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Rapid furcation involvement associated with a devitalizing mandibular first molar
Rapid furcation involvement associated with a devitalizing mandibular first molar A case report Ernest S. Reeh, BSc, DDS,a and Mahmoud UNIVERSITY
OF MlNlUESOTA
SCHOOL
ElDeeb, BDS, MS,h Minneapolis,
Minn.
OF DENTISTRY
Literature reports and journal articles on endodontic-periodontic relationships are numerous. Presented is a brief review of the diagnostic tests, the classification of endoperiodontic lesions, and a clinical report that covers an unusually rapid development of furcation involvement associated with a tooth that became nonvital. (ORAL SURC ORAL MED ORAL PATHOL 1990;69:95-8)
D
iagnosis in endoperiodontic cases is often difficult, but establishing the correct diagnosis and subsequently the correct treatment sequence is necessary for a satisfactory prognosis.1-6 A large number of teeth with a combined endoperiodontic problem are lost, likely becauseof inadequate diagnosis3 Lack of combined therapy, where indicated, will lead to failure.3, 5*6 Appropriate attention to diagnosis by obtaining all pertinent information, including a thorough medical and dental history, pulp testing, periodontal probing, and radiographic survey, is necessary in establishing the correct diagnosis.3% 7 Clinical diagnostic procedures include a wide variety of tests. Pulp vitality testing including hot, cold, electric, and, where indicated, test cavity preparation should be conducted to establish the lack of vitality.2v 7 Pulp tests, unfortunately, may not reveal the nonvitality of a multirooted tooth.3. 6-8If a fistula is present, it should be tracked with a gutta-percha point and a radiograph taken to establish its origin.3 Percussion tests, both occlusally and buccally, may produce symptoms or changes in the sound that could isolate an offending tooth. 3,7 Mobility assessmentand occlusal evaluation may assist in diagnosis or treatment,3y’ and occlusal trauma must be ruled out.7 Transillumination may disclose a fracture or assist in locating subgingival calculus3 Radiographs may reveal calculus, furcal bone loss in lower molars, and Yiraduate student in endodontics. bAssociate Professor and Director Program. 7/15/11313
oi the Graduate
Endodontic
horizontal, vertical, or periapical bone 10ss.~,6-8Periodontal probing and sounding are necessaryto determine the position of attachment and the height of the alveolar bones6-s One of five classifications of endoperiodontic lesions is established after evaluation of clinical testing results. The five categories that are generally used to describe these types of lesions are (1) primary endodontic lesions, (2) primary endodontic lesions with secondary periodontic involvement, (3) primary periodontic lesions, (4) primary periodontic lesions with secondary endodontic involvement, and (5) true combined endoperiodontic lesions.2,4,7 Some authors use three classifications, placing two of the five as subclassifications5* 6 while others choose to use a nine-category system.’ Each of the classifications has its own specific criteria and subsequent treatments. I. Primary endodontic lesions.2. 7 These occur as a result of a nonvital pulp, and consequently pulp testing best confirms the diagnosis. A fistula may be present, or the tooth may drain through the sulcus. If a fistula is present, it should be traced with a guttapercha point and a radiograph taken. The radiograph may also demonstrate normal crestal bone heights mesially and distally, with bone resorption in the furcation area. This condition may be difficult to detect on maxillary molars, as the palatal root may obscure the furcation, but the gutta-percha point will still track to the furcation region. Bone loss may also be seen on one aspect of the root only because of a lateral canal. This lesion is of endodontic origin, and conventional endodontic treatment is generally sufficient for resolution. 95
96
Reeh and ElDeeb
ORAL SURG ORAL
MED
ORAL
January
Fig. 1. Radiograph taken during ment (February 4, 1987).
