are a 30 and 45. Future studies of this technique should investigate the optimum relationship between condenser and canal sizes.
This research was funded by USPH Biomedical Research Support Grant RR05994 from the of The University of Tennessee, Memphis, College of Dentistry, Memphis, TN. The authors would like to thank Dr. Diane Brown and Dr. W. Thomas Fields for their assistance. Dr. Himel is director and Dr. Cain is an instructor, Division of Endodontics, University of Tennessee at Memphis, College of Dentistry, Memphis, TN. Address requests for reprints to Dr. Van T. Himei, Division of Endodontics, University of Tennessee at Memphis, College of Dentistry, 875 Union Ave., Memphis, TN 38163.
82
Journal of Endodontics
Himel and Cain References
1. Schilder H. Filling root canals in three dimensions. Dent Clin North Am 1967;11:723-44. 2. Larder TC, Prescott AJ, Brayton SM. Gutta-percha: a comparative study of three methods of obturation. J Endodon 1976;2:289-94. 3. Kuttler Y. Analysis and comparison of root canal filling techniques. Oral Surg 1979;48:153-9. 4. Friedman CE, Sandrik JL, Heuer MA, Rapp GW. Composition and physical properties of gutta-percha endodontic filling materials. J Endodon 1977;3:304-8. 5. Luks S. Gutta-percha versus silver points in the practice of endodontics. NY Dent J 1965;31:341-50.
6. Goldman M. Evaluation of two filling methods for root canals. J Endodon 1975;1:69-72. 7. Schilder H, Goodman AO, Aldrich W. The thermomechanical properties of gutta-percha. II. The history and molecular chemistry of gutta-percha. Oral Surg 1974;37:954-61. 8. Schilder H, Goodman AO, Aldrich W. The thermomechanical properties of gutta-percha. V. Volume changes in bulk gutta-percha as a function of temperature and its relationship to molecular phase transformation. Oral Surg 1985;59:285-96. 9. Luccy CT, Weller RN, Kulild JC. An evaluation of the apical seal produced by lateral and warm lateral condensation techniques. J Endodon 1990;16:1702.
Y o u M i g h t B e I n t e r e s t e d to K n o w Another verity destroyed! Lightning does strike twice. Indeed there is record of a park ranger who was struck by lightning seven times between 1942 and 1977 (New Sci. 1989:54). Supposedly an impending strike can be signalled by your hair literally standing on end--in which case one should crouch in as small a ball shape as possible. "Playing through" on a golf course and kite flying are not recommended.
Josh Wiley
JOURNAL OF ENDODONTICS
Copyright © 1993 by The American Association of Endodontists
An Evaluation of the Number of Condenser Insertions Needed with Warm Lateral Condensation of Guttapercha Van T. Himel, DDS, and Christopher W. Cain, DDS
lateral canals and foramina. This method uses a modified canal preparation, sequential placement of gutta-percha, and heated instruments to vertically compact the gutta-percha. The warm lateral condensation technique arose as a combination of the two previous techniques. It attempts to combine the advantages of cold lateral and warm vertical techniques to produce a homogenous mass of gutta-percha with adaptation to canal walls and fewer voids (9).
The purpose of this investigation was to determine the number of condenser insertions needed to obturate root canal systems using warm lateral condensation. Forty epoxide blocks with one major and five lateral canals placed at varying angles were used. The blocks received either one, three, five, or seven insertions of the warm instrument. The findings revealed gutta-percha and or sealer in every lateral canal. Cold compaction of the heated guttapercha produced more material in the lateral canals than did the use of the heated condenser alone. The optimum number of condenser insertions depended upon the position of the lateral canal, the size of the canal, and the bulk of material being heated. The areas of the main canal with a smaller diameter required fewer insertions of the warm condenser to push the gutta-percha into the lateral canals located in those areas.
