Dento-alveolar trauma includes injuries caused by an external impact to the dentition and its surrounding structures. These injuries range from a simple contusion of the tooth to total dislocation of the tooth from the alveolar bone, termed tooth avulsion. A significant amount of force is usually necessary for the avulsion of a tooth. Other injuries to the surrounding structures such as alveolar bone fractures and gingival tissue contusions should be suspected.
Falls, especially in younger patients with poor balance, cycling, full-contact sports, traffic accidents, and assaults, are the most common causes of dento-alveolar trauma. In a systematic review published in 2015, the most common places for dental trauma to occur were found to be home, school, and then the street. Anatomic/physiologic features associated with dentoalveolar trauma include protuberant upper teeth, overjet (over 3mm), anterior open bite, malocclusion (Class II), incompetent lips, and mouth breathing.
The peak incidence of dental trauma occurs in the 7-11-year age group, with a male to female ratio of 2:1. Permanent teeth are injured more than temporary (60% vs. 40%, respectively). A study of 800 children 11-13 years of age found that the prevalence of existing dental trauma in permanent anterior teeth was 52%, with approximately 10% of respondents not remembering a history of trauma. In a study conducted on 1298 trauma patients that received treatment in an emergency room, 24% included dental injuries, of which two-thirds were tooth avulsions. Falls are the most common cause, with cycling accidents second, and then full-contact sports and assaults following. Bemelmans reported that at least 32% of athletes involved in full-contact sports had experienced some form of injury to their dentition. The most high-risk sports for dental injury are ice hockey, football, lacrosse, rugby, martial arts, and skating. Helmets have not decreased the incidence of dental trauma, but mouth guards have. Dental trauma in younger children should always raise the suspicion of abuse.
Dento-alveolar trauma can be broken down based on injuries to the tooth itself and those to the surrounding periodontium, which includes the periodontal ligament, the alveolar bone, and the gingival tissue. Dental injuries are classified as fractures to the cementum, the enamel, the dentine, and the root. Pulp exposure may be a component of enamel-dentine fracture. Injuries to the tooth include subluxation (loose tooth), luxation (displaced tooth), or avulsion (knocked out). The periodontal ligament (PDL) is the soft tissue connecting the cementum that covers the roots of the teeth to the surrounding alveolar bone. When an external impact occurs on a tooth, the fibers of the periodontal ligament can tear, allowing partial or total displacement of the tooth from the socket. The ensuing damage can lead to neuro-vascular disruption, as well as pulp necrosis.The maxillary central incisors are the most commonly affected teeth, with the maxillary lateral incisors second. Often, more than one tooth is avulsed. Periodontal ligament fibers can desiccate rapidly in the open air. Even in a tooth that is replanted, the damaged periodontal ligament fibers can lead to bony resorption of the root. Root resorption will lead to crown fracture and loss of the tooth. 
Maintaining the viability of the periodontal fibers after avulsion is integral to the long-term prognosis. Immediate replantation will allow the PDL to reform the connections within the socket (alveolus) to the cementum. The current consensus is that time elapsed between avulsion and reimplantation is the most critical factor for survival. Ninety minutes seems to be the upper limit consistent with long term survival of the tooth.
A history of trauma to the tooth will reveal tooth avulsion, and the mechanism of injury can point to other injuries. History should include the length of time since tooth avulsion, the storage medium in which the tooth had been placed, and if the tooth is primary or permanent. By 14 years of age, a patient's primary teeth should all be replaced by permanent teeth. Physical examination involves the assessment of the tooth socket for foreign material, tooth fragments, and lacerations as these can prevent tooth replantation. Evaluation of the surrounding structures for other injuries such as lacerations, gingival contusions, and maxillary or mandibular fractures is also necessary. If a tooth suspected of avulsion is not found, aspiration, gastro-intestinal placement, or intrusion should be ruled out.
Imaging modalities, including extra and intraoral radiographs and CT scans, can aid in evaluation for dental, alveolar, and surrounding fractures. Imaging is useful in identifying intrusion of the 'missing' tooth.
