Orthognathic, TMJ, Chin 1-22 Flashcards
Which of the following cephalometric planes extends from the most superior aspect of the external auditory canal through the inferior orbital rim?
A) Facial plane angle
B) Frankfort horizontal plane
C) Nasion-pogonion plane
D) Sella-nasion plane
The correct response is Option B.
Numerous points, angles, and planes may be identified on a standard cephalogram. The sella is the midpoint within the sella turcica. The nasion is the most anterior point of the frontonasal suture in the midsagittal plane. The pogonion is the most forward-projecting point on the anterior surface of the chin. The Frankfort horizontal is a line extending from the porion (the superior extent of the ear canal) to the orbitale (inferior extent of the orbit). The Frankfort horizontal was originally introduced at an anthropological conference in Frankfurt, Germany, in 1884. It is used to orient the craniofacial skeleton and serve as a relation to other descriptive planes. The facial plane angle extends from the nasion to the pogonion. It is used to measure the degree of protrusion or retrusion of the lower jaw.
A 21-year-old man undergoes discectomy for the treatment of temporomandibular joint internal derangement. Which of the following long-term complications is most likely for this patient?
A) Ankylosis
B) Condylar remodeling
C) Facial (VII) nerve injury
D) Frey syndrome
The correct response is Option B.
The temporomandibular joint (TMJ) is described as a ginglymoarthrodial joint since it is both a ginglymus (hinging joint) and an arthrodial (sliding) joint. A superior joint space is separated from an inferior joint space by a disc. The arterial supply to the TMJ is provided by the branches of the superficial temporal branch of the external carotid, in addition to the deep auricular, ascending pharyngeal, and maxillary arteries. Nervous innervation is provided by the auriculotemporal and masseteric branches of the mandibular nerve (cranial nerve V3). Resection of the disc is a treatment for internal derangement that is not responsive to conservative measures. The most common long-term complication of discectomy is remodeling of the mandibular condyle. While Frey syndrome, facial (VII) nerve injury, and ankylosis are possible, they are less common than remodeling.
An 18-year-old man with a history of cleft lip and palate repair is planning to undergo orthognathic surgery to correct his malocclusion. When counseling the patient regarding complications, which of the following is the most common complication after orthognathic surgery?
A) Dental injury
B) Hardware failure
C) Hemorrhage
D) Infection
E) Nerve injury
The correct response is Option E.
Large-scale studies involving hundreds to even thousands of patients have demonstrated the safety and risks associated with orthognathic surgery. Although all of the complications listed in the options have been described during orthognathic surgery, the most common complication is nerve injury ranging from 12.1 to 19%. Infection has been reported from 2 to 3.4%. Hardware failure occurs in up to 2.5% of cases, while dental injuries range from 0.14 to 5%. Significant hemorrhage occurs in 0.5 to 1.4% of cases. Additional complications associated with orthognathic surgery include postoperative temporomandibular joint disorders/condylar disorder, scar problems, and necessity of secondary surgery.
A 23-year-old woman with vertical maxillary excess is scheduled to undergo a LeFort I osteotomy with impaction. During this procedure, which of the following pairs of arteries is most likely to be disrupted?
A) Ascending pharyngeal and ascending palatine
B) Greater palatine and facial
C) Maxillary and lesser palatine
D) Nasopalatine and descending palatine
E) Sphenopalatine and pterygopalatine
The correct response is Option D.
Understanding the vascular anatomy of the maxilla is critical to successfully performing a Le Fort I osteotomy. In addition to the periosteal blood supply from the mucosal attachments, there are several named vessels that supply the palate and alveolar processes, which are mobilized in a Le Fort I osteotomy. Of the answer choices listed, the nasomaxillary and descending palatine arteries are commonly disrupted during surgery. After downfracture, the ascending palatine and ascending pharyngeal arteries become the dominant blood supply to the segment.
A 17-year-old girl presents for correction of Angle class II malocclusion, 8 mm of overjet, and retrognathia/retrogenia. Mandibular advancement and genioplasty are planned. Which of the following is the most likely outcome of this procedure?
A) Decreased presence of the nasolabial folds
B) Decreased prominence of the labiomental crease
C) Increased area of the glossopharyngeal opening
D) Increased area of the velopharyngeal opening
E) Increased cervicomental angle
The correct response is Option C.
Understanding the anatomic changes after orthognathic surgery is crucial in helping to select the appropriate intervention as well as for informing patients about their expected results. Patients undergoing mandibular advancement (bilateral sagittal split osteotomy [BSSO]) and genioplasty surgery can expect predictable outcomes. The labiomental crease becomes deeper, while the cervicomental angle becomes more acute. Intraorally, the glossopharyngeal opening enlarges as the tongue is brought forward with the mandible. This can improve airway symptoms in patients with obstructive sleep apnea. Neither the nasolabial folds nor the velopharyngeal opening is affected with a mandibular advancement surgery.
A 30-year-old woman comes to the office to discuss surgical augmentation of the chin. Which of the following outcomes is most likely in this patient if a porous polyethylene prosthesis is used instead of a solid silicone rubber prosthesis?
A) Increased incidence of bone resorption
B) Increased incidence of infection
C) Increased ingrowth of tissue
D) Increased likelihood of malposition
E) Reduced resorption of the implant
The correct response is Option C.
Porous polyethylene implants have enough rigidity to resist soft-tissue deforming forces but enough flexibility to facilitate placement. The pore size (diameter of 100 to 250 ?m) of porous polyethylene used in facial augmentation procedures is sufficient to allow fibrous tissue ingrowth and relative incorporation of the prostheses. This avoids the capsule formation intrinsic to smooth-surface implants which is the result of the host’s foreign body response. This superficial tissue integration makes porous polyethylene facial prostheses less likely to migrate after implantation than solid silicone prostheses, but it also makes their explantation more difficult compared with solid silicone prostheses.
Silicone rubber has a smooth surface and is relatively flexible, making implant placement and removal beneath the soft-tissue envelope easier.
Neither porous polyethylene nor silicone prostheses are resorbed after implantation. Two recent studies reported on a total of 53 patients undergoing chin augmentation with silicone implants. The authors found 55% of those patients experienced underlying bone resorption during the 20 month follow-up period based on lateral radiographs.
A 33-year-old woman presents to the office for evaluation of facial pain. Physical examination shows that she has facial pain, temporomandibular joint clicking, and an anterior open bite. Which of the following is the most common physical examination finding of temporomandibular joint dysfunction?
A) Dental pain
B) Jaw deviation with mouth opening
C) Malocclusion
D) Masseter hypertrophy
E) Pain on palpation of the muscles of mastication
The correct response is Option E.
The most common age at presentation for temporomandibular disorder (TMD) is 20 to 40 years, and it is more common in women than men. Occlusal abnormalities, such as open bite, have not been shown to be a major cause of TMD, as is evidenced by the lack of response to occlusal correction therapy. Pain on palpation of the muscles of mastication is the most consistent clinical sign seen with TMD. Localized dental pain is not often a feature of TMD. Masseter hypertrophy is associated with bruxism.
A 22-year-old woman presents with long vertical facial height, narrow constricted alar bases, and lip incompetence. She has excessive gingival and upper incisor show at rest and while smiling. Which of the following is the most appropriate treatment for correction of the deformity?
A) Advancement genioplasty
B) Le Fort I osteotomy with impaction
C) Le Fort II osteotomy
D) Orthodontic manipulation
E) Sagittal split mandibular osteotomy
The correct response is Option B.
