0099-2399/92/1810-04921503.00/0 JOURNAL OF ENDODONTJCS Copyright © 1992 by The American Association of Endodontists
Printed in U.S.A. VOL. 18, NO. 10, OCTOBER1992
Effect of Different Endodontic Treatment Protocols on Periodontal Repair and Root Resorption of Replanted Dog Teeth Martin Trope, DMD, Cemil Yesilsoy, DMD, Larry Koren, DMD, Joshua Moshonov, DMD, and Shimon Friedman, DMD
This study examined, histologically, the healing of intentionally damaged root surfaces of replanted teeth with either uninfected or infected root canals treated with short- and long-term calcium hydroxide. Thirty beagle dog incisors were randomly divided into four groups. In group 1, uninfected obturated incisors were extracted, the roots were longitudinally grooved and the teeth were replanted within 2 min. In group 2 the root canals were artificially infected followed by extraction, longitudinal grooving, and replantation as described in group 1. Fourteen days after replantation, the root canals were fully instrumented and medicated with intracanal calcium hydroxide. One week later the root canals were permanently obturated with gutta-percha and sealer. The teeth in group 3 were treated as described in group 2 but after 1 wk the calcium hydroxide dressing was repacked for the duration of the study. In group 4 (positive control) the teeth were treated as described in groups 2 and 3 but no endodontic treatment was performed. After 8 wk, sacrifice and histological preparation were carried out. In group 1 complete cemental repair was seen in all teeth. In groups 2 and 3, complete and incomplete cemental repair was seen in seven and two teeth, respectively. An ankylotic area was present in one tooth in group 3. None of the teeth in group 4 showed cemental repair. It was concluded that short- and long-term calcium hydroxide treatment resulted in similar healing patterns when endodontic treatment is initiated 14 days after replantation of teeth.
4, 5) and the extent to which the viability of the periodontal cells remaining on the root surface are maintained (6). Factors, such as extraoral time (3, 7, 8), use of a suitable storage medium (6), and the type and duration of splinting (9), are critical. Thus, whether or not replacement resorption will occur is determined soon after the accident. If present, resorption cannot be reversed (4). On the other hand, the development of inflammatory root resorption is directly related to damage of the periodontium at the time of the accident and the presence of bacteria within the root canal and dentinal tubules (4-10). As a result, extirpation of the pulp and subsequent root canal therapy soon after replantation is critical for the prevention and/or treatment of inflammatory root resorption (11). Thus, the ultimate success or failure of treatment of inflammatory resorption may depend on the endodontic therapy protocol implemented. At present, the American Association of Endodontists Ad Hoc Committee on Treatment of the Avulsed Tooth recommends that endodontic therapy of an avulsed, replanted, mature tooth must include long-term calcium hydroxide treatment (12). Removal of the pulp and preparation of the root canal after 7 to 14 days is recommended. Calcium hydroxide is then introduced into the root canal and replaced every 3 months for a minimum of 6 to 24 months. The root canal is then obturated with a permanent root canal filling material. Although the use of long-term calcium hydroxide for avulsed teeth will result in an extremely high rate of success (11, 13), there are some disadvantages with this treatment regimen. High patient motivation and cooperation are essential because the treatment is long-term and requires repeated replacement of the calcium hydroxide. Without patient cooperation, the root canal may ultimately become infected, resulting in possible loss of the tooth. Calcium hydroxide is antibacterial (14, 15) and, in addition, has been reported to favorably influence the local environment at the resorption site, promoting healing (4). Hammarstrom et al. (16) and Lengheden et al. (17, 18) have warned that use of calcium hydroxide in the root canals of teeth with damaged root surfaces might be contraindicated because of its necrotizing effect on the cells repopulating the root surface. Ankylosis may then result (16). Also, since the critical factor
Progressive root resorption is a serious complication associated with the replantation of avulsed teeth (1-3). The development of replacement resorption depends on both the degree of damage to the periodontium at the time of the avulsion (1,
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TABLE 1. Healing patterns of different endodontic treatment methods after replantation of extracted teeth No. of Teeth Preextraction obturation 1 wk CaOH2 Long-term CaOH2 No treatment
8 9 9 0
Complete Cemental Repair
Partial Cemental Repair
No Cemental Repair
8 7 7 0
0 2 2 0
0 0 0 4
for inflammatory root resorption after avulsion is the presence of an infected root canal system (4, 10), sterilization of the root canal alone should be sufficient to stop inflammatory root resorption. Thus, chemomechanical instrumentation and an antibacterial agent used short-term might be sufficient for this purpose. This is suggested by Cvek's study (13) on avulsed teeth which showed that the same radiographic success occurred when root canals were obturated immediately following replantation compared with those that received long-term calcium hydroxide therapy. Also, if the endodontic treatment is initiated as recommended, 10 to 14 days after the avulsion, the pulp is either ischemically necrotic or minimally infected (16). Thus, routine endodontic treatment should produce a bacteria-free root canal (14, 15). The purpose of this study was to examine, histologically, the healing of damaged root surfaces in replanted teeth with uninfected root canals and with infected root canals, followed by short- and long-term calcium hydroxide treatment initiated 14 days after replantation. MATERIALS AND METHODS Six alternate incisors from both jaws of five beagle dogs were used in this experiment. All incisors had completed root formation. The dogs were anesthetized with an intravenous injection of 6% sodium pentobarbital (30 mg/kg body wt, Nembutal R; Abbott Laboratories, Chicago, IL), and the 30 incisors were randomly assigned to four groups.
