Avulsion

Pre-Replantation Storage of Avulsed Teeth: Fact and Fiction

David J. Kenny, DDS, PhD; Edward J. Barrett, DDS, MSc

Copyright 2001 Journal of the California Dental Association.

Drs. Kenny and Barrett will present "Dental Trauma: Decision Time for the Clinician" at CDA’s Spring Scientific Session in Anaheim, Calif. The presentation will be held twice: from 9:30 a.m. to noon and continuing from 2 to 4:30 p.m. on Friday, April 20, in Ballroom C of the Anaheim Convention Center; and from 9 to 11:30 a.m. and continuing from 1:30 to 4 p.m. on Saturday, April 21, in Room 304 C/D.

Recent laboratory and clinical studies have proven that there is a rapid decrease in the regenerative potential of normal periodontal ligament the longer an avulsed tooth is out of the socket. These findings make some guidelines for the management of avulsed teeth inaccurate. This paper will review the effects of pre-replantation storage on periodontal ligament healing. In addition, current management recommendations are reviewed and suggestions for change presented.

The ideal method for management of an avulsed permanent tooth is immediate replantation.^1-3 However, immediate replantation continues to be the management exception due to accident-associated factors such as a child’s emotional state at the time of injury, lack of knowledge or confidence of acute caregivers, and consent issues.⁴ The results of recent clinical and laboratory studies have led to a redefinition of immediate replantation from 30 minutes to less than five minutes. Consequently, delayed replantation is the only option that is available to clinicians by the time a patient arrives at a dental office.^3,5-9 The preferred outcome for replanted teeth, periodontal ligament regeneration, is dependent upon the extra-alveolar duration and storage conditions prior to replantation.^7,10-15 Both of these uncontrollable variables are largely in the hands of caregivers who do not have dental training.⁴

Although several consensus-based guidelines for management of avulsed teeth have been published, they are not entirely scientifically based, especially with respect to pre-replantation storage.^16-20 This review is focused on the effects of pre-replantation storage on periodontal ligament healing. The facts and fiction of current management recommendations are reviewed, and suggestions for change are presented.

Periodontal Ligament Cells

Fibroblasts are the predominant cell type in the periodontal ligament and make up approximately 25 percent of all periodontal ligament cells. Although the origins and regulation of fibroblasts are not clear, it is currently thought that fibroblasts arise from a constantly renewing stem cell system. These still-unidentified stem cells (also called progenitor cells) produce different fibroblast phenotypes.^21,22 Stem cells may be located adjacent to blood vessels in the periodontal ligament or within vascular channels of the adjacent alveolar bone.

Avulsion injuries rupture the periodontal ligament and immediately initiate a cascade of wound-healing responses. The periodontal ligament fibroblasts are critical for regeneration and repair and large increases in their formation and differentiation have been observed after wounding.²¹ Furthermore, the variety and function of fibroblasts that repopulate the periodontal ligament may dictate both the form and type of tissue that will be produced during healing.^21,22 The healing pattern that occurs can either be regeneration of typical periodontal ligament tissues with normal function or repair with scarring. Scarring is characterized by replacement resorption of the root and ankylosis. While replacement resorption and ankylosis are expected outcomes and represent an acceptable result of replantation in an adult, they inevitably lead to gingival disharmony and infraocclusion following growth in pre-adolescents.

Unfortunately, most avulsions occur prior to the adolescent growth spurt.⁹ In these cases cellular metabolism and activity are accelerated compared with adults. The unsightly esthetics produced by infraocclusion often dictate that extraction will be the chosen outcome. If treatments are to be developed that will lead to regeneration of the periodontal ligament after avulsion, the ability to influence stem cell differentiation must first be developed. Only when this level of cell management is developed will prevention of ankylosis be possible.

Periodontal Ligament Cell Environment Following Avulsion

Acute Changes

* Ischemic injury: Ischemia occurs because the avulsed tooth becomes an inadvertent free graft. When free grafts are planned in periodontal surgery or solid organ transplantation, the tissue is maintained in chilled, isotonic, ion-balanced solutions to slow cellular metabolism. While the effects of ischemia on root-side periodontal ligament cells cannot be ignored, they are likely eclipsed by other acute factors.

