And Their Radiographic Appearance 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 Mastoid process Temporal fossa

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 Compact bone- forms plates that form outside of bones, linings for alveolus, foramina, etc… Is more radiopaque because of its density Compact bone Cancellous bone

Compact Bone Lines Alveolus (socket) It is also called (*and means same thing): Lamina dura (on radiographs only) Cribriform plate Cortical bone 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 Mandible Maxilla Zygomatic arch Condyle External auditory meatus Temporal bone

Lateral closeup 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 Dehiscence Fenestration Mental foramen Zygomatic process of maxilla Alveolar bone Alveolar crest 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 Inverted Y Maxillary sinus

Septa of maxillary sinus (divides cavity) Zygomatic Arch Floor of maxillary sinus (radiopaque)

Frontal View Identification Frontal bone Orbit Mental protuberance

Skull Identification Midline suture Anterior Nasal spine Nasal septum Infraorbital foramen Lateral fossa Superior nasal conchae 6

Anterior Radiograph Median palatal suture (radiolucent) Noseline (cartilage) Nasal spine (radiopaque V-shaped prominence) Nasal conchae 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 Lateral fossa (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

A- external oblique ridge B- internal oblique ridge C- submandibular fossa D- mandibular canal A B Hyoid bone

Mandibular foramen Mandibular canal Submandibular fossa Soft tissue outline- retromolar area Submandibular fossa (large radiolucency within the circle)

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

Nasopalatine or Incisive Palatal Radiographs Median Palatal suture Nasopalatine 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 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 Mastoid process Articular or glenoid fossa (where condyle sits)

Infratemporal Space (skull with mandible removed) Articular or Glenoid fossa Maxillary tuberosity Styloid process (can sometimes be seen on a panoral)

Condyle and glenoid fossa Hard palate Coronoid process (horizontal thicker radiopaque line)

External oblique ridge Maxillary tuberosity External oblique ridge Nasal spine Inverted Y