This patient presents with the classic physical finding of vertical maxillary excess, also known as long face syndrome. Patients will have long vertical facial height (especially in the lower third), narrow constricted alar bases, lip incompetence with an excessive interlabial gap, and excessive gingival and upper incisor show at rest and while smiling. They may also have a retruded and vertically long chin and a retrognathic mandible. Cephalometric analysis may show increased lower anterior facial height, SNA and SNB angles that are smaller than normal, and an ANB angle that is larger than normal (greater than 3 degrees).
The surgical treatment generally entails maxillary Le Fort I osteotomy with impaction. If there are mandibular discrepancies, then genioplasty and mandibular osteotomy may be needed. Le Fort II osteotomy would not address the vertical excess. Genioplasty alone, sagittal split mandibular osteotomy alone, and orthodontic manipulation alone would not address the vertical discrepancy.
A 25-year-old healthy man presents with a painful clicking when opening and closing his mouth 12 weeks after being involved in a physical altercation. He is able to chew and open and close his mouth normally, but with discomfort. Anteroposterior x-ray study shows no abnormalities. Which of the following is the most likely source of his discomfort?
A) Articular disc subluxation
B) Dynamic condylar subluxation
C) Early arthritis
D) Occult fracture of the condylar head
E) Spasm of the lateral pterygoid muscle
The correct response is Option A.
This patient likely has increased mobility of the articular disc. This can occur as a result of acute trauma (as in this case) or chronic trauma, such as bruxism. At this juncture, the disc is reducing with motion, so there is no obstruction to movement. Nevertheless, symptoms can worsen over time and create a closed-lock wherein the patient cannot open his mouth. An MRI and/or ultrasound can help confirm the pathology. With the limited and nonmechanical symptoms (eg, locking), treatment is conservative.
Arthritis is possible but unlikely in a patient of this age, especially without some other reason, such as infection or a history of juvenile rheumatoid arthritis. Fracture of the condylar head is possible, but this should have healed after 2 months and would be asymptomatic. Subluxation of the condylar head would restrict motion, and spasm of the lateral pterygoid can cause temporomandibular joint pain, but subluxation of the condylar head does not produce the click that is heard.
A 35-year-old woman is referred for evaluation of jaw pain. She reports a history of clicking and popping in her jaw particularly when chewing gum. She denies any history of trauma. Physical examination shows class I occlusion with a midline chin point. She has normal intra-oral opening. Which of the following diagnostic imaging techniques will provide the best sensitivity and specificity to evaluate her temporomandibular joint?
A) Arthrography
B) CT scan
C) Dynamic MRI
D) Fluoroscopy
E) Ultrasonography
The correct response is Option C.
This patient has subluxation of the disc causing her popping and subsequent pain. The study ordered must evaluate her for internal derangement of the disc related to the joint.
All of the listed imaging techniques have been used to evaluate temporomandibular joint (TMJ) disease. MRI is considered the gold standard for evaluation of the TMJ, particularly when evaluating the joint-disc relationship.
X-ray studies are indicated in the presence of trauma and would not provide the appropriate detail to determine the causes of this patient’s problems. CT scans are more sensitive and specific than conventional x-ray studies at determining bony abnormalities.
CT scan has a definite role in evaluation of patients with TMJ problems. CT scan should be enlisted when diagnosing bony abnormalities. It is useful in the diagnosis of ankylosis, osseous changes (e.g., idiopathic condylar resorption, or condylar hypoplasia seen in congenital anomalies such as Treacher Collins syndrome), or traumatic deformities. CT scan does not determine the location of the disc, so it would not be the appropriate imaging technique for this patient.
Arthrography is an invasive procedure and would not be performed for initial diagnosis. It can be combined with MRI to evaluate for adhesions or perforations.
Given its low cost and availability, ultrasonography of the TMJ has received increased attention in diagnosing internal derangement of the disc. Recent studies have reported a sensitivity of 65.8% and a specificity of 80.4% when compared with MRI. Ultrasonography was reported to be accurate in diagnosing normal disc position and the presence of abnormal disc-joint relationships but was less effective in evaluating disc displacement with or without reduction of the disc. Ultrasonography-guided arthrocentesis has been employed to decrease patient discomfort and multiple attempts to enter the joint space.
A 23-year-old woman seeks improvement in the appearance of her smile. A Le Fort I osteotomy is planned for correction of maxillary excess. Which of the following arteries is at increased risk for injury during this procedure?
A) Ascending pharyngeal artery
B) Descending palatine artery
C) Infraorbital artery
D) Posterior superior alveolar artery
E) Sphenopalatine artery
The correct response is Option B.
The blood supply to the maxilla before Le Fort I osteotomy is from the descending palatine, infraorbital, and posterior superior alveolar arteries, which are branches of the internal maxillary artery off the external carotid artery. When performing a Le Fort I osteotomy, the descending palatine artery runs vertically in the posterior maxilla and is at risk of injury.
After Le Fort I osteotomy, the blood supply to the maxilla is from the ascending palatine artery, which is a branch of the facial artery, off the external carotid artery and the palatine branch of the ascending pharyngeal artery, off the external carotid artery.
Which of the following best describes the normative percentage of the lower third of the face from subnasal to menton when compared to the upper face and mid face?
A) 10%
B) 20%
C) 30%
D) 40%
E) 50%
Please note: Upon further review, this item was not scored as part of the examination.
The correct response is Option C.
The face may be divided into horizontal thirds. The upper third extends from the hairline to the glabella, the middle third from the glabella to the subnasale and the lower third from the subnasale to the menton. These facial thirds are rarely equal. If proportions are to be used in orthodontic/orthognathic surgical planning, they should be used only as general guidelines alongside other well-established treatment planning methods.
During genioglossus advancement, which of the following nerves innervates the affected muscle?
A) Facial nerve
B) Glossopharyngeal nerve
C) Hypoglossal nerve
D) Lingual nerve
E) Vagus nerve
The correct response is Option C.
During genioplasty or horizontal osteotomy of the mandible, the genioglossus muscle is identified after down fracture and separation of the mobile and nonmobile segments. The genioglossus muscle is not only a source of blood supply but also acts to advance the tongue during skeletal sleep apnea surgery and contributes to posterior pull on potential relapse of the mobilized chin segment. This important muscle is innervated by the hypoglossal nerve.
During a Le Fort I osteotomy, the descending palatine artery is disrupted and ligated. The blood supply to the mobilized maxilla is primarily from which of the following arteries?
A) Ascending pharyngeal
B) Greater palatine
C) Internal maxillary
D) Lesser palatine
The correct response is Option A.
The vascular supply of the Le Fort I osteotomy segment was studied by utilizing standard latex injection techniques. Anatomic dissections of 10 fresh cadavers demonstrated interruption of the descending palatine arteries with preservation of the ascending palatine branch of the facial artery and the anterior branch of the ascending pharyngeal artery within the attached posterior palatal soft-tissue pedicle in all specimens following Le Fort I maxillary osteotomy. These ascending arterial branches entered the soft palate at a position approximately 1 cm posterior to the pterygomaxillary junction, which was disrupted during the Le Fort I maxillary osteotomy. Separate ink injections of total maxillary osteotomy segments confirmed vascular perfusion of the ipsilateral hemimaxillary segment by the ascending palatine artery. Thus vascular supply of the mobilized Le Fort I maxillary segment is by means of the ascending palatine branch of the facial artery and the anterior branch of the ascending pharyngeal artery in addition to the rich mucosal alveolar anastomotic network overlying the maxilla.