* Desiccation: The drying of root-side periodontal ligament cells begins soon after the tooth is avulsed. The tooth may be held in a hand or a paper tissue or set aside to air-dry in the confusion that accompanies an avulsion injury. Almost all avulsed teeth experience a period of desiccation that may go unreported as it is often followed by placement of the tooth in a liquid medium for transport.

* Chemical injury: This is usually caused by imbibition and cell rupture due to immersion in media with inappropriate ion strengths. A variety of interim storage media have been suggested. Public education has encouraged the use of milk. Avulsed teeth are typically stored in milk; tap water; saliva; and, very rarely, ion-balanced solutions. Consequently, teeth often arrive with a "history" of chemical injury.

* Mechanical injury: Blunt trauma produces torn periodontal ligament fibers and ruptured cells, cementum, and blood vessels. Mechanical injury to the pulpal neurovasculature produces ischemic damage to the dental pulp.

Subacute/Chronic Changes

If the tooth has not been replanted, a blood clot will form in the socket. Inflammatory cells, the neutrophils and macrophages, migrate into the clot and prepare the way for development of granulation tissue. Fibroblasts proliferate and migrate into the coagulum as well. They produce dense connective tissue and differentiate into osteoblasts that form new bone.²³ Connective tissue maturation may terminate the opportunity to replant a tooth as it becomes increasingly difficult to debride the socket to facilitate replantation. However, it has been shown in an animal model that socket-side changes favoring osteoblast and osteoclast differentiation occur less than two hours following an avulsion.²⁴ Replantation may be subject to time constraints that are both cellular and mechanical.

If a tooth has been replanted, then inflammation is prolonged due to the complexity of the periodontal ligament cellular domain.²⁵ If regeneration of a normal periodontal ligament is to occur, numerous cell types must form multiple junctional complexes. It has been hypothesized that periodontal ligament, bone and cementum cell populations arise from progenitor cells within the socket-side periodontal ligament and bone.^21,22 Furthermore, the differentiation of progenitor cells is thought to be regulated by extracellular molecules and cytokines. For periodontal ligament fibers to insert onto cementum, avascular cementum must be repaired and infection must be controlled. The damaged cells attached to the root-side periodontal ligament will be removed by macrophages from the alveolar-side periodontal ligament . When the dental pulp becomes necrotic, toxic cellular breakdown products will leak through dentinal tubules where cementum has been torn loose during the avulsion.

A few days after replantation, a chronic inflammatory response characterized by proliferation of fibroblasts and liberation of a collagen matrix and vascular elements of the periodontal ligament begins and remains very active during the next couple of weeks. The inflammatory process is also associated with an infiltration of lymphocytes, macrophages and plasma cells into the periodontal ligament. Furthermore, bacterial infection will cause neutrophils to release lysosomal enzymes that will cause local tissue destruction. Bacteria and foreign bodies introduced following replantation may further stimulate the chronic inflammatory reaction.^21,22,26

Dentists must rely on clinical signs to determine the progress of regeneration or repair: altered mobility, percussion tone, and radiographic changes are important aids in the differentiation of the two processes. Laboratory studies that use periodontal ligament tissue from animal and human sources allow isolation of variables in order to observe the cellular aspects of the competing healing processes. While extrapolation to human healing is often difficult, much useful information has been gleaned over the past decade. Numerous investigations of periodontal ligament cell responses to storage media have yielded consistent results and provide a high level of scientific evidence. Furthermore, laboratory evidence of cell degeneration during extra-alveolar storage is largely supportive of reported clinical outcomes even though the influence of specific cellular mechanisms are unknown.

Laboratory Measures of Periodontal Ligament Cell Activity

Early studies that concentrated on measurement of cell vitality have been supplemented by assays of cell division, reproductive capacity, and immunohistochemical marker expression.

