Ortho-surgical management of skeletal malocclusions

Introduction

The rehabilitation, attainment and maintenance of a well-functioning masticatory apparatus in adult patients with dentofacial deformity would require the involvement of several dental specialists. Although the adult patient may seek dental treatment for simple reasons like discomfort, pain or aesthetics, an accurate diagnosis may reveal a need for more extensive treatment. The need for comprehensive treatment is far greater now with increased life expectancy, better health care and demand from social and peer pressures.

Therefore, a clinician should offer contemporary treatment options for existing malocclusion and deformity to the patient, who may or may not choose a treatment based on his personal/financial/social or other unknown reasons.

Individuals with severe malocclusion resulting from facial skeletal disproportions cannot be treated solely with orthodontics. These individuals exhibit an inherent imbalance among craniofacial structures, which includes variations in facial height, width and anteroposterior dimensions. The severity of these imbalances can vary, and they may affect deep facial structures, including the orbital, zygomatic and cranial areas. Facial disproportions can present as misaligned centre lines or facial asymmetry and canting of occlusal plane.

Surgical procedures performed to enhance facial aesthetics and correct jaw imbalances are referred to as orthognathic surgery (Orthos means straight; Gnathos means jaws). Orthognathic surgical procedures can be performed on one jaw, both jaws (bimaxillary) or in conjunction with surgery on craniofacial structures, including the orbits, zygoma and cranium.

While minor skeletal problems can be treated with orthodontic camouflage, more severe forms of malocclusion and facial disproportions need surgical correction. In the opinion of 28 orthodontists who independently evaluated 30 sets of pre-treatment dental models, they perceived that a positive overjet more significant than 8 mm, a negative overjet of 4 mm or greater and a transverse discrepancy larger than 3 mm were not orthodontically treatable.

These malocclusions would need additional mode of therapy which may include skeletal anchorage and implants-supported orthodontics or surgical procedures to correct the deformities.

Historical perspective

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Historically, surgery on the mandible preceded that of the maxilla. Hullihen was the first to perform osteotomy surgery on the lower jaw to treat deformity caused by a burn.
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Vilray Blair, for the first time, performed an osteotomy of the mandibular body to correct prognathism in 1887, later called the St Louis operation.
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Subsequently, Blair reported mandibular body osteotomy in 1906 and horizontal osteotomy of the ramus, with the external approach in 1907.
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The contemporary orthognathic surgery has much to owe to the contribution of H. L. Obwegeser, who introduced intraoral bilateral sagittal split osteotomy (1942 first description published, 1957).
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The bilateral sagittal split osteotomy (BSSO) technique was further modified by Dal Pont. BSSO with its modifications is a widely accepted procedure on the mandible for a variety of deformities.
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Cheever, as early as 1864, was the first to do a down-fracture of the maxilla to resect nasopharyngeal mass in two patients. Wassmund reported his initial attempt to perform a maxillary osteotomy. Wassmund employed post-operative orthopaedic traction to position the maxilla without surgically mobilising it. Later Obwegeser fully mobilised the maxilla in a single step and brought it into the predicted position.
•
The technique to move the maxilla in three dimensions of space emerged revolutionary, as did the sagittal split osteotomy in the mandible. The primary concern was the preservation of the vascularity to prevent necrosis of the maxilla, which had been thoroughly researched by then. It is now well understood that intact palatal and maxillary soft tissue pedicles attached to the osteotomised segments preserve the vascularity, allow healing and minimise the risk of tissue necrosis.
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In the 1960s, Obwegeser started to perform maxillary surgery and described an extensive series of cases treated with Le Fort I osteotomy. Obwegeser also reported simultaneous repositioning of the maxilla and the mandible in 1970.
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The success of bimaxillary surgery has enabled the correction of severe deformities of the face. Technological and biomaterial inventions have led to the development of rigid internal fixation, mini plates and bioresorbable rigid fixation devices. Orthodontic diagnosis and treatment planning have considerably improved with knowledge of growth and newer imaging devices that enable 3D virtual planning and estimating post-surgical profiles. Also, quality care in anaesthesia and post-operative patient care have synergised together to advance orthognathic surgery, resulting in minimal complications and quality outcomes. Distraction osteogenesis with multiple vector control devices is the most recent advancement in this field. These developments have already influenced treatment planning and therapy in skeletal deformities.

