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Prognosis of Intentional Replantation of Vertically Fractured Roots Reconstructed with Dentin-Bonded Resin
JOURNAL OF ENDODONTICS Copyright © 2004 by The American Association of Endodontists
Printed in U.S.A. VOL. 30, NO. 3, MARCH 2004
Prognosis of Intentional Replantation of Vertically Fractured Roots Reconstructed with Dentin-Bonded Resin Mikako Hayashi, DDS, PhD, Yoshifumi Kinomoto, DDS, PhD, Fumio Takeshige, DDS, PhD, and Shigeyuki Ebisu, DDS, PhD
of vertically fractured roots treated by intentional replantation after reconstructing with dentin-bonded resin was calculated as 83.3% at 12 months and 36.3% at 24 months after replantation. Among 20 fractured roots evaluated, 14 cases were functional in the oral environment. However, an obvious improvement of the periodontal pocket and regeneration of periodontal tissue were observed in just six cases, which were considered necessary criteria for complete success. In the remaining eight cases, periradicular radiolucency or a periodontal pocket remained in spite of the absence of other clinical symptoms. Careful observations are indispensable for these cases, because acute gingival inflammation is likely to recur as a result of infection from a remaining periodontal pocket. Although this newly developed method has the potential to preserve vertically fractured roots, its durability and reliability over long periods of follow-up is still uncertain. Therefore, the present study addressed this gap in knowledge by evaluating whether the intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin is a useful treatment to preserve fractured roots with long-term efficacy.
There is no particular treatment established to preserve vertically fractured teeth. We evaluated the long-term prognosis of the intentional replantation of 26 vertically fractured roots after reconstruction with 4-META/MMA-TBB dentin-bonded resin. Replanted teeth were evaluated according to clinical criteria and radiographic examinations for periods ranging from 4 to 76 months. Eighteen cases were functional and retained, with six fully successful; the others needed further observation. Eight cases failed to respond to treatment because of refracture, recurrence of gingival inflammation, or both. Longevity was calculated as 88.5% at 12 months after replantation, 69.2% at 36 months, and 59.3% at 60 months. All failures occurred in premolar and molar teeth. Longitudinal fractures extending more than 2⁄3 from the cervical portion toward the apex showed significantly shorter longevity compared with fractures within the 2⁄3 area (log-rank test, p ⴝ 0.02). Intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin may be considered for incisors as an alternative to extraction, although the long-term success is not optimal.
MATERIALS AND METHODS Replanted Teeth Twenty-six teeth from 26 patients— 8 incisors, 14 premolars, and 4 molars—were treated at the Department of Conservative Dentistry of Osaka University Dental Hospital between August 1994 and September 2001. All the teeth were diagnosed as vertically fractured, with detection of fracture lines by visual inspection or microscopic or radiographic examinations. Patients, 21 women and 5 men 21 to 73 yr old (Table 1), were followed. Informed consent was obtained from all patients after the nature of the procedure and any possible risks and benefits had been fully explained. A total of nine different surgically experienced operators performed the replantations.
Endodontically treated teeth with vertical root fractures usually result in tooth extraction in single-rooted teeth or surgical root removal in multirooted teeth because this type of fracture presents special difficulties in its treatment and has a poor prognosis. Despite new restorative and surgical methods to preserve vertical fractured roots, the prognosis for these teeth is still far from promising (1–5); no particular treatment has yet been established to preserve vertically fractured teeth. As an alternative method for treating vertical root fractures, we used the following technique: extraction, dentin bonding of the root fragments with adhesive resin, and then intentional replantation. An earlier study of our group reported short-term prognoses of intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin (6). The longevity
Conditions of Replanted Teeth Conditions of the treated teeth were recorded in terms of type and extension of fracture, reconstruction methods, thickness of roots, and operation time, as shown in Table 1. 145
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Journal of Endodontics TABLE 1. Distribution and conditions of replanted teeth
Case no.
