n
J \¡®j m
ARTICLES
Root canal morphology of the maxillary first premolar Fran k J. V ertucci, DMD Anthony Gegauff, DMD
Methods and materials T h e d e t e r m in a t io n s o f th e n u m b e r o f ro o t c a n a ls , t h e i r ty p e,
For this investigation, we obtained 400 maxillary first premolars from several oral surgery practices. All were adult teeth. The age, sex, and race of the patient and reasons for extraction were not known. Im mediately after extraction, the teeth were fixed in 10% Formalin solution and were then decalcified in 5% hy drochloric acid solution. The teeth then were washed in tap water and placed in a 5% solution of potassium hydroxide for 24 hours. Hematoxy lin dye was injected into pulp cavities with a no. 25-gauge needle on a Luer-Lok plastic, disposable syringe. Before the dye was injected, a separate, no. 25-gauge needle was used to enter the pulp chamber through the occlusal aspect of the teeth. This was done to prevent the dye syringe from clogging. Dye was injected into the pulp cavity until it
th e r a m ific a t io n s o f t h e m a in ro o t c a n a l, th e lo c a tio n o f th e a p ic a l f o r a m e n s a n d tr a n s v e r s e a n a sto m o sis, a n d th e f r e q u e n c y o f a p i c a l d e lta s w e r e m a d e in this s tu d y o f 4 0 0 d e c a l c if i e d m a x illa r y f ir s t p r e m o l a r s th a t h a d b e e n i n j e c t e d w ith d y e .
efore endodontic therapy is performed, the dentist should know the configurations of the pulp spaces of the teeth he will treat. All root ca nals should be located so that pulp tissue or necrotic debris can be re moved. Incomplete debridement will lead to almost certain failure. Consequently, a knowledge of the morphology of the pulp cavity is important if the dentist is to suc cessfully treat a tooth endodontically. The literature conveys a di vergence of opinion as to the anatomy of the pulp cavity of the maxillary first premolar. Some re searchers have found that the pres ence of two canals in this tooth oc curs in as many as 98.5% of all cases. Others find the incidence as low as 68.8% (Table l ) .1'6 These discrepan cies are the result of differences in individual anatomy and of classifi cations used. Because of many dis 194 ■ JADA, Vol. 99, August 1979
similarities in selection of speci mens and classification of canal con figurations, the results of most re ports cannot be directly compared with each other. Because the literature is inconclu sive, we decided to conduct a de tailed investigation of the anatomy of root canals of the extracted, human maxillary first premolar. We used a standardized technique that involved examination of transparent specimens.
■ Results of previous studies on morphology of root canals of maxillary first premolar.
T a b le 1
Investigators H ess' BarrettM u elle r1 Pineda and K uttler' G reen ' C arn s and Skidm ore'1
No. in sam ple
O ne can al (%)
T w o can als (%)
T h ree ca n a ls (%)
260 32 130 259 50 100
19.5 28.1 1.5 26.2 8.0 9.0
79.3 68.8 98.5 73.3 92.0 85.0
1.2 3.1 0.5 6.0
A R T IC L E S
could be seen exiting from the apical foramen. Excess dye was wiped from the external surface of the tooth with 5% hydrochloric acid solution. The teeth then were dehydrated in suc cessive solutions of 70%, 95%, and 100% ethyl alcohol for five hours each. This dehydration was neces sary because the clearing agent can not be mixed with water. Finally, the specimens were placed in clear, liq uid plastic casting resin* (the clear ing agent) and were completely cleared within 15 hours.
Table 2 ■ Morphology of maxillary first premolar.
No. teeth No. can als C anals w ith lateral can als Position o f lateral ca n a ls Cervical M iddle A pical Furcation T ra n sv erse a n astom o sis betw een can als P o sition o f tran sv erse an astom o sis C ervical M iddle A pical P o sition o f ap ical foram en Central Lateral A p ical deltas
No.
