Effect of extra-alveolar period and storage media upon periodontal and pulpal healing after replantation of mature permanent incisors in monkeys

The effect of extra-alveolar period and storage media upon periodontal and pulpal healing after replantation was studied in green Vervet monkeys (Cercopithecus aethiops). Mandibular lateral incisors were extracted. The extra-alveolar period before replantation was 0, 18, 30, 60, 90, and 120 min. The storage media for the extracted teeth were tap water, physiologic saline, saliva or dry storage. The animals were sacrificed 8 weeks after replantation and the replanted teeth were examined histometrically. The following histologic parameters were registered for each tooth: surface resorption, inflammatory resorption, replacement resorption (ankylosis), periapical inflammatory changes, the extent of vital pulp and downgrowth of pocket epithelium. A significant relationship was found between the frequency of root resorption, extra-alveolar period and storage medium. This was especially evident after dry storage. Surface resorption was found with approximately the same frequency irrespective of extra-alveolar period and storage media. Inflammatory root resorption was especially common after dry storage and was related to the length of the extra-alveolar period. Already after 30 min dry storage, this resorption type was very prominent. Teeth stored in tap water, saline or saliva showed about the same frequency of inflammatory resorption, which increased slightly with increased extra-alveolar periods. Replacement resorption showed a strong relationship to dry storage and became very prominent after 60 min. Replacement resorption was rarely found among teeth stored in saline or saliva; whereas it was significantly increased among teeth stored in tap water. It is concluded that saline and saliva offer good protection against root resorption during the extra-alveolar period.     

Replantation of 400 avulsed permanent incisors. 3. Factors related to root growth

Abstract Four hundred avulsed and replanted permanent incisors were examined for pulpal and periodontal healing. In 30 teeth, root formation was incomplete at the time of injury. Two teeth were excluded from the study due to nonphysiological extraalveolar storage (i.e. homemade saline). Of the 28 remaining replanted incisors, 7 showed subsequently completed root development, 8 partially completed root development and 13 arrested root development. Completed root development subsequent to replantation was found to be significantly related to pulpal revascularization, being rare in cases with pulp necrosis (5 of 15 teeth) and frequent after pulpal healing (11 of 13 teeth) (p=0.01). Root development was not found to be significantly related to the extraalveolar storage period; but occurred slightly more frequently when the dry–storage period was less than 45 min. (p=0.13). Ingrowth of bone and formation of an internal periodontal ligament (PDL) was found in 6 teeth and was related to arrested root formation in cases with pulpal healing. The explanatory factor for these findings appeared to be damage to the Hertwig's epithelial root sheath.     

The effect of apicoectomy before replantation on periodontal and pulpal healing in teeth in monkeys

The effect of resection of the apical part of the root before replantation upon periodontal and pulpal healing was studied in 7 green Vervet monkeys (Cercopithecus aethiops) using teeth with incomplete and complete root formation. Maxillary central incisors, mandibular lateral incisors and first and second mandibular molars were used in this experiment. On one side, the tooth was extracted and replanted with an intact root while the contralateral tooth had 2 mm of the apex resected for the purpose of facilitating pulpal repair and eliminating resorption in the resorption-prone region of the root. The replanted teeth were examined histologically 8 weeks after replantation. The histometric analysis revealed no significant difference in periodontal healing between teeth with or without apical resection. With regard to pulpal healing, apical resection was found to lead to significantly less vital pulp tissue in teeth with immature root formation. A similar, but not significant difference was found for mature teeth. Based on these findings, it could not be recommended that apices be resected prior to replantation in order to improve pulpal repair.     

Replantation of 45 avulsed permanent teeth: a 1-year follow-up study

Abstract –  Thirty-four patients with 45 avulsed and replanted permanent teeth were followed for 1 year. All teeth were soaked in tetracycline before replantation. In addition, enamel matrix derivative was used in teeth with dry storage times exceeding 30 min. Splinting was carried out with a non-rigid titanium splint and was limited to 7–10 days. Within that period, root canal treatment was begun in all teeth with a closed apex, whereas teeth with an open apex and ideal post-traumatic storage were not instrumented. All patients were given tetracycline systematically for 10 days. The survival rate of replanted avulsed permanent teeth was 95.6% at the 1-year follow-up. In 82.2%, root canal treatment was performed. Pulp survival was never observed, but three teeth had pulp canal obliteration. Normal periodontal healing was observed in 57.7% of teeth; 42.3% of teeth showed external root resorption (28.9% replacement resorption, 6.7% infection-related resorption, 6.7% surface resorption). The occurrence of replacement resorption correlated with the period of extraoral dry storage. Compared with other clinical studies on avulsed and replanted teeth, the present study reports a higher percentage of periodontal healing. The favorable treatment outcome may be associated with a strict protocol to enforce endodontic treatment, the use of topical and systemic tetracycline, and the relatively high number of ideally stored teeth following avulsion. In contrast, the present study has a follow-up period limited to 1 year.     

