Orthognathic, TMJ, Chin Flashcards
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 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.
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.
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.
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 29-year-old woman comes to the office for evaluation of orthognathic profile and class I occlusion. Physical examination shows isolated retrogenia and moderate vertical mandibular excess. Which of the following types of genioplasty is most appropriate?
(A) Advancement with horizontal osteotomy only
(B) Advancement with horizontal osteotomy and downgrafting
(C) Advancement with inferiorly angled osteotomy
(D) Alloplastic augmentation, extraoral approach
(E) Alloplastic augmentation, intraoral approach
The correct response is Option C.
The most appropriate genial treatment option is advancement with the osteotomy angled inferiorly. The angle of the osteotomy has an impact on the vertical dimension of the mandible as the segment is advanced forward. An osteotomy angled inferiorly in relation to the occlusal plane will provide a progressive decrease in the vertical dimension as the osteotomy segment is advanced. A 2- to 4-mm reduction in chin height can be achieved with this technique. When a larger height reduction (in excess of 5 mm) is indicated, a horizontal wafer of bone is removed above the horizontal sliding osteotomy. A horizontal osteotomy, relatively parallel to the occlusal plane, would provide a more pure anteroposterior movement.
Downgrafting the osteotomy site, with an interpositional bone graft or alloplastic material, would be indicated to increase the vertical dimension in a patient with vertical mandibular deficiency.
Alloplastic augmentation alone, whether placed through an intraoral or extraoral approach, is best indicated for a unidimensional change, such as a pure sagittal deficiency.
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.
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.
A 34-year-old woman undergoes a down-fracture of the maxilla during Le Fort I osteotomy. Profuse bleeding is noted in the posterior aspect of the lateral nasal wall. Injury to which of the following arteries is most likely?
(A) Anterior ethmoidal
(B) Descending palatine
(C) Greater palatine
(D) Infraorbital
(E) Nasopalatine
The correct response is Option B.
The descending palatine artery is a branch of the third portion of the internal maxillary artery. It descends vertically within the perpendicular portion of the palatine bone. Injury to this vessel is not uncommon while performing a Le Fort I osteotomy. Division of this artery has been shown not to expose the maxilla to necrosis.
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 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.
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 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 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 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
Correct answer 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.
A 34-year-old woman undergoes a down-fracture of the maxilla during Le Fort I osteotomy. Profuse bleeding is noted in the posterior aspect of the lateral nasal wall. Injury to which of the following arteries is most likely?
(A) Anterior ethmoidal
(B) Descending palatine
(C) Greater palatine
(D) Infraorbital
(E) Nasopalatine
The correct response is Option B.
The descending palatine artery is a branch of the third portion of the internal maxillary artery. It descends vertically within the perpendicular portion of the palatine bone. Injury to this vessel is not uncommon while performing a Le Fort I osteotomy. Division of this artery has been shown not to expose the maxilla to necrosis.
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.
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.
Interorbital distance is most accurately determined by measuring the distance between which of the following structures?
(A) Anterior lacrimal crests
(B) Inferior orbital fissures on a plain anteroposterior cephalogram
(C) Lateral aspects of the medial canthi on standard anteroposterior photograph
(D) Pupils on a standard anteroposterior photograph
(E) Supraorbitale (SOr) €” the most anterior point of the intersection of the orbital roof and its lateral contour
The correct response is Option A.
By convention, the interorbital distance is determined as the shortest distance between the medial walls of the orbit. This usually falls at the dacryon, which refers to the craniometric point at the junction of the anterior border of the lacrimal bone with the frontal bone. The normal distance is approximately 25 mm in women and 28 mm in men.
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.
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.
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 24-year-old woman comes to the office for consultation regarding her appearance when smiling. Physical examination shows the mesiobuccal cusp of the first maxillary molar lying distal to the buccal groove of the first mandibular molar. Which of the following is the most appropriate Angle classification?
(A) I
(B) IIA
(C) IIB
(D) III
The correct response is Option D.
Occlusion as described by the Angle classification uses the relationship of the permanent first molars of the maxilla and mandible as its reference point. Patients with class I occlusion (normal) have the mesiobuccal cusp of the maxillary first molar lying in the buccal groove of the mandibular first molar. Patients with class II occlusion have the mesiobuccal cusp of the maxillary first molar located mesial to the buccal groove of the mandibular first molar. Class III occlusion, as illustrated in this case, is described as having the mesiobuccal cusp of the maxillary first molar positioned distal to the buccal groove of the mandibular first molar.
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.
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
The correct response is Option 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.
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.
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 surge
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 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 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.
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.