consultation
appoint-
2. Primary endodontic lesions with secondary periodontic involvement.2s5-7 This is probably the most
common form of combined lesion and results when a primary endodontic lesion has persisted and plaque and calculus have accumulated and resulted in secondary periodontal involvement. Fistulization from the apex or lateral canal, or furcation because of a necrotic pulp drains through some aspect of the ligament space, and plaque can accumulate on the root surface. Endodontic therapy alone is not adequate for complete resolution. Endodontic therapy will resolve the apical lesions and a portion of the lateral lesion, but periodontal therapy including scaling, hygiene instruction, and recall maintenance is required for optimum resolution. 3. Primary periodontic lesions.2s5r 7 Periodontal disease that progresses unchecked through the tooth’s attachment and subsequently involves the apical region, yet the tooth remains vital, is the situation that belongs in this classification. It is important to rule out traumatic occlusion, as these teeth may be primarily or secondarily involved as a result of traumatic occlusion. It is important to remember that these teeth test vital, and subsequently the prognosis depends on the outcome of periodontal therapy. 4. Primary periodontic lesions with secondary endodontic involvement.2, 6 7 This situation exists when
periodontal breakdown has led to pulpal involvement through a lateral canal or, if the periodontal breakdown is sufficiently extensive, through the apical foramen and has lead to devitalization of the pulp. Pulp testing confirms the irreversible state of the pulp or n,,lvvl 1 ‘
nm-r+r .._ _. -sz-.
This
condition
can also result
when
the blood supply to the pulp, via a lateral canal, is severed by a currette, a situation that leads to pulpal involvement. Both periodontal and endodontic ther-
Fig. 2. Periapical radiograph series (March 5, 1987).
from routine
PATHOL
1990
full-mouth
apy are needed to resolve this situation. Unfortunately, teeth that may appear to be hopeless periodontally may be extracted when endodontic therapy might have tipped the balance in favor of a reasonable prognosis in a combined therapy treatment. 5. True combined endo-periodontic lesions.2ss-7
Teeth fit in this classification when pulpal involvement and periodontal involvement occur independently of each other. The simultaneous periapical and crestal bone destruction occur independently and eventually communicate. Pulp tests indicate nonvitality due to pulpal involvement, and periodontal probing indicates substantial loss of tooth .support. Interestingly, the radiographic appearance of these teeth is similar to that of vertical root fracture. The periapical lesions respond to endodontic therapy, but again periodontal therapy is also required. In relation to the importance of the tooth in the arch and involvement of roots, hemisection or extraction may also need to be considered as alternative treatments. CASEREPORT
A 47-year-old white man first reported to the University of Minnesota dental clinic in November, 1982, for an examination. His medical history was noncontributory, with only a history of tobacco use. His dental history indicated a fear of dentistry and a parafunctional habit of which he was aware. Clinical examination revealed no substantial wear facets, moderate plaque in all posterior quadrants, minor recession, toothbrush abrasion, and several carious lesions. The patient had the restorations completed, including one three-quarter crown on the lower right first molar, and underwent a comprehensive hygiene program. The patient was not seen again until February 4, 1987, when he came to the University of Minnesota emergency clinic with a chief complaint of spontaneous pain from the lower right that was exacerbated by hot and cold and could
Volume 69 Number
Rapid furcation
involvement associated with devitalizing first molar
97
1
Fig. 3. Preoperative radiograph involvement (March I 1, 1987).
demonstrating
furcation
be relieved with aspirin. Clinical examination revealed slight sensitivity to palpation of right cervical nodes, no significant pocketing in the affected area, and inconclusive results from pulp testing, with several teeth indicating pulpal symptoms. The periapical radiograph revealed nothing outside of normal limits (Fig. I). The patient was advised that a diagnosis could not be made at that time. He was given appropriate pain medications and a follow-up appointment. The patient failed to come for subsequent appointments but came on March 5 for a routine recall examination. A new full-mouth series of radiographs was taken, and a localized furcation involvement of the lower right first molar was noted (Fig. 2). A consultation was made with an endodontics instructor, and the case was referred to the graduate clinic for treatment. The patient was evaluated in the graduate endodontics clinic on March I 1, at which time he mentioned that his self-prescribed 30 units of vitamin A daily apparently helped. Clinical evaluation demonstrated the patient was maintaining a fair level of oral hygiene and revealed the lower right first molar had a class I mobility, in contrast to the adjacent teeth, which were nonmobile. Pulp testing revealed a sensitivity to horizontal percussion but not to vertical percussion, a significantly delayed response to cold, and no response to electric pulp testing on the lower right first molar. Periodontal probing revealed a class II to 111 furcation involvement of the lower right first molar with an 11 mm pocket on the buccal side. Radiographically a class III furcation involvement could be noted, but no apical lesion was detected (Fig. 3). Conservative root canal treatment was initiated, but no curettage or other periodontal therapy was to be initiated until after the root canal treatment was completed. On April 1 the patient returned to continue with his treatment, at which time the buccal surface of the lower right first molar had a narrow tractlike pocket of 11 mm depth. The root canal treatment was completed on April 15, at which time the buccal pocket was of 5 mm depth and had a fistula on the gingivae buccal to the lower right first mo-
Fig. 4. Radiograph taken after endodontic treatment (April 15, 1987). Note the sealer extruded from the lateral canal in the distal root.
