Anatomical Landmarks Maxilla and Mandible Radiographic PDF

# Anatomical Landmarks Maxilla and Mandible Radiographic ## Teeth - The radiographic recognition of disease needs a sound knowledge of the radiographic appearance of normal structures. - Teeth are composed primarily from dentin and enamel cover the coronal portion, and a thin layer of cementum co...

# Anatomical Landmarks Maxilla and Mandible Radiographic ## Teeth - The radiographic recognition of disease needs a sound knowledge of the radiographic appearance of normal structures. - Teeth are composed primarily from dentin and enamel cover the coronal portion, and a thin layer of cementum cover the root - The enamel characteristically appeared more radiopaque than the other tissue, because it is the most dense naturally occurring substance in the body. Being 90% minerals, it causes the greatest attenuation of the x-ray photons, the dentin is **about** 75% mineralized and because of its lower mineral content, its radiographic appearance it is roughly comparable with bone. - Thin layer of cementum cover the root surface has mineral content 50% comparable of that in dentin. Cementum is not usually apparent radiographlly because cementum layer is so thin. - The pulp of normal teeth is composed of soft tissue and consequently appears radiolucent. The chambersand root canals containing the pulp extend from the interior of the crown to the apices of the roots. Although the shape of most pulp chambers is fairly uniform within tooth groups, great variations exist among individuals in the size of the pulp chambers and the extent of pulp horns. - A radiograph of sound teeth in a normal dental arch demonstrates that the tooth sockets are bounded by a thin radiopaque layer of dense bone. Its name, lamina dura (hard layer). - Because the periodontal ligament (PDL) is composed primarily of collagen, it appears as a radiolucent space between the tooth root and the lamina dura. This space begins at the alveolar crest, extends around the portions of the tooth roots within the alveolus, and returns to the alveolar crest on the opposite side of the tooth. ## Cancellous Bone - The cancellous bone (also called trabecular bone or spongiosa) in both jaws. To evaluate the trabecular pattern in a specific area, the practitioner should examine the trabecular distribution, size, and density and compare them throughout both jaws. - This frequently demonstrates that a particularly suspect region is characteristic for the individual. - The trabeculae in the anterior maxilla are typically thin and numerous, forming a fine, granular, dense pattern, and the mirror spaces are consequently small and relatively numerous. - In the posterior maxilla the trabecular pattern is usually quite similar to that in the anterior maxilla, although the marrow spaces may be slightly larger. - In the anterior mandible the trabeculae are somewhat thicker than in the maxilla, resulting in a coarser pattern, with trabecular plates that are oriented more horizontally. The trabecular plates are also fewer than in the maxilla, and the marrow spaces are correspondingly larger. - In the posterior mandible the periradicular trabeculae and marrow spaces may be comparable to those in the anterior mandible but are usually somewhat larger.Note... Occasionally the trabecular spaces in this region are very irregular, with some so large that they mimic pathologic lesions. # Maxillary Landmark ## Nasal fossae - The nasal fossae (plural; singular - fossa) are the nasal openings located above the maxillary anterior teeth. - The fossae are divided in the midline into right and left chambers. - Radiographically, the nasal fossae appear as vertically oblong radiolucent structures bounded by bone. - These structures can be seen on maxillary central incisor periapical views and partially on lateral incisor and canine periapical images. ## Nasal Septum - The nasal septum is a bony vertical band-like midline structure that divides the nasal cavity into right and left chambers. - The nasal septum is a radiopaque landmark visible on maxillary central incisor periapical images. ## Anterior Nasal Spine - The anterior nasal spine (ANS) is a bony projection located at the base of the nasal septum in the maxillary midline. - Radiographically, the ANS appears as a V-shaped or triangular point radiopacity. - This structure is recorded on maxillary central incisor periapical images. ## Inferior Nasal Concha - The inferior nasal concha or turbinate bone projects into the inferior aspect of the nasal fossa from the lateral walls of the nasal cavity. - These bilateral radiopaque structures (conchae) are sometimes visible on central and lateral incisor periapical images. ## Mid-palatine suture - Mid-palatine suture is the interface of the two halves of the premaxilla where they come together in the midline. - The mid-palatine suture is also referred to as the median palatal suture. - It courses from the alveolar crest through the midline to the posterior aspect of the hard palate. - This structure appears radiographically as a thin vertical linear radiolucency in the