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 34-year-old woman desires an improved aesthetic appearance of the chin. On physical examination, she has a bony chin deformity characterized by sagittal deficiency and vertical mandibular excess. She has class I occlusion. Which of the following genioplasty procedures should be performed in this patient?
(A) Asymmetric genioplasty
(B) Interposition genioplasty
(C) Jumping genioplasty
(D) Sliding genioplasty
(E) Silastic implantation
The correct response is Option C.
This 34-year-old woman who has a bony chin deformity should undergo jumping genioplasty. In this procedure, the transverse osteotomy is performed initially, decreasing the vertical dimension of the chin; following this, the osteotomized segment is transposed anteriorly with its attached suprahyoid musculature to augment the sagittal deficiency.
Asymmetric genioplasty involves adjusting the lines of osteotomy in multiple vectors in order to correct a misshapen chin. Interposition genioplasty can be performed to increase the vertical and sagittal dimensions of the chin; autogenous bone or hydroxyapatite can be grafted to the osteotomy site. Although sliding genioplasty can be used for correction of a sagittal deficiency or an excessively large chin, the change in vertical chin dimension seen following this procedure is only minimal. Silastic implantation will correct the sagittal deficiency but not the vertical excess.
Which of the following is the most common indication for performing distraction osteogenesis of the mandible in a 6-month-old infant?
(A) Malocclusion
(B) Mandibular hypoplasia with tongue-based airway obstruction
(C) Mandibular hypoplasia with tracheomalacia
(D) Unilateral craniofacial microsomia
The correct response is Option B.
In patients younger than age 2 years, mandibular distraction osteogenesis should only be performed when there is tongue-based airway compromise secondary to mandibular hypoplasia. In these patients, pulling the mandible forward will also pull the base of the tongue forward, relieving the airway obstruction.
Children younger than age 2 years with congenital hypoplasia or aplasia of select portions of the mandible but without airway compromise should not undergo distraction osteogenesis of the mandible because of the risk for permanent dental injury. In addition, mandibular procedures are associated with the potential for injury to the inferior alveolar nerve. Similarly, any procedures to correct malocclusion should only be performed after the permanent dentition has been established. Because children younger than age 1 year have either no dentition or rudimentary dentition and because the tooth buds are difficult to identify, operative correction of malocclusion is inappropriate.
Advancing the mandible and the base of the tongue will not relieve airway obstruction secondary to other causes, such as tracheomalacia or laryngomalacia. In neonates with these conditions, tracheotomy may be required for airway control.
Although distraction osteogenesis is typically performed in patients who have hemifacial microsomia (which can involve absence of the ramus, condyle, and/or glenoid fossa), it is only initiated in patients older than 1 year.
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.
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.
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.
A 24-year-old woman with maxillary hypoplasia is scheduled to undergo Le Fort I osteotomy. In order to protect the maxillary dentition, the osteotomy must be carried out above the dental apices. Which of the following maxillary teeth have the longest roots?
(A) Central incisors
(B) Lateral incisors
(C) Cuspids
(D) First bicuspids
(E) First molars
The correct response is Option C.
The cuspids, or canine teeth, have the longest roots in both the maxilla and mandible. The average length of a cuspid tooth from the tip of the root to the tip of the crown is 27 mm.
Knowledge of the length and position of the dental roots will help to prevent injury during Le Fort I osteotomy and placement of internal fixation during fracture reduction. The dentition can also be injured during stabilization of maxillary or mandibular fractures.
The average length of a molar tooth from the tip of the root to the tip of the crown is 24 mm. The length of the upper first molar is 21.3 mm.
The cuspid tooth is named for its single cusp; bicuspids have two cusps (buccal and lingual), and molars have three cusps (mesiobuccal, distobuccal, and mesiolingual). The average adult has two maxillary cuspids, four maxillary bicuspids, and six maxillary molars.
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.
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.
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.
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.
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.
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 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 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
The correct response is Option 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.
A 27-year-old woman desires surgical correction because she has an edentulous appearance. Physical examination shows decreased height in the lower third of the face and absence of maxillary incisor show. Cephalometric analysis shows an acute mandibular plane angle.
Which of the following operative procedures is most appropriate?
(A) Genioplasty
(B) Le Fort I osteotomy with inferior repositioning
(C) Le Fort I osteotomy with maxillary impaction
(D) Le Fort III osteotomy
(E) Bilateral sagittal split osteotomy of the mandible
The correct response is Option B.
This patient has findings consistent with vertical maxillary deficiency, or short face syndrome. Affected patients have a vertical decrease in facial height and absence of maxillary show, resulting in an edentulous appearance. The upper lip appears short and flat; the bite is deep, and the chin protrudes excessively. The alar bases are wide. The mandibular plane angle is acute.
