Normal Anatomy Of Intraoral And Extraoral Radiographs Question And Answers

Normal Anatomy Of Intraoral And Extraoral Radiographs

Question 1. Describe various anatomic landmarks seen on periapical radiographs.
or
Describe normal radiographic anatomical landmark of maxilla and mandible
Answer. Radiographic appearance of various structures which are visualized on the intraoral periapical radiograph are classified as:

 

Normal teeth anatomy in maxilla and mandible

• Enamel
• Dentin
• Cementum
• Pulp cavity

Supporting structures

• Lamina dura
• Alveolar crest
• Periodontal ligament space
• Cancellous bone

Read And Learn More: Oral Radiology Question And Answers

Maxilla

• Radiopaque bony landmarks of maxilla
  • Nasal septum
  • Anterior nasal spine
  • Floor of nasal cavity
  • Inferior nasal conchae
  • Nasolabial fold
  • Floor of maxillary sinus
  • Septae in maxillary sinus
  • Inverted Y in maxillary sinus
  • Zygomatic process of the maxilla
  • Zygoma
  • Pterygoid plates
  • Hamular process
  • Maxillary tuberosity
• Radiolucent bony landmarks of maxilla
  • Nutrient canals
  • Intermaxillary suture
  • Nasal fossa
  • Incisive foramen
  • Superior foramina of nasopalatine canal
  • Incisive fossa
  • Nasolacrimal canal
  • Maxillary sinus
  • Nose

Mandible

• Radiopaque bony landmarks of mandible
  • Genial tubercle
  • Mental ridge
  • Mylohyoid ridge
  • External oblique ridge
  • Inferior border of mandible
  • Coronoid process
  • Internal oblique ridge
• Radiolucent bony landmarks of mandible
• • Lingual foramen
  • Symphysis
  • Mental fossa
  • Mental foramen
  • Mandibular canal
  • Submandibular fossa

Normal Teeth Anatomy in Maxilla and Mandible

• Enamel: This is the densest structure. It is seen as the outer most radiopaque layer of the crown of a tooth on the radiograph.
• Dentin: It is found beneath the enamel layer and surrounds the pulp. It is less radiopaque than enamel.
• Cementum: It is not usually apparent on the radiograph because the cementum layer is very thin.
• Pulp cavity: This consists of the pulp chamber and the root canals. It contains blood vessels and nerves and appears relatively radiolucent in the radiograph.

Supporting structures

• Lamina dura: This is the wall of tooth socket that surrounds the teeth, it is made up of dense cortical bone. It appears as a thin dense radiopaque line that surrounds the root of the tooth.
• Alveolar crest: This is the most coronal portion of the alveolar bone found between the teeth. It appears as a radiopaque area located 1.5 to 2 cm below the junction of the crown and the root surfaces.
• Cancellous bone: This is sof spongy bone located between two layers of dense cortical bone. It is composed of numerous bony trabeculae. On radiograph, the cancellous bone appears as predominantly radiolucent with the trabeculae appearing radiopaque in a cris cross pattrn.
• Periodontal ligament space: It is a space between the root of the tooth and the lamina dura. The PDL space contains connective tissue fiers, blood vessels and lymphatic. On radiograph, it appears as a thin radiolucent line of uniform thickness around the root of the teeth.

Radiopaque Bony Landmarks of Maxilla

• Nasal septum: It is a vertical bony wall or partition that divides the nasal cavity into the right and lef nasal fossa. It appears as a vertical radiopaque partition that divides the nasal cavity.
• Anterior nasal spine: V-shaped radiopaque area located at the intersection of the flor of the nasal cavity and nasal septum.
• Floor of the nasal cavity: Appear as dense radiopaque band above the maxillary incisors.
• Inferior nasal conchae: A diffse radiopaque mass or projection within the nasal cavity.
• Nasolabial fold: It is an oblique line demarcating a region that appears to be covered by a veil of slight radiopacity which is seen in premolar region. Line of contrast is sharp and area of increased radiopacity is posterior to the line. Line is the nasolabial fold and veil is thick cheek tissue superimposed on teeth and alveolar process.
• Floor of maxillary sinus: A radiopaque line appears at above the apices of maxillary molars is indicative of flor of maxillary sinus.
• Septa in maxillary sinus: Boney projection or partition which appear to divide the sinus in compartments.
• Inverted-Y in maxillary sinus: It is the intersection of maxillary sinus and nasal cavity. It appears as radiopaque upside down Y formed due to intersection of flor of nasal fossa and anterior border of maxillary sinus.
• Zygomatic process of maxilla: “J” or “U” shaped radiopacity located superior to the maxillary fist molar region.
• Zygoma: Adiffse radiopaque band extending posteriorly form the zygomatic process of the maxilla.
• Pterygoid plates: A single radiopaque homogeneous shadow immediately posterior to the tuberosity of the maxilla.
• Hamular plates: It is a small hook like projection of bone extending from the medial pterygoid plate of the sphenoid bone.
• Maxillary tuberosity: This is a rounded prominence of bone which extends posterior to the third molar region. On radiograph, it appear as a radiopaque bulge posterior to the third molar region.

