Trauma mandible fractures Flashcards
Define Angle class I molar occlusion.
Mesiobuccal cusp of the maxillary first molar interdigitates with the mesiobuccal (central) groove of the mandibular
first molar
Define the occlusal relationships of overjet and overbite.
● Overbite is the vertical distance that the incisal edges of the maxillary anterior teeth overlap the incisal edges of the mandibular anterior teeth in an inferosuperior
direction.
● Overjet is the horizontal distance that the incisal edges of
the anterior maxillary teeth project beyond the incisal edges of the mandibular anterior teeth in an anteropos-
terior direction.
Define crossbite.
Under normal occlusal relationships, the maxillary dentition
should be located in a position more buccal than the mandibular counterparts. For the anterior teeth (incisiors
and canines), the maxillary teeth should be more anterior than the mandibular teeth. For the posterior teeth (premolars and molars), the maxillary teeth should be more lateral than the mandibular teeth. A crossbite is when these
occlusal relationships are reversed.
Sublingual ecchymosis at the floor of the mouth
after trauma usually indicates what type of injury?
Mandibular fracture
What nerve provides sensory innervation to the
mandible?
The inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve (V3)
Which cranial nerve (CN) innervates the muscles
of mastication?
Trigeminal nerve (CN V3)
List the muscles that insert into the mandible and their respective functions.
The digastric muscles and the geniohyoid extert posteroinferior pull on the mandible. The masseters, medial pterygoids, and temporalis muscles elevate the mandible.
The lateral pterygoids cause translation of the condylar processes of the mandible and facilitate mandibular opening. The mylohyoid serves to elevate the tongue and floor of mouth and also has the ability to depress the mandible if
the position of the hyoid is fixed.
Describe the embryologic development of the
mandible
During the 4th week of embryologic development, the
mandibular processes (first branchial arch derivatives) fuse
in the midline. The mandibular processes then develop into
the mandible and lower face.
What are the subsites of the mandible?
Symphysis, parasymphysis, body, alveolar process, angle, ramus, coronoid, and condyle
What are the two most common sites of
mandibular fracture?
The mandibular condyle and the mandibular body
With respect to frequency, how common are
mandible fractures compared with other facial trauma injuries?
Nasal fractures are most common, followed by mandible fractures. Mandible fractures are two to three times more
common than midface fractures.
What constitutes a favorable or unfavorable
fracture?
Fragments of the fracture are either pulled together
(favorable) or apart (unfavorable) by the tension from the
muscles of mastication.
Define the term horizontally unfavorable in the context of classifying mandibular fractures.
A horizontally unfavorable fracture is one that is unable to
resist the upward displacing forces on the mandible by the
muscles of mastication when viewed in the horizontal plane. Muscles typically responsible for horizontally unfavorable fractures are the temporalis, masseter, and medial pterygoid.
Define the term vertically unfavorable in the
context of classifying mandibular fractures.
A vertically unfavorable fracture is one that is unable to resist
medial displacing forces on the mandible by the muscles of mastication when viewed in a vertical plane. Muscles typically responsible for vertically unfavo1rable fractures are the medial pterygoids, the suprahyoid muscles, and the digastric muscles.
Outline the dental classification for mandibular
fractures.
● Class I: Teeth are present on both sides of the fracture
line.
● Class II: Teeth are present on only one side of the fracture
line.
● Class III: No teeth are in proximity of either side of the
fracture line.
How would you manage a displaced fracture of
the body of the mandible in a 5-year-old child?
Closed reduction with fixation using orthodontic splints
Review the complications associated with inter- maxillary fixation (IMF) of mandible fractures.
Dental injury, periodontal injury, potential for airway
compromise, weight loss or malnutrition
List the contraindications to IMF.
Alcoholism, epilepsy, mental retardation, nutritional deficiency, advanced respiratory disease, psychosis, pregnancy,
noncompliant patient
List the disadvantages of closed reduction repair of
mandible fractures.
Fractures lines are not rigidly fixed, which leads to indirect (secondary) bone healing. Prolonged IMF may result in temporomandibular joint (TMJ) ankylosis, and IMF fixation renders oral hygiene and adequate oral intake difficult.
What are the primary reasons for pursuing early
(within 24 to 36 hours) repair of mandible
fractures?
Earlier return to function and to manage pain
Which mandible fracture has the highest incidence
of infection?
Mandibular angle fractures
Review the primary indications for open reduction of mandible fractures.
● Unfavorable or unstable fractures
● Concurrent comminuted facial fractures
● Edentulous mandible with severe displacement
● Delayed treatment with interposing soft tissue that
prevents adequate closed reduction
● Patients with contraindications to IMF
Describe the Champy technique of mandible
fracture repair.
Use of miniplate fixation in simple fractures along the ideal lines of osteosynthesis to form load-sharing or semi-rigid
fixation constructs
How should a lag screw be placed relative to a
mandibular fracture?
Always place the lag screw perpendicular to the line of fracture to prevent fragments from overriding and displacement.
Review the indications for external pin-fixation
repair of mandible fractures.
● Severely comminuted fractures
● Pathological fractures
● Grossly infected fracture sites or fractures with a high
propensity for future infection (e.g., gunshot wounds)
● Comminuted edentulous mandible fractures
Name the complications associated with open-
reduction internal fixation of mandible fractures.
Osteomyelitis, plate infection/loosening/extrusion/failure, malunion, nonunion, malocclusion, trismus, scaring (external approach), paresthesia
What is the time period for primary bony healing
to occur in facial fractures treated with open reduction and internal fixation?
Primary bony healing of repaired facial fractures takes place over 4 to 10 weeks. If healing does not take place by this
time, the diagnosis of nonunion can be suspected.
What are the radiographic characteristics of nonunion (mandibular fractures) on panoramic X-ray?
● Sclerotic bone margins
● Osteolytic changes within the bone adjacent to the fracture site
● A persistent radiolucent gap where bone has not bridged
the fracture site
What factors contribute to nonunion after mandible fracture repair?
● Inadequate immobilization ● Incomplete reduction ● Infection ● Poor blood supply ● Nutritional or metabolic alterations
What structure protects the coronoid process of
the mandible when in occlusion?
The zygomatic arch
What muscular force tends to distract high
condylar fractures out of alignment?
Medial displacement of the condyle by the pull of the lateral pterygoid muscle
Review the absolute indications for open reduction of condylar neck fractures.
Invasion of joint by foreign body
Lateral extracapsular displacement
Inability to achieve occlusion with closed reduction Involvement of the middle cranial fossa or external auditory canal
What is the most common subunit location of
condylar process fractures?
Subcondylar > condylar neck > condylar head (intracapsular)
What is the immediate concern with bilateral
condylar process fractures?
Airway compromise
Review the primary reasons to consider tooth
extraction during repair of mandible fractures.
Evidence of periapical or gross periodontal infection, tooth
preventing fracture reduction, root fracture, exposure of root apex after fracture reduction, teeth without adequate bone support, partially erupted third molars with evidence of active pericornitis