%
400 788 390
49.5
27 59 423 63 219
4.7 10.3 74.0 11.0 34.2
36 127 56
16.4 58.0 25.6
95 693 25
12.0 88.0 3.2
Results The transparent specimens were ex amined under the dissection micro scope. The number of root canals; the number and location of lateral canals, apical foramens, and trans verse anastomosis; and the fre quency of apical deltas were re corded. These data are summarized in Table 2. The configurations of the canals of the maxillary first premolars exam ined can be classified as one of five types (Fig 1-3). In the type 1 config uration, a single canal is present from the pulp chamber to the apex. In the second type, two separate ca nals leave the pulp chamber but join short of the apex to exit as one canal. In the type 3 configuration, two sep arate and distinct canals stem from the pulp chamber to the apex. In the fourth type, one canal leaves the pulp chamber and divides, before reaching the apex, to form two sepa rate and distinct canals, each with a separate apical foramen. There are three separate and distinct canals from the pulp chamber to the apex in the fifth type of configuration. The percentages of maxillary first premo lars with the preceding canal con figurations are shown in Figure 4. In addition to variations at the apical foramen, significant dif ferences in the form of the canals of the teeth also were present in other regions of the root. In type 2 cases, the two canals leaving the pulp chamber joined at various levels in the root. Six percent merged in the coronal third of the root, 20% joined in the middle third, 58% came to-
Fig 1 ■ M axillary first prem olars with one canal at apex: bottom row , type 1; top row, type 2.
gether in the apical third, and 16% joined at the apical foramen. In 71% of type 4 cases, the canal formed two branches in the middle third of the root. In the remaining 29%, the canal formed two branches in the apical third. In addition to variations in con figurations, the number of roots per tooth was determined. The maxil lary first premolar had one root in 39.5%, two roots in 56.5%, and three roots in 4% of the cases. Figure 5 shows a summary of the relationship
of the configuration of canals to the number of roots.
Discussion Successful root canal therapy cannot be achieved without some under standing of the morphology of the pulp cavity. During the past 100 years, many studies have been made on pulp form. Most of these dis closed many difficulties. Various methods are advocated for anatomic examination of root canals;
V ertu cci-G eg a u ff: ROOT CANAL MORPHOLOGY OF M AXILLARY F IR S T PREMOLAR ■ 195
A R T IC L E S
Fig 3 ■ M axillary first prem olar with three canals at apex, type 5.
Fig 2 ■ M axillary first prem olars with two canals at apex: bottom row, type 3; top row, type 4.
a standardized technique that used transparent specimens was used in this investigation. The technique of clearing specimens has considerable value in studying the anatomy of the root canal because it gives a threedimensional view of the pulp cavity in relation to the exterior of the teeth.7 This technique also makes entering the specimens with instru 196 ■ JADA, Vol. 99, August 1979
ments unnecessary, thereby main taining the original form and rela tionship of the canals. Dentists have been treating maxil lary first premolars for years and have assumed that these teeth have only two root canals. Results of this study indicate that five different canal configurations may be present in this tooth; therefore, the dentist
must always be aware of these pos sibilities when treating maxillary first premolars. When endodontic therapy is per formed, the dentist first should con sider the internal anatomy of the tooth. Before beginning the access preparation, he should study ra diographs from several angles. If, on the direct periapical exposure, he notices the sudden narrowing or disappearance of a root canal, he should realize that the canal di verges at this point into two parts that may either remain separate or merge before reaching the apex. With the information obtained by examining the radiographs and the knowledge of the different possible combinations of internal anatomy, the dentist should be able to deter mine the type of configuration of the canal. This preparatory information will greatly facilitate subsequent treatment. Failure to find and to fill a canal is a causative factor in the breakdown of endodontic treatment.8 When possible, all canals should be lo cated and treated during root canal therapy. An examination of the floor of the pulp chamber offers clues to the type of configuration present. When only one canal exists, it usu ally is located easily in the center of the access preparation. If only one orifice is found, which is not in the center of the preparation, another canal probably is present and should be searched for on the opposite side. Radiographs from various angles, some with a file in place, may be helpful. Also, the relationship of the
A R T IC L E S
Fig 5 ■ Relationship of configurations of canals to num ber o f roots per tooth.
premolars even though, radiographically and clinically, the canal seems to have been obliter ated. Sometimes treatment failure oc curs despite rigid adherence to basic treatment principles.9 When either pain or periapical breakdown is seen after apparently effective endodon tic treatment, the possible presence of an additional canal should be considered before the tooth is con demned or surgical intervention is scheduled. If an apical root resection and reverse fill become necessary, a complication may result if a type 2 configuration is present—surgery may cause a single apical foramen to become two separate foramens. Re sults will be poor if the second canal is not routinely looked for during surgery. Being aware that five possi ble canal configurations can occur in the maxillary first premolar and that possible complications from a surgi cal endodontic procedure can arise should increase the rate of success ful endodontic therapy.