Radiolucent Bony Landmarks of Maxilla

• Intermaxillary suture: It is the immovable joint between the two palatine processes of maxilla. It extends from the alveolar bone between the maxillary incisor to the posterior hard palate. It appears as a thin radiolucent line between the maxillary central incisors.
• Nasal fossa: It is a pear-shaped, air-filed compartment of bone located superior to maxilla. On radiograph, it appears as large radiolucent area above the maxillary incisors.
• Incisive foramen: It is an opening located in the midline of the anterior portion of the hard palate posterior to central incisors. On radiograph it appears as a small radiolucent round area between the roots of maxillary central incisors.
• Superior foramina of nasopalatine canal: It appears as two small radiolucent areas located superior to the apices ofthe maxillary central incisors, in the flor of the nasal cavity.
• Incisive fossa: It is a smooth depressed area of maxilla located just inferior and medial to infraorbital foramen between lateral incisors and canine. On radiograph, it appears as a radiolucent area between canine and lateral incisor.
• Nasolacrimal canal: It is formed by the nasal and maxillary bone, running from the medial aspect of the anteroinferior border of the orbit. On radiograph, it appears as a welldefied slightly ovoid radiolucency, just above the apex of the maxillary canine.
• Maxillary sinus: These are paired three-sided pyramidal cavities of bone within the maxilla.
• On the radiograph it appear as radiolucent area located above the apices of the maxillary molars.
• Nose: Image of nose has uniform slight opaque appearance with sharp border and sometimes radiolucent nares can be identified.

Radiopaque Bony Landmarks of Mandible

• Genial tubercles: These are tiny bumps of bone on the lingual side of the mandible in midline and serve as attachment for the genioglossus and the geniohyoid muscle. Radiographically appear as ring-shaped radiopacities below the apices of the mandibular incisors.
• Mental ridge: This is a linear prominence of cortical bony plate, located on external surface of the anterior portion of the mandible. It appear as a thick radiopaque band that extends from premolar to incisor region.
• Mylohyoid ridge: This is a linear prominence of the bone located on the internal surface of the mandible, extending from molar region downwards and forwards towards the lower border of the mandibular symphysis.
• External oblique ridge: It appears as a radiopaque band extending downwards and forwards from the anterior border of the ramus of the mandible.
• Inferior border of the mandible: It appears as a dense radiopaque band of bone in the lower border of the mandible.
• Coronoid process: It is a marked prominence of bone on the anterior ramus of the mandible. On radiograph, it appears as triangular radiopacity superimposed over or inferior to the maxillary tuberosity region.
• Internal oblique ridge: On radiograph, it appear as a radiopaque band which extend downward and forward from the ramus.

Radiolucent Bony Landmarks of Mandible

• Nutrient canals: They are tube like passages through the bone which consists of nerves and blood vessels which supply the teeth. On radiograph they appear as vertical radiolucent lines. They are prominent in anterior region and in edentulous mandible.
• Lingual foramen: It is a tiny opening in the bone located on the internal surface of the mandible near the midline. It appears as a small radiolucent dot inferior to the apices of the mandibular incisors.
• Symphysis: On radiograph, it appears as a radiolucent line through the midline of the jaw. After one year of life it does not appear radiographically.
• Mental fossa: This is a scooped out depressed area of the bones located on the external surface of the anterior mandible. On radiograph it appears as a radiolucent area above the mental ridge.
• Mental foramen: It is an opening in the bone located in the external surface of the mandible, in the region of the mandibular premolar. Blood vessels and nerves that supply the lower lip exit through the mental foramen. On radiograph, it appears as a small liquid fist round radiolucent area located in the apical region of the premolar.
• Mandibular canal: It is a tube-like passage through the bone that travels the length of the mandible. It extends from the mandibular foramen to the mental foramen and houses the inferior alveolar nerve and blood vessels. Radiographically appears as a radiolucent band, outlined by two thin radiopaque lines.
• Submandibular fossa: It is a depressed area of bone located on the internal surface of the mandible inferior to mylohyoid line. It houses the submandibular salivary gland. On radiograph appear as a radiolucent area in the molar region below mylohyoid ridge.