The effect of removal of the coagulum in the alveolus before replantation upon periodontal and pulpal healing of mature permanent incisors in monkeys

The effect of removal of the coagulum in the alveolus before replantation upon periodontal and pulpal healing was studied in green Vervet monkeys (Cercopithecus aethiops). Mandibular lateral incisors were extracted. The extra-alveolar period before replantation was 60 min. The storage medium for the extracted teeth was physiologic saline. On the right side of the mandible, the coagulum was removed before replantation, using syringe with saline assisted by a spoon-shaped excavator. On the left side, the tooth was replanted with the coagulum in situ. The replanted teeth were examined histologically after 8 weeks. The histometric analysis showed no significant difference in periodontal or pulpal healing between the two groups. Based on this finding, it is suggested that replantation of avulsed mature teeth be carried out immediately, without any attempt to remove the coagulum.     

The effect of topical minocycline on replacement resorption of replanted monkeys' teeth

Abstract – Tetracycline has been reported to possess antiresorptive properties in addition to antimicrobial actions. Systemic administration of tetracycline showed variable results in the control of replacement resorption after replantation with good results in half of the cases, and almost no healing in the rest. The purpose of this study was to evaluate histologically the effect of topically applied minocycline on replacement resorption of replanted monkeys' teeth. Thirty‐two roots from seven monkeys were endodontically treated aseptically to prevent inflammatory resorption of pulpal origin, a common sequela after avulsion injury. Teeth were then extracted as atraumatically as possible. Teeth in the negative control group (10 roots) were replanted almost immediately, while teeth in the positive control group (12 roots) were allowed to bench‐dry for 1 h prior to replantation, both without further treatment. Teeth in the experimental group (10 roots) were bench‐dried for 1 h, rinsed with saline, and then immersed in 1 ml of 50 mg ml^?1 minocycline hydrochloride for 5 min before replantation. No splinting was used. After 12 weeks, the animals were sacrificed and histological sections were prepared and evaluated according to a morphometric analysis modified from that described by Andreasen (1987) as complete healing, inflammatory resorption, and replacement resorption. Kruskal–Wallis test showed significant differences among the three groups in all the three healing categories. Further analysis with Mann–Whitney U‐test showed teeth in the negative control group to have significantly higher complete healing and significant lower unfavorable healing, comprising of replacement resorption and inflammatory root resorption than the positive control group and the minocycline group. Topical application of minocycline to the root surface appeared to result in slightly higher occurrence of complete healing (32.46%) compared to the delayed replantation group with no minocycline treatment (positive control) (16.58%), but the difference was not statistically significant (P = 0.09).     

Effects of temperature, storage time and media on periodontal and pulpal healing after replantation of incisors in monkeys

Abstract – The effect of temperature of various storage media and at varying storage periods upon periodontal ligament (PDL) and pulpal healing after tooth replantation was examined in green vervet monkeys (Cercopithecus aethiops). Mandibular lateral incisors with mature root formation were extracted and kept in dry storage at 22, 4 and ?18 °C; in saline at 37, 22, 4 and ?18 °C; or in saliva (i.e. in the buccal vestibule) at 37 °C for either 60 or 120 min prior to replantation. The animals were sacrificed 8 weeks after replantation and the replanted teeth examined histometrically. The following histological parameters were registered for each tooth: normal PDL, surface resorption, inflammatory resorption, replacement resorption (ankylosis), downgrowth of pocket epithelium, periapical inflammatory changes, and the extent of vital pulp. A total of 125 replanted teeth were examined. Storage in saliva at 37 °C showed a similar amount of normal PDL compared to saline storage for both 60 and 120 min. Saline storage for 60 or 120 min showed no difference in the extent of normal PDL when storage was compared at 37, 22 and 4 °C. However, storage at ?18 °C resulted in significantly less normal PDL than storage at other temperatures. Dry storage for 60 min showed significantly less root resorption at 4 °C compared to 22 °C. Furthermore, dry storage at ?18 °C showed significantly less normal PDL than storage at 4 °C. When the dry storage period was extended to 120 min, no difference was found between 22, 4 and ?18 °C. It is concluded that the temperature (above 0 °C) of the storage medium is of importance only for dry storage and in such a situation only for shorter extra‐alveolar periods, i.e. for 60‐min storage and not for 120 min, where extensive destruction of the PDL always takes place. It is suggested that the temperature effect of 4 °C could be related to less evaporation from the PDL and thereby less damage to the PDL cells or a strict temperature effect upon cell metabolism. Pulp healing in all the cases was limited to the entrance of the pulp canal, and no significant pattern was found between storage media, time and temperature.     

