0099-2399/90/1707-0338[$03.00/0 JOURNALOF ENDODONTICS Copyright 9 1991 by The American Association of Endodontists

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VOL. 17, NO. 7, JULY 1991

CLINICAL ARTICLE Failure of Endodontically Treated Teeth: Classification and Evaluation Donald E. Vire, DDS, MS

their study. Seidberg (6) reported on a number of cases and commented that failures are not always related to filling canals long or short but that many are related to restorative efforts or lack of them. The present study was designed to determine causes of the ultimate failure: extraction of the tooth after endodontic therapy.

All endodontically treated teeth that were extracted over a 1-yr period in a busy group practice were evaluated for cause of failure. The 116 teeth collected were classified into major failure categories of prosthetic, periodontic, and endodontic origin. Of the teeth, 59.4% were prosthetic failures which were due primarily to crown fracture. Teeth that had been crowned had greater longevity than uncrowned teeth. Periodontal failures constituted 32% of the study. Only 8.6% of the failures were due to endodontic causes, but these failures became evident more quickly than those in the other categories. A classification of failures is presented, and the resuits are analyzed.

MATERIALS AND METHODS Teeth were collected at the time of extraction from a busy military dental clinic which was a large group practice in which all recognized dental specialties were represented. A report form was completed for all extracted teeth which has previously received endodontic therapy. Among the data collected were: a radiograph, which tooth was extracted, the age of the patient, the date endodontics had been completed, the date a crown had been placed, if applicable, and the reason for extraction. Major categories of failure included periodontic, prosthetic, and endodontic. These major categories were then subdivided to accurately define the reason for extraction (Table 1). Over a 1-yr period, 116 teeth which had been endodontically treated were deemed unsuitable for further treatment, extracted, and analyzed for the causes of failure. These teeth represented endodontic treatments completed by numerous practitioners by a variety of techniques. No attempt was made to determine the total percentage of endodontic success, but, rather, the purpose was to determine why endodontic teeth are extracted. It was hoped that this analysis might enhance the ability to retain a greater percentage of endodontieally treated teeth throughout the life of the patient. This study would seem to replicate real-life situations in which teeth are normally lost from the dental arch.

Since the advent of endodontics, practitioners have been concerned about what percentage of success could be expected from treatment. An associated problem exists in deciding the best method of determining success and failure. The most common method of evaluation of success has employed recall radiographs. Ingle and Beveridge (1) reported on the University of Washington School of Dentistry study in which nearly 95% of all treated endodontic cases were successful in using radiographic evaluation. This method has been demonstrated to have drawbacks due to examiner inconsistency and bias as demonstrated by numerous investigators (2-4). Studies demonstrated that different examiners using radiographic evaluation agree on the determination of success less than half of the time. The same examiners will often disagree with themselves upon reevaluation at a later date. Zakariasen et al. (4) pointed out that problems in reliability of radiographic interpretation have been substantiated in branches of both dentistry and medicine. Because of anatomical cavities, maxillary molars yield the greatest percentage of disagreement by this method. In a study of Dutch servicemen, Meeuwissen and Eschen (5) used the definition for failure of endodontic treatment as extraction of the tooth. They concluded that this extraction may be caused by caries, periodontal involvements, and other reasons but did not have that data available for

PROSTHETIC FAILURES This group consisted of 69 teeth representing 59.4% of the total study. Teeth were placed in this category when it was decided that the major clinical situation leading to the need for extraction was related to failure of the restoration or an inability to further restore the tooth. The teeth were almost


Vol. 17, No. 7, July 1991

Failure, Endodontic Teeth


TABLE 1. Extracted endodontically treated teeth--classification

Prosthetic failures Crown fractures Root fractures Traumatic fractures Pathological restoration Periodontic failures Endodontic failures Vertical root failures Instrumentation failures Resorption Overall

No. of Teeth

Percentage of Total

Average Endodontic Elapsed Time (months)

69 54 10 4 1 37 10 5 4 1 116

59.4 46,5 8.6 3.5 .8 32 8.6 4.3 3.5 .8 100

59.4 60,6 65.1 43.0 1.0 65.0 20.6 20.2 17.0 37.0 57.8

TABLE 2. Extracted endodontically treated teeth--distribution No. of Teeth (%) Maxillary Molars 17 (15) Bicuspids 11 (9) Anteriors 31 (27) Mandibular Molars 37 (32) Bicuspids 8 (7) Anteriors 12 (10) Total 116 (100)

