Relative indications for removal of a tooth from the fracture line:

1. Functionless tooth which would eventuallybe removed.

2. Advanced caries.

3. Advanced periodontal disease.

4. Doubtful teeth which could be added to existing dentures.

5. Teeth involved in untreated fractures pre senting more than 3 days after injury. It is desirable that all teeth not covered by these conditions should be retained.

Management of teeth retained in fracture line:

1. Good-quality intra-oral periapical radiograph.

2. Institution of appropriate systemic antibiotic therapy.

3. Splinting of tooth if mobile.

4. Endodontic therapy if pulp is exposed.

5. Immediate extraction if fracture becomes infected/

6. Follow-up for 1 year and endodontic therapy if there is demonstrable loss of vitality.

Immobilization

Following accurate reduction of the fragments, the fracture site must be immobilized to allow bone healing to occur. Orthopaedic surgeons have been concerned for some time with the process of fracture healing when either rigid or sernirigid fixation is employed. The speed of repair of the weight-bearing skeleton is of paramount importance in the eventual rehabilitation of an injured patient. When semi-rigid fixation is used a fracture heals by secondary intention, which involves the formation and subsequent organization of callus. This is a relatively slow process and weight-bearing must be delayed until full bone replacement has occurred. Even apparently rigid fixation by means of non-compression plating or pinning leaves a gap between the bone ends and bony union requires organization of a primary callus. Key (1932) noted that healing of the arthrodesed knee was accelerated when the opposing bony surfaces were compressed. Later experimental work (Perren at al., 1969) has confirmed that compression osteosynthesis of both experimental osteotomies and clinical fractures results in primary bone healing without the formation of intermediate callus. This results in more rapid stabilization of the fracture site and much earlier restoration of the mechanical strength of the bone. Reitzik and Schoorl (1983) compared non-compression screw and plate osteosynthesis and wired osteosynthesis on either side of the same mandible. Although non-compression plated osteotomies resulted in gap healing with the formation of a small amount of intermediate callus, this was still superior to the less rigid wired osteosynthesis with demonstrably increased mechanical strength on the plated side 6 weeks after surgery. The question arises as to how relevant are these findings to the treatment of mandibular fractures. Unlike a weight-bearing bone, it is only necessary to immobilize the mandible until a stable relationship between the fragments has been achieved. This period is considerably less than would be required for full bony consolidation to take place. Some simple mandibular fractures need no immobilization at all, particularly if a lack of teeth means that precise restoration of the occlusion is not at a premium. Such fractures remain mobile for some time if they are forcibly manipulated but eventually proceed to full bony union. It is indeed difficult to prevent the fractured mandible uniting, and malunion is a more frequent complication than non-union.

Infection of a fracture line prior to definitive treatment has traditionally been regarded as a contraindication to any form of direct skeletal fixation. Indeed at one time it was considered inadvisable to insert a transosseous wire if the fracture was compound into the mouth, because of the risk of subsequent infection. However, with the routine employment of prophylactic antibiotic cover, this risk is very considerably reduced. James et al. (1981), in a prospective study of 422 mandibular fractures, concluded that the postoperative infection rate of the fracture line was no different whether closed or open techniques were employed. Awty and Banks (1971) and Banks (1985) showed that trans-osseous wiring could be regularly and safely employed in heavily contaminated gunshot wounds. There is some evidence that rigid fixation of previously infected fractures by plates produces better results in terms of uncompli­cated healing than traditional methods (Kai Tu and Tenbulzen, 1985).

The overwhelming advantage of plating techniques is that they are all sufficiently rigid to obviate the need for intermaxillary fixation. However, in view of the fact that clinical union of mandibular fractures is much quicker than most other bones, compression osteosynthesis must have a very dubious place in any treatment plan.

Period of immobilization

Whenever IMF is used as the main or adjunctive means of immobilizing a fractured mandible, the clinician needs some guide to the length of time it must be kept in place. The period of stable fixation required to ensure full restoration of function varies according to the site of fracture, the presence or otherwise of retained teeth in the line of fracture, the age of the patient and the presence or absence of infection. Juniper and Awty (1973) have shown that in favourable circumstances stable clinical union can on average regularly be achieved after 3 weeks, at which time fixation can be released.

In fractures of the body of the mandible the blood supply to the fracture site is important to the healing process. Where endosteal vascu-larity is relatively poor, as in the ageing jaw, and particularly in the symphysis region, healing tends to be prolonged. In contrast, the rich blood supply and exuberant osteoblastic activity of the child's growing mandible ensures extremely rapid union.

A simple guide to the time of immobilization for fractures of the tooth-bearing area of the lower jaw is as follows (3 weeks):

1. Tooth retained in fracture line: add 1 week.

2. Fracture at the symphysis: add 1 week.

3. Age 40 years and over: add 1 or 2 weeks.

4. Children and adolescents: subtract 1 week.

Applying this guide it follows that a fracture of the symphysis in a 40-year-old patient where the tooth in the fracture line is retained requires 6 weeks of immobilization (basic 3 weeks + 1 week for less favourable site + 1 week allowed for age + 1 week for tooth retained in the line of fracture).

Rules such as these are designed for guidance only, and it must be emphasized that the frac­ture must always be tested clinically before the mandible is finally released. The temporary attachments to the dentition should be retained for a further period so that re-immobilization can be carried out if the union of the fracture is found to be inadequate after function has been restored.

The methods of immobilization can be summarized as follows:

1.Osteosynthesis without intermaxillary fixation:

a)non-compression small plates;

b) compression plates;

c)miniplates;

d) lag screws;

e)resorbable plates and screws.

2. Intermaxillary fixation:

a)bonded brackets;

b) dental wiring: direct, eyelet;

c) arch bars;

d) cap splints.

3. Intermaxillary fixation with osteosynthesis:

a)transosseous wiring;

b) circumferential wiring;

c)external pin fixation;

d) bone clamps;

e)transfixation with Kirschner wires.