Replantation of 400 avulsed permanent incisors. 1. Diagnosis of healing complications

Abstract A material of 322 patients with 400 avulsed and replanted permanent teeth were followed prospectively in the period from 1965 to 1988 (mean observation period=5.1 yrs). The age of the patients at the time of replantation ranged from 5 to 52 yrs (mean =13.7 yrs and median =11.0 yrs). Standardized patient records were used through the entire period in order to obtain valid data concerning the extent of injury and treatment provided. At the follow–up period, pulpal and periodontal healing were monitored by clinical examination, mobility testing and standardized radio–graphic controls. Thirty–two of the replanted teeth (8%) showed pulpal healing. When related to teeth with incomplete root formation, where pulpal revascularization was anticipated (n = 94) the frequency of pulpal healing was 34%. Periodontal ligament healing (i.e. with no evidence of external root resorption) was found in 96 teeth (24%). Gingival healing was found in 371 teeth (93%). During the observation period, 119 teeth (30%) were extracted. Tooth loss was slightly more frequent in teeth with incomplete root formation at the time of replantation than in teeth with completed root formation.     

Analysis of the healing process in delayed tooth replantation after root canal filling with calcium hydroxide,Sealapex and Endofill: a microscopic study in rats

Abstract – The major concern in the therapeutics of tooth replantation refers to the occurrence of root resorption and different approaches have been proposed to prevent or treat these complications. The purpose of this study was to evaluate tissue response to delayed replantation of anterior rat teeth treated endodontically using calcium hydroxide, Sealapex, and Endofill without the placement of gutta‐percha cones. Thirty rats had their right upper incisor extracted and maintained in dry storage for 60 min. After removal of the dental papilla, enamel organ, pulp tissue, and periodontal ligament remnants, the teeth were immersed in 2% sodium fluoride phosphate acidulated, pH 5.5, for 10 min. The root canals were dried with absorbent paper points and the teeth were assigned to three groups (n = 10) according to the filling material. Group I – calcium hydroxide and propyleneglycol paste, Group II – Sealapex, and Group III – Endofill. The sockets were irrigated with saline and the teeth were replanted. Replacement resorption, inflammatory resorption and ankylosis were observed in all groups. Although the occurrence of inflammatory resorption was less frequent in Group I, there were no statistically significant differences among the groups. It may be concluded that compared to the paste, filling the root canals with Sealapex and Endofill sealers without the placement of gutta‐percha cones did not provide better results.     

Periodontal healing after replantation and autotransplantation of incisors in monkeys

The effect of injury to the cemental or alveolar part of the periodontal ligament upon periodontal healing after replantation and autotransplantation of teeth was studied in green Vervet monkeys. Sixty-six maxillary central incisors were replanted or autotransplanted after extra-alveolar periods of 18 min. saline storage or 120 min. dry storage. The animals were sacrificed after 8 weeks and the teeth examined histometrically. Identical healing was found in the following experimental groups: replantation or autotransplantation after 18 min. and replantation with or without removal of periodontal ligament in the alveolus. A significant increase in replacement resorption (ankylosis) compared to the 18 min. replantation group was found in the following groups: replantation and autotransplantation after 120 min., replantation after removal of periodontal ligament on the root surface and autotransplantation after 120 min. to a socket where the tooth was extracted 18 min. earlier. Autotransplantation after 18 min. to a socket where a tooth had been extracted 120 min. earlier led to a significant increase in the amount of replacement resorption compared to transplantation to an 18 min. socket. Based on these findings, it is concluded that the presence of an intact and viable periodontal ligament on the root surface is the most important factor in assuring healing without root resorption. The length of the extra-alveolar period also seems to exert some influence upon the socket, enhancing the development of ankylosis.     