Type of teeth
Incisors 1 23 2 9 3 8 4 24 5 7 6 25 7 8 8 9 Premolars 9 13 10 21 11 4 12 5 13 4 14 4 15 13 16 5 17 21 18 5 19 5 20 5 21 5 22 12 Molars 23 31 24 2 25 18 26 31
Method of reconstruction§
Root thickness㛳
Operation time,¶ min
Middle Middle Middle Apical Apical Apical Middle Middle
Sealing Sealing Sealing Adhesion Adhesion Adhesion Adhesion Adhesion
Thick Thick Thick Thin Thin Thin Thick Thick
30 50 30 40 30 40 40 40
Complete Hairline crack Complete Hairline crack Separate Incomplete Incomplete Complete Hairline crack Complete Complete Incomplete Incomplete Complete
Apical Apical Apical Apical Cervical Middle Middle Apical Middle Apical Middle Apical Middle Apical
Adhesion Sealing Adhesion Sealing Adhesion Adhesion Adhesion Adhesion Sealing Adhesion Adhesion Adhesion Adhesion Adhesion
Thick Thin Thin Thin Thin Thick Thick Thin Thin Thin Thin Thin Thin Thin
15 30 10 45 60 40 30 45 40 30 30 20 30 20
Hairline crack Incomplete Hairline crack Complete
Cervical Apical Middle Middle
Sealing Adhesion Sealing Adhesion
Thin Thick Thick Thick
30 60 30 40
Age, yr
Gender
Observation period, months
Result*
Type of fracture†
72 52 46 46 51 46 25 25
M F F F F F F F
57 46 76 55 39 60 25 25
F S F F S S F F
Hairline crack Hairline crack Hairline crack Complete Complete Separate Incomplete Incomplete
67 50 73 57 33 33 47 60 53 60 36 55 38 55
M F M F F F F F F M F F F F
21 49 26 25 44 41 24 6 65 4 20 19 19 16
E S E E F S E E S E F F F F
49 76 45 71
F F F M
45 12 42 47
F E F E
Extension of fracture‡
* S, successful; F, functional; E, extracted. † Hairline crack, only hairline-like vertical cracks were detected; incomplete, incomplete fracture lines were detected; complete, complete fracture lines were detected and the fracture fragments were partially separated; separate, fracture fragments were separated. ‡ Cervical, fracture extended to 1⁄3 depth longitudinally from the cervical portion; middle, fracture extended between 1⁄3 and 2⁄3 from cervical portion toward the apex; apical, fracture extended more than 2⁄3 toward the apex. § Sealing, sealing the crack with resin cement; adhesion, adhering the fracture fragments with resin cement. 㛳 Thick, root with more than half the thickness of the original root; thin, root with less than half the thickness of the original root. ¶ Operation time, the total time the replanted teeth were out of the mouth.
The teeth were classified into four groups according to the type of fracture. In eight cases, only hairline-like vertical cracks were detected, and the fractured fragments did not separate. In seven cases, incomplete fracture lines were detected. In another nine cases, complete fracture lines were detected, and the fractured fragments were partially separated. The remaining two were completely fractured, and the fragments were completely separated. The teeth were classified into three groups according to the extension of the fracture. The cervical fracture group consisted of two cases with the teeth with longitudinal root fractures confined to the cervical 1⁄3 of the root. The middle fracture group consisted of 12 cases with teeth with a root fracture extending to the middle of the root between 1⁄3 and 2⁄3 from the cervical portion toward the apex. The apical fracture group consisted of 12 cases with teeth with a root fracture extending more than 2⁄3 of the way toward the apex or including the apical area. Detailed clinical procedures of the intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin have been described previously (6). In brief, there were two methods for reconstructing fractured teeth. 4-META/MMA-TBB dentin-bonded resin (Super Bond C&B, Sun Medical Co., Kyoto, Japan) was used for reconstruction of all fractures according to the manufacturer’s instructions. For eight cases with only hairline
cracks, the crack was sealed with 4-META/MMA-TBB dentinbonded resin after a shallow preparation of the fracture line. For the other 18 fractures, fragments were adhered with 4-META/MMATBB dentin-bonded resin after the fractured surfaces of the fragments were cleaned with an ultrasonic unit. The fractured teeth were also classified into two groups according to the thickness of the fractured root by inspection or radiographic examination. One group consisted of 11 cases with thick roots that retained more than half of the thickness of the original roots. The other group consisted of 15 cases with thin roots with less than half of the original thickness because of significant canal enlargement for endodontic treatment or preparation for the post core. All the replanted teeth were restored with metallic post cores and full crowns. None served as a bridge abutment.
Evaluation All replanted teeth were evaluated once a week for 1 month after operation, then monthly for 6 months, twice a year for 2 years, and thereafter once a year. Teeth were evaluated according to clinical criteria and radiographically examined at each observation, as described previously (6).
Vol. 30, No. 3, March 2004
Results were graded as success, functional, or extracted. Success was defined as being clinically acceptable in all evaluating characteristics without any clinical symptoms, demonstrating regeneration of the surrounding periodontal tissue radiographically and improving in the periodontal probing depth at the fracture site. A case in which periradicular radiolucency was unchanged or a periodontal pocket remained in a previously detected area was considered functional if it was without other clinical symptoms. A failure needed retreatment or extraction. If a deep pocket greater than 5 mm was found hat had not been detected previously, or the periradicular radiolucency increased, the case was considered a failure. Because all failure cases needed extraction, these were categorized as extracted.
Statistical Analysis The Kaplan-Meier method was used to calculate the longevity of replanted teeth. The type of tooth, age and gender of the patients, method of reconstruction (adhesion of fragments or sealing cracks), extension of a fracture, or thickness of a root were analyzed with the log-rank (Mantel-Cox) test at a 95% level of confidence to determine whether these characteristics had significant effects on the longevity of the replanted teeth.