Which of the following findings is most common in patients with vertical maxillary excess?
A) Counterclockwise rotation of the mandible
B) Excessive height in the upper half of the face
C) Mentalis strain
D) Posterior open bite
E) Retrusive midface
The correct response is Option C.
Vertical maxillary excess (VME), or long face syndrome, occurs when there is excessive (imbalanced) anterior facial height in the lower half of the face. The midface is relatively protrusive. Excessive eruption of the posterior dentition in the maxilla can cause clockwise rotation of the mandible. There is lip incompetence, excessive gingival show, and an effort to close the lips can result in mentalis strain. It is associated with an anterior open bite.
Which of the following is the best method to treat maxillary transverse deficiency in a skeletally mature patient?
A) Mandibular setback (bilateral sagittal split osteotomy)
B) Maxillary advancement (Le Fort I advancement)
C) Orthopedic and orthodontic expansion
D) Reverse-pull headgear
E) Surgically assisted rapid palatal expansion
The correct response is Option E.
Maxillary transverse deficiency (MTD) in the skeletally mature patient is best addressed with surgically assisted rapid palatal expansion (SARPE). In the young patient (before suture closure), orthopedic and orthodontic forces can be more easily used to correct the MTD.
Reverse-pull headgear does not aid in expansion in the skeletally mature patient.
One-piece Le Fort and bilateral sagittal split osteotomy (BSSO) procedures address anterior-posterior discrepancies rather than transverse deficiencies.
In a patient undergoing orthognathic surgery with preoperative class III malocclusion, which of the following anatomic relationships must be retained in order to optimize postoperative occlusion?
A) Centric relation and centric occlusion
B) Condylar seating
C) Maximal intercuspation
D) 2 mm of overbite
E) 2 mm of overbite and 2 mm of overjet
The correct response is Option A.
Centric occlusion is incorrect because centric occlusion (maximal intercuspation) without centric relation (condylar seating within the glenoid fossa) will not lead to reliable postoperative occlusion.
Maxillary occlusion plane angle is incorrect because the maxillary plane angle affects open bite tendency and is not a reliable measure of occlusion.
Gonial angle is incorrect because the gonial angle along with the mandible occlusal plane are better predictors of prognathism and open bite tendency and are not a reliable measure of occlusion.
Centric relation is incorrect because centric relation without centric occlusion will not lead to reliable postoperative occlusion.
Centric occlusion and centric relation is the correct response because maximal intercuspation (centric occlusion) coupled with proper mandible condylar position within the glenoid fossa (centric relation) is most likely to result in optimal occlusion after orthognathic surgery.
Which of the following terms best describes the temporomandibular joint?
A) Ellipsoid (condyloid)
B) Gliding (arthrodial)
C) Hinge-sliding (ginglymoarthrodial)
D) Pivot (trochoid)
E) Saddle (ephippial)
The correct response is Option C.
The temporomandibular joint is classified as a ginglymoarthrodial joint since it has both hinge and sliding components during jaw opening. These functions take place in the two separate compartments in the joint, upper and lower, that are effectively separated by an articular disc. During the first 20 mm of jaw opening, the condyle rotates in the lower compartment (space between condylar head and articular disc) in a nearly pure hinge motion. For further opening to take place, the condyle translates (or shifts) forward with the articular disc through the upper compartment (space between the articular disc and the joint surface). The other options describe other joint configurations. Examples of each are: saddle, thumb basilar joint; pivot, atlas-axis (C1-2 neck); gliding, tarsal bones in the foot; ellipsoid, radiocarpal articulation.
A 22-year-old woman comes to the office because she is unhappy with the appearance of the lower third of her face. On examination, she has a class II occlusion. Lateral cephalometric evaluation shows an SNA angle of 82 degrees (N 80-84), an SNB angle of 75 degrees (N 78-80), and an ANB angle of 7 degrees. Cranial base anatomy shows no abnormalities. Which of the following orthognathic procedures is most appropriate in this patient?
A) LeFort I maxillary advancement
B) LeFort I maxillary advancement with mandibular setback
C) Maxillary impaction
D) Sagittal split mandibular osteotomy with advancement
E) Sliding genioplasty
The correct response is Option D.
This patient has a skeletal class II deformity with a retrognathic mandible and normal maxillary projection. The SNA angle of 82 degrees (N 80-84) indicates a normally positioned maxilla relative to the cranial base, while the SNB angle of 75 degrees (N 78-80) indicates a retrognathic mandible relative to the cranial base. The ANB angle confirms the class II deformity (>4 degrees). A mandibular sagittal split osteotomy with advancement will correct this deformity.
Maxillary impaction is used to treat vertical maxillary excess.
LeFort I maxillary advancement will worsen this patient’s deformity.
Which of the following cephalometric landmarks is included in the Frankfort horizontal plane?
A) Nasion
B) Pogonion
C) Point B
D) Porion
E) Sella turcica
The correct response is Option D.
The two cephalometric planes used most frequently in lateral cephalograms to describe and evaluate the cranial base are the Sella-nasion plane and the Frankfort horizontal plane. The Frankfort horizontal plane is defined by a line from the superior edge of the external auditory meatus (porion) to the inferior orbital meatus (orbitale). The SNA and SNB are angles used to describe the position of the maxilla and mandible, respectively. The SN refers to a line from the sella turcica to the nasion, while point A is on the maxilla and point B is on the mandible. The pogonion refers to the chin point.
A 22-year-old woman comes to the office for evaluation of an abnormal bite. On physical examination, she has an anterior open bite, and the upper teeth are not exposed with the lips in repose. Cephalometric analysis shows a nasion (N) to anterior nasal spine (ANS) distance of 45 mm (N 52–57 mm), an ANS to menton (Me) distance of 63 mm (N 63–68 mm), and an N-ANS:ANS-Me ratio of 1:1.4 (N 1:1.2). All other measurements are within the reference ranges. Which of the following is the most appropriate surgical procedure for correction of this patient’s deformity?
A) Le Fort I maxillary osteotomy with downward repositioning
B) Le Fort II osteotomy with maxillary advancement
C) Naso-orbito-maxillary osteotomy
D) Perinasal osteotomy
E) Sagittal split osteotomy with mandibular setback
The correct response is Option A.
Le Fort I osteotomy with downward repositioning effectively lengthens the maxilla in cases of isolated vertical maxillary hypoplasia. The maxilla is repositioned vertically in its entirety or rotated downward, depending on whether or not the hypoplasia extends to the posterior maxilla. The goal is to close the anterior open bite and to restore facial height, allowing 3 to 4 mm of upper incisor to show with lips in repose.
Perinasal osteotomy is a procedure designed to lengthen the skeletal framework of the nose. It lengthens and increases nasal projection. It is therefore a suitable procedure for patients with nasomaxillary hypoplasia and a foreshortened nose, but with normal dental occlusion and facial height. It does not correct maxillary height or change the dental relationships.