midline on maxillary central incisor periapical images. ## Incisive Foramen - The incisive or nasopalatine foramen is located in the midline on the lingual aspect of the hard palate above the central incisor teeth crowns. - The foramen is the termination of the nasopalatine canal. - Radiographically, it appears between the roots of the central incisor teeth as a round to oval radiolucency less than one centimeter in diameter. - It has a range of sizes and shapes, so variation is not unusual. - This structure is recorded on maxillary central incisor periapical images. ## Lateral Fossa - Lateral fossa – The lateral fossa is a slight dip or depression in the bone on the labial aspect of the maxilla near and around the lateral incisor tooth root. - This diffuse radiolucency appears bilaterally and is recorded on lateral incisor and canine periapical images. - It is sometimes referred to as the canine fossa ## Inverted Y - The inverted Y is a radiographic landmark that depicts where the nasal fossa crosses the maxillary sinus. - The boundary between them is shaped like an upside-down letter Y, hence its name. - The periapical images below demonstrate the inverted Y, a classic radiographic landmark of the right and left anterior maxilla. - The fossa is positioned toward the midline while the sinus extends toward the posterior aspect of the maxilla. - Typically, the inverted Y sits apical to the maxillary lateral incisor and canine teeth. - No comparable structures are found in the mandibular lateral incisor and canine areas which differentiates maxillary from mandibular anterior periapical images. ## Nasal Soft Tissue - The soft tissue of the nose, including the tip and ala (corner of the nose), often can be seen superimposed over the roots of the teeth on anterior periapical images. - The nasal soft tissue appears radiopaque. ## Maxillary Sinus - The maxillary sinus is one of the paired paranasal sinuses. - This prominent radiolucent air-filled cavity is located above the posterior teeth on the right and left sides of the maxilla. - The sinus cavities are horizontally oblong bilateral structures with fine radiopaque borders. - The maxillary sinus may contain septa which appear as radiopaque lines within the body of the sinus cavity. - The size of the maxillary sinus can be quite variable and sometimes encroaches into the alveolar process, especially when posterior teeth are missing. - Typically, the sinus appears uniform right to left. - The maxillary sinus is sometimes referred to as the maxillary antrum and can be observed on both maxillary premolar and molar periapical images and partially on lateral-canine periapical images. ## Zygomatic Bone - The zygomatic bone or cheek bone attaches to the right and left sides of the posterior maxilla. - The zygomatic bone, quadrangular in shape, broadens as it extends posteriorly. - This bilateral radiopaque structure is also known as the malar bone. - The zygomatic bone can be seen on maxillary premolar and molar periapical images. ## Zygomatic Process - The zygomatic process is the radiopaque U-shaped structure representing where the zygomatic bone attaches to the maxilla. - The zygomatic process of the maxilla is the most anterior aspect of the zygomatic bone. - The process is positioned toward the midline while the bone extends posteriorly away from the midline. - This structure is sometimes referred to as the malar process and can be seen on maxillary premolar and molar periapical images. ## Coronoid Process - The coronoid process of the mandible is the triangular bony portion of the anterosuperior aspect of the ramus. - This mandibular structure can be recorded on maxillary molar periapical images as the ramus moves forward when the patient's mouth is open. - It appears as a bilateral triangular or thumb-like radiopacity on posterior maxillary images. - The triangular portion projects forward toward the midline. - The coronoid process is the only mandibular structure recorded on maxillary molar periapical images. ## Maxillary Tuberosity - The maxillary tuberosity is the rounded end of the alveolar process of the maxilla. - This radiopaque structure appears bilaterally on maxillary molar periapical images and often on maxillary premolar periapical images and molar bitewings. - The tuberosity curves upward at the end of the maxillary alveolar process. - The tuberosity gives a smile appearance to the maxilla and the dentition particularly on bitewings. ## Pterygoid Plates - The lateral and medial pterygoid plates are located behind the maxillary tuberosity. - They project a single image configured like a thin wing of bone extending posteriorly from the tuberosity. - This bilateral radiopacity is occasionally recorded on maxillary molar periapical images when the receptor is positioned adequately posterior. ## Hamular Process - The hamular process or pterygoid hamulus is a tiny finger or hook-like projection of bone that extends inferiorly from the medial pterygoid plate. - This bilateral radiopacity occasionally appears on maxillary molar periapical images and molar bitewings when the receptor is