Orthognathic, TMJ, Chin Flashcards
Which of the following is the most common etiology of ankylosis of the temporomandibular joint?
(A) Autoimmune
(B) Congenital
(C) Infectious
(D) Neoplastic
(E) Trauma
The correct response is Option E.
Intra-articular (true) ankylosis of the temporomandibular joint (TMJ) most frequently occurs as a result of trauma. In patients with true ankylosis, destruction of the articular disk and joint elements occurs, leading to fibrosis, narrowing of the joint space, and ultimately bony fusion.
Abnormalities of bone, cartilage, and/or soft tissue have also been shown to cause TMJ ankylosis.
Other causes of TMJ ankylosis, such as congenital abnormalities, idiopathic occurrences, infection, and juvenile rheumatoid arthritis, have been documented but are less common than trauma. Neoplasms of the TMJ are extremely rare.
In a 20-year old man, examination of the occlusion shows that the mesial buccal cusp of the maxillary first molar articulates between the first and second mandibular molars. Cephalometric analysis shows SNA angle of 70 degrees (normal 80 to 82 degrees) and SNB angle of 79 degrees (normal 79 to 80 degrees). Which of the following is the most likely diagnosis?
(A) Long face syndrome
(B) Maxillary deficiency
(C) Maxillary excess
(D) Retrognathia
(E) True prognathism
The correct response is Option B.
In a Class III mesioclusion, the mesial buccal cusp of the maxillary first molar articulates between the first and second mandibular molars. The mandible is mesially placed or prognathic compared to the maxilla. This type of malocclusion may result from maxillary deficiency, mandibular overgrowth, or a combination of both.
Long face syndrome results from vertical maxillary excess. Physical findings include excessive gingival and upper incisor show at rest and during smiling, a long vertical face, and a retrognathic mandible caused by backward autorotation or true retrognathism.
At rest, normal incisor show is approximately 2 to 3 mm. Decreased incisor show usually indicates maxillary hypoplasia. Excessive gingival show indicates excess maxillary growth.
This patient has a normal SNB angle, indicating that he does not have true prognathism but that it only appears excessive because the maxilla is retrusive. The SNA angle (normally 82 degrees) relates the maxilla to the cranial base. The SNB angle (normally 79 degrees) relates the mandible to the cranial base.
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.
Which of the following is the optimal amount of incisor show at rest?
(A) 0 to 1 mm
(B) 2 to 3 mm
(C) 4 to 5 mm
(D) 6 to 7 mm
The correct response is Option B.
At rest, the upper lips should be parted slightly and 2 to 3 mm of upper central incisors should be visible beneath the lower border of the upper lip. Only 1 to 2 mm of gingiva should be visible during a full smile. Patients with vertical maxillary deficiency typically have no incisor show at rest, resulting in a “prematurely aged” appearance. Patients with vertical maxillary excess often exhibit a “gummy” smile that occurs as a result of excessive gingival show.
Which of the following sites is osteotomized in the Le Fort III osteotomy but NOT in the monobloc advancement osteotomy?
(A) Frontozygomatic suture
(B) Inferior orbital fissure
(C) Lamina papyracea
(D) Pterygomaxillary fissure
(E) Zygomatic arch
The correct response is Option A.
Although the Le Fort III osteotomy, as shown in the first illustration on page 36, is most often used for correction of midface hypoplasia in patients with craniosynostosis, the monobloc advancement osteotomy is now gaining acceptance. In the Le Fort III procedure, the osteotomies pass through the nasofrontal junction first, then laterally across the medial orbital wall (lamina papyracea) and onto the orbital floor, continuing into the inferior orbital fissure. The lateral orbital wall is cut through the frontozygomatic suture and separated from the cranium; it continues inferiorly and posteriorly, where a pterygomaxillary disjunction is performed. After the zygomatic arch is cut, the advancement can be performed.
In the monobloc advancement, shown in the second illustration on page 36, the osteotomy lines are similar to the Le Fort III osteotomy, but the nasofrontal junction and frontozygomatic suture are not osteotomized. An advantage of the monobloc procedure is simultaneous correction of the supraorbital and midface deformities. However, this technique is associated with higher rates of infection and cerebrospinal fluid leakage, which is most likely due to direct communication between the cranial and nasal cavities.
In patients with Treacher Collins syndrome, which of the following is a characteristic skeletal finding?
(A) Brachycephaly
(B) Hypertelorism
(C) Macrogenia
(D) Malar hypoplasia
(E) Preaxial polysyndactyly
The correct response is Option D. The characteristic skeletal finding in patients with Treacher Collins syndrome is hypoplasia of the malar bones, which often occurs in conjunction with clefting through the zygomatic arches. Patients also have hypoplasia of the maxilla and mandible and antegonial notching of the angle of the mandible. Occlusion is Angle class II; there is an anterior open bite and clockwise rotation of the occlusal plane. Effects on the temporomandibular joint are varied.
