Tooth avulsion and replantation - A reviewHammarstrom L, Pierce A, Blomlof L, Feiglin B, Lindskog S.Tooth avulsion and replantation - A review. Endod Dent Trau-matol 1986; 2: 1-8.

Abstract - The major causes of post-replantation tooth loss areinflammatory root resorption and root resorption associatedwith ankylosis. Recent studies have concentrated on delineatingthe cellular interactions in the pulp and periodontium in order tomore fully understand the various factors affecting the prognosesof such teeth. The aim of this report is to discuss the nature of thepathology responsible for tooth loss following avulsion and toreview recent replantation and attachment studies.

LIBRARYb^H-.JL Or U . J I I A L

Lars Hammarstrom, Angela Pierce, Leif

Blomiof, Barry Faigiin^ and Sven Lind-

skog

Department of Oral Pathology, School of Dentistry,Karolinska Insfitutet, 'Department of Periodontoio-gy, Skanstull Public Dental Health, Stockholm, Swe-den, 'Department of Restorative Dentistry, Facultyof Dental Science, The University of Melbourne,Melbourne, Australia

Key words: ankylosis, replantation, review, rootresorption, tooth avulsion.

Professor L. Hammarstrom, Dept. ot Oral Pathol-ogy, School ot Dentistry, Karolinska Institutet, Box4064, S-141 04 Huddlnge, Sweden.

Accepted for publication 11 July 1985.

A variety of treatment procedures have been advo-cated in the past for the management of avulsed orexarticulated teeth (1). The majority of these weredirected at the prevention of root resorption associ-ated witli inflammation or ankylosis, the majorcauses of tooth loss following replantation. However,many treatment methods have been unsuccessful,and tooth loss following replantation is a disconcert-ing but not uncommon clinical observation. It isapparent that a basic understanding of the cellularinteractions occurring at the root surface and withinthe periodontal membrane is essential to the success-ful management of the avulsed tooth. The followingdiscussion aims to examine these interactions in thecontext of recent replantation and attachmentstudies.

The normal periodontium

The dental root is separated from the alveolar boneby a thin layer of connective tissue, the periodontalmembrane. Not only does this tissue form an attach-ment between the root and bone, but it also servesto maintain the integrity of the root. Furthermore,it is unique in nature, containing a web of epithelialcells (the epithelial rests of Malassez) which aresurrounded by connective tissue. Absence of thisperiodontal membrane zone results in ankylosis, aunion between tooth and bone (2,3).

Collagen fibers form a major part of the cemen-tum and are responsible for its attachment to theperiodontal membrane. Recently, attention has

been focused upon the complex nature of the outer-most layers of the root: the granular layer of Tomes,the intermediate cementum and, closest to the peri-odontal membrane, the dental cementum. It hasbeen suggested that the intermediate cementum,forming an effective barrier between the dentin andthe periodontal membrane, is critical to the progressof root resorption (4,5). Furthermore, it can not beregenerated once it has been damaged. An appreci-ation of the development and function of these lay-ers is essential to the understanding of periodontalrepair.

Root resorption associated with inflammation or ankylosis:

The major causes of tooth loss following replantation

Under normal circumstances, invasion of the peri-odontal membrane by bone, and dentoalveolarankylosis (union between tooth and bone) are notobserved. However, these tissues are not static. Thebone socket surface is continuously remodelled inresponse to functional demands, and cementum,although not normally resorbed, grows slowly butcontinuously throughout life.

In contrast, pathological resorption of the dentalroot is often found on the external surface of re-planted teetli in association with trauma and infec-tion or with dentoalveolar ankylosis. In the past,root resorption has been subdivided into static andseparate entities which, labelled accordingly, in-ferred a difference in the basic resorptive mechan-isms. This has become somewhat misleading and

1

Hammarstrom et al.

the following discussion attempts to focus on re-sorption as a dynamic and unified process.

Root resorption, although an e.ssentially patho-logical process, apparently differs little from its os-seous homcostatic counterpart. There are, however,some notable differences between the cells respon-sible for resorption of the different tissues (6). Al-though both are of hematogenous origin, dentin-resorbing cells (Fig. 1) are usually smaller and con-tain fewer nuclei than osteoclasts (7). Furthermore,the well-developed clear zones evident in actively-resorbing osteoclasts contrast with those observed indentin-resorbing cells, which are either very smallor non-existent (6,8). It has been suggested thatthe appearance of resorbing eells is affected by thenature of the tissue being resorbed and that the cellsshould be designated accordingly, as in the termsdentinoclast and osteoclast (6).

