Dynamics of dentoalveolar ankylosis and associated root resorption

Abstract The present experimental studies in monkeys were undertaken to study the initiation and progression of dentoalveolar ankylosis of replanted teeth and associated root resorption. Maxillary and mandibular lateral incisors were extracted and replanted after an extraoral period of 15 min or 1 h. Teeth with an extraoral period of 1 h were endodontically treated. Half the number of monkeys were given antibiotics at the time of replantation. The observation periods varied from 2 days to 40 weeks. Irrespective of the length of the extraoral period, initial root resorption and minor areas of ankylosis were found 1 week after replantation. The initial ankylosis was not preceded by root resorption. In teeth replanted after an extraoral period of 15 min the ankylotic area did not increase with increasing time after replantation. Instead the periodontal membrane was re-established, separating the root surface from the alveolar bone. In teeth replanted after an extraoral period of 1 h, the initial ankylotic area increased with increasing time after replantation. Eight weeks and more after replantation, most of the periodontal membrane was replaced by bone covered by osteoblasts and occasional osteoblasts that were in continuity with the endosteal cells outlining the marrow spaces of the alveolar bone. The cementum and dentin were then gradually resorbed with increasing time after replantation. Antibiotics given at the time of replantation reduced the initial inflammation in the periodontal membrane and the inflammatory root resorption after all observation periods and it also seemed to some extent to prevent bacteria from entering the necrotic pulp tissue. Based on the present results it is suggested that root resorption associated with dentoalveolar ankylosis is initiated by endosteal osteoblasts and is thus a hormonally regulated process. This is in contrast to inflammatory root resorption, which seems to be triggered by inflammatory cells.     

Dynamics of dentoalveolar ankylosis and associated root resorption

The present experimental studies in monkeys were undertaken to study the initiation and progression of dentoalveolar ankylosis of replanted teeth and associated root resorption. Maxillary and mandibular lateral incisors were extracted and replanted after an extraoral period of 15 min or 1 h. Teeth with an extraoral period of 1 h were endodontically treated. Half the number of monkeys were given antibiotics at the time of replantation. The observation periods varied from 2 days to 40 weeks. Irrespective of the length of the extraoral period, initial root resorption and minor areas of ankylosis were found 1 week after replantation. The initial ankylosis was not preceded by root resorption. In teeth replanted after an extraoral period of 15 min the ankylotic area did not increase with increasing time after replantation. Instead the periodontal membrane was re-established, separating the root surface from the alveolar bone. In teeth replanted after an extraoral period of 1 h, the initial ankylotic area increased with increasing time after replantation. Eight weeks and more after replantation, most of the periodontal membrane was replaced by bone covered by osteoblasts and occasional osteoblasts that were in continuity with the endosteal cells outlining the marrow spaces of the alveolar bone. The cementum and dentin were then gradually resorbed with increasing time after replantation. Antibiotics given at the time of replantation reduced the initial inflammation in the periodontal membrane and the inflammatory root resorption after all observation periods and it also seemed to some extent to prevent bacteria from entering the necrotic pulp tissue. Based on the present results it is suggested that root resorption associated with dentoalveolar ankylosis is initiated by endosteal osteoblasts and is thus a hormonally regulated process. This is in contrast to inflammatory root resorption, which seems to be triggered by inflammatory cells.     

Experimental replantation of teeth in dogs and monkeys

Fifty-eight teeth were replanted in four monkeys and six dogs. Thirteen teeth were replanted without periodontal membrane, fifteen were dried in air for varying periods of time, and thirty were re-inserted into the alveolus immediately following extraction. Observation periods varied between 8 days and 33 months. Teeth replanted without periodontal membrane never regained a normal attachment apparatus. At first the periodontal space was occupied by soft tissue. This was soon replaced by bone and the establishment of ankylosis was accomplished within 30 days. A normal periodontal membrane was never found in the teeth replanted with a dried periodontal membrane, although the teeth that were dried for short periods exhibited minor areas of normal periodontal attachment. In teeth replanted with vital periodontal membranes, the periodontal membrane was always reformed after replantation. Ankylosis was never observed. Success or failure in replantation seems greatly to depend on the presence or absence of a vital periodontal membrane. The hypothesis is offered that the epithelial remnants of Malassez play a role in the maintenance of the periodontal space.     

