Evaluation of success and failure after endodontic therapy using a glass ionomer cement sealer

0099-2399/95/2107-0384503.00/0 JOURNAL OF ENDODONTICS Copyright © 1995 by The American Association of Endodontists

CLINICAL ARTICLES

Printed in U.S.A. VOL. 21, NO. 7, JULY 1995

Evaluation of Success and Failure after Endodontic Therapy Using a Glass Ionomer Cement Sealer

Shimon Friedman, DMD, Claus L6st, Dr.med.dent., Malaekeh Zarrabian, DDS, and Martin Trope, DMD

The purpose of this multicenter, prospective clinical study was to assess the treatment results following endodontic therapy using a glass ionomer cement sealer (Ketac-Endo) and to relate the results to various clinical factors. A total of 486 teeth were treated by three operators, using the "standardized technique" for canal preparation and either single cone or laterally condensed gutta-percha, in one or multiple treatment sessions. Six to 18 months postoperatively, the treatment results were assessed clinically and radiographically, and related to preoperative, intraoperative, and postoperative factors using a X 2 analysis with 5% level of significance. Of 378 followed-up teeth, there was a 78.3% success, 15.6% incomplete healing, and 6.1% failure. Statistically, differences in the results were related to the number of canals (p < 0.04), primary treatment and retreatment (p < 0.02), pulp vitality (p < 0.001), periapical lesion (p < 0.001), preoperative symptoms (p < 0.003), operative complications (p < 0.001), and absence of restoration (p < 0.03). It was concluded that these treatment results were compatible with those reported in previous studies, and supported the clinical use of Ketac-Endo as an acceptable endodontic sealer.

Numerous studies, representing various endodontic techniques, report that the success rate of endodontic therapy ranges from 48 to 95% (Table 1). One of the prerequisites for successful endodontic therapy is the complete filling of the root canal system, which provides a biological environment for healing of the periradicular tissues (1). The endodontic filling mainly consists of gutta-percha, as the core filling material, and sealer, which is expected to seal the interface between the gutta-percha cones and canal walls. It ap- pears that the choice of sealer may influence the treatment results of endodontic therapy (2).

Recently, a glass ionomer cement endodontic sealer was intro- duced (Ketac-Endo, ESPE Gmbh, Seefeld, Germany) (3). It is biocompatible in bone (4), and exhibits modified working and setting times, no shrinkage upon setting, and superior adaptation to the canal walls and radiopacity as compared with Grossman's sealer (3). In addition, because of its dentinal bonding, Ketac- Endo--filled roots are more resistant to vertical fracture (5). Be- cause of these favorable characteristics, only a single gutta-percha cone is advocated when using Ketac-Endo (3). If required, retreatment is possible with the use of solvent and ultrasonic instrumen- tation (6). The use of a single gutta-percha cone is also likely to prevent vertical root fractures, which may be associated with gutta-percha condensation techniques (7).

The purpose of this multicenter, prospective clinical study was to assess the treatment results after endodontic therapy using Ketac-Endo sealer, and to relate the results to various preoperative, intraoperative, and postoperative clinical factors.

384

MATERIAL AND METHODS

A total of 486 teeth in 401 patients were endodontically treated by three operators, in Tiibingen, Germany (C.L.), Philadelphia, PA (M.T.), and Jerusalem, Israel (S.F.). The study material included a variety of clinical conditions, excluding only teeth in which endodontic therapy was contraindicated (Figs. 1 to 4).

For each tooth, the following preoperative information was recorded: demographic data, tooth location, number of root canals, previous endodontic treatment, clinical signs and symptoms, re- sponses to percussion and vitality tests, and periapical status. Based on these findings, the preoperative condition was classified as one of the following: vital, nonvital, endodontically treated; with or without periapical lesion; and symptomatic or asymptomatic.

