Nomenclature

Jaws and Temporomandibular Joint

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Jaw and TMJ Anatomy
Jaw Trauma
TMJ Abnormalities

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Abbeviations to be used in AVDC Case Logs are shown in (blue brackets)


Jaw and TMJ Anatomy

All mammals have two maxillas (or maxillae) and two mandibles. The adjective "maxillary" is often used in a wider sense, e.g., "maxillary fractures", to include other facial bones, in addition to the maxillary bone proper.

References: Anonymous. Nomina anatomica veterinaria. 4th ed. Zurich and Ithaca: World Association of Veterinary Anatomists, 1994. Evans HE. The skull. In: Evans HE, ed. Miller's anatomy of the dog. 3rd ed. Philadelphia: W.B. Saunders, 1993;128-166. Hildebrand M. Analysis of vertebrate structure. 4th ed. New York: John Wiley & Sons, 1995. Nickel R, Schummer A, Seiferle E, et al. Teeth, general and comparative. In: The viscera of domestic mammals. 1st ed. Berlin: Verlag Paul Parey, 1973;75-99. Verstraete FJM. Maxillofacial fractures. In: Slatter DH, ed. Textbook of small animal surgery. 3rd ed. Philadelphia: WB Saunders Co, 2003;2190-2207.

Incisive Bones:

In domestic animals, the correct name for the paired bones that carry the maxillary incisors, located rostral to the maxillary bones, is the incisive bones, not the premaxilla.
Reference(s): Anonymous. Nomina anatomica veterinaria. 4th ed. Zurich and Ithaca: World Association of Veterinary Anatomists, 1994.

Clinically Relevant Terms Related to the Mandible and Temporomandibular Joint:

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Anatomical Structure
Comments
Mandible All animals have two mandibles, not one; removing one entire mandible is a total mandibulectomy not a hemimandibulectomy
Body of the mandible The part that carries the teeth; often incorrectly referred to as horizontal ramus
Incisive part The part that carries the incisors
Molar part The part that carries the premolars and molars; premolar-molar part would probably have been more accurate
Alveolar margin Often incorrectly referred to as alveolar crest
Ventral margin Free ventral border
Mandibular canal Contains a neurovascular bundle; often incorrectly referred to as the medullary cavity of the mandible
Mental foramens or foramina Rostral, middle or caudal mental foramina in the dog and cat
Ramus of the mandible The part that carries the 3 processes; often incorrectly referred to as the vertical ramus
Angular process Caudoventral process (in carnivora
Coronoid process Process for the attachment of the temporal muscle 
Condylar process Consisting of mandibular head and mandibular neck; often incorrectly referred to as condyloid process
Mandibular head Articular head of the condylar process
Mandibular neck Neck of the condylar process
Mandibular notch The notch on the caudal aspect, between the coronoid and condylar processes; not to be confused with the facial vascular notch
Mandibular angle Angle between the body and ramus of the mandible.  
Facial vascular notch Shallow indentation on the ventral apsect of the mandible, rostral to the angular process (absent in carnivores)
Mandibular foramen The entrance to the mandibular canal
Intermandibular joint (mandibular symphysis) Median connection of the bodies of the right and left mandibles (in adult Sus and Equus replaced by a synostosis), consisting of intermandibular synchondrosis and intermandibular suture
Intermandibular synchondrosis The smaller part of the intermandibular joint formed by cartilage
Intermandibular suture The larger part of the intermandibular joint formed by connective tissue
Temporomandibular joint (TMJ) The area where the condylar process of the mandible articulates with the mandibular fossa of the temporal bone
Articular disk A flat structure composed of fibrocartilagenous tissue and positioned between the articular surfaces of the condylar process of the mandible and mandibular fossa of the temporal bone, separating the joint capsule in dorsal and ventral compartments; often incorrectly referred to as meniscus.
Mandibular fossa Concave depression in the temporal bone that articulates with the mandibular head
Retroarticular process A projection of the temporal bone that protrudes ventrally from the caudal end of the zygomatic arch and carries part of the mandibular fossa

Reference: Anon. Nomina anatomica veterinaria. 4th ed. Zurich, Ithaca: World Association of Veterinary Anatomists, 1994.
Scapino RP. The third joint of the canine jaw. J Morphol 1965;116:23-50.