Delayed replantation after submucosal storage in order to prevent root resorption after replantation. An experimental study in monkeys

The purpose of this study was to determine the root resorption pattern of teeth autotransplanted to a submucosal site and to determine whether root resorption after replantation could be prevented by delayed replantation of teeth after submucosal storage in order to regenerate damaged periodontal ligament. Permanent teeth were extracted in green Vervet monkeys. One group of teeth was transplanted to a submucosal site and examined histologically in situ. Another group of teeth was autotransplanted to submucosal sites, recovered and replanted either 2 or 6 weeks later. The animals were sacrificed 8 week after replantation and examined histometrically. The following histologic parameters were registered: surface resorption, inflammatory resorption, replacement resorption (ankylosis), periapical inflammatory changes and downgrowth of pocket epithelium. Teeth autotransplanted to submucosal sites developed surface and inflammatory resorption. In half of the cases where teeth were transplanted with a vital periodontal ligaments new formation of bone took place adjacent to the transplant. Delayed replantation after submucosal burial was not found to inhibit the development of ankylosis, but changed the resorption type from direct apposition of bone upon the root surface to apposition of bone after initial resorption.     

Treatment of root surface in delayed tooth replantation: a review of literature

Abstract –  The time elapsed between a trauma and tooth replantation usually ranges from 1 to 4 h. The chances of root surface damage are higher when tooth replantation is not performed immediately or if the avulsed tooth is not stored in an adequate medium. This invariably leads to necrosis of pulp tissue, periodontal ligament cells and cementum, thus increasing the possibility of root resorption, which is the main cause of loss of replanted teeth. This paper presents a comprehensive review of literature on root surface treatments performed in cases of delayed tooth replantation with necrotic cemental periodontal ligament. Journal articles retrieved from PubMed/MedLine, Bireme and Scielo databases were reviewed. It was observed that, when there are no periodontal ligament remnants and contamination is under control, replacement resorption and ankylosis are the best results and that, although these events will end up leading to tooth loss, this will happen slowly with no loss of the alveolar ridge height, which is important for future prosthesis planning.     

Effect of masticatory stimulation on dentoalveolar ankylosis after experimental tooth replantation

Abstract Dentoalveolar ankylosis (replacement resorption) is a serious complication after replantation of avulsed teeth. The purpose of the present study was to investigate the influence of masticatory stimulation on dentoalveolar ankylosis after replantation of avulsed teeth. Monkey upper incisors were extracted, air-dried for 1 h, endodontically treated and replanted. No splinting was used. One group of monkeys was given hard pelleted food, while another group was given soft diet during a healing period of 8 wk. The periodontal conditions were evaluated histologically with a morphometrical method. The replanted teeth of the monkeys given the hard pelleted food had significantly less ankylosis and a larger area of the root surrounded by a normal periodontal membrane than the teeth from the monkeys given a soft diet. In conclusion, development of ankylosis seemed to be partially prevented or reduced by masticatory stimulation.     

Influence of root development on periodontal and pulpal healing after replantation of incisors in monkeys

The influence of root development on periodontal and pulpal healing after replantation was examined in 30 green vervet monkeys (cercopithecus aethiops) in which a total of 50 teeth were replanted. Maxillary central incisors with different stages of root development (immature, young mature and mature root formation) were replanted with untreated pulps or after root canal treatment with gutta percha and Kerr® sealer. The extra-alveolar period in all groups was 18 min. The animals were sacrificed 8 weeks after replantation and the teeth examined histologically. The following histologic parameters were registered for each tooth: surface resorption, inflammatory resorption, replacement resorption (ankylosis), downgrowth of pocket epithelium, periapical inflammatory changes and extent of vital pulp. Histologic analysis showed that the extent of vital pulp was significantly related to the stage of root development, being almost complete in teeth with immature roots and almost totally lacking in young mature and mature teeth. Surface resorption was found with the same frequency in the different root development groups while inflammatory resorption was slightly more frequent in young mature teeth than in mature teeth, a finding possibly related to a protective action of a thick cementum layer in the mature teeth. Replacement resorption was found with almost the same frequency in the different root development groups in non-endodontically treated teeth. As ankylosis is the most important factor determining the prognosis of replanted and autotrans-planted teeth, the present findings indicate that replantation and auto-transplantation of mature teeth could be of clinical use.     