Summary and conclusion
two orifices to each other is impor tant. If they are more than 3 mm apart, the two canals remain sepa rate throughout their length. If less than 3 mm, the two canals usually join. The closer the orifices are to each other, the more coronal the union. In cases in which two canals were joined into one (type 2), the pa latal canal consistently showed straightline access to the apex. Con sequently, type 2 cases are best treated by filling the palatal canal to the apex and the buccal canal to the point where it joins the palatal ca nal. If both canals were enlarged to the apex, an hourglass preparation would result. The point at which the two canals join would be more con stricted than the preparation at the apex. Filling will leave a void in the
apical third of the root and may in vite subsequent failure. Teeth with bifurcations in the middle or apical third of the canal (type 4 cases) may present consider able problems during treatment. Al though one of the two canals, the one most continuous with the large main canal, is usually amenable to adequate enlarging and filling pro cedures, preparing and filling the other canal often is extremely dif ficult. If vital tissue remains in the inadequately treated canal and does not become inflamed, the results may be successful. However, if this untreated canal contains necrotic tissue or is associated with periapi cal pathosis, failure may result. The presence of an unfilled canal may explain some of the endodontic fail ures associated with maxillary first
Four hundred maxillary first premo lars were decalcified, injected with dye, cleared, and studied. The canal configurations were categorized as: 26% had one canal, 69% had two ca nals, and 5% had three canals at the apex. The relationship of canal con figuration to number of roots per tooth was determined. Of the canals studied, 49.5% had lateral canals. They occurred equally in all types of canals, were located mainly in the apical region, and exited from the main canal mostly in a palatal direction. Also, 11% of these canal's extended from the floor of the pulp chamber to the furcation area. An accurate knowledge of the morphology of the pulp cavity is es sential before endodontic procedure can be approached rationally. The frequency with which root canals unite should be considered during enlargement and filling procedures. The dentist also should be aware of the possible existence of bifurcated and double canals if root canal ther
V ertu cci-G eg au ff: ROOT CANAL MORPHOLOGY OF M AXILLARY F IR ST PREMOLAR ■ 197
A R T IC L E S
apy should unexplainably fail. A knowledge of these variations will assist the dentist in reaching conclu sions when diagnosing and treating endodontic cases. *Fibre-Glass Evercoat Co., Inc., Cornell Rd., Cincinnati. Dr. Vertucci is assistant professor, depart m ent of endodontics, and Dr. Gegauff is in structor, department of occlusion and fixed
198 ■ JADA, Vol. 99, August 1979
prosthodontics, College of Dentistry, Univer sity o f Florida, B ox J-436, Gainesville, 32610. Address requests for reprints to Dr. Vertucci. 1. Hess, W. Anatomy of the root canals of the teeth of the perm anent dentition, part I. New York, W illiam Wood and Co., 1925, p 29. 2. Barrett, M.T. The internal anatomy of the teeth with special reference to the pulp with its branches. Dent Cosmos 6 7 :5 8 1 -5 9 2 ,1 9 2 5 . 3. M ueller, A.H. Anatomy of the root canals of the incisors, cuspids and bicuspids of the permanent teeth. JADA 20(8):1361-1386, 1933. 4. Pineda, F., and Kuttler, Y. M esiodistal and buccalingual roentgenographic investiga
tion of 7,275 root canals. Oral Surg 33(1):101110, 1972. 5. Green, D. Double canals in single roots. Oral Surg 35(5):689-696, 1973. 6. Carns, E.J., and Skidmore, A.E. Configura tions and deviations of root canals of m axillary first premolars. Oral Surg 36(6):880-886, 1973. 7. Barker, B.C.; Lockett, B.C.; and Parsons, K.C. T he demonstration of root canal anatomy. Aust Dent J 14(1):37-41, 1969. 8. Stewart, G.G. Evaluation of endodontic results. Dent Clin North Am 11:711-722, 1967. 9. Seltzer, S., and Bender, I.B. Cognitive dis sonance in endodontics. Oral Surg 20(14): 505-516, 1965.
