Fractures of the tooth-bearing section of the mandible

Reduction of a fracture means the restoration of a functional alignment of the bone fragments. In certain situations, for example a fracture of the clavicle, this does not necessarily imply exact anatomical alignment. However, in the dentate mandible reduction must be anatomically precise when teeth, which were previously in good occlusion, are involved. Less precise reduction may be acceptable if part of the body of the mandible is edentulous or there are no opposing teeth.

The presence of teeth provides an accurate guide in most cases by which the related bony fragments can be aligned. The teeth are used to assist the reduction, check alignment of the fragments and assist in the immobilization.

Whenever the occlusion is used as an index of accurate reduction it is important to recognize any pre-existing occlusal abnormalities such as an anterior or lateral open bite. Wear facets on individual teeth can provide valuable clues to previous contact areas. Teeth may on occasions be brought into contact during reduction and yet be occluding incorrectly owing to lingual inclination of the fracture segment.

Widely displaced, multiple or extensively comminuted fractures may be impossible to reduce by means of manipulation of the teeth alone, in which case open operative exploration becomes necessary.

In general, reduction and later immobilization is best effected under general anaesthetic, but occasionally it is possible to employ local analgesia supplemented if necessary by sedation. If there is minimal displacement the reduction can sometimes be effected without an anaesthetic.

If the patient's general medical condition precludes the administration of a general anaesthetic, gradual reduction of fractures can sometimes be carried out by elastic traction. Small elastic bands are applied to cap splints or wires fitted to teeth on the individual mandibular fragments and attached in turn to the intact maxilla. More often nowadays, modified orthodontic brackets are cemented to selected teeth to which elastic bands can in turn be attached. A satisfactory temporary reduction can usually be achieved pending an improvement in the patient's general condition.

Teeth in the fracture line are a potential impediment to healing for the following reasons:

1. The fracture is compound into the mouth via the opened periodontal membrane.

2. The tooth may be damaged structurally or lose its blood supply as a result of the trauma so that the pulp subsequently becomes necrotic.

3. The tooth may be affected by some preexisting pathological process, such as anapical granuloma.

       The fracture line can become infected as a result of any of the above - either from the oral cavity via the disrupted periodontium or directly from an infected pulp or apical granuloma. Infection of the fracture line will result in greatly protracted healing of the fracture or even nonunion.

For these reasons in pre-antibiotic days all teeth in the line of the fracture were extracted. This practice was, however, continued into the antibiotic era with unnecessary detriment to the patient. A tooth in the line of fracture which is structurally undamaged, potentially functional, and not subluxed should be retained and antibiotics administered. Its retention will tend to delay clinical union of the fracture by a short period, but this is acceptable in order to preserve the integrity of the dentition. Obviously teeth in an intact dentition are more important than those in a partially edentulous jaw.

Without antibiotic therapy teeth in the line of fracture constitute a real risk of infection. As recently as 1978 Neal and co-workers reported a complication rate of 30 per cent in a retrospeсtive study of 207 mandibular fractures, where the average delay in treatment was 3-4 days, and the patients were generally from deprived social backgrounds and uncooperative (Neal et al., 1978). Thirty-six infections of the fracture site occurred, the incidence interestingly being unrelated to whether the involved tooth was removed at the time of treatment or after the complications had ensued. The subsequent literature supports the observation that infection is almost invariably associated with teeth in the fracture line but the incidence is not affected by early removal (Anderson and Alpert 1992; Ellis and Sinn 1993).

In general the infection rate of mandibular fractures which involve teeth is much lower -around 5 per cent (James et al., 1981). Kahnberg (1979) and Kahnberg and Ridell (1979), in a study of 185 teeth involved in the line of mandibular fractures, have shown that the pro­gnosis of the teeth they elected to conserve was good. Complete clinical and radiographic recovery was found in 59 per cent, a figure similar to other studies. Careful follow-up of the retained teeth was necessary so that endodontic therapy could be instituted as soon as there were clinical indications. In Kahnberg and Ridell's study 32 of the 185 involved teeth were extracted, 20 of which became necessary after initial fixation of the fracture because of loosening of the teeth or infection of the fracture site. Kamboozia and Punnia-Moorthy (1993) found that there were significantly more devitalized teeth in the line of mandibular fractures treated by plated osteosynthesis.

Fractures at the angle of the mandible with teeth in the fracture line are more likely to become infected than at other sites (Ellis, 1999). Considerable controversy therefore exists with regard to functionless third molars involved in mandibular fractures. These teeth are a potential source of infection and, if left, will eventually need to be removed. They have little value in stabilizing the fracture which, if undisplaced, is retained in line by the attached periosteum. Furthermore, such a tooth will never be easier to remove, because the fracture effectively disimpacts it and as a result it can be elevated with minimal disturbance of bone and periosteum. On balance it would seem more sensible to remove a func­tionless, potentially troublesome tooth when an operative intervention has become necessary by virtue of the fracture.

Summary

Absolute indications for removal of a tooth from a mandibular fracture line:

1. Longitudinal fracture involving the root.

2. Dislocation or subluxation of the tooth from its socket.

3. Presence of periapical infection.

4. Infected fracture line.

5. Acute pericoronitis.