BONES
And Their Radiographic
Appearance
22 Bones make up the skull
Cranial bones include:
• Occipital (one)
• Frontal (one)
• Parietal (two)
• Temporal (two)
• Sphenoid (one)
• Ethmoid (one)
Cranial bones surround
the brain
The Skull Bones:
1 - mandible
2 - maxilla
3 - zygomatic
4 - nasal bone
5 - frontal bone
6 - sphenoid bone
7 - temporal
8 - occipital bone
9 - lacrimal bone
10 - ethmoid bone
11 - parietal bone
Facial bones include:
• Mandible (one)
• Maxilla (two)
• Zygomatic (two)
• Lacrimal (two)
• Nasal (two)
• Inferior nasal conchal
(two)
• Vomer (one)
Terms that describe bone anatomy
• Process – general term
for any prominence
• Fossa - depression on
the surface of the bone
• Suture – where two
bones join
• Tuberosity – bony
prominance, usually
where muscle attaches,
ie maxillary tuberosity
suture
Temporal fossa
Mastoid process
Terms that describe bone anatomy
• Notch – indentation
on the edge of a bone
• Ridge – elongated
prominence
• Foramen - opening
Mental foramen
External oblique ridge
Mandibular notch
Two types of Bone – compact and
cancellous
• Cancellous bone
(also called spongy
bone) makes up
center of bones
• Contains bone
marrow spaces
(called “trabeculation”
on radiographs)
• More radiolucent than
compact bone
trabeculation
Compact Bone
1. Compact boneforms plates that
form outside of
bones, linings for
alveolus, foramina,
etc…
2. Is more radiopaque
because of its
density
Compact bone
Cancellous bone
Compact Bone Lines Alveolus (socket)
It is also called (*and
means same thing):
1. Lamina dura (on
radiographs only)
2. Cribriform plate
3. Cortical bone
4. Alveolar bone proper
Compact bone outlines alveolar crest (when no
bone has been lost due to periodontal disease!)
Alveolar crest (radiopaque)
Periodontal ligament space
(radiolucent lining)
Lamina dura
(radiopaque lining)
Do you see any compact bone
outlining the alveolar crest?
Lateral View Identification
1.
2.
3.
4.
5.
Mandible
Maxilla
Zygomatic arch
Condyle
External auditory
meatus
6. Temporal bone
Lateral closeup
1.
2.
3.
4.
5.
6.
7.
Condyle
Articular eminence
Coronoid process
Ramus
Articular fossa
Mandibular notch
Coronoid notch
6
7
Temporomandibular Joint
Articular or gleniod fossa
Articular eminance
• Mandibular condyle
articulates with temporal
bone in the articular fossa
(also called glenoid fossa,
mandibular fossa)
• Most anterior border of
articular fossa is the
articular eminance
• If someone opens wide
and the condyle slides
anterior to the eminance,
the person has “lockjaw”
Lateral closeup
1.
2.
3.
4.
Dehiscence
Fenestration
Mental foramen
Zygomatic process
of maxilla
5. Alveolar bone
6. Alveolar crest
7. External oblique
ridge
7
Dehiscence vs Fenestration
• Bony defects of
unknown cause
• Neither can be found
radiographically, only
during surgery
• Fenestration, defect
completely surrounded
by bone
• Dehiscence, alveolar
crest bone absent
fenestration
dehiscence
Bones of the Orbit
In order of appearance
• Frontal
• Zygomatic
• Maxillary
• Palatine
• Sphenoid
• Lacrimal
• Ethmoid
Nasal Cavity
Orbit
Maxillary Sinus
Zygomatic Arch
• Commonly called
the “cheekbone”
• Comprised of
three bones,
temporal, maxilla,
zygoma
temporal
zygoma
maxilla
sutures
Zygomatic Arch
Zygomatic process of
temporal bone
joins with temporal
process of zygoma
Maxillary process of zygoma
joins with zygomatic
process of maxilla
Zygomatic Arch
Radiographically, the zygomatic arch appears as a
radiopaque horseshoe shaped structure above maxillary
molars (not always seen)
Maxillary Sinus – an opening in the maxillary
bone, acts as a filter for inhaled air
Location of the sinus
Inside of sinus with bony covering removed
Inverted Y
• Maxillary sinus meets
nasal cavity in area of
canine
• On radiographs, wall of
sinus crosses wall of
nasal cavity (both are
radiopaque because they are
compact bone)
• Result is the “inverted Y”
Inverted Y
Nasal cavity
Maxillary sinus
Inverted Y
Septa of maxillary sinus (divides cavity)
Floor of maxillary sinus
(radiopaque)
Zygomatic Arch
Frontal View Identification
1. Frontal bone
2. Orbit
3. Mental protuberance
Skull Identification
1.