During the actual avulsion and replantation pro-cedures, small areas of mechanical damage to thecementum surface are sustained, and these resultin the shallow resorption lacunae observed afterreplantation and termed »surlace resorption«(9,10). Under ideal conditions (that is, where thevitality ol the periodontal membrane has not beencompromised, and the pulp or dentin is not con-taminated by bacteria), rapid periodontal healingand root surface repair occur. Apposition of repara-tive cementum within these resorption lacunae isusually completed within 14 days (11).

The status of the dental pulp is critical to theroot resorption process. The pul|3 invariably loses itsvascular supply following avulsion and, except inthe case of an immature tooth with an open apex,revascularization rarely occurs (12,13). Necrosisgenerally proceeds and the pulp is often infected asa result of contact with saliva or extra-oral debris(1,12). Nevertheless, as long as the eementum cover-ing the root surface remains intaet, the bacteria andproducts of pulp tissue degradation remain reason-ably confined to the root canal. Once the cementumand intermediate cementum are penetrated by thesurface resorption referred to earlier, the dentinaltubules provide a pathway for the passage of bac-teria and their toxic products from the pulpchamber to the root surface. An inflammatory re-sponse is subsequently evoked within the periodon-tal membrane, and root substance and bone aredestroyed. This proce.ss is accelerated in the youngerpatient in whom the dentinal tubules, often sealedwith the progress of years, are still patent (1,14).This sequence of events has been termed inflamma-tory root resorption (15,16) and, if not resolved,can cause rapid destruction of the dental root. If,however, the inflammation subsides, ankylosis oftenresults from the fusion of ingrowing bone to dentinexposed by the resorption process.

Replantatioti ofa tooth with a necrotic periodontalmembrane, in the absence of infection, results in anankylotic fusion between bone and the cementumsurface or shallow resorption lacunae (17). This maydiffer from, or at least be a delayed form of the »re-placement resorption« described by Andreasen(4,18,19), in which ankylosis is subsequent to inflam-matory resorption. The status of the periodontalmembrane is thus critical to the initiation of ankylosis(1,2,18,20,21,22) and this raises the question of howthe progression of ankylosis is influenced by such fac-tors as a necrotic periodontal membrane, or the stateof the dental cementum. No such long-term experi-mental studies have been reported. However, ourpreliminary data indicate that the root resorptionwhich follows an ankylotic fusion between the dentalroot and the alveolar bone progresses more slowly ifthe cementum layer is intact. It may thus prove morefavorable to chemically remove a necrotic and ofteninfected periodontal membrane prior to replantation(e.g. when an avulsed tooth has been stored for toolong in an unsuitable medium) (21).

Recently, experimental studies on formation ofreattachment and new att;ichment iti jjeriodontally-compromiscd teeth have demonstrated the potentialof periodontal membrane cells to proliferate apicallyinto a denuded area of the root, provided the al-veolar bone and pocket epithelium are preventedfrom simultaneous invasion (23,24,25). This con-cept of a competition between the various tissueelements was also investigated by Andreasen (26)who found that periodontal cells proliferated api-cally from the crevicular gingival tissues when theroot surface had been denuded of vital periodontalligament prior to replantation. It was proposed thata competitive situation existed between the down-growth of new periodontal membrane from the cer-vical region, and the ingrowth of the alveolar boneacross the periodontal spaCe. Andreasen postulatedthat if alveolar bone growth across the periodontalspace, and thereby ankylosis, could be prevented, anew periodontal ligament could form as a result ofcontinued downgrowth from the crevicular site.

In conclusion, ankylosis »"esults after replantationof all teeth with necrotic periodontal membranes.Furthermore, if the periodontal membrane is vitalat the time of replantation, but pulpally-derivedinflammatory resorption ensues, ankylosis will resultafter endodontic treatment when the inflammationsubsides. Hence the importance of the status of boththe periodontium and the pulp is emphasized.

Experimental studies: Factors intiuencing the prognosis ofthe replanted tooth

The use of a histomorphometric evaluation tech-nique, pioneered by Andreasen (9,10), has facili-

Tooth replantation

Fig. 1. A dcnli i ioclasl (O) in a shallow resorpt ion l a c u n a from a m o n k e y tooth in a s ia i in iny electron niurosKiij i i p i epa r a l i on . T h e

dent inoe las i ha.s a rulTled bordci ' (a r row) loward.s llic den l ina l suiface. T l ie re is very litlie evidence fbi llie existence o( '»elear /.ones«

or a n y struc tures sealing ofl' the rallied border .

tated experimental studies of tooth replantation andits sequelae. The basic principles of this techniqueare illustrated in Figs. 2 and 3. Examination ofperiodontal membrane repair and reattachment iscommon to all of these studies, each one of whichemphasizes a different variable capable of alteringthe prognosis of the re]3lanted tooth (Fig. 4).