Prosthetic Failures (%)

Periodontal Failures (%)

Endodontic Failures (%)

11 (16) 9 (13) 17 (25)

5 (14) 2 (5) 12 (32)

1 (10) -2 (20)

24 (35) 8 (12) -69 (59,4)

6 (16) -12 (32) 37 (32)

7 (70) --10 (8.6)

evenly divided between the arches with 33 mandibular teeth and 36 maxillary teeth (Table 2). The average time between completion of endodontics and extraction was 59.4 months. This group had four subgroups: crown fractures, root fractures, traumatic fractures, and pathologic restoration. The crown fracture subgroup included those teeth that had lost an artificial or natural crown and were deemed nonrestorable because of location of the fracture or carious destruction of the remaining tooth (Fig. 1). This was the largest subgrouping with 54 teeth representing 78.2% of the prosthetic category. The root fracture subgroup consisted of 10 teeth in which fracture of the root had occurred at the level of a post (Figs. 2 and 3). These patients denied a history of a recent traumatic episode. The traumatic fracture subgroup consisted of four teeth in which a recent traumatic episode had caused the tooth to fracture in such a manner that restoration was not feasible. The one case of pathological restoration was a tooth with severe bone destruction from two pins placed far into the furcation coupled with a massive amalgam overhang. The most significant factor of this entire group was that, had the teeth been considered restorable, they would have been retained. The endodontic treatment itself could be considered successful, but the total dental treatment was a failure resulting in extraction. Comparing teeth with and without crowns demonstrated a significant difference in longevity. I f a crown had been placed, the average time before extraction was 87 months. Without a crown, the average prosthetic failure occurred at 50 months.

FIG 1. Uncrowned cuspid demonstrates fracture along the composite restoration.

PERIODONTAL FAILURES This group consisted of 37 teeth representing 32% of the total study. Teeth were placed into this group if bone loss was so extensive as to preclude further periodontal therapy or if prostheodontics was treatment planned but the tooth was not considered able to bear a prosthetic load. These teeth were usually quite mobile, were often symptomatic, and displayed radiographic bone loss. An attempt was made to differentiate



Journal of Endodontics

FIG 2. Tooth with post showing typical angular fracture pivoting on the apical end of the post.

periodontal teeth having the above signs and symptoms from endodontic teeth with similar signs and symptoms. Three of these teeth had been abutments for overdentures, while two of them had experienced root amputation. One tooth was a maxillary lateral incisor with a lingual groove. Distribution between the arches was virtually identical, but there was a greater incidence of anterior teeth (65%) in this group than of anterior teeth in the whole study (37%). The average endodontic elapsed time was 65 months, and the average patient age was 53 years--both greater than the averages for the study as a whole. ENDODONTIC FAILURES This group consisted of 10 teeth representing 8.6% of the total study. Mandibular teeth predominated over maxillary at a ratio of 7:3. Eight of the teeth were molars, and there were two maxillary lateral incisors. This category was further subdivided into three subgroups: five vertical root fractures, four instrumentation failures, such as strips, zips, and incomplete instrumentation, and one case of severe resorption which could have resulted from incomplete obturation. The two lateral incisors were particularly interesting because they both exhibited vertical root fractures (Figs. 4, 5). One tooth had received three previous apical root resections and was referred for a fourth surgery, at which time extraction was recom-

FiG 3. Another case demonstrating typical angular fracture.

mended. The average elapsed time from obturation to extraction in this group was 20.6 months. This is a much shorter time than that in the total sample and indicates that failure of this type will generally be recognized within a 2-year period. DISCUSSION Weine (7) emphasized that a greater number of endodontically treated teeth are lost because of fracture because of improper restorations than because of poor endodontic result. In this sample, close to half of the failures were due to crown fracture. It became c o m m o n to see a remnant of gutta-percha extruding from a mass of decayed broken-down dentin that was unrestorable. Certainly, the lack of pulpal sensation frequently allowed the decay process to continue without the patient seeking dental care. The value of crown placement was further emphasized by the average longevity increasing from 50 months in uncrowned teeth to 87 months in those with crowns. The crown-restored teeth were generally extracted only after the crown was lost and further pathosis developed. With longer lasting crown restorations, the differences in longevity would be even greater. The teeth with root fractures judged to be from prosthetic causes constituted another significant group. Kern et al. (8) stated that specimens prepared by a specific restorative technique fractured in a consistent predictable pattern. The fractures in the present study's group of teeth consistently dem-