Appropriate management of vertical maxillary deficiency is Le Fort I osteotomy with inferior repositioning of the maxilla. Bone grafts can be interposed to stabilize the mandible during downward movements and prevent recurrence of the deformity.
Genioplasty can be performed as an adjuvant to Le Fort I osteotomy to improve the aesthetic appearance of the chin but will not effectively increase maxillary height if performed alone.
Le Fort I osteotomy with maxillary impaction is performed to shorten the face in patients with vertical maxillary excess.
Le Fort III osteotomy is not indicated for patients with deformities limited to the lower third of the face.
Bilateral sagittal split osteotomy can be combined with downfracture of the maxilla to improve facial projection but will not improve midface height when performed 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.
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
Correct answer is 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 24 year old woman comes to the office because she has had popping of the left temporomandibular joint and associated mild pain that have been worsening over the past six months. The patient says she also has intermittent inability to fully open her mouth, but she does not believe her symptoms restrict her daily routine. Physical examination shows mild bilateral tenderness of the preauricular region but no popping, clicking, or crepitus. Maximal incisal opening is 20 to 25 mm, and lateral and protrusive excursions are reduced. MRI of the temporomandibular joints shows mild anterior dislocation of the left meniscus with reduction in the open mouth position. Which of the following is the most appropriate initial management?
(A) Administration of a nonsteroidal anti-inflammatory drug, occlusal splint therapy, and restriction to soft diet
(B) Comprehensive orthodontic therapy with bilateral sagittal ramus osteotomies of the mandible
(C) Initial intra-articular injection of a corticosteroid followed by serial injections if symptoms do not resolve
(D) Open arthrotomy with meniscectomy followed by a brief period of joint immobilization and then physical therapy
(E) Open arthrotomy with plication of the meniscus followed by a brief period of joint immobilization and then physical therapy
The correct response is Option A.
With symptoms and clinical findings of mild pain and popping of the temporomandibular joint, mild tenderness of the preauricular region, and transient joint locking, the patient described has an early/intermediate stage internal derangement. MRI shows only mild changes in meniscal position. Therefore, conservative therapy such as a soft diet, use of nonsteroidal anti-inflammatory drugs, and splinting is indicated. Most patients with temporomandibular joint disorders will achieve some relief of symptoms with nonsurgical therapy within a period of two to three years. However, the pathologic process may continue, and follow €‘up is recommended.
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 24-year-old woman comes to the office for consultation regarding her appearance when smiling. Physical examination shows the mesiobuccal cusp of the first maxillary molar lying distal to the buccal groove of the first mandibular molar. Which of the following is the most appropriate Angle classification?
(A) I
(B) IIA
(C) IIB
(D) III
The correct response is Option D.
Occlusion as described by the Angle classification uses the relationship of the permanent first molars of the maxilla and mandible as its reference point. Patients with class I occlusion (normal) have the mesiobuccal cusp of the maxillary first molar lying in the buccal groove of the mandibular first molar. Patients with class II occlusion have the mesiobuccal cusp of the maxillary first molar located mesial to the buccal groove of the mandibular first molar. Class III occlusion, as illustrated in this case, is described as having the mesiobuccal cusp of the maxillary first molar positioned distal to the buccal groove of the mandibular first molar.
A 16-year-old girl with a history of rheumatoid arthritis has mandibular retrusion and an anterior open bite. Skeletal maturity is complete. Which of the following is most appropriate for correction of the deformity?
(A) Use of orthodontic functional appliances
(B) Advancement sagittal split osteotomy and advancement genioplasty
(C) Maxillary impaction and advancement genioplasty
(D) Maxillary impaction, advancement sagittal split osteotomy, and genioplasty
The correct response is Option C.
Because episodes of juvenile rheumatoid arthritis can be triggered by increased loading on the temporomandibular joint, orthognathic procedures should be limited to those that minimize condylar load. Therefore, the most appropriate procedure for correction of this child’s deformity is maxillary impaction, which will allow closure of the open bite without creating condylar load. The resultant mandibular autorotation of the mandible will increase the SNB (sella-nasion-point B) angle, thereby correcting the mandibular deficiency. Any subsequent sagittal deficiency of the mandible can be improved with advancement genioplasty.
Orthodontic functional appliances are not effective in a 16-year-old patient and are relatively contraindicated in patients with juvenile rheumatoid arthritis because of the forces exerted on the temporomandibular joint. Mandibular advancement will result in increased condylar load, leading to degenerative remodeling.
Advancement sagittal split osteotomy is less acceptable than maxillary impaction and advancement genioplasty because it will increase condylar load.
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.
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 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.
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.
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 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.
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.