Question 2. Write short note on radiopaque anatomical landmarks seen in intraoral periapical radiography.
Answer. Radiopaque anatomical landmarks seen in intraoral periapical radiography are:

Radiopaque normal teeth anatomy in maxilla and mandible

• Enamel
• Dentin
• Cementum

Radiopaque-supporting structures

• Lamina dura
• Alveolar crest
• Cancellous bone

Radiopaque bony anatomical landmarks in maxilla

• Nasal septum
• Anterior nasal spine
• Floor of nasal cavity
• Inferior nasal conchae
• Nasolabial fold
• Floor of maxillary sinus
• Septae in maxillary sinus
• Inverted-Y in maxillary sinus
• Zygomatic process of the maxilla
• Zygoma
• Pterygoid plates
• Hamular process
• Maxillary tuberosity

Radiopaque bony anatomical landmarks in mandible

• Genial tubercle
• Mental ridge
• Mylohyoid ridge
• External oblique ridge
• Inferior border of mandible
• Coronoid process
• Internal oblique ridge

Radiopaque Normal Teeth Anatomy in Maxilla and Mandible

• Enamel: This is the densest structure. It is seen as the outer most radiopaque layer of the crown of a tooth on the radiograph.
• Dentin: It is found beneath the enamel layer and surrounds the pulp. It is less radiopaque than enamel.
• Cementum: It is not usually apparent on the radiograph because the cementum layer is very thin.

Radiopaque supporting structures

• Lamina dura: This is the wall oftooth socket that surrounds the teeth, it is made up of dense cortical bone. It appears as a thin dense radiopaque line that surrounds the root of the tooth.
• Alveolar crest: This is the most coronal portion of the alveolar bone found between the teeth. It appears as a radiopaque area located 1.5 to 2 cm below the junction of the crown and the root surfaces.
• Cancellous bone: This is soft spongy bone located between two layers of dense cortical bone. It is composed of numerous bony trabeculae. On radiograph, the cancellous bone appears as predominantly radiolucent with the trabeculae appearing radiopaque in a criss-cross pattern.

Radiopaque Bony Landmarks of Maxilla

• Nasal septum: It is a vertical bony wall or partition that divides the nasal cavity into the right and lef nasal fossa. It appears as a vertical radiopaque partition that divides the nasal cavity.
• Anterior nasal spine: V-shaped radiopaque area located at the intersection of the flor of the nasal cavity and nasal septum.
• Floor of the nasal cavity: Appear as dense radiopaque band above the maxillary incisors.
• Inferior nasal conchae: A diffse radiopaque mass or projection within the nasal cavity.
• Nasolabial fold: It is an oblique line demarcating a region that appears to be covered by a veil of slight radiopacity which is seen in premolar region. Line of contrast is sharp and area of increased radiopacity is posterior to the line. Line is the nasolabial fold and veil is thick cheek tissue superimposed on teeth and alveolar process.
• Floor of maxillary sinus: A radiopaque line appears at above the apices of maxillary molars is indicative of flor of maxillary sinus.
• Septa in maxillary sinus: Boney projection or partition which appear to divide the sinus in compartments.
• Inverted-Y in maxillary sinus: It is the intersection of maxillary sinus and nasal cavity. It appears as radiopaque upside down Y formed due to intersection of flor of nasal fossa and anterior border of maxillary sinus.
• Zygomatic process of maxilla: “J” or “U” shaped radiopacity located superior to the maxillary fist molar region.
• Zygoma: A diffuse radiopaque band extending posteriorly form the zygomatic process of the maxilla.
• Pterygoid plates: A single radiopaque homogeneous shadow immediately posterior to the tuberosity of the maxilla.
• Hamular plates: It is a small hook-like projection of bone extending from the medial pterygoid plate of the sphenoid bone.
• Maxillary tuberosity: This is a rounded prominence of bone which extends posterior to the third molar region. On radiograph, it appears as a radiopaque bulge posterior to the third molar region.

Radiopaque Bony Landmarks of Mandible

• Genial tubercles: These are tiny bumps of bone on the lingual side of the mandible in mid line and serve as attchmentforthe genioglossus and the geniohyoid muscle. Radiographically appear as ring-shaped radiopacities below the apices of the mandibular incisors.
• Mental ridge: This is a linear prominence of cortical bony plate, located on external surface of the anterior portion of the mandible. It appear as a thick radiopaque band that extends from premolar to incisor region.
• Mylohyoid ridge: This is a linear prominence of the bone located on the internal surface of the mandible, extending from molar region downwards and forward towards the lower border of the mandibular symphysis.
• External oblique ridge: It appears as a radiopaque band extending downwards and forwards from the anterior border of the ramus of the mandible.
• Inferior border of the mandible: It appears as a dense radiopaque band of bone in the lower border of the mandible.
• Coronoid process: It is a marked prominence of bone on the anterior ramus of the mandible. On radiograph, it appears as triangular radiopacity superimposed over or inferior to the maxillary tuberosity region.
• Internal oblique ridge: On radiograph, it appear as a radiopaque band which extend downward and forward from the ramus.

