(A) Greater palatine and anterior superior alveolar
(B) Greater palatine and buccal
(C) Nasopalatine and anterior superior alveolar
(D) Nasopalatine and buccal
(E) Infraorbital and middle superior alveolar

The correct response is Option C.

This 25-year-old man is to undergo operative reduction of a fracture of the maxillary alveolus involving the right central and lateral incisors, followed by application of an arch bar. To obtain a sensory blockade, the surgeon must anesthetize the nasopalatine nerve to block the palate (lingual surface) and the anterior superior alveolar nerve to block the teeth and alveolar mucosa (buccal surface). The nasopalatine nerve originates from the infraorbital nerve and passes through the incisive foramen to reach the anterior hard palate. It innervates the premaxilla at this point, then extends posteriorly to innervate the maxillary cuspids. The anterior superior alveolar nerve branches from the infraorbital nerve after it exits the infraorbital foramen and provides innervation to the maxillary incisors and canine teeth.

The greater palatine nerve emerges from the greater palatine foramen and provides sensation to the posterior portion of the hard palate.

The buccal nerve provides sensation to the buccal mucosa and lower gingiva.

The middle and posterior superior alveolar nerves are derived from the infraorbital nerve after it exits the pterygopalatine fossa. The middle superior alveolar nerve innervates the bicuspids, and the posterior superior alveolar nerve innervates the first, second, and third molars within the maxilla.

References
1. Clemente CD. Anatomy: A Regional Atlas of the Human Body. 4th ed. Baltimore, Md: Williams & Wilkins; 1997:435-576.
2. Wexler A. Anatomy of the head and neck. In: Ferraro JW, ed. Fundamentals in Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:53-113.

In a 27-year-old man who has sustained bilateral parasymphyseal fractures, which of the following muscles exerts a distractive force on the anterior fracture segment?

(A) Geniohyoid
(B) Lateral pterygoid
(C) Masseter
(D) Medial pterygoid
(E) Posterior belly of the digastric muscle

The correct response is Option A.

Both anterior and posterior muscles exert forces on the mandible. The anterior muscles consist of the geniohyoid, genioglossus, mylohyoid, and digastric muscles. The muscles from this group exert primary distractive forces on the anterior fracture segment of a parasymphyseal fracture, displacing the fracture segment downward, posteriorly, and medially. The geniohyoid muscle originates from the mental spine of the inner anterior mandible and inserts on the hyoid bone. It acts to depress and retract the mandible.

The masseter, temporalis, and medial and lateral pterygoids comprise the posterior muscles. These muscles do not exert any force on the anterior segment of a parasymphyseal fracture.

The digastric muscle has an anterior and a posterior belly. The posterior belly originates on the medial aspect of the mastoid and courses forward and inferiorly as a tendon, passing through a fascial sling on the hyoid to transition into the anterior belly, which inserts into the digastric fossa of the mandible. The posterior belly of the digastric muscle primarily functions to elevate the hyoid and exhibits only a secondary effect on the anterior mandible. In contrast, the anterior belly of the digastric muscle exerts force on the anterior fracture segment.

References
1. Clemente CD. Anatomy: A Regional Atlas of the Human Body. 4th ed. Baltimore, Md: Williams & Wilkins; 1997:435-576.
2. Manson PN. Facial injuries. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:867-1141.
3. Wexler A. Anatomy of the head and neck. In: Ferraro JW, ed. Fundamentals in Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:53-113.

Simultaneous ipsilateral contractions of which of the following muscles produce the side-to-side grinding movements of the mandible?

(A) Masseter and lateral pterygoid
(B) Masseter and medial pterygoid
(C) Masseter and temporalis
(D) Medial and lateral pterygoid
(E) Medial pterygoid and temporalis

The correct response is Option D.