Periodontal and pulpal healing of monkey incisors preserved in tissue culture before replantation.

The effect of delayed replantation and tissue culture as a prevention against root resorption was examined in green Vervet monkeys (Cercopithecus aethiops). Extracted incisors were kept in tissue culture medium (Eagle's medium) for 5--14 days before replantation. The extra-alveolar dry period before tissue culture ranged from to 0 to 60 min. Incisors not subjected to tissue culture served as controls. The animals were sacrificed 8 weeks after replantation. The following histologic parameters were registered for each tooth: surface resorption, inflammatory resorption, replacement resorption (ankylosis), downgrowth of pocket epithelium, and periapical inflammatory changes. The evaluation of the pulp included the extent, recorded in mm, of pulp survival. Histometric evaluation showed that teeth immediately placed in tissue culture medium for 5--14 days showed improved periodontal healing, exhibiting significantly less inflammatory resorption than control teeth immediately replanted. Also the extent of pulp survival was significantly increased in teeth replanted after tissue culture. Teeth bench-dried for 60 min and thereafter placed in tissue culture medium also showed a significant reduction in the amount of inflammatory resorption and increased amount of pulp survival compared with control teeth replanted after the 60-min dry extra-alveolar period. Replacement resorption (ankylosis) was found in all teeth in both groups.     

Effect of stannous fluoride and tetracycline on repair after delayed replantation of root-planed teeth in dogs

Mandibular incisors were extracted and allowed to dry in air for 45 min. They were then root-planed extensively, leaving a cervical collar and the apical region uninstrumented, to prevent direct contact between root surface and alveolar bone after replantation while, at the same time, enabling precise and stable reseating of the tooth. Control teeth were replanted either without further treatment or after treatment with citric acid for 3 min. Experimental teeth were treated before replantation with 1% SnF2 for 5 min, 1% tetracycline HCl for 5 min, or 1% SnF2 followed by 1% tetracycline. Histometric analysis of healing in the root-planed areas showed minimal amounts of inflammatory resorption and ankylosis after 21 days in experimental teeth as compared with the control teeth. A persisting inflammatory reaction in the periodontal ligament without root resorption was, however, frequently seen. The observations confirm that the frequency of adverse healing reactions after delayed replantation of teeth from which nonvital soft tissue remnants have been removed can be reduced by demineralizing the root surface and preventing mechanical trauma to the root surface in the postoperative period. Root surface treatment with SnF2 followed by tetracycline resulted in complete absence of inflammatory resorption and ankylosis in this short-term experiment.     

Effect of lyophilized autologous plasma on periodontal healing of replanted teeth

