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Incidence and position of the canal isthmus. Part 1. Mesiobuccal root of the maxillary first molar
0099-2399/95/2107-0380503.00/0 JOURNAL OF ENDODONTfCS
Printed in U.S.A. VOL. 21, No. 7, JuLY 1995
Copyright © 1995 by The American Association of Endodontists
Incidence and Position of the Canal Isthmus. Part 1. Mesiobuccal Root of the Maxillary First Molar R. Norman Weller, DMD, MS, Stephen P. Niemczyk, DMD, and Syngcuk Kim, DDS, PhD
The mesiobuccal roots of 50 randomly selected maxillary first molars were examined to assess the incidence and position of the canal isthmus. Transverse serial sections of the apical 6 mm of each root were prepared in 1-mm increments. The apical side of each section was stained with methylene blue dye, viewed with a surgical operating microscope, and videotaped. Forty percent of the roots had one canal, whereas 60% had two canals. None of the sections had more than two main canals. The incidence of an isthmus was highest in the apical 3- to 5-mm levels. In teeth that had two canals, the 4-mm sections contained a complete or partial isthmus 100% of the time. The concept of a partial isthmus was presented. Failure to deal with the isthmus may explain why some posterior teeth do not heal completely following endodontic surgery.
varies. Pineda (11) reported interconnections in 4.9% of the roots examined. This percentage is definitely lower than the 16% reported by Green (10) and the 30.1% reported by Cambruzzi and Marshall (13). The highest percentage of an isthmus (52%) was found by Vertucci (12). He also reported that 75% of the anastamoses were located in the middle and 15% were in the apical third of the root. Because of the possible importance of the canal isthmus in surgical endodontics, especially in the mesiobuccal root of the maxillary first molar, a more detailed investigation was undertaken. The purpose of this study was to determine the incidence and location of the isthmus. The type of root canal configuration and the level of canal bifurcation or convergence were also examined.
M A T E R I A L S AND M E T H O D S Fifty human maxillary left and right first molars were randomly selected and stored in 10% formalin. The age, sex, and race of the patients were unknown. The identification of these teeth as maxillary first molars was confirmed by accepted criteria (14). Using an ultrathin separating disk (Jel-Thin 9'S; Jelenko, Armonk, NY), the mesiobuccal crown and root were resected in one piece. The first cut was made through the buccal furcation to the palatal root. The second cut was directed through the mesial furcation and joined the first cut. The opening into the pulp chamber was sealed with wax to prevent embedding material from entering the root canal system. Each root was embedded separately in clear resin (Caulk/ Dentsply, Milford, DE). Starting at the root apex, serial transverse sections were made perpendicular to the long axis of the root, with a low-speed diamond saw (Buehler Ltd., Evanston, IL) at 1-mm increments to a level 6 mm from the apex. Each section was placed in 5.25% sodium hypochlorite (Clorox; Clorox Co., Oakland, CA) for 24 h to remove any organic material remaining in the root canal. No endodontic instruments were placed into the root canals of any specimen. Each section was rinsed in water and dried. The serial sections of each root were arranged from the 1-mm level to the 6-mm level. Only the apical sides of each section were evaluated. The resected surface was stained with 2% methylene blue dye (The Coleman & Bell Co., Norwood, OH) and examined
The success rate of surgical endodontics in posterior teeth is often less than in anterior teeth. Friedman et al. (1) reported successful results in only 44.1% of the premolars and molars treated. Other authors (2-4) showed 71 to 73% success in apicoectomized molars. However, successful treatment in anterior teeth was reported to be as high as 85 to 90% (5-7). The maxillary first molar and, in particular, the mesiobuccal root of this tooth, is frequently treated surgically (8). However, the successful healing is lower than the mandibular first molar following surgery (9). Possible factors affecting the success of endodontic surgery are the complexity of the surgical procedure, untreated root canals, or a poor apical seal of the root canal system. Another factor that is not often considered is the canal isthmus. An isthmus is a narrow, ribbon-shaped, communication between two root canals that contains pulp or pupally derived tissue. It is also known as a corridor (10), a lateral interconnection (11), or a transverse anastamosis (12). Any root that contains two root canals has the potential to contain an isthmus. The reported incidence of an isthmus in the mesiobuccal foot of the maxillary first molar 380
Vol. 21, No. 7, July 1995
Canal Isthmus
FIG 1. Representative examples of sections with a complete isthmus (original magnification x32).
