normal anatomy Flashcards
what’s right next to the tooth?
PDL space
o The normal PDL space is a thin, radiolucent line of uniform thickness encircling the tooth root.
o In some cases, there may be a slight increase in thickness nearer the cementoenamel junctions of teeth (e.g. anterior teeth and maxillary premolars).
what is the lamina dura?
o Refers to the thin layer of dense cortical bone which lines the normal tooth socket.
o Normal lamina dura shows variation in both thickness and radiopacity at different parts of the same tooth; how it appears is also dependent on the angulation of the x ray beam, and exposure factors used.
o Lamina dura is continuous around the roots of normal teeth.
what type of bone is the bone that is not the lamina dura?
trabecular (cancellous) bone
o In the mandible, a well-described gradient of trabeculation is seen, with the number of trabeculae increasing anteriorly, and superiorly.
o Fewer trabeculae (and therefore larger marrow spaces) are seen near the roots of the molar teeth, whereas more trabeculae (and therefore smaller marrow spaces) are seen nearer the roots of the incisor teeth.
o Fewer trabeculae are seen nearer the inferior border of the mandible, away from the tooth roots.
• Differences in the trabecular pattern in the mandible may be related to different stresses and strains developed in the bone during jaw function.
o In the maxillae, the trabecular pattern is more uniform with marrow spaces ranging in size from 1 to 3 mm.
What is the landmark between the maxillary teeth?
Intermaxillary (mid-palatal) suture
o Sometimes referred to as the mid-palatal suture, the intermaxillary suture is a very thin, radiolucent line in the maxillary midline that is bordered on either side by thin radiopaque lines.
What are three landmarks having to do with the nose?
o Floor of the nasal fossa
o The floor of the nasal fossa is a thin, linear, radiopaque line.
o In the midline, the floor of the nose intersects the base of the nasal septum.
o At the maxillary midline, a sharp bony prominence called the anterior nasal spine projects anteriorly from the floor of the fossae.
o Nasal septum
o The nasal septum is made up of 3 components:
• Vomer
• Perpendicular plate of the ethmoid bone
• Septal cartilage
o On periapical radiographs and pantomographs, we typically see only the septal cartilage and perpendicular plate of the ethmoid bone.
what is a maxillary landmark having to do with the nose and incisors?
o Incisive (nasopalatine) canal and foramen
o The incisive canal is located in the midline of the maxillae.
• The incisive canal arises as two small openings in the floors of the anterior nasal fossae; the two small canals “join” to form the main canal that opens onto the hard palate behind the maxillary central incisors to become the incisive (nasopalatine) foramen.
• The normal incisive foramen has a horizontal diameter that is usually no larger than 10 mm.
what about canals from the nose?
o Nasolacrimal ducts (canals)
o The nasolacrimal ducts arise from the medioanterior aspects of the floors of the orbits, and empty into the inferior meatus of the nasal fossa.
o The ducts are usually only seen on maxillary occlusal views, where the vertical angulation of the x ray beam is quite steep.
qhat is the Y line of ennis ?
“Y-line of Ennis”- formed by intersection of floor of nasal fossa (N) and floor of maxillary sinus (S)
o The Y-line of Ennis is a radiographic landmark in the anterior maxilla that is formed by the superimposition of the anterior border of the maxillary sinus and the floor of the nose.
o It is a landmark for the canine region of the maxilla.
What is another maxillary landmark above the teeth?
o Maxillary sinus
o The border of the maxillary sinus is a thin, often undulating, but continuous radiopaque line.
• Its cortex may be superimposed over the roots of teeth, or undulate around them.
o The border is usually continuous with the posterior border of the maxilla. In some edentulous patients who have been missing their maxillary posterior teeth for a long time, the floor of the sinus may coincide with the crest of the alveolar process.
o One may see nutrient canals, loculi and bony septa within the sinus
what bony prominence of the maxillan can be seen?
o Zygomatic process of the maxilla
o The zygomatic process of the maxilla is a thick, radiopaque, curvilinear landmark that is typically seen in the form of the letters “J” or “U”, a “reverse J”, or as a “fish-hook”.
o It is most commonly seen near the apices of the first and second molar roots, and therefore, is a landmark for this area. The zygomatic process of the maxilla should not be confused with the posterior border of the maxillary sinus.
o The inferior border of the zygomatic bone is often seen running distally from the zygomatic process of the maxilla. The irregularity of this border may be attributed to the attachment here of the masseter muscle.
Zygomatic Arch = Zygomatic Bone + Zygomatic Processes
of the Maxillary and Temporal Bones
what is the little landmark behind the last molars in the maxilla?
o Hamular process
o Extending from the medial pterygoid plate, is a small, finger-like extension called the hamular process, or hamulus.
o The hamular process may be seen on periapical radiographs of the maxillary molars.
What is by the hamular process or by the last molars on a maxllary radiograph?
coronoid process.
o Although part of the mandible, the coronoid process is sometimes seen in periapical views of the posterior maxilla.
What do soft tissue structures have to do with anything?
o Soft tissue shadows
o If soft tissue structures are thick enough, they can attenuate enough of the x ray beam to create a radiographic image (e.g. nose, nasolabial fold, etc.)
What is something in the bone of the mandible that is distinguishing for the mandible?
o Inferior cortex
o The inferior cortex is a uniform, thick radiopaque line that should be seen from the angle of the mandible on one side to the angle of the mandible on the other.
o It is often not clearly seen in growing children and adolescents, as this border is a major growth front in these age groups.
what canal in the mandible can be seen to distinguish it from the maxilla?
o Like all neurovascular canals, the inferior alveolar canal appears as a radiolucent line surrounded on both sides by thin radiopaque lines.
o Typically, the inferior border is more often seen, as fenestrations of the superior border do not allow it to be readily visualized.
o The walls of the canal are often not well corticated anterior to the second molar area