Histological and immunohistochemical analyses of the chronology of healing process after immediate tooth replantation in incisor rat teeth

Abstract – Dental tissues have special characteristics, and its regenerative capacity is noteworthy. However, understanding the circumstances that lead to regeneration is challenging. In this study, the chronology of the healing process after immediate replantation of rat incisor teeth was examined by histological and immunohistochemical analyses within a 60‐day period. Thirty‐six male Wistar rats had their maxillary right incisors extracted and replanted after 15 min in saline storage. The rats were sacrificed immediately 3, 7, 15, 28, and 60 days after replantation. The histological analysis showed rupture of the periodontal ligament and formation of a blood clot, which started being replaced by a connective tissue after 3 days. At 7 days, the gingival mucosa epithelium was reinserted and areas of root resorption could be seen. At 15 days, the periodontal ligament was repaired. At 3 days, the pulp presented an absence of the odontoblast layer, which started being replaced by a connective tissue. This tissue suffered gradual calcification, filling the root canal at 28 and 60 days. The root ends were closed. The immunohistochemical analysis revealed greater expression of OP, OPG, and RANK proteins in the initial periods (0 and 3 days), while TRAP expression predominated at 28 and 60 days (P < 0.05). In conclusion, in delayed tooth replantation, there is great new bone formation activity in the earlier periods of the repair process, while a predominance of bone resorption and remodeling is observed in the more advanced periods.     

Effect of root surface treatment with propolis and fluoride in delayed tooth replantation in rats

Abstract – Replantation is an acceptable option for treatment of an avulsed permanent tooth. Nevertheless, an extended extraoral period damages the periodontal ligament and results in external root resorption. The purpose of this study was to assess by histologic and histometric analysis, the influence of propolis 15% (natural resinous substance collected by Apis mellifera bees from various plants) and the fluoride solution used as root surface treatment on the healing process after delayed tooth replantation. Thirty Wistar (Rattus norvegicus albinus) rats were submitted to extraction of their upper right incisor. The teeth were maintained in a dry environment for 60 min. After this, the pulp was extirpated and the papilla, enamel organ and periodontal ligament were removed with scalpel. The teeth were divided into three experimental groups: Group I – teeth immersed in 20 ml of physiologic saline; Group II – teeth immersed in 20 ml of 2% acidulated phosphate sodium fluoride; Group III – teeth immersed in 20 ml of 15% propolis. After 10 min of immersion in the solutions, the root canals were dried and filled with calcium hydroxide paste and the teeth were replanted. The animals were euthanized 60 days after replantation. The results showed that similar external root resorption was seen in the propolis and fluoride groups. Teeth treated with physiologic saline tended to have more inflammatory root resorption compared with those treated with fluoride or propolis. However, the comparative analysis did not reveal statistically significant differences (P > 0.05) between the treatment modalities when used for delayed tooth replantation.     

Periodontal healing of exarticulated monkey teeth stored in milk or saliva

Abstract – Saliva has usually been recommended as a storage medium for exarticulated teeth. Recent tissue culture studies have, however, shown that milk has a more suitable osmolaliry than saliva and that milk is a bettter storage medium for human periodontal ligament cell. In the present investigation periodontal healing of replanted monkey teeth has been studied after storage of teeth in milk or saliva before replantation. There was much less root resorption, especially inflammatory resorption, after storage in milk thatn in saliva. Storage of teeth in milk for 3 h before replantation resulted in the same low frequence of root resorptions as was seen after immediate replantation. There was hardly any replacement resorption (ankylosis) seen in the replanted teeth.     

The effects of topical application of bisphosphonates on replanted rat molars

Abstract – The purpose of this study was to evaluate the potential usefulness of two bisphosphonates (BPs) (etidronate and zoledronate), compared with that of alendronate, which is a well‐known drug for delayed replantation, in decreasing or preventing inflammatory root resorption and replacement root resorption in replanted teeth. Eighty‐four Sprague Dawley rat maxillary first molars were extracted, dried for 60 min and then replanted after root treatment. The rats were divided into four groups (control, alendronate, etidronate, zoledronate) as following treatments of avulsed root before replantation. At 7, 14, and 28 days postreplantation, the animals were sacrificed and the samples obtained and process for microscopic analysis. The data were statistically analyzed with the SPSS procedure, anova test and each test was complemented by the Tukey’s post hoc test. The result indicated that topical application of alendronate and zoledronate, both nitrogen containing BPs, prevented inflammatory root resorption and inflammatory cell response in the delayed replantation model. Both drugs were demonstrated similar effects in the delayed tooth replantation model (P = 0.9). Etidronate did not prevent inflammatory root resorption and inflammation in the delayed replantation (P < 0.05). No significant differences in replacement root resorption were observed among all drugs. These results suggest that when teeth are dried and not replanted immediately, zoledronate, like alendronate, may prevent root resorption and facilitates the regeneration of periodontal tissues after replantation.     