Question 3. Write short note on radiographic anatomical landmarks of mandible.
Answer. Following are the radiographic anatomical landmark of mandible

Radiopaque anatomical Landmarks in Mandible

• Enamel
• Dentin
• Cementum
• Lamina dura
• Alveolar crest
• Cancellous bone
• Genial tubercle
• Mental ridge
• Mylohyoid ridge
• External oblique ridge
• Inferior border of mandible
• Coronoid process
• Internal oblique ridge

Radiolucent anatomical Landmarks in Mandible

• Pulp
• Periodontal ligament space
• Nutrient canals
• Lingual foramen
• Symphysis
• Mental fossa
• Mental foramen
• Mandibular canal
• Submandibular fossa

Radiopaque anatomical Landmarks in Mandible

• Enamel: This is the densest structure. It is seen as the outer most radiopaque layer of the crown of a tooth on the radiograph.
• Dentin: It is found beneath the enamel layer and surrounds the pulp. It is less radiopaque than enamel.
• Cementum: It is not usually apparent on the radiograph because the cementum layer is very thin.
• Lamina dura: This is the wall oftooth socket that surrounds the teeth, it is made up of dense cortical bone. It appears as a thin dense radiopaque line that surrounds the root of the tooth.
• Alveolar crest: This is the most coronal portion of the alveolar bone found between the teeth. It appears as a radiopaque area located 1.5 to 2 cm below the junction of the crown and the root surfaces.
• Cancellous bone: This is sof spongy bone located between two layers of dense cortical bone. It is composed of numerous bony trabeculae. On radiograph, the cancellous bone appears as predominantly radiolucent with the trabeculae appearing radiopaque in a cris-cross pattrn.
• Genial tubercles: These are tiny bumps of bone on the lingual side of the mandible in midline and serve as attachmentforthe genioglossus and the geniohyoid muscle. Radiographically appear as ring shaped radiopacities below the apices of the mandibular incisors.
• Mental ridge: This is a linear prominence of cortical bony plate, located on external surface of the anterior portion of the mandible. It appear as a thick radiopaque band that extends from premolar to incisor region.
• Mylohyoid ridge: This is a linear prominence of the bone located on the internal surface of the mandible, extending from molar region downwards and forwards towards the lower border of the mandibular symphysis.
• External oblique ridge: It appears as a radiopaque band extending downwards and forwards from the anterior border of the ramus of the mandible.
• Inferior border of the mandible: It appears as a dense radiopaque band of bone in the lower border of mandible.
• Coronoid process: It is a marked prominence of bone on the anterior ramus of the mandible. On radiograph, it appears as triangular radiopacity superimposed over or inferior to the maxillary tuberosity region.
• Internal oblique ridge: On radiograph, it appear as a radiopaque band which extend downward and forward from the ramus.

Radiolucent anatomical Landmarks in Mandible

• Pulp cavity: This consists of the pulp chamber and the root canals. It contains blood vessels and nerves and appears relatively radiolucent in the radiograph.
• Periodontal ligament space: It is a space between the root of the tooth and the lamina dura. The PDL space contains connective tissue fiers, blood vessels and lymphatic. On radiograph, it appears as a thin radiolucent line of uniform thickness around the root of the teeth.
• Nutrient canals: They are tube-like passages through the bone which consists of nerves and blood vessels which supply the teeth. On radiograph, they appear as vertical radiolucent lines. They are prominent in anterior region and in edentulous mandible.
• Lingual foramen: It is a tiny opening in the bone located on the internal surface of the mandible near the midline. It appears as a small radiolucent dot inferior to the apices of the mandibular incisors.
• Symphysis: On radiograph, it appears as a radiolucent line through the midline of the jaw. Aftr one year of life, it does not appear radiographically.
• Mental fossa: This is a scooped out depressed area of the bones located on the external surface of the anterior mandible. On radiograph, it appears as a radiolucent area above the mental ridge.
• Mental foramen: It is an opening in the bone located in the external surface of the mandible, in the region of the mandibular premolar. Blood vessels and nerves that supply the lower lip exit through the mental foramen. On radiograph, it appears as a small liquid fist round radiolucent area located in the apical region of the premolar.
• Mandibular canal: It is a tube-like passage through the bone that travels the length of the mandible. It extends from the mandibular foramen to the mental foramen and houses the inferior alveolar nerve and blood vessels. Radiographically appears as a radiolucent band, outlined by two thin radiopaque lines.
• Submandibular fossa: It is a depressed area of bone located on the internal surface of the mandible inferior to mylohyoid line. It houses the submandibular salivary gland. On radiograph appear as a radiolucent area in the molar region below mylohyoid ridge.