CC
A 17-year-old White female is referred by her orthodontist for combined surgical–orthodontic management of her anterior open bite (AOB; apertognathia) and mandibular hypoplasia. The patient complains: “I have difficulty eating and would like to have my open bite fixed.”
Patients presenting for orthognathic surgical correction of skeletal deformities or malocclusions often have functional problems. Correction of these issues can also impact the patient’s facial appearance. It is essential to differentiate the degree of functional versus cosmetic dissatisfaction. Successful outcomes require this distinction to be well integrated into the surgical plan.
HPI
The patient reports difficulty chewing certain foods because of the AOB and is also concerned about her facial profile, including her retrusive chin. She admitted a history of thumbsucking, however, she denied a history of tongue thrusting. The cause of AOB can be as simple and straightforward as a digital habit or multifactorial and related to skeletal, neuromuscular, or respiratory factors. Tongue thrusting is a difficult parameter to rule out, and an unrecognized tongue-thrusting habit can cause future relapse of surgical and orthodontic treatment. Macroglossia should also be recognized and treated as needed by tongue reduction surgical procedures if deemed appropriate.
As a teenager, the patient completed extensive orthodontic therapy attempting to close her AOB; however, this progressively relapsed over time. Although relapse is unfortunate for the patient, orthodontic closure of a larger AOB does have a high relapse rate. One week before her orthognathic surgical consultation, the patient had orthodontic appliances placed by her orthodontist once again to begin her definitive correction for this problem. The patient was congenitally missing the right maxillary third molar, but the remaining third molars are full bony impactions. Most surgeons prefer that impacted mandibular third molars be extracted at least 6 months before mandibular sagittal split osteotomy procedures to avoid complications related to fixation. Maxillary molars do not necessarily need to be removed in advance. The patient has no history or symptoms of temporomandibular joint disease (TMD). Preexisting TMD should be recognized and addressed before orthognathic surgery because these surgical procedures can either cause or exacerbate preexisting TMD symptoms. Some surgeons recommend simultaneous orthognathic and temporomandibular joint (TMJ) surgery in select cases of preexisting anterior disk displacement; however, this issue is highly controversial. Total TMJ joint reconstruction in conjunction with orthognathic surgical correction for select malocclusions can be accomplished predictably.
PMHX/PSHX/medications/allergies/SH/FH
Noncontributory.
Elective orthognathic surgery should be avoided in patients classified as being American Society of Anesthesiologists (ASA) III or higher unless their health issues can be clinically improved before the procedures. Many patients who have failed nonsurgical management of obstructive sleep apnea have comorbidities qualifying them for an ASA II or III status. These patients may undergo maxillomandibular advancement or orthognathic surgical procedures electively when optimized and typically will do well. Preoperative anesthesia evaluation as well as a discussion of risks are especially important when working with patients with an ASA II class or higher. Consideration for postoperative recovery in the intensive care unit may be indicated.
Examination
The examination of a patient for orthognathic surgery can be divided into four components: TMJ, skeletal, dental, and soft tissue. Skeletal discrepancies, either hypoplasia or hyperplasia, should be assessed in three dimensions: transverse, anteroposterior (AP), and vertical. As for all surgical patients, the airway, cardiopulmonary, neurologic, and other organ systems should be fully assessed in anticipation of the use of general anesthesia.
The maxillofacial examination of the current patient proceeded as follows.
- 1.
TMJ component
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The muscles of mastication and the TMJ capsule are nontender, with no evidence of clicking or crepitus, which is typically seen with disk position or integrity issues. The maximal interincisal opening is 45 mm, with good excursive movements and no deviation upon opening or closing, consistent with a normal TMJ examination.
- 2.
Skeletal component
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There is no vertical orbital dystopia. The intercanthal distance is 31 mm. A normal range is 30 to 34 mm. The intercanthal distance varies with ethnicities, and individualized care should reflect these considerations. The nose is straight and coincident with the facial and skeletal midline. Malar eminences are within normal limits.
- a.
Transverse dimension
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The maxillary dental midline is coincident with the facial midline.
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The mandibular dental midline is 1 mm right of the maxillary dental midline.
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The chin point is 2 mm right of the maxillary midline.
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The maxillary occlusal plane is canted down 1 mm on the right at the canine.
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The mandibular angles are level.
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The maxillary arch width is adequate.
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- b.
AP dimension
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Overjet is 6 mm.
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The nasolabial angle is 110 degrees (normal is 100 degrees ± 10 degrees).
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The labiomental fold is deep.
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The chin is retrognathic.
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The profile is brachycephalic.
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- c.
Vertical dimension
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The maxillary incisor length is 10 mm.
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Upper incisor show is 3 mm at rest. Ideally, there are 2 to 4 mm of tooth show at rest and 8 mm in full smile. In an esthetically pleasing smile line, the gingival papilla or up to 1 mm of gingival margin is visible at full smile.
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- a.
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AOB is 7 mm.
- 3.
Dental component
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Open bite is 7 mm at incisors and 3 mm at canines, with divergent occlusal planes ( Fig. 62.1 ).
• Fig. 62.1 Preoperative intraoral view revealing anterior open bite.(Courtesy of Dr. Vincent J. Perciaccante.) - •
Overjet is 6 mm (normal is 3.5 mm ± 2.5 mm).
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A class II relationship is present at the first molars and canines bilaterally.
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The arch width is adequate on handheld articulated models.
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The curve of Spee has been leveled.
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The dentition is in good repair. The third molars were not visible on clinical examination.
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The mandibular arch form is good. There is no mandibular occlusal cant.
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- 4.
Soft tissue component
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The upper lip has adequate thickness and length.
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The nasolabial angle is 85 degrees (normal is 100 degrees ± 10 degrees).
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The nasal contour is within normal limits (dorsum, alar base, tip).
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Imaging
Panoramic radiograph and lateral cephalometric radiographs are the minimum imaging modalities necessary for orthognathic surgery. Preoperative profile, frontal (repose and smiling), and occlusal photographs should be obtained. Advances in computer-aided design and computer-aided manufacturing technology has contributed to break throughs for treatment planning in orthognathic surgery beyond virtual surgical planning (VSP). The combined orthodontic and orthognathic surgery digital workflow requires cone-beam computed tomography (CBCT) and digital impressions for VSP, orthodontic treatment planning, and fabrication of patient-specific implants (PSI) (i.e., custom cutting guides and titanium fixation plates).
The current patient’s panoramic radiograph showed normal bony architecture of the condylar head and no other pathology. The right maxillary third molar was missing, and the left maxillary and left and right mandibular third molars were full bony impacted with minimal root formation ( Fig. 62.2 A).
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