Replantation of 400 avulsed permanent incisors. 2. Factors related to pulpal healing

Abstract Four hundred avulsed and replanted permanent teeth were examined for pulpal healing. In 110 teeth, the apical foramen was either open or half-open. In 16 teeth, the pulps were extirpated prophylactically. Thus, pulpal revascularization was considered possible in 94 teeth. Revascularization occurred in 32 teeth (34%). Pulp necrosis could usually be demonstrated after 3 weeks. Positive pulpal sensibility and radiographis signs of pulp canal obliteration were usually observed after 6 months. The effect of various clinical factors was examined, such as sex, age, type of tooth replanted, stage of root formation, type and length of extra-alveolar storage, clinical contamination of the root surface, type of cleansing procedure of the root surface, type and length of splinting and the use of antibiotics. Finally, the width of the apical foramen and the length of the root canal were measured on radiographs taken at the time of injury. A multivariate statistical analysis revealed that pulpal revascularization was more frequent in teeth with shorter distances from the apical foramen to the pulp horns. Furthermore, that wet storage (saliva and/or saline) for more than 5 min decreased the chance of pulpal revascularization; whereas dry extraalveolar storage had a monotonous effect on pulpal revascularization, i. e. decreasing chance of revascularization with increasing length of the extraalveolar dry storage. Based on these findings, immediate replantation after brief cleansing in either tap water or saline is recommended.     

Periodontal healing of extracted dogs' teeth air-dried for extended periods and soaked in various media

Abstract The aim of this study was to determine the periodontal healing of replanted dogs’ teeth which, after extended extra-oral dry times, had been soaked in various media before replantation. Incisors and premolars of beagle dogs were root canal treated, extracted and bench dried. The teeth were grouped according to dry times of 30, 45 and 60 minutes. Each group of teeth was soaked in one of three media, Hank's balanced salt solution, Via Span (Belzer UW-CSS, Dupont Pharmaceuticals), or Conditioned Medium (supernatant of confluent culture of human gingival fibroblasts) for 30 minutes before replantation. Controls consisted of teeth extracted and replanted without drying or soaking (negative control), and bench-dried teeth replanted without soaking in the media (positive control). The dogs were killed 6 months after replantation of the teeth, which were prepared for histologic evaluation. Five um cross-sections (every 70 Jim) of the root and surrounding tissue were evaluated for healing/resorption according to Andreasen's criteria. The best healing occurred for the roots which had been immediately replanted. Healing in the positive control groups decreased with increased dry time. For the 30–minute dry time groups, soaking in media had no beneficial effect on periodontal healing compared with the controls. Soaking in ViaSpan resulted in an increased healing incidence for both the 45- and 60- minute bench-dried groups while soaking in the other media had no consistent beneficial effect. It appears from this study that an avulsed tooth that has been left dry for 30 minutes should be replanted immediately without soaking. However, teeth that have been dry for 45 or 60 minutes would benefit from soaking for 30 minutes in ViaSpan.     

Periodontal healing of replanted dog teeth stored in Viaspan, milk and Hank's balanced salt solution

Abstract This study examined, histologically, periodontal healing and root resorption of replanted dogs teeth stored in Viaspan for different time periods and compared these healing patterns to those after storage in milk or Hank's balanced salt solution (HBSS). Seventy-two beagle incisors were endodontically treated, extracted, randomly divided and placed in Viaspan or milk for 6, 12, 24 and 36 h, and Viaspan or HBSS for 36, 48, 72 and 96 h, after which they were replanted. Four negative control teeth were immediately replanted while four positive controls were allowed to dry for one hour before replantation. All replanted teeth were splinted for 14 days. Two months after replantation the clogs were killed and the teeth histologically examined for healing of the supporting tissues. For Viaspan neither replacement nor inflammatory root resorption was seen after 6 and 12 h storage. A statistically significant rise in the incidence of replacement resorption was seen at 24, 36 and 48 h which decreased again at 72 and 96 h to levels equal to storage for 6 and 12 h. The occurrence of inflammatory root resorption was low and significantly increased only at 48 h after which it decreased significantly again. Viaspan proved superior to milk as a storage medium. Teeth stored in HBSS showed healing results similar to those stored in Viaspan.     