2.
3.
4.
5.
6.
Midline suture
Anterior Nasal spine
Nasal septum
Infraorbital foramen
Lateral fossa
Superior nasal
conchae
6
Anterior Radiograph
1. Median palatal suture
(radiolucent)
2. Noseline (cartilage)
3. Nasal spine (radiopaque
V-shaped prominence)
4. Nasal conchae
5. Nasal septum (elongated,
thicker radiopacity)
5
Lateral Fossa – a depression between the
maxillary cuspid and incisor
Exercise – feel your lateral fossa with your finger
Inferior nasal
conchae
Nasal septum
(divides nasal cavity)
Anterior Nasal
spine (V-shaped)
Lateral fossa
(Radiolucency inside circle)
Internal Oblique ridge(slightly inferior to
external oblique ridge)
Mandibular
foramen
Mental ridge- see figure 27-56 Iannucci
Lingula – a bony projection that
partially covers the mandibular foramen
Lingual foramen
Genial tubercles
(muscles attach here)
Submandibular fossa
(depression for submandibular
Salivary gland)
Coronoid process
Coronoid notch
Mandibular (sigmoid)
Notch
Condyle
Ramus
External oblique ridge
Angle of the mandible
External oblique ridge
(thicker radiopaque band)
Note: External/internal ridges often “superimposed” over each other radiographically;
therefore difficult to differentiate between the two; external always superior to internal
oblique ridge (mylohyoid muscle attachment); internal usually runs below roots of mandibular
molars (see figure 27-41, 27-43 Iannucci)
Internal on “inside” or lingual
ABCD-
A
B
Hyoid bone
external oblique ridge
internal oblique ridge
submandibular fossa
mandibular canal
Mandibular foramen
Mandibular canal
Submandibular fossa
(large radiolucency
within the circle)
Soft tissue outline- retromolar area
External oblique ridge
Mandibular
canal
Submandibular fossa
Nutrient canals – passageways to
teeth for vessels (arrows on film),
often seen around maxillary premolars
Genial tubercles
(Radiopacities)
Lingual foramen
(radiolucency)
Mental Foramen
Mylohyoid ridge or internal oblique ridge
(see down by roots of teeth)– actually
on lingual of mandible
Palate
Nasopalatine or
Incisive foramen
Median palatine suture
Anterior or Greater
palatine foramen
Posterior or Lessor
palatine foramen
Hamulus
Palatal Radiographs
Nasopalatine or Incisive
foramen
Median Palatal suture
Sphenoid Bone
• A butterfly shaped
cranial bone posterior
to the palate
• It forms part of the orbit
• It’s hamulus can
sometimes be seen on
third molar radiograph
• Some muscles of
masticaton attach to
Pterygoid plate
Hamulus
Lateral pterygoid plate
Temporal bone
• A cranial bone that
articulates with
mandible in its
articular fossa
• Other landmarks
include styloid
process, mastoid
process
• Forms part of
zygomatic arch
Articular or glenoid fossa
(where condyle sits)
Mastoid process
Infratemporal Space
(skull with mandible removed)
Articular or
Glenoid
fossa
Maxillary
tuberosity
Styloid process (can sometimes be
seen on a panoral)
Coronoid
process
Hard palate
(horizontal thicker radiopaque line)
Condyle
and glenoid fossa
Maxillary tuberosity
External oblique ridge
Nasal spine
Inverted Y