Pre-surgical orthodontic treatment

Before the 1960s, orthognathic surgery was performed without orthodontic treatment, or sometimes surgery was planned after orthodontic treatment was over. In a few situations, orthodontic treatment was considered only after surgery.

Horowitz, in 1969, emphasised the importance of orthodontics in this field and integrated it with orthognathic surgery. In this ‘team approach’, oral surgeon and orthodontist complement each other and take up their unique roles, where assessment, planning and execution are done in a coordinated manner with each specialist doing their specialist jobs after interactive discussion and approval and review and modification if needed. Not all orthodontists are experienced and involved in surgical orthodontics; the same applies to oral surgeons.

Motivational factors involved in seeking orthognathic surgery

Aesthetics

The aesthetic impairments may alter the psychological well-being of a subject with a facial deformity and create perceptions of negative self-image and poor social well-being. Many psychosocial studies have shown cosmetic motivation as the primary reason for seeking orthognathic surgery. However, it may vary across sociocultural groups. The type of malocclusion and associated functional problems may directly affect aesthetics and motivation for the treatment. It has been reported that patients with class III deformity rated themselves less attractive than class II patients. After the surgery, they felt significantly more improvement in attractiveness/self-confidence compared to class II patients. A large proportion of these class III patients suffer from aesthetic and functional problems related to their appearance before treatment, and aesthetic improvement was the primary driving force for their decision to seek treatment.

Functional problems

Functional problems are often associated with severe jaw deformities but are rarely the main reason for seeking orthognathic surgery. The following are the functional reasons for seeking orthognathic surgery:

1.
Problems of articulation of speech. These problems are common in patients with anterior open bite and severe deep bite.
2.
Temporomandibular joint (TMJ) problems, especially in class III patients.
3.
Periodontal and gingival health, such as in traumatic deep bite.
4.
Obstructive sleep apnoea (OSA).
5.
Compromised masticatory efficiency due to a decreased number of functional occlusal contacts.
6.
Tumour of the jaws.
7.
Ankylosis of TMJ.

Case selection for orthognathic surgery

Indications

1.
Many deformities are developmental aberrations of the facial structures that may have a familial trend. These subjects, who have otherwise normal health, may suffer from varying aesthetic and functional impairments.
2.
Some of the patients reporting for surgery are those who are not satisfied with the outcome of orthodontic treatment aimed to camouflage their facial skeletal problems.
3.
Subjects exhibiting skeletal class III malocclusion with or without mid-face hypoplasia.
4.
Subjects with severe class II skeletal malocclusion that cannot be corrected with orthodontics alone.
5.
Long face syndrome and vertical maxillary excess.
6.
Facial asymmetry.
7.
Orthognathic surgery is required for cleft palate patients who have small maxilla, which is consequent to the growth inhibitory effects of scarring caused by the primary surgery of the lip and palate.
8.
Children who have acquired jaw deformity due to ankylosis of the TMJ (unilateral or bilateral).
9.
Post-traumatic jaw deformities due to malunited fractures.
10.
Orthognathic surgery is indicated in patients with OSA to enlarge the oral space and prevent the tongue from falling back during sleep.
11.
Orthognathic surgery may also be needed to correct deformities due to the tumours of the condyle, such as unilateral condylar hyperplasia.
12.
Other groups of orthognathic patients constitute children born with craniofacial deformities.