* Cellular vitality. There are a number of laboratory tests that measure membrane integrity, a requirement for cellular vitality. Stains such as Trypan blue attach to intact cell structures. Membrane integrity may be assessed by measuring the leakage of tritiated-uridine from cells. These tests do not offer any information about the functional, reproductive, or proliferative abilities of cells. Vital dye assays are only weakly correlated with tooth survival following replantation and illustrate the importance of newer functional test methods.

* Plating efficiency. Cells must attach to their substrate in order to synthesize and secrete matrix proteins. Measurement of cell attachment ability is called plating efficiency.

* Mitogenic assay. This test measures the functional capacity of all cells in a medium to attach to their substrate and proliferate. This total population assay includes both mature fibroblasts and progenitor cells. Uptake of ³H-thymidine by cells increases with increased mitotic activity and is a measurable parameter.

* Clonogenic capacity. This test estimates the proportion of progenitor cells in a population that demonstrate proliferative and colony-forming capabilities. It is presumed to be a measure of the ability of periodontal ligament cells to attach, proliferate, and recolonize the root surface following replantation. This test is most sensitive to changes in storage conditions.

* Immunohistochemical markers. These tests use antibody "probes" to identify the actual products of cellular metabolism. They give evidence of type, location, and amount of cellular byproducts and allow detection of changes in the activities of cell populations.

A number of cellular studies that have employed different methods are essentially in agreement. The laboratory studies are also consistent with clinical outcome studies by investigators from different centers. The evidence base for the effects of extra-alveolar storage on avulsed teeth is well-established.

Effects of Pre-Replantation Storage

* Desiccation is deadly (Figure 1). Outcome studies have demonstrated that even with immediate (in less than five minutes) replantation, normal periodontal ligament healing was evident in only 73 percent of teeth.³ By 10 minutes, only half the replanted teeth in a separate study exhibited normal periodontal ligament healing.² By 15 minutes, an in vitro study of human periodontal ligament progenitor cells demonstrated that periodontal ligament cells exhibited a very low ability to reproduce themselves (clonogenic capacity 4.5 percent), and by 30 minutes periodontal ligament cells were incapable of reproduction.¹¹ Desiccation appears to select for osteogenic cells at the expense of periodontal ligament fibroblasts. This would increase the incidence of ankylosis with time.²⁸ Numerous investigators have demonstrated early effects of desiccation ^29-31 while others have shown that within 30 to 60 minutes of desiccation all periodontal ligament cells die.^14,27,32

* Water is acceptable for storage for up to 15 minutes if there are no alternatives. Cell damage due to imbibition is inevitable, but it is less damaging than desiccation for this very short period.^33,34

* Saliva is as safe as room temperature milk for up to 30 minutes (Figure 1) as periodontal ligament progenitor cells retain an acceptable clonogenic capacity (7.6 percent). However, storage in saliva results in a precipitous decrease in functional capacity within 60 minutes. Separate studies support the acceptability of storage in saliva for up to 30 minutes. ^12,35,36

* Milk is acceptable for up to 60 minutes based upon its ability to support the clonogenic capacity of periodontal ligament cells even if the milk is allowed to warm to ambient temperature (Figure 2). However, if the milk is kept chilled, the cooler temperatures reduce cell swelling, increase cell viability, and improve cell recovery.^12,29,37 Clonogenic capacity can be maintained at the same level for an additional 45 minutes simply by keeping the milk chilled in an ice pack or refrigerator.³⁵ There is only anecdotal evidence that storage on ice leads to extensive root resorption.³

* Balanced Salt Solution is similar to milk but is not superior (Figure 2).^13,22,35

Fact and Fiction

Recent investigations have focused on sophisticated and rare storage media such as balanced salt solution (an ophthalmic irrigating solution) or ViaSpan (a tissue culture medium). However, numerous cell biology and clinical outcome studies have clearly identified desiccation as the principal avoidable threat to root-side periodontal ligament cells. Desiccation for as few as 15 minutes has profound effects on progenitor cell growth and differentiation. If a tooth has been dried for 30 minutes, there will be no functional periodontal ligament cells on the root, and by as few as 45 minutes all periodontal ligament cells will be dead. Patients often arrive at hospital emergency departments or dental offices with avulsed teeth in milk. Meticulous record taking of the extra-alveolar history of the tooth will often identify a desiccation time of more than 30 minutes while milk was located or an extended (more than 15 minutes) exposure to tap water. Either condition will lead to selection of osteogenic progenitor cells or simply kill all cells on the root-side periodontal ligament and render subsequent storage media irrelevant.