The purpose of this histologic and autoradiographic study of replanted teeth was to evaluate the beneficial effect, if any, of lyophilized autologous plasma (LAP) application on periodontal healing and to re-examine rates of repair in different areas of the associated periodontium following replantation. Maxillary and mandibular incisors and premolars of three rhesus monkeys were used. Teeth were extracted with forceps and placed in sterile physiologic saline. After 5 minutes each tooth was returned to its socket and immobilized by interproximal acid-etch splints. Splints were removed after 1 week. Of the 48 replants performed, 24 (controls) were replanted as described. Of the 24 experimental teeth, during the 5 minute interval between tooth extraction and replantation, the root surface and the inner socket walls were bathed with 1 ml of the reconstituted LAP-saline solution (800 mg/ml). Replants and animal sacrifice were scheduled to provide observations at 1, 3, 7, 14, 28 and 45 days following replantation. One hour prior to sacrifice, each monkey received an intravenous injection of tritiated thymidine, 1 microCi/gm body weight. Tissue specimens were processed for evaluation following standard procedures. Eight replanted teeth were available for evaluation for each of the six time-points. Four teeth were treated with LAP and four without it. Histologically, tissue sections were examined for epithelial proliferation and attachment, periodontal fibers organization and maturation, inflammatory cell types, presence or absence of cementum resorption and dentoalveolar ankylosis and degree of vascularity of the tissues. For autoradiographic evaluation, the periodontium associated with the replanted tooth was divided into nine spatial cell compartments. In each compartment, labeled tissue cells, epithelial or connective, were counted and recorded. Differences between the control (untreated) replanted teeth and the LAP-treated teeth, at each time-point and within each compartment, were analyzed for significance using the paired t-test. The findings of this study indicate that LAP use enhanced healing by early replacement of the fibrin clot, increased connective tissue cell proliferation, reduction of the inflammatory response and inhibition of root cementum resorption. Periodontal healing and repair occurred more rapidly in the supracrestal or transseptal connective tissue region than within the periodontal membrane space.     

Mechanical removal of necrotic periodontal ligament by either Robinson bristle brush with pumice or scalpel blade. Histomorphometric analysis and scanning electron microscopy

One of the important factors accounting for successful delayed replantation of avulsed teeth is seemingly the type of root surface treatment. Removal of necrotic cemental periodontal ligament remnants may prevent the occurrence of external root resorption, which is the major cause of loss of teeth replanted in such conditions. The purpose of this study was to compare the efficacy of two mechanical techniques for removal of root-adhered periodontal ligament. Preservation or removal of the cementum layer concomitantly with these procedures was also assessed. Forty-five roots of healthy premolars extracted for orthodontic purposes were selected. After extraction, the teeth were kept dry at room temperature for 1 h and then immersed in saline for rehydration for an additional 10 min. Thereafter, the roots were assigned to three groups, as follows: group 1 (control)--the cemental periodontal ligament was preserved; group 2--removal of the periodontal ligament by scraping root surface with a scalpel blade (SBS); group 3--periodontal ligament remnants were removed using a Robinson bristle brush at low-speed with pumice/water slurry (RBP). The specimens were analysed histomorphometrically and examined by scanning electron microscopy. The quantitative and qualitative analyses of the results showed that the RBP technique was significantly more effective than the SBS technique for removal of the periodontal ligament remnants adhered to root surface. Both techniques preserved the cementum layer.     

Intracanal bisphosphonate does not inhibit replacement resorption associated with delayed replantation of monkey incisors

Abstract – Progressive replacement resorption following delayed replantation of avulsed teeth has proved to be an intractable clinical problem. A wide variety of therapeutic approaches have failed to result in the predictable arrest of resorption, with a good long‐term prognosis for tooth survival. Bisphosphonates are used in the medical management of a range of bone disorders and topically applied bisphosphonate has been reported to inhibit root resorption in dogs. This study evaluated the effectiveness of a bisphosphonate (etidronate disodium) as an intracanal medicament in the root canals of avulsed monkey teeth, placed before replantation after 1 h of extraoral dry storage. Incisors of six Macaca fascicularis monkeys were extracted and stored dry for 1 h. Teeth were then replanted after canal contamination with dental plaque (negative control) or after root canal debridement and placement of etidronate sealed in the canal space. A positive control of calcium hydroxide placed 8–9 days after replantation was also included. All monkeys were sacrificed 8 weeks later and block sections were prepared for histomorphometric assessment of root resorption and periodontal ligament status. Untreated teeth showed the greatest extent of root resorption (46% of the root surface), which was predominantly inflammatory in nature. Calcium hydroxide treated teeth showed the lowest overall level of resorption (<30% of the root surface), while the bisphosphonate‐treated group was intermediate (39%). Ankylosis, defined as the extent of the root surface demonstrating direct bony union to both intact and resorbed root surface, was the lowest in the untreated control group (15% of the root surface), intermediate in the calcium hydroxide group (27%) and the highest in the bisphosphonate group (41%). Bony attachment to the tooth root was divided approximately equally between attachment to intact cementum and to previously resorbed dentin. Overall, bisphosphonate resulted in a worse outcome than calcium hydroxide in terms of both root resorption and ankylosis.     