Group 1 The canals of eight incisors were fully instrumented and obturated with laterally condensed gutta-percha and Roth's 801 root canal sealer (Chicago, IL) in one session. Two weeks later the teeth were extracted as uniformly as possible with elevators and forceps using gentle rotational movements. The lingual mid-root aspect of the roots were grooved longitudinally to a depth of approximately 1.5 mm with a slow-speed fissure bur, the denuded surfaces washed with sterile water for 20 s, and the teeth replanted into their sockets. Splinting consisted of resorbable sling sutures for approximately 14 days. The dogs were fed a soft diet for 3 days after the replantation procedure after which their normal diet of dog chow once a day was resumed.
Group 2 The pulps of nine incisors were extirpated, the root canals infected with isologous dog's plaque, and the access cavities
Complication 0 0 1 ankylosis 4 inflammatory resorption
sealed with IRM (Caulk Co., Milford, DE). Extraction, longitudinal grooving, replantation, and splinting were performed as described in group 1. Fourteen days after replantation, the root canals of the nine infected teeth were prepared with hand files to ISO size #40, irrigated with 0.5% sodium hypochlorite, and dried with paper points. A creamy suspension of calcium hydroxide USP in sterile saline was then spun into the canals with a Lentulo spiral instrument (Caulk Co.), and the access cavity was sealed with IRM. One week later, the calcium hydroxide was removed from the root canals using files and copious irrigation with 5 ml of 0.5% sodium hypochlorite. The canals were dried and obturated with guttapercha and sealer as described in group 1. All access cavities were sealed with IRM.
Group 3 The nine incisors in this group were treated exactly as described in group 2 with one exception. After 1 wk, the root canals were not permanently obturated. Instead they were filled with a fresh mix of calcium hydroxide which remained for the duration of the experiment.
Group 4 In four teeth, the canals were infected, extracted, grooved, and replanted as described in groups 2 and 3. However, the root canals in this group were not endodontically treated. These teeth served as positive controls. Eight weeks after the second treatment, the dogs were killed by an overdose of 6% sodium pentobarbital. Jaw blocks containing the replanted teeth were separated, fixed in phosphate-buffered formalin, decalcified in 5% formic acid, and embedded in paraplast. Three 5-um horizontal sections were cut every 70 um along the longitudinal groove, stained with hematoxylin and eosin, and subjected to light microscopic examination. The denuded as well as the surrounding root surface were observed for the presence of resorption and/or healing and categorized according to the criteria of Andreasen (19). RESULTS The microscopic findings in the sections taken 70-#m apart throughout the length of the groove were consistent with each other. The periodontal ligament adjacent to the experimental grooves were found to have healed normally in all sections except for an occasional small area of repaired surface resorption. The observations in all of the teeth are summarized in
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F~G 1. Photomicrograph of grooved root surface 2 months after preextraction root canal treatment and replantation (group 1). Root resorption is minimal. A well-defined area of new cementum (NC) covers the entire grooved surface (hematoxylin and eosin; original magnification x l 0).
FIG 3. Photomicrograph of grooved surface 2 months after replantation and endodontic treatment with calcium hydroxide (groups 2 and 3). New cementum (NC) covers part of the grooved root surface. Areas not covered by cementum were bordered by normally structured periodontium (NP) without osteoclasts present (hematoxylin and eosin; original magnification x40).