The patient’s bloody saliva is always present at the point of injury and should be used immediately to prevent desiccation. Guidelines should emphasize the need for immediate hydration with saliva (less than 45 minutes) or water (less than 15 minutes) while securing milk and ice. The safety of both of these time intervals is supported by a number of in vitro investigations. Although the patient’s own saliva is acceptable and immediately available, the recommended use of the buccal sulcus for storage should be reconsidered as risky and unnecessary in a traumatized child who may be upset and crying. It would be safer for the patient to spit or drool into a receptacle and keep the tooth wet in the saliva-and-blood mixture while a better storage medium is sought. It is easy to forget that except for the rare cases when a dentist is either a coach or just happens to be present, the primary caregiver for dental injuries is most frequently another parent or simply a passerby.

Milk and ice can usually be procured within a quarter-hour while the patient’s saliva protects the tooth from desiccation. Milk will protect periodontal ligament cells beyond two hours if the milk is packed in ice or kept in a refrigerator. The value of storage at 39 degrees Fahrenheit is strongly supported by cell studies and medical practice for solid organ transport and should be encouraged. Cell physiology studies have shown the protective effect of low-temperature storage on root-side periodontal ligament cells. However, the linkage to improved clinical outcomes such as periodontal ligament regeneration, replacement resorption, ankylosis, or prolonged survival has not yet been made. This linkage will be difficult to demonstrate in humans due to multiple confounding variables.

American Academy of Endodontics guidelines still state that inflammatory resorption, replacement resorption, ankylosis, and tooth submergence are potential complications of replantation. Evidence supports these clinical signs as expected outcomes rather than potential complications. In fact, virtually all replanted teeth will eventually be extracted for a variety of reasons that can include root loss due to inflammatory resorption, unsatisfactory esthetics due to infraocclusion, or crown fracture as a consequence of marginal resorption. Survival following replantation is greater for patients who are in late adolescence or adulthood when they sustain their injury.

The use of balanced salt solution seems to have found its way into some guidelines with a modicum of scientific support. For instance, Krasner³⁸ cited the work of others as evidence that storage in balanced salt solution may "reconstitute" periodontal ligament cells. Cvek and colleagues¹⁰ and Matsson and colleagues³⁹ assumed that storage in isotonic medium would wash off breakdown products of autolysed cells that acted as a substrate for bacteria or as a chemotactic agent for inflammatory cells.¹⁰ The clinical outcome study by Andreasen and colleagues found that a combination of wet and dry storage resulted in a significantly lower healing rate for teeth stored for greater than 20 minutes and saline storage significantly decreased periodontal ligament healing in teeth stored dry for up to nine minutes.³ For teeth allowed to desiccate for longer durations, no significant difference could be found in periodontal ligament healing rates between dry storage and dry storage followed by saline storage.³ Matsson’s group studied replanted dog incisors that had been stored in either dry conditions, dry followed by balanced salt solution, or in balanced salt solution alone.³⁹ Even though ankylosis was significantly reduced in teeth stored in balanced salt solution, the percentage of root sites with external resorption was approximately the same for teeth stored dry (16 percent) and teeth stored dry followed by wet storage in balanced salt solution (14 percent). Therefore it cannot be concluded that balanced salt solution rejuvenates degenerating periodontal ligament cells from the results of this study alone.³⁹ Whether "reconstituted" cells are phenotypically/physiologically normal is unknown as no studies have been conducted to determine the properties of "reconstituted" cells.