Fig. 5. Radiograph taken during nation (September 18, 1987).
5-month recall exami-
lar. The four canals were obturated, and the patient was instructed to return in 3 months for endodontic reevaluation (Fig. 4). Periodontal treatment was not indicated at the completion of the root canal therapy. Difficulties in contacting the patient resulted in a recall appointment on September 18, 1987. At that time the paricnt mentioned no problems from the tooth and could not remember which tooth had been treated. Clinical examination revealed nothing abnormal: no symptoms, no response to pulp testing, no periodontal pocketing, no detectable mobility, no evidence that a fistula had been present, and occlusion within acceptable limits. A radiograph was taken that indicated good resolution of the furcation (Fig. 5). DISCUSSION Differential
diagnosis
of endoperiodontic
lesions
is
often confusing, yet the treatment sequence depends on the correct diagnosis. ‘, 2, 5 It is important to establish the condition of the pulp as part of the procedure
98
Reeh and ElDeeb
for establishing a diagnosis, as a vital pulp would indicate a condition that may respond to periodontal therapy.s Irreversible pulpitis or nonvital pulps require treatment whether there is an endoperiodontic condition or not. The root canal therapy should be initiated and preferably completed before periodontal therapy, especially if periodontal surgery may be indicated.” 5, * One may also complete endodontic treatment first and then, if resolution of the periodontal condition is inadequate at the time of reevaluation, periodontal therapy should be initiated.5 It is also prudent to remember that bone loss due to endodontic lesions is reversible but bone loss due to periodontal lesions is usually irreversible.4q s Early recognition and treatment are the best measures to ensure the most favorable prognosis.3s 4 The case described belongs to the classification of primary endodontic origin but was rapidly progressing to a secondary periodontic involvement. It was fortunate for the patient that he had had and was able to maintain fair oral hygiene; the prognosis might not have been as favorable had the secondary periodontic involvement occurred to any significant degree. It is interesting to note how rapidly the furcation lesion had developed; the time from the first pulpal symptoms to the presence of the severe furcation involvement was 29 days. In Dr. Ram’s case report4 the furcation involvement took 2.5 months before it was radiographically evident. Another interesting feature was the resolution of the lesion, which changed from a periodontal pocket on the buccal side to a narrow
ORAL SURG ORAL
MED ORAL PATHOL January 1990
tractlike pocket and finally significantly resolved to a fistula present on the buccal gingivae. At the recall evaluation no fistula or periodontal problems were evident. The lesion was also asymmetric. This fact seemed unusual until the time of obturation, when a lateral canal on the mesial aspect of the distal root was observed when sealer was pushed into it during obturation. REFERENCES NW, Trenton NJ. Periodontic-endodontic 1. Chilton ships: a synthesis. ORAL SURG ORAL MED ORAL
relationPATHOL
1972;34:327-8.
Simon JH, Glick DH, Frank AL. The relationship of endodontic-periodontic lesions. J Periodontol 1972;43:202-8. Hiatt WH. Pulpal periodontal disease. J Periodontol 1977; 48:598-609. Ram Z. Endodontic-periodontic interrelationships. ORALSURG ORAL
MED
ORAL
PATHOL
1979;48:84-6.
Rosenberg ES, Garber DA, Rossman LE, Evian CI. Case report: a combined endodontic-periodontic lesion its management and resolution. J Clin Periodontol 1981;8:369-74. 6. Tal H, Kaffe I, Littner MM, Tamse A. Combined periodontic-endodontic lesions: a diagnostic challenge. Quintessence Tnt 1984;12:1257-65. I. Gargiulo AV. Endodontic-periodontic interrelationships: diagnosis and treatment. Dent Clin North Am 1984;28:767-81. 8. Barrington GW. The perio-endo question: differential diagnosis. Dent Clin North Am 1979;23:673-90.