Simultaneous contractions of the medial and lateral pterygoid muscles largely produce the side-to-side grinding and chewing movements of the mandible. Both pairs of medial and lateral pterygoid muscles have two heads. The heads of the medial pterygoids originate from the medial surface of the lateral pterygoid plate and the tuberosity of the maxilla and insert into the medial surface of the mandibular angle and ramus. These muscles act to elevate the
mandible. The heads of the lateral pterygoids originate from the lateral surface of the lateral pterygoid plate and the infratemporal surface of the greater wing of the sphenoid and insert into the neck of the mandibular condyle and articular disk. These muscles act to protrude the mandible forward and open the mouth. When the ipsilateral medial and lateral pterygoid muscles work together, rotation occurs around the vertical axis of the contralateral condyle. Grinding and chewing movements occur when both sides alternate this action in rhythmic fashion. Simultaneous action of all four pterygoid muscles results in protrusion of the mandible.

The masseter muscle arises from the lower border and medial surface of the zygomatic arch and attaches to the lateral aspect of the mandibular ramus. It functions primarily to elevate the mandible to occlude the teeth. The temporalis muscle originates in the temporal fossa of the cranium and attaches to the coronoid process of the mandible. Although its primary function is elevation of the mandible, it can also retract the mandible because of the action of the posterior muscle fibers. Both the masseter and temporalis muscles contribute only minimally to the side-to-side grinding movements of the mandible.

References
1. Netter FH, ed. Atlas of Human Anatomy. 2nd ed. East Hanover, NJ: Novartis/Hoechstetter Printing Co, Inc; 1997:48-49.
2. Pegington J. The side of the mouth and parapharynx. In: Pegington J, ed. Clinical Anatomy In Action – The Head and Neck. Edinburgh, Scotland: Churchill Livingstone, Inc; 1986;2:143-150.
3. Snell RS, ed. Clinical Anatomy for Medical Students. 5th ed. Boston, Mass: Little, Brown & Co; 1995:671-682.
4. Williams PL, Warwick R, Dyson M, et al, eds. Gray’s Anatomy. 37th ed. Edinburgh, Scotland: Churchill Livingstone, Inc; 1989:570-575.

Which of the following nerves supplies sensory innervation to the buccal mucosa?

(A) Trigeminal (V) nerve
(B) Facial (VII) nerve
(C) Glossopharyngeal (IX) nerve
(D) Vagus (X) nerve
(E) Lingual nerve

The correct response is Option A.

The buccal branch of the trigeminal (V) nerve provides sensation to the buccal mucosa. It is important for the surgeon to know the anatomy of this nerve branch to plan and perform neurotized free flap reconstruction and reinnervation of the intraoral cavity.

The buccal branch of the facial (VII) nerve innervates the muscles surrounding the buccal mucosa.

The glossopharyngeal (IX) and vagus (X) nerves do not provide sensory innervation to the intraoral mucosa.

The lingual nerve provides sensation to a portion of the tongue.

References
1. Lutz BS, Wei FC. Microsurgical reconstruction of the buccal mucosa. Clin Plast Surg. 2001;28:339.
2. Marieb EN, ed. Overview of the digestive system. In: Human Anatomy and Physiology. Redwood City, Ca: Benjamin/Cummings Publishing; 1995.

A 29-year-old man is involved in a fistfight and sustains bilateral fractures of the mandible in the region of the canine teeth. On examination, the fractures are vertically and horizontally unstable. The central segment of the mandible is most likely to be displaced in which of the following directions?

(A) Downward and anterior
(B) Downward and posterior
(C) Rotationally
(D) Upward and anterior
(E) Upward and posterior

The correct response is Option B.

This 29-year-old man has sustained bilateral fractures of the mandible that are located in the region of the canine teeth and are unstable both vertically and horizontally. Therefore, the central segment is most likely displaced downward and posteriorly due to the action of the anterior bellies of the digastric muscles and the geniohyoid and genioglossus muscles. In addition, the power of the mylohyoid muscle pulls the posterior fracture segments medially.

Rotational displacement of the central segment may occur if the fracture is stable either vertically or horizontally because the action of the muscles would then be opposed partially. Rotational displacement is characterized by hinging of the central segment on the upper or lower border of the mandible.

Upward and anterior displacement occurs only if the central fragment becomes detached from surrounding muscles, which is unlikely.

