General medical and dental history

Medical‐surgical and dental histories must be obtained for every orthognathic patient prior to examination. While most patients will have been seen already at an orthodontic diagnostic clinic and a medical history recorded, the surgeon will wish to probe any reported issues in greater depth to reduce the risk of patients entering the treatment pathway for whom surgery may turn out to be complicated or even contraindicated when the time for arranging admission comes. A social history is also important, to try to ascertain accurate information about the levels of any smoking habits or alcohol consumption, which can affect fitness for surgery and subsequent recovery.

Patients should be attending their general dental practitioner regularly, but it is important to establish if they have been through periods of dental neglect or experienced significant problems with their teeth, including episodes of treatment or extractions. In some cases, a patient’s malocclusion, and the detrimental esthetics associated with it, may have discouraged them from looking after their teeth and detailed questioning may be needed to gain an accurate history.

Patient’s concerns

It is important that a patient seeking treatment for a dentofacial deformity can express clearly defined concerns, and it is essential that these are fully explored early in the assessment process. Severe malocclusions will often be accompanied by functional difficulties, such as incising food in the case of an anterior open bite or reverse overjet. Esthetic concerns can be related to either the jaw discrepancy, the teeth, or a combination of both. Where dental appearance is the main concern, it may be that orthodontic alignment alone is all that is required for a satisfactory result, but where occlusal function and/or facial appearance are the major concerns, surgery is more likely to be required. The clinical psychologist plays a key role in identifying patients who have disproportionate concerns or, in more severe cases, BDD, which would contraindicate surgery.

Facial assessment

The first step in evaluating a patient’s face is to gain a subjective impression of his or her dentofacial deformity. The eye of an experienced clinician can assess the region and extent of any key deficiencies or excesses, and observing patients as they walk into the room and then during conversation, with its accompanying facial animation, yields valuable information about how their facial esthetics may differ from the accepted norm. Viewing the face in all three planes of space is essential and the bird’s‐eye (from above) and worm’s‐eye (from below) views can be very informative, particularly where an asymmetry is present. We consider it essential that both the surgeon and the orthodontist examine the patient together, since both clinicians will naturally tend to focus on slightly different aspects of the dentofacial complex and discussing their combined observations will then allow the most accurate and complete picture to be assembled.

It is important to then look at specific aspects of the facial soft tissues in a more objective manner, and numerous soft tissue profile analyses are available, which include variables such as facial convexity, naso‐labial angle, labio‐mental angle, lip‐chin‐submental plane angle, submental plane‐neck angle, Frankfort‐mandibular planes angle (FMPA), upper lip length, lower lip length, and so on. It is important for the lips to be relaxed during the examination to avoid posturing, which can distort the profile and the vertical relationship of the lips to the teeth. Patients should be evaluated in an upright sitting position and encouraged to adopt a natural head position (NHP). This should ensure that the antero‐posterior jaw relationship and profile are accurately assessed (Ayoub et al. 2013a; Figure 20.1). Where angles are being measured and compared to published norms, analysis of profile photographs and/or a lateral cephalogram may be more useful. However, we would emphasize that numerical values should be regarded only as supplementary information, which can serve to confirm clinical judgment in many cases, but should not be relied on to dictate treatment planning.

In the average facial type, the clinically observed vertical dimension can be divided into two equal parts: the lower anterior face height (LAFH), measured from subnasale to soft tissue menton, and the upper anterior face height (UAFH), measured from glabella to subnasale. The ratio of the LAFH to the total anterior face height (TAFH) should therefore be 50%. For the evaluation of transverse proportions, the rule of fifths can be used as a practical guide, in which the face comprises five equal portions. This is particularly useful in assessing the width of the alar base (the middle fifth), which should ideally be equal to the intercanthal width (Naini and Gill, 2016). The balance between vertical and horizontal proportions should be maintained where possible to achieve facial harmony (Ayoub et al., 2013a). Asymmetry should be assessed in each step during the systematic approach of dentofacial examination for each component, including the level of the eyes and ears. Any cant of the occlusal plane should be carefully examined and documented. A practical method of assessing this is to lay a wooden spatula across the occlusal surfaces of the maxillary posterior teeth, which can be compared to another horizontal reference plane (usually the interpupillary line). A detailed discussion of dentofacial assessment and clinical parameters is beyond the scope of this chapter, but further information is available in other texts, including our Handbook of Orthognathic Treatment (Ayoub et al., 2013a).