Brachycephaly, macrogenia, preaxial polysyndactyly, and hypertelorism do not occur in patients with Treacher Collins syndrome.
In patients with vertical maxillary excess undergoing Le Fort osteotomy with maxillary impaction, which of the following findings is most likely postoperatively?
(A) Increased mentalis strain
(B) Increased upper incisal show
(C) More obtuse nasolabial angle
(D) Retrogenia
(E) Widened alar base
The correct response is Option E.
Patients with vertical maxillary excess, or long face syndrome, have a narrow alar base, an obtuse nasolabial angle, and an anterior open bite. Mentalis muscle strain and labial incompetence are increased, and there is excess gingival show and exposure of the upper incisors.
Appropriate management is Le Fort I osteotomy with maxillary impaction; osseous genioplasty is also performed in some patients. These procedures will correct many of the findings associated with this condition, including decreasing the mentalis muscle strain and incisal show and creating a more acute nasolabial angle. The alar base will be widened. Le Fort I osteotomy also rotates the mandible forward and upward, resolving the retrogenia associated with long face syndrome. Postoperative lateral cephalograms will show forward autorotation of the mandible with counterclockwise rotation.
The lateral cephalogram shown above is from a 16-year-old boy who desires occlusal correction. He underwent bilateral cleft lip and palate repair in infancy and pharyngeal flap transfer in early childhood. Examination shows Angle class III malocclusion with 12 mm of negative overjet; the SNB angle is within an acceptable range.
Which of the following is the most appropriate management?
(A) Le Fort I maxillary advancement
(B) Le Fort I maxillary advancement and genioplasty
(C) Maxillary distraction osteogenesis
(D) Maxillary and mandibular distraction osteogenesis
(E) Maxillary distraction osteogenesis and bilateral sagittal split-ramus osteotomy with mandibular setback
The correct response is Option C.
In patients who have severe deficiencies of the midface occurring secondary to cleft lip and palate, traditional orthognathic and orthodontic approaches are often ineffective. This patient with a bilateral cleft lip and palate has 12 mm of negative overjet following pharyngeal reconstruction with a posterior pharyngeal flap. These factors, as well as other complications seen in similar patients, including absence of maxillary and alveolar bone, scarring, and residual fistulas, can make reconstruction problematic and predispose these patients to surgical relapse. Therefore, newer procedures such as maxillary distraction osteogenesis are most appropriate for correction of the midface deficiency. This technique will expand the soft tissues and bones of the midface and palate in a single-stage procedure, correcting the malocclusion and leaving the mandible untouched.
Le Fort I maxillary advancement of more than 10 mm is a technically challenging, unpredictable procedure that would not correct this patient’s malocclusion. In addition, the posterior pharyngeal flap would have to be taken down before surgery, and a certain amount of relapse would be seen.
Although it is technically possible, a combined Le Fort I maxillary advancement and genioplasty procedure is not the first choice for this patient because the mandible and SNB angle are normal. For the same reason, mandibular distraction and/or setback are not necessary. Skeletal reduction procedures, such as the bilateral sagittal split-ramus osteotomy, are not recommended when maxillary distraction is available.
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.
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.
In a 30-year-old woman who is undergoing evaluation prior to orthognathic surgery, cephalometric analysis shows a decreased SNB angle and a normal SNA angle. These findings are most consistent with
(A) mandibular protrusion
(B) mandibular pseudoprognathism
(C) mandibular retrusion
(D) maxillary protrusion
(E) maxillary protrusion and mandibular retrusion
The correct response is Option C.
This patient’s findings are most consistent with mandibular retrusion, which is defined as a normal SNA (sella-nasion-point A) angle combined with a decreased SNB (sella-nasion-point B) angle on cephalometric analysis. The SNA angle measures the position of point A (anterior maxilla) relative to the anterior cranial base (SN); a normal SNA angle is defined as 82 degrees x 3 degrees. Patients with maxillary protrusion have an increased SNA angle, while patients with maxillary retrusion have a decreased SNA angle. In contrast, the SNB angle measures the position of point B (anterior mandible) relative to the anterior cranial base (SN); a normal SNB angle is defined as 80 degrees x 3 degrees. It is increased in patients with mandibular protrusion and decreased in patients with mandibular retrusion.
The Landes angle, which is formed by the Frankfort horizontal line and the nasion to point A (N-A) plane, is sometimes used instead of the SNA angle because of its greater reliability. A normal Landes angle is measured at 88 degrees x 3 degrees.
The ANB angle measures the position of point A to point B relative to the anterior cranial base; the angle is positive when point A lies anterior to point B. Patients with maxillary protrusion, mandibular protrusion, or a combination of both will have a markedly increased ANB angle. A decreased ANB angle can be seen in patients who have maxillary retrusion, mandibular protrusion, or a combination of both. In patients with mandibular pseudoprognathism, the ANB angle is normal.