Mechanical damage during exarticulation and replantation

In the processes of avulsion and rcjjlantation, tissuesare torn and cells are damaged. These areas ofdamage api^ear as surface resorption defects which.

if uncomplicated by other factors, heal relativelyquickly. It has been demonstrated that damage tothe root surface is maximal on those surfaces wherephysical contact occurs with the bone socket duringrotatory movement, i.e. the convex buccal and lin-gual surfaces of the root. 1 he proximal concavesurfaces are least damaged during the exarticulation- replantation sequence (10). 'fhus, it is not surpris-ing that resorption sites, after experimental extrac-tion and replantation, arc most commonly observedon the convex surfaces of the root and, less com-monly, on the proximal surfaces which are ustiallyconcave and thereby protected from damage.

Hammarstrom et al.

Fig. 2. The histomorphometric evaluation technique. A predeter-mined number of radii were superimposed over each sectiontaken from a step-serial sectioned tooth. At the intersections ofthe radii and the root surlaee (at 8 points shown in this Figure)the appearance of the periodontium was elassified accordingto defmed criteria (normal periodontium, surface resorption,inflammatory resorption, ete). The percentage area of root sur-face showing a defined criterion was caleulated by dividing theproduct of the number of observation points showing the defmedcriterion X 100, by the total number of observation points.

Storage of the tooth prior to replantation

Although it is most desirable to replant the exartic-ulated tooth as quickly as possible, this may notalways be feasible. In these situations, it is essentialto ensure maximal viability of the periodontal metn-brane attached to the root surface. Accordingly, thetooth must be prevented from drying, and it isimportant that its storage medium is of the correctosmolality and pH (27,28). It has been shown thatafter 60 min of dry storage very few periodontalcells retain their vitality (22,29). Such a situationguarantees the onset of extensive pulpally-derivedinflammatory resorption or of ankylosis and sub-sequent replacement root resorption of endodon-tically treated teeth (1,19,22). Storage in tap wateris equally as damaging as dry storage, the hypotoniceonditions resulting in rapid cell lysis (27). Exper-imentally available media, such as physiological cul-ture media, preserve cell viability well, but these arerarely available at the site of accident (27,28,30).

Saliva allows storage of teeth for about 2 h (31).However, its hypotonicity augers poorly for cell sur-vival and, furthermore, the compromised cells dem-onstrate a lowered resistance lo the bacteria nor-mally found in saliva (22,27,28,32). Recent studieshave established that milk is an excellent storagemedium, and teeth stored for up to 6 h demonstratethe same low index of resorption as teeth replantedimmediately following avulsion (30,31), The pH

and osmolality of milk, being 6.5-6.8 and 230-270mOsm/kg respectively, are compatible with long-term cell survival (28,30,33). Furthermore, pasteur-ized milk contains few virulent baeteria (22,27).Milk products such as sour milk and yoghurt pro-vide poor conditions for cell survival because of theirlow pH (27).

Cell survival can also be encouraged by prevent-ing osmotic damage caused by evaporation. Recentexperiments have demonstrated that teeth wrappedin plastic foil for 1 h have a similary low rate ofresorption as those replanted immediately followingavulsion (34).

The temperature of the storage medium appearsto have little influence on"periodontal healing andvitality of the cells of the periodontal metnbrane, aslong as it is kept below 37°C (27). Accordingly, milktaken directly from the refrigerator may be used asa storage medium.

The use of chemical agents to prevent root-resorption

While it is apparetit from the foregoing that cellsurvival is essential for prevention of the resorptiotiprocess, what can be done if cell damage has alreadyintervened? Many different chemical agents havebeen used in order to produce a root surface that isresistant to resorptioti (1). Treatment with acids,formaliti atid calcium hydroxide has been utisuccess-ful, but the use ofa fluoride solutioti has been re-ported to slow down the resorption process (35-38).Recent studies have investigated the possibility ofrendering the root surface unreactive by decalcifica-tion followed by enzymatic deletion of glyco-proteins, and cross-linkage of cementum collagenusing glutaraldehyde. Initial results hold somepromise for the prevention of resorption (39).

