And Their Radiographic Appearance

BONES

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

Mastoid processTemporal fossasuture

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 bone- forms 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

Lamina dura(radiopaque lining)

Periodontal ligament space(radiolucent lining)

Compact bone outlines alveolar crest (when no bone has been lost due to periodontal disease!)

Alveolar crest (radiopaque)

Do you see any compact bone outlining the alveolar crest?

Lateral View Identification

1. Mandible

2. Maxilla

3. Zygomatic arch

4. Condyle

5. External auditory meatus

6. Temporal bone

Lateral closeup

1. Condyle

2. Articular eminence

3. Coronoid process

4. Ramus

5. Articular fossa

6. Mandibular notch

7. Coronoid notch

6

7

Temporomandibular Joint

• 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”

Articular or gleniod fossa

Articular eminance

Lateral closeup

1. Dehiscence

2. Fenestration

3. Mental foramen

4. 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

dehiscencefenestration

Bones of the Orbit

In order of appearance• Frontal• Zygomatic• Maxillary• Palatine• Sphenoid• Lacrimal• Ethmoid

Maxillary Sinus

Nasal Cavity Orbit

Zygomatic Arch

• Commonly called the “cheekbone”

• Comprised of three bones, temporal, maxilla, zygoma

maxilla

zygoma

temporal

sutures

Zygomatic Arch

Maxillary process of zygoma joins with zygomatic process of maxilla

Zygomatic process of temporal bone joins with temporal process of zygoma

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 sinusInside 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

Maxillary sinusNasal cavity Inverted Y

Floor of maxillary sinus(radiopaque)

Zygomatic Arch

Septa of maxillary sinus (divides cavity)

Frontal View Identification

1. Frontal bone

2. Orbit

3. Mental protuberance

Skull Identification

1. Midline suture

2. Anterior Nasal spine

3. Nasal septum

4. Infraorbital foramen

5. Lateral fossa

6. 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

Nasal septum(divides nasal cavity)

Anterior Nasal spine (V-shaped)

Lateral fossa(Radiolucency inside circle)

Inferior nasal conchae

Mandibular foramen

Internal Oblique ridge- (slightly inferior to external oblique ridge)

Lingula – a bony projection that partially covers the mandibular foramen

Mental ridge- see figure 27-56 Iannucci

Lingual foramen

Genial tubercles (muscles attach here)

Submandibular fossa (depression for submandibular Salivary gland)

Coronoid notchCoronoid process

External oblique ridge

Mandibular (sigmoid) Notch

Ramus

Condyle

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 internaloblique ridge (mylohyoid muscle attachment); internal usually runs below roots of mandibularmolars (see figure 27-41, 27-43 Iannucci)

Internal on “inside” or lingual

A- external oblique ridgeB- internal oblique ridgeC- submandibular fossaD- mandibular canal

B

A

Hyoid bone

Mandibular foramen

Mandibular canal

Submandibular fossa(large radiolucencywithin the circle)

Soft tissue outline- retromolar area

Mandibular canal

External oblique ridge

Submandibular fossa

Nutrient canals – passageways to teeth for vessels (arrows on film), often seen around maxillary premolars

Lingual foramen(radiolucency)

Genial tubercles(Radiopacities)

Mental Foramen

Mylohyoid ridge or internal oblique ridge(see down by roots of teeth)– actually on lingual of mandible

Nasopalatine orIncisive foramen

Palate

Anterior or Greater

palatine foramen

Median palatine suture

Posterior or Lessor palatine foramen

Hamulus

Palatal Radiographs

Median Palatal sutureNasopalatine or Incisive foramen

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

Lateral pterygoid plateHamulus

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)

Maxillarytuberosity

Styloid process (can sometimes beseen on a panoral)

Articular or Glenoid fossa

Condyleand glenoid fossa

Hard palate(horizontal thicker radiopaque line)

Coronoidprocess

Maxillary tuberosity

Inverted Y

External oblique ridge

Nasal spine