Krasner and Person investigated the success rate of replanted teeth that had been stored in balanced salt solution in a study with multiple methodological and data-interpretation problems.⁴⁰ They stated that teeth with an extra-alveolar duration of from 15 to 120 minutes that were subsequently stored in balanced salt solution showed a "success rate" of 91 percent. This included teeth that showed radiographic signs of root resorption. There was no indication that a standardized protocol for the treatment of the avulsed teeth such as the American Association of Endodontists recommended guidelines was followed.¹⁶ Interexaminer variability was not evaluated statistically for radiographic interpretation of ratings, and the data did not describe initial storage conditions and extra-alveolar duration before placement in balanced salt solution. Therefore, it cannot be concluded whether "success" at the 30-month interval was related to the storage treatment, the extra-alveolar duration before replantation, or both.

Due to the many variables in this study, the conclusions made by Krasner and Person that balanced salt solution reconstitutes periodontal ligament cells cannot be substantiated.⁴⁰ Similarly, none of the previous studies produced evidence that balanced salt solution storage following dry storage "reconstitutes" periodontal ligament cells. The definitive study of Doyle and co-workers showed no significance with or without soaking desiccated human periodontal ligament cells in either balanced salt solution or milk.⁴¹ This study further emphasized the fatal effects of 30 minutes of drying on root-surface periodontal ligament cells. Clearly the weak evidence for resurrection of periodontal ligament cells with balanced salt solution should be considered inadequate to support recommendations for such treatment in humans. Furthermore, the concept of cellular resurrection with balanced salt solution should not be considered for inclusion in guidelines.⁴¹

Only if a tooth has been protected from desiccation and potentially hostile storage conditions should it be considered a candidate for long-term (more than 2 hours) storage if early replantation is an option. Ashkenazi and co-workers have recently shown that beyond two hours, room temperature balanced salt solution is an acceptable storage medium as long as viable cells are present.⁴² Nevertheless, the survival of root-side periodontal ligament cells has still not been linked to prolonged survival of replanted teeth.

In fact, storage media and methods are available to prolong the viability of root surface periodontal ligament cells even though they may select for osteogenic phenotypes rather than periodontal ligament fibroblasts. The fiction is that once periodontal ligament cells are dead, they can be resurrected by dipping them in balanced salt solution, milk or any other medium. It is also fiction for dentists to delude themselves or their patients with the belief that replanted teeth will last as long as normal teeth. The available literature clearly demonstrates that unless an avulsed tooth is immediately replanted, it is destined to fail as a result of progressive root resorption.^2,3,6,9 Extraction can be as early as one year in a preadolescent with immature roots to decades for adults with fully formed roots. Table 1 illustrates the authors’ interpretation of an evidence-based storage protocol.

Authors

David J. Kenny, DDS, PhD, is director of dental research and graduate studies at the Hospital for Sick Children and professor of dentistry, University of Toronto, Ontario, Canada.

Edward J. Barrett, DDS, MSc, is coordinator of the Dental Trauma Unit at the Hospital for Sick Children and assistant professor of Dentistry, University of Toronto.

References

1. Andreasen J, A time-related study of periodontal healing and root resorption activity after replantation of mature permanent incisors in monkeys. Swed Dent J 4:101-10, 1980.

2. Andersson L, Bodin I, Avulsed human teeth replanted within 15 minutes -- A long-term clinical follow-up study. Endod Dent Traumatol 6:37-42, 1990.

3. Andreasen JO, Borum MK, et al, Replantation of 400 avulsed permanent incisors. 4. Factors related to periodontal ligament healing. Endod Dent Traumatol 11:76-89, 1995.

4. Hamilton F, Hill FJ, Mackie IC, Investigation of lay knowledge of the management of avulsed permanent incisors. Endod Dent Traumatol 13:19-23, 1997.

5. Andreasen J, Hjorting-Hansen E, Replantation of teeth. I. Radiographic and clinical study of 110 human teeth replanted after accidental loss. Acta Odontol Scand 24:263-86, 1966.

