Introduction
The overall management of a patient with facial deformity requiring orthognathic surgery is both an art and a science. The management must be based on a team approach. Whilst the team may vary according to local circumstances, the optimum would consist of an orthodontist, an oral and maxillofacial surgeon, a liaison psychiatrist or clinical psychologist, a specialist in restorative dentistry, supported by a maxillofacial technician. A speech therapist is essential for cleft cases and plastic surgery expertise should also be available on an individual patient basis. Whilst a patient may be referred to any of the above specialists, it is important that all patients follow an agreed care pathway to ensure patient satisfaction with the outcome. Unfortunately the patient's personal concerns may be overlooked and it is imperative that as part of the initial consultation, patients are encouraged to state precisely what specific aspects of their facial features and or dentition they would like corrected, for what reason and the length of time that they have sought treatment. Research has shown that clinicians and the general public differ in their perception of an ideal face. Whilst the patient can be guided to what constitutes an ideal facial appearance, it is vital that the clinician does not lose sight of the patient's underlying concerns. The motivation behind the request for treatment is also very important and special consideration is required when marked psychological factors appear to influence both the diagnosis and the treatment.
Combined orthodontic/surgical treatment goals are:
· Improve facial aesthetics
· Improve dental aesthetics
· A functional, balanced and stable occlusion
· A satisfied patient.
The management protocol for facial deformity should comprise the:
· History
· Clinical examination
· Investigations
· Initial diagnosis
· Treatment plan
· Presurgical orthodontics
· Final treatment plan
· Surgery
· Postsurgical orthodontics
· When appropriate, restorative dentistry, psychological intervention or support and speech therapy will be required.
History
The purpose of the history is to identify the patient's orofacial problems and their cause. This may be a family trait, congenital deformity, or trauma in infancy or adolescence. It is useful to ask the patient to draw up a problem list in order of priority of the specific features they wish to have corrected and for the clinician to note where the drive for treatment has arisen. For example, a patient may complain of having a prominent chin, which they have noticed ever since adolescence and for which they have frequently requested treatment through the general dental practitioner. This differs from the sudden desire to change minimal deformity as a response to a personal crisis. The long term success in terms of patient satisfaction is far better when driven by the patient than that of a patient seeking surgery driven by a parent, partner or close relative. The overall treatment goals must be to improve facial and dental aesthetics, and to provide a functional, balanced and stable occlusion but with the underlying premise that these satisfy the patient's reasonable wishes.
The Medical History
Most orthognathic patients are young and fit to undergo a general anaesthetic and prolonged surgery. Occasional disorders, which require specific attention include:
i) haemophilia or similar clotting disorders which require pre-and intraoperative correction
ii) acromegaly patients may be a cardiomyopathy risk
iii) antibiotic or analgesic idiosyncrasy or allergy
iv) rheumatic or congenital heart valve lesions
v) obstructive sleep apnoea should warrant a sleep study and specific assessment.
Body Dysmorphic Disorder (Formerly Dysmorphophobia)
A small but significant proportion of patients may present with varying degrees of concern about one or more aspects of their facial appearance without appropriate clinical signs. This may be a manifestation of a psychiatric disturbance now called Body Dysmorphic Disorder (formerly dysmorphophobia). This condition will create problems in surgical management as the patient is often dissatisfied with the final result. The condition raises the conflict as to whether one does,
i) what the patient wants
ii) what the patient needs
iii) or nothing.
It is therefore worth considering in some detail. See Chapter 6.
Evaluation of the Patient
Patient Evaluation
· Clinical examination
· Radiographic examination
· Analysis of study models
· Psychological examination where appropriate.
Introduction
The full examination must include the simultaneous scrutiny of the patient, radiographs, cephalometry and study casts. The evaluation of the orthognathic patient should begin with a systematic examination of the patient's facial features from both the frontal perspective (vertical proportions) and the lateral profile (horizontal relations). It is important to consider the vertical facial proportions and their balance in relation to the patient's general build, and personality. Examples of patients who may not need surgery are: (i) a young female patient who possesses a vivacious and extrovert personality suited to a mild Class II malocclusion accompanied by a broad smile and marked incisor exposure and (ii) similarly, a well-built male may be suited to a mild Class III malocclusion with a minor degree of mandibular prognathism. It is also important to take into consideration the overall facial shape, as clearly there is extreme variation from a square shaped facial appearance to one of a long ovoid appearance. In the former case this may fit in well with a shorter stature whereas a longer face may be more suited to a tall individual. At the moment these decisions are based on experience and intuition.