Unsuitable cases for orthognathic surgery

1.
Orthognathic surgery is not indicated for patients with mandibular prognathism caused by tumours of the endocrine glands and endocrine disorders such as acromegaly.
2.
The psychological state of the patient is an essential consideration before taking a case for orthognathic surgery. Adults who have complex behavioural issues or known psychological disorders should undergo a thorough evaluation to determine their mental fitness for surgery.
3.
While having medical conditions is not an absolute reason to refuse surgery, patients must be assessed based on the type and severity of the disease condition and its potential impact during or after the surgical procedure.

History and clinical evaluation

Often, patients with malocclusion first report to an orthodontist, who may seek advice and consultation with the oral surgeon for a detailed assessment of the case for a prospective surgical patient.

A thorough examination and assessment of medical, dental, social, psychological and financial aspects is essential for a potential patient considering orthognathic surgery. Additionally, evaluating the clinical problem and conducting necessary investigations are crucial steps.

The important steps are:

1.
Medical and dental history
2.
Extraoral examination
3.
Intraoral examination
4.
Diagnostic records: Digital 3D scan of face and teeth, CBCT and superimposed dental and soft tissue scans.
5.
Possible visual treatment objectives (VTOs) and predictions/mock surgery
6.
Reassessment in joint sessions with an oral surgeon

Evaluation of the face constitutes an assessment of the following parameters:

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Vertical proportions
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Sagittal problems
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Transverse problems
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Symmetry of the face/midline deviations
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Nose and its impact on the overall facial profile

Extraoral examination

Evaluation of the face

It includes visual observation and palpation of the facial structures, the prominence of the bony contours, muscle thickness and the quality of the soft tissue. A thorough clinical examination of the face is conducted to evaluate and assess the overall profile and shape of the face. The type of face shape (long and thin, broad and short) and the location of the skeletal problems of the lower jaw alone, upper jaw, upper jaw with mid-face or a combination of lower face and mid-face are assessed ( Fig. 79.1 ).

The severity of the problem is assessed in anteroposterior, vertical and transverse dimensions in a totality of the face and for each jaw separately, including the nose. Facial asymmetry and skeletal midline deviations are also evaluated. The assessment is done with regard to soft tissue function, especially smile and speech.

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Assessment of facial proportions and discrepancy in three dimensions of space.
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Zygoma and forehead, orbits, the width of the face and proportions.
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Evaluation of the soft tissue of the face, its thickness and muscle mass.
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Nose and forehead: nose width of alar bases.
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Lip thickness, muscle mass and behaviour at rest, during smiling, speech and swallowing.
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Incisor show, gingival show at rest and during posed smile and spontaneous smile.
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Nasolabial angle, lip height and contour.
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Inter-labial gap, lip seal, strain on mentalis muscle and depth of the mental sulcus.
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The shape and thickness of the chin and its overlying tissue.
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Type of face? That is a horizontal or vertical type, ramus height, gonial angle, chin position, chin thickness and chin shape.
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Any facial asymmetry or chin deviations during the closure, in centric occlusion or at rest of the mandible.
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TMJ evaluation for its health and the possible impact of surgery.

It is an essential and critical part of the evaluation process. It is important to measure the height of the upper face (from the nasal bridge to the base of the nose) and to know the cant (inclination) of the palatal plane.

Symmetry of the face

It is evaluated at an imaginary mid-sagittal plane. If facial asymmetry is suspected, it should be confirmed with the analysis of a PA cephalogram. The facial asymmetry may vary from a slight deviation of the chin during functional closure in centric occlusion to a gross asymmetry of the mandible and face. Developmental facial asymmetry can be seen in children who have been treated for ankylosis of the TMJ or malunited fractures of the condyle or ear infections involving TMJ. The other causes could be pathological, such as condylar hyperplasia. Facial asymmetry can be seen in congenital face defects such as hemifacial microsomia (HFM) or unilateral cleft lip and palate.

Nose

Nose morphology can be a major contributing factor to an unaesthetic appearance of the face. In a well-balanced face, the nasal width at the alar base is equal to the inter-canthal distance. A detailed examination of the nose includes evaluation of the columella, nasal tip and nasal dorsum.