Naso-orbito-maxillary osteotomy is a step beyond perinasal osteotomy, in that it corrects both the foreshortened and retruded nasal framework and maxillary hypoplasia horizontally and vertically. The entire osteotomized segment includes the central section of the maxilla from nasion to teeth, and from one internal orbital rim to the other. It can therefore close an anterior open bite when vertical maxillary insufficiency is a component of the deformity in addition to a retruded nasomaxillary complex. However, it would most likely shift the occlusion into class II if there were not also a horizontal deficiency of the maxilla. Therefore, it is not an appropriate procedure for the patient in the vignette because it would alter the naso-orbital region unnecessarily, and possibly cause a new deformity or abnormal relationship in this otherwise isolated vertical maxillary deficiency. The indications for a or a naso-orbito-maxillary osteotomy would overlap those for a Le Fort II osteotomy.
Le Fort II osteotomy is indicated for nasomaxillary hypoplasia with a recessed maxilla and class III malocclusion. This is frequently noted in patients with a history of cleft lip and palate. The same discussion used for the naso-orbito-maxillary osteotomy would apply here as well.
Sagittal split osteotomy is a procedure that modifies the mandible, permitting setback or advancement of the mandibular dentition when the cause of the malocclusion is mandibular hypoplasia or overdevelopment. It has no effect on the maxilla.
Which of the following is the most common cause of temporomandibular joint ankylosis?
A) Bruxism
B) Congenital anomaly
C) Infection
D) Radiation
E) Trauma
The correct response is Option E.
The most common cause of temporomandibular joint (TMJ) ankylosis is trauma. It usually occurs after untreated or inadequately treated mandibular fractures. Damage to the articular surface of the TMJ is the most common factor seen. In children, this can lead to growth disturbances ultimately requiring orthognathic surgery. Otherwise, joint replacement and repair may be indicated in adults. In the antibiotic era, infection is a rare cause. Congenital anomalies, bruxism, and radiation are less common.
A 16-year-old boy who successfully underwent Le Fort III advancement with bone grafting 6 years ago because of severe maxillomandibular disharmony comes to the office due to severe malocclusion. Physical examination shows an Angle class III malocclusion and severe mid face deficiency. Which of the following is the most likely explanation for the reappearance of this patient’s condition?
A) Age during original surgery
B) Discrepancy in the growth rate of the operated mid face and the mandible
C) Lack of bony stability in the first postoperative year
D) Poor follow-up
E) Poorly performed orthognathic surgery
The correct response is Option B.
A recent article showed for the first time that children who underwent Le Fort III advancement had recurrence of their initial pathology due to minimal mid face sagittal growth, but with normal mandibular growth. This study displayed this, despite excellent early advancement and bony stability up to 1 year. After 5 years, the lack of mid face growth ultimately relegates these patients to at least another advancement surgery. Definitive orthognathic surgery is required following the completion of skeletal growth to improve maxillomandibular relationships and to achieve optimal occlusion. In multiple studies, the average age of children undergoing Le Fort III osteotomies was close to age 6 years and age was not an independent factor for recidivism. Finally, studies of distraction after a Le Fort III osteotomy show better advancement and may help to minimize the recurrence of pathology.
A 16-year-old girl with facial asymmetry secondary to hemifacial microsomia comes to the office for evaluation of orthognathic surgery. Which of the following procedures puts her at the highest risk for perioperative bleeding?
A) Bilateral sagittal split osteotomy
B) Distraction osteogenesis
C) Le Fort I osteotomy
D) Mandibular vertical ramus osteotomy
E) Osseous genioplasty
The correct response is Option C.
Significant hemorrhage is uncommon in orthognathic surgery, but when it occurs, it is most likely secondary to the maxillary osteotomies. The vessels at risk with the maxillary osteotomy include the greater palatine vessels, maxillary artery, and pterygoid plexus. The incidence of significant hemorrhage with mandible osteotomies is rare. The vessels at risk include the inferior alveolar artery, facial artery, retromandibular vein, and the pterygoid venous vein. Distraction osteogenesis is associated with lower risk for bleeding than any of the open procedures.
A 41-year-old man comes to the emergency department because he is unable to close his mouth after yawning. He reports pain in the jaw. Which of the following is the most appropriate initial treatment?
A ) Arthroplasty
B ) Closed reduction during sedation
C ) Eminectomy
D ) Injection of botulinum toxin type A
E ) Intra-articular sclerosing
The correct response is Option B.
This patient has an acute anterior dislocation of his temporomandibular joint. Anterior dislocations are usually secondary to an interruption in the normal sequence of muscle action when the mouth closes from extreme opening. The masseter and temporalis muscles elevate the mandible before the lateral pterygoid muscle relaxes resulting in the mandibular condyle being pulled anterior to the bony eminence and out of the temporal fossa. Spasm of the masseter, temporalis, and pterygoid muscles causes trismus and keeps the condyle from returning into the glenoid fossa. Dislocations can be both unilateral and bilateral.
The most appropriate initial treatment is attempted closed reduction. Local anesthesia or sedation can help relax the muscles that are in spasm. Reduction involves downward and posterior movement of the mandible.
All other choices are options that have been tried with variable success to prevent chronic, recurrent temporomandibular joint dislocation. Arthroplasty or eminoplasty refers to augmentation of the articular eminence with a bone graft or an alloplastic material, or even titanium hardware. In contrast to the eminectomy, an eminoplasty seeks to confine the condyle to the glenoid fossa.
Eminectomy involves reducing or removing the articular eminence, which is the anterior wall of the glenoid fossa, surgically so that spontaneous reduction is possible.
Injection of botulinum toxin type A has been suggested as a treatment. The theoretic mechanism of action is relaxation of the masseter and temporalis muscles, allowing spontaneous reduction.
Intra-articular injection of a sclerosing agent, such as alcohol, usually followed by a period of interdental fixation has been described but has fallen out of favor due to lack of proven long-term efficacy. It was thought to be a noninvasive way of preventing the mandible from opening excessively wide and allowing dislocation of the condyle from the glenoid fossa by inducing fibrosis of the temporomandibular joint.
A 50-year-old man is evaluated for a 6-month history of clicking of the left temporomandibular joint and pain with joint movement. Physical examination shows an interincisal opening of 20 mm and recurrent locking in the open position; no signs of infection or ankylosis are noted. Which of the following is the most appropriate treatment?
A ) Botulinum toxin type A injection
B ) Intracapsular disk repositioning and reduction of the articular eminence
C ) Removal of disk and placement of an interpositional temporalis fascia flap
D ) Temporomandibular joint replacement
E ) Observation
The correct response is Option B.
Surgical reduction of the articular eminence is indicated for patients who have symptomatic open locking of the mandible. Surgical options for symptomatic patients and secondary functional limitations with internal joint abnormalities on MRI include: intracapsular disk repositioning; discectomy; and an interpositional temporalis fascia flap. Botulinum toxin type A is not an approved use in this clinical setting. Discectomy is appropriate as a salvage procedure. Temporomandibular joint replacement is rarely warranted unless signs of infection, as part of cancer resection, or severe ankylosis are noted. Conservative management is appropriate in cases with no functional abnormalities.
A 12-year-old girl is evaluated because of a 1-year history of progressive mandibular retrognathia and bilateral temporomandibular joint pain. There is no history of trauma. Examination shows slightly decreased interincisal opening without chin point deviation and an Angle class II malocclusion with an anterior open bite. Which of the following is the most likely cause of this patient?s symptoms?
A ) Bruxism
B ) Condylar hyperplasia
C ) Infection
D ) Myofascial pain syndrome
E ) Rheumatoid arthritis
The correct response is Option E.