6. Andreasen JO, Borum MK, et al, Replantation of 400 avulsed permanent incisors. 1. Diagnosis of healing complications. Endod Dent Traumatol 11:51-8, 1995.

7. Andreasen JO, Borum MK, et al, Replantation of 400 avulsed permanent incisors. 2. Factors related to pulpal healing. Endod Dent Traumatol 11:59-68, 1995.

8. Andreasen JO, Borum MK, et al, Replantation of 400 avulsed permanent incisors. 3. Factors related to root growth. Endod Dent Traumatol 11:69-75, 1995.

9. Barrett EJ, Kenny DJ, Survival of avulsed permanent maxillary incisors in children following delayed replantation. Endod Dent Traumatol 13:269-75, 1997.

10. Cvek M, Granath LE, Hollender L, Treatment of non-vital permanent incisors with calcium hydroxide. III. Variation of occurrence of ankylosis of reimplanted teeth with duration of extra-alveolar period and storage environment. Odont Revy 25:43-56, 1974.

11. Lekic P, Kenny D, et al, Relationship of clonogenic capacity to plating efficiency and vital dye staining of human periodontal ligament cells: implications for tooth replantation. J Periodont Res 31:294-300, 1996.

12. Blomlof L, Milk and saliva as possible storage media for traumatically exarticulated teeth prior to replantation. Swed Dent J Suppl 8, 1981.

13. Blomlof L, Otteskog P, Hammarstrom L, Effect of storage in media with different ion strengths and osmolalties on human periodontal ligament cells. Scand J Dent Res 89:180-7, 1981.

14. Lindskog S, Blomlof L, Hammarstrom L, Mitosis and microorganisms in the periodontal membrane after storage in milk or saliva. Scand J Dent Res 91:465-72, 1983.

15. Oikarinen KS, Seppa ST, Effect of preservation media on proliferation and collagen biosynthesis of periodontal ligament fibroblasts. Endod Dent Traumatol 3:95-9, 1987.

16. Treatment of the Avulsed Permanent Tooth: Recommended Guidelines of the American Association of Endodontists. Chicago, Ill, 1995.

17. Andreasen JO, Andreasen F, Textbook and Color Atlas of Traumatic Injuries to the Teeth. Munksgaard, Copenhagen,1994.

18. Protocols for Clinical Pediatric Dentistry, 3rd ed. The Journal of Pedodontics Inc, Boston, 1995.

19. Gregg TA, Boyd DH, Treatment of avulsed permanent teeth in children. UK National Guidelines in Paediatric Dentistry. Royal College of Surgeons, Faculty of Dental Surgery. Int J Paediatr Dent 8:75-81, 1998.

20. Casamassimo PS, In critical condition: management of dental trauma. Ped Dent 17(5):330-1, 1995.

21. McCulloch CAG, Bordin S, Role of fibroblast subpopulations in periodontal physiology and pathology. J Periodont Res 26:144-54, 1991.

22. Lekic P, McCulloch CAG, Periodontal ligament cell populations: The central role of fibroblasts in creating a unique tissue. Anat Rec 245:327-41, 1996.

23. Lin W-L, McCulloch CAG, Cho M-I, Differentiation of periodontal ligament fibroblasts into osteoblasts during socket healing after tooth extraction in the rat. Anat Rec 240:492-506, 1994.

24. Morris ML, Moreinis A, et al, Factors affecting healing after experimentally delayed tooth transplantation. J Endod 7:80-4, 1981

25. Nguyen NH, Miller M, Landry RG, Factors influencing repair and regeneration following replantation. J Can Dent Assoc 58:407-11, 1992.

26. Beertsen W, McCulloch CAD, Sodek J, The periodontal ligament: a unique, multifunctional connective tissue. Periodontol 2000 13:20-40, 1997.

27. Blomlof L, Lindskog S, et al, Storage of experimentally avulsed teeth in milk prior to replantation. J Dent Res 62:912-6, 1983.

28. Lin DG, Kenny D, et al, Storage conditions of avulsed teeth affect the phenotype of cultured human periodontal ligament cells. J Periodont Res 35:42-50, 2000.