It is also important to consider the patient’s overall physical build, including height and general body shape. A tall, thin patient is likely to suit dolichocephalic dentofacial features, while a short, stocky patient is more likely to fit well with brachycephalic features, and this can influence the surgical plan. For example, a short female patient who presents with an increased LAFH and moderate Class III discrepancy, due to mild maxillary deficiency and mild mandibular prognathism, will tend to derive a pleasing esthetic outcome from mandibular setback, rather than maxillary advancement. A key step in this scenario, therefore, is combining dentofacial assessment and body status information for the planning of optimal surgical goals.

Both soft and hard tissues of the dentofacial complex require systematic assessments to identify any dentofacial dysmorphology. A systematic approach to guide clinical evaluation should ensure accurate and complete information and avoid missing fundamental parameters that may be important in planning surgery for optimal facial esthetics (Figure 20.2). Clinicians should consider the philosophy of aiming to achieve balance, proportions, and harmony of the dentofacial components, based primarily on clinical assessment, rather than surgical correction based on numerical values derived from objective analysis.

Nose

The size and morphology of the nose can affect overall facial esthetics and therefore needs special consideration during the assessment and planning of orthognathic treatment. Dentofacial deformities are commonly associated with some nasal deformities. For example, maxillary deficiency is often coupled with a narrow alar base, drooping of the nasal tip, and a mild dorsal hump, which often improve as a result of Le Fort I advancement osteotomy (Seah et al., 2012). However, other nasal deformities may require a separate rhinoplasty, particularly where asymmetry and septal deviation are involved. The nose may look bigger or smaller than its actual size based on the position of the maxilla (Posnick, 2022). For example, Le Fort I advancement with clockwise rotation in cases of maxillary deficiency associated with Class III jaw discrepancies will improve the nasal profile, midface prominence, and overall facial harmony.

Where maxillary impaction is required to correct vertical maxillary excess, clinicians should be aware of the potential negative effects on nasal esthetics. In particular, flaring of the alar base can result, as well as asymmetry of the nostrils, nasal septum, and tip (Almukhtar et al., 2018; Ubaya et al., 2012; Ayoub et al., 2016). These abnormalities can usually be managed simultaneously with Le Fort I osteotomy through adequate trimming of the nasal septum and placement of a cinch suture to control the alar base width.

Temporomandibular joints

Details of any temporomandibular joint (TMJ) problems should be recorded, followed by a comprehensive examination, as part of orthognathic patient assessment. Abnormalities of the TMJs include symptoms such as pain, clicking, or grinding noises, in addition to a history of any previous therapy. Clinical signs of TMJ abnormalities in radiographic assessments include limitation of mouth opening or locking of the joints, while radiographs may suggest lysis of the condylar heads, which might warrant further investigation. Temporomandibular dysfunction (TMD) has a multifactorial etiology. Al‐Moraissi et al. (2017) reported on a systematic review and meta‐analysis of 29 studies on the effects of orthognathic surgery on TMD. They concluded that there were no identified preoperative symptoms of TMD, nor any specific skeletal deformity, which could have predicted the TMD outcome after orthognathic surgery. Several limitations were associated with this review, including different study designs and short follow‐up, as well as lack of controls and considerable variability. There is therefore a need for more prospective randomized control trials using appropriate sex‐matched and age‐matched controls to identify more clearly the effects of orthognathic surgery, if any, on TMJs. Clinicians must inform TMD patients that orthognathic surgery could not be guaranteed to improve their condition and that there is also a chance that they could be negatively affected. Moreover, there is a possibility that new symptoms can develop after orthognathic surgery (Al‐Moraissi et al., 2017; Dujoncquoy et al., 2010; Dolwick and Widmer, 2018).

Intraoral examination

For patients referred through the orthodontic clinic, dental and periodontal health will already have been assessed, but it is important to ensure that patients do not have uncontrolled dental or periodontal disease that could cause complications with the surgery or adjunctive orthodontic treatment (Musich, 2012). As a general rule, dental or periodontal disease should be treated and the patient made fully “dentally fit” before progressing further along the orthognathic pathway; oral hygiene should also be satisfactory. If good plaque control is not being maintained prior to any surgical or orthodontic intervention, it is less likely that the patient will cope with the cleaning regime required during the early postoperative period, when oral access is restricted and uncomfortable. In addition, any areas of gingival recession, whether secondary to disease or physiological bony dehiscence, should be noted and photographed, since both orthodontic tooth movement and surgery could result in one or more of these progressing.