All of the teeth were treated using a standardized protocol. Root canals were prepared with hand instruments and 0.5% sodium hypochlorite irrigation. Canals were enlarged according to the standardized technique (3, 8), to 1 mm short of the radiographic apex wherever possible and to a minimum size 35 at the working length. Therapy was completed in single or multiple treatment sessions. In the latter case, a mixture of calcium hydroxide powder and anesthetic solution was placed in the canals, with a Lentulo spiral between appointments. Ketac-Endo was used according to

Vol. 21, No. 7, July 1995 Glass Ionomer Sealer in Endodontic Therapy

TABLE 1. Studies in which treatment results of endodontic therapy were assessed

385

Recall Periapical Retreatments No. of Follow-Up Rate Lesion

Study Cases (yr) (%) (%) (%)

Treatment Results (%)

Success Uncertain Failure

Strindberg, 1956 775* 0.5-10 76 36 38 83 3 14 Grahnen and Hansson, 2019" 4-5 44 19 34 82 6 12

1961 Seltzer et al., 1963 2921" 0.5 40 84 - - 16 Zeldow and Ingle, 1963 89 2 68 86 - - 14 Grossman et al., 1964 432 1-5 23 - - 90 1 9 Storms, 1969 158 1 65 - - 87 - - 13 Harty et al., 1970 1886 0.5-2 60 90 - - 10 Heling and Tamshe, 1970 800 1-5 27 37 - - 70 - - 30 Selden, 1974 4695 1.5 12 76 5 93 - - 7 Adenubi and Rule, 1976 870 0.5-7 38 - - 88 5 7 Jokinen et al., 1978 2459* 2-7 46 66 53 13 34 Kerekes and Tronstad, 1979 647* 3-5 77 34 Some 91 4 5 Bergenhoitz et al., 1979 660* 2 84 42 100 48 30 22 Barbakow et al., 1980 566 ->1 66 34 - - 87 6 7 Morse et al., 1983 585 1 37 95 - - 5 Oliet, 1983 369 1.5 58 89 - - 11 Swartz et al., 1983 1007 1 40 88 - - 12 Pekruhn, 1986 1140 1 81 35 4 91 - - 9 Bystr6m et al., 1987 140 2-5 56 100 85 9 6 Qrstavik et al., 1987 810" 1-4 67 29 - - 95 - - 5 Akerblom and Hasselgren, 64* 2-12 73 25 - - 89 - - 11

1988 Molven and Halse, 1988 541 10-17 50 49 43 80 - - 20 Shah, 1988 132 0.5-2 85 100 84 - - 16 Sj6gren et al., 1990 849* 8-10 46 35 31 91 - - 9 Smith et al., 1993 1518 5-13 54 46 - - 84 - - 16

* Roots, as opposed to teeth in other studies.

FIG 1. Radiographs demonstrating success following endodontic retreatment of both maxillary central incisors. (A) Preoperative view showing immature apices, overextended root canal fillings, and periapical lesions. (B) Root canal fillings with Ketac-Endo and single gutta-percha cones, after apexification with calcium hydroxide for 3 months and healing of lesions. (C) Six months postoperatively, the integrity of the periodontal ligament space is maintained periapically. Teeth are restored with temporary posts and crowns.

the manufacturer's directions. The capsule was activated and mixed in the Capmix vibrator (ESPE) for 10 sec. The sealer was then expressed either directly into the pulp chamber or onto a chilled glass slab, and placed in the canal with a Lentulo spiral. A

single standardized gutta-percha master cone, prefitted to the working length, was seated into the canal with a gentle pumping motion. In 320 teeth treated by two of the operators, no condensation was performed, and only in the canals designated for post-

386 Friedman el al. Journal of EndodonUcs

sions; occurrence of procedural complications, such as perforation, breakage of files, and extrusion of sealer; density and length of the canal filling; and temporary restoration placed. Fillings extending to the radiographic apex or up to 2 mm shorter were recorded as "adequate," as opposed to "underextended" and "overextended" filling.

Six to 18 months after treatment, the patients were recalled, and clinical and radiographic follow-up examinations were performed by the original operators. For teeth examined more than once, only the findings of the final examination were considered. The time elapsed since treatment, clinical signs and symptoms, and type of restoration were recorded as postoperative data. Then, the widest diameters of the periapical lesions in all preoperative and follow-up radiographs were measured by an independent examiner at random, blinded sequence. The lesion size was recorded as the following: smaller than 2 mm, 2 to 5 mm, 6 to 9 mm, and 10 mm or larger.