Clinical Examination
The clinical examination should be undertaken with the patient comfortably seated with the Frankfort plane horizontal. Not only is it easy to visualise a line running from the inferior orbital margin to the upper end of the tragal cartilage, but this can be readily compared with the same horizontal plane on the lateral skull radiograph (cephalogram) and photographs.
Frontal Assessment
There are several important facial features to note. These include:
a) The facial proportions
The useful classic guide is to consider the face as having three equal vertical components (Figure 1.1): The distance from the hairline to the soft tissue bridge of the nose; from the soft tissue bridge of the nose to the alar base and from the alar base to the chin. It is also important to determine whether or not there is a relative excess or deficiency in the vertical height of either the maxillary or mandibular thirds.
b) The alar base width
Traditionally in a westernised population it is accepted that the alar base width, as measured from the lateral aspects of the alar cartilages of the nose, should be approximately equal to the intercanthal distance as measured between the inner canthi of the eyes (Figure 1.2). This measurement has importance when planning a maxillary impaction.
Figure 1.1 The superficial aesthetic proportions of the face can be divided into equal thirds. However the underlying cephalometric proportions of the upper to the lower facial height are 45:55 (see Figure 2.3).
Figure 1.2 The alar base width should approximate the inner intercanthal distance.
c) Incisor exposure (the lip — incisor relationship)
For a patient with an average upper lip length of 20-25 mm, the standard exposure for orthognathic planning of the upper labial segment with the lips parted at rest should be 2-4mm of the incisor crown. On smiling, the exposure should increase to the level of the gingival margin of the upper labial segment. This assessment is crucial when planning the ultimate vertical height of the mid face. Quite clearly the amount of incisor exposure should be inversely proportional to the length of the upper lip. (Figure 1.3). Where the upper lip length is very short then the patient would expect to show more of the upper incisors. Any attempt to reduce the incisor exposure in relation to a short upper lip will lead to an unaesthetic reduced middle face height. Similarly, with a long upper lip, the patient would be expected to show less or no upper incisor, both at rest and during facial animation. The lip incisor measurement should be done with the face at rest. Animation especially smiling will enhance the face and make planning difficult.
The harmony between the components of the lower third of the face is also important, in that the subnasale to the upper lip vermillion border should be a third of the total (i.e. half of the lower lip vermillion border to the soft tissue menton). In those cases where the lower third of the face appears overclosed, it is wise to re-evaluate both the upper lip length and the incisor exposure with the mouth open so that the lips are taken just out of contact.
d) Facial asymmetry and centre line relationships
It is important to note any asymmetry of the middle or lower third of the face, including the position and levels of the eyes. This may be facilitated by marking the midlines on the patient's face and also by analysing a clinical photograph or surface laser scan.
The patient's maxillary and mandibular dental midlines may not be coincident nor match their skeletal midlines (Figure 1.4).
Figure 1.3 With an average upper lip length, a useful aesthetic proportion is (a) 2-4 mms of maxillary incisor crown visible with the lips apart at rest. (b) Increasing to the level of the gingival margin on smiling. (c) The excess incisor exposure of vertical maxillary excess at rest is important for the estimation of the required vertical impaction. (d) The aesthetic animated face makes this estimation difficult.
Generally where the maxillary dental midline is displaced to one side of the skeletal midline, there is an indication for orthodontic correction rather than attempting to rotate the maxilla in order to produce a dental midline coincident with the midface. Where a mandibular dental midline discrepancy is noted in relation to the upper midline, it is important to determine whether it is coincident with a mandibular skeletal asymmetry or of purely dental origin. Where the skeletal asymmetry and dental midlines coincide the centre lines will be corrected as part of the surgical procedure.