FIG 2. Photomicrograph of grooved surface 2 months after replantation and endodontic treatment with calcium hydroxide (groups 2 and 3). Areas of repaired surface resorption are present with new cementum (NC) covering the entire grooved surface (hematoxylin and eosin; original magnification xl0).
FIG 4. Photomicrograph of grooved surface 2 months after replantation and endodontic treatment with long-term calcium hydroxide (group 3). New cementum (NC) covers most of the grooved surface. A small area of normally structured periodontium (NP) and replacement resorption (RR) is present on the root surface (hematoxylin and eosin; original magnification xl0).
Table 1. In the eight teeth in group 1, occasional resorptive areas were seen on the grooved root surface. All grooved surfaces including resorptive areas were completely covered with a layer of newly deposited cementum (Fig. 1). In the teeth from groups 2 and 3, more resorption defects were evident on the denuded root surfaces than those in group 1. In both groups 2 and 3, deposition of new cementum over the entire denuded surface was seen in seven teeth (Fig. 2); while in two teeth, the cementum covered only part of the surface (Fig. 3). In the latter two teeth, the denuded area not covered by cementum exhibited a normally structured periodontium on its border with no detectable osteoclasts. Thus, these areas were categorized as arrested surface resorption (Fig. 3) (19). In one tooth in group 3, a small region of replacement resorption was present in the area uncovered by new cementum (Fig. 4). In the positive control teeth (group 4), none of the teeth showed deposition of new cementum over the denuded surfaces, and the periodontal ligament
adjacement to these surfaces was infiltrated by mononuclear inflammatory cells (Fig. 5). Multinucleated resorbing cells were also present in specific areas. Since all except the positive control groups had such uniformly successful healing patterns, it did not seem necessary to subject these findings to statistical analysis.
DISCUSSION As suggested by Hammarstrom et al. (16), the root surfaces of the teeth were artificially damaged to simulate severe cemental damage and to provide a controlled, standardized surface prone to external resorption. The denuded root surfaces were easily discernible histologically as a straight line on an otherwise convex surface. The width of these surfaces was
Vol. 18, No. 10, October 1992
FIG 5. Photomicrograph of grooved root surface 2 months after extraction of the tooth with an infected root canal (group 4). No endodontic treatment was performed. Inflammatory root resorption is present throughout the length of the root-grooved surface.
quite uniform from tooth to tooth so that comparisons of healing patterns were possible. The positive control teeth (group 4) left infected for the duration of the study showed resorption defects without cemental repair in the experimentally grooved areas. This result was consistent with that of previous reports (16, 20) affirming that the presence of bacteria in the root canal prevents repair of the resorption defects and sustains the inflammation in the periodontal ligament. By contrast, minimal initial resorption and total cemental repair and healing ensued after replantation of teeth with noninfected obturated canals (group 1). This result warrants the utilization of such treatment as a negative control in future experiments. The recommendations of the American Association of Endodontists Ad Hoc Committee on Treatment of Avulsed Teeth do not address the question of treatment of a previously endodontically treated tooth that is avulsed (12). The assumption could be made from the recommendations that the gutta-percha should be removed and long-term calcium hydroxide treatment instituted. The results of this study suggest that if the endodontic treatment appears to be adequate, further endodontic therapy in association with the replantation is not immediately necessary. A monthly follow-up period for approximately 6 months might be prudent in such cases where the canal may be infected in spite of the good radiographic appearance of the obturation. At the first sign of inflammatory root resorption, the gutta-percha could be removed and steps taken to sterilize the root canal system. No differences in healing were found in the infected teeth which were obturated with gutta-percha after 1 wk of calcium hydroxide therapy and those treated with a long-term calcium hydroxide dressing. This finding suggests that thorough canal preparation and medication with calcium hydroxide for 1 wk is sufficient to disinfect the root canals and eliminate the etiological agent for inflammatory resorption. Sjogren et al. (15) have demonstrated in humans that a calcium hydroxide root canal dressing for 7 days eliminates the bacteria which have survived after canal preparation. Even in the two teeth exhibiting areas without cemental covering, no active resorbing cells were seen. It can thus be assumed that, in time, these areas would also be covered by cementum. Thus, it appears