References
1. Barber HD, Woodbury SC, Silverstein KE, et al. Mandibular fractures. In: Fonseca RJ, Walker RV, eds. Oral and Maxillofacial Trauma. 2nd ed. Philadelphia, Pa: WB Saunders Co; 1997;1:473-489.
2. Haskell R. Applied surgical anatomy. In: Williams JL, ed. Rowe and Williams’ Maxillofacial Injuries. 2nd ed. Edinburgh, Scotland: Churchill Livingstone, Inc; 1994;1:1-14.
3. Hopkins R. Mandibular fractures: treatment by closed reduction and indirect skeletal fixation. In: Williams JL, ed. Rowe and Williams’ Maxillofacial Injuries. 2nd ed. Edinburgh, Scotland: Churchill Livingstone, Inc; 1994;1:283-285.
4. Netter FH, ed. Atlas of Human Anatomy. 2nd ed. East Hanover, NJ: Novartis/Hoechstetter Printing Co, Inc; 1997:47.

Which of the following muscles of mastication pulls the mandible upward, medially, and forward?

(A) Anterior digastric
(B) Masseter
(C) Medial pterygoid
(D) Mylohyoid
(E) Temporalis

The correct response is Option C.

Knowledge of the muscles of the mandibular region and their functions in the movement of the mandible and displacement of fracture segments is crucial to accurately diagnosing and effectively treating facial fractures.

The medial pterygoid muscle exerts upward, medial, and forward traction on the mandible. This muscle arises inferiorly, laterally, and posteriorly from the medial surface of the pterygoid plate and inserts on the medial ramus and mandibular angle. Contraction of the medial pterygoid muscle pulls the mandible medially, elevating the lower jaw. A patient who sustains a fracture medial to the mandibular angle has displacement of the mandibular ramus medially and cephalad because of the forces of this muscle.

The anterior belly of the digastric muscle originates from the inside lower border of the symphysis and attaches to the lateral corner of the hyoid bone, while the posterior belly of the digastric extends between the hyoid bone and mastoid notch of the temporal bone. The digastric muscle is part of the suprahyoid musculature, which in a patient with a mandibular fracture would pull the anterior mandibular fragments posteroinferiorly.

The masseter muscle extends from the medial and lateral surfaces and lower border of the zygomatic arch to the anterolateral surface of the mandibular ramus. It exerts powerful forces of elevation on the mandible. In patients with zygomatic fractures, displacement of the zygoma is exacerbated by the chronic active traction of the masseter muscle. When performing open reduction of a zygomatic fracture, two-point wire fixation of the zygoma at the orbital rim will not diminish the forces of the masseter muscle and will instead create an axis around which the zygoma can rotate.

Because the bundles of the mylohyoid muscle join in the midline to form the muscular floor of the mouth, this muscle has only minimal influence on the movement of the mandible and hyoid bone. Instead, the mylohyoid functions to elevate the tongue.

The temporalis muscle elevates and retracts the mandible. In patients with subcondylar fractures, this muscle may elevate the mandibular ramus, resulting in loss of posterior facial height.

References
1. Dingman RO, Converse JM. The clinical management of facial injuries and fractures of the facial bones. In: Converse JM, ed. Reconstructive Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1977.
2. Hollinshead WH, ed. The face. In: Anatomy for Surgeons: The Head and Neck. Philadelphia, Pa: Harper & Row; 1982:307.
3. Manson PN, Crawley WA, Yaremchuk MJ, et al. Midface fractures: advantages of immediate extended open reduction and bone grafting. Plast Reconstr Surg. 1985;76:1.

According to the Angle classification, which of the following permanent teeth are used to determine the class of dental occlusion?

(A) Central incisors
(B) Lateral incisors
(C) First premolars
(D) Second premolars
(E) First molars

The correct response is Option E.