RESULTS No cases were lost during the evaluation period; of the 26 cases, 18 were functional in the oral environment, with 6 classified as completely successful, because in addition to remaining functional, the periodontal defects were improved and radiographic evidence of regeneration of the periradicular tissue was observed. The other 12 cases were classified as functional because periodontal pockets remained. The remaining eight cases were failures and were extracted. The causes of failure were refracture, abscess formation, or both. Refracture was found in three cases at 4, 6, and 12 months after the replantation, accompanied gingival inflammation. Abscess formation caused by acute gingival inflammation without refracture was observed in the other five cases at 21, 24, 25, 26 and 47 months after the replantation. Failures occurred in six premolar and two molar teeth, but none in incisor teeth. The observation periods ranged between 4 and 76 months, with the average observation period excluding failures 41 months. Longevity was calculated as 88.5% at 12 months after replantation, 79.1% at 24 months, 69.2% at 36 months, and 59.3% at 60 months by the Kaplan-Meier method. Teeth with longitudinal fractures extending more than 2⁄3 from the cervical portion toward the apex showed significantly lower longevity compared with teeth fractured within the 2⁄3 area (logrank test, p ⫽ 0.02). For teeth with fractures extending within a 2⁄3 depth from the cervical area, the longevity was 100% at 12 months, 91.7% at 36 months, and 68.8% at 60 months. In contrast, the longevity was 75.0% at 12 months, 53.6% at 24 months, and 42.9% from 36 to 60 months for the teeth with fractures more than 2⁄3 from the cervical portion toward the apex. Periodontal conditions evaluated by pocket depth measurement and radiographic examination are summarized in Table 2. Obvious improvements of the periodontal pocket and regeneration of surrounding periodontal tissue were detected in 6 of the 18 successful cases.
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TABLE 2. Periodontal conditions of replanted teeth
Case Result* no. Incisors 1 F 2 S 3 F 4 F 5 S 6 S 7 F 8 F Premolars 9 E 10 S 11 E 12 E 13 F 14 S 15 E 16 E 17 S 18 E 19 F 20 F 21 F 22 F Molars 23 F 24 E 25 F 26 E
Maximum depth of periodontal probing along fracture line, mm At time of initial examination
At time of latest follow-up
X-ray appearance of bone defect†
9 ⬎10 ⬎10 ⬎10 8 ⬎10 3 3
8 5 3 6 2 2 3 3
U R U U R R W‡ W‡
8 9 ⬎10 5 3 7 5 ⬎10 3 ⬎10 8 7 7 ⬎10
⬎10 2 7 ⬎10 3 3 9 7 3 ⬎10 5 4 6 5
W R W W U R W W R W U U U U
7 9 ⬎10 8
5 9 3 7
U W U W
* S, successful; F, functional; E, extracted. † R, regenerated; U, unchanged; W, changed worse. ‡ Root resorption caused by ankylosis was observed.
Root resorption caused by ankylosis was detected in two upper central incisors (7 and 8 in Table 1). These incisors had been fractured in a traumatic accident, and replantation with reconstruction of fractured roots was performed 2 weeks after the injury. Ankylosis was first diagnosed by an unusual percussion sound 3 months after replantation, and root resorption was detected radiographically in both incisors at 6 months after replantation. These were graded functional because they showed no clinical symptoms or a periodontal pocket greater than 3 mm, even though the resorption had been gradually progressing. Age and gender of patients, type of fracture, root thickness, adhesion methods, and operation time did not show significant effects on longevity. DISCUSSION This study provides a long-term follow-up of the intentional replantation of vertically fractured roots after reconstruction with 4-META/MMA-TBB dentin-bonded resin. No failures were found in vertically fractured incisors treated with this method. All failures were restricted to premolars and molars. The strong occlusal force in posterior teeth (7) may be a crucial factor that influences the prognosis of the reconstructed roots. Further, incisors, because of their location and morphology, are generally considered to be easier for maintenance of gingival health than molars (8). Hence,
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a more predictable long-term prognosis of replantation with reconstruction for vertically fractured roots can be expected in incisors. Two functional cases from those previously observed over the short term failed at 26 and 47 months after replantation because of recurrence of gingival inflammation. In contrast, no refracture has been detected after this time. The majority of cases functional in the short-term observations maintained long-term function, even though a periodontal pocket remained in a previously detected area. This finding suggests that with well-controlled oral hygiene, replanted fractured teeth may be able to maintain their function in conditions of no refracture for 2 years after replantation. Among the eight failures, refractures were found in three cases within