Other Terms Relating to the Jaws and TMJ

Alveolar jugum (plural: alveolar juga): The palpable convexity of the buccal alveolar bone overlying a large tooth root. References: Anonymous. Nomina Anatomica Veterinaria. 4th ed. Zurich and Ithaca: World Association of Veterinary Anatomists, 1994. Evans HE. Miller's Anatomy of the Dog. 3rd ed. Philadelphia: WB Saunders Co, 1993.

Dental arch: Referring to the curving structure formed by the teeth in their normal position; upper dental arch formed by the maxillary teeth, lower dental arch formed by the mandibular teeth

Jaw quadrant: Referring to the left or right upper or lower jaw

Interarch: Referring to between the upper and lower dental arches

Interquadrant: Referring to between the left and right upper or lower jaw quadrants

Jaw and Related Abbeviations:


Mandible/mandibular (MN):   Referring to the lower jaw

Maxilla/maxillary (MX):   Referring to the upper jaw

Mandibular symphysis (SYM): Joint between the left and right mandibles (intermandibular joint)

Zygomatic arch (ZYG): Consisting of the zygomatic process of the temporal bone and the temporal process of the zygomatic bone; also called zygoma

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Jaw Trauma

Click Anatomy to review the Jaw and TMJ anatomy section


Maxillary fracture (MX/FX): Fracture of the upper jaw (maxilla and other facial bones)

Mandibular fracture (MN/FX): Fracture of the lower jaw (mandible)

Sympyseal separation (SYM/S): Separation of the two mandibles in the mandibular symphysis; this includes parasymphyseal fractures where the fracture line is partly or completely paramedian to the symphysis; repair of symphyseal separation with wire (circumferential or interquadrant) and/or intraoral resin splinting is abbreviated with SYM/R

Repair of a jaw fracture (FX/R): Used when any of the other abbreviations do not describe the jaw fracture repair technique applied

Maxillomandibular fixation (FX/R/MMF): Fixation that brings together the upper and lower jaws; use MMF for devices other than muzzles and splints

Muzzling (FX/R/MZ): Maxillomandibular fixation using a prefabricated or custom-made muzzle; also used in horses to prevent eating (e.g., post sedation)

Interarch splinting (FX/R/IAS): Maxillomandibular fixation using intraoral splints (commonly resin that can be reinforced with wire)

Interquadrant splinting (FX/R/IQS): Fixation using intraoral splints (commonly resin that can be reinforced with wire) between the left and right upper or lower jaw quadrants

Interdental splinting (FX/R/IDS): Fixation using intraoral splints (commonly resin that can be reinforced with wire) between teeth within a dental arch

Intraosseous wiring (FX/R/WIR/OS): Fixation using intraosseous wire

Bone plating (FX/R/PL): Fixation using bone plates

External skeletal fixation (FX/R/EXF): Fixation using pins or wires and extraoral splinting

Wire cerclage (FX/R/WIR/C): Fixation using circumferential wiring


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Temporomandibular Joint Trauma and Other Conditions


Decreased mouth opening (DMO): Difficulty opening the mouth by the animal or decreased range of mouth opening upon oral examination

Temporomandibular joint fracture (TMJ/FX): Fracture of one or more bony structures forming the temporomandibular joint; surgical repair is abbreviated with TMJ/FX/R

Temporomandibular joint ankylosis (TMJ/A): Fusion between the bones forming the temporomandibular joint or those in close proximity, resulting in progressive inability to open the mouth; removal of bone in ankylotic areas is abbreviated with TMJ/A/R

Temporomandibular joint luxation (TMJ/LUX): Displacement of the condylar process of the mandible; manual or surgical reduction of temporomandibular joint luxation is abbreviated with TMJ/LUX/R

Temporomandibular joint dysplasia (TMJ/D): Dysplasia of soft or hard tissues forming the temporomandibular joint

Open-mouth jaw locking (OMJL): Inability to close the mouth due to locking of the coronoid process of the mandible ventrolateral to the ipsilateral zygomatic arch; manual reduction of open-mouth jaw locking is abbreviated with OMJL/R

Zygomectomy (ZYG/X): Resection (usually partial) of the zygomatic arch

Coronoidectomy (COR/X): Resection (usually partial) of the coronoid process of the mandible

Condylectomy (CON/X): Resection of the condylar process of the mandible

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