The shape of the nose and the width of the nasal base are important considerations, and the surgeon must evaluate and predict the influence of the orthognathic surgery procedure on the alar base width and nasal tip. For example, a forward movement of the maxilla aimed to correct negative overjet would result in the widening of the nasal base. This problem should be evaluated and addressed before or during the surgery.

Examination of the lower face

It includes an assessment of the ramus height and anterior lower facial height. The ratio of posterior to anterior facial heights is an important consideration both clinically and cephalometrically.

For example, a subject with a large gonial angle, increased lower anterior face height and smaller posterior face height would need a different approach to surgical planning in contrast to the patient who has a wide ramus body, acute gonial angle, increased height of the posterior face and decreased lower face height.

The anterior open bite may be limited to the vertical excess of the lower jaw or both the jaws. Subjects with long face syndrome have a long, narrow face with an excessive height of the maxilla and increased visibility of the gingiva and teeth (gummy smile), anterior open bite and increased lower anterior facial height.

In the frontal view, the face is divided into five equal segments by vertical lines. The mid-segment is formed between two vertical planes passing at the inner canthus of the eyes. In a well-balanced face, these planes should pass through the base of the alae of the nose. The next lateral segments are formed on either side of the plane passing at the inner canthus of the eyes and the plane passing through the outer canthus of the eyes. This outer plane should usually coincide with the gonial angle. The outer two-fifths segments essentially represent ears, and their widths may have to be improved by the plastic surgeon if the ears are disproportionate to the rest of the face. The width of the mouth normally should be equal to the inter-pupillary distance.

Intraoral examination

The following parameters need to be assessed:

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Amount of overjet and overbite
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Sagittal relations of the molar, canine and occlusal contacts
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Posterior cross bite and width of the maxilla
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Width of the mandible
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Inclinations of the anterior teeth
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Inclinations of the posterior teeth
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Cant of the occlusal plane in a transverse direction
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Mid line deviations in relation to mid sagittal reference plane
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Crowding/spacing
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Curve of Spee
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Functional examination during opening and closing of the mouth

Evaluation of the oral hygiene status, periodontal health, missing or extracted teeth and need for maintenance of general dental health are also assessed. The possible need for restorative work and optimisation of oral health is a prerequisite before considering a case for orthognathic surgery.

Functional examination

Evaluation of speech and indulgence of the speech therapist is required in subjects with nasality of voice, cleft lip and palate patients, and those with articulation problems.

Examination of the oral cavity volume and size of the tongue is an important aspect of the clinical examination. Evaluation of the size of the tongue is of particular significance in skeletal class III patients. A setback surgery can pose volume constraints when accommodating a large-sized tongue. Tongue size reduction procedures may need to be included in the plan in such clinical situations.

Diagnostic records and investigations

Complete detailed records for orthognathic surgery include:

1.
Facial photographs including frontal and lateral profile views, and 45 degrees at rest and in the smile.
2.
Study models with wax bite recorded in centric occlusion and centric relation.
3.
Lateral cephalogram and PA cephalogram are required in almost all cases of class III malocclusion and vertical excess patients to assess transverse problems.
4.
Orthopantomographs and intraoral periapical radiographs are required to assess the interseptal bone available for making surgical cuts. Oral surgeons like to assess the thickness of the bone available and its density apical to root apices for surgical cuts.
5.
Additional records include a cone beam-computed tomography (CBCT) scan. (For a detailed description, see Chapter 37 .)
6.
3D facial scans obtained with stereophotogrammetry (3dMD) are optional; however, they are a great tool for 3D virtual planning and prediction of post-treatment profiles.
7.
Digital dental scans for planning following their integration with CBCT and face scan.

Cephalometric and computer-based prediction technology

Various cephalometric analyses are available to ascertain the location of the dysplasia and its severity. Lateral cephalometric radiograph prediction technology should be considered, with the limitations of a 2D image of the 3D skeleton. PA cephalogram is a valuable adjunct, especially in cases of facial asymmetry. Analysis of the PA cephalogram provides valuable information on midline deviations and transverse discrepancies of the maxilla and mandible. Cephalogram tracings can be superimposed on Bolton’s standard tracings, which provide an instant graphics display of the site, the severity of the problems and the possible correction required to achieve an average profile.