Which of the following orthognathic movements is the most unstable and prone to relapse?
(A) Mandibular advancement
(B) Mandibular narrowing
(C) Maxillary advancement
(D) Maxillary widening
(E) Sliding genioplasty
The correct response is Option D.
Transverse widening of the maxilla is the most unstable orthognathic movement. With this procedure, a patient may lose as much as 50% of the movement at one year after surgery. Maxillary downgrafts and mandibular setbacks are also relatively unstable procedures. Mandibular advancement, mandibular narrowing, maxillary advancement, and sliding genioplasty are all considered stable movements.
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.
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.
In patients with vertical maxillary excess undergoing Le Fort osteotomy with maxillary impaction, which of the following findings is most likely postoperatively?
A) Increased mentalis strain
B) Increased upper incisal show
C) More obtuse nasolabial angle
D) Retrogenia
E) Widened alar base
Correct answer is E.
Patients with vertical maxillary excess, or long face syndrome, have a narrow alar base, an obtuse nasolabial angle, and an anterior open bite. Mentalis muscle strain and labial incompetence are increased, and there is excess gingival show and exposure of the upper incisors.
Appropriate management is Le Fort I osteotomy with maxillary impaction; osseous genioplasty is also performed in some patients. These procedures will correct many of the findings associated with this condition, including decreasing the mentalis muscle strain and incisal show and creating a more acute nasolabial angle. The alar base will be widened. Le Fort I osteotomy also rotates the mandible forward and upward, resolving the retrogenia associated with long face syndrome. Postoperative lateral cephalograms will show forward autorotation of the mandible with counterclockwise rotation.
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.
In a 5-year-old child, the optimal latency period for mandibular distraction is approximately how many weeks?
(A) 1
(B) 2
(C) 3
(D) 4
(E) 8
The correct response is Option A.
The latency period is defined as that time following the osteotomy procedure during which the cut bone surfaces begin to become bridged by initial fracture healing, just prior to initiation of distraction. Although recommendations regarding the optimal latency period for mandibular distraction have been controversial, current clinical protocols typically describe a latency period of five to seven days. However, some studies have questioned the necessity of a latency period. In experimental studies involving adult canines, premature consolidation of the tibial bone surfaces was noted following latency periods of either 14 days or 21 days. Because latency periods of 14 days or longer have been theorized to result in premature bony union, such lengthy periods are contraindicated in distraction osteogenesis. After active distraction is complete, the bone segments are held in rigid fixation until new bone mineralization occurs. This is known as the period of consolidation, which according to clinical protocols typically lasts for eight weeks.
A 16-year-old boy is scheduled to undergo maxillary advancement for correction of a 10-mm negative overjet of the maxillary incisors. Which of the following additional findings is associated with the greatest risk for the development of velopharyngeal incompetence?
(A) Class III malocclusion secondary to mandibular prognathism
(B) Maxillary-mandibular disharmony secondary to craniofacial microsomia
(C) Midface hypoplasia secondary to Crouzon syndrome
(D) Midface hypoplasia secondary to repaired cleft palate
The correct response is Option D.
Patients with midface hypoplasia secondary to repaired cleft palate are at increased risk for development of velopharyngeal incompetence, especially following maxillary (Le Fort I) advancement of greater than 10 mm. In a study of 70 patients who underwent Le Fort I advancement, the incidence of velopharyngeal incompetence was increased in those patients who had previously undergone cleft palate repair. This was particularly true in patients who, on preoperative examination, exhibited evidence of nasal air emission, nasal resonance, borderline velopharyngeal incompetence, or a combination of these findings.
In patients with Angle class III malocclusion secondary to mandibular prognathism, maxillary advancement is not the treatment of choice; instead, the skeletal anomaly is more appropriately addressed by performing mandibular setback. This procedure should not increase the patient’s risk for development of velopharyngeal incompetence.
Patients undergoing maxillary advancement for management of other conditions, such as craniofacial microsomia or Crouzon syndrome, are at much lower risk for development of velopharyngeal incompetence than those patients with a repaired cleft palate.
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.
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.
A 45-year-old woman with myofascial pain dysfunction has had pain in the preauricular region for the past six months. Plain radiographs of the temporomandibular joint are most likely to show which of the following?
(A) Anterior displacement of the disk
(B) Erosion of the anterior condyle
(C) Narrowing of the joint space
(D) Osteophytes of the condylar head
(E) No abnormalities
The correct response is Option E.
In myofascial pain dysfunction, radiographs show no abnormalities because the disorder does not usually produce discernible anatomic abnormalities in the temporomandibular joint (TMJ). Myofascial pain dysfunction is associated with preauricular pain, occasional joint clicking, restricted jaw opening, and tenderness of the masticatory muscles. Its causes are multifactorial and include bruxism, anxiety, and occlusal abnormalities. Anterior displacement of the disk of the TMJ cannot be identified on plain radiographs because the disk is composed of fibrous tissue, which can be seen only on radiographs with contrast.
