TOPIC: NORMAL RADIOGRAPHIC ANATOMY
🌟 IMPORTANT POINTS TO REMEMBER
🔹Enamel: It is the most radiopaque normal structure in human body which consists of 92% of minerals.
🔹Dentine: It is less radiopaque as compared to enamel, which contains 65% of mineral content. The line of demarcation between enamel and dentine is sharp and well-demarcated. In bicuspid and molar teeth, DEJ is usually in a straight line. In cuspid and incisor, DEJ assumes the general contour of the tooth.
🔹Cementum: It has the same radiopacity as that of dentine. It contains 50% of mineral content.
🔹Cervical burn-out: It is a radiolucent band at the neck of the teeth radiographically appearing as radiolucent areas of the mesial or distal surface of the neck of the tooth, cervical portion of the tooth and crest of the alveolar ridge.
🔹Pulp chamber: It is the radiolucent area in the crown of the teeth.
🔹Pulp horns: Finger-like projections in the coronal portion of pulp are called pulp horns.
🔹Root canal: It tapers gradually towards the apex. In some cases, the canal may be constricted in the region of the apex and not seen in the last millimetre of length.
🔹Lamina dura: It is a dense cortical bone of tooth socket that surrounds the teeth. It is a thin white or radiopaque shadow which is continuous with the shadow of cortical bone at the alveolar crest.
🔹Double lamina dura: The image of double lamina dura appears when the mesial and distal surfaces of the root lie behind one another.
🔹Alveolar crest: Gingival margin of the alveolar process is called alveolar crest. The anterior region appears as a dense radiopaque line and the posterior region is flat, horizontal and parallel to CEJ.
🔹PDL space: It is the radiolucent space between the root of the tooth and lamina dura, composed primarily of collagen.
🔹Double PDL space: When the X-ray beam is directed so that two convexities of the root surface are projected on the film, double PDL space is seen.
🔹Cancellous bone: Cancellous bone is defined by the Latin word ‘arranged like lattice’. Anterior maxilla (trabeculae are thin), posterior maxilla (marrow spaces are slightly larger), tuberosity area (trabeculae are diminished), anterior mandible (trabeculae are somewhat thicker than maxilla) and posterior mandible (trabecular spaces are somewhat larger, and may be irregular in size).
🔹Cortical bone: It is derived from the Latin word ’cortex’ meaning outer layer. It is also called compact bone.
🔹Anterior nasal spine: It appears radiopaque because of its bony composition and is usually V-shaped.
🔹Nose: It appears as a slight uniform opacity with sharp borders.
🔹Nasal septum: It appears as the vertical radiopaque portion that divides a nasal cavity.
🔹Inferior concha: It appears as diffuse radiopaque mass within the nasal cavity.
🔹Floor of nasal cavity: It appears as a dense radiopaque band above the maxillary incisor.
🔹Zygomatic process: It appears as U-shaped radiopaque line with its open end directed superiorly.
🔹Zygoma: It appears as a diffuse radiopaque band extending posteriorly from the zygomatic process of the maxilla.
🔹Nasolabial fold: It is seen as an oblique line demarcating the region that appears to be covered by a veil of slight radiopacity.
🔹Pterygoid plate: They cast a single radiopaque Homogenous shadow without any evidence of trabeculation.
🔹Hamular process: It may be seen as a radiopaque hook-like projection posterior to the maxillary tuberosity area.
🔹Junction of the maxillary sinus and nasal cavity or inverted Y-shaped area: It appears as an inverted Y in the canine area.
🔹Maxillary tuberosity: It appears as a radiopaque bulge distal to the third molar area.
🔹Intermaxillary suture: It appears as thin radiolucent line in the midline between two portions of the maxilla.
🔹Nasal fossa or nasal cavity: It appears radiolucent area above the apices of central incisor projection.
🔹Incisive foramina: It is also called nasopalatine or anterior palatine foramina. Its image is projected in the midline between the roots and in the region of the middle and apical third of the central incisor.
🔹Superior foramina of nasopalatine canal: It can be recognised as two radiolucent areas above the apices of the central incisor in the floor of the nasal cavity.
🔹Lateral fossa: It is also called incisive fossa or canine fossa. It appears as diffuse radiolucent area between the canine and lateral incisors.
🔹Nasolacrimal canal: It may be visualized on periapical radiograph of the canine at the apex as a radiolucent area when steep angulations are used.