All of the recorded information was coded and entered into a computerized database. The computer-derived treatment results were programmed as the following combinations of clinical and radiographic findings: (i) Success--absence of clinical signs, symptoms, or periapical radiolucency; slight tenderness to percussion was permitted (Fig. 1). (ii) Incomplete healing--absence of clinical signs and symptoms, including tenderness to percussion, and a decreased size of the periapical lesion (Fig. 2). (iii) Failure-- presence of pain, swelling, or a sinus tract, regardless of the radiographic appearance, or decreased size of the periapical lesion and tenderness to percussion; or development of a periapical lesion or no change in size of the lesion (Fig. 3). Multirooted teeth were assessed according to the root that appeared the worst (Fig. 3). The relation of the treatment results to specific preoperative, intraoperative, and postoperative data was analyzed using )(2, with a 5% level of significance. Various combinations of data were analyzed to indicate the factors that were significantly identified with treatment success or failure.

FIG 2. Radiographs demonstrating incomplete healing following endodontic therapy of mandibular lateral incisor. (,4) Root canal filling with Ketac-Endo and a single gutta-percha cone. There is an extensive periradicular lesion. (B) Eight months postoperatively, the size of the lesion is considerably decreased. The access cavity is still temporarily filled with Intermediate Restorative Material.

placement accessory gutta-percha cones were passively inserted. In the remaining 58 teeth, treated by the third operator, the gutta- percha was laterally condensed in all canals using D-11-T spread- ers, without additionally coating the accessory cones with sealer. Upon completion of obturation, the access cavity was sealed with either Cavit (ESPE), IRM (L. D. Caulk Co., Milford, DE), or glass ionomer cement (Ketac-Fill, ESPE). In several cases, a crown was removed to facilitate retreatment, then temporarily recemented on top of the temporary filling. For each tooth, the following intraoperative information was recorded: the number of treatment ses-

RESULTS

A total of 378 teeth (78%) presented for follow-up examination. The majority of the missing patients (83 teeth) could not be located to be recalled, and the remaining patients did not respond to the recall. Overall, 296 teeth (78.3%) were classified as a treatment success, 59 teeth (15.6%) as incomplete healing, and 23 teeth (6.1%) as a failure.

Distribution of the followed-up teeth by age, sex, and location is presented in Tables 2 and 3, respectively. Distribution by significant preoperative factors and the related treatment results are presented in Table 4. Statistically significant differences in treatment results were found between teeth with single and multiple canals (p < 0.04), primary treatment and retreatment (p < 0.02), vital and nonvital teeth (p < 0.001), teeth with and without periapical lesion (p < 0.001), and teeth with and without symptoms (p < 0.003). Differences related to age (dr = 12, p > 0.6), sex (dr = 2, p > 0.1), tooth location (dr = 10, p > 0.4), and size of the periapical lesion divided into four categories (dr = 6, p > 0.2) were not statistically significant. However, combining lesion sizes to smaller or larger than 2 mm yielded statistically significant differences (p < 0.04).

Distribution of the teeth by significant intraoperative factors and the related treatment results are presented in Table 5. Statistically

Vol. 21, No. 7, July 1995 Glass Ionomer Sealer in Endodontic Therapy 387

FIG 3. Radiographs demonstrating failure following endodontic therapy of first mandibular molar. (A) Preoperative view showing a periapical lesion and external root resorption associated with the distal root. (B) Root canal filling with Ketac-Endo and single gutta-percha cones after intracanal dressing with calcium hydroxide for I month. (C) Eight months postoperatively, there is complete periapical healing of the distal root, but a new lesion developed associated with the mesial root. The tooth is restored with a composite resin inlay.