According to the Angle classification, the permanent first molars are used to determine the class of dental occlusion. Angle class I, or normal, occlusion is defined as the mesiobuccal cusp of the maxillary first molar lying in the buccal groove of the mandibular first molar. In Angle class II malocclusion, the mesiobuccal cusp of the maxillary first molar lies mesial (anterior) to the buccal groove of the mandibular first molar. Angle class III malocclusion is defined as the mesiobuccal cusp of the maxillary first molar lying distal (posterior) to the buccal groove of the mandibular first molar and being located instead in the buccal groove of the lower second molar.

The central incisors are used to determine overbite and overjet. Both overbite and overjet refer to the distance between the maxillary and mandibular incisors; overbite is measured vertically, and overjet is measured horizontally. In reverse overjet, which can occur in patients with Angle class III malocclusion, the maxillary central incisor lies distal (posterior) to the mandibular incisor.

The premolars and lateral incisors are less relevant than the molars and central incisors in the evaluation of occlusion.

References
1. Ash MM, Ramfjord S. Clinical occlusion. In: Ash MM, Ramfjord S, eds. Occlusion. 4th ed. Philadelphia, Pa: WB Saunders Co; 1995:50-62.
2. Donald PJ, Sykes J. Facial fractures. In: Snow JB Jr, Ballenger JJ, eds. Ballenger’s Otorhinolaryngology Head and Neck Surgery. 16th ed. Hamilton, Ontario: BC Decker; 2003:900-950.
3. Schendel SA. Orthognathic surgery. In: Vander Kolk CA, ed. Plastic Surgery: Indications, Operations, and Outcomes. Saint Louis, Mo: Mosby Year- Book, Inc; 2000;2:871-875.

A 25-year-old woman is undergoing evaluation of microgenia. Cephalometric analysis shows marked bony deficiencies in both the anteroposterior and vertical dimensions. Occlusion is normal. Which of the following is the most appropriate management?

(A) Chin implantation
(B) Intraoral vertical osteotomy
(C) Sagittal split osteotomy
(D) Osseous genioplasty
(E) Distraction osteogenesis

The correct response is Option D.

In this patient who has microgenia with anteroposterior and vertical deficiencies of the chin, the most appropriate management is osseous genioplasty. Microgenia is one of several terms used to describe abnormalities of the chin. In this condition, the chin is small and bone is deficient in all three planes. Macrogenia describes a large chin; both macrogenia and microgenia can be associated with normal occlusion or mandibular prognathism. In patients with retrogenia, the chin is positioned posteriorly but is not necessarily small. Occlusion is normal in pure retrogenia. Patients with mandibular retrognathia have secondary retrogenia. Any of the above conditions can be associated with vertical abnormalities and chin asymmetry.

This patient has moderate-to-severe vertical microgenia, which frequently includes anteroposterior deficiency of the chin. This results in decreased height of the lower face, creating an imbalance between the midface and lower face. This abnormality can be corrected by performing osseous genioplasty, which will increase the projection of the mental symphysis within the sagittal plane while compensating for the vertical deficiency.

Chin implantation is recommended to increase the anteroposterior projection of the chin but does not correct vertical deficiency or excess.

Both intraoral vertical osteotomy and sagittal split osteotomy of the mandibular ramus will alter dental occlusion and are not indicated for correction of vertical or horizontal deficiencies, especially in a patient who has normal occlusion.

Distraction osteogenesis is indicated for treatment of skeletal deficiencies (ie, Pierre Robin sequence) but is an unnecessary, excessive option for correction of this deformity.

References
1. Cohen S. Genioplasty. In: Achauer BM, Erikkson E, Guyuron B, et al., eds. Plastic Surgery: Indications, Operations, and Outcomes. Saint Louis, Mo: Mosby Year - Book, Inc; 2000:2683-2703.
2. Zide BM, Boutros S. Chin surgery III: revelations. Plast Reconstr Surg. 2003;111:1542-1550.
3. Zide BM, Longaker MT. Chin surgery: II. Submental ostectomy and soft-tissue excision. Plast Reconstr Surg. 1999;104:1854-1860.
4. Zide BM, Pfeifer TM, Longaker MT. Chin surgery: I. Augmentation--the allures and the alerts. Plast Reconstr Surg. 1999;104:1843-1853.