Endodontic Treatment of Replanted Teeth
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that routine endodontics is sufficient to remove the stimulus for inflammatory resorption in a canal that is infected for up to 14 days. In this study, ankylosis was seen in one tooth in the long-term calcium hydroxide group. Occasional ankylosis with the use of calcium hydroxide was also seen in other studies (16-18). This ankylosis was probably caused by necrosis of the cells in the periodontal ligament due to the high pH of the calcium hydroxide. In this experiment treatment of the teeth artificially infected for 2 wk before endodontic therapy proved to be mostly successful. In a clinical situation, the root canal probably would not even be infected. When intact teeth are extracted and replanted quickly, no inflammatory/progressive resorption occurs for as long as 8-wk even without endodontic treatment (16). This suggests that either the canals remain uninfected for 8 wk or long enough for cemental repair to take place. In a tooth replanted after an avulsion the chance for infection is higher, but the establishment of an infection in the canal and dentinal tubules could still require longer than l0 to 14 days. It must be recognized that the long-term calcium hydroxide treatment proved successful in this study. With a cooperative patient, this is probably still the most predictable treatment. However, the recommendations of the American Association of Endodontists restrict dentists from legally performing routine endodontic treatment even when it is obvious that the patient will be uncooperative. The results of this study indicate that it is unjustified to recommend only long-term calcium hydroxide therapy for avulsed teeth when endodontic treatment is initiated l0 to 14 days after replantation. Further studies are needed to ascertain whether long-term calcium hydroxide therapy is essential when the pulpal infection is already well established and radiographic evidence of resorption is apparent, i.e. when treatment is initiated at least 3 wk after replantation. This research was supported in part by a Student Research Support Grant from the Research and Education Foundation of the American Association of Endodontists. The opinions, assertions, materials, and methodologies herein are private ones of the author and are not to be construed as official or reflecting the views of the American Association of Endodontists or the Research and Education Foundation. Drs. Trope, Yesilsoy, and Koren are affiliated with the Department of Endodontology, Temple University, School of Dentistry, Philadelphia, PA. Drs. Moshonov and Friedman are affiliated with the Department of Endodontics, The Hebrew University-Hadassah Faculty of Dental Medicine, Jerusalem, Israel. Address requests for reprints to Dr. Martin Trope, Department of Endodontology, Temple University, School of Dentistry, 3223 North Broad Street, Philadelphia, PA 19140.
References
1. Andreasen JO. Traumatic injuries of the teeth. 2nd ed. Copenhagen: Munksgaard, 1981. 2. Lenstrup K, Skieller V. A follow-up study of teeth replanted after accidental loss. Acta Odontol Scand 1959;17:503-9. 3. Andreasen JO, Hjorting-Hansen E. Replantation of teeth. I. Radiographic and clinical study of 110 human teeth replanted after accidental loss. Acta Odontol Scand 1966;24:263-86. 4. Tronstad L. Root resorption--etiology, terminology and clinical manifestations. Endod Dent Traumato11988;4:241-52. 5. Andreasen JO, Kristersson L. The effect of limited drying or removal of the periodontal ligament. Periodontal healing after replantation of mature permanent incisors in monkeys. Acta Odontol Scand 1981 ;39:1-13. 6. Blomlof L. Milk and saliva as possible storage media for traumatized exarticulated teeth prior to replantation [Thesis]. Swed Dent J 1981 ;8(suppl). 7. Andreasen JO. The effect of extra-alveolar period and storage media upon periodontal and pulpal healing after replantation of mature permanent incisors in monkeys. Int J Oral Surg 1981;10:43-5.
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8, Cvek M, Granath LE, Hollender L. Treatment of non-vital permanent incisors with calcium hydroxide. III, Variations of occurrence of ankylosis of reimplanted teeth with duration of extra-alveolar period and storage environment. Odontol Revy 1974;25:43-56, 9. Andreasen JO. The effect of splinting upon periodontal healing after replantation of permanent incisors in monkeys. Acta Odontol Scand 1975;33:313-23. 10. Hammarstrom L, Blomlof L, Feiglin B, Andreasen L, Lindskog S. Replantation of teeth and antibiotic treatment. Endod Dent Traumatol 1986;2:51-7, 11. Cvek M. Endodontic treatment of traumatized teeth. In: Andreasen JO, ed. Traumatic injuries of the teeth. 2nd ed. Copenhagen: Munksgaard,
1981:321-84. 12. Camp JH. Recommended guidelines for treatment of the avulsed tooth, J Endodon 1983;9:571, 13. Cvek M. Treatment of non-vital permanent incisors with calcium hydroxide. II. Effect on external root resorption in luxated teeth compared with effect of root filling with gutta-percha. A follow-up. Odontol Revy 1973;24:34354.