Most often, tooth avulsions occur outside of treatment facilities. Avulsed teeth should be handled by the crown to prevent damage to the root surface and PDL fibers. Reimplantation immediately at the scene carries the best survival. However, few parents, coaches, or by-standers are likely to know this. Studies have shown that if a tooth cannot be replanted within in five minutes, it should be placed in a storage media such as a balanced salt solution or milk, or in the patient's mouth. Milk has the advantage of ready availability, appropriate pH, normal osmolarity, an abundance of nutrients, and growth factors. Appropriate storage media can increase the time of viability of an avulsed tooth. Water alone can damage the PDL due to its low osmolality. Before replantation at the dentist's or orthodontist, the socket and tooth should be lightly irrigated with normal saline to clean the structures, and the socket may be aspirated gently if a blood clot is obstructing it. The tooth should be aligned anatomically, and firm pressure applied to the socket to replant the tooth. Most teeth can be successfully replanted if the extraoral dry time is less than 30 minutes; after this period, the survival probability of the tooth diminishes. Storage media can increase the viability time of the PDL fibers. If the extraoral dry time is more than 90 minutes, soaking the tooth in agents such as fluoride or thymosal alpha 1 may decrease resorption rates. Immature teeth where the root has not yet wholly formed have a greater chance of revascularization after soaking in doxycycline. Primary teeth should not undergo replantation as this can damage the underlying permanent tooth germ. Splinting with bonding resins, thin steel wires, and sutures may be needed. Splinting for two weeks is indicated for securing the tooth in place once replanted. Accompanying fractures of the tooth or alveolus increases the splinting time to 6-8 weeks and require rigid splints. Semi-rigid splints seem to have the greatest success. Splinting immobilizes the replanted tooth and allows the damaged periodontal ligament fibers to reestablish connection from the alveolus to the cementum. In cases where the dry time was more than 60 minutes, and there was no use of any storage media, removal of the remaining PDL should be undertaken as it will become a stimulus for continued inflammation that accelerates infection-related resorption and ankylosis. The remaining PDL can be removed by multiple methods that include gentle scaling and root planning, soft pumice prophylaxis, gauze, or soaking the tooth in 3% citric acid for 3 minutes. The fluoride treatment must follow this process as it slows down the process of ankylosis and reduces the risk of resorption. Severe damage to the neurovascular bundle and the periodontal ligament can lead to replacement root resorption or inflammatory resorption. These complications can be anticipated and possibly prevented with disinfectants at the time of reimplantation, as well as systemic antibiotics. Resorption complications may need ultimate root canal procedures. 
Differential diagnosis of tooth avulsion includes complete intrusion of the tooth into the alveolar bone, subluxation, or lateral luxation. A 'missing tooth' needs to have intrusion, swallowing, or aspiration ruled out. These conditions can be distinguished by history and physical as well as by imaging modalities.
In a study published by Karayilmaz et al., they examined the long-term prognosis of avulsed teeth and concluded that the reimplantation of avulsed teeth is a highly successful procedure. The long and short term prognosis is strongly affected by the dry time. However, in another study, the long term survival of replanted avulsed teeth was only approximately 20%, and this was attributed to the actual failure of adequate follow-up treatment.
The major complications secondary to reimplantation of avulsed teeth include infections, tooth discolorations, fistulas, inflammatory root resorption, ankylosis of the root to the alveolus, apical periodontitis, pulp canal obliteration (PCO), and pulp necrosis (ultimately leading to tooth loss).[iv]Resorption and ankylosis are associated more with the use of rigid splints as opposed to semi-rigid. This condition can be problematic if the patient is growing as the surrounding structures will continue to develop, and the tooth will look submerged. Second, loss of vitality, as the severing of blood vessels occurs when the tooth is avulsed, so there is a high risk of loss of vitality, especially if the apex has completely developed. This may eventuate in pulp necrosis and inflammatory resorption of the root. If this goes unrecognized, periapical periodontitis may develop and can complicate the healing process and prognoses. PCO is apparent weeks to months after reimplantation and is heralded by radiographic density in the crown pulp cavity and along the root pulp cavities. Although it is thought to be a concomitant of healthy revascularization of the injured neurovascular bundles, approximately 15-25% of teeth with PCO go on to have pulp necrosis. 
Coaches, recreational leaders, and first responders should all know the initial management of an avulsed tooth. Patient and parental education and the early seeking of medical care can improve the prognosis and success of treatment. Using the right protective mouthguards in high-risk contact sports can reduce the incidence of potential injury.
Tetanus immunization should be updated if necessary, after tooth avulsion. Dental follow-up is mandatory for further treatment after replantation. Brushing teeth after every meal and using chlorhexidine 0.12% rinse twice daily can decrease infection rates. Antibiotics are prescribed to prevent infection. Patients should be placed on a soft to chew diet for at least two weeks following tooth avulsion. The success of replantation of the tooth is difficult to predict, and the patient\family should be warned that dental root resorption and tooth loss are possible.
The need for early reimplantation and the appropriate storage medium is an essential factor that is less recognized by the patients, parents, and medical professionals. It is necessary for primary care providers, nurse practitioners, and the general dentist to educate the public regarding the prognosis and success of reimplantation, how early treatment is essential, and the preferred storage medium is a balanced salt solution or milk.
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