MATERIALS AND METHODS Forty clear epoxide blocks (Kilgore Int'l Inc., Coldwater, MI) with five lateral canals, labeled A through E, placed at varying angles were used for this study. Each block was manufactured to the specifications of a #50 instrumented main canal. Dimensions and the placement of the lateral canals are noted in Fig. 1. All lateral canals were of equal dimensions. The patency of all lateral canals were evaluated by the placement of a # 10 K-type file through the side of the 1.5era
According to Schilder, "the final objective of endodontic procedures is the total three dimensional filling of the root canal system" (1). Various techniques and materials have been used in an attempt to achieve this goal (1-4). Most currently used filling techniques employ either a solid core and cementing substance or a material which can be adapted to the shape of the root canal system (1, 5). Gutta-percha is now the filling material of choice because of its biological and mechanical properties (6-8). Several gutta-percha techniques have been used in an attempt to achieve a void-free, homogeneous filling. While advances have been made in alternate obturation techniques, the cold lateral condensation technique is still one of the most frequently used techniques today. One stated disadvantage of cold lateral condensation is that at no time is a homogenous mass of gutta-percha developed (1). The final filling is composed of a large number of gutta-percha cones tightly pressed together and joined by frictional grip and cementing substance. Warm vertical condensation of gutta-percha is claimed by Schilder (1) to provide a greater density of gutta-percha at the apical portion of the filling and to consistently obturate
T
2 . 0 c~
O.l~
E ~
/ A
.,,,.
I
'
T
B
FIG 1. Epoxide block with a main canal and five lateral canals labeled AtoE. 79
80
Journal of Endodontics
Himel and Cain
lateral canal into the main canal. Working lengths of the main canals were established by inserting a #50 K-type file into the canals. The length from the canal apex to the coronal orifice was measured. The blocks were covered with foil and tape to prevent visual inspection during obturation. They were then numbered and randomly divided into four groups. The groups were differentiated by the number of Endotec condenser (Caulk/Dentsply, Milford, DE) insertions used during obturation: group 1, one Endotec insertion at 12 s each; group 2, three Endotec insertions at 12 s each; group 3, five Endotec insertions at 12 s each; and group 4, seven Endotec insertions at 12 s each. To ensure consistency, the four groups were treated by a clinician with experience using this obturation technique. Each block was fitted with a #50 master apical cone seated to the working length. Roth's 801 elite grade sealer (Roth Drug Co., Chicago, IL) was mixed according to the manufacturer's recommendation and placed into the canal with a #30 K-type file. The apical third of the file was coated with sealer, inserted into the canal at working length, and rotated in a counterclockwise direction to coat the canal walls. The master apical cone, with sealer placed on the apical one third, was inserted to the working length. A cold condenser was inserted followed by a #20 accessory cone to within 1 m m of working length prior to the insertion of the Endotec. The accessory cone provided additional bulk of gutta-percha in the apical third and is a technique suggested by the manufacturer. The Endotec condenser was placed into the canal until resistance was met and then the heat activator button was depressed for 12 s. The tip was pressed in an apical direction with a lateral and circumferential rotary motion to a depth of 2 m m from the working length. After the 12-s interval the heat activator was released and the tip of the heated instrument was removed. A #20 accessory point was then placed into the prepared space. This process was repeated as prescribed for each group. Cold lateral condensation of additional accessory cones was used to complete obturation after the specified number of warm condenser insertions per group was completed. Number 25 accessory cones were used in the coronal half of the canal. The blocks were back filled to within 4 m m of the orifice. Upon completion of obturation, each block was stored for a m i n i m u m of 7 days at room temperature and 100% humidity. The foil was removed from each clear block and the lateral canals microscopically evaluated with a Meiji EMT microscope at x l0 magnification. The length of filling material, either sealer or gutta-percha, extruded into the lateral canals from the main canal was measured in 0.5-mm increments. The data obtained were statistically analyzed using a one-way analysis of variance (ANOVA). The groups were shown to be statistically different at the p<0.05 level of significance.