Reprint requests to: Dr. Mahmoud ElDeeb Department of Endodontics University of Minnesota School 515 Delaware St. S.E. Minneapolis, MN 55455
of Dentistry
OF MlNlUESOTA
SCHOOL
ElDeeb, BDS, MS,h Minneapolis,
Minn.
OF DENTISTRY
Literature reports and journal articles on endodontic-periodontic relationships are numerous. Presented is a brief review of the diagnostic tests, the classification of endoperiodontic lesions, and a clinical report that covers an unusually rapid development of furcation involvement associated with a tooth that became nonvital. (ORAL SURC ORAL MED ORAL PATHOL 1990;69:95-8)
D
iagnosis in endoperiodontic cases is often difficult, but establishing the correct diagnosis and subsequently the correct treatment sequence is necessary for a satisfactory prognosis.1-6 A large number of teeth with a combined endoperiodontic problem are lost, likely becauseof inadequate diagnosis3 Lack of combined therapy, where indicated, will lead to failure.3, 5*6 Appropriate attention to diagnosis by obtaining all pertinent information, including a thorough medical and dental history, pulp testing, periodontal probing, and radiographic survey, is necessary in establishing the correct diagnosis.3% 7 Clinical diagnostic procedures include a wide variety of tests. Pulp vitality testing including hot, cold, electric, and, where indicated, test cavity preparation should be conducted to establish the lack of vitality.2v 7 Pulp tests, unfortunately, may not reveal the nonvitality of a multirooted tooth.3. 6-8If a fistula is present, it should be tracked with a gutta-percha point and a radiograph taken to establish its origin.3 Percussion tests, both occlusally and buccally, may produce symptoms or changes in the sound that could isolate an offending tooth. 3,7 Mobility assessmentand occlusal evaluation may assist in diagnosis or treatment,3y’ and occlusal trauma must be ruled out.7 Transillumination may disclose a fracture or assist in locating subgingival calculus3 Radiographs may reveal calculus, furcal bone loss in lower molars, and Yiraduate student in endodontics. bAssociate Professor and Director Program. 7/15/11313
oi the Graduate
Endodontic
horizontal, vertical, or periapical bone 10ss.~,6-8Periodontal probing and sounding are necessaryto determine the position of attachment and the height of the alveolar bones6-s One of five classifications of endoperiodontic lesions is established after evaluation of clinical testing results. The five categories that are generally used to describe these types of lesions are (1) primary endodontic lesions, (2) primary endodontic lesions with secondary periodontic involvement, (3) primary periodontic lesions, (4) primary periodontic lesions with secondary endodontic involvement, and (5) true combined endoperiodontic lesions.2,4,7 Some authors use three classifications, placing two of the five as subclassifications5* 6 while others choose to use a nine-category system.’ Each of the classifications has its own specific criteria and subsequent treatments. I. Primary endodontic lesions.2. 7 These occur as a result of a nonvital pulp, and consequently pulp testing best confirms the diagnosis. A fistula may be present, or the tooth may drain through the sulcus. If a fistula is present, it should be traced with a guttapercha point and a radiograph taken. The radiograph may also demonstrate normal crestal bone heights mesially and distally, with bone resorption in the furcation area. This condition may be difficult to detect on maxillary molars, as the palatal root may obscure the furcation, but the gutta-percha point will still track to the furcation region. Bone loss may also be seen on one aspect of the root only because of a lateral canal. This lesion is of endodontic origin, and conventional endodontic treatment is generally sufficient for resolution. 95
96
Reeh and ElDeeb
ORAL SURG ORAL
MED
ORAL
January
Fig. 1. Radiograph taken during ment (February 4, 1987).