a year after treatment. A sufficiently high bonding strength of the dentin-bonded resin cement is a critical requirement for long-term success of reconstructed roots. A prompt curing reaction of resin cement that can produce high bonding strength immediately after curing may also be an important characteristic of the resin cement required for reconstruction, because a reconstructed root has to endure moisture and occlusal force immediately on replantation. According to the manufacturer’s instructions, 4-META/TBB-MMA resin used in the present study takes approximately 5 min for the initial chemical curing reaction, which is relatively slower than that of light-cured resin cement. Further investigations are required to evaluate the prognosis of fractured roots reconstructed by resin cements with other types of curing systems. All patients who failed to respond sought treatment for inflammation caused by infection from a persistent periodontal pocket. Further, a periodontal pocket in a previously detected area remained in the 12 functional cases. Thus, periodontal pockets along fractures reconstructed with dentin-bonding resin remain a problem that needs to be addressed in future studies. Although we tried to keep the width of the resin cement in an adhesive area to a minimum, this procedure has not been effective in eliminating all periodontal pockets. Rotation of reconstructed roots at replantation may be an option to promote the generation of periodontal tissue surrounding a fracture line. However, indications for replantation rotating a reconstructed root have limitations because of root curvatures or the existence of anatomical organs such as the maxillary sinus or mandibular canal. Clinicians should be aware of the importance of early extraction of vertical root fractures based on an early, accurate diagnosis, because early extraction of fractured roots, before buccal or lingual bone plates are destroyed, may allow successful implantation. When implantation is one of the treatment options for a patient, the benefit of early extraction of a fractured tooth should be considered before selecting the intentional replantation with reconstruction. Biocompatibility of 4-META/TBB-MMA resin for dental pulp tissue and periodontal tissues has been reported (9 –11) and has been considered sufficient for use in soft tissues in procedures such as direct pulp capping, retrofilling in root end surgery, and repair of root perforations. It has been reported that the 4-META/TBBMMA resin component combined with bone morphogenetic protein may accelerate wound healing of damaged pulp tissue (12). Bone morphogenetic protein-containing 4-META/TBB-MMA resin may accelerate the regeneration of damaged periodontal tissue when it is applied to the reconstruction of a fractured root as an adhesive material. A modern approach using bioengineering techniques may constitute a breakthrough method to promote promising long-term prognoses of intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin. As previously reported (6), the longevity of the apical fracture group was shorter than that of the middle fracture group. The
Journal of Endodontics
occlusal force may be transmitted in exactly the same direction as the previous fracture when the fracture runs through the whole root longitudinally, including the apical area. Recurrence of the fracture could then be induced if the adhesion of the fractured fragments reaches a limit of sustainability. The root resorption caused by ankylosis observed in the two incisors may be a result of burnishing the root surface during the extractions of the fractured teeth. It was impossible to remove the fractured roots without damage to the periodontium, because the freshly fractured roots were tightly held by the alveolar bone without any defects. Although root resorption was not detected in the remaining replanted roots, further follow-up is indispensable, because it is still possible that negligibly small root resorption or root resorption that existed in a radiographically undetectable area may progress afterward. Prognoses for autotransplantation of nonfractured teeth have been reported, and success rates of more than 95% (13–15) allow this treatment to be a reliable option for restoring missing teeth. From a comparison of the results of the present study with those of the autotransplantation of nonfractured teeth, it was concluded that intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin has benefits as a treatment alternative, especially for incisor teeth. This study was supported in part by a Grant-in-Aid for Scientific Research (No. 14571812) from the Japan Society for the Promotion of Science. Dr. Hayashi, Dr. Kinomoto, Dr. Takeshige, and Dr. Ebisu are affiliated with the Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Osaka, Japan. Address requests for reprints to Dr. Hayashi, Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. E-mail: [email protected].