FiG 4. Radiographs demonstrating incomplete healing following endodontic retreatment of a mandibular first molar. (A) Preoperative view showing poorly filled canals and a second, untreated distal root, a perforation into the furcation and an extensive periradicular lesion. (B) Root canal fillings with Ketac-Endo and single gutta-percha cones. There is extensive extrusion of sealer; the largest observed in all treated teeth. (C) Six months postoperatively, the lesion has decreased in size with evidence of new bone trabeculation in the interradicular area. There is no evidence of resorption of the extruded sealer. The tooth is restored with an amalgam filling.

significant differences were found between teeth in which operative complications occurred, particularly periapical extrusion of the sealer, and teeth without complications (p < 0.001 and p < 0.003, respectively). Differences between teeth treated in one and multiple sessions were statistically borderline (p = 0.052). Differences related to laterally condensed and single-cone gutta-percha (df =

2, p > 0.4), the operator (df = 4, p > 0.2), the temporary filling material (dr = 6, p > 0.7), the filling density (dr = 2, p > 0.07), or the apical extension of the canal filling (df = 4, p > 0.1), were not statistically significant. Combining overextended and underextended fillings as "inadequate" yielded statistically significant differences from the "adequate" fillings (p < 0.05). A general

388 Friedman et al. Journal of Endodontics

TABLE 2. Distribution of the study material by patient age and sex

Sex No. of teeth Age

<19 20-29 30-39 40-49 50-59 60-69 >70

Female 217 (57%) Male 161 (43%)

Total 378 100 %

10 36 63 64 27 7 10 11 22 38 35 29 15 11

21 58 101 99 56 22 21 5.6% 15.3% 26.7% 26.2% 14.8% 5.8% 5.6%

TABLE 3. Distribution of the study material by tooth location

No. of Arch

Teeth

Location in Arch

Anteriors Premolars Molars

Maxilla 212(56%) 64(16.9%) 59(15.6%) 89(23.5%) Mandible 166(44%) 18(4.8%) 48(12.7%) 100(26.5%)

Total 378(100%) 82(21.7%) 107(28.3%) 189(50%)

TABLE 4. Relation of preoperative factors to treatment results following endodontic therapy using Ketac-Endo sealer

No. of Examined Factor

Teeth


Success Incomplete Failure Healing

No. of canals One 144(38%) 85.4 10.4 4.2 Two or more 234(62%) 73.9 18.8 7.3 p < 0.04

Nature of Treatment Primary 250(66%) 82.4 12.0 5.6 Retreatment 128(34%) 70.3 22.7 7.0 p < 0.02

Vitality Vital 108(43%) 93.5 1.9 4.6 Nonvital 142(57%) 73.9 19.7 6.3 p < 0.001

Periapical lesion Absent 169(45 %) 97.0 0 3.0 Present 209(55%) 63.2 28.2 8.6 p < 0.001

In nonvital teeth Absent 29(20%) 93.1 0 6.9 Present 113(80%) 69.0 24.8 6.2 p < 0.001

In retreated teeth Absent 42(20%) 100.0 0 0 Present 86(67%) 55.8 33.7 10.5 p < 0.001

Lesion size -<2 mm 92(44%) 72.8 20.7 6.5 >2 mm 117(56%) 55.6 34.1 10.3 p < 0.04

Symptoms Absent 126(33%) 87.3 11.9 0.8 Present 252(67%) 73.8 17.5 8.7 p < 0.003

observation was that periapically extruded Ketac-Endo was not absorbed by the tissues during the observation period (Fig. 4).

Distribution of the teeth by significant postoperative factors and the related treatment results are presented in Table 6. Eighty-two of the teeth presented for follow-up examination without a final

TABLE 5. Relation of intraoperative factors to treatment results following endodontic therapy using Ketac-Endo sealer


Teeth



Treatment Sessions One 106(28%) 85.8 8.5 5.7 Two or more 272(72%) 75.4 18.4 6.2 p = 0.052

Working length Adequate 306(81%) 79.4 16.0 4.6 Inadequate 72(19%) 73.6 13.9 12.5 p < 0.05

Complications Absent 315(83%) 81.9 13.7 4.4 Present 63(17%) 60.3 25.4 14.3 p < 0.001

Extruded sealer Absent 315(91%) 81.9 13.7 4.4 Present 30(9%) 56.7 26.7 16.6 p < 0.003

TABLE 6. Relation of postoperative factors to treatment results following endodontic therapy using Ketac-Endo sealer


Teeth



Follow-up (months) 6 100(26%) 66.0 22.0 12.0 7-12 255(68%) 81.6 14.5 3.9 >12 23(6%) 95.7 0 4.3 p < 0.003

Final restoration None 4(1%) 50.0 0 50.0 Temporary filling 78(21%) 80.8 14.1 5.1 Definitive filling 90(24%) 80.0 14.4 5.6 Post present 142(37%) 75.4 19.7 4.9 Crown alone 64(17%) 81.3 10.9 7.8 p < 0.03

restoration, having either no filling or still the temporary filling (Fig. 2). Statistically significant differences were found between various observation periods (p < 0.003), and between teeth with and without a restoration (p < 0.03). Differenees related to the type of restoration were not statistically significant (df = 6, p > 0.7).