consultation
appoint-
2. Primary endodontic lesions with secondary periodontic involvement.2s5-7 This is probably the most
common form of combined lesion and results when a primary endodontic lesion has persisted and plaque and calculus have accumulated and resulted in secondary periodontal involvement. Fistulization from the apex or lateral canal, or furcation because of a necrotic pulp drains through some aspect of the ligament space, and plaque can accumulate on the root surface. Endodontic therapy alone is not adequate for complete resolution. Endodontic therapy will resolve the apical lesions and a portion of the lateral lesion, but periodontal therapy including scaling, hygiene instruction, and recall maintenance is required for optimum resolution. 3. Primary periodontic lesions.2s5r 7 Periodontal disease that progresses unchecked through the tooth’s attachment and subsequently involves the apical region, yet the tooth remains vital, is the situation that belongs in this classification. It is important to rule out traumatic occlusion, as these teeth may be primarily or secondarily involved as a result of traumatic occlusion. It is important to remember that these teeth test vital, and subsequently the prognosis depends on the outcome of periodontal therapy. 4. Primary periodontic lesions with secondary endodontic involvement.2, 6 7 This situation exists when
periodontal breakdown has led to pulpal involvement through a lateral canal or, if the periodontal breakdown is sufficiently extensive, through the apical foramen and has lead to devitalization of the pulp. Pulp testing confirms the irreversible state of the pulp or n,,lvvl 1 ‘
nm-r+r .._ _. -sz-.
This
condition
can also result
when
the blood supply to the pulp, via a lateral canal, is severed by a currette, a situation that leads to pulpal involvement. Both periodontal and endodontic ther-
Fig. 2. Periapical radiograph series (March 5, 1987).
from routine
PATHOL
1990
full-mouth
apy are needed to resolve this situation. Unfortunately, teeth that may appear to be hopeless periodontally may be extracted when endodontic therapy might have tipped the balance in favor of a reasonable prognosis in a combined therapy treatment. 5. True combined endo-periodontic lesions.2ss-7
Teeth fit in this classification when pulpal involvement and periodontal involvement occur independently of each other. The simultaneous periapical and crestal bone destruction occur independently and eventually communicate. Pulp tests indicate nonvitality due to pulpal involvement, and periodontal probing indicates substantial loss of tooth .support. Interestingly, the radiographic appearance of these teeth is similar to that of vertical root fracture. The periapical lesions respond to endodontic therapy, but again periodontal therapy is also required. In relation to the importance of the tooth in the arch and involvement of roots, hemisection or extraction may also need to be considered as alternative treatments. CASEREPORT
A 47-year-old white man first reported to the University of Minnesota dental clinic in November, 1982, for an examination. His medical history was noncontributory, with only a history of tobacco use. His dental history indicated a fear of dentistry and a parafunctional habit of which he was aware. Clinical examination revealed no substantial wear facets, moderate plaque in all posterior quadrants, minor recession, toothbrush abrasion, and several carious lesions. The patient had the restorations completed, including one three-quarter crown on the lower right first molar, and underwent a comprehensive hygiene program. The patient was not seen again until February 4, 1987, when he came to the University of Minnesota emergency clinic with a chief complaint of spontaneous pain from the lower right that was exacerbated by hot and cold and could
Volume 69 Number
Rapid furcation
involvement associated with devitalizing first molar
97
1
Fig. 3. Preoperative radiograph involvement (March I 1, 1987).
demonstrating
furcation
be relieved with aspirin. Clinical examination revealed slight sensitivity to palpation of right cervical nodes, no significant pocketing in the affected area, and inconclusive results from pulp testing, with several teeth indicating pulpal symptoms. The periapical radiograph revealed nothing outside of normal limits (Fig. I). The patient was advised that a diagnosis could not be made at that time. He was given appropriate pain medications and a follow-up appointment. The patient failed to come for subsequent appointments but came on March 5 for a routine recall examination. A new full-mouth series of radiographs was taken, and a localized furcation involvement of the lower right first molar was noted (Fig. 2). A consultation was made with an endodontics instructor, and the case was referred to the graduate clinic for treatment. The patient was evaluated in the graduate endodontics clinic on March I 1, at which time he mentioned that his self-prescribed 30 units of vitamin A daily apparently helped. Clinical evaluation demonstrated the patient was maintaining a fair level of oral hygiene and revealed the lower right first molar had a class I mobility, in contrast to the adjacent teeth, which were nonmobile. Pulp testing revealed a sensitivity to horizontal percussion but not to vertical percussion, a significantly delayed response to cold, and no response to electric pulp testing on the lower right first molar. Periodontal probing revealed a class II to 111 furcation involvement of the lower right first molar with an 11 mm pocket on the buccal side. Radiographically a class III furcation involvement could be noted, but no apical lesion was detected (Fig. 3). Conservative root canal treatment was initiated, but no curettage or other periodontal therapy was to be initiated until after the root canal treatment was completed. On April 1 the patient returned to continue with his treatment, at which time the buccal surface of the lower right first molar had a narrow tractlike pocket of 11 mm depth. The root canal treatment was completed on April 15, at which time the buccal pocket was of 5 mm depth and had a fistula on the gingivae buccal to the lower right first mo-
Fig. 4. Radiograph taken after endodontic treatment (April 15, 1987). Note the sealer extruded from the lateral canal in the distal root.