References 1. Trope M, Rosenberg ES. Multidisciplinary approach to the repair of vertically fractured teeth. J Endodon 1992;18:460 –3. 2. Selden HS. Repair of incomplete vertical root fractures in endodontically treated teeth—in vivo trials. J Endodon 1996;22:426 –9. 3. Pitts DL, Natkin E. Diagnosis and treatment of vertical root fractures. J Endodon 1983;9:338 – 46. 4. Oliet S. Treating vertical fractures. J Endodon 1984;10:391– 6. 5. Testori T, Badino M, Castagnola M. Vertical root fractures in endodontically treated teeth: a clinical survey of 36 cases. J Endodon 1993;19:87–91. 6. Hayashi M, Kinomoto Y, Miura M, Sato I, Takeshige F, Ebisu S. Shortterm evaluation of intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin. J Endodon 2002;28:120 – 4. 7. Proffit WR, Fields HW, Nixon WL. Occlusal forces in normal and long face adults. J Dent Res 1983;62:566 –70. 8. Carranza FA, Newman MG. Distribution of disease in different areas of mouth. In: Clinical periodontology. 8th ed. Philadelphia, PA: Saunders, 1996: 77–9. 9. Nakamura M, Inoue T, Shimono M. Immunohistochemical study of dental pulp applied with 4-META/MMA-TBB adhesive resin after pulpotomy. J Biomed Mater Res 2000;51:241– 8. 10. Kitasako Y, Inokoshi S, Tagami J. Effects of direct resin pulp capping techniques on short-term response of mechanically exposed pulps. J Dent 1999;27:257– 63. 11. Noguchi H, Sugaya T, Kato H. Treatment of vertically fractured root by cohesion, part 1: evaluations of cytotoxicity of adhesive resin cement with cultured periodontal ligament cells. Jpn J Cons Dent 1997;40:1445–52. 12. Inoue T, Matsuzaka K, Murakami S, Koike Y, Miyakoshi S, Shimono M. An experimental study on the osteogenesis of BMP-containing 4-META/ MMA-TBB adhesive resin. Jpn J Cons Dent 2002;45:434 – 40. 13. Andreasen JO, Hjorting-Hansen E, Jolst O. A clinical and radiographic study of 76 autotransplanted third molars. Scand J Dent Res 1970;78:512–23. 14. Kristerson L, Johansson LA, Kisch J, Stadler LE. Autotransplantation of third molars as treatment in advanced periodontal disease. J Clin Periodontol 1991;18:521– 8. 15. Akiyama Y, Fukuda H, Hashimoto K. A clinical and radiographic study of 25 autotransplanted third molars. J Oral Rehabil 1998;25:640 – 4.
Printed in U.S.A. VOL. 30, NO. 3, MARCH 2004
Prognosis of Intentional Replantation of Vertically Fractured Roots Reconstructed with Dentin-Bonded Resin Mikako Hayashi, DDS, PhD, Yoshifumi Kinomoto, DDS, PhD, Fumio Takeshige, DDS, PhD, and Shigeyuki Ebisu, DDS, PhD
of vertically fractured roots treated by intentional replantation after reconstructing with dentin-bonded resin was calculated as 83.3% at 12 months and 36.3% at 24 months after replantation. Among 20 fractured roots evaluated, 14 cases were functional in the oral environment. However, an obvious improvement of the periodontal pocket and regeneration of periodontal tissue were observed in just six cases, which were considered necessary criteria for complete success. In the remaining eight cases, periradicular radiolucency or a periodontal pocket remained in spite of the absence of other clinical symptoms. Careful observations are indispensable for these cases, because acute gingival inflammation is likely to recur as a result of infection from a remaining periodontal pocket. Although this newly developed method has the potential to preserve vertically fractured roots, its durability and reliability over long periods of follow-up is still uncertain. Therefore, the present study addressed this gap in knowledge by evaluating whether the intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin is a useful treatment to preserve fractured roots with long-term efficacy.
There is no particular treatment established to preserve vertically fractured teeth. We evaluated the long-term prognosis of the intentional replantation of 26 vertically fractured roots after reconstruction with 4-META/MMA-TBB dentin-bonded resin. Replanted teeth were evaluated according to clinical criteria and radiographic examinations for periods ranging from 4 to 76 months. Eighteen cases were functional and retained, with six fully successful; the others needed further observation. Eight cases failed to respond to treatment because of refracture, recurrence of gingival inflammation, or both. Longevity was calculated as 88.5% at 12 months after replantation, 69.2% at 36 months, and 59.3% at 60 months. All failures occurred in premolar and molar teeth. Longitudinal fractures extending more than 2⁄3 from the cervical portion toward the apex showed significantly shorter longevity compared with fractures within the 2⁄3 area (log-rank test, p ⴝ 0.02). Intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin may be considered for incisors as an alternative to extraction, although the long-term success is not optimal.
MATERIALS AND METHODS Replanted Teeth Twenty-six teeth from 26 patients— 8 incisors, 14 premolars, and 4 molars—were treated at the Department of Conservative Dentistry of Osaka University Dental Hospital between August 1994 and September 2001. All the teeth were diagnosed as vertically fractured, with detection of fracture lines by visual inspection or microscopic or radiographic examinations. Patients, 21 women and 5 men 21 to 73 yr old (Table 1), were followed. Informed consent was obtained from all patients after the nature of the procedure and any possible risks and benefits had been fully explained. A total of nine different surgically experienced operators performed the replantations.
Endodontically treated teeth with vertical root fractures usually result in tooth extraction in single-rooted teeth or surgical root removal in multirooted teeth because this type of fracture presents special difficulties in its treatment and has a poor prognosis. Despite new restorative and surgical methods to preserve vertical fractured roots, the prognosis for these teeth is still far from promising (1–5); no particular treatment has yet been established to preserve vertically fractured teeth. As an alternative method for treating vertical root fractures, we used the following technique: extraction, dentin bonding of the root fragments with adhesive resin, and then intentional replantation. An earlier study of our group reported short-term prognoses of intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin (6). The longevity
Conditions of Replanted Teeth Conditions of the treated teeth were recorded in terms of type and extension of fracture, reconstruction methods, thickness of roots, and operation time, as shown in Table 1. 145
146
Hayashi et al.