Journal of Endodontics 14. Bystrom A, Claesson R, Sundqvist G. The antibacterial effect of camphorated paramonochlorophenol, camphorated phenol and calcium hydroxide in the treatment of infected root canals. Endod Dent Traumato11985;1:170-5. 15. Sjogren U, Figdor D, Spangberg L, Sundqvist G. The antimicrobial effect of calcium hydroxide as a short-term intracanal dressing. Int Endod J 1991 ;24:119-25. 16. Hammarstrom L, Blomlof LB, Feiglin B, Lindskog S. Effect of calcium hydroxide treatment on periodontal repair and root resorption. Endod Dent Traumato11986;2:184-9. 17. Lengheden A, Blomlof L, Lindskog S. Effect of immediate calcium hydroxide treatment and permanent root-filling on periodontal healing in contaminated replanted teeth. Scand J Dent Res 1990;99:139-46. 18. Lengheden A, Blomlof L, Lindskog S. Effect of delayed calcium hydroxide treatment on periodontal healing in contaminated replanted teeth. Scand J Dent Res 1991 ;99:147-53. 19. Andreasen JO. Experimental dental traumatology: development of a model for external root resorption. Endod Dent Traumato11987;3:269-87. 20. Andreasen JO. Relationship between surface and inflammatory resorption and changes in the pulp after replantation of permanent incisors in monkeys. J Endodon 1981 ;7:294-301.
A Word for the Wise Definitions of genius are legion; a commonly quoted one is "the ability to perceive in an unhabitual way." Claude Bernard said the same thing somewhat differently when speaking of "seeing what everybody has seen and thinking what nobody has thought."
Cosby Newell
Printed in U.S.A. VOL. 18, NO. 10, OCTOBER1992
Effect of Different Endodontic Treatment Protocols on Periodontal Repair and Root Resorption of Replanted Dog Teeth Martin Trope, DMD, Cemil Yesilsoy, DMD, Larry Koren, DMD, Joshua Moshonov, DMD, and Shimon Friedman, DMD
This study examined, histologically, the healing of intentionally damaged root surfaces of replanted teeth with either uninfected or infected root canals treated with short- and long-term calcium hydroxide. Thirty beagle dog incisors were randomly divided into four groups. In group 1, uninfected obturated incisors were extracted, the roots were longitudinally grooved and the teeth were replanted within 2 min. In group 2 the root canals were artificially infected followed by extraction, longitudinal grooving, and replantation as described in group 1. Fourteen days after replantation, the root canals were fully instrumented and medicated with intracanal calcium hydroxide. One week later the root canals were permanently obturated with gutta-percha and sealer. The teeth in group 3 were treated as described in group 2 but after 1 wk the calcium hydroxide dressing was repacked for the duration of the study. In group 4 (positive control) the teeth were treated as described in groups 2 and 3 but no endodontic treatment was performed. After 8 wk, sacrifice and histological preparation were carried out. In group 1 complete cemental repair was seen in all teeth. In groups 2 and 3, complete and incomplete cemental repair was seen in seven and two teeth, respectively. An ankylotic area was present in one tooth in group 3. None of the teeth in group 4 showed cemental repair. It was concluded that short- and long-term calcium hydroxide treatment resulted in similar healing patterns when endodontic treatment is initiated 14 days after replantation of teeth.