J \¡®j m
ARTICLES
Root canal morphology of the maxillary first premolar Fran k J. V ertucci, DMD Anthony Gegauff, DMD
Methods and materials T h e d e t e r m in a t io n s o f th e n u m b e r o f ro o t c a n a ls , t h e i r ty p e,
For this investigation, we obtained 400 maxillary first premolars from several oral surgery practices. All were adult teeth. The age, sex, and race of the patient and reasons for extraction were not known. Im mediately after extraction, the teeth were fixed in 10% Formalin solution and were then decalcified in 5% hy drochloric acid solution. The teeth then were washed in tap water and placed in a 5% solution of potassium hydroxide for 24 hours. Hematoxy lin dye was injected into pulp cavities with a no. 25-gauge needle on a Luer-Lok plastic, disposable syringe. Before the dye was injected, a separate, no. 25-gauge needle was used to enter the pulp chamber through the occlusal aspect of the teeth. This was done to prevent the dye syringe from clogging. Dye was injected into the pulp cavity until it
th e r a m ific a t io n s o f t h e m a in ro o t c a n a l, th e lo c a tio n o f th e a p ic a l f o r a m e n s a n d tr a n s v e r s e a n a sto m o sis, a n d th e f r e q u e n c y o f a p i c a l d e lta s w e r e m a d e in this s tu d y o f 4 0 0 d e c a l c if i e d m a x illa r y f ir s t p r e m o l a r s th a t h a d b e e n i n j e c t e d w ith d y e .
efore endodontic therapy is performed, the dentist should know the configurations of the pulp spaces of the teeth he will treat. All root ca nals should be located so that pulp tissue or necrotic debris can be re moved. Incomplete debridement will lead to almost certain failure. Consequently, a knowledge of the morphology of the pulp cavity is important if the dentist is to suc cessfully treat a tooth endodontically. The literature conveys a di vergence of opinion as to the anatomy of the pulp cavity of the maxillary first premolar. Some re searchers have found that the pres ence of two canals in this tooth oc curs in as many as 98.5% of all cases. Others find the incidence as low as 68.8% (Table l ) .1'6 These discrepan cies are the result of differences in individual anatomy and of classifi cations used. Because of many dis 194 ■ JADA, Vol. 99, August 1979
similarities in selection of speci mens and classification of canal con figurations, the results of most re ports cannot be directly compared with each other. Because the literature is inconclu sive, we decided to conduct a de tailed investigation of the anatomy of root canals of the extracted, human maxillary first premolar. We used a standardized technique that involved examination of transparent specimens.
■ Results of previous studies on morphology of root canals of maxillary first premolar.
T a b le 1
Investigators H ess' BarrettM u elle r1 Pineda and K uttler' G reen ' C arn s and Skidm ore'1
No. in sam ple
O ne can al (%)
T w o can als (%)
T h ree ca n a ls (%)
260 32 130 259 50 100
19.5 28.1 1.5 26.2 8.0 9.0
79.3 68.8 98.5 73.3 92.0 85.0
1.2 3.1 0.5 6.0
A R T IC L E S
could be seen exiting from the apical foramen. Excess dye was wiped from the external surface of the tooth with 5% hydrochloric acid solution. The teeth then were dehydrated in suc cessive solutions of 70%, 95%, and 100% ethyl alcohol for five hours each. This dehydration was neces sary because the clearing agent can not be mixed with water. Finally, the specimens were placed in clear, liq uid plastic casting resin* (the clear ing agent) and were completely cleared within 15 hours.
Table 2 ■ Morphology of maxillary first premolar.
No. teeth No. can als C anals w ith lateral can als Position o f lateral ca n a ls Cervical M iddle A pical Furcation T ra n sv erse a n astom o sis betw een can als P o sition o f tran sv erse an astom o sis C ervical M iddle A pical P o sition o f ap ical foram en Central Lateral A p ical deltas
No.