Role of digital cephalometric and video imaging in treatment planning

Before the advent of possibilities of direct digital images, acquisition of the skeleton and its on-screen manipulation through the computer, hand-drawn cephalometric tracings were used to predict and assess the post-treatment profile following repositioning of the maxilla and mandible by cutting the tracing template(s). Hence, treatment planning in terms of the amount of movement of the jaws, location of the surgical cuts, rotation of the osteotomised segments, execution and outcomes could be predicted. The cephalometric tracings supported by the model mock surgery add to the transverse and vertical models of the occlusion and dental bases.

The current cephalometric analysis systems are supported by powerful software functions that allow possibilities of ‘on-screen’ digital image acquisition either directly from a digital cephalostat or through a scanner and ‘on-screen cephalometric analysis’ and storage of data. The process is quick and accurate for the landmarks digitised. The digital photographic images, taken in a standardised manner, are calibrated and superimposed on the digital cephalogram image. The software functions facilitate ‘on-screen mock surgery’, movements of the skeleton segments and morphing of the soft tissue profile that is the likely outcome of the surgery. The soft tissue changes of the patient are predicted and morphed based on the data provided by the research studies. Dynamic smile analysis is done through video imaging techniques. ^,

The predicted image enhances communication with the patient, who can visualise the outcome of the surgery and boosts his/her confidence. However, these systems have limitations of accuracy whereby the actual surgical outcome may vary. Computer predictions may have ethical and legal implications.

3D models

3D models with CBCT and digital reconstructions are other technical advancements in this field. Herein, the digital CT images obtained through CBCT are used for the reconstruction of the patient’s skeleton and soft tissue. CBCT offers the distinct advantage of much lower radiation doses than what conventional MDCT offers. It provides a real-life view of the bony structures and therefore allows detailed surgical treatment planning ( Fig. 79.2 ). The bone thickness and relations with anatomical structures such as neurovascular canal and teeth roots can also be visualised. Stereolithography models can be generated using CT data. Surgeons can plan a mock surgery, simulate outcomes and design splints.

Stereophotogrammetry

Stereophotogrammetry is used in clinical practice to evaluate the face forms before and after treatment with surgery. The technique uses specialised cameras that estimate the 3D coordinates of an object (e.g. face) using multiple photographic images taken from different positions, front and side, which have similar points in each camera’s field of view (FOV).

It can capture the object (a patient’s face) in ~1.5 ms to generate a precise digital 3D model of the human anatomy. It is likely that 3D surface images will soon replace traditional 2D photographs. 3D surface imaging has a wide range of clinical and research applications in surgery, orthodontics, anthropometry, treatment planning and assessment of outcomes. The most significant advantage is that of its non-invasive nature of ultra short (~1.5 ms) capture speed, which is instantaneous and especially suited for imaging young, restless children. The images offer possibilities for marking the landmarks on patient surface data and analysis. Calculating and comparing several parameters, such as linear, angular and complex surface distances, ratios, areas and volumes is possible. With 3dMD, it is possible to obtain surface data from cross-sectional views on any plane or intersecting plane. The images are of high quality and can be exported for use in cross-consultations through telemedicine. The image allows simulation and superimposition with radiological images such as 3D CBCT ( Fig. 79.3 ).

A summary of clinical features and important cephalometric features of skeletal jaw anomalies are compiled in Fig. 79.4 .

Special considerations during surgical treatment planning

Social history and patients’ expectations, including psychological assessment

Psychological profiling constitutes an important aspect of treatment planning because case preparation, surgical treatment and post-surgical management require considerable time, effort and cost. Hence, it is relevant to assess the psychological state and the perception of the patient towards treatment at the beginning of the consultation. This may involve psychological evaluation or sometimes psychiatric assessment for depression and paranoid behaviour.