Journal of Endodontics TABLE 1. Distribution and conditions of replanted teeth
Case no.
Type of teeth
Incisors 1 23 2 9 3 8 4 24 5 7 6 25 7 8 8 9 Premolars 9 13 10 21 11 4 12 5 13 4 14 4 15 13 16 5 17 21 18 5 19 5 20 5 21 5 22 12 Molars 23 31 24 2 25 18 26 31
Method of reconstruction§
Root thickness㛳
Operation time,¶ min
Middle Middle Middle Apical Apical Apical Middle Middle
Sealing Sealing Sealing Adhesion Adhesion Adhesion Adhesion Adhesion
Thick Thick Thick Thin Thin Thin Thick Thick
30 50 30 40 30 40 40 40
Complete Hairline crack Complete Hairline crack Separate Incomplete Incomplete Complete Hairline crack Complete Complete Incomplete Incomplete Complete
Apical Apical Apical Apical Cervical Middle Middle Apical Middle Apical Middle Apical Middle Apical
Adhesion Sealing Adhesion Sealing Adhesion Adhesion Adhesion Adhesion Sealing Adhesion Adhesion Adhesion Adhesion Adhesion
Thick Thin Thin Thin Thin Thick Thick Thin Thin Thin Thin Thin Thin Thin
15 30 10 45 60 40 30 45 40 30 30 20 30 20
Hairline crack Incomplete Hairline crack Complete
Cervical Apical Middle Middle
Sealing Adhesion Sealing Adhesion
Thin Thick Thick Thick
30 60 30 40
Age, yr
Gender
Observation period, months
Result*
Type of fracture†
72 52 46 46 51 46 25 25
M F F F F F F F
57 46 76 55 39 60 25 25
F S F F S S F F
Hairline crack Hairline crack Hairline crack Complete Complete Separate Incomplete Incomplete
67 50 73 57 33 33 47 60 53 60 36 55 38 55
M F M F F F F F F M F F F F
21 49 26 25 44 41 24 6 65 4 20 19 19 16
E S E E F S E E S E F F F F
49 76 45 71
F F F M
45 12 42 47
F E F E
Extension of fracture‡
* S, successful; F, functional; E, extracted. † Hairline crack, only hairline-like vertical cracks were detected; incomplete, incomplete fracture lines were detected; complete, complete fracture lines were detected and the fracture fragments were partially separated; separate, fracture fragments were separated. ‡ Cervical, fracture extended to 1⁄3 depth longitudinally from the cervical portion; middle, fracture extended between 1⁄3 and 2⁄3 from cervical portion toward the apex; apical, fracture extended more than 2⁄3 toward the apex. § Sealing, sealing the crack with resin cement; adhesion, adhering the fracture fragments with resin cement. 㛳 Thick, root with more than half the thickness of the original root; thin, root with less than half the thickness of the original root. ¶ Operation time, the total time the replanted teeth were out of the mouth.
The teeth were classified into four groups according to the type of fracture. In eight cases, only hairline-like vertical cracks were detected, and the fractured fragments did not separate. In seven cases, incomplete fracture lines were detected. In another nine cases, complete fracture lines were detected, and the fractured fragments were partially separated. The remaining two were completely fractured, and the fragments were completely separated. The teeth were classified into three groups according to the extension of the fracture. The cervical fracture group consisted of two cases with the teeth with longitudinal root fractures confined to the cervical 1⁄3 of the root. The middle fracture group consisted of 12 cases with teeth with a root fracture extending to the middle of the root between 1⁄3 and 2⁄3 from the cervical portion toward the apex. The apical fracture group consisted of 12 cases with teeth with a root fracture extending more than 2⁄3 of the way toward the apex or including the apical area. Detailed clinical procedures of the intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin have been described previously (6). In brief, there were two methods for reconstructing fractured teeth. 4-META/MMA-TBB dentin-bonded resin (Super Bond C&B, Sun Medical Co., Kyoto, Japan) was used for reconstruction of all fractures according to the manufacturer’s instructions. For eight cases with only hairline
cracks, the crack was sealed with 4-META/MMA-TBB dentinbonded resin after a shallow preparation of the fracture line. For the other 18 fractures, fragments were adhered with 4-META/MMATBB dentin-bonded resin after the fractured surfaces of the fragments were cleaned with an ultrasonic unit. The fractured teeth were also classified into two groups according to the thickness of the fractured root by inspection or radiographic examination. One group consisted of 11 cases with thick roots that retained more than half of the thickness of the original roots. The other group consisted of 15 cases with thin roots with less than half of the original thickness because of significant canal enlargement for endodontic treatment or preparation for the post core. All the replanted teeth were restored with metallic post cores and full crowns. None served as a bridge abutment.