%
400 788 390
49.5
27 59 423 63 219
4.7 10.3 74.0 11.0 34.2
36 127 56
16.4 58.0 25.6
95 693 25
12.0 88.0 3.2
Results The transparent specimens were ex amined under the dissection micro scope. The number of root canals; the number and location of lateral canals, apical foramens, and trans verse anastomosis; and the fre quency of apical deltas were re corded. These data are summarized in Table 2. The configurations of the canals of the maxillary first premolars exam ined can be classified as one of five types (Fig 1-3). In the type 1 config uration, a single canal is present from the pulp chamber to the apex. In the second type, two separate ca nals leave the pulp chamber but join short of the apex to exit as one canal. In the type 3 configuration, two sep arate and distinct canals stem from the pulp chamber to the apex. In the fourth type, one canal leaves the pulp chamber and divides, before reaching the apex, to form two sepa rate and distinct canals, each with a separate apical foramen. There are three separate and distinct canals from the pulp chamber to the apex in the fifth type of configuration. The percentages of maxillary first premo lars with the preceding canal con figurations are shown in Figure 4. In addition to variations at the apical foramen, significant dif ferences in the form of the canals of the teeth also were present in other regions of the root. In type 2 cases, the two canals leaving the pulp chamber joined at various levels in the root. Six percent merged in the coronal third of the root, 20% joined in the middle third, 58% came to-
Fig 1 ■ M axillary first prem olars with one canal at apex: bottom row , type 1; top row, type 2.
gether in the apical third, and 16% joined at the apical foramen. In 71% of type 4 cases, the canal formed two branches in the middle third of the root. In the remaining 29%, the canal formed two branches in the apical third. In addition to variations in con figurations, the number of roots per tooth was determined. The maxil lary first premolar had one root in 39.5%, two roots in 56.5%, and three roots in 4% of the cases. Figure 5 shows a summary of the relationship
of the configuration of canals to the number of roots.
Discussion Successful root canal therapy cannot be achieved without some under standing of the morphology of the pulp cavity. During the past 100 years, many studies have been made on pulp form. Most of these dis closed many difficulties. Various methods are advocated for anatomic examination of root canals;
V ertu cci-G eg a u ff: ROOT CANAL MORPHOLOGY OF M AXILLARY F IR S T PREMOLAR ■ 195
A R T IC L E S
Fig 3 ■ M axillary first prem olar with three canals at apex, type 5.
Fig 2 ■ M axillary first prem olars with two canals at apex: bottom row, type 3; top row, type 4.
a standardized technique that used transparent specimens was used in this investigation. The technique of clearing specimens has considerable value in studying the anatomy of the root canal because it gives a threedimensional view of the pulp cavity in relation to the exterior of the teeth.7 This technique also makes entering the specimens with instru 196 ■ JADA, Vol. 99, August 1979
ments unnecessary, thereby main taining the original form and rela tionship of the canals. Dentists have been treating maxil lary first premolars for years and have assumed that these teeth have only two root canals. Results of this study indicate that five different canal configurations may be present in this tooth; therefore, the dentist
must always be aware of these pos sibilities when treating maxillary first premolars. When endodontic therapy is per formed, the dentist first should con sider the internal anatomy of the tooth. Before beginning the access preparation, he should study ra diographs from several angles. If, on the direct periapical exposure, he notices the sudden narrowing or disappearance of a root canal, he should realize that the canal di verges at this point into two parts that may either remain separate or merge before reaching the apex. With the information obtained by examining the radiographs and the knowledge of the different possible combinations of internal anatomy, the dentist should be able to deter mine the type of configuration of the canal. This preparatory information will greatly facilitate subsequent treatment. Failure to find and to fill a canal is a causative factor in the breakdown of endodontic treatment.8 When possible, all canals should be lo cated and treated during root canal therapy. An examination of the floor of the pulp chamber offers clues to the type of configuration present. When only one canal exists, it usu ally is located easily in the center of the access preparation. If only one orifice is found, which is not in the center of the preparation, another canal probably is present and should be searched for on the opposite side. Radiographs from various angles, some with a file in place, may be helpful. Also, the relationship of the
A R T IC L E S
Fig 5 ■ Relationship of configurations of canals to num ber o f roots per tooth.
premolars even though, radiographically and clinically, the canal seems to have been obliter ated. Sometimes treatment failure oc curs despite rigid adherence to basic treatment principles.9 When either pain or periapical breakdown is seen after apparently effective endodon tic treatment, the possible presence of an additional canal should be considered before the tooth is con demned or surgical intervention is scheduled. If an apical root resection and reverse fill become necessary, a complication may result if a type 2 configuration is present—surgery may cause a single apical foramen to become two separate foramens. Re sults will be poor if the second canal is not routinely looked for during surgery. Being aware that five possi ble canal configurations can occur in the maxillary first premolar and that possible complications from a surgi cal endodontic procedure can arise should increase the rate of success ful endodontic therapy.
