NORMAL RADIOGRAPHIC ANATOMY

  • Thicker, more mineralized or denser tissue appears radiopaque.
  • Less dense, thinner or demineralized tissue appears radiolucent.
  • Term radiolucent (dark/black) or radiopaque (light/white) used in plain radiographic image like intra oral, panoramic or extra oral radiographs.  

Figure1: Radiographic appearance of enamel, dentin and pulp

  1. Enamel
    • Most radiopaque.
    • Covers the coronal portion of tooth.
    • The line of demarcation between enamel and dentine is k/a dentinoenamel junction (DEJ).
    • Caries is most common disease affecting the enamel. (Figure:1)
  2. Dentin
    • Less radiopaque- white.
    • Dentin appears less dense or lighter than the underlying pulp but darker than the overlying enamel.
    • Caries is most common disease affecting the dentin extended through the enamel. (Figure:1)
  3. Pulp
    • The pulp tissue is not visible radiographically.
    • The space that contains the pulp is visible and forms the most radiolucent (dark) portions of the tooth.
    • The pulp spaces decrease in size with advancing age.
    • The root canal space tapers gently toward the apex.
    • The apical foramen is the terminal portion of the root canal space at the apex of the tooth through which the vital elements of the tooth pass.
    • At the end of a developing; tooth root the pulp canal diverges and the walls of the toot rapidly taper to a knife edge. (Figure:1)

Figure 2: Cervical burnout

The constricted cervical neck of the tooth, the area between the crown and the root, absorbs less x-ray energy than the areas above and below it. This is because of the presence of enamel above and the alveolar bone covering the root of this tooth below the cervical neck. It results in a radiolucent band running across the cervical neck of anterior teeth and a triangular, wedge shaped radiolucency at the inter-proximal cervical neck of the posterior teeth. This is called cervical burnout (Figure:2).

  • Root caries appears as saucer- shaped or having a cupped – out appearance. Root caries is usually located in the region of the interproximal cementoenamel junction. It does not usually involve the enamel; it may undermine the enamel by spreading underneath it.
  • Cervical burnout is seen in the cervical region of the teeth as a radiolucent triangular area on the interproximal surfaces of the posterior teeth and as radiolucent band on the anterior teeth.
  • Lamina dura.
  • Alveolar crest.
  • Periodontal ligament space.
  • Cancellous bone.

Figure 3: Lamina dura

A radiograph of sound teeth in a dental arch demonstrates that the tooth socket is bounded by a thin radiopaque layer of dense bone. Its name, lamina dura (“hard layer”) is derived from its radiographic appearance. (Figure: 3)

The name lamina dura (or alveolus) is applied to the thin layer of dense cortical bone (the so–called cribriform plate or alveolar bone proper) which lines the normal tooth socket.

It radiographic appearance is caused by the fact that x-ray beam passes tangentially through many times the thickness of thin bony wall which results in its observed attenuation (egg-shell effect).

  • When the x-ray beam is directed through a relatively long expanse of the structure, the lamina dura appears radiopaque and well defined.
  • When the beam is directed more obliquely, however, the lamina dura appears more diffuse and may not be discernible.
  1. Common Normal Variations
    • Apex of Maxillary Canine.
    • Rotated Tooth.
    • Maxillary Premolars – before maturation.
    • Projection over the maxillary sinus.
    • Projection over the mandibular Canal.
    • Projection over the mental foramen.
  2. Pathologic
    • Inflammatory periapical diseases.
    • Peri-apical granuloma.
    • Radicular cyst.
    • Simple bone cyst.
    • Peri-apical cemental dysplasia.
    • Osteomyelitis
  3. Uncommon
    • Malignant Tumor.
    • Fibrous Histiocytoma.
    • Histiocytosis –X.
  1. Common
    • Idiopathic.
    • Paget Disease of Bone.
    • Leukemia.
  2. Uncommon
    • Metastatic Malignancy (especially breast).
    • Hyperparathyroidism.
    • Multiple Myeloma.
    • Osteomalacia.
    • Rickets (Including Vitamin D resistant Rickets).
    • Cushing syndrome.
    • Osteomalacia.
    • Rickets (Including Vitamin D resistant Rickets).
    • Postmenopausal Osteoporosis.
    • Renal Acidosis.
    • Acromegaly.
    • Oxalosis.
    • Hypervitaminosis D.
    • Hypovitaminosis C.
    • Systemic Sclerosis (Scleroderma).
    • Hypophosphatasia.

Teeth in heavy occlusion.

Thinner and less dense around teeth not subjected to occlusal function.