Two types of motivations have been described for patients seeking orthognathic surgical treatment:

1.
External
2.
Internal

Persons with long-standing feelings about deficiencies in one’s appearance and negative self-image would be internally self-motivated and are likely to be more satisfied after the surgery. Meanwhile, persons with external motivation, such as requirements in a career or pressure from their spouses/partners to look better or different, may not be good candidates for surgery. A few patients are those whose internal motivation is activated by social, professional or career needs.

Importance of age in orthognathic surgery

Orthognathic surgery should be delayed till adulthood so that the skeletal growth is completed and the deformity is fully expressed. The mandible grows till late in adulthood, more so in subjects with true mandibular prognathism. The mandible may continue to increase well beyond the average age range. Sexual dimorphism in skeletal and somatic maturation should be kept in mind. The earliest recommended age for orthognathic surgery in females is 14.9 and 16.5 years in males.

It is also important to highlight that the age at which surgery is to be performed is also influenced by the type of deformity to be corrected.

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Surgical intervention in skeletal class III patients may have to be delayed until completion of the mandibular growth, which may be as late as 22–24 years in males while much earlier in females.
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Mandibular deficiency patients may need to undergo surgery early before the growth is complete.
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Maxillary vertical excess patients can also have surgery before growth is complete.

Tissue considerations-related factors

Hard tissue considerations: There are three crucial hard tissue considerations, which are affected significantly by growth and hence are indirectly influenced by the age of the individual. These are:

1.
Active growth and maturation of the skeletal tissues of the craniofacial skeleton.
2.
Late mandibular skeletal growth.
3.
Third molars: extraction before, during or after the surgery or no extraction.

Soft tissue considerations: The growth of the soft tissue of the face should be evaluated and correlated with chronological age to analyse the current situation and possibly predict the soft tissue changes in lips, nose and chin during maturity.

Age 13–16: The growth of the nose, in particular, has a greater impact on the overall profile and outcome of the orthognathic surgery. Boys show greater growth at the tip of the nose (nasal prominence), which increases significantly compared to girls between the ages of 13 and 16 years.

Age 18–42: Between ages 18 and 42, the nose increases in size in all dimensions in men. The profile straightens with lips becoming retrusive, with a decrease in upper lip thickness and increased lower lip thickness. There is an increased soft tissue thickness at the pogonion. The tip of nose grows downwards.

Among women, changes are different from those of men in a similar age group. The profile does not become straighter, and the lips do not become more retrusive. The nose increases in size in all dimensions. There is a decreased soft tissue thickness at pogonion. For men, most of the hard tissue changes have occurred in 25 years, whereas soft tissue changes in the nose, lips and chin occur much after the age of 25 years. For females, both hard and soft tissue changes occur more after 25 years of age than before.

Age 45–83: Behrents documented age changes between ages 17 and 83 years on the Bolton–Brush Growth Study sample. The significant changes were an increase in a nasal droop or nasal prominence and the nasal tip that moved more inferiorly. The lips became less prominent and tended to be located inferiorly, thereby covering the incisor show or decreasing visibility during a smile. These considerations have a bearing on the amount of incisor visibility to be planned at the time of maxillary surgery.

Steps involved in an orthognathic surgery procedure

1.
Pre-orthodontic preparatory phase
2.
Pre-surgical orthodontic treatment phase
3.
Surgical phase
4.
Post-surgical orthodontic phase
5.
Prosthodontic treatment phase, rehabilitation of occlusion and aesthetic dentistry
6.
Follow-up and retention

Pre-orthodontic preparatory phase

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Tags: Kharbanda's Orthodontics: Diagnosis and Management of Malocclusion and Dentofacial Deformities, M Ali Darendeliler

May 10, 2026 | Posted by drzezo in Orthodontics | 0 comments

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Ortho-surgical management of skeletal malocclusions

Introduction

Historical perspective

Pre-surgical orthodontic treatment