Summary and conclusion
two orifices to each other is impor tant. If they are more than 3 mm apart, the two canals remain sepa rate throughout their length. If less than 3 mm, the two canals usually join. The closer the orifices are to each other, the more coronal the union. In cases in which two canals were joined into one (type 2), the pa latal canal consistently showed straightline access to the apex. Con sequently, type 2 cases are best treated by filling the palatal canal to the apex and the buccal canal to the point where it joins the palatal ca nal. If both canals were enlarged to the apex, an hourglass preparation would result. The point at which the two canals join would be more con stricted than the preparation at the apex. Filling will leave a void in the
apical third of the root and may in vite subsequent failure. Teeth with bifurcations in the middle or apical third of the canal (type 4 cases) may present consider able problems during treatment. Al though one of the two canals, the one most continuous with the large main canal, is usually amenable to adequate enlarging and filling pro cedures, preparing and filling the other canal often is extremely dif ficult. If vital tissue remains in the inadequately treated canal and does not become inflamed, the results may be successful. However, if this untreated canal contains necrotic tissue or is associated with periapi cal pathosis, failure may result. The presence of an unfilled canal may explain some of the endodontic fail ures associated with maxillary first
Four hundred maxillary first premo lars were decalcified, injected with dye, cleared, and studied. The canal configurations were categorized as: 26% had one canal, 69% had two ca nals, and 5% had three canals at the apex. The relationship of canal con figuration to number of roots per tooth was determined. Of the canals studied, 49.5% had lateral canals. They occurred equally in all types of canals, were located mainly in the apical region, and exited from the main canal mostly in a palatal direction. Also, 11% of these canal's extended from the floor of the pulp chamber to the furcation area. An accurate knowledge of the morphology of the pulp cavity is es sential before endodontic procedure can be approached rationally. The frequency with which root canals unite should be considered during enlargement and filling procedures. The dentist also should be aware of the possible existence of bifurcated and double canals if root canal ther
V ertu cci-G eg au ff: ROOT CANAL MORPHOLOGY OF M AXILLARY F IR ST PREMOLAR ■ 197
A R T IC L E S
apy should unexplainably fail. A knowledge of these variations will assist the dentist in reaching conclu sions when diagnosing and treating endodontic cases. *Fibre-Glass Evercoat Co., Inc., Cornell Rd., Cincinnati. Dr. Vertucci is assistant professor, depart m ent of endodontics, and Dr. Gegauff is in structor, department of occlusion and fixed
198 ■ JADA, Vol. 99, August 1979
prosthodontics, College of Dentistry, Univer sity o f Florida, B ox J-436, Gainesville, 32610. Address requests for reprints to Dr. Vertucci. 1. Hess, W. Anatomy of the root canals of the teeth of the perm anent dentition, part I. New York, W illiam Wood and Co., 1925, p 29. 2. Barrett, M.T. The internal anatomy of the teeth with special reference to the pulp with its branches. Dent Cosmos 6 7 :5 8 1 -5 9 2 ,1 9 2 5 . 3. M ueller, A.H. Anatomy of the root canals of the incisors, cuspids and bicuspids of the permanent teeth. JADA 20(8):1361-1386, 1933. 4. Pineda, F., and Kuttler, Y. M esiodistal and buccalingual roentgenographic investiga
tion of 7,275 root canals. Oral Surg 33(1):101110, 1972. 5. Green, D. Double canals in single roots. Oral Surg 35(5):689-696, 1973. 6. Carns, E.J., and Skidmore, A.E. Configura tions and deviations of root canals of m axillary first premolars. Oral Surg 36(6):880-886, 1973. 7. Barker, B.C.; Lockett, B.C.; and Parsons, K.C. T he demonstration of root canal anatomy. Aust Dent J 14(1):37-41, 1969. 8. Stewart, G.G. Evaluation of endodontic results. Dent Clin North Am 11:711-722, 1967. 9. Seltzer, S., and Bender, I.B. Cognitive dis sonance in endodontics. Oral Surg 20(14): 505-516, 1965.