DELAYED TOOTH REPLANTATION AFTER ROOT SURFACE TREATMENT WITH SODIUM HYPOCHLORITE AND SODIUM FLUORIDE: HISTOMORPHOMETRIC ANALYSIS IN RATS

In cases of delayed tooth replantation, non-vital periodontal ligament remnants have been removed with sodium hypochlorite in an attempt to control root resorption. Nevertheless, reports of its irritating potential in contact with the alveolar connective tissue have been described. Therefore, this study evaluated the healing process on delayed replantation of rat teeth, after periodontal ligament removal by different treatment modalities. Twenty-four rats, assigned to 3 groups (n=8), had their upper right incisor extracted and left on the workbench for desiccation during 60 min. Afterwards, the teeth in group I were immersed in saline for 2 min. In group II, root surfaces were scrubbed with gauze soaked in saline for 2 min; and in group III, scrubbing was done with gauze soaked in 1% sodium hypochlorite solution. Thereafter, root surfaces were etched with 37% phosphoric acid and immersed in 2% acidulate-phosphate sodium fluoride solution, at pH 5.5. Root canals were filled with a calcium hydroxide-based paste and the teeth were replanted. The animals were sacrificed 60 days postoperatively and the pieces containing the replanted teeth were processed and paraffin-embedded. Semi-serial transversally sections were obtained from the middle third of the root and stained with hematoxylin and eosin for histomorphometric analysis. Data were analyzed statistically using Kruskal-Wallis and Dunn''s tests. The results showed that root structure and cementum extension were more affected by resorption in group III (p<0.05). All groups were affected by root resorption but the treatment performed in group III was the least effective for its control. The treatment accomplished in groups I and II yielded similar results to each other.     

Effect of dexamethasone on root resorption after delayed replantation of rat tooth

The purpose of this study was to evaluate the effect of dexamethasone after delayed tooth replantation with specific regard to root resorption and ankylosis. In addition, the study was planned to elucidate further the usefulness of the model. Fifty-two maxillary first molar teeth were extracted from 26 Sprague-Dawley white female rats fed 0.4% beta-aminoproprionitrile for 3 days to facilitate the extraction. After extraction, the mesiobuccal root canals were endodontically treated under a microscope to prevent subsequent inflammatory resorption of pulpal origin and were assigned to three groups. Teeth in group 1, the dexamethasone group (n = 22), were demineralized in citric acid (1 min), washed, soaked in 1000 nM dexamethasone solution (3 min), air-dried, and replanted in the original sockets. Total extraoral treatment time for each tooth was controlled to 30 min. Teeth in group 2, the dried-only group (n = 22), were air-dried for 30 min after obturation without any surface treatment and replanted. Teeth in group 3, the immediate group (n = 8), were extracted, not root-filled and replanted immediately into their sockets. All experimental animals were killed at 3 weeks after replantation and evaluated histologically. Forty-three of the 52 teeth were available for histological interpretation. They consisted of six immediate, 18 dried-only, and 19 dexamethasone-treated teeth. The degree of progressive root resorption was significantly less in the dexamethasone-treated group than in the dried-only group (p < 0.05). The dexamethasone-treated group exhibited significantly more bone ankylosis than the dried-only group (p < 0.05). These results indicate that the topical use of dexamethasone may be of value in reducing the degree or rate of progressive root resorption secondary to traumatic avulsion and that the rat is a reasonable model for tooth replantation.     

