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   Journal of the Canadian Dental Association 308  May 2003, Vol. 69, No. 5  C LINICAL P RACTICE  A  vulsions and severe intrusions are associated withpoor post-treatment outcomes. Management of both avulsions and intrusions is controversial: avulsions present the dilemma of whether or not to replant, whereas intrusions have the widest choice of treatmentoptions. Every trauma intervention should be guided by application of the best scientific evidence integrated withthe clinician’s expertise and the values and expectations of patients and their parents. Yet dentists may be “rusty” inboth clinical techniques and application of research-basedinformation, primarily because of the rarity of such events.Clinical guidelines should incorporate the best researchevidence and techniques, as well as the means to explore theexpectations of patients and their parents. This review of recent research and the changing management of avulsionsand intrusions identifies the controversies and clarifies clinical options.  Avulsions Guidelines  Guidelines for replantation have been published by a number of organizations such as the American Associationof Endodontists (AAE), 1 the Royal College of Surgeons of England (RCSE) 2 and the International Association of Dental Traumatology (IADT). 3  Although there are similar-ities among them, it is obvious that personal opinion, anecdotal information and caprice are woven into thesedocuments. 4 For example, the guidelines for the manage-ment of avulsions have not addressed outcomes, the “drivefor normalcy” that produces requests for replantation of teeth for which the prognosis is hopeless, the orthodonticimplications of replantation into mouths with associatedmalocclusions and, finally, the direct and indirect costs of the replantation decision. 1–3 The guidelines just described  Avulsions and Intrusions:The Controversial Displacement Injuries ã David J. Kenny, BSc, DDS, PhD ãã Edward J. Barrett, BSc, DDS, MSc ãã Michael J. Casas, DDS, MSc ã Abstract Avulsions and intrusions are the most complicated and controversial displacement injuries of permanent teeth.Clinical guidelines published by authorities such as the American Association of Endodontists, the Royal College of Surgeons of England and the International Association of Dental Traumatology are inconsistent. While a certainamount of inconsistency might be expected, some of these guidelines recommend treatments that are experimen- tal or have not incorporated research information from the past 5 years, and in one case the guidelines incorrectly describe the nature of Hank’s balanced salt solution. Recent laboratory studies support previous clinical outcome studies in emphasizing that only for teeth replanted within 5 minutes of avulsion is there a chance of regenerationof the periodontal ligament and normal function. Teeth replanted beyond 5 minutes will take another path, that of repair followed by root resorption, ankylosis and eventual extraction. Dentists should explain these outcomes at the time of the replantation decision. Severe intrusions also have predictable outcomes. Teeth intruded beyond 6 mm cannot regenerate a functional periodontal ligament and so are prone to root resorption and eventual extraction as well. In this situation the decision is one of immediate extraction or repositioning, with the understanding that it is inevitable that the tooth will eventually be extracted. Authoritative clinical guidelines available on the Internet provide the clinician with useful outlines for treatment. However, individual inconsistencies stimulate academic controversies and, in some cases, clinical misdirection. MeSH Key Words:  incisor/injuries; root resorption/prevention & control; tooth avulsion/therapy  © J Can Dent Assoc 2003; 69(5):308–13This article has been peer reviewed.  May 2003, Vol. 69, No. 5  309   Journal of the Canadian Dental AssociationAvulsions and Intrusions: The Controversial Displacement Injuries  are “trailing edge” documents that at best provide consen-sus interpretation of research evidence published more than5 years ago. Nevertheless, such guidelines may reduce thenumber of inappropriate or cavalier treatments of trauma. 5 The advent of computer-assisted training packages providesyet another means of disseminating consensus-based treat-ment methods. 6 The AAE, 1 RCSE 2 and IADT 3 guidelinesare also available online. Extra-alveolar Time Despite evidence that immediate replantation (i.e., within5 minutes) is required for regeneration of the periodontalligament (PDL) and its return to normal function, 7 morethan three-quarters of school teachers, coaches and care-givers would be reluctant to replant teeth if the circum-stance arose. 8,9 The reasons for this reluctance reportedly included inadequate training, reluctance to induce pain orfear in the child, personal fear of bloodborne infection,fear of replacing the tooth incorrectly and fear of possiblelegal consequences. 