positioned sufficiently posterior to record it. # Mandibular Anatomical Landmarks - The mandible is the lower dental arch that contains the mandibular alveolar process, the mandibular teeth and consists of the body (horizontal aspect) and ramus (posterior vertical aspect) intersecting at the angle. ## Genial Tubercle - The genial tubercle is a spiny protuberance or prominence (sometimes two) of bone located in the midline on the lingual aspect of the mandible below the roots of the incisor teeth. - This structure serves as the locus of attachment for the genioglossus and geniohyoid muscles. - Although variable in appearance, the tubercle often produces a ring-like or doughnut-shaped radiopacity on mandibular incisor periapical images. - The genial tubercle is also referred to as the mental spine. ## Lingual Foramen - The lingual foramen is a small pin-point opening in bone on the lingual aspect of the anterior mandible for the lingual nerve and arteries. - The lingual foramen appears in the midline below the apices of the central incisor teeth. - This dot-like radiolucency is frequently surrounded by the genial tubercle. - The lingual foramen is recorded on mandibular incisor periapical images. ## Mental Fossa - The mental fossa is a depression in the bone on the labial aspect of the mandible. - It has a diffuse radiolucent appearance above the mental ridge. - The mental fossa varies in its prominence depending on the thickness and density of the anterior mandible. ## Mental Ridge - The mental ridge is a prominence of bone on the labial surface of the anterior mandible. - This structure presents as an inverted V-shaped radiopaque ridge that extends from the premolar to canine area on each side meeting in the midline. - The mental ridge varies in its presentation with some individuals displaying very distinct ridge anatomy while others, little or no evidence of its presence. - This mandibular landmark can be recorded on incisor and partially on the lateral aspect of canine periapical images. ## Mental Foramen - The mental foramen, the primary landmark of this area, is a circular radiolucent structure located below the roots of the mandibular premolar teeth. - This structure is the opening for passage of the mental nerve and vessels and can be observed on mandibular premolar and the lateral aspect of canine periapical images. - This bilateral radiolucency can be misinterpreted as a periapical lesion. - However, it is easily differentiated upon closer examination of the tooth and its supporting structures. ## External Oblique Ridge - The external oblique ridge or line is the bony anterior border of the ramus located on the outer aspect of the mandible. - This ridge has a downward diagonal course and is seen on most mandibular molar periapical images and molar bitewings. - It is more prominent and appears more frequently than the internal oblique ridge which will be discussed next. - This bilateral radiopaque landmark gives the mandible and the dentition a smile appearance. ## Internal Oblique Ridge - The internal oblique ridge is the bony ridge found bilaterally on the lingual aspect of the posterior mandible. - This radiopaque ridge is variable in its appearance ranging from highly defined to barely visible. - When recorded on molar periapical images, it runs parallel to but below the external oblique ridge. - The internal oblique ridge is sometimes referred to as the mylohyoid line. ## Mandibular Canal - The mandibular canal is the pathway in bone where the inferior alveolar nerve and blood vessels course through the mandible. - The canal extends from the mandibular foramen within the ramus anteriorly to the mental foramen. - This tubular bilateral radiolucency often demonstrates fine radiopaque boundaries. - The mandibular canal is recorded on mandibular premolar and molar periapical images. - It is also referred to as the inferior alveolar nerve canal. - The mandibular foramen is not recorded on mandibular periapical images. ## Submandibular Fossa - The submandibular fossa is a depression in bone on the lingual aspect of the posterior mandible. - The fossa is located bilaterally below the internal oblique ridge or mylohyoid line. - This concavity is where the submandibular salivary gland rests. - The submandibular fossa presents as a diffuse bilateral radiolucency typically with few trabeculae. - It can appear unusually radiolucent, enticing the novice clinician into thinking a bony lesion is present. - The submandibular fossa is recorded on premolar and molar periapical images. - This structure is also referred to as the submandibular gland fossa or mandibular fossa. ## Lower Border - The lower border of the mandible appears as a radiopaque band of dense cortical bone demarcating the inferior aspect of the mandible. - This structure can be observed on any mandibular periapical view, especially when the x-ray beam angulation is excessive. ## References - Langland.O.E., Langlais .R.P., diganostic Imagings of the jaw, 1st edn, Williams & Wilkins. - Langland.O.E., Langlais .R.P., Principles of Dental Imaging, 1st edn, Williams & Wilkins.