For most patients, an orthodontic assessment will have been carried out on a previous clinic, but it is worth going through this again as part of the orthognathic assessment. Trimmed study models (or virtual models produced from intraoral scans) should be available for the MDT clinic, and this helps greatly with accurate assessment and documentation of the occlusal relationships. The overjet, overbite, and any crossbites, along with the arch forms and the presence of an accentuated curve of Spee, must be assessed. However, it is important to check that the study models are correctly trimmed or articulated, particularly if the patient tends to posture the mandible forward or off to one side. It is essential to make sure the patient’s condyles are fully seated, so that the true extent of the antero‐posterior occlusal discrepancy is known and recorded, prior to planning any treatment. In our experience, patients with retrognathic mandibles and backward growth rotations frequently have a habitual forward posture and can be difficult to induce into a retruded contact position. It is equally important in Class III cases with a reverse overjet and increased overbite to ascertain if the patient is able to contact their incisors edge to edge, before displacing them forward into a more comfortable occlusion. Failure to unmask these postural habits can result in surgical planning starting from the erroneous position and adversely affect the outcome.

The upper incisal show at rest and on smiling, along with any gingival show, are essential baseline measurements since they must be considered in planning any vertical maxillary movement. The relation of the maxillary dental midline to the envisaged midline of the face, as well as to the mandibular dental midline, should be assessed. Where there is an asymmetry of the upper face it can be difficult to find a mid‐facial line and clinical judgment is needed. The mandibular dental midline should also be assessed in relation to the midpoint of the chin, so that any mandibular asymmetry is accounted for.

The presence of a deep overbite or open bite requires measurement and documentation. The nature and extent of an open bite are important, and whether it is associated with an accentuated upper curve of Spee or level arches. The size and posture/function of the tongue need to be evaluated, particularly in cases of open bite, where it may be part of the etiology and could affect stability after surgical correction. Macroglossia and scalloping of the tongue’s lateral sides are commonly associated with open bite or excessive bimaxillary dental proclination (Wolford and Cottrell, 1996).

The presence of unerupted and impacted teeth should be assessed, using radiographs where necessary. Unerupted third molars may require surgical removal in advance of orthognathic surgery, usually leaving at least nine months for healing, but this is down to surgical preference and some surgeons are content to remove 8s, where necessary, at the time of surgery (Verweij et al., 2016).

Radiographic assessment

The patient’s general dental practitioner will usually have taken whatever intraoral radiographs have been required to diagnose and then manage any dental or periodontal disease, but a dental panoramic tomograph (DPT), taken as part of the initial orthognathic assessment, will occasionally identify caries, bone loss, apical areas, or other pathology. In such cases, further investigation and management may be indicated before the patient can progress further along the pathway. Apart from acting as a hard tissue screen, the DPT provides information regarding the morphology of the mandible and its condyles, which can vary significantly with the vertical dimension of the face. More detailed tomography of the condyles may be indicated in cases where lysis is suspected with, for example, a progressive anterior open bite. Where mandibular asymmetry is present, a DPT can give some information about any difference in size and shape of the condyles and their necks, and this may be supplemented by radioisotope scanning in some cases if progressive asymmetrical growth is suspected. Asymmetries in the length and depth of the body of the mandible will also be apparent, although accurate positioning of the patient in the machine is essential to avoid distortion of the image, which can give a false perception of asymmetry.

The presence and position of unerupted and impacted teeth, including third molars, must be identified. The DPT is a useful image in this regard, but it provides very limited information in the transverse plane. This makes the orientation and relative positions of hard tissue structures difficult to determine. This is particularly true of the transverse position and course of the inferior dental canal, which is of relevance in the planning of the sagittal split osteotomy. The DPT also gives no information about the thickness of the mandibular cortical plates or cancellous space, which can influence the quality of the sagittal split procedure. An image that provides three‐dimensional (3D) information is therefore of superior value, for both diagnosis and contemporary surgical planning.