9 Recently, attention has focused on thefact that the avulsed tooth (which is essentially a free graft) isoften exposed to air or held in tissue or cloth (dry storage) while first aid caregivers search for milk. Laboratory studieshave supported earlier clinical studies demonstrating thatafter dry storage for more than 15 minutes, precursor cellson the root-side PDL are unable to reproduce and differ-entiate into fibroblasts. Several authors have shown that with 30 minutes of dry storage, virtually all root-side PDLcells have died. 10–14  Why is it, then, that teeth replanted many hours afteravulsion remain in the mouth, often “look good” and arefunctional? In these cases of delayed replantation, healing occurs by repair rather than by regeneration. Root-sidePDL cells that are immediately stored in appropriate media can retain their vitality for extended periods, butbecome disabled. They lose their ability to become fibrob-lasts and to perform the normal functions of PDL cells.Consequently, healing is by repair and little or no PDL isregenerated. In addition, PDL cells on the alveolar side areaffected by damage associated with physical tearing of theligament and loss of the tooth, so they too have limitedability to contribute to the regeneration of new PDL. Storage Media and Root Treatments For the past decade, laboratory studies of PDL cell vitality have focused on a search for the Holy Grail of storage media, often without consideration of issues of practicality or the blood, tears and confusion that takeplace when a person is injured by a fall, collision or othermisadventure. If the tooth is transferred to a liquid mediumsuch as the patient’s own saliva, milk or saline within thefirst 15 minutes, some of the cells in the PDL and cementum will survive and may play a role in regeneration.Inevitably, however, storage in a liquid medium beforereplantation results in ankylosis, root resorption and even-tual extraction. 15 The patient’s own saliva, which is alwaysavailable, is preferable to desiccation and can be an effectivestorage medium for up to 30 minutes. 11 If the tooth istransferred to a liquid medium beyond 15 minutes of desic-cation, the surviving cells will be increasingly limited inboth number and function. 13 Cool milk will maintain theability of PDL precursor cells to reproduce for almost twiceas long as milk that is allowed to warm to room tempera-ture. 11 Clearly, milk packed in ice should be considered theprimary extended-time storage medium for avulsed teethintended for delayed replantation, and ice is almost alwaysavailable where cold milk is found. Guidelines for thechoice of storage media and prereplantation “treatment” of avulsed teeth suggest exotic solutions and treatments for which there is limited scientific evidence. Few dental prac-tices stock saline, still fewer have Hank’s balanced salt solution, and virtually none have ViaSpan (DuPontPharmaceuticals Co., Wilmington, Del.), a tissue culturemedium.For teeth that have undergone an extended extra-alveolar period, most guidelines advocate prereplantation“treatment” of the root surface with fluoride. 1–3 Thisrecommendation is based on a limited number of animalstudies and a single case report and is directed towardincreasing the resistance of the root to replacement resorp-tion through the formation of fluorapatite on the rootsurface. 16–18 This treatment has never been tested in a human outcome study, and its clinical utility remainsunknown, yet it appears in all 3 guidelines. 1–3  Anothertreatment that is still advocated on the home page of the AAE Web site 1 and subsequently disproved involved placing teeth with prolonged extra-alveolar time in Hank’sbalanced salt solution, a balanced isotonic salt solution,before replantation, with the intent of reconstituting depleted cellular metabolites. 19 Subsequent in vitro experi-ments have proven (not surprisingly) that root-side cellsthat are already dead cannot be resurrected by rehydrating them in media such as Hank’s balanced salt solution. 20 Some reputable animal studies (in dogs and monkeys) havesupported the use of topical doxycycline “treatment” of teeth before replantation. 21,22 However, topical applicationis mentioned in one set of guidelines 2 and systemic treat-ment in another. 3 Furthermore, there are no humanoutcome studies to support the recommendation of doxy-cycline treatment for trauma. These treatments, which areonly marginally supported by scientific research, are contro-versial and needlessly complicate clinical management. Root Resorption  Obtaining a precise and accurate post-trauma, prere-plantation history is paramount, as postreplantationoutcomes are directly related to extra-alveolar time. 7,14 Careful history-taking may reveal, for example, that a tooth   Journal of the Canadian Dental Association 310  May 2003, Vol. 69, No. 5 Kenny, Barrett, Casas  that has arrived in milk was desiccated in a paper napkin for15 minutes while someone went for the milk. The clinicianshould strive for a replanted tooth that is free of infectionby early removal of the necrotic pulp and timely completionof endodontic treatment. Elimination of infection andprevention of pulp necrosis represent the best means of preventing inflammatory root resorption ( Fig.1 ).Replacement resorption and ankylosis may be consideredacceptable outcomes, as replanted teeth can survive for a number of years. If, in addition, the patient has achievedphysical maturity, infraocclusion and gingival irregularity dueto surrounding alveolar growth ( Fig.2 ) will be minimal. Almost all replanted teeth exhibit replacement resorption andankylosis, as immediate replantation is achieved only rarely.Replacement resorption leads to fusion of the tooth root with the adjacent alveolar bone ( Fig.3 ). In older childrenand adults this process produces bony replacement of rootcementum and dentin, followed by loss of the crown eitherspontaneously or by surgical intervention. In children whohave not achieved skeletal maturity, replacement resorptionleads to progressive infraocclusion during the adolescentgrowth spurt. Adolescents and parents often do not want tohave these incisor(s) extracted, yet the alveolar and gingivalarchitecture becomes increasingly distorted with growth.Thus, the decision to replant a permanent tooth initiatesa number of sequelae, including some that affect socio-economic aspects of family life. 23,24 Evidence that regeneration of a normal PDL is notexpected beyond 5 minutes of extra-alveolar dry storage hasproduced a paradigm shift in understanding the outcomesof replantation. Avulsed teeth fall into 1 of 2 categories: less than 5 minutes of extra-alveolar dry storage, where thelikelihood of regeneration of a functional PDL is maxi-mized, 7,25 and beyond 5 minutes of dry storage, where healing is by repair and tooth loss is inevitable (althoughsurvival may be prolonged if the patient is a young adult). 