DISCUSSION

The present study was prospective, in an attempt to standardize treatment protocols and maximize the recall rate. The recall rate of

Vol. 21, No. 7, July 1995

78% compared well with previous studies (Table 1). When patients do not respond to recall, there is always the possibility that the missing teeth represent failures of treatment; therefore, the teeth that are followed-up may not truly represent the study population (9). However, missing teeth from patients who cannot be recalled are not considered as representing a particular treatment result category (9). In this study, 83 of the missing teeth (77%) were from patients who could not be recalled, suggesting that the teeth that were followed-up truly represented the entire study population. The composition of the material included in this study represented the routine treatments performed by the three operators, and in all probability, the treatments performed in any endodontic specialty practice.

When comparing the treatment results observed in this study with those of previous studies, in which other techniques and sealers were used, differences in assessment criteria and composition of the material must be considered (2) (Table 1). As in other studies (8-13), success excluded any evidence of periapical lesion. Tenderness to percussion was permitted, however, considering that it may be frequently associated with conditions unrelated to periapical healing, such as traumatic occlusion, food impaction, or periodontal disease. In a few studies, success included cases in which the periapical lesion decreased (14, 15) or remained the same (16). In this study, these findings were considered incomplete healing and failure, respectively. In addition, the presence of signs and symptoms overruled the radiographic appearance, whereas in several studies only a radiographic evaluation was performed (2, 8, 14, 15). The present study material included 209 teeth (55%) with periapical lesion and 128 (34%) retreatments, both of which are frequently associated with failure of endodontic therapy (8-11, 14-16). In contrast, other studies included <40% teeth with periapical lesions (2, 8-14, 16), and <5% retreatments (8, 10, 14, 15). Finally, the rate of incomplete healing, resulting from the relatively short observation period in the present study, reduced the success rate as compared with studies based on longer observation periods (2, 8, 9, 11-13, 17). Therefore, considering the assessment criteria and composition of the material in this study, the success rate was expected to be lower than in previous studies. Nevertheless, the general distribution of the treatment results was within the range reported in the prognostic studies on endodontic treatment and retreatment. These results supported the clinical application of Ketac-Endo as an acceptable root canal sealer in endodontic therapy.

Regarding demographic and preoperative factors, the insignif- icance of age, sex, and tooth location in this study was in agreement with most previous studies (8-10, 12-15). Teeth with single canals, however, showed a higher success rate than teeth with multiple canals, reflecting the increased probability of failure in muttirooted teeth, which were assessed according to the worst root (9). In several studies, roots, rather than teeth, were observed individually (8-14, 17), a factor that could have contributed to a higher success rate reported in those studies (Table 1).

As previously demonstrated (10, 15), the success rate was lower following retreatment than initial treatment. In an extensive study on retreatment, complete healing was observed in 48% of the retreated roots, incomplete healing in 30%, and failure in 22% (17). Those results are considerably poorer than the ones observed in the present study.

The failure rate in teeth with infected canals and resulting periapical lesions was almost three times higher than in teeth without lesions. This difference was accentuated by the retreatment cases, with 10% failure in the former group, as opposed to 100%

Glass Ionomer Sealer in Endodontic Therapy 389

success in the latter group. In addition, the treatment results were significantly poorer in symptomatic teeth than in asymptomatic teeth, in contrast to previous reports (10, 13). Some of the symptomatic teeth probably had limited pulpat infection, whereas the others had fully established infection with periapical extension. The finding of poorer treatment results in the infected teeth is in agreement with most studies (8-17).