Disorders that can affect the temporomandibular joint (TMJ) include ankylosis, arthritis, trauma, dislocation, congenital and developmental anomalies, and neoplasms. Rheumatoid arthritis (RA) can cause tenderness, swelling, and decreased motion in any joint, including the TMJ. The TMJ can be affected in up to 33% of patients with RA. Chronic inflammation can, eventually, result in articular erosions, joint destruction, and ankylosis. When RA develops in childhood or early adolescence (juvenile idiopathetic arthritis), erosion of the condyles can lead to progressive mandibular retrognathism and anterior open bite.
Bruxism is grinding of the teeth and can lead to progressive dental wear, myofascial pain, and TMJ derangement. It does not affect the facial profile. Condylar hyperplasia is overgrowth of the condyle. It is most commonly unilateral, painless, and can lead to chin point deviation. Infection can cause tenderness and, ultimately, degeneration of the TMJ. However, infection is rarely bilateral and there are usually concurrent systemic symptoms. Myofascial pain syndrome is a common cause of pain in the TMJ region. It is more common in girls and is considered a localized form of fibromyalgia in the head and neck. It usually is unilateral and does not typically lead to joint degeneration or alterations in occlusion.
A 7-year-old boy with Pfeiffer syndrome is brought to the office because of snoring that has worsened progressively for the past 6 months. Treatment with tonsillectomy and adenoidectomy failed to correct the obstruction. Physical examination shows moderate proptosis, Angle class III malocclusion, and inadequate malar projection. Nasendoscopy shows pharyngeal obstruction by the soft palate. Which of the following is the most appropriate management?
A ) Le Fort I osteotomy and advancement
B ) Le Fort II osteotomy and advancement
C ) Le Fort III osteotomy and advancement
D ) Mandibular setback with glossopexy and tongue-lip adhesion
E ) Mandibular setback with vertical ramus osteotomies
The correct response is Option C.
In a patient with Pfeiffer syndrome who is found to have worsening nasopharyngeal airway obstruction, mid face advancement is indicated to obviate a tracheostomy. Until the adult dentition has erupted, a Le Fort I osteotomy is contraindicated to avoid injuring the developing teeth in the maxilla. A Le Fort II osteotomy will fail to advance the deficient malar processes. A mandibular setback, by any means, will worsen the airway.
A 13-year-old boy who underwent repair of left unilateral cleft lip and palate is brought to the office because he is dissatisfied with his “underbite.” He reports no other symptoms. Cephalometric analysis shows an SNA angle of 76 degrees (N = 81 ± 3) and an SNB angle of 81 degrees (N = 79 ± 3). A negative overjet of 5 mm is noted. Which of the following is the most appropriate management?
A ) Bimaxillary advancement
B ) Le Fort I advancement of the maxilla with internal fixation
C ) Le Fort I osteotomy and distraction
D ) Mandibular setback
E ) Orthodontics and follow-up in 1 year
The correct response is Option E.
At 13 years of age, the facial skeletal growth is not complete. Therefore, the patient should wait until his facial skeletal growth is complete, usually at age 18 for boys. Meanwhile, he should follow up regularly with his craniofacial team. The Angle class III malocclusion is not uncommonly seen in patients after cleft palate repair. The scarring from bony dissection in the palate repair restricts maxillary growth. However, unless there are severe symptoms (such as respiratory compromise), the definitive orthognathic surgery is deferred until skeletal maturation. When skeletal maturation is complete, a Le Fort I osteotomy with immediate fixation, or distraction osteogenesis (DO), can be done. DO is reserved for those cases where the advancement is calculated to exceed 10 mm. His SNB angle is within normal limits, therefore a setback is not indicated, nor is bimaxillary surgery.
A 34-year-old woman comes to the office because she would like to improve the appearance of her face. She recently completed orthodontic therapy with lingual braces. When she smiles, no upper incisal show is noted. Occlusion is Angle class I. Which of the following is the most appropriate management?
A ) Cosmetic dental laminates
B ) Horizontal excision of the upper lip
C ) Mandibular osteotomy and advancement of the mandible with a genioplasty
D ) Maxillary osteotomy with vertical lengthening of the maxilla
E ) Vertical shortening of the upper lip using a scar hidden under the nostril
The correct response is Option D.
This case describes an adult with vertical maxillary deficiency resulting in inadequate upper incisal show. This is corrected with a maxillary osteotomy and vertical lengthening while maintaining the occlusive relationship. Excision of the upper lip is not the best solution of the patient described with vertical maxillary deficiency. A mandibular advancement should not be recommended as cephalometric evaluation is noted to be normal. Shortening the upper lip is not recommended for vertical maxillary deficiency.
An 18-year-old woman who underwent repair of unilateral cleft lip and palate in infancy comes to the office for consultation regarding facial aesthetics. Cephalometric analysis shows an SNA angle of 75 degrees (N 81.2), an SNB angle of 81 degrees (N 77.3), and an SNPg angle of 81 degrees (N 80). A negative overjet of 1.5 mm is noted. A photograph is shown. After orthodontic preparation, which of the following is the most appropriate surgical management?
A) Maxillary advancement
B) Maxillary advancement and mandibular setback
C) Maxillary advancement, mandibular setback, and advancement genioplasty
D) Maxillary setback
E) Maxillary setback, mandibular advancement, and advancement genioplasty
The correct response is Option C.
The cephalogram is a standardized x-ray study used for analyzing facial disharmony and asymmetry. Labeled landmarks help establish the relationship of the maxilla, mandible, and skull base to other facial structures. The sella (S) point marks the center of the hypophyseal fossa. The nasion (N) is the junction of the nasal and frontal bones at the most posterior point of the curve of the nose. Point ?A? marks the innermost curvature from the maxillary anterior nasal spine to the alveolar process. The angle created by these points (SNA) establishes the maxillary position in relation to the skull base. Point ?B? is located at the innermost curvature from the chin to the alveolar process of the mandible. The SNA angle similarly establishes the mandibular relationship to the skull base.
The prominence of the chin is often an important consideration in orthognathic surgery. The pogonion is the most anterior chin point. SNPg angle is representative of the degree of chin prominence relative to the cranial base (mandible position).
Normal angle values are given in the text. The patient described is in a dramatic Angle class III malocclusion. The SNA is less than normal, and the SNB is greater than normal. The chin position is appropriate. In order to establish a class I dental relationship, the maxilla must advance, and the mandible must be set back. Doing so will also move the chin back. Therefore, to maintain the preoperative chin position, a compensatory advancement genioplasty should also be performed.
A 19-year-old man comes to the office for evaluation of a large lower jaw. Physical examination shows an Angle class III malocclusion. Which of the following is the most likely finding on cephalometric evaluation?
A) ANB angle is more acute than normal
B) SNA angle is more obtuse than normal
C) SNB angle is more obtuse than normal
D) SNO angle is more acute than normal
The correct response is Option C.
In a patient with mandibular prognathism (ie, projecting mandible), the SNB angle is more likely to be larger or more obtuse than normal. On a lateral cephalogram, the SNB is formed by the angle drawn between the sella, nasion, and B point (supramentale) of the mandible.
The ANB angle describes the position of the mandible relative to the maxilla. In the scenario described, the ANB angle would be more acute than normal.
The SNA angle describes the sagittal position of the maxilla and would be expected to be normal in the patient described.
The SNO angle describes the relationship between the inferior orbital rim and the skull base.
An image is shown.