4, 5) and the extent to which the viability of the periodontal cells remaining on the root surface are maintained (6). Factors, such as extraoral time (3, 7, 8), use of a suitable storage medium (6), and the type and duration of splinting (9), are critical. Thus, whether or not replacement resorption will occur is determined soon after the accident. If present, resorption cannot be reversed (4). On the other hand, the development of inflammatory root resorption is directly related to damage of the periodontium at the time of the accident and the presence of bacteria within the root canal and dentinal tubules (4-10). As a result, extirpation of the pulp and subsequent root canal therapy soon after replantation is critical for the prevention and/or treatment of inflammatory root resorption (11). Thus, the ultimate success or failure of treatment of inflammatory resorption may depend on the endodontic therapy protocol implemented. At present, the American Association of Endodontists Ad Hoc Committee on Treatment of the Avulsed Tooth recommends that endodontic therapy of an avulsed, replanted, mature tooth must include long-term calcium hydroxide treatment (12). Removal of the pulp and preparation of the root canal after 7 to 14 days is recommended. Calcium hydroxide is then introduced into the root canal and replaced every 3 months for a minimum of 6 to 24 months. The root canal is then obturated with a permanent root canal filling material. Although the use of long-term calcium hydroxide for avulsed teeth will result in an extremely high rate of success (11, 13), there are some disadvantages with this treatment regimen. High patient motivation and cooperation are essential because the treatment is long-term and requires repeated replacement of the calcium hydroxide. Without patient cooperation, the root canal may ultimately become infected, resulting in possible loss of the tooth. Calcium hydroxide is antibacterial (14, 15) and, in addition, has been reported to favorably influence the local environment at the resorption site, promoting healing (4). Hammarstrom et al. (16) and Lengheden et al. (17, 18) have warned that use of calcium hydroxide in the root canals of teeth with damaged root surfaces might be contraindicated because of its necrotizing effect on the cells repopulating the root surface. Ankylosis may then result (16). Also, since the critical factor
Progressive root resorption is a serious complication associated with the replantation of avulsed teeth (1-3). The development of replacement resorption depends on both the degree of damage to the periodontium at the time of the avulsion (1,
492
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Endodontic Treatment of Replanted Teeth
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TABLE 1. Healing patterns of different endodontic treatment methods after replantation of extracted teeth No. of Teeth Preextraction obturation 1 wk CaOH2 Long-term CaOH2 No treatment
8 9 9 0
Complete Cemental Repair
Partial Cemental Repair
No Cemental Repair
8 7 7 0
0 2 2 0
0 0 0 4
for inflammatory root resorption after avulsion is the presence of an infected root canal system (4, 10), sterilization of the root canal alone should be sufficient to stop inflammatory root resorption. Thus, chemomechanical instrumentation and an antibacterial agent used short-term might be sufficient for this purpose. This is suggested by Cvek's study (13) on avulsed teeth which showed that the same radiographic success occurred when root canals were obturated immediately following replantation compared with those that received long-term calcium hydroxide therapy. Also, if the endodontic treatment is initiated as recommended, 10 to 14 days after the avulsion, the pulp is either ischemically necrotic or minimally infected (16). Thus, routine endodontic treatment should produce a bacteria-free root canal (14, 15). The purpose of this study was to examine, histologically, the healing of damaged root surfaces in replanted teeth with uninfected root canals and with infected root canals, followed by short- and long-term calcium hydroxide treatment initiated 14 days after replantation. MATERIALS AND METHODS Six alternate incisors from both jaws of five beagle dogs were used in this experiment. All incisors had completed root formation. The dogs were anesthetized with an intravenous injection of 6% sodium pentobarbital (30 mg/kg body wt, Nembutal R; Abbott Laboratories, Chicago, IL), and the 30 incisors were randomly assigned to four groups.
Group 1 The canals of eight incisors were fully instrumented and obturated with laterally condensed gutta-percha and Roth's 801 root canal sealer (Chicago, IL) in one session. Two weeks later the teeth were extracted as uniformly as possible with elevators and forceps using gentle rotational movements. The lingual mid-root aspect of the roots were grooved longitudinally to a depth of approximately 1.5 mm with a slow-speed fissure bur, the denuded surfaces washed with sterile water for 20 s, and the teeth replanted into their sockets. Splinting consisted of resorbable sling sutures for approximately 14 days. The dogs were fed a soft diet for 3 days after the replantation procedure after which their normal diet of dog chow once a day was resumed.
Group 2 The pulps of nine incisors were extirpated, the root canals infected with isologous dog's plaque, and the access cavities
Complication 0 0 1 ankylosis 4 inflammatory resorption
sealed with IRM (Caulk Co., Milford, DE). Extraction, longitudinal grooving, replantation, and splinting were performed as described in group 1. Fourteen days after replantation, the root canals of the nine infected teeth were prepared with hand files to ISO size #40, irrigated with 0.5% sodium hypochlorite, and dried with paper points. A creamy suspension of calcium hydroxide USP in sterile saline was then spun into the canals with a Lentulo spiral instrument (Caulk Co.), and the access cavity was sealed with IRM. One week later, the calcium hydroxide was removed from the root canals using files and copious irrigation with 5 ml of 0.5% sodium hypochlorite. The canals were dried and obturated with guttapercha and sealer as described in group 1. All access cavities were sealed with IRM.