The advent of cone‐bean computed tomography (CBCT) has brought about a paradigm shift in the diagnosis and planning of orthognathic patients. Traditionally, lateral and postero‐anterior cephalometric radiographs have been used for routine radiographic assessment of dentofacial deformities, with numerous analyses available, aimed at quantifying the various aspects of the craniofacial dysmorphology using linear, angular, and proportional variables. Most of these analyses relate to the lateral cephalogram, which represents only the antero‐posterior and vertical planes and is therefore a two‐dimensional (2D) representation of a complex 3D object composed of multiple bilateral structures. While comparing mean values to published norms is informative, the information should be carefully interpreted and correlated to the clinical findings. In addition, facial asymmetry cannot be readily analyzed using lateral cephalometry due to its complexity. We are now of the opinion that it is the 3D morphology of the patient’s face, as assessed subjectively by the clinicians, that should guide treatment planning, rather than numerical data. The 3D cephalometric analysis of CBCT images is a potentially valuable tool that could overcome some of the limitations of 2D cephalometry, but normative values have not yet been established and its validity and accuracy have yet to be confirmed. Further work is therefore required around landmark identification and standardization of measurements on CBCT images before this becomes a widely accepted method for the 3D quantification of dentofacial deformities (Weiss and Read‐Fuller, 2019; Wang et al., 2020; Yitschaky et al. 2011).

In contemporary orthognathic clinics, CBCT may now be considered as the gold standard for assessment of hard tissues, including facial asymmetry, and 3D orthognathic planning (Weiss and Read‐Fuller, 2019; Almutairi et al., 2018). In our clinic, it has now largely replaced conventional 2D cephalograms. The thresholding of the CBCT image can be adjusted to show both the craniofacial soft and hard tissues, which allows it to be used for both surgical planning as well as soft tissue prediction, with the aid of dedicated software, which is now widely available.

It is important to be mindful of the higher levels of radiation that CBCT exposes the patient to, and each clinician must be able to justify the radiographic views he or she requests on the grounds of their diagnostic yield.

Clinical photographs

Conventional 2D clinical photographs consist of a series of intraoral and extraoral images, which should be as standardized as possible. Extraoral photographs should include frontal views at rest and on smiling; right and left profiles; right and left three‐quarter profiles; and bird’s‐eye and worm’s‐eye views. Together, these provide a comprehensive record of the patient’s facial appearance and should be taken before any treatment starts and then at key stages throughout, to monitor progress and change. Intraoral photographs should consist of upper and lower occlusal views, front and lateral views of the teeth in occlusion, and overjet (or reverse overjet). It is our protocol to take postoperative photographs annually for five years for patients who continue to attend review appointments.

In our clinic, we also use stereophotogrammetry to record standardized 3D images of the face, which can be rotated and viewed from any angle. These give a true 3D representation of the face, and the presurgical capture is used in conjunction with the CBCT image for photo‐realistic orthognathic planning. In addition, these images can be used to show topographical changes to the soft tissues produced by surgery, or due to growth, such as asymmetries, by superimposing sequential captures on stable regions of the face (Al‐Rudainy et al., 2019).

Study models

Dental study models should be available at the first MDT clinic appointment. They allow detailed assessment of the patient’s occlusion, as well as allowing the clinicians to try out different possible postoperative occlusions by freehand articulation. Having two sets of models is advisable so that one set can be used, if necessary, for provisional model surgery at the early planning stage, particularly if segmental surgery is being considered.

Where intraoral scanners are being used to produce digital models only, it may be more challenging and time consuming to manipulate the models into new trial occlusions because of the absence of haptic feedback (feel) from the occlusal surfaces of the teeth. One of the advantages of physical models at the initial planning stage is the ease with which the clinicians can assess how the teeth would fit together in the proposed postoperative occlusion. Study models, whether physical or digital, should be acquired at the key stages of treatment, at least up to and including the removal of any orthodontic appliances following surgery.

Treatment planning process

The process of conventional orthognathic treatment planning can be approached in two fundamental ways. The first could be called “orthodontically led” planning, where the initial aim is to set the upper and lower incisors as near as possible to their cephalometric norms in relation to their respective skeletal bases. The overjet (or reverse overjet) produced by this presurgical decompensation then largely dictates the size of the surgical jaw movements and, in turn, the corresponding soft tissue changes. The potential problem with this approach, in our opinion, is that the orthodontic tooth movements achieved may not necessarily deliver the jaw movements required for optimal facial esthetics. In addition, complete decompensation, carried out with the aim of achieving ideal incisor inclinations, may create an excessive overjet or reverse overjet, requiring bimaxillary surgery, where partial decompensation would have allowed single‐jaw surgery and still produced satisfactory esthetics.

