Dentofacial and craniofacial anomalies
Abnormalities of the jaws, face and cranium may be the consequence of faulty development or acquired as a consequence of trauma, tumour, fibrous dysplasia or surgery for neoplastic disease. Dentofacial clefting is the most common of the congenital anomalies but hundreds of others are recognised. Dentofacial and craniofacial anomalies frequently require combined orthodontic and surgical management for their correction.
The embryology of the face has been studied in detail and has provided insight into the cause of dentofacial anomalies. Advances in medical and dental genetics are now providing further insight. Various growth factors induce formation of ‘growth centres’, and malformation may occur because these centres are defective or there is a lack of coordination between them.
Cleft lip is more common in Mongoloid races and rare in Negroids. A family history exists in 12–20% of complete cleft cases. The gene responsible for the expression of transforming growth factor beta 3 has been implicated in human cleft palate. A genetic predisposition to anomalies such as clefting may reach a threshold after which environmental factors come into play. There is, for example, an association between the anticonvulsant phenytoin and cleft disease. Excess vitamin A is similarly associated, while folic acid is important in the prevention of cleft disease. Infections in the mother such as rubella have also been implicated in cleft formation in the infant.
The craniosynostoses result from premature fusion of the craniofacial sutures and may arise sporadically when a single suture is involved or are inherited in the more complex syndromes. The diagnosis may be made according to the clinical presentation alone or involve molecular biological techniques to provide a genetic diagnosis now that access to such testing is more widely available.
It is important to establish what is of concern to the patient. There may be difficulty in eating or problems with speech or the appearance of the teeth or face. Patients may be reluctant to discuss dissatisfaction with their appearance and feel that it is more acceptable to present a functional problem to the clinician. They should, therefore, be reassured of the legitimacy of describing their aesthetic problem and the effect it has on them. Family members may underestimate the significance of abnormality to the patient and inhibit the patient in this discussion.
Children with abnormal appearance of teeth or face may suffer nicknames and teasing from other children, and this can affect their psychological development. The development of emotional attachment between child and parents can also be adversely affected. In adulthood, many subtle influences come into play. Attractiveness has been shown to be related to social advantage, so that more attractive individuals are, for example, more likely to find a partner and more likely to be successful in the work environment. The general public have difficulty in accepting facial disfigurement and prefer to look away or ignore the individual concerned. Correction of abnormality can be very beneficial to the patient and this benefit can be displayed in many ways, such as improved peer relationships and social confidence.
Occasionally, a patient may present requesting surgery for improvement of a small or non-existent physical defect. The clinician should arrange referral to a liaison psychiatrist in this situation in case the patient is suffering from body dysmorphic disorder (BDD). Similarly, clinical neurosis and frank psychosis should be excluded before surgery. Patients with these conditions will not be satisfied with the outcome and may have very severe postoperative problems.
Fig. 9.1 shows the occlusion of a patient with severe asymmetry owing to overgrowth of her left mandible.
Cephalometric analysis: Lateral skull tracing for cephalometric measurements may be carried out manually with tracing paper and pencil or digitised tracing may be performed for computer-assisted analysis and operation planning. Radiographic landmarks are shown in Fig. 9.2 and also, the lines that are then drawn between some of these landmarks. The angles between these can then be compared with standard values to indicate facial skeletal variations from normal. Digital photographic images may also be superimposed on the radiographic images and surgical predications carried out with the computer software.
For dentofacial anomalies, the diagnosis will describe the maxillary and mandibular base relationship relative to the skull together with a description of the dental occlusion and comments about general condition of the dentition and oral hygiene. The mandible and maxilla may be described as prognathic, hypoplastic or asymmetrical. The effect of these may be to produce a long face, open bite or short face. The chin may also be described using various classifications of excess (macrogenia), hypoplasia (microgenia) and asymmetry. For craniofacial anomalies, the diagnosis will also describe the orbits, eyes, ears and other features and may suggest various syndromes in a differential diagnosis.
• Preoperative orthodontic management to move teeth into a position for the best possible occlusion at operation. This may involve relief of crowding, flattening of the occlusal plane or other treatment.
Orthognathic surgery involves the correction of occlusal and facial disharmony. Such surgery may play a part in gender reassignment treatment to produce a more feminine or masculine face. Surgery carried out to change racial characteristics or the facial characteristics in conditions such as Down syndrome is controversial. The majority of patients who undergo orthognathic surgery are referred by their general dental practitioner either directly or via an orthodontist because they have a malocclusion that is beyond the scope of orthodontic management alone. Advances in orthodontic treatment and surgical management has led to predictable outcomes from orthognathic surgery.
1. A surgical plan is made to correct the abnormality described by the lateral cephalometric tracing. The surgically predicted outcome may be produced readily by computer software packages designed for this use and visualised on screen.