Three weeks after undergoing bilateral maxillary advancement, a 28-year-old man has exposure of two of the four maxillary plates in the oral cavity. The maxilla appears stable. Which of the following is the most appropriate next step in management?
A) Instruction in oral hygiene and observation
B) Irrigation and debridement of the wound followed by replacement of the two exposed plates
C) Maxillomandibular fixation with heavy elastic for two weeks
D) Removal of all plates followed by intermaxillary fixation for six weeks
E) Removal of the two exposed plates only
Correct answer is A,
In this patient who has exposure of the internal hardware, the most appropriate management is maintenance of optimum oral hygiene. As long as oral hygiene is maintained, the oral mucosa is likely to granulate over the maxillary plates. After satisfactory bone healing has been achieved, any exposed plates can be removed.
Removal of the hardware is not indicated in a patient who underwent surgery only three weeks earlier because there is an increased risk of bony malunion. The maxilla is stable, and maxillomandibular fixation is unnecessary. The patient can continue nutrition with a soft diet without adverse sequelae.
A 16-year-old boy with history of cleft lip and palate comes to the clinic for management of malocclusion. Medical history includes several surgical procedures on the palate for closure of an oral nasal fistula. Intraoral evaluation shows Class III malocclusion and 15-mm negative overjet. Lateral cephalometry shows decreased SNA angle with normal SNB angle. Which of the following surgical procedures is most appropriate for correction of this deformity?
(A) Mandibular setback
(B) Le Fort I osteotomy with bilateral sagittal split osteotomy of the mandible
(C) Le Fort I advancement by distraction osteogenesis
(D) Le Fort II advancement by distraction osteogenesis
(E) Le Fort III advancement by distraction osteogenesis
The correct response is Option C.
For this patient, the most appropriate surgical option is a Le Fort I advancement by distraction osteogenesis because he requires correction of the malocclusion and needs a large amount of movement. Le Fort I advancement can correct the malocclusion by moving the tooth-bearing segment of the maxilla. Distraction osteogenesis allows for large movement because it stretches the soft tissue envelope gradually to accommodate the bony framework. Also, this patient=s prior surgery probably has resulted in scarring of the soft tissue of the palate. Such scarring is also an indication for distraction, which gradually stretches the scars. In contrast, an immediate large advancement is likely to be limited by scarring.
In this patient, mandibular setback alone produces too large a movement to correct the malocclusion and risks posterior placement of the base of the tongue, which could narrow the airway. In addition, it would not be aesthetically pleasing. A mandibular setback could be used as an adjunct if it were not possible to obtain the needed advancement by moving the maxilla alone.
Because this patient’s nose, orbital rim, and malar prominences are in good position, a Le Fort II or Le Fort III advancement is not indicated.
A 16-year-old girl who has hypoplasia of the chin and a prominent hump on the nasal dorsum is scheduled to undergo rhinoplasty and osseous genioplasty. In this patient, nerve injury during osseous genioplasty is most likely to result in which of the following complications?
(A) Inability to depress the lower lip
(B) Inability to elevate the lower lip
(C) Numbness of the ipsilateral tongue
(D) Numbness of the lower lip
(E) Oral incompetence
The correct response is Option D.
This 16-year-old girl who is undergoing genioplasty is at greatest risk for injury to the mental nerve, which will result in numbness of the lower lip. The mental nerve is a sensory portion of the inferior alveolar nerve and is located distally. It should be routinely identified and preserved during surgery. Patients who have damage to the mental nerve, either from injury during genioplasty or an inferior alveolar nerve block, often inadvertently bite the lip because of the loss of sensation.
An inability to depress the lower lip during facial animation occurs as a result of injury to the facial nerve. Injury to branches of the facial nerve is most likely to result in an inability to depress or elevate the lower lip and oral incompetence. Injury to the lingual nerve would result in numbness of the tongue.
A 23-year-old woman undergoes Le Fort I osteotomy with impaction of the maxilla because of vertical maxillary excess. The final vertical position of the maxilla is most accurately determined using which of the following studies?
A) Assessment of maxillary lip-tooth relationship
B) Cephalometric analysis of the ANB angle
C) Cephalometric analysis of the SNA angle
D) Dental model surgery
E) Panorex radiography
Correct answer is A.
Assessment of the maxillary lip-tooth relationship is the most accurate study in determining the final vertical position of the maxilla. This assessment can be made on a cephalometric radiograph by performing a soft-tissue and skeletal analysis and prediction tracing. Intraoperative assessment of the amount of tooth show is also important in determining the final vertical position of the maxilla. Normally, the lip-tooth relationship is 2 to 3 mm of tooth show.
Cephalometric analysis of the ANB and SNA angles are skeletal measurements. The ANB angle relates the maxilla to the mandible in the horizontal plane. The SNA angle relates the maxilla to the base of the cranium in the horizontal plane. Neither measurement assesses the vertical position of the maxilla or the soft-tissue envelope.