TABLE 1. Canal configurations in the mesiobuccal root of maxillary first molars Canal Configuration
No. of Roots
%
I II III IV
20 10 17 3
40 20 34 6
Total
50
100
Type Type Type Type
FIG 2. Representative examples of sections with a partial isthmus
(arrow) (original magnification x32). TABLE 2. Level of convergence of type II canals Level from Apex (mm) 6 5 4 3 2 1 Total
with a surgical operating microscope (.lED MED Instrument Co., St. Louis, MO) at X32 magnification. A videotape of each level was made for evaluation. Using this videotape, two of the authors simultaneously viewed each section and determined the number of root canals present and the presence or absence of an isthmus. If an isthmus was present, it was classified as complete or partial. A complete isthmus was one with a continuous, narrow opening between the two main root canals (Fig. 1). A partial isthmus was classified as an incomplete communication with one or more patent openings, through the section, between the two main canals. The opening could be of any size (Fig. 2). After all the sections were evaluated, the type of canal configuration present in each root was classified according to Weine (15). Briefly, a type I configuration had a single canal present at each level. A type II configuration had two separate
381
No. of Roots
%
3 3 4
30 30 40
10
100
TABLE 3. NO. of canals at each level Level from Apex (mm)
No. with 1 Canal
%
No. with 2 Canals
%
6 5 4 3 2 1
23 21 25 29 30 37
46 42 50 58 6O 74
27 29 25 21 20 13
54 58 50 42 4O 26
canals that merged short of the apex to form a single root canal. A type III configuration had two separate canals through each section. Finally, a type IV configuration had a single canal that divided short of the apex into two separate root canals.
382
Weller et al.
Journal of Endodontics TABLE 4. Incidence of an isthmus at each level in sections with two canals
Level from Apex (ram)
No. with 2 Canals
NI
%
CI
%
PI
%
CI + PI
%
6 5 4 3 2 1
27 29 25 21 20 13
5 5 0 2 7 9
18.5 17.2 0 9.5 35.0 69.2
4 4 3 3 1 1
14.8 13.8 12.0 14.3 5.0 7.7
18 20 22 16 12 3
66.7 69.0 88.0 76.2 60.0 23.1
22 24 25 19 13 4
81.5 82.8 100.0 90.5 65.0 30.8
NI, no isthmus; CI, complete isthmus; PI, partial isthmus.
![
[
•
Complete Isthmus (CI}
[]
Partial isthmus (Pi)
[] Total Isthmus (el + Pl)
40
i
i 1
i
i
3 5 Level from Apex (ram)
2
5
FIG 3. Percentage of a complete isthmus, a partial isthmus, and the total number of isthmuses at each level (mm) from the apex.
RESULTS The results are listed in Tables 1 to 4. One root canal was found in 40% of the roots examined, and two canals were present 60% of the time (Table 1). All of the canals classified as type II converged into one canal within 2 to 4 mm of the apex (Table 2), whereas in three roots the canals that bifurcated into two separate canals (type IV) did so more than 3 mm from the root apex. Table 3 shows the number of canals at each level within the root. None of the sections had more than two main root canals. For those sections with two canals (Table 4 and Fig. 3), the incidence of an isthmus, either complete or partial, was highest in the 3- to 5-ram sections. For instance, the 4-ram sections contained a complete isthmus 12% and a partial isthmus 88% of the time for a combined total of 100%.