The second method could be called “soft tissue‐guided” planning, in which the starting point is to decide the soft tissue changes that will deliver the desired esthetic result, and then plan the jaw movements to produce those changes. The orthodontic treatment is then planned to facilitate the jaw movements, and may involve partial, rather than complete, decompensation in some cases. It is this second method that the authors prefer, because orthognathic surgery will inevitably produce a change in facial appearance. Considering the soft tissues first should increase the likelihood that the treatment is targeted at addressing the patient’s concerns. However, the orthodontist must be careful to consider what orthodontic tooth movements are possible. If the magnitude of surgical jaw correction decided on requires tooth movements that cannot be achieved, a compromise will have to be agreed. Envisaging the soft tissue changes required for optimal esthetics relies on the experience of the clinicians and is subjective. Where there is disagreement among the team members regarding the desired goals, it is important to involve the patient as much as possible in the decision‐making process, focusing carefully on the patient’s concerns and expectations.

For most patients, in addition to a functional deficit, the lack of soft tissue harmony is their main concern. Our orthognathic treatment planning process starts with identifying the required soft tissue changes, which guide the movements of the osteotomy segments and inform the orthodontic tooth movements. The need for clockwise or anti‐clockwise rotation of the maxillo‐mandibular complex should be considered, taking into consideration the need to adjust the chin. The position of the maxilla is planned to place the upper incisors in their ideal relationship to the upper lip, both at rest and on smiling, as well as correcting the upper dental midline. Careful consideration should be given to the effect of any proposed maxillary movements on the nose and lips, as well as any deficiencies of the zygomatic bones or infraorbital rims. Any repositioning of the mandible should also consider the throat length and possible effects on the airway. Carrying out soft tissue prediction planning can be helpful at this stage, to illustrate different options such as single‐jaw versus bimaxillary surgery, but the limitations of whichever software is used must be made clear to the patient.

Once there is agreement between the clinicians and the patient as to what the treatment objectives are, consideration can be given to the way in which the treatment is to be carried out.

Orthodontics‐first approach

In the conventional or “orthodontics‐first” approach (OFA), a provisional surgical plan is made prior to the start of presurgical orthodontics, with is then aimed at positioning the teeth to allow the desired surgical jaw movements and produce the best possible arch coordination. Final surgical planning is not carried out until up‐to‐date records have been taken with the teeth in their final decompensated positions. The positions of the teeth will then dictate the magnitude of the antero‐posterior skeletal jaw correction, which should be guided by the required soft tissue changes. This can be predetermined to some extent by agreeing a “target (reverse) overjet” that the orthodontist aims to achieve. Final surgical planning is then carried out to confirm the individual jaw movements, whether single‐jaw or bimaxillary, along with the vertical dimension and any necessary chin adjustment. Following surgery, postoperative orthodontics continues, with the aims of achieving optimal arch coordination and interdigitation. Despite the widespread use of the conventional pathway, it has been shown to have a long duration, with presurgical orthodontics taking between 15 and 24 months, and 36 months for the total treatment on average (Behrman and Behrman, 1988). In addition, presurgical dental decompensation tends to exaggerate the patient’s malocclusion, particularly in Class III cases, and this has been shown to have adverse psychological effects (Liao and Lo, 2018). (See Cases 20.1–20.4.)

Surgery‐first approach

The surgery‐first approach (SFA) has been widely reported in the literature over the past decade or so (Nagasaka et al., 2009; Sugawara et al., 2010; Villegas et al., 2010; Hernández‐Alfaro et al., 2011a; Anwar et al., 2022). Because the surgery is carried out at the start of the treatment journey, the orthodontic treatment is carried out in a single continuous phase afterwards. For the patients, this means that the correction of what is usually their main problem, the jaw discrepancy, happens right at the start, and they do not have to suffer the adverse functional and esthetic effects of presurgical orthodontic decompensation.. In addition, the treatment duration is greatly reduced, partly due to the uninterrupted nature of the pathway, but also because the soft tissue environment of the teeth has been normalized, which would be expected to aid dental decompensation rather than resist it (Behrman and Behrman, 1988). In addition, there is some evidence that the rate of tooth movement is increased through the “regional acceleratory phenomenon” due to surgical trauma in the early postoperative period (Peiro‐Guijarro et al., 2016; Baek et al., 2010; Hernández‐Alfaro et al., 2014). Another contributory factor to the rapid treatment progress is the reduced appointment intervals that the SFA requires, because of the need to closely monitor patients in the postoperative healing phase. Their orthodontic mechanics also demand intensive supervision to ensure that the teeth are moving in the desired way to correct the secondary malocclusion. Appliance adjustments therefore tend to be carried out much more frequently than for nonsurgical orthodontic patients, with appointments every few weeks (Barone et al., 2020). Such intensive supervision along with the reduced treatment duration would also be expected to reduce the risk of orthodontically induced iatrogenic damage.