Extraoral endodontic treatment by retrograde insertion of posts: a long-term study on replanted and transplanted teeth

OBJECTIVE: The aim of the study was to investigate the healing results of teeth replanted or transplanted in different indications and treated by extraoral root canal therapy. STUDY DESIGN: Extraoral root canal treatment was performed from a retrograde direction with posts made of ceramics or titanium. Preoperatively, the pulp status was classified as definitely infected (n = 47) or not infected/symptomless (n = 78), and the condition of the periodontal ligament (PDL) was classified as damaged (n = 50) or not damaged (n = 75) according to trauma type and extraoral storage. The healing after replantation or transplantation was diagnosed as functional, ankylosis, or infection depending on clinical and radiographic findings. RESULTS: In total, 125 teeth in 99 patients were replanted or transplanted. Mean observation period was 44.4 months. Teeth with a less damaged PDL in no case exhibited ankylosis/replacement resorption after a mean observation period of 53 months. Teeth without preoperative infection of the pulp in no case showed infection-related complications after a mean observation period of 30 months. Teeth classified as definitely infected before treatment had a high frequency of continuous periradicular bone and root resorption. CONCLUSIONS: The extraoral insertion of posts appeared to inflict no additional damage to the PDL that was clinically relevant. Infection-related complications were prevented. Teeth that were classified as definitely infected at the time of treatment had a low rate of healing and should undergo conventional root canal disinfection before this surgical procedure is applied.     

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.     

Re- and allotransplantation of teeth--an experimental study in monkeys

In each of six monkeys one of the permanent lateral incisors with uncompleted root development was replanted. At the same time the contralateral incisors in four of the monkeys were allotransplanted by pairs. The remaining two contralateral incisors served as controls. After 4 weeks and 4 months, respectively, three monkeys were decapitated and the upper lateral incisors with adjacent periodontal tissue were examined histologically. The replanted teeth in five cases had a vital pulp. In the sixth case, however, the replanted incisor exhibited pulpitis and partial necrosis of the pulp. The periodontal membrane had a normal histologic appearance. In two cases a small area of arrested root resorption was observed. With the allotransplanted teeth the histologic appearance was altered. After 4 weeks a pronounced inflammatory reaction was observed in both the pulpal tissue and the periodontal membrane. The pulp was in most cases necrotic, and marked root resorption was observed. Most of the allotransplanted teeth were resorbed and replaced by an irregular hard tissue that resembled osteoid, which in many cases was connected with the tooth remnants by ankylosis. These results indicate that allotransplanted teeth, in contrast to replanted teeth, exhibit the characteristic features of an allograft rejection, including an inflammatory reaction and resorption.     

Clinical observations regarding the treatment of traumatically avulsed mature teeth. Part 1

A documented case involving the simultaneous avulsion of two maxillary incisors, intraorally and extraorally, was reported. Long-term observations following replantation treatment revealed several interesting clinical features: The prognosis of replanted teeth may be more favorable following intraoral avulsions. The intrusion phenomenon associated with replanted incisors appears to be directly related to replacement root resorption or ankylosis; occlusal forces may be a factor. Teeth extraorally avulsed for a few hours may still provide a useful function, albeit temporary, with replantation treatment. These teeth may not reveal clinical ankylosis or replacement resorption for periods of 1 to 2 years, or possibly longer, following replantation. Long-term studies can help evaluate replantation techniques.     

The effect of saline storage before replantation upon dry damage of the periodontal ligament

Abstract The effect of 30 min of saline storage before replantation of teeth, which had been dried out for 30 min, was studied in 10 Green Vervet monkeys (Cercopithecus aethiops). Maxillary central incisors were extracted and dried out for 30 min, after which 1 incisor was replanted and the other transferred to a saline solution for 30 min before replantation. No splinting or endodontic treatment was carried out. The teeth were examined after 8 wk. Histometric analysis showed identical extent of root resorption in the 2 groups, with ankylosis being the dominant resorption type, and with very limited pulpal repair in either group. It is concluded that saline storage under the experimental conditions chosen had no effect on development of root resorption or pulpal repair, presumably because 30 min dry storage had inflicted close to maximal damage on the periodontal ligament at the root surface. On the other hand, it is of clinical importance that a certain delay in the replantation procedure does not influence periodontal and pulpal healing, as long as the tooth is kept in saline storage. This suggests that replantation under these conditions can be reserved for dental professionals, rather than favoring immediate replantation by anyone ‘on-the-spot’.     

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.