DISCUSSION The number of root canals and canal configurations (Table 1) in the present investigation are in agreement with previous studies (10-12). It is possible, however, that had the entire root been sectioned, the types of canal systems might have been different. For instance, those roots classified as type I might have had two canals more coronally (type II). Likewise, a type III system could have been a type IV canal. Weine et al. (16) defined a type II configuration as a larger buccal canal and a smaller lingual canal that merge from 1 to 4 mm from the apex. All of the roots that were classified as type II in this investigation joined 2 to 4 mm from the apex (Table 2). This is important because, when a root is surgically resected, the lingual canal may be exposed. If that canal had not been obturated before the surgical procedure, then the untreated canal could contribute to failure of the case unless identified and sealed with a retrofilling. The same principles hold true for type III canal configurations. The incidence of a complete isthmus in this study was much
lower than the reports by Cambruzzi and Marshall (13) and Vertucci (12). Cambruzzi and Marshall (13) examined the beveled surface of both maxillary first and second molars. They did not report the incidence in each tooth, but only reported a combined number. It is possible that more isthmuses were present in the second molars than in the first molars. Vertucci (12) examined the entire root canal systems of transparent specimens. Even though he reported a 52% incidence of transverse anastamoses, only 15% were found in the apical third of the root. This more closely agrees with our findings. The concept of a partial isthmus has not been presented before. Any openings on the resected root surface may contain microorganisms or necrotic tissue or act as a portal of exit for an uninstrumented or unfilled part of the root canal system. This may explain why some cases of apparently well-obturated and sealed canals do not heal following endodontic surgery. Continued leakage through a complete or partial isthmus could prevent a successful result. There were many more sections at each level of the root containing a partial isthmus than a complete isthmus (Fig. 3). Whenever any part of the mesiobuccal root is resected, and two main canals are located, the results of this study indicate that the presence of an isthmus must be assumed. The area between the two canals should always be prepared and sealed with a retrofilling. Several factors made visualization of the apical morphology possible. Methylene blue dye was used to stain each section. The dye made it easier to see each root canal and isthmus present. The operating microscope was also invaluable to this investigation. The high-intensity light and high magnification made viewing of even the partial isthmus openings possible. In the past, not only was the canal isthmus often overlooked, but it was also very difficult to prepare if located. Now, with the advent of microscopic endodontic surgical techniques, we are able to view the resected surface of the root better, identify the isthmus, prepare it with an ultrasonic tip, and seal it with appropriate materials. The recognition and treatment of the canal isthmus may be one factor that will reduce the failure rate of surgical endodontics in posterior teeth, especially the mesiobuccal root of the maxillary first molar. Dr. Weller is director, postgraduate endodontJcs;Dr. Niemczyk is director, undergraduate endodontics; and Dr. Kim is chairman, Department of Endodontics, School of Dental Medicine, University of Pennsylvania,Philadelphia, PA. Address requests for reprints to Dr. Syngcuk Kim, Louis I. Grossman Professor and Chairman, Department of Endodontics, School of Dental Medicine, University of Pennsylvania, 4001 Spruce Street, Philadelphia, PA 19104- 6003.
References 1. Friedman S, Lustmann J, Shaharabany V. Treatment results of apical surgery in premolar and molar teeth. J Endodon 1991;17:30-3.
Voh 21, No. 7, July 1995 2. Altonen M, Mattila K. Follow-up study of apicoectomized molars. Int J Oral Surg 1976;5:33-40. 3. Persson G. Periapical surgery of molars. Int J Oral Surg 1982;11:96100. 4. Ioannides C, Borstlap WA. Apicoectomy on molars: a clinical and radiologic study. Int J Oral Surg 1983;12:73-9. 5. Storms JL. Factors that influence the success of endodontic treatment. J Can Dent Assoc 1969;35:83-97. 6. Ingle Jl. Endodontics. Philadelphia: Lea & Febiger, 1965:54-77. 7. Harry FJ, Parkins BJ, Wengraf AM. Success rate in root canal therapy. A retrospective study of conventional cases. Br Dent J 1970;128:65-70. 8. Rapp EL, Brown CE, Newton CW. An analysis of success and failure of apicoectomies. J Endodon 1991 ;17:508-12. 9. Nordenram A, Svardstrom G. Results of apicoectomy. Swed Dent J 1970;63:593-604.
Canal Isthmus
383
10. Green D. Double canals in single roots. Oral Surg 1973;35:689-96. 11. Pineda F. Roentgenographic investigation of the mesiobuccal root of the maxillary first molar. Oral Surg 1973;36:253-60. 12. Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg 1984;58:589-99. 13. Cambruzzi JV, Marshall FJ. Molar endodontic surgery. J Can Dent Assoc 1983;1:61-6. 14. Sicher H, DuBrul EL. Oral anatomy. 6th ed. St. Louis: CV Mosby, 1975:236-9. 15. Weine FS. Endodontic therapy. 3rd ed. St. Louis: CV Mosby, 1982: 210-11. 16. Weine FS, Healey HJ, Gerstein H, Evanson L. Canal configuration in the mesiobuccal root of the maxillary first molar and its endodontic significance. Oral Surg 1969;28:419-25.