A 20-year-old woman with juvenile rheumatoid arthritis has worsening occlusion two years after undergoing sagittal split osteotomy with mandibular advancement. On examination, there is a loss of posterior facial height bilaterally and an anterior open bite. She has Angle class II malocclusion. Serial cephalometric analysis shows progressive posterior movement of the B point. Which of the following is the most likely cause of the worsening occlusion?
(A) Continued growth of the maxilla
(B) Improper intraoperative seating of the condyles in the glenoid fossae
(C) Improper preoperative and postoperative orthodontic treatment
(D) Loosening of all of the plates of the rigid internal fixation
(E) Progressive condylar resorption
The correct response is Option E.
Progressive condylar resorption is a late cause of open bite that occurs mainly in young women. It is associated with condylar shortening, a decrease in posterior facial height, clockwise rotation of the mandible, and Angle class II malocclusion. Slow progressive posterior movement of the point B on serial cephalometric analysis is a classic finding. The exact cause of the problem is unknown.
Poor orthodontic treatment can result in a recurrence of malocclusion in the postoperative period. However, the patient described above exhibits many of the classic findings of progressive condylar resorption, making that a more likely diagnosis.
The most likely cause of immediate postoperative open bite is improper seating of the condyles in the glenoid fossae during surgery. It is important to take the patient out of intermaxillary fixation after fixation of the osteotomies is completed to ensure that the condyles are properly seated. During this process, the occlusion and path of the opening of the mandible are checked. In a skeletally mature female, continued growth of the maxilla would be unusual. Lastly, it would be unusual for all of the plates of the rigid internal fixation to loosen.
A 10-year-old boy is scheduled to undergo Le Fort III osteotomy with distraction osteogenesis for advancement of the midface. Which of the following is an advantage of using a rigid external distraction device rather than an internal distraction device in this patient?
(A) Decreased operative morbidity
(B) Decreased risk for relapse following midface advancement
(C) Greater degree of advancement
(D) More rapid rates of distraction
(E) Need for fewer subsequent operative procedures
The correct response is Option E.
Distraction osteogenesis with external or internal distraction devices can be performed to lengthen the midface gradually in children with craniosynostosis, cleft lip and palate, hemifacial microsomia, and midface hypoplasia. Midface osteotomies must be performed in order to initiate distraction regardless of the type of device. The rigid external distraction (RED) device is most commonly used externally. Distraction with this device, rather than with an internally implanted device, is advantageous primarily because it can be removed in the office and a second operative procedure is not necessary. In contrast, an additional operative procedure is required in a patient who has an implanted internal device to expose and remove the hardware. Resorbable internal devices have been introduced recently, which may decrease the extent of operative dissection required for removal. However, a second operative procedure is still necessary to remove the metallic distraction foot plate attached to the resorbable hardware.
There are no differences in the degree of operative morbidity at the time of osteotomy with either the internal or external distraction device. However, operative morbidity following midface osteotomy for distraction osteogenesis is lower than that seen with midface osteotomy using conventional bone grafting and rigid fixation techniques. Distraction techniques using either internal or external devices do not have the potential for morbidity associated with bone graft harvest sites.
The potential for relapse of the advanced midface segment is no different with either technique following removal of the distraction device and an adequate period of consolidation.
There are no data to indicate that the results achieved with either type of device differ substantially. There is also no difference in the rate of distraction or the amount of distraction that can be achieved with either technique. Both techniques require a period of bone consolidation after distraction has been completed.
Which of the following is the most common complication of sagittal split osteotomy?
(A) Avascular necrosis of the proximal segment
(B) Injury to the mandibular molars
(C) Loss of lower lip sensibility
(D) Nonunion of the osteotomy site
(E) Relapse from incorrect positioning of the condyles at surgery
The correct response is Option C.
The most common complication of sagittal split osteotomy is loss of lower lip sensibility. Studies have shown a significant incidence of both temporary and permanent disruption of sensibility in the lower lip following this procedure.
Sagittal split osteotomy involves only minimal muscle stripping on the lateral aspect of the mandible. The blood supply to the proximal bony segment is adequate, and the incidence of avascular necrosis is minimal.
Because the roots of the mandibular molars are closer to the lingual cortex than to the buccal cortex, they are not typically injured during osteotomy.
Nonunion is an extremely rare complication of sagittal split osteotomy.
During the osteotomy procedure, the proximal segment and condyle are seated gently into the fossa, and the surgeon takes great care to avoid displacing the condyle anteriorly and downward on the temporal bone. As a result, relapse from incorrect positioning occurs only rarely.
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.
A 22-year-old man desires aesthetic enhancement of the chin. Examination of the chin shows horizontal (sagittal) deficiency and vertical excess. Which of the following surgical procedures should be performed in this patient?
