Dentofacial Anatomy
What are the vertical and horizontal buttresses?
Vertical: Nasomaxillary, Zygomaticomaxillary, Pterygomaxillary
Horizontal: Frontal bar, Infraorbital rim, Zygomatic arch, Mandibular body
How do you confirm CSF rhinorrhea?
Bedside "halo test" or beta-2-transferrin test
What supplies sensation to the nasal dorsum and lateral nasal wall?
Infratrochlear and infraorbital nerves
What are the articulations of the ZMC?
ZygomaticoFrontal suture
ZygomaticoMaxillary suture
ZygomaticoSphenoid suture
ZygomaticoTemporal suture
Describe Le Fort I, II, and III fractures.
All must extend posteriorly through pterygoid plates
I - Free-floating maxilla
II - Pyramidal-shaped disjointed fracture, extends through NOE region (nasal bones)
III - Extends through pterygoid plates and ZMC and NOE regions
Describe Class I, II, and III occlusion.
Class I (normal): Mesiobucal cusp of 1st maxillary molar occludes in the buccal groove of the 1st mandibular molar
Class II: Mesiobucal cusp lies mesial to the buccal groove
Class III: Mesiobucal cusp lies distal to the buccal groove
Describe the location and drainage of the nasofrontal duct
Located in posteromedial frontal sinus, drains beneath middle meatus
Describe classification of NOE fractures.
Markowitz-Manson classification:
- Type I - the medial canthal tendon is intact and connected to a single large fracture fragment
- Type II - the fracture is comminuted, and the medial canthal tendon is attached to a single bone fragment
- Type III - comminution extends to the medial canthal tendon insertion site on the anterior medial orbital wall at the level of the lacrimal fossa, with resultant avulsion of the tendon
What incisions are used to gain surgical access to the ZMC for fracture repair?
- Upper lateral blepharoplasty incision
- Inferior lid incision
- Gingivobuccal sulcus
- Coronal incision (with severe posteriorly or laterally displaced fractures)
Le Fort I fracture with significant oronasal bleeding. How do you address the bleeding?
Anterior and posterior nasal packing
What is the difference between anterior and posterior crossbite?
Anterior crossbite: Anterior maxillary teeth are lingual to mandibular teeth
Posterior crossbite: Posterior maxillary teeth are lingual to mandibular teeth
What are possible complications associated with frontal sinus fracture?
- Contour defects
- Mucocele/pyelocele: Most commonly with involvement of ethmoid sinus. Communication with the nasal cavity causes infection of the frontal sinus mucosa.
- Meningitis
- Enophthalmos
What physical exam findings are likely in an NOE fracture?
- Telecanthus (increased distance between medial canthi)
- Decreased projection of nasal dorsum (can be masked by edema)
- Superior rotation of nasal tip
- Periorbital edema/ecchymoses, sobconjunctival hemorrhages
- Concommitant septal fracture or hematoma
Describe fixation of different classes of palatal fractures.
Type I: Alveolar - splint
Type II: Sagittal - rigid internal fixation
Type III: Para-sagittal - rigid internal fixation
Type IV: Para-alveolar - rigid internal fixation
Type V: Complex - splint
Type VI: Transverse - neither
What is the most appropriate direction of resuspension of the tendon in relation to the anterior lacrimal crest?
Posterior and superior to the anterior lacrimal crest
Describe the following vertical dental relationships: Normal, openbite, overbite
Normal: Incisal edges of the anterior maxillary teeth extend 2-3mm below the incisal edges of the mandibular teeth
Openbite: <2mm of vertical overlap
Overbite: >3mm of vertical overlap
Describe management of a displaced anterior AND posterior table fracture...
- w/ CSF leak, severe displacement, or tissue loss
- w/o CSF leak, severe displacement, or tissue loss
w/: sinus cranialization +/- pericranial flap
w/o: sinus obliteration
Describe management of a septal hematoma.
Drain/pack to avoid resorption of nasal septal cartilage
- Quilting sutures with 4-0 plain gut to prevent reaccumulation
- Antibiotics for packing, remove after 2-3 days
What is the best indication of an appropriate ZMC fracture reduction on postop CT?
Good alignment at the zygomaticosphenoid suture articulation
Describe the difference between superior orbital fissure syndrome and orbital apex syndrome.
- Superior orbital fissure syndrome: Optic nerve is spared (vs. Orbital apex syndrome)
- COMMON FINDINGS OF BOTH:
How many bones make up the orbit? Name them.
- Frontal
- Sphenoid
- Maxillary
- Zygomatic
- Palatine
- Ethmoid
- Lacrimal
Describe frontal sinus obliteration and circumstances in which you would use it.
- Coronal approach
- Complete remival of frontal sinus mucosa using a burr
- Occlusion of nasofrontal duct
- Fill sinus using: autologous fat, local fascial and pericranial flaps, allogenic materials (high infection rates), or nothing
Circumstances:
- isolated anterior table fracture with NF duct involvement
- anterior and posterior table fracture without CSF leak, severe displacement, or tissue loss
Nasal fracture: Under what conditions do you perform a closed vs. open reduction?
Closed reduction:
- Displaced fractures
- Should occur before onset of edema (<4 hours) or after edema decreases (5-7 days)
Open reduction:
- Significant septal injury
- Associated buttress dislocation
- Disruption of cartilaginous pyramid
Neither:
- Non-displaced fracture
What are possible physical findings associated with a ZMC fracture?
- Subconjunctival hemorrhage, periorbital ecchymosis, edema
- Diplopia
- Lower lid retraction
- Enophthalmos
- Proptosis
- Cheek paresthesias
- Malar flattening
- Step-offs at: Orbital rim, zygomatic arch, zygomaticomaxillary buttress
- Dystopia: Malposition of the orbital cavity
- Trismus: Posteriorly displaced ZMC impinges on coronoid process of mandible
- Inferiorly displaced lateral canthus
What are indications for surgical management of orbital floor fractures?
- Displaced fracture w/ defect >1cm2
- Smaller defects with persistent enophthalmos (>2mm)
- Symptomatic diplopia in primary field of gaze that lasts >2weeks
- Hypoglobus (inferiorly displaced globe)
- Oculocardiac reflex (bradycardia, nausea, syncope)
- Entrapment (based on CT or positive forced duction test)