Replantation of 400 avulsed permanent incisors. 4. Factors related to periodontal ligament healing

Abstract 400 avulsed and replanted permanent teeth were examined for periodontal ligament (PDL) healing, using standardized radiographic and clinical examination procedures (i.e. percussion test and mobility test). The effect of various clinical factors was examined, such as age and sex of the patient, type of tooth replanted, presence of crown fracture or bone fracture, stage of root development (including apical diameter and length of the pulp), type and length of extra-alveolar storage, clinical contamination of the root surface, type of root surface cleansing procedure, type and length of splinting period and antibiotic therapy. Surface resorption was generally diagnosed after 12 months; while inflammatory resorption and replacement resorption (ankylosis) were usually observed after 1 month and 12 months respectively. Most resorptive processes were diagnosed within the first 2–3 years. However, although rarely, even after 5 and 10 years new resorptive processes could be diagnosed. A univariate statistical analysis of 272 teeth revealed 9 factors significantly related to PDL healing. A subsequent multivariate analysis revealed that the following 4 factors had the strongest impact upon PDL healing, in descending order of significance: Stage of root development; length of the dry extra-alveolar storage period; immediate replantation and length of the wet period (saliva or saline storage). Nonphysiological storage, such as homemade saline and sterilizing solutions (chloramine and alcohol) always led to root resorption. Storage in tap water for more than 20 minutes usually led to root resorption. The common denominator for all these factors related to PDL healing appears to be survival of the PDL cells along the root surface. Based on these findings, immediate replantation is recommended irrespective of stage of root development.     

Periapical tissue reactions to calcium hydroxide and MTA after external root resorption as a sequela of delayed tooth replantation

Clinical experience has shown that most avulsed teeth are replanted after a long extra-alveolar time and dry or inadequate wet storage, causing necrosis of periodontal ligament cells. This condition invariably leads to development of external root resorption, leaving the filling material in contact with the periapical connective tissues. In this study, the periapical tissue reactions to calcium hydroxide (CH) and mineral trioxide aggregate (MTA) were evaluated after occurrence of external root resorption as an expected sequela of delayed tooth replantation. Twenty male Wistar rats (Rattus norvegicus, albinus) had their right upper incisor extracted and maintained in dry storage for 60 min. Then, the dental papilla, enamel organ, pulp tissue, and periodontal ligament were removed, and the teeth were immersed in a 2% acidulated phosphate sodium fluoride solution, pH 5.5, for 10 min. The teeth were randomly assigned into two groups (n = 10), in which the canals were filled with either a CH and saline paste (CH group) or MTA (MTA group). The sockets were irrigated with saline, and the teeth were replanted. After 80 days, it was possible to observe large areas of replacement root resorption and some areas of inflammatory root resorption in both groups. More severe inflammatory tissue reaction was observed in contact with calcium hydroxide compared with the mineral trioxide aggregate. New bone formation was more intense at the bottom of the socket in the MTA group. In conclusion, as far as periapical tissue compatibility is concerned, intracanal MTA can be considered as a viable option for root canal filling in delayed tooth replantation, in which external root resorption is an expected sequela.     

Replantation of teeth and antibiotic treatment

Abstract Administration of antibiotics is usually recommended when a traumatically avulsed tooth is replanted, in order to prevent bacterial contamination. In the present study, permanent lateral incisors of monkeys were extracted, allowed to dry for 1 h and then replanted. Some teeth had their pulp chambers opened labially and left open for 3 wk after replantation. The monkeys were treated with antibiotics (i.m.) either at the lime of replantation or 3 wk after replantation. In some monkeys, antibiotics were placed in the pulpal cavity. Comparisons were made of the effect of endodontic treatment on periodontal healing and root resorption. The monkeys were killed 8 wk after replantation. It was found that after systemic antibiotic treatment at the time of replantation there was no inflammatory root resorption. Also, endodontic treatment at the time of replantation prevented inflammatory root resorption. When systemic antibiotic treatment was instituted 3 wk after (he replantation, there was no reduction of the inflammatory root resorption as compared with teeth without antibiotic treatment. Application of antibiotics in the pulp 3 wk after replantation almost completely eliminated the inflammatory resorption. In all the treatment groups where administration of antibiotics or endodontic treatment had prevented, reduced or eliminated inflammatory root resorption, 30–45% of the root surface area was ankylotic 8 wk after replantation.