The total length of gutta-percha found in all lateral canals increased with additional use of the warm condenser, up to five insertions. The greatest increase occurred between one and three insertions, with no statistical difference (ANOVA, p<0.05) between five and seven insertions (Fig. 3). When the lateral canals were evaluated individually, a difference was noted. Canal A, the most apical canal, had less gutta-percha with increased use of the warm condenser while all other canals tended to have more gutta-percha with increased use (Fig. 4). DISCUSSION The choice of sealer seems to affect the ease of manipulating gutta-percha when using warm lateral condensation. During the process of obturation, the zinc oxide and eugenol sealer had a tendency to become sticky, causing the gutta-percha and sealer to adhere to the warm instrument. This made obturation of the root canal system and cleaning of the
M E A N G u ' r r A - P E R C H A AND S E A L E R 8
FIVE INSERTIONS I SEVEN INSER'I3ONSJ
6
=
4
I
2
0
A
B
C
D
E
CANALS
FIG 2. Graph representing the mean length of filling with gutta-percha and sealer in each lateral canal. A statistical difference (ANOVA,
p<0.05) was noted in group D (1D to 3D, 3D to 5D), and group E (1E to 3E, 1E to 5E). I I P
i
|I
~ I
I
~
•
R P R h I
•
I
o ntu Q. <
o 11
O
RESULTS 0
The obturation produced either gutta-percha and/or sealer in all lateral canals (Fig. 2). The most consistent results were found in canals A and B when gutta-percha and/or sealer were measured. Lateral canals C, D, and E were not as consistent. Sealer was in all lateral canals and always preceded gutta-percha regardless of the number of warm condenser insertions.
1
3
5
7
N u m b e r of Insertions
FIG 3. Graph showing the mean gutta-percha (mm) in all lateral canals for each group of insertions. A statistical difference (ANOVA, p<0.05) was noted between insertions 1 to 3, 5, and 7 and insertions 3-1, 5, and 7. Five and seven insertions were not statistically different. No gutta-percha was found in groups A5 or El.
Warm Lateral Condensation
Vol. 19, No. 2, February 1993
MEAN GUTTA-PERCHA 1.S- IN LATERAL CANALS
(I ONEr~ER'nON [i nEE,NSER'rDNSI FIVE INSERTIONS I SEVEN INSERTIONS,,~
A
B
C
D
E
CANALS FIG 4. Graph illustrating the mean gutta-percha in each lateral canal as labeled A to E. A statistical difference (ANOVA, p<0.05) was noted in group A (1-5, 1-7), group C (1-5, 1-7), group D (1-3, 1-5, 1-7, 3-5, 3-7), and group E (1-3, 1-5, 1-7).
instrument difficult. The problem was overcome using alcohol wipes to clean sealer from the instrument. In a follow-up pilot study, the authors used a different sealer which decreased in viscosity with heat, resulting in increased flow properties. The use of the second sealer (AH26; De Trey/Dentsply, Milford, DE) would seem to overcome the problem of material sticking to the instrument. Warm lateral condensation was effective in the obturation of artificial canals as all lateral canals contained either guttapercha and/or sealer. The irregular positioning and the small size of these lateral canals seem to indicate that this technique would fill root canal irregularities such as fenestrations in as equally an effective manner. The use of a file to place sealer into these relatively large curved canals seemed to be an effective method as sealer was always seen in advance of the gutta-percha. The technique of sealer placement and the amount inserted could be as critical a factor to its movement as the obturation technique and is an area in need of additional research. The number of insertions of the warm spreader did not seem to have a consistent effect on the material in canals when sealer was combined with gutta-percha. Canals with less gutta-percha tended to have more sealer while canals with more more gutta-percha had less sealer. This could be due to the displacement of sealer by the gutta-percha or by the inhibition of gutta-percha movement by the sealer. Such displacement is desirable unless gutta-percha is pushed into the periapical tissues in large quantities and/or into critical anatomical structures such as the mandibular canal. As Luccy et al. (9) have suggested, an ideal temperature may exist which would allow for the production of an optimal homogeneous mass of gutta-percha. This ideal temperature may also help the clinician restrict the flow of filling materials to canal systems avoiding periapical inflammatory responses. Schilder has stated (8) that less change in volume occurs upon cooling when lower temperatures are used. Any technique which uses heat above 45°C predisposes to shrinkage of the gutta-percha and requires compaction (8). Being able to accurately control the temperature could possibly help the clinician control the direction and amount of gutta-percha flow. When gutta-percha alone was analyzed, a definite relationship was noticed between gutta-percha and the number of
81