25 Tooth Survival   A previous study  26 produced survival curves illustrating tooth survival after replantation in a population of adoles-cents ( Fig. 4 ). Use of this information in conjunction witha thorough discussion of the financial, temporal andemotional costs of replantation will help clinicians, parentsand patients arrive at a rational treatment plan. Bioactive Substances  Investigators are now working with an enamel matrixderivative, Emdogain (Biora AB, Malmo, Sweden), designed Figure 1: Two replanted central incisors affected by inflam- matory root resorption. The process, characterized by bowl- shaped radiolucent areas, is initiated by infected dental pulp. Figure 2: Infraocclusion of tooth 21following replantation more than 3 hours after the initial trauma. Infraocclusionoccurs when replacement root resorption(ankylosis) affects the teeth of young people with incomplete skeletal growth. Fusionbetween the teeth and the alveolus prevents the affected teeth from drifting with growthof the maxilla and thus distorts gingival architecture. Figure 3: Radiograph of acentral incisor affected by replacement root resorption.In the absence of infection, the process is progressive and results in eventual loss of the tooth. Figure 4: Survival rates after replantation.If a patient presents with anavulsed permanent incisor that has been stored dry for 60 minutes,the 5-year survival for the tooth is estimated at 0.56. This means that if the replanted tooth is retained for 5 years, there is a probability of 0.56 that the tooth will be retained beyond that point. It does not mean that there is a 56% chance the tooth will be retained for 5 years. 29   May 2003, Vol. 69, No. 5  311  Journal of the Canadian Dental AssociationAvulsions and Intrusions: The Controversial Displacement Injuries  to facilitate PDL regeneration and thus inhibit replacementresorption. One group is involved in a prospective outcomecase series, 27  while others have undertaken animal studies 28 and described unconventional applications. 29 It is speculatedthat a differentiation factor such as Emdogain couldpromote migration, proliferation and differentiationof PDL fibroblasts 30  within the adjacent alveolus torepopulate the PDL. 31 There are no published outcome data forEmdogain in the acute management of avulsedteeth. Nevertheless, this material is mentioned inthe IADT guidelines 3 as a treatment for replanta-tion. Although the performance of Emdogain onreplanted permanent incisors is as yet unknown, theuse of such bioactive substances marks the begin-ning of the use of pharmacotherapeutics in dentaltrauma management. Intrusions Guidelines  Clinicians have noted discrepancies in the recom-mendations of Andreasen and Andreasen, 32 theRCSE, 2 and Andreasen and others. 33 Even theterminology used to describe the treatment of intru-sions and subsequent outcomes lacks precision andconsistency. The term spontaneous eruption  gives a falsely optimistic impression, as tooth movementafter injury is both unpredictable and pathologicalrather than developmental, as it would be in normaleruption. Another imprecise term is orthodontic repositioning  . The traction forces used to moveintruded incisors exceed those of conventionalorthodontic treatment, and severely intruded teethdo not have a functional PDL, a prerequisite fororthodontic movement ( Figs. 5a  , 5b ). These termsimply that an intruded tooth will return to its src-inal location with time or that it can be moved thereby the same mechanics and with the samepredictability as conventional orthodontic treatment,neither of which is necessarily true. Current manage-ment strategies include surgical reduction (immediaterepositioning), repositioning with traction (activerepositioning) and waiting for the tooth to return toits preinjury position (passive repositioning).  Amount of Intrusion as Most Critical Factor   Along with avulsions, intrusions are the othermost complicated and controversial luxationinjuries. A severe intrusion produces catastrophicinjury to the alveolar bone, shears and destroysPDL cells and the ligament itself, and crushes theapical vascular system. Previously it was thoughtthat the stage of root development was the deter-mining factor for the outcome of intruded teeth. 32 Now it appears that the amount of intrusion is the criticaldeterminant of pulp and tooth survival. Some studies haveshown that intrusions of up to 3 mm have an excellent prog-nosis, whereas the prognosis of incisors with severe (> 6 mm) Figure 5a: Clinical appearance after severe (> 6 mm) intrusion of tooth 22 in a 12-year- old girl. The tooth was surgically repositioned and splinted, and endodontic treatment was completed at the time of initial presentation. Figure 5b: Radiographic appear- ance after severe intrusion of tooth 22 in the same patient. Figure 6a:  Clinical appearance of tooth 21intruded 4 mm at the time of initial presentation. A tooth with this muchintrusion will not predictably repositionwithout traction. Figure 6b:  Radiographic appear- ance of intruded tooth 21 inthe same patient, also at the time of initial presentation. Figure 6c: The appliance employed for active repositioning of intruded tooth 21 inthe same patient. Treatment was initiated at the time of initial presentation, and repositioning was accomplished over aperiod of 6 weeks. Restoration of the crownfracture was completed 7 days after the initiation of treatment. Figure 6d:  Final radiographic appearance of the tooth after 6 weeks of treatment.
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