A Word to the Wise We seem to have a surfeit of disputacious by nature persons in our society. A tactic common to such folk is the use of the phrases, "just for the sake of argument" or "to play the Devil's advocate," by which they then introduce mindless, time-wasting, and irrelevant "issues." This plague on modern life could be averted by heeding C. S. Lewis' assessment of a raised objection that it was "in one sense very right, very charitable ...and very sensitive. It has every amiable quality except that of being useful." Zachariah Yeomans
Printed in U.S.A. VOL. 21, No. 7, JuLY 1995
Copyright © 1995 by The American Association of Endodontists
Incidence and Position of the Canal Isthmus. Part 1. Mesiobuccal Root of the Maxillary First Molar R. Norman Weller, DMD, MS, Stephen P. Niemczyk, DMD, and Syngcuk Kim, DDS, PhD
The mesiobuccal roots of 50 randomly selected maxillary first molars were examined to assess the incidence and position of the canal isthmus. Transverse serial sections of the apical 6 mm of each root were prepared in 1-mm increments. The apical side of each section was stained with methylene blue dye, viewed with a surgical operating microscope, and videotaped. Forty percent of the roots had one canal, whereas 60% had two canals. None of the sections had more than two main canals. The incidence of an isthmus was highest in the apical 3- to 5-mm levels. In teeth that had two canals, the 4-mm sections contained a complete or partial isthmus 100% of the time. The concept of a partial isthmus was presented. Failure to deal with the isthmus may explain why some posterior teeth do not heal completely following endodontic surgery.
varies. Pineda (11) reported interconnections in 4.9% of the roots examined. This percentage is definitely lower than the 16% reported by Green (10) and the 30.1% reported by Cambruzzi and Marshall (13). The highest percentage of an isthmus (52%) was found by Vertucci (12). He also reported that 75% of the anastamoses were located in the middle and 15% were in the apical third of the root. Because of the possible importance of the canal isthmus in surgical endodontics, especially in the mesiobuccal root of the maxillary first molar, a more detailed investigation was undertaken. The purpose of this study was to determine the incidence and location of the isthmus. The type of root canal configuration and the level of canal bifurcation or convergence were also examined.
M A T E R I A L S AND M E T H O D S Fifty human maxillary left and right first molars were randomly selected and stored in 10% formalin. The age, sex, and race of the patients were unknown. The identification of these teeth as maxillary first molars was confirmed by accepted criteria (14). Using an ultrathin separating disk (Jel-Thin 9'S; Jelenko, Armonk, NY), the mesiobuccal crown and root were resected in one piece. The first cut was made through the buccal furcation to the palatal root. The second cut was directed through the mesial furcation and joined the first cut. The opening into the pulp chamber was sealed with wax to prevent embedding material from entering the root canal system. Each root was embedded separately in clear resin (Caulk/ Dentsply, Milford, DE). Starting at the root apex, serial transverse sections were made perpendicular to the long axis of the root, with a low-speed diamond saw (Buehler Ltd., Evanston, IL) at 1-mm increments to a level 6 mm from the apex. Each section was placed in 5.25% sodium hypochlorite (Clorox; Clorox Co., Oakland, CA) for 24 h to remove any organic material remaining in the root canal. No endodontic instruments were placed into the root canals of any specimen. Each section was rinsed in water and dried. The serial sections of each root were arranged from the 1-mm level to the 6-mm level. Only the apical sides of each section were evaluated. The resected surface was stained with 2% methylene blue dye (The Coleman & Bell Co., Norwood, OH) and examined
The success rate of surgical endodontics in posterior teeth is often less than in anterior teeth. Friedman et al. (1) reported successful results in only 44.1% of the premolars and molars treated. Other authors (2-4) showed 71 to 73% success in apicoectomized molars. However, successful treatment in anterior teeth was reported to be as high as 85 to 90% (5-7). The maxillary first molar and, in particular, the mesiobuccal root of this tooth, is frequently treated surgically (8). However, the successful healing is lower than the mandibular first molar following surgery (9). Possible factors affecting the success of endodontic surgery are the complexity of the surgical procedure, untreated root canals, or a poor apical seal of the root canal system. Another factor that is not often considered is the canal isthmus. An isthmus is a narrow, ribbon-shaped, communication between two root canals that contains pulp or pupally derived tissue. It is also known as a corridor (10), a lateral interconnection (11), or a transverse anastamosis (12). Any root that contains two root canals has the potential to contain an isthmus. The reported incidence of an isthmus in the mesiobuccal foot of the maxillary first molar 380
Vol. 21, No. 7, July 1995
Canal Isthmus
FIG 1. Representative examples of sections with a complete isthmus (original magnification x32).