Evaluation All replanted teeth were evaluated once a week for 1 month after operation, then monthly for 6 months, twice a year for 2 years, and thereafter once a year. Teeth were evaluated according to clinical criteria and radiographically examined at each observation, as described previously (6).
Vol. 30, No. 3, March 2004
Results were graded as success, functional, or extracted. Success was defined as being clinically acceptable in all evaluating characteristics without any clinical symptoms, demonstrating regeneration of the surrounding periodontal tissue radiographically and improving in the periodontal probing depth at the fracture site. A case in which periradicular radiolucency was unchanged or a periodontal pocket remained in a previously detected area was considered functional if it was without other clinical symptoms. A failure needed retreatment or extraction. If a deep pocket greater than 5 mm was found hat had not been detected previously, or the periradicular radiolucency increased, the case was considered a failure. Because all failure cases needed extraction, these were categorized as extracted.
Statistical Analysis The Kaplan-Meier method was used to calculate the longevity of replanted teeth. The type of tooth, age and gender of the patients, method of reconstruction (adhesion of fragments or sealing cracks), extension of a fracture, or thickness of a root were analyzed with the log-rank (Mantel-Cox) test at a 95% level of confidence to determine whether these characteristics had significant effects on the longevity of the replanted teeth.
RESULTS No cases were lost during the evaluation period; of the 26 cases, 18 were functional in the oral environment, with 6 classified as completely successful, because in addition to remaining functional, the periodontal defects were improved and radiographic evidence of regeneration of the periradicular tissue was observed. The other 12 cases were classified as functional because periodontal pockets remained. The remaining eight cases were failures and were extracted. The causes of failure were refracture, abscess formation, or both. Refracture was found in three cases at 4, 6, and 12 months after the replantation, accompanied gingival inflammation. Abscess formation caused by acute gingival inflammation without refracture was observed in the other five cases at 21, 24, 25, 26 and 47 months after the replantation. Failures occurred in six premolar and two molar teeth, but none in incisor teeth. The observation periods ranged between 4 and 76 months, with the average observation period excluding failures 41 months. Longevity was calculated as 88.5% at 12 months after replantation, 79.1% at 24 months, 69.2% at 36 months, and 59.3% at 60 months by the Kaplan-Meier method. Teeth with longitudinal fractures extending more than 2⁄3 from the cervical portion toward the apex showed significantly lower longevity compared with teeth fractured within the 2⁄3 area (logrank test, p ⫽ 0.02). For teeth with fractures extending within a 2⁄3 depth from the cervical area, the longevity was 100% at 12 months, 91.7% at 36 months, and 68.8% at 60 months. In contrast, the longevity was 75.0% at 12 months, 53.6% at 24 months, and 42.9% from 36 to 60 months for the teeth with fractures more than 2⁄3 from the cervical portion toward the apex. Periodontal conditions evaluated by pocket depth measurement and radiographic examination are summarized in Table 2. Obvious improvements of the periodontal pocket and regeneration of surrounding periodontal tissue were detected in 6 of the 18 successful cases.
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TABLE 2. Periodontal conditions of replanted teeth
Case Result* no. Incisors 1 F 2 S 3 F 4 F 5 S 6 S 7 F 8 F Premolars 9 E 10 S 11 E 12 E 13 F 14 S 15 E 16 E 17 S 18 E 19 F 20 F 21 F 22 F Molars 23 F 24 E 25 F 26 E
Maximum depth of periodontal probing along fracture line, mm At time of initial examination
At time of latest follow-up
X-ray appearance of bone defect†
9 ⬎10 ⬎10 ⬎10 8 ⬎10 3 3
8 5 3 6 2 2 3 3
U R U U R R W‡ W‡
8 9 ⬎10 5 3 7 5 ⬎10 3 ⬎10 8 7 7 ⬎10
⬎10 2 7 ⬎10 3 3 9 7 3 ⬎10 5 4 6 5
W R W W U R W W R W U U U U
7 9 ⬎10 8
5 9 3 7
U W U W
* S, successful; F, functional; E, extracted. † R, regenerated; U, unchanged; W, changed worse. ‡ Root resorption caused by ankylosis was observed.