Figure 1.4 (a) The facial asymmetry of a left-sided hemimandibular elongation with the chin point displaced to the right. The lower dental midline mirrors the mandibular skeletal asymmetry and will be corrected as part of the surgery. (b) The maxillary dental midline is displaced to the left of a symmetrical maxilla and therefore should be corrected as part of the orthodontic preparation of the case. (c)Postural camouflage showing tilting of the head to level the lip line, in an asymmetrical face can give a false impression of orbital dystopia. (d) Levelling the occlusal plane with bimaxillary osteotomies also “levels” the eyes!
Postural camouflage can be a problem with the asymmetrical face (Figures 1.4c and 1.4d). The patient with a marked occlusal cant habitually tilted the head to level the lip line giving the impression of orbital dystopia. This was corrected by bimaxillary levelling of the occlusal plane.
Profile Assessment
As with frontal evaluation it is important to work down the face from above to observe several key features.
a) Relative protrusion of the maxilla and mandible
The relations of the maxilla and mandible to each other and to the skull base will be discussed in greater detail in Chapter 2. It is very common for patients to complain of a big chin, whereas it is the relationship of the maxilla to the skull base which is at fault, i.e. a hypoplastic maxilla related to a normal mandible. This can be clinically demonstrated by simply padding out the upper lip with soft wax or cotton wool (Figure 1.5) until the lip relationship and facial profile appear normal. Similarly, the surgical correction of a retrognathic mandible may be visualised by asking the patient to slide the mandible forwards (Figure 1.6). Most orthognathic cases require a combination of both maxillary and mandibular surgery and an easy assessment of the relative protrusion of the mid third and mandible can be made by assessing their position relative to the perpendicular to the Frankfort plane passing downwards through the soft tissue nasion. With normal facial proportions the soft tissue profile of the maxilla should be approximately 2-3 mm in front, and the soft tissue pogonion should lie 2 mm behind this facial plane (Figure 1.7). However the face can vary with ethnic norms, giving anterognathic, mesognathic or posterognathic profiles.
Figure 1.5 (a) Apparent mandibular prognathism. (b) Padding the upper lip suggests a maxillary advancement will harmonise the profile and maintain a “strong chin”. (c) Masking the mandible facilitates judging the mid face.
Figure 1.6 Forward posturing of the mandible will help to visualize the horizontal and vertical effects of a mandibular advancement to correct a marked Class II deformity.
b) Position of the infra-orbital margin
A good indicator of middle third hypoplasia arises from the relative protrusion of the maximum convexity of the globe of the eye in relation to the infra-orbital margin. Ideally the globe should be just 2-3 mm in advance of the infra-orbital margin (Figure 1.8).
Figure 1.7 (a) The relative protrusion of the mid third and mandible can be assessed by a perpendicular to the Frankfort plane passing downwards through the soft tissue nasion. With “normal facial proportions” the soft tissue profile of the maxilla should be 2-3 mm in front of the line and that of the mandible 2-3 mm behind.
Figure 1.7 (b) The “normal profile” can vary with concepts of beauty and ethnic variation as is seen above showing: (a) the anterognathic, (b) mesognathic, and (c) posterognathic norms.
Figure 1.8 A patient with midface hypoplasia. Note the retruded infra-orbital margin relative to the globe of the eye, which should only be 2-3 mm in front of the orbital margin.
c) Nasal morphology
The appearance of the nose will often change both relatively and anatomically with many osteotomies. For instance, an apparent large nose may appear more acceptable following a bimaxillary correction (Figure 1.9) due to the change in the adjacent soft tissue drape. Alternatively, a Le Fort I maxillary advancement and/or impaction will tend to raise the nasal tip and straighten a nasal hump unless modifications to the surgical procedure are included (Figure 1.10). Where a formal rhinoplasty is considered essential, it should always be undertaken as a separate surgical procedure once the changes produced by the jaw surgery have stabilised. See Chapter 12.
The importance of the nasolabial angle in the surgical planning process will be discussed in greater detail in Chapter 5. However it is important to record the nasolabial angle, should be slightly greater than 90 degrees indicating optimum lip support (Figure 1.11)
Figure 1.9 (a) The relative prominence of the nose seen preoperatively is diminished with a bimaxillary correction, (b) which has radically changed the adjacent soft tissue drape.