Regarding intraoperative factors, treatment in a single session resulted in a 10% higher success rate than multiple session treatment, supporting previous evidence that single session endodontic therapy is highly successful (10). In teeth with infected canals, however, intracanal dressing with calcium hydroxide between appointments is believed to control the intracanal infection (18). Therefore, for these teeth, multiple session treatment, including intracanal calcium hydroxide dressing, was expected to be more successful than single session treatment. Indeed, the infected teeth treated in multiple sessions, in contrast to the overall trend, showed a 9% higher success rate and almost half the failure rate shown by infected teeth treated in a single session, but the differences were not statistically significant.

The prognosis of endodontic therapy is poorer when the root canal fillings are overextended (9, 12-14, 16) or underextended (13). In this study, the treatment results did not differ significantly for underextended, adequate, or overextended fillings. However, the greatest overextension was only 0.5 mm, and underextension occurred mostly in calcified canals, a condition shown to have an endodontic success rate of 89% (11). Nevertheless, the importance of the apical extension of root canal fillings was confirmed by the lower failure rate of adequate fillings as compared with "inadequate" fillings (8).

Voids in the root canal fillings were observed in 4% of the teeth, which indicated that the technique used when filling the canals with Ketac-Endo was consistent. Avoiding voids in the sealer is very important when obturation relies on the sealer rather than gutta-percha, as in the case of the single cone technique. In this study, however, voids were not associated with an increased failure rate, possibly because the voids were isolated rather than contin- uous, and bordered by areas in which the sealer may have entirely filled the lumen of the canal. In such situations, there may not be communication between the voids and the apex, and propagation of bacteria to the apical area may be prevented. Teeth filled with a single cone or laterally condensed gutta-percha demonstrated comparable treatment results. This finding was expected in view of the superior adaptation of Ketac-Endo to the canal walls (3), and it supported the recommended application technique (3, 6). Avoid- ing condensation of gutta-percha should save time and effort, and vertical root fractures associated with condensation (7) may be prevented.

Complications in therapy decreased the success rate in this study. The most frequent "complication" was extrusion of sealer through the apical foramen, which occurred in 9% of the teeth. Unlike other sealers (19), the extruded Ketac-Endo was not absorbed during the follow-up period. When Ketac-Endo is im- planted in bone, it does not stimulate an osteoclastic response; this allows bone to grow in its immediate proximity without a fibrous tissue interface (4). Therefore, when Ketac-Endo is extruded through the apical foramen, it becomes an "implant" in the periapical tissues, not an irritant. The increased failure rate associated with extruded sealer may, therefore, have been related to other factors such as preoperative periapical lesions. These results do suggest, however, that extrusion of Ketac-Endo should be avoided

390 Friedman et ah

by forming a firm apical stop with minimal apical patency during preparation of the root canal.

In previous studies, the failure rate in teeth with intraradicular posts was either similar (13) or higher (20) than in teeth without posts. The placement of posts may result in failure by decreasing the seal of the remaining canal filling or vertically fracturing the root. In this study, the type of restoration and the presence or absence of a post did not significantly affect the success rate. Ketac-Endo may have sufficiently sealed the canal even after post placement and reinforced the roots against fracture, as observed in vitro (5). A surprising finding was that, several months after endodontic treatment, teeth remaining restored with temporary fillings performed as well as teeth with permanent restorations. Only the four teeth that presented without any restoration demonstrated significantly poorer results. This finding suggested that Ketac-Endo, like other sealers, does not prevent failure of endodontic therapy when coronally the pulp chamber and canals are not sealed.

The authors thank ESPE GmbH for supplying Ketac-Endo and the neces- sary armamentadum for its app)ication; Professor Adele Csima, University of Toronto, for assistance in designing the database; and Jennifer Payne, MSc, University of Toronto, for processing the statistical analysis.

Dr. Friedman is associate professor and head, Department of Endodon- tics, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada. Dr. L6st is professor and chairman, Department of Conservative Dentistry, School of Dentistry, TLibingen University, T(Jbingen, Germany. Dr. Zarrabian is cur- rently practicing in Toronto, Ontario, Canada. Dr. Trope is professor and chair, Department of Endodontics, Faculty of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC. Address requests for reprints to Dr. Shimon Friedman, Department of Endodontics, Faculty of Dentistry, 124 Edward Street, Toronto, Ontario M5G 1G6, Canada.