Treatment of the socket

In the past, there was a tetideticy to attribute aninfluence of the socket to the onset and progress ofreplacement resorption. However, results of laterexperiments, in which newly avulsed teeth werereplanted into previously prepared sockets, indi-cated that the main factor determining the onset ofreplacement resorption was the state of the peri-odontal membrane. Curettage of the socket walland presence or removal of a blood elot had littleitifluence on the healing pattem of the replantedtooth (1).

Splinting of the replanted tooth

The role of rigid and semi-rigid fixation in the treat-ment of the replanted tooth has been investigatedand it was concluded that minimal splinting permits

Tooth replantation

T̂ z'fj. J?. Schematic drawing and photomicrc^graphs illustrating the most common periodontal re])air patterns observed during re|)lant-

ation studies.

Hammarstrom et al.

IMMI D I A l I Kl PI \N1 ,\1 K ) \ ' Ih

86%

42%

SAt lVA MILK (ih

21%

79%

Fig. 4. Periodontal healing patterns after variotis extraoral treatments of an avulsed tooth. The drawings summarize results (Voni anumber of studies (17,21,27,30,31,34,41). I'-ndo indicates that the teeth were treated endodontically with gutta percha root fillingsextraorally. The periodontal ccjnditions were evaluated after a healing period of 8 weeks. The figures indicate the relative area (in%) of the root stnlace showing the tiiost common periodontal re])air patterns indicated in Fig. 3.

Tooth replantation

physiological »jiggling« movements of the tootliwhich result in a low incidence of ankylosis (1,9,40).Rigid fixation produced a high degree of bony out-growth across the periodontal space, ankylosis tothe root, and replacetnent resorption (1,9).

Effect of mastication on periodontal repair

Masticatory stimulation has been shown to have apositive eflect in reducitig the extent of ankylosis(41). Monkey teeth were extracted, air dried for 1h, endodontically treated atid replanted, and theanitnals were subsequently placed on either a hardor a soft diet. The hard diet resulted in significandyless ankylosis and a higher incidence of normal peri-odontal ligametit compared with the soft diet.

Endodontic treatment

It has been established that bacteria and breakdownproducts from infected pulp tissue can readily pen-etrate the dentinal tubules. In the absence o( theintermediate cementum layer, these products prod-uce inflammatory changes within the periodontalmembrane leading to inflatnmatory root resorptton(4,5). Rapid and efficient management of the necro-tic pulp is necessary to prevent the onset of inflam-matory root resorption, and debridetnent of theroot-canal within a period of 14 d following replant-ation has been recomtnended (1).

As the primary goal of therapy is to tninimizeperiodontal damage, endodontic treatment shouldnot be carried out on the tooth prior to replantation,as the excessive handlitig risks additional damage tothe membrane (1,4). Similarly, it has been suggestedthat agents such as calciutn hydroxide or root canalsealers should not be placed within the root canalinitially as these have a cytotoxic eflbct which tnayadd to the datnage already sustained by the peri-odontal tnetnbrane (4,42).

The role of antibiotics

Attention has recently been focused upon the use ofantibiotics as an adjunct in the treatment of thereplanted tooth (17). Systemic administration ofthese agents at the time of replantation, and priorto endodontic treatment, has been shown to beeflfective in preventing both bacterial invasion of thenecrotic pulp atid inflamtnatory rcsorption. How-ever, if bacterial invasion of the pulp is allowed toproceed before systemic antibiotic adtnitiistration,this prophylactic measure is rendered itieffectiveand inflammatory t-esorption results. In such a case,intrapulpal application of antibiotics in experimen-tal studies has been shown to eliminate inflammato-ry resorption prior to final endodontic therapy (17).

Conclusions

Successful managemetit of the avulsed tooth shouldaim at the prevetition of both ankylosis and inflam-matory resorption. Cotisequently, the vitality ol theperiodontal membrane must be maintained andbacterial invasion of the pulp prevented. CutTendy,we are aware of the factors responsible for the iti-itiation of the various healing patterns in the peri-odotital tnembrane, but further sttidies are requiredto examine the progression of these patterns utidervarious conditions.

Acknowtedgements Gratits from the Swedish MedicalResearch Council (nos. 06001 & 6651), StockholmsIatis latidsting, Folksatn forskningsfond and SverigesMejeriers Riksforbund have supported the studiesby the authors of this review.

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