Injuries to the primary dentition

Seventy per cent of injuries to the primary dentition involve the maxillary central incisors (Galea, 1984). Intrusion and lateral luxation are the commonest injury (Mackie and Warren, 1988) with avulsion occurring in approximately 10 per cent of cases (Fountain and Camp, 1991). Generally speaking fractured, extruded or grossly displaced teeth should be extracted. Less displaced teeth that do not cause occlusal interference can be left and monitored. Damage to the underlying developing permanent tooth by displaced teeth is a recognized problem, particularly with intrusion injuries. This has been shown to occur in 25-70 per cent of cases (Von Arx, 1997). Intruded primary teeth will normally erupt spontaneously and extraction simply increases the risk of further damage to underlying teeth.

Injuries affecting the permanent dentition

Injuries to the dental hard tissue

Crown fracture

A simple fracture of only the enamel does not require emergency treatment but exposure of the underlying dentine should be covered as soon as possible, particularly in young people where bacterial penetration of the open dentinal tubules can be rapid (Lundy and Stanley, 1969). Protection with a calcium hydroxide cement held in place with a temporary acid-etch composite dressing is ideal until a definitive restora­tion can be undertaken. Providing it is large enough, consideration can be given to restoring the fractured crown by cementing the fragment with composite resin. Pulp testing immediately after injury is of no clinical value, but the tooth must be carefully followed up and root-treated later if necessary.

If the pulp is exposed it is not only exquisitely painful to touch and thermal stimuli but will also eventually necrose. Small exposures treated early can be managed as above and monitored, but larger exposures or delays in treatment will require a minimal pulpolomy and calcium hydroxide dressing if the apex is still open, or pulp extirpation if the apex is closed.

Root fracture

An oblique fracture of the crown may extend subgingivally (crown-root fracture). In this situation a decision has to be taken about the possibility of saving the tooth following the same emergency methods described above. If the fracture extends a considerable way down the root, or if there is a vertical split, extraction is inevitable.

Transverse fractures of the root usually affect the incisor teeth and the prognosis depends to a large extent on the level of fracture. A calcified or fibrous bridge occasionally results in 'healing' of the root, particularly if the fracture is in the apical third, but fractures that lie near the gingival level have a poorer prognosis. If the tooth is to be conserved it should be held in a rigid splint for at least 8 weeks. The teeth can be immobilized by bonding to adjacent teeth with acid-etch composite, or a wire and acid-etch composite splint can be applied.

Pulp necrosis, root resorption and obliteration of the pulp canal are common consequences of root fracture, occurring in up to 60 per cent of cases (Andreasen and Andreasen, 1988).

In fractures that lie close to the gingival margin the tooth can still be restored. The loose coronal fragment should be removed and the root devitalized. Following endodontic treatment the root can be orthodontically extruded or a crown-lengthening procedure carried out according to circumstances. This will allow a definitive restoration with a post crown (Heithersay, 1973).

Injuries to the periodontal tissues

Luxation

Pulpal haemorrhage can occur following simple concussion of a tooth and any loosening or displacement carries a high risk of subsequent pulp necrosis, particularly following intrusion injuries. As with root fractures additional late complications include root resorption, pulp canal obliteration, ankylosis and loss of marginal bone support.

Teeth that have been loosened, laterally luxated, or extruded should be manipulated back into position and splinted for 7-21 days. The older methods of fixation such as temporary foil splints or cast cap splints have been replaced by acid-etch composite techniques in which a piece of heavy wire or light arch bar is bonded to the damaged tooth and adjacent sound teeth. Lighter or flexible orthodontic wire, or even a length of heavy nylon suture, can be used if a semirigid splint is needed.

Soft stainless-steel wire can be used to construct a splint without the help of composite material. A loop of wire is passed around a group of teeth, incorporating one or two teeth either side of the subluxed teeth. Individual tie wires are then passed interdentally and tightened to take up the slack in the loop and immobilize the loose teeth.

Simple splints for subluxed teeth or alveolar fractures can be rapidly constructed from vacuum-formed plastic (extruded butyrate sheet, May & Baker Ltd.). An impression is taken following repositioning of the tooth or alveolar fragment. If necessary the affected teeth are relieved on the model, and the thin plastic veneer vacuum-formed on the press in the laboratory. The splint is ussually fixed with a zinc oxide-based cement or self-cure acrylic resin, although individually chipped or fractured teeth should be covered with calcium hydroxide as described above. The whole procedure can be completed on an outpatient basis within 1 hour if the laboratory is on site, and with a minimum of discomfort to the patient. A criticism of this type of splint, as well as for interdental wiring techniques, is that oral hygiene may be compromised leading to gingival inflammation and interference with healing of the traumatized tissues.

Avulsion

A number of factors will influence the chance of success following replantation of an avulsed tooth. These include the stage of root development, the length of time the tooth is allowed to dry, the length of wet storage and the medium used, and correct handling and splinting (Andreasen et al., 1995). Immediate replacement is still the ideal treatment. The root should not be handled, to avoid damage to the periodontal ligament cells, but this is a counsel of perfection in the acute situation where the tooth may have to be retrieved from a playground or sports field! Debris should be removed by gentle rinsing for a few seconds under running cold water. Once the tooth is replaced the patient should bite gently on a handkerchief or gauze and an emergency appointment should be made with a dental surgeon for semi-rigid splinting.

If the tooth cannot be replanted immediately it is important to ensure that the cells of the periodontal ligament do not dry out. Survival out of the mouth is possibLe Fort up to 30 minutes but few cells will retain any vitality after 60 minutes. Blomhof (1981) has shown that periodontal cells will retain their vitality for 2 hours in the patient's saliva and 6 hours in fresh milk. Water is a harmful storage medium due to osmotic lysis of the cells. As soon as possible the socket should be irrigated with warm saline to clear any clot or debris. Curettage of the socket should be avoided because it is associated with increased resorption. The tooth is held by the crown and the root gently irrigated to wash off the storage medium. It is then firmly replanted in the socket. The alveolus should be compressed to reduce any fracture of the socket wall. A semi-rigid splint is applied for 7-14 days and a course of antibiotics prescribed. Even if the eventual outlook is poor it is still worth attempting to save a tooth in the short term since this will help alveolar healing and will retain alveolar bone in the area, an important factor if an implant is to be considered at a later date.