A 44-year-old man is referred by his pulmonologist for consultation regarding surgical management of obstructive sleep apnea. He is unable to tolerate treatment with continuous positive airway pressure. History includes septoplasty to correct a deviated nasal septum and uvulopalatopharyngoplasty 2 years ago. History also includes orthodontic treatment 30 years ago. Current examination shows a Class I molar relationship with normal overjet. Cephalometric analysis shows an SNA angle of 76.7 degrees (N 80), an SNB angle of 72.1 degrees (N 78), and a posterior airway space (PAS) of 4 mm (N 11.0 ± 1). Orthognathic surgery is planned. Which of the following is the most appropriate management?
A) Mandibular advancement
B) Maxillary advancement
C) Maxillary and mandibular advancement
D) Maxillary/palatal expansion
The correct response is Option C.
Options for management of obstructive sleep apnea (OSA) include medical and surgical modalities. The first line of treatment is continuous positive airway pressure. Surgical treatments are directed toward the level of pathology(ies); ie, nose, palate, or base of the tongue. The goal of orthognathic surgery in the treatment of OSA is the enlargement and decreased collapse of the velo-oropharyngeal airway through anterior displacement of the soft tissues and musculature. Orthognathic treatment in adult OSA patients generally involves maxillary and mandibular advancement. The amount of advancement is usually greater than 10 mm regardless of cephalometric analysis. Success rates seen with simultaneous large advancement of the maxilla and mandible are between 75 and 100%.
A 50-year-old man comes to the office because of a clicking sensation when he opens his mouth. He sustained injuries to the right side of his face 1 year ago when he was involved in a snowmobile collision. Evaluation at that time showed no evidence of a fracture. Current physical examination shows adequate range of motion of the mandible. Which of the following is the most likely cause of the condition described?
A) Blood within the temporomandibular joint capsule
B) Contact of the condylar head against the articular eminence
C) Contact of the mandibular condyle against the glenoid fossa
D) Foreign body in the temporomandibular joint
E) Subluxation of the articular disk
The correct response is Option E.
A “clicking sensation” upon opening the jaw is commonly caused by anterior subluxation of the articular disk. The temporomandibular joint is unique in that it is a diarthrodial joint, having one space above the disk and a second space below. Clicking occurs when the posterior attachments of the disk become attenuated or ruptured. The disk is then allowed to sublux anteriorly and then relocate. Patients with painless clicks may be observed; those with painful clicking during jaw closure require treatment. Conservative management consists of NSAID therapy, the use of a bite block, and aggressive physical therapy. More aggressive management includes surgery, which is reserved for those who fail conservative therapy. The other causes are much less likely.
Which of the following is the ideal amount of tooth show with the lips in repose?
A ) 2 mm of lower incisor show
B ) 4 mm of lower incisor show
C ) 2 mm of upper incisor show
D ) 4 mm of upper incisor show
E ) No tooth show
The correct response is Option C.
The ideal amount of tooth show with the lips in repose is 2 mm of the maxillary incisors. In women, up to 4 mm may be acceptable. However, more show of the upper dentition results in a gummy appearance. One possible etiology for a gummy appearance is vertical excess of the maxilla. Orthognathic surgery with maxillary impaction is the typical treatment for this deformity.
Over time, elongation of the upper lip decreases the amount of show of the upper dentition. Gravitational pull on the lower lip may result in the increased display of the mandibular dentition with advancing age. Techniques such as lip augmentation and lip lift are designed to correct these changes of aging.
An 18-year-old man undergoes Le Fort I advancement for correction of a 10-mm maxillomandibular discrepancy as a result of maxillary hypoplasia. Which of the following diagnoses places this patient at greatest risk for postoperative development of velopharyngeal incompetence?
A ) Apert syndrome
B ) Clefting of the lip and palate
C ) Craniofacial microsomia
D ) Mandibular prognathism
The correct response is Option B.
Substantial advancement of the maxilla in patients with mid face hypoplasia secondary to a repaired cleft of the lip and palate is a risk factor for the development of velopharyngeal incompetence. Key preoperative findings to evaluate the risk include nasal air emission, nasal resonance, borderline velopharyngeal incompetence, or a combination of findings. In patients with an Angle class III malocclusion due to mandibular prognathism, mandibular setback, rather than maxillary advancement, is the procedure of choice. This should not increase a patient €™s risk for development of velopharyngeal incompetence. Patients undergoing maxillary advancement for other craniofacial anomalies, such as craniofacial microsomia or Apert syndrome, are at lower risk for development of velopharyngeal incompetence.
A 4-year-old girl is undergoing mandibular reconstruction involving the temporomandibular joint. Use of which of the following types of bone graft is most likely to result in overgrowth on the reconstructed side?
A ) Calvaria
B ) Fibula
C ) Iliac crest
D ) Radius
E ) Rib
The correct response is Option E.
A variety of bone sources may be used in reconstructing the deficient mandible in pediatric patients. The majority of reconstructions are done for congenital anomalies involving the mandible, such as hemifacial microsomia and Treacher Collins syndrome. However, bone grafting may also be needed following tumor resection and traumatic loss.
Cortical bone may be harvested from the iliac crest, calvaria, rib, radius, and fibula. Typically, when rib bone is used to reconstruct the mandible, including the temporomandibular joint, a cartilaginous cap is left on the end of the rib when it is harvested. This allows for growth of the rib as the child grows, but it can also result in overgrowth. This overgrowth can result in further asymmetry and malocclusions.
Which of the following tooth root apexes is at greatest risk for damage during a Le Fort I osteotomy for maxillary advancement?
A ) Bicuspid
B ) Canine
C ) Central incisor
D ) First molar
E ) Lateral incisor
The correct response is Option B.
The canine tooth root is the longest root extending onto the maxillary wall near the piriform rim. The length of the canine tooth from the incisal edge to the root apex is approximately 30 mm. The root is at risk during both osteotomy and plating and serves as an important landmark in operative planning. The roots of central and lateral incisors and bicuspids and molars are at less risk because they have shorter roots. Crowns of the central and lateral incisors are at greater risk during disimpaction of the Le Fort I segment if the maxillary disimpaction forceps are not placed properly. With careful osteotomy planning, disimpaction and plating dental injury are infrequent occurrences.
A 30-year-old woman comes to the office because of a 1-year history of a clicking sensation when she opens her mouth. She was involved in a motor vehicle collision in which her face struck the steering wheel 1 year ago. Physical examination shows midline dental structures without deviation. Which of the following is the most likely cause of this patient’s condition?
A ) Disruption of the lateral pterygoid muscle
B ) Foreign body within the joint space
C ) Malunion of a coronoid fracture
D ) Nonunion of a condylar fracture
E ) Subluxation of the articular disk
The correct response is Option E.
Motion at the temporomandibular joint (TMJ) is best appreciated by placing one €™s fingers either inside the external auditory canal or just anterior to it. The sensation of clicking when the jaw is repeatedly opened and closed is usually caused by subluxation of the articular disk. The disk normally lies centrally between the two joint spaces. Conservative treatment involves adjustment of the patient €™s bite with a splint, anti-inflammatory drugs, and physical therapy. Surgical treatment is reserved for patients who fail conservative therapy. Air within the joint space may occur following open fractures of the mandibular condyle. The presence of a foreign body within the joint space produces pain and decreased range of motion rather than clicking. Similar symptoms are also noted in patients with degenerative disease affecting the TMJ.