(A) Alloplastic chin augmentation
(B) Interpositional genioplasty
(C) Jumping genioplasty
(D) Reduction genioplasty
The correct response is Option C.
A jumping genioplasty can performed to correct both horizontal (sagittal) deficiency and vertical excess. Preoperative evaluation of patients with chin abnormalities should involve analysis of the horizontal and vertical (ie, superoinferior) dimensions; chin symmetry should also be noted. Patients can have a combination of deficiency and/or excess in both the horizontal and vertical dimensions. In order to correct the findings seen in this patient, horizontal osteotomy is performed first, and then the caudal mandibular osteotomized segment is placed in front of the mandible.
Alloplastic augmentation is typically reserved for older persons with minimal pure horizontal chin deficiencies, and osseous genioplasties are performed in younger patients with more pronounced anomalies. Interpositional genioplasty, which is indicated for correction of vertical deficiency alone, is accomplished by performing a horizontal osteotomy with interpositional grafting using bone or a bone substitute. Reduction genioplasty, which involves wedge ostectomy followed by securing of the caudal segment to the mandible, is used for correction of vertical excess alone.
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.
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 37-year-old woman is undergoing evaluation because of intermittent clicking of the right temporomandibular joint (TMJ). She has no pain or crepitus of the joint. Interincisal opening is 40 mm. MRI shows a nonreducing articular disk within the right TMJ. Which of the following is the most appropriate management?
(A) Observation
(B) Intracapsular repositioning of the disk
(C) Intracapsular repositioning of the disk and reduction of the articular eminence
(D) Removal of the disk and placement of an interpositional temporalis fascia flap
The correct response is Option A.
Conservative management is most appropriate for this patient who has episodic clicking, no pain, and a normal interincisal opening distance. Operative correction is indicated only for internal derangement of the temporomandibular joint associated with congenital anomalies, neoplasia, previous trauma to the joint, chronic pain, or trismus resulting in functional limitation.
Intracapsular repositioning of the disk, removal of the disk, and placement of a temporalis fascia flap are options for those patients with internal derangement who are surgical candidates. Surgical reduction of the articular eminence, or eminectomy, is indicated in patients who have symptomatic open locking of the mandible.
Which of the following percentages best represents the incidence of paresthesia of the lower lip immediately after bilateral sagittal split osteotomy?
(A) 10%
(B) 30%
(C) 50%
(D) 70%
(E) 90%
The correct response is Option E.
Paresthesia of the lower lip is the most common immediate postoperative finding following a bilateral sagittal split osteotomy. It is generally bilateral and is due to neurapraxia resulting from stretch and compression of the inferior alveolar nerve as the mandible is mobilized and fixed into its new position. Studies have shown that the incidence of this finding ranges from 85% to 97% in the immediate postoperative period. In one study, 55% of the patients reported some degree of paresthesia at one month, which was further reduced to 12.5% at one year. The older the patient, the more protracted the sensory deficit.
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 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 12-year-old girl is scheduled to undergo surgically assisted maxillary expansion for correction of transverse maxillary deficiency. During this subtotal Le Fort I procedure, completion of each of the following osteotomies is appropriate EXCEPT
(A) lateral nasal walls bilaterally
(B) anterior and lateral antral walls bilaterally
(C) pterygoid plates bilaterally
(D) palatal midline
(E) nasal septum
The correct response is Option A.
Complete osteotomy of the thin lateral nasal walls is unnecessary. This structure offers little resistance to transverse expansion. Additionally, the lateral nasal walls help maintain the spatial relationship of the mobilized maxilla.
Completion osteotomies of the anterior antral walls, the lateral antral walls, and the pterygoid plates bilaterally as well as the midpalatal suture and the nasal septum are necessary for unhindered symmetric expansion of the maxillary halves.
A 20-year-old woman comes to the office for consultation regarding malocclusion. Cephalometric analysis shows SNA angle of 83 degrees (normal = 82 ± 3 degrees) and SNB angle of 85 degrees (normal = 80 ± 3 degrees). Which of the following is the most likely cause of this patient’s deformity?
A) Mandibular prognathism
B) Mandibular retrognathism
C) Maxillary retrusion
D) Retrogenia
E) Vertical maxillary excess
Correct answer is A.
A normal SNA (sella nasion point A) angle is defined as 82 ± 3 degrees and measures the position of point A (anterior maxilla) relative to the anterior cranial base (SN). A normal SNB (sella nasion point B) angle is defined as 80 ± 3 degrees and measures the position of point B (anterior mandible) relative to the cranial base (SN). The most common cause of a normal SNA with an increased SNB is mandibular prognathism. Mandibular retrognathism would have a normal SNA with a decreased SNB. Maxillary retrusion is associated with a decreased SNA and a normal SNB. Vertical maxillary excess alone would not change the SNB but describes a patient with long face syndrome.