Group 3 The nine incisors in this group were treated exactly as described in group 2 with one exception. After 1 wk, the root canals were not permanently obturated. Instead they were filled with a fresh mix of calcium hydroxide which remained for the duration of the experiment.
Group 4 In four teeth, the canals were infected, extracted, grooved, and replanted as described in groups 2 and 3. However, the root canals in this group were not endodontically treated. These teeth served as positive controls. Eight weeks after the second treatment, the dogs were killed by an overdose of 6% sodium pentobarbital. Jaw blocks containing the replanted teeth were separated, fixed in phosphate-buffered formalin, decalcified in 5% formic acid, and embedded in paraplast. Three 5-um horizontal sections were cut every 70 um along the longitudinal groove, stained with hematoxylin and eosin, and subjected to light microscopic examination. The denuded as well as the surrounding root surface were observed for the presence of resorption and/or healing and categorized according to the criteria of Andreasen (19). RESULTS The microscopic findings in the sections taken 70-#m apart throughout the length of the groove were consistent with each other. The periodontal ligament adjacent to the experimental grooves were found to have healed normally in all sections except for an occasional small area of repaired surface resorption. The observations in all of the teeth are summarized in
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F~G 1. Photomicrograph of grooved root surface 2 months after preextraction root canal treatment and replantation (group 1). Root resorption is minimal. A well-defined area of new cementum (NC) covers the entire grooved surface (hematoxylin and eosin; original magnification x l 0).
FIG 3. Photomicrograph of grooved surface 2 months after replantation and endodontic treatment with calcium hydroxide (groups 2 and 3). New cementum (NC) covers part of the grooved root surface. Areas not covered by cementum were bordered by normally structured periodontium (NP) without osteoclasts present (hematoxylin and eosin; original magnification x40).
FIG 2. Photomicrograph of grooved surface 2 months after replantation and endodontic treatment with calcium hydroxide (groups 2 and 3). Areas of repaired surface resorption are present with new cementum (NC) covering the entire grooved surface (hematoxylin and eosin; original magnification xl0).
FIG 4. Photomicrograph of grooved surface 2 months after replantation and endodontic treatment with long-term calcium hydroxide (group 3). New cementum (NC) covers most of the grooved surface. A small area of normally structured periodontium (NP) and replacement resorption (RR) is present on the root surface (hematoxylin and eosin; original magnification xl0).
Table 1. In the eight teeth in group 1, occasional resorptive areas were seen on the grooved root surface. All grooved surfaces including resorptive areas were completely covered with a layer of newly deposited cementum (Fig. 1). In the teeth from groups 2 and 3, more resorption defects were evident on the denuded root surfaces than those in group 1. In both groups 2 and 3, deposition of new cementum over the entire denuded surface was seen in seven teeth (Fig. 2); while in two teeth, the cementum covered only part of the surface (Fig. 3). In the latter two teeth, the denuded area not covered by cementum exhibited a normally structured periodontium on its border with no detectable osteoclasts. Thus, these areas were categorized as arrested surface resorption (Fig. 3) (19). In one tooth in group 3, a small region of replacement resorption was present in the area uncovered by new cementum (Fig. 4). In the positive control teeth (group 4), none of the teeth showed deposition of new cementum over the denuded surfaces, and the periodontal ligament
adjacement to these surfaces was infiltrated by mononuclear inflammatory cells (Fig. 5). Multinucleated resorbing cells were also present in specific areas. Since all except the positive control groups had such uniformly successful healing patterns, it did not seem necessary to subject these findings to statistical analysis.
DISCUSSION As suggested by Hammarstrom et al. (16), the root surfaces of the teeth were artificially damaged to simulate severe cemental damage and to provide a controlled, standardized surface prone to external resorption. The denuded root surfaces were easily discernible histologically as a straight line on an otherwise convex surface. The width of these surfaces was
Vol. 18, No. 10, October 1992
FIG 5. Photomicrograph of grooved root surface 2 months after extraction of the tooth with an infected root canal (group 4). No endodontic treatment was performed. Inflammatory root resorption is present throughout the length of the root-grooved surface.