Figure 1.10 Maxillary impaction and advancement can raise the nasal tip.
Figure 1.11 The nasolabial angle is assessed at the intersection of tangents to the columella (lower border) of the nose and the upper lip.
d) Morphology of the ears
The ears, being first arch derivatives, may concurrently suffer with a gross facial deformity. The ear deformity associated with hemifacial hypoplasia (microsomia) will require reconstruction at a later stage (Figure 1.12). It is not uncommon for the external auditory meati to lie at unequal levels. This creates an asymmetrical facial artefact and difficulties when taking a facebow recording for transfer to the articulator. See Chapter 7. Bat ears appear to be an independent abnormality and do not seem to concern most adults.
e) Chin depth
When assessing the facial height in the frontal and sagittal plane, the lower facial third can be further subdivided into the upper lip which forms one-third, whilst the distance from the lower lip margin (stomion) to the chin margin (soft tissue men-ton) should comprise two-thirds of the lower facial height.
Figure 1.12 Severe ear deformity in a patient with hemifacial microsomia.
Taken together with the chin profile this is an important component for correcting jaw disproportion (Figure 1.13).
f) Chin-Throat angle
Some patients request cosmetic surgery for an excess fat deposit in the throat region. This should be distinguished from a dewlap which is a fold of loose skin. As a consequence the fat gives a bulky contour below the chin. Surgery to setback the mandible may occasionally accentuate this build up of submental soft tissue, in which case liposuction or plastic surgery procedures may need to be incorporated into the postoperative surgical plan. However in the young patient the submental neck area usually remodels spontaneously after a setback.
Figure 1.13 The upper lip length should be a third of the lower facial height.
Temporomandibular Joint Examination
Although there is no evidence of malocclusion or jaw deformity causing temporomandibular joint symptoms, it is important to record any abnormalities present in patients considering surgery. The examination of the joint should include observation of the path of opening and closure of the mandible, noting any clicking sounds whilst palpating the joints. If a click is present, it should be noted how this relates to the opening or closing cycle. Also, the extent of maximum opening should be recorded.
Intraoral Examination
A full intraoral dental examination must be carried out with the study models and radiographs.
1. Record the teeth that are present or unerupted and any that are impacted, carious, overerupted or periodontally involved. This is often overlooked.
2. The following orthodontic base line notes should include:
a) A definition of the dental occlusion and dental base relationships.
b) Any dental centre line discrepancies relative to each other and the facial midline and chin point.
c) Any crossbite indicating a discrepancy in the transverse relations. This includes both anteroposterior and buccal crossbites. It is important to check and record whether there is any associated displacement or deviation of the mandible on closing. In the buccal segments, it is also important to note whether the segments have attempted to compensate for the discrepancy by tipping of the dentition.
d) The upper and lower incisor inclinations and in particular, compensatory changes due to the jaw disproportion, e.g. retroclined lower incisors and proclined upper incisors in a prognathous mandible.
e) The presence of crowding or spacing together with any tooth size discrepancies. Note also any tilting and rotation of teeth.
f) The levels and shape of the occlusal planes, both the antero-posterior curves of Spee, and the transverse occlusal plane. A wooden spatula placed across the transverse occlusal plane can help identify any cant in relation to extraoral structures, for example, the interpupillary line.
g) The depth of the overbite and whether it is complete or incomplete. The size of the overjet from the most prominent incisor should also be recorded.
h) Whether the maxillary intercanine width can accommodate the lower arch.
i) The arch form and the coordination of upper and lower arches.
3. Examine and record the tongue size and mobility, and the speech pattern.
4. Enlarged tonsils may jeopardise the patency of the airway. Adenoids are rarely a problem as they have usually regressed in size during early adolescence. However, remember that the micrognathic mandible will create an intubation problem for the anaesthetist.
5. Cleft cases require careful analysis of the cleft site and bony defects that will require grafting. Velopharyngeal competence should be examined by endoscopy and speech recorded by a speech therapist.
