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)
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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
Terms that describe bone anatomy
• Notch – indentation
on the edge of a bone
• Ridge – elongated
prominence
• Foramen - opening
Mental foramen
External oblique ridge
Temporal fossa
Mastoid process
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
Mandibular notch
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
trabeculation
2
Compact bone outlines alveolar crest (when no
bone has been lost due to periodontal disease!)
Compact Bone Lines Alveolus (socket)
Alveolar crest (radiopaque)
It is also called (*and
means same thing):
1. Lamina dura (on
radiographs only)
2. Cribriform plate
3. Cortical bone
4. Alveolar bone proper
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
3
Temporomandibular Joint
Lateral closeup
1.
2.
3.
4.
5.
6.
7.
Condyle
Articular eminence
Coronoid process
Ramus
Articular fossa
Mandibular notch
Coronoid notch
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”
6
7
Lateral closeup
Dehiscence
Fenestration
Mental foramen
Zygomatic process
of maxilla
5. Alveolar bone
6. Alveolar crest
7. External oblique
ridge
Dehiscence vs Fenestration
1.
2.
3.
4.
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• 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
4
Nasal Cavity
Bones of the Orbit
Orbit
Maxillary Sinus
In order of appearance
• Frontal
• Zygomatic
• Maxillary
• Palatine
• Sphenoid
• Lacrimal
• Ethmoid
Zygomatic Arch
• Commonly called
the “cheekbone”
• Comprised of
three bones,
temporal, maxilla,
zygoma
Zygomatic Arch
Zygomatic process of
temporal bone
joins with temporal
process of zygoma
temporal
Maxillary process of zygoma
joins with zygomatic
process of maxilla
zygoma
maxilla
sutures
Zygomatic Arch
5
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
Inverted Y
Nasal cavity
Maxillary sinus
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”
6
Septa of maxillary sinus (divides cavity)
Zygomatic Arch
Floor of maxillary sinus
(radiopaque)
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
Anterior Radiograph
1. Median palatal suture
5
(radiolucent)
6
2. Noseline (cartilage)
3. Nasal spine (radiopaque
V-shaped prominence)
4. Nasal conchae
5. Nasal septum (elongated,
thicker radiopacity)
7
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)
Lingual foramen
Genial tubercles
(muscles attach here)
Mandibular
foramen
Mental ridge- see figure 27-56 Iannucci
Lingula – a bony projection that
partially covers the mandibular foramen
Submandibular fossa
(depression for submandibular
Salivary gland)
8
Coronoid process
Coronoid notch
Mandibular (sigmoid)
Notch
Condyle
External oblique ridge
(thicker radiopaque band)
Ramus
External oblique ridge
Angle of the mandible
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 26-62 Haring)
ABCD-
Internal on “inside” or lingual
external oblique ridge
internal oblique ridge
submandibular fossa
mandibular canal
A
B
Hyoid bone
9
Mandibular foramen
Mandibular canal
External oblique ridge
Soft tissue outline- retromolar area
Submandibular fossa
Mandibular
canal
(large radiolucency
within the circle)
Submandibular fossa
Nutrient canals – passageways to
teeth for vessels (arrows on film),
often seen around maxillary premolars
Genial tubercles
(Radiopacities)
Lingual foramen
(radiolucency)
10
Palate
Nasopalatine or
Incisive foramen
Median palatine suture
Mental Foramen
Anterior or Greater
palatine foramen
Mylohyoid ridge or internal oblique ridge
(see down by roots of teeth)– actually
on lingual of mandible
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
11
Infratemporal Space
(skull with mandible removed)
Temporal bone
Articular or
Glenoid
fossa
• 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
Maxillary
tuberosity
Styloid process (can sometimes be
seen on a panoral)
Maxillary tuberosity
External oblique ridge
Nasal spine
Coronoid
process
Condyle
and glenoid fossa
Hard palate
(horizontal thicker radiopaque line)
Inverted Y
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