quite uniform from tooth to tooth so that comparisons of healing patterns were possible. The positive control teeth (group 4) left infected for the duration of the study showed resorption defects without cemental repair in the experimentally grooved areas. This result was consistent with that of previous reports (16, 20) affirming that the presence of bacteria in the root canal prevents repair of the resorption defects and sustains the inflammation in the periodontal ligament. By contrast, minimal initial resorption and total cemental repair and healing ensued after replantation of teeth with noninfected obturated canals (group 1). This result warrants the utilization of such treatment as a negative control in future experiments. The recommendations of the American Association of Endodontists Ad Hoc Committee on Treatment of Avulsed Teeth do not address the question of treatment of a previously endodontically treated tooth that is avulsed (12). The assumption could be made from the recommendations that the gutta-percha should be removed and long-term calcium hydroxide treatment instituted. The results of this study suggest that if the endodontic treatment appears to be adequate, further endodontic therapy in association with the replantation is not immediately necessary. A monthly follow-up period for approximately 6 months might be prudent in such cases where the canal may be infected in spite of the good radiographic appearance of the obturation. At the first sign of inflammatory root resorption, the gutta-percha could be removed and steps taken to sterilize the root canal system. No differences in healing were found in the infected teeth which were obturated with gutta-percha after 1 wk of calcium hydroxide therapy and those treated with a long-term calcium hydroxide dressing. This finding suggests that thorough canal preparation and medication with calcium hydroxide for 1 wk is sufficient to disinfect the root canals and eliminate the etiological agent for inflammatory resorption. Sjogren et al. (15) have demonstrated in humans that a calcium hydroxide root canal dressing for 7 days eliminates the bacteria which have survived after canal preparation. Even in the two teeth exhibiting areas without cemental covering, no active resorbing cells were seen. It can thus be assumed that, in time, these areas would also be covered by cementum. Thus, it appears
Endodontic Treatment of Replanted Teeth
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that routine endodontics is sufficient to remove the stimulus for inflammatory resorption in a canal that is infected for up to 14 days. In this study, ankylosis was seen in one tooth in the long-term calcium hydroxide group. Occasional ankylosis with the use of calcium hydroxide was also seen in other studies (16-18). This ankylosis was probably caused by necrosis of the cells in the periodontal ligament due to the high pH of the calcium hydroxide. In this experiment treatment of the teeth artificially infected for 2 wk before endodontic therapy proved to be mostly successful. In a clinical situation, the root canal probably would not even be infected. When intact teeth are extracted and replanted quickly, no inflammatory/progressive resorption occurs for as long as 8-wk even without endodontic treatment (16). This suggests that either the canals remain uninfected for 8 wk or long enough for cemental repair to take place. In a tooth replanted after an avulsion the chance for infection is higher, but the establishment of an infection in the canal and dentinal tubules could still require longer than l0 to 14 days. It must be recognized that the long-term calcium hydroxide treatment proved successful in this study. With a cooperative patient, this is probably still the most predictable treatment. However, the recommendations of the American Association of Endodontists restrict dentists from legally performing routine endodontic treatment even when it is obvious that the patient will be uncooperative. The results of this study indicate that it is unjustified to recommend only long-term calcium hydroxide therapy for avulsed teeth when endodontic treatment is initiated l0 to 14 days after replantation. Further studies are needed to ascertain whether long-term calcium hydroxide therapy is essential when the pulpal infection is already well established and radiographic evidence of resorption is apparent, i.e. when treatment is initiated at least 3 wk after replantation. This research was supported in part by a Student Research Support Grant from the Research and Education Foundation of the American Association of Endodontists. The opinions, assertions, materials, and methodologies herein are private ones of the author and are not to be construed as official or reflecting the views of the American Association of Endodontists or the Research and Education Foundation. Drs. Trope, Yesilsoy, and Koren are affiliated with the Department of Endodontology, Temple University, School of Dentistry, Philadelphia, PA. Drs. Moshonov and Friedman are affiliated with the Department of Endodontics, The Hebrew University-Hadassah Faculty of Dental Medicine, Jerusalem, Israel. Address requests for reprints to Dr. Martin Trope, Department of Endodontology, Temple University, School of Dentistry, 3223 North Broad Street, Philadelphia, PA 19140.
References
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A Word for the Wise Definitions of genius are legion; a commonly quoted one is "the ability to perceive in an unhabitual way." Claude Bernard said the same thing somewhat differently when speaking of "seeing what everybody has seen and thinking what nobody has thought."
Cosby Newell
