Trauma mandible fractures

Question 1

Define Angle class I molar occlusion.

Answer 1

Mesiobuccal cusp of the maxillary first molar interdigitates with the mesiobuccal (central) groove of the mandibular
first molar

Question 2

Define the occlusal relationships of overjet and overbite.

Answer 2

● 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.

Question 3

Define crossbite.

Answer 3

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.

Question 4

Sublingual ecchymosis at the floor of the mouth

after trauma usually indicates what type of injury?

Answer 4

Mandibular fracture

Question 5

What nerve provides sensory innervation to the

mandible?

Answer 5

The inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve (V3)

Question 6

Which cranial nerve (CN) innervates the muscles

of mastication?

Answer 6

Trigeminal nerve (CN V3)

Question 7

List the muscles that insert into the mandible and their respective functions.

Answer 7

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.

Question 8

Describe the embryologic development of the

mandible

Answer 8

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.

Question 9

What are the subsites of the mandible?

Answer 9

Symphysis, parasymphysis, body, alveolar process, angle, ramus, coronoid, and condyle

Question 10

What are the two most common sites of

mandibular fracture?

Answer 10

The mandibular condyle and the mandibular body

Question 11

With respect to frequency, how common are

mandible fractures compared with other facial trauma injuries?

Answer 11

Nasal fractures are most common, followed by mandible fractures. Mandible fractures are two to three times more
common than midface fractures.

Question 12

What constitutes a favorable or unfavorable

fracture?

Answer 12

Fragments of the fracture are either pulled together
(favorable) or apart (unfavorable) by the tension from the
muscles of mastication.

Question 13

Define the term horizontally unfavorable in the context of classifying mandibular fractures.

Answer 13

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.

Question 14

Define the term vertically unfavorable in the

context of classifying mandibular fractures.

Answer 14

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.

Question 15

Outline the dental classification for mandibular

fractures.

Answer 15

● 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.

Question 16

How would you manage a displaced fracture of

the body of the mandible in a 5-year-old child?

Answer 16

Closed reduction with fixation using orthodontic splints

Question 17

Review the complications associated with inter-
maxillary fixation (IMF) of mandible fractures.

Answer 17

Dental injury, periodontal injury, potential for airway

compromise, weight loss or malnutrition

Question 18

List the contraindications to IMF.

Answer 18

Alcoholism, epilepsy, mental retardation, nutritional deficiency, advanced respiratory disease, psychosis, pregnancy,
noncompliant patient

Question 19

List the disadvantages of closed reduction repair of

mandible fractures.

Answer 19

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.

Question 20

What are the primary reasons for pursuing early
(within 24 to 36 hours) repair of mandible
fractures?

Answer 20

Earlier return to function and to manage pain

Question 21

Which mandible fracture has the highest incidence

of infection?

Answer 21

Mandibular angle fractures

Question 22

Review the primary indications for open reduction of mandible fractures.

Answer 22

● 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

Question 23

Describe the Champy technique of mandible

fracture repair.

Answer 23

Use of miniplate fixation in simple fractures along the ideal lines of osteosynthesis to form load-sharing or semi-rigid
fixation constructs

Question 24

How should a lag screw be placed relative to a

mandibular fracture?

Answer 24

Always place the lag screw perpendicular to the line of fracture to prevent fragments from overriding and displacement.

Question 25

Review the indications for external pin-fixation

repair of mandible fractures.

Answer 25

● 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

Question 26

Name the complications associated with open-

reduction internal fixation of mandible fractures.

Answer 26

Osteomyelitis, plate infection/loosening/extrusion/failure, malunion, nonunion, malocclusion, trismus, scaring (external approach), paresthesia

Question 27

What is the time period for primary bony healing

to occur in facial fractures treated with open reduction and internal fixation?

Answer 27

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.

Question 28

What are the radiographic characteristics of nonunion (mandibular fractures) on panoramic X-ray?

Answer 28

● 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

Question 29

What factors contribute to nonunion after mandible fracture repair?

Answer 29

● Inadequate immobilization
● Incomplete reduction
● Infection
● Poor blood supply
● Nutritional or metabolic alterations

Question 30

What structure protects the coronoid process of

the mandible when in occlusion?

Answer 30

The zygomatic arch

Question 31

What muscular force tends to distract high

condylar fractures out of alignment?

Answer 31

Medial displacement of the condyle by the pull of the lateral pterygoid muscle

Question 32

Review the absolute indications for open reduction of condylar neck fractures.

Answer 32

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

Question 33

What is the most common subunit location of

condylar process fractures?

Answer 33

Subcondylar > condylar neck > condylar head (intracapsular)

Question 34

What is the immediate concern with bilateral

condylar process fractures?

Answer 34

Airway compromise

Question 35

Review the primary reasons to consider tooth

extraction during repair of mandible fractures.

Answer 35

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