Fig. 5. Radiograph taken during nation (September 18, 1987).
5-month recall exami-
lar. The four canals were obturated, and the patient was instructed to return in 3 months for endodontic reevaluation (Fig. 4). Periodontal treatment was not indicated at the completion of the root canal therapy. Difficulties in contacting the patient resulted in a recall appointment on September 18, 1987. At that time the paricnt mentioned no problems from the tooth and could not remember which tooth had been treated. Clinical examination revealed nothing abnormal: no symptoms, no response to pulp testing, no periodontal pocketing, no detectable mobility, no evidence that a fistula had been present, and occlusion within acceptable limits. A radiograph was taken that indicated good resolution of the furcation (Fig. 5). DISCUSSION Differential
diagnosis
of endoperiodontic
lesions
is
often confusing, yet the treatment sequence depends on the correct diagnosis. ‘, 2, 5 It is important to establish the condition of the pulp as part of the procedure
98
Reeh and ElDeeb
for establishing a diagnosis, as a vital pulp would indicate a condition that may respond to periodontal therapy.s Irreversible pulpitis or nonvital pulps require treatment whether there is an endoperiodontic condition or not. The root canal therapy should be initiated and preferably completed before periodontal therapy, especially if periodontal surgery may be indicated.” 5, * One may also complete endodontic treatment first and then, if resolution of the periodontal condition is inadequate at the time of reevaluation, periodontal therapy should be initiated.5 It is also prudent to remember that bone loss due to endodontic lesions is reversible but bone loss due to periodontal lesions is usually irreversible.4q s Early recognition and treatment are the best measures to ensure the most favorable prognosis.3s 4 The case described belongs to the classification of primary endodontic origin but was rapidly progressing to a secondary periodontic involvement. It was fortunate for the patient that he had had and was able to maintain fair oral hygiene; the prognosis might not have been as favorable had the secondary periodontic involvement occurred to any significant degree. It is interesting to note how rapidly the furcation lesion had developed; the time from the first pulpal symptoms to the presence of the severe furcation involvement was 29 days. In Dr. Ram’s case report4 the furcation involvement took 2.5 months before it was radiographically evident. Another interesting feature was the resolution of the lesion, which changed from a periodontal pocket on the buccal side to a narrow
ORAL SURG ORAL
MED ORAL PATHOL January 1990
tractlike pocket and finally significantly resolved to a fistula present on the buccal gingivae. At the recall evaluation no fistula or periodontal problems were evident. The lesion was also asymmetric. This fact seemed unusual until the time of obturation, when a lateral canal on the mesial aspect of the distal root was observed when sealer was pushed into it during obturation. REFERENCES NW, Trenton NJ. Periodontic-endodontic 1. Chilton ships: a synthesis. ORAL SURG ORAL MED ORAL
relationPATHOL
1972;34:327-8.
Simon JH, Glick DH, Frank AL. The relationship of endodontic-periodontic lesions. J Periodontol 1972;43:202-8. Hiatt WH. Pulpal periodontal disease. J Periodontol 1977; 48:598-609. Ram Z. Endodontic-periodontic interrelationships. ORALSURG ORAL
MED
ORAL
PATHOL
1979;48:84-6.
Rosenberg ES, Garber DA, Rossman LE, Evian CI. Case report: a combined endodontic-periodontic lesion its management and resolution. J Clin Periodontol 1981;8:369-74. 6. Tal H, Kaffe I, Littner MM, Tamse A. Combined periodontic-endodontic lesions: a diagnostic challenge. Quintessence Tnt 1984;12:1257-65. I. Gargiulo AV. Endodontic-periodontic interrelationships: diagnosis and treatment. Dent Clin North Am 1984;28:767-81. 8. Barrington GW. The perio-endo question: differential diagnosis. Dent Clin North Am 1979;23:673-90.
Reprint requests to: Dr. Mahmoud ElDeeb Department of Endodontics University of Minnesota School 515 Delaware St. S.E. Minneapolis, MN 55455
of Dentistry