An 18-year-old man is evaluated because of an overbite. Cephalometric analysis shows an SNA angle of 83 degrees (N 82 ± 3) and an SNB angle of 74 degrees (N 80 ± 3). Which of the following is the most likely underlying cause of this condition?
A ) Prognathic maxilla
B ) Retrognathic maxilla
C ) Prognathic mandible
D ) Retrognathic mandible
The correct response is Option D.
An €œoverbite € (Angle class II malocclusion) may be caused by several different etiologies: a prognathic maxilla, a retrognathic mandible, or both; even a prognathic mandible with a more severely prognathic maxilla, or a retrognathic maxilla with a more severely retrognathic mandible, is possible. The patient described is exhibiting isolated mandibular deficiency, or retrognathia, which is characterized by a decreased sella-nasion-point B (SNB) angle combined with a normal sella-nasion-point A (SNA) angle. The SNA and SNB angles determine the position of the maxilla and mandible relative to the cranial base. The SNA angle measures the position of point A (subspinale) relative to the anterior cranial base with the normal value being 82 degrees plus or minus 3 degrees. The SNA angle is increased in maxillary prognathism and decreased in maxillary retrognathism. The SNB angle measures the position of point B (supramentale) relative to the anterior cranial base with the normal value being 80 degrees plus or minus 3 degrees. The SNB angle is increased in mandibular prognathism and decreased in maxillary retrognathism.
A 40-year-old man is being evaluated because of lower dental show and occasional drooling since undergoing bilateral sagittal split mandibular osteotomy and genioplasty four years ago. Lip sensation is normal. A clinical photograph is shown. Which of the following is the most likely cause of these findings?
A ) Excessive downward repositioning of the genioplasty segment
B ) Failure to reapproximate the mentalis muscle to the mandible
C ) Injury to the buccal branch of the facial nerve
D ) Injury to the inferior alveolar nerve
E ) Injury to the marginal mandibular branch of the facial nerve
The correct response is Option B.
The patient shown has ptosis of the lower lip, caused by failure to reapproximate the mentalis muscle to the mandible during genioplasty. Ptosis of the soft tissues of the chin, including the lip, and excessive lower dental show are the result. If the depth of the labial sulcus is sufficiently reduced, drooling may occur.
Provided the mentalis muscle is repaired, and no nerve injury occurs, downward repositioning of the genioplasty segment should not produce excessive lower dental show.
The mentalis muscle is innervated by the marginal mandibular branch of the facial nerve, which could sustain a neurapraxic injury during either bilateral sagittal split osteotomy or genioplasty. However, that injury would be unlikely to persist for four years.
The buccal branch of the facial nerve innervates the buccinator and orbicularis oris muscles. Loss of orbicularis oris function could lead to lip ptosis, but injury to the buccal branch of the facial nerve would be very unlikely in the situation described.
Injury to the inferior alveolar nerve can occur with either bilateral sagittal split osteotomy or genioplasty. The resulting paresthesia or anesthesia of the lower lip may lead to drooling but would not cause dysfunction in the mentalis muscle or lip ptosis.
Which of the following best describes the occlusal relationship indicated by the arrow labeled B in the diagram shown?
A ) Crossbite
B ) Open bite
C ) Overbite
D ) Overjet
The correct response is Option D.
Overjet is the horizontal relationship between the maxillary and mandibular incisors shown in the diagram. Crossbite describes a reverse relationship between the maxillary and mandibular teeth, either
sagittally or buccolingually. Open bite refers to the lack of vertical overlap by the maxillary teeth over the mandibular teeth. Overbite is the vertical overlap between the maxillary and mandibular incisors.
A 38-year-old woman is referred to the office by an orthodontist for orthognathic surgery to correct facial disharmony. The following angles are noted on cephalometric analysis:
SNA 80 degrees (N 81.2)
SNB 76 degrees (N 77.3)
SN-Pogonion 70 degrees (N 80)
Which of the following is the most appropriate surgical procedure?
A ) Advancement genioplasty
B ) Le Fort I advancement and advancement genioplasty
C ) Le Fort I advancement and setback genioplasty
D ) Sagittal split mandibular advancement
E ) Sagittal split mandibular setback
The correct response is Option A.
The cephalogram is a standardized radiograph used for analyzing facial disharmony and asymmetry. Labeled landmarks help establish the relationship of the maxilla, mandible, and skull base to other facial structures. The sella (S) point marks the center of the hypophyseal fossa. The nasion (N) is the junction of the nasal and frontal bones at the most posterior point of the curve of the nose. The A point marks the innermost curvature from the maxillary anterior nasal spine to the alveolar process. The angle created by these points (sella-nasion angle, SNA) establishes the maxillary position in relation to the skull base. The B point is located at the innermost curvature from the chin to the alveolar process of the mandible. The SNA angle similarly establishes the mandibular relationship to the skull base.
The prominence of the chin is often an important consideration in orthognathic surgery. The pogonion (Pg) is the most anterior chin point. The sella-nasion-pogonion (SNPg) angle is representative of the degree of chin prominence relative to the SNB (mandible position).
Normal angle values are given in the scenario. The patient described has a relatively retrusive pogonion and a normally positioned mandible/maxilla. This would represent a class I dental relation. The pogonion is posteriorly displaced in relation to both the mandible and the maxilla.
Therefore, to establish better facial relationships, the chin prominence should be advanced via a sliding genioplasty. The mandible does not need to move.
Which of the following is the most important clinical measurement when planning vertical maxillary changes?
A ) Gingival exposure with smiling
B ) Upper incisor exposure with the lips in repose
C ) Upper incisor exposure with smiling
D ) Vermilion exposure with the lips in repose
The correct response is Option B.
Upper incisor exposure with the lips relaxed is the key measurement when planning surgical vertical changes of the maxilla, aiming for a range of 3 to 5 mm. Males typically show less than females. Aging also results in a progressive decrease in upper incisor display. Normally, 100% of maxillary incisor is displayed on smile, but this relationship can be quite variable. Using relationships during smiling to determine surgical movements may result in unfavorable lip-tooth aesthetics at rest.
An 18-year-old woman is referred for evaluation of lower facial asymmetry. Examination shows the mandibular dental midline 6 mm to the left of the midsagittal plane, and the chin point and maxilla are coincident with the midsagittal plane. Which of the following procedures is most appropriate to correct the lower facial asymmetry?
(A) Le Fort I osteotomy with midline shift to the left and mandibular sagittal osteotomy with shift to the right
(B) Mandibular sagittal osteotomy with midline shift to the left
(C) Mandibular sagittal osteotomy with midline shift to the right
(D) Mandibular sagittal osteotomy with midline shift to the left and sliding genioplasty to the right
(E) Mandibular sagittal osteotomy with midline shift to the right and sliding genioplasty to the left
The correct response is Option E.
In assessing the orthognathic patient preoperatively, it is important to recognize all asymmetries and to be aware of potential asymmetries that may result from planned procedures. Combined osteotomies of the mandible and chin are indicated to bring the mandibular dental midline and the bony chin midline in line with the midsagittal plane in the patient described. To correct the jaw deformity, the mandibular dental midline would have to move to the right. The chin point would also move to the right and would therefore require an osteotomy and left shift.
Combining a Le Fort I and mandibular sagittal osteotomies would result in coincident dental midlines, but neither would be aligned with the midsagittal plane.
Correcting the dental midline alone with mandibular sagittal osteotomies would create a genial asymmetry that was not present preoperatively.
Which of the following reference points are used in cephalometric analysis of the mandible?