A 20-year-old woman comes to the office for consultation regarding malocclusion. Cephalometric analysis shows SNA angle of 83 degrees (normal = 82 ± 3 degrees) and SNB angle of 85 degrees (normal = 80 ± 3 degrees). Which of the following is the most likely cause of this patient’s deformity?
(A) Mandibular prognathism
(B) Mandibular retrognathism
(C) Maxillary retrusion
(D) Retrogenia
(E) Vertical maxillary excess
The correct response is Option A.
A normal SNA (sella €‘nasion €‘point A) angle is defined as 82 ± 3 degrees and measures the position of point A (anterior maxilla) relative to the anterior cranial base (SN). A normal SNB (sella €‘nasion €‘point B) angle is defined as 80 ± 3 degrees and measures the position of point B (anterior mandible) relative to the cranial base (SN). The most common cause of a normal SNA with an increased SNB is mandibular prognathism. Mandibular retrognathism would have a normal SNA with a decreased SNB. Maxillary retrusion is associated with a decreased SNA and a normal SNB. Vertical maxillary excess alone would not change the SNB but describes a patient with long face syndrome.
The percentage of patients who have numbness in the distribution of the mental nerve one year after undergoing sagittal split osteotomy is closest to…
A) 0%
B) 10%
C) 30%
D) 60%
E) 80%
Correct answer is B.
According to the results of several studies, the risk for permanent damage to the inferior alveolar nerve during sagittal split osteotomy is 5% to 10%. The inferior alveolar nerve exits from the mental foramen to become the mental nerve, and the incidence of permanent sensory disturbance in the distribution of the mental nerve is similar to the incidence in the inferior alveolar nerve.
A 32-year-old man is undergoing evaluation because he has temporal headaches and a sensation of “sand in the jaw” when he eats. He sustained trauma to the face while playing football in college. On current physical examination, there is reciprocal clicking and transient locking of the jaw during opening and closing movements. MRI shows anterior malpositioning of the meniscus and posterosuperior displacement of the condyle.
These findings are most consistent with which of the following?
(A) Ankylosis of the temporomandibular joint
(B) Avascular necrosis of the condylar head of the mandible
(C) Dislocation of the temporomandibular joint
(D) Internal derangement of the temporomandibular joint
(E) Myofascial pain dysfunction syndrome
The correct response is Option D.
The findings in this patient are most consistent with internal derangement of the temporomandibular joint (TMJ), which is defined as an abnormal relationship between the articular disk and mandibular condyle. This condition is typically associated with anterior displacement of the meniscus and often with posterosuperior malpositioning of the condyle. The retromeniscal pad may be damaged and/or disrupted. Affected patients usually have preauricular pain and clicking of the joint, as well as other, less specific symptoms such as headache and aching pain in the ear or neck. A history of trauma or previous orthodontic treatment may be associated.
Ankylosis of the TMJ can result from trauma, infection, juvenile rheumatoid arthritis, or other conditions. In patients with TMJ ankylosis, destruction of the articular disk and joint elements occurs, resulting in fibrosis, narrowing of the joint space, and bony fusion.
Although avascular necrosis is rarely seen within the mandibular condyle, it may occur as a result of trauma or devascularization at the time of TMJ surgery. Affected patients have pain and limited jaw motion; MRI will show devascularization of the condyle.
Acute TMJ dislocation occurs following anterior extension of the condyle beyond the eminence; this condition occurs as a result of joint hypermobility secondary to either trauma or an excessively large mouth opening. Although spontaneous relocation typically follows, manual reduction under anesthesia may be required.
Patients with myofascial pain dysfunction have short, sudden episodes of aching pain in the jaw associated with stress; this condition is often referred to as masticatory muscle spasm secondary to bruxism. Malocclusion associated with long-term microtrauma to the joint (as seen in patients with bruxism) is thought to result in spasm of the lateral pterygoid or deep posterior masseter muscle, which is then further aggravated by episodes of anxiety and stress.
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.
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.
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.
A 16-year-old boy with history of cleft lip and palate comes to the clinic for management of malocclusion. Medical history includes several surgical procedures on the palate for closure of an oral nasal fistula. Intraoral evaluation shows Class III malocclusion and 15-mm negative overjet. Lateral cephalometry shows decreased SNA angle with normal SNB angle. Which of the following surgical procedures is most appropriate for correction of this deformity?
(A) Mandibular setback
(B) Le Fort I osteotomy with bilateral sagittal split osteotomy of the mandible
(C) Le Fort I advancement by distraction osteogenesis
(D) Le Fort II advancement by distraction osteogenesis
(E) Le Fort III advancement by distraction osteogenesis
The correct response is Option C.
For this patient, the most appropriate surgical option is a Le Fort I advancement by distraction osteogenesis because he requires correction of the malocclusion and needs a large amount of movement. Le Fort I advancement can correct the malocclusion by moving the tooth-bearing segment of the maxilla. Distraction osteogenesis allows for large movement because it stretches the soft tissue envelope gradually to accommodate the bony framework. Also, this patient=s prior surgery probably has resulted in scarring of the soft tissue of the palate. Such scarring is also an indication for distraction, which gradually stretches the scars. In contrast, an immediate large advancement is likely to be limited by scarring.