Investigations
Radiographs
1. A panoramic film, e.g. orthopantomograph shows at a glance:
a) Any unerupted and impacted teeth.
b) The shape and relative size of each half of the mandible, including the condyles, in two dimensions.
c) The presence of any pathological condition such as impacted unerupted teeth, caries, periodontal disease, apical granulomas or cysts.
d) The trabeculation pattern of the bone, especially at the lingula, which when visible is an indication of adequate thickness of the ascending ramus and ease with which the ramus can be split.
2. The true lateral skull radiograph is taken with the head in a reproducible position with the aid of a craniostat. The tube is set 1.5 m from the film so that the central parallel rays are used, producing a life-sized image with minimal distortion. Ideally the teeth should be in centric relation (retruded contact position), i.e. the mandible should be gently closed to the natural retruded cuspal contact position to approximate to the supine anaesthetised centric relation during surgery. However, the influence of centric occlusion and centric relation on planning will be discussed in Chapter 7.
3. A craniostat posteroanterior view of the skull helps to reveal facial bone asymmetry. However, remember that the head may be tilted in the craniostat if the external auditory meati are asymmetrically placed, giving a misleading image.
4. Long cone periapical films are essential for assessing the space between teeth when segmental surgery is required.
5. A maxillary occlusal radiograph defines the bone defect in cleft cases.
6. Major deformity is best visualised with a 3-dimensional CT scan.
If the patient elects to have surgery, a preoperative chest radiograph is required by some surgeons but is only justified where a costschondral graft is to be harvested.
Study Models (Casts)
Impressions are taken for study models, together with a careful interocclusal record (“squash bite”) so that the models can be trimmed in centric relation. This is done with the patient in a relaxed supine position. The models must show all the teeth present as well as the sulci. The patient's name, hospital number and the date of taking the impressions must be marked on them after trimming in a standardised manner (e.g. Angle or Tweed).
Initially two replicas are made of the originals and one set is mounted on an anatomical articulator using a facebow recording, although a simple plasterless articulator is suitable for those cases involving mandibular surgery alone. Model surgery is discussed in detail in Chapter 7.
In cases of posterior open bite, a plaster backing block may be required, although the majority of the planning will be undertaken on an articulator.
Photographs
The basic orthognathic series of colour images consists of (Figure 1.14):
i) Full face at rest and smiling.
ii) Right profile but both profiles with any asymmetry.
iii) Anterior teeth and right and left buccal segments in occlusion.
Figure 1.14 A basic orthognathic series of photographic records.
iv) Some also include occlusal views of the upper and lower dentition.
v) Cleft cases require a palatal view.
vi) Cleft and rhinoplasty patients also need an inferior view of the alar margins to capture problems of asymmetry.
In addition, some surgeons use black and white prints of the patient's profile for treatment planning but as the 1:1 object-image profile photograph is not exactly comparable to the lateral skull tracing, there is little value in superimposing them for planning purposes. These techniques have been largely superseded by the advent of digital imaging and the development of computer imaging and morphing software programmes which are used to simulate surgical changes (Chapter 3).
Photographs should be taken pre-and postoperatively as a surgical audit, for teaching and rarely for medico-legal reasons. If photographs are to be of value, hair must be retracted from the face and ideally moustaches and beards removed.
Lateral Skull Tracing
The “true lateral skull” radiograph is traced manually or digitised by computer for cephalometric analysis.
These will be discussed in detail in Chapter 3 and in the sections on deformities.
The Diagnosis
With many patients this can be readily stated, together with its surgical solution, at the first clinical examination; for example, “mandibular prognathism requiring a sagittal split osteotomy push-back”. However, without more formal scrutiny, bimaxillary, orthodontic, restorative and periodontal problems will be overlooked.
Complex deformities require a detailed appraisal by the surgeon and orthodontist jointly, and even then a surgical solution may not suggest itself immediately. Hence it is useful to describe the case under the following headings, in the form of a “problem list”.
1. The jaw relationship and facial proportions, including the nose and ears
2. Orthodontic diagnosis
3. Restorative, including periodontal problems
4. Speech
5. Psychological assessment.