(A) Glabella and subnasale
(B) Nasion and pogonion
(C) Orbitale and porion
(D) Orbitale and sella
(E) Sella and A point
The correct response is Option B.
€œNasion and pogonion € is the only option that has at least one point of reference on the mandible. A line drawn between the nasion and pogonion may be referred to as the facial axis plane, and it may be related to any of several other intersecting lines, such as the Frankfort horizontal (orbitale to porion) line, to evaluate the mandible. The sella, A point, and palatal plane are used to evaluate the position of the maxilla.
A 17-year-old girl with Marfan syndrome comes to the office for an orthognathic evaluation. Intraoral examination shows a bilateral posterior lingual crossbite. Which of the following is the most appropriate management?
(A) Le Fort I osteotomy with palatal expansion
(B) Le Fort I osteotomy with palatal narrowing
(C) Mandibular osteotomy with narrowing
(D) Mandibular osteotomy with widening
The correct response is Option A.
Patients with Marfan syndrome typically have a high-arched and narrow palate resulting in a transversely constricted maxilla. Le Fort I osteotomy with palatal expansion is an appropriate surgical option for correcting the skeletal facial disharmony in the patient described.
Palatal narrowing would further worsen the skeletal problem.
Mandibular osteotomies are rarely performed to correct malocclusions based in the maxilla. However, if performed, they would generally be applied to narrow the mandible anteriorly.
A 26 year old woman comes to the office because she has had difficulty opening her mouth fully for the past three months. She says she has had €œpopping and clicking € in the temporomandibular joints (TMJs) with pain of varying severity for more than five years. Which of the following is the most likely cause of the internal derangement of the TMJs?
(A) Anterior dislocation with perforation
(B) Anterior dislocation with reduction
(C) Anterior dislocation without perforation
(D) Anterior dislocation without reduction
The correct response is Option D.
The patient has an anterior dislocation without reduction. €œPopping and clicking € in the TMJs are due to an anterior relationship of the articular disc to the mandibular condyle. A reducible disc is associated with essentially normal range of motion as translation is allowed to occur. A nonreducible disc maintains an anterior position and does not allow translation to occur fully. Thus, hypomobility of the mandible results.
An 18 year old man is undergoing presurgical orthodontic therapy for a dentofacial skeletal deformity. A current photograph is shown. Orthognathic surgery is planned. Repositioning of the maxilla during this procedure may result in each of the following changes EXCEPT
(A) cephalic rotation of the nasal tip
(B) decreased width of the nasal alar base
(C) flattening of the upper lip
(D) obstruction of the nasal airway
(E) reduced exposure of the vermilion
The correct response is Option B.
The patient shown has vertical maxillary excess as well as mandibular retrognathia. Le Fort I osteotomy with vertical impaction of the maxilla is necessary. Superior repositioning of the maxilla may result in several undesirable changes in nasolabial aesthetics, including increased width of the nasal alar base. Decrease in the width of the nasal alar base will not result from this procedure. Other possible nasal changes include cephalic rotation and increased projection of the nasal tip, reduction in the nasolabial angle, as well as flattening and shortening of the upper lip with resultant loss of visible vermilion.
The Frankfort horizontal line is formed by connecting which of the following two points on a standard cephalogram?
(A) A point and B point
(B) B point and menton
(C) Nasion and porion
(D) Orbitale and porion
(E) Sella and orbitale
The correct response is Option D.
A line joining the porion and the orbitale forms the Frankfort horizontal line (see cephalogram below). The porion is the superior aspect of the external auditory meatus. The orbitale is the most inferior point around the orbital rim. The Frankfort horizontal line is used to determine other reference measurements in the facial skeleton, such as the facial plane angle. The A point is the most posterior point of the anterior surface of the maxilla. The B point is the most posterior point on the anterior surface of the mandible. The menton is the most inferior point on the lower border of the mandible. The nasion is the junction of the frontal bone and the nasal bones. The sella is the midportion of the sella turcica. Lines and angles other than the Frankfort horizontal line utilize these points to determine anomalous cranial skeletal structure.
A 13-year-old boy who underwent repair of bilateral cleft lip at 3 months of age and repair of cleft palate at 9 months of age is being evaluated after alveolar bone grafting. He has undergone orthodontic treatment, but a 12-mm negative overjet remains. A photograph is shown. Which of the following operative procedures is most appropriate?
(A) Le Fort I osteotomy with distraction
(B) Le Fort I osteotomy with immediate advancement
(C) Le Fort III osteotomy with distraction
(D) Le Fort II osteotomy with immediate advancement
The correct response is Option A.
This patient has severe maxillary retrusion associated with bilateral cleft lip and palate. He has undergone bone grafting and orthodontic treatment, and his deformity is at the Le Fort I level, involving the tooth-bearing maxilla. Distraction osteogenesis at the Le Fort I level has become the mainstay for managing severe maxillary retrusion associated with cleft lip and palate. Before the advent of distraction, traditional Le Fort I advancement would give inadequate advancement due to palatal scarring, and many surgeons simultaneously performed mandibular setbacks to obtain class I occlusion at the expense of facial aesthetics. With distraction, significant advancements can be accomplished. If the osteotomy is performed at the Le Fort III level, vertical elongation of the orbit and resultant enophthalmos occur.
Le Fort I osteotomy is performed through which of the following structures?
(A) Lateral orbital wall
(B) Maxillary sinus
(C) Medial orbital walls
(D) Nasofrontal junction
(E) Orbital floor
The correct response is Option B.
The Le Fort classification is used to identify the pattern of midface fractures. Identification of the lines of fracture is useful in planning osteotomies for patients requiring midface advancement.
Le Fort I midface advancement involves placement of the osteotomy at a level above the apices of the teeth. The entire alveolar processes of the maxilla, vault of the palate, and pterygoid processes are included in a single block. The osteotomy extends transversely across the base of the maxillary sinus and the floor of the piriform aperture.
The Le Fort II osteotomy begins above the level of the apices of the teeth laterally and extends through the pterygoid plates in a manner similar to the Le Fort I osteotomy, leaving a central maxillary segment undisturbed. The osteotomy procedure includes portions of the medial orbital walls, orbital floor, and nasofrontal junction. Patients undergoing Le Fort II midface advancement are at increased risk for injury to the ethmoid area and the lacrimal system. The lateral orbital wall is unaffected.
Le Fort III osteotomy extends through the zygomaticofrontal suture and the nasofrontal suture and across the orbital floor. The entire midface is completely detached from the base of the skull.
Alloplastic chin augmentation is most appropriate for a patient with which of the following findings?
The correct response is Option D.
Because the indications for alloplastic chin augmentation are limited, the surgeon should carefully consider the skeletal deficiencies of each patient before considering this procedure. Alloplastic augmentation is most appropriate for a patient who has a minimal sagittal deficiency of the lower face, a shallow labiomental fold, and symmetry and normal height of the lower face.
Alloplastic chin implants are not appropriate for patients with chin asymmetry. Because a chin implant is always placed over the anterior symphysis, it cannot be used to correct abnormalities in facial height. Chin implantation will further accentuate any preexisting deep labiomental folds, resulting in an unnatural, “operated” appearance. Osseous genioplasties are more appropriate instead in those patients who require adjustments in the height of the lower face, or in patients who have a deep labiomental fold and require genial advancement. The vertical height of the chin can be elongated during advancement of the chin to prevent further deepening of the labiomental fold.