Vol. 17, No. 7, July 1991

FiG 4. Extracted tooth with longitudinal fracture believed to be from obturation.

onstrated an angular fracture which seemed to pivot on the apical end of the post. Because not all posts were salvaged, it was impossible to directly correlate technique with the failures. However, analysis did show that the majority of these teeth were bicuspids or other teeth with narrow roots. Patients having a periodontal failure represented what are probably typical periodontal patients. They were older than other patients in the study and had experienced a lot of dental care directed at root retention. This group included root amputations, multiple scalings, and retention of roots for overdentures. This dental care resulted in the greatest post endodontic longevity. It is interesting to note from the distribution table that the majority of teeth in this category were anterior teeth; the other categories were predominantly posterior teeth. An original premise of the study presented here was that true endodontic failures would constitute a large segment of the study. Surprisingly, this was the smallest group, with only 10 cases. These cases were mostly root fractures of instrumentation failures of the mandibular molars. Morris (9) reported a study in which 3.69% of the teeth sustained root fracture attributed to endodontic procedures. The results of that report may correlate with the 4.3% found in this study. He also concluded that posts did not appear to be a reason for vertical root fracture. The posted teeth with root fractures in this study demonstrated such a consistent pattern that the opposite

Failure, Endodontic Teeth


FiG 5. Vertical fracture discovered after three previous surgeries. Fracture is highlighted for photographic purposes.

impression would be drawn. Swartz et al. (10) stated that the mandibular first molar had a significantly lower success rate than the remaining teeth. Mandibular molars in our study constituted approximately one-third of the failures overall and 70% of the endodontic failures. This is particularly significant when considering that Swartz reported mandibular molars to have a frequency of treatment of 17.8%. Therefore, the failure rate of this group is generally at least twice the frequency of treatment. Perhaps the most important observation of this group was that extraction occurred much quicker. This category of failures averaged extraction in less than 2 yr whereas the total sample average was close to 5 yr. Failure of true endodontic origin is less frequent but appears to occur faster than that of other categories. Dr. Vire, Colonel, U. S. Army, is a mentor in Endodontics, Advanced Educational Program in General Dentistry (2 yr), at Fort Bragg, NC. Address requests for reprints to Dr. Donald Vire, 2600 N. Edgewater Drive, Fayetteville, NC 28303.


1. Ingle J, Beveridge E. Endodontics. 2rid ed. Philadelphia: Lea & Febiger, 1976:34. 2. Goldman M, Pearson A, Darzenta N. Endodontic success--who's reading the radiograph? Oral Surg 1972;33:432-6. 3. Goldman M, Pearson A, Darzenta N. Reliability of radiographic interpre-



tations. Oral Surg 1974;38:287-93. 4. Zakariasen K, -Scott D, Jensec J. Endodontic recall radiographs: how reliable is our interpretation of endodontic success or failure and what factors affect our reliability? Oral Surg 1984;57:343-7. 5. Meeuwissen R, Eschen S. Twenty years of endodontic treatment. J Endodon 1983;9:390-3. 6. Seidberg BH. Endodontic success: restorative failure. Boston Univ Endod J 1983;8:8-11.

Journal of Endodontics 7. Weine FS. Endodontic therapy. 3rd ed. St. Louis: C. V. Mosby Co., 1982:4. 8. Kern SB, VonFraunhofer JA, Mueinghoff LA. An in vitro comparison of two dowel and core techniques for endodontically treated molars. J Prosthet Dent 1984;51:508-14. 9. Morris AS. Vertical root fractures. Oral Surg 1990;69:631-5. 10. Swartz D, Skidmore A, Griffin J. Twenty years of endodontic success and failure. J Endodon 1983;9:198-202.

Failure of endodontically treated teeth: classification and evaluation.

All endodontically treated teeth that were extracted over a 1-yr period in a busy group practice were evaluated for cause of failure. The 116 teeth co...
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