In this patient, mandibular setback alone produces too large a movement to correct the malocclusion and risks posterior placement of the base of the tongue, which could narrow the airway. In addition, it would not be aesthetically pleasing. A mandibular setback could be used as an adjunct if it were not possible to obtain the needed advancement by moving the maxilla alone.
Because this patient’s nose, orbital rim, and malar prominences are in good position, a Le Fort II or Le Fort III advancement is not indicated.
In an 18-year-old man with Angle class III malocclusion, cephalometric analysis shows a decreased SNA angle and a normal SNB angle. Which of the following is the most likely cause of these findings?
(A) Mandibular prognathism
(B) Mandibular retrognathism
(C) Maxillary retrusion
(D) Vertical maxillary excess
The correct response is Option C.
Maxillary retrusion is the most common cause of a decreased SNA (sella-nasion-point A) angle combined with a normal SNB (sella-nasion-point B) angle. The SNA angle measures the position of point A (anterior maxilla) relative to the anterior cranial base (SN); a normal SNA angle is defined as 82 degrees 3 degrees. Patients with maxillary protrusion have an increased SNA angle, while patients with maxillary retrusion have a decreased SNA angle. In contrast, the SNB angle measures the position of point B (anterior mandible) relative to the anterior cranial base (SN); a normal SNB angle is defined as 80 degrees 3 degrees. It is increased in patients with mandibular protrusion and decreased in patients with mandibular retrusion. This patient has Angle class III malocclusion, in which the mandible is abnormally protrusive relative to the maxilla, or the maxilla is retrusive relative to the mandible. This patient has a decreased SNA angle and a normal SNB angle, as stated above; therefore, the mandibular position is normal while the maxillary position is deficient.
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.
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.
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 12-year-old girl is scheduled to undergo surgically assisted maxillary expansion for correction of transverse maxillary deficiency. During this subtotal Le Fort I procedure, completion of each of the following osteotomies is appropriate EXCEPT
(A) lateral nasal walls bilaterally
(B) anterior and lateral antral walls bilaterally
(C) pterygoid plates bilaterally
(D) palatal midline
(E) nasal septum
The correct response is Option A.
Complete osteotomy of the thin lateral nasal walls is unnecessary. This structure offers little resistance to transverse expansion. Additionally, the lateral nasal walls help maintain the spatial relationship of the mobilized maxilla.
Completion osteotomies of the anterior antral walls, the lateral antral walls, and the pterygoid plates bilaterally as well as the midpalatal suture and the nasal septum are necessary for unhindered symmetric expansion of the maxillary halves.
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.
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.
The percentage of patients who have numbness in the distribution of the mental nerve one year after undergoing sagittal split osteotomy is closest to
(A) 0%
(B) 10%
(C) 30%
(D) 60%
(E) 80%
The correct response is Option B.
According to the results of several studies, the risk for permanent damage to the inferior alveolar nerve during sagittal split osteotomy is 5% to 10%. The inferior alveolar nerve exits from the mental foramen to become the mental nerve, and the incidence of permanent sensory disturbance in the distribution of the mental nerve is similar to the incidence in the inferior alveolar nerve.
A 24-year-old woman is referred to the office by her orthodontist for evaluation of facial disharmony. The following angles are obtained on cephalometric analysis: SNA 70 (normal = 81.2) SNB 77 (normal = 77.3) SN-pogonion 87 (normal = 80) Which of the following procedures is most effective to achieve facial symmetry in this patient?
A) Le Fort I advancement and advancement genioplasty
B) Le Fort I advancement and setback genioplasty
C) Sagittal split mandibular advancement
D) Sagittal split mandibular setback
E) Vertical ramus osteotomy and setback
Correct answer is B
The cephalogram is a standardized radiograph used for analysis of 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 (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 SNB 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 SNPg angle is representative of the degree of chin prominence relative to the SNB (mandible position).
Normal angle values are given in the text. This patient has a relatively retrusive maxilla and a normally positioned mandible. This would represent a class III relation. The pogonion is anteriorly displaced in relation to both the mandible and the maxilla.
Therefore, to establish better facial relationships, the maxilla should be advanced at the Le Fort I level and the chin setback via a genioplasty. The mandible does not need to be moved.
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.
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.
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.
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 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.
Reference(s)
- Bykowski MR, Hill A, Garland C, et al. Ruptured pseudoaneurysm of the maxillary artery and its branches following Le Fort I osteotomy: evidence-based guidelines. J Craniofac Surg. 2018 Mar 1.
- Bauer RE, Ochs MW. Maxillary Orthognathic Surgery. Oral Maxillofac Surgery Clin North Am. 2014; 26(40):523-37.