References

1. Nguyen TN. Obturation of the root canal system. In: Cohen S, Burns RC, eds. Pathways of the pulp. St. Louis: Mosby Year Book, 1991:193-5.

Journal of Endodontics

2. Qrstavik D, Kerekes K, Eriksen HM. Clinical performance of three endodontic sealers. Endod Dent Traumatol 1987;3:178-66.

3. Ray HL, Seltzer S. A new glass ionomer root canal sealer. J Endodon 1991 ;17:598-603.

4. Jonck LM, Grobbelaar CJ, Strating H. Biological evaluation of glass- ionomer cement (Ketac-O) as an interface material in total joint replacement. A screening test. Clin Mater 1989;4:201-24.

5. Trope M, Ray HL. Resistance to fracture of endodontically treated roots. Oral Surg 1992;73:99-102.

6. Friedman S, Moshonov J, Trope M. Efficacy of removing glass inomer cement, zinc oxide eugenol and epoxy resin sealers from retreated root canals. Oral Surg 1992;73:609-12.

7. Dang DA, Walton RE. Vertical root fracture and root distortion: effect of spreader design. J Endodon 1989;15:294-301.

8. Kerekes K, Tronstad L. Long-term results of endodontic treatment performed with a standardized technique. J Endodon 1979;5:83-90.

9. Strindberg LZ. The dependence of the results of pulp therapy on certain factors. An analytic study based on radiographic and clinical follow-up examinations. Acta Odontol Scand 1956;14(suppl 21):1-175.

10. Pekruhn R. The incidence of failure following single-visit endodontic therapy. J Endodon 1986;2:68-72.

11. Akerblom A, Hasselgren G. The prognosis for endodontic treatment of obliterated root canals. J Endodon 1988;14:565-7.

12. Grahnen H, Hansson L. The prognosis of pulp and root canal therapy. A clinical and radiographic follow-up examination. Odontol Revy 1961;12: 146-65.

13. Sjogren U, H~gglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endodon 1990;16:498-504.

14. SeltzerS, BenderlB, TurkenkopfS. Factors affecting successful repair after root canal therapy. J Am Dent Assoc 1963;67:651-62.

15. Selden HS. Pulpoperiapical disease: diagnosis and healing. Oral Surg 1974;37:271-82.

16. Swartz D, Skidmore AE, Griffin JA. Twenty years of endodontic success and failure. J Endodon 1983;9:198-202.

17. Bergenholtz G, Lekholm U, Milthon R, Heden G, Odesjo B, Engstrom B. Retreatment of endodontic fillings. Scand J Dent Res 1979;87:217-24.

18. BystrSm A, Happonen R-P, SjSgren U, Sundqvist G. Healing of periapical lesions of pulpless teeth after endodontic treatment with controlled asepsis. Endod Dent Traumatol 1987;3:58-63.

19. Augsburger RA, Peters DD. Radiographic evaluation of extruded obturation materials. J Endodon 1990;16:492-7.

20. Eckerbom M, Magnusson T, Martinsson T. Prevalence of apical peri- odontitis, crowned teeth and teeth with posts in a Swedish population. Endod Dent Traumatol 1991 ;7:214-20.

A Word to the Wise

S e l f - s t y l e d e t h i c i s t s a re p r o n e t o r a b b i t on a b o u t d i s o b e d i e n c e t o m o r a l l a w i n e v i t a b l y l e a d i n g t o s u b j u g a t i o n

t o l e s s e r p h y s i c a l l aws . W h i c h s o u n d s l i ke a lo t o f g i b b e r i s h . It is m o r e i l l u m i n a t i n g t o s i m p l y o b s e r v e t h a t if,

w h e n w a l k i n g o n i cy p a v e m e n t , w e d i s o b e y t h e l a w s o f p r u d e n c e , w e r isk b e c o m i n g s u b j e c t t o t h e l a w s o f

g rav i t y .

William Cornelius

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Evaluation of success and failure after endodontic therapy using a glass ionomer cement sealer