condenser insertions. Figure 3 shows the results when guttapercha was totaled in all lateral canals. It would seem that statistically (ANOVA, p<0.05) more movement of material occurred with increased insertions of the warm condenser up to five insertions. Differences were observed when the canals were evaluated individually (Fig. 4). The size of the canal, the bulk of material in the main canal, the orientation of lateral canal to main canal, and the compaction of cooling gutta-percha with a cold spreader represent possible causes of these differences. Additional insertions of the heated condenser caused an increased movement of gutta-percha in all canals except in A, the most apical canal (Fig. 1). This apical position made it the only canal which would require more of a vertical than a lateral vector of force to be placed on the filling material. In the single insertion group, the warm instrument was placed to within 2 m m of the working length and a cold spreader inserted into the heated mass. This spreader compacted the cooling material, pushing it farther into canal A than the multiple insertion groups in which the cold spreader was not used in the more apical portions of the main canal. When the heated spreader was used three or more times before a cold spreader was used, less vertical movement of gutta-percha occurred. Canal B was in a position to receive both vertical and horizontal forces. Canals C, D, and E were positioned so that more gutta-percha flowed into them as a result of the lateral forces. More insertions were necessary for heating the greater mass of gutta-percha as the main canal became wider in the more coronal sections. The larger diameter made movement of gutta-percha into lateral canals more difficult than in the narrower, more apical portions of the canal. With a large mass of gutta-percha present, the heated condenser was unable to thermoplasticize the gutta-percha on the periphery of the canal walls as efficiently as in the more apical portion containing a smaller mass of material. The lateral forces exerted by the condenser are dissipated over a larger diameter and are therefore less effective in forcing gutta-percha into these lateral canals. Increased numbers of insertions were necessary to overcome these problems. The cold spreader pushed the heated gutta-percha laterally during the cooling phase. This would seem to be in agreement with Schilder and others (1, 6-8) that when gutta-percha is heated, it must be compacted while cooling to prevent shrinkage and to assure maximum sealing of root canal systems. The availability of a larger warm condenser might help with the efficiency of obturating large canals. At present the only sizes available are a 30 and 45. Future studies of this technique should investigate the optimum relationship between condenser and canal sizes.
This research was funded by USPH Biomedical Research Support Grant RR05994 from the of The University of Tennessee, Memphis, College of Dentistry, Memphis, TN. The authors would like to thank Dr. Diane Brown and Dr. W. Thomas Fields for their assistance. Dr. Himel is director and Dr. Cain is an instructor, Division of Endodontics, University of Tennessee at Memphis, College of Dentistry, Memphis, TN. Address requests for reprints to Dr. Van T. Himei, Division of Endodontics, University of Tennessee at Memphis, College of Dentistry, 875 Union Ave., Memphis, TN 38163.
82
Journal of Endodontics
Himel and Cain References
1. Schilder H. Filling root canals in three dimensions. Dent Clin North Am 1967;11:723-44. 2. Larder TC, Prescott AJ, Brayton SM. Gutta-percha: a comparative study of three methods of obturation. J Endodon 1976;2:289-94. 3. Kuttler Y. Analysis and comparison of root canal filling techniques. Oral Surg 1979;48:153-9. 4. Friedman CE, Sandrik JL, Heuer MA, Rapp GW. Composition and physical properties of gutta-percha endodontic filling materials. J Endodon 1977;3:304-8. 5. Luks S. Gutta-percha versus silver points in the practice of endodontics. NY Dent J 1965;31:341-50.
6. Goldman M. Evaluation of two filling methods for root canals. J Endodon 1975;1:69-72. 7. Schilder H, Goodman AO, Aldrich W. The thermomechanical properties of gutta-percha. II. The history and molecular chemistry of gutta-percha. Oral Surg 1974;37:954-61. 8. Schilder H, Goodman AO, Aldrich W. The thermomechanical properties of gutta-percha. V. Volume changes in bulk gutta-percha as a function of temperature and its relationship to molecular phase transformation. Oral Surg 1985;59:285-96. 9. Luccy CT, Weller RN, Kulild JC. An evaluation of the apical seal produced by lateral and warm lateral condensation techniques. J Endodon 1990;16:1702.
Y o u M i g h t B e I n t e r e s t e d to K n o w Another verity destroyed! Lightning does strike twice. Indeed there is record of a park ranger who was struck by lightning seven times between 1942 and 1977 (New Sci. 1989:54). Supposedly an impending strike can be signalled by your hair literally standing on end--in which case one should crouch in as small a ball shape as possible. "Playing through" on a golf course and kite flying are not recommended.
Josh Wiley