Root resorption caused by ankylosis was detected in two upper central incisors (7 and 8 in Table 1). These incisors had been fractured in a traumatic accident, and replantation with reconstruction of fractured roots was performed 2 weeks after the injury. Ankylosis was first diagnosed by an unusual percussion sound 3 months after replantation, and root resorption was detected radiographically in both incisors at 6 months after replantation. These were graded functional because they showed no clinical symptoms or a periodontal pocket greater than 3 mm, even though the resorption had been gradually progressing. Age and gender of patients, type of fracture, root thickness, adhesion methods, and operation time did not show significant effects on longevity. DISCUSSION This study provides a long-term follow-up of the intentional replantation of vertically fractured roots after reconstruction with 4-META/MMA-TBB dentin-bonded resin. No failures were found in vertically fractured incisors treated with this method. All failures were restricted to premolars and molars. The strong occlusal force in posterior teeth (7) may be a crucial factor that influences the prognosis of the reconstructed roots. Further, incisors, because of their location and morphology, are generally considered to be easier for maintenance of gingival health than molars (8). Hence,
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a more predictable long-term prognosis of replantation with reconstruction for vertically fractured roots can be expected in incisors. Two functional cases from those previously observed over the short term failed at 26 and 47 months after replantation because of recurrence of gingival inflammation. In contrast, no refracture has been detected after this time. The majority of cases functional in the short-term observations maintained long-term function, even though a periodontal pocket remained in a previously detected area. This finding suggests that with well-controlled oral hygiene, replanted fractured teeth may be able to maintain their function in conditions of no refracture for 2 years after replantation. Among the eight failures, refractures were found in three cases within a year after treatment. A sufficiently high bonding strength of the dentin-bonded resin cement is a critical requirement for long-term success of reconstructed roots. A prompt curing reaction of resin cement that can produce high bonding strength immediately after curing may also be an important characteristic of the resin cement required for reconstruction, because a reconstructed root has to endure moisture and occlusal force immediately on replantation. According to the manufacturer’s instructions, 4-META/TBB-MMA resin used in the present study takes approximately 5 min for the initial chemical curing reaction, which is relatively slower than that of light-cured resin cement. Further investigations are required to evaluate the prognosis of fractured roots reconstructed by resin cements with other types of curing systems. All patients who failed to respond sought treatment for inflammation caused by infection from a persistent periodontal pocket. Further, a periodontal pocket in a previously detected area remained in the 12 functional cases. Thus, periodontal pockets along fractures reconstructed with dentin-bonding resin remain a problem that needs to be addressed in future studies. Although we tried to keep the width of the resin cement in an adhesive area to a minimum, this procedure has not been effective in eliminating all periodontal pockets. Rotation of reconstructed roots at replantation may be an option to promote the generation of periodontal tissue surrounding a fracture line. However, indications for replantation rotating a reconstructed root have limitations because of root curvatures or the existence of anatomical organs such as the maxillary sinus or mandibular canal. Clinicians should be aware of the importance of early extraction of vertical root fractures based on an early, accurate diagnosis, because early extraction of fractured roots, before buccal or lingual bone plates are destroyed, may allow successful implantation. When implantation is one of the treatment options for a patient, the benefit of early extraction of a fractured tooth should be considered before selecting the intentional replantation with reconstruction. Biocompatibility of 4-META/TBB-MMA resin for dental pulp tissue and periodontal tissues has been reported (9 –11) and has been considered sufficient for use in soft tissues in procedures such as direct pulp capping, retrofilling in root end surgery, and repair of root perforations. It has been reported that the 4-META/TBBMMA resin component combined with bone morphogenetic protein may accelerate wound healing of damaged pulp tissue (12). Bone morphogenetic protein-containing 4-META/TBB-MMA resin may accelerate the regeneration of damaged periodontal tissue when it is applied to the reconstruction of a fractured root as an adhesive material. A modern approach using bioengineering techniques may constitute a breakthrough method to promote promising long-term prognoses of intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin. As previously reported (6), the longevity of the apical fracture group was shorter than that of the middle fracture group. The
Journal of Endodontics
occlusal force may be transmitted in exactly the same direction as the previous fracture when the fracture runs through the whole root longitudinally, including the apical area. Recurrence of the fracture could then be induced if the adhesion of the fractured fragments reaches a limit of sustainability. The root resorption caused by ankylosis observed in the two incisors may be a result of burnishing the root surface during the extractions of the fractured teeth. It was impossible to remove the fractured roots without damage to the periodontium, because the freshly fractured roots were tightly held by the alveolar bone without any defects. Although root resorption was not detected in the remaining replanted roots, further follow-up is indispensable, because it is still possible that negligibly small root resorption or root resorption that existed in a radiographically undetectable area may progress afterward. Prognoses for autotransplantation of nonfractured teeth have been reported, and success rates of more than 95% (13–15) allow this treatment to be a reliable option for restoring missing teeth. From a comparison of the results of the present study with those of the autotransplantation of nonfractured teeth, it was concluded that intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin has benefits as a treatment alternative, especially for incisor teeth. This study was supported in part by a Grant-in-Aid for Scientific Research (No. 14571812) from the Japan Society for the Promotion of Science. Dr. Hayashi, Dr. Kinomoto, Dr. Takeshige, and Dr. Ebisu are affiliated with the Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Osaka, Japan. Address requests for reprints to Dr. Hayashi, Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. E-mail: [email protected].
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