29. Rozenfarb N, Kupietzky A, Shey A, Milk and egg albumen are superior to human saliva in preserving human skin fibroblasts. Pediatr Dent 19:347-8. 1997.

30. Soder PO, Otteskog P, et al, Effect of drying on viability of periodontal membrane. Scand J Dent Res 85:164-8, 1977.

31. Kinirons MJ, Boyd DH, Gregg TA, Inflammatory and replacement resorption in reimplanted permanent incisor teeth: a study of the profiles of 84 teeth Endod Dent Traumatol 15:269-72, 1999.

32. Modeer T, Dahllof G, Otteskog P, Effect of drying on human periodontal ligament repair in vitro. J Int Assoc Dent Child 15:15-20, 1984.

33. Blomlof L, Andersson L, et al, Periodontal healing of replanted monkey teeth prevented from drying. Acta Odontol Scand 41:117-23, 1983.

34. Bibby KJ, McCulloch CA, Regulation of cell volume and [Ca2+]i in attached human fibroblasts responding to anisosmotic buffers. Am J Physiol 266:C1639-49, 1994.

35. Lekic PC, Kenny DJ, Barrett EJ, The influence of storage conditions on the clonogenic capacity of periodontal ligament cells: implications for tooth replantation. Int Endod J 31:137-40, 1998.

36. Andreasen JO, Effect of extra-oral period and storage media upon periodontal and pulpal healing after replantation of mature permanent incisors in monkeys. Int J Oral Surg 10:43-53, 1981.

37. Blomlof L, Otteskog P, Viability of human periodontal ligament cells after storage in milk or saliva. Scand J Dent Res 88:436-40, 1980.

38. Krasner PR, Rankow HJ, Ehrenreich A, Apparatus for storing and transporting traumatically avulsed teeth. Compendium 10:232-4, 1989.

39. Matsson L, Andreasen J, et al, Ankylosis of experimentally reimplanted teeth related to extra-alveolar period and storage environment. Pediatr Dent 4:327-9, 1982.

40. Krasner P, Person P, Preserving avulsed teeth for replantation. J Am Dent Assoc 123:80-8, 1992.

41. Doyle DL, Dumsha TC, Sydiskis RJ, Effect of soaking in Hank’s balanced salt solution or milk on PDL cell viability of dry stored human teeth. Endod Dent Traumatol 14:221-4, 1998.

42. Ashkenazi M, Marouni M, Sarnat H, In vitro viability, mitogenecity and clonogenic capacity of periodontal ligament cells after storage in four media at room temperature. Endod Dent Traumatol 16:63-70, 2000.

To request a printed copy of this article, please contact / Dr. David J. Kenny, DDS, PhD, Department of Dentistry, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, Canada, M5G 1X8 or at HSCDent@sickkids.on.ca

Figure 1. Effects of dry storage (top) and saliva storage (bottom). Time bars illustrate acceptable, indeterminate and fatal damage to cells that remain in the root-side periodontal ligament following an avulsion. Upper references are to cellular studies and lower references are to clinical outcome studies of teeth according to storage duration.

Figure 2. Effects of room temperature milk storage (top) and balanced salt solution storage (bottom). Time bars illustrate acceptable and indeterminate damage to cells that remain in the root-side periodontal ligament following an avulsion. Upper references are to cellular studies and lower references are to clinical outcome studies of teeth according to storage duration.

Table 1. Advice for Parents and Caregivers

1. The most important factor for healing is immediate (less than five minutes) replantation.

2. Drying of the cells on the root surface drastically reduces their ability to assist healing.

3. Replantation is always superior to storage out of the mouth.

4. Immediate storage in the patient’s own saliva followed by transfer to cold milk will maintain the root surface cells’ ability to assist healing for up to one hour.

5. Keep the milk (and tooth) cold by packing the milk in ice during storage.

6. The first person prepared to replant the tooth should do so. Do not wait for a dentist.

7. Water storage damages root surface cells. Use water to rinse the root before replantation if saline is unavailable.