TABLE 1. Canal configurations in the mesiobuccal root of maxillary first molars Canal Configuration
No. of Roots
%
I II III IV
20 10 17 3
40 20 34 6
Total
50
100
Type Type Type Type
FIG 2. Representative examples of sections with a partial isthmus
(arrow) (original magnification x32). TABLE 2. Level of convergence of type II canals Level from Apex (mm) 6 5 4 3 2 1 Total
with a surgical operating microscope (.lED MED Instrument Co., St. Louis, MO) at X32 magnification. A videotape of each level was made for evaluation. Using this videotape, two of the authors simultaneously viewed each section and determined the number of root canals present and the presence or absence of an isthmus. If an isthmus was present, it was classified as complete or partial. A complete isthmus was one with a continuous, narrow opening between the two main root canals (Fig. 1). A partial isthmus was classified as an incomplete communication with one or more patent openings, through the section, between the two main canals. The opening could be of any size (Fig. 2). After all the sections were evaluated, the type of canal configuration present in each root was classified according to Weine (15). Briefly, a type I configuration had a single canal present at each level. A type II configuration had two separate
381
No. of Roots
%
3 3 4
30 30 40
10
100
TABLE 3. NO. of canals at each level Level from Apex (mm)
No. with 1 Canal
%
No. with 2 Canals
%
6 5 4 3 2 1
23 21 25 29 30 37
46 42 50 58 6O 74
27 29 25 21 20 13
54 58 50 42 4O 26
canals that merged short of the apex to form a single root canal. A type III configuration had two separate canals through each section. Finally, a type IV configuration had a single canal that divided short of the apex into two separate root canals.
382
Weller et al.
Journal of Endodontics TABLE 4. Incidence of an isthmus at each level in sections with two canals
Level from Apex (ram)
No. with 2 Canals
NI
%
CI
%
PI
%
CI + PI
%
6 5 4 3 2 1
27 29 25 21 20 13
5 5 0 2 7 9
18.5 17.2 0 9.5 35.0 69.2
4 4 3 3 1 1
14.8 13.8 12.0 14.3 5.0 7.7
18 20 22 16 12 3
66.7 69.0 88.0 76.2 60.0 23.1
22 24 25 19 13 4
81.5 82.8 100.0 90.5 65.0 30.8
NI, no isthmus; CI, complete isthmus; PI, partial isthmus.
![
[
•
Complete Isthmus (CI}
[]
Partial isthmus (Pi)
[] Total Isthmus (el + Pl)
40
i
i 1
i
i
3 5 Level from Apex (ram)
2
5
FIG 3. Percentage of a complete isthmus, a partial isthmus, and the total number of isthmuses at each level (mm) from the apex.
RESULTS The results are listed in Tables 1 to 4. One root canal was found in 40% of the roots examined, and two canals were present 60% of the time (Table 1). All of the canals classified as type II converged into one canal within 2 to 4 mm of the apex (Table 2), whereas in three roots the canals that bifurcated into two separate canals (type IV) did so more than 3 mm from the root apex. Table 3 shows the number of canals at each level within the root. None of the sections had more than two main root canals. For those sections with two canals (Table 4 and Fig. 3), the incidence of an isthmus, either complete or partial, was highest in the 3- to 5-ram sections. For instance, the 4-ram sections contained a complete isthmus 12% and a partial isthmus 88% of the time for a combined total of 100%.