Figure 4: Double Lamina dura

The image of a double lamina dura appears when mesial or distal surfaces of roots present two elevations in the path of the x-ray beam. (Figure: 4)

  • Alveolar crest is the gingival margin of the alveolar process that extends between the teeth is apparent on radiographs as a radiopaque line.
  • Normal level of alveolar crest is when it is not more than 1.5mm from the cementoenamel junction of the adjacent teeth.
  • In the anterior region the crest is reduced to only a point of bone between the close-set incisors.
  • Posteriorly it is flat, aligned parallel with and slightly below a line connecting the cementoenamel junctions of the adjacent teeth.
  • The crest of the bone is continuous with the lamina dura and forms a sharp angle with it.
  • Rounding of these sharp junctions is indicative of periodontal disease.

Figure 5: Normal appearance of periodontal ligament space

  • It is a soft connective tissue between the inner wall of the alveolar socket and the roots of the teeth.
  • It consists of collagen bands (mostly type I collagen) connecting the cementum of teeth to the gingivae and alveolar bone.
  • Fibroblasts are the main cells in the PDL, which form, maintain, and repair the alveolar bone and cementum.
  • Radiographically, the PDL is seen as a radiolucent space between the lamina dura and the tooth root.
  • The normal width of the PDL ranges from 0.15 mm to 0.21 mm, which may decrease with age.
  • Orthodontic movement of teeth results in PDL widening, but the lamina dura remains intact.(Figure:5)
  1. Traumatic causes
    • Occlusal/orthodontic trauma.
    • Radiation-induced bone defect.
  2. Infectious causes
    • Periodontal disease/periodontitis.
    • Pulpo-periapical lesions.
    • Osteomyelitis.
  3. Neoplastic lesions of the jawbones
    • Osteosarcoma.
    • Chondrosarcoma.
    • Non-Hodgkin lymphoma (NHL).
  4. Systemic causes
    • Progressive systemic sclerosis.
    • Bisphosphonate-related osteonecrosis.

The alveolar bone is divided into:

  1. Alveolar bone proper (compact bone).
  2. Supporting alveolar bone (cortical and trabecular bone).

The trabecular bone (cancellous bone) is located between alveolar bone proper and plates of cortical bone.

  • Also k/a trabecular bone or spongiosa that lies between the cortical plates in both jaws.
  • It is composed of thin radiopaque plates and rods (trabeculae) surrounding many small radiolucent pockets of marrow.
    1. Anterior maxilla

Thin and numerous, forming a fine, granular, dense pattern and marrow spaces are consequently small and relatively numerous.

    1. Posterior maxilla

Trabeculae are typically thin, and numerous, forming a fine, granular, dense pattern, and the marrow spaces are consequently slightly larger than the anterior region.

    1. Anterior mandible

Characterized by fewer, coarser trabecular plates and larger marrow spaces.

    1. Posterior mandible

The trabecular pattern in the posterior mandible is quite variable, shows large marrow spaces and sparse trabeculation, especially inferiorly.

  1. Radiolucent normal anatomical landmarks of maxilla:
    • Intermaxillary suture.
    • Nasal fossa.
    • Incisive foramen also k/a nasopalatine or anterior palatine foramen.
    • Superior foramina of the Nasopalatine Canal.
    • Lateral fossa or incisive fossa.
    • Maxillary Sinus
    • Neurovascular canals in the lateral wall of the maxillary sinus.
    • Nasolacrimal canal.
  2. Radiopaque normal anatomical landmarks of maxilla:
    • Anterior nasal spine.
    • Floor of nasal fossa.
    • Nasal septum.
    • Soft tissue of the tip of the nose.
    • Borders of maxillary sinus.
    • A septum in the maxillary sinus.
    • Zygomatic process of the maxilla.
    • Nasolabial fold.
    • Pterygoid plates.
    • Hamular process.
  1. Radiolucent normal anatomical landmarks of mandible:
    • Symphysis in infants.
    • Mental fossa.
    • Mental Foramen.
    • Mandibular Canal
    • Nutrient Canals
    • Submandibular Gland Fossa
  2. Radiopaque normal anatomical landmarks of mandible:
    • Genial tubercles or mental spine.
    • Mental ridge.
    • Mylohyoid ridge.
    • External oblique Ridge.
    • Interior border of the mandible.
    • Coronoid process of mandible.
  1. Intermaxillary suture:   

                           A                                                                                             B

Figure 6: Intermaxillary suture

  • Appears on intraoral periapical radiographs as a thin radiolucent line in the midline between the two portions of the premaxilla.
  • It extends from the alveolar crest between the central incisors superiorly through the anterior nasal spine and continues posteriorly between the maxillary palatine processes to the posterior aspect of the hard palate. (Figure 6, A and B)
  1. Anterior Nasal Spine

                              A                                                                                               B

Figure 7: Anterior Nasal Spine and Nasal septum

  • Can be seen on periapical radiographs of the maxillary central incisors.
  • Appears an opaque V-shaped projection from