🔹Maxillary sinus: The floor of sinus wall is seen well above the apices of posterior teeth whilst in some it may extend beyond the apices towards the alveolar ridge. Sometimes the maxillary sinus appears as U or W-shaped. Borders of maxillary sinus appear as a thin, delicate, tenuous radiopaque line that represents a thin, layer of cortical bone.
🔹Genial tubercle: It is also called mental spine or geniohyoid tubercle. It appears as a ring-shaped radiopacity below the apices of mandibular incisor.
🔹Mental ridge: The mental ridge may occasionally be seen as two bilateral radiopaque lines sweeping forward and upwards towards the midline.
🔹Mylohyoid ridge: It appears as radiopaque band, which runs diagonally downwards and forwards from the area of the third molar to the premolar region at the level of apices of posterior teeth.
🔹External oblique ridge: Radiographically, it is seen in the posterior periapical radiograph superior to mylohyoid ridge. It appears as a radiopaque line of varying density and length.
🔹Internal oblique ridge: It appears as radiopaque band that extends downwards and forwards from the ramus.
🔹Inferior border of mandible: It is a broad radiopaque band of bone.
🔹Coronoid process: It is frequently apparent in the periapical radiographs of maxillary third molar region, lying medial to the zygomatic arch. It appears as a triangular radiopacity with its apex directed superiorly and anteriorly superimposed in the region of third molar.
🔹Lingula: It gives a radiopaque shadow, which sometimes is projected into the area of radiolucency of the foramina.
🔹Symphysis: It is seen in infants as a radiolucent line through the midline of the jaw between the images of developing deciduous central incisors.
🔹Mental fossa: It appears radiolucent just like submandibular gland fossa.
🔹Mental foramina: It may appear as a round, slit-like or irregular partially or completely corticated radiolucency located in the apical region of premolar.
🔹Lingual foramina: Periapical area of mandibular anterior region demonstrates a small radiolucent dot surrounded by the cortical wall.
🔹Mandibular canal: It is dark linear shadow with thin radiopaque superior and inferior borders caused by the lamellae of bone that bounds the canal.
🔹Nutrient canal: They are seen running vertically from the inferior dental canal directly to the apex of the tooth or into interdental space between the mandibular incisors. It appears as radiolucent lines of fairly uniform width.
🔹Submandibular gland fossa: It is a scooped-out depressed area on bone located lingually below the mylohyoid ridge.
🔹Sublingual fossa: Shadow of this fossa extends forwards and backwards to varying extents.
🔹Retromolar triangle: It appears as an area of increased radiolucency having ill-defined posterior margin. Lateral margins are more clearly seen as this triangle is enclosed between internal and external oblique ridges.
🔹Normal radiographic appearance of jaws in children: In children following landmarks are seen i.e. intermaxillary suture, symphysis menti, mental ossicles, bony trabeculae, maxillary antrum, tooth follicle, developing tooth, calcification, cortex, dental papilla, root, multirooted teeth and position of unerupted teeth.
📌 MULTIPLE CHOICE QUESTIONS (MCQS)
💡 Which is not a part of maxilla
a. Hamular notch
b. Mylohyoid line
c. Frontal process
d. Zygomatic process
Answer :b
💡 The first form hard tissue is
a. Enamel
b. Dentin
c. Pulp
d. Cementum
Answer : a
💡 PPSA refers to
a. Postpalatine seal area
b. Postpalatine sulcus area
c. Postpulp seal area
d. Postpulp sulcus area
Answer : a
💡 Radiolucent band at the neck of teeth can be
a. Cervical burn out
b. Proximal caries
c. Bone loss
d. All of the above
Answer : d
💡 The size of pulp chamber
a. Increase with an increase in age
b. Decrease with increase in age
c. Does not change with age
d. No relation with age
Answer : b
💡 Double lamina dura is seen with
a. Double roots
b. Carious root
c. Periodontitis
d. The mesial and distal surface of the root lies behind each other
Answer : d
💡 Anterior nasal spine appears as
a. V-shaped radiopacity
b. Inverted V-shaped radiopacity
c. V-shaped radiolucency
d. Inverted V-shaped radiolucency
Answer: a
💡 Inverted Y-shaped radiopacity is seen in
a. Maxillary incisor region
b. Maxillary premolar region
c. Maxillary molar region
d. Maxillary tuberosity area
Answer: b
💡 All the restorative materials are radiolucent except
a. Composite
b. Porcelain
c. Gutta-percha
d. Calcium hydroxide
Answer: c
💡 Symphysis menti is present in the mandible
a. At birth
b. At a young age
c. At old age
d. All of the above
Answer: a