DISCUSSION The number of root canals and canal configurations (Table 1) in the present investigation are in agreement with previous studies (10-12). It is possible, however, that had the entire root been sectioned, the types of canal systems might have been different. For instance, those roots classified as type I might have had two canals more coronally (type II). Likewise, a type III system could have been a type IV canal. Weine et al. (16) defined a type II configuration as a larger buccal canal and a smaller lingual canal that merge from 1 to 4 mm from the apex. All of the roots that were classified as type II in this investigation joined 2 to 4 mm from the apex (Table 2). This is important because, when a root is surgically resected, the lingual canal may be exposed. If that canal had not been obturated before the surgical procedure, then the untreated canal could contribute to failure of the case unless identified and sealed with a retrofilling. The same principles hold true for type III canal configurations. The incidence of a complete isthmus in this study was much
lower than the reports by Cambruzzi and Marshall (13) and Vertucci (12). Cambruzzi and Marshall (13) examined the beveled surface of both maxillary first and second molars. They did not report the incidence in each tooth, but only reported a combined number. It is possible that more isthmuses were present in the second molars than in the first molars. Vertucci (12) examined the entire root canal systems of transparent specimens. Even though he reported a 52% incidence of transverse anastamoses, only 15% were found in the apical third of the root. This more closely agrees with our findings. The concept of a partial isthmus has not been presented before. Any openings on the resected root surface may contain microorganisms or necrotic tissue or act as a portal of exit for an uninstrumented or unfilled part of the root canal system. This may explain why some cases of apparently well-obturated and sealed canals do not heal following endodontic surgery. Continued leakage through a complete or partial isthmus could prevent a successful result. There were many more sections at each level of the root containing a partial isthmus than a complete isthmus (Fig. 3). Whenever any part of the mesiobuccal root is resected, and two main canals are located, the results of this study indicate that the presence of an isthmus must be assumed. The area between the two canals should always be prepared and sealed with a retrofilling. Several factors made visualization of the apical morphology possible. Methylene blue dye was used to stain each section. The dye made it easier to see each root canal and isthmus present. The operating microscope was also invaluable to this investigation. The high-intensity light and high magnification made viewing of even the partial isthmus openings possible. In the past, not only was the canal isthmus often overlooked, but it was also very difficult to prepare if located. Now, with the advent of microscopic endodontic surgical techniques, we are able to view the resected surface of the root better, identify the isthmus, prepare it with an ultrasonic tip, and seal it with appropriate materials. The recognition and treatment of the canal isthmus may be one factor that will reduce the failure rate of surgical endodontics in posterior teeth, especially the mesiobuccal root of the maxillary first molar. Dr. Weller is director, postgraduate endodontJcs;Dr. Niemczyk is director, undergraduate endodontics; and Dr. Kim is chairman, Department of Endodontics, School of Dental Medicine, University of Pennsylvania,Philadelphia, PA. Address requests for reprints to Dr. Syngcuk Kim, Louis I. Grossman Professor and Chairman, Department of Endodontics, School of Dental Medicine, University of Pennsylvania, 4001 Spruce Street, Philadelphia, PA 19104- 6003.
References 1. Friedman S, Lustmann J, Shaharabany V. Treatment results of apical surgery in premolar and molar teeth. J Endodon 1991;17:30-3.
Voh 21, No. 7, July 1995 2. Altonen M, Mattila K. Follow-up study of apicoectomized molars. Int J Oral Surg 1976;5:33-40. 3. Persson G. Periapical surgery of molars. Int J Oral Surg 1982;11:96100. 4. Ioannides C, Borstlap WA. Apicoectomy on molars: a clinical and radiologic study. Int J Oral Surg 1983;12:73-9. 5. Storms JL. Factors that influence the success of endodontic treatment. J Can Dent Assoc 1969;35:83-97. 6. Ingle Jl. Endodontics. Philadelphia: Lea & Febiger, 1965:54-77. 7. Harry FJ, Parkins BJ, Wengraf AM. Success rate in root canal therapy. A retrospective study of conventional cases. Br Dent J 1970;128:65-70. 8. Rapp EL, Brown CE, Newton CW. An analysis of success and failure of apicoectomies. J Endodon 1991 ;17:508-12. 9. Nordenram A, Svardstrom G. Results of apicoectomy. Swed Dent J 1970;63:593-604.
Canal Isthmus
383
10. Green D. Double canals in single roots. Oral Surg 1973;35:689-96. 11. Pineda F. Roentgenographic investigation of the mesiobuccal root of the maxillary first molar. Oral Surg 1973;36:253-60. 12. Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg 1984;58:589-99. 13. Cambruzzi JV, Marshall FJ. Molar endodontic surgery. J Can Dent Assoc 1983;1:61-6. 14. Sicher H, DuBrul EL. Oral anatomy. 6th ed. St. Louis: CV Mosby, 1975:236-9. 15. Weine FS. Endodontic therapy. 3rd ed. St. Louis: CV Mosby, 1982: 210-11. 16. Weine FS, Healey HJ, Gerstein H, Evanson L. Canal configuration in the mesiobuccal root of the maxillary first molar and its endodontic significance. Oral Surg 1969;28:419-25.
A Word to the Wise We seem to have a surfeit of disputacious by nature persons in our society. A tactic common to such folk is the use of the phrases, "just for the sake of argument" or "to play the Devil's advocate," by which they then introduce mindless, time-wasting, and irrelevant "issues." This plague on modern life could be averted by heeding C. S. Lewis' assessment of a raised objection that it was "in one sense very right, very charitable ...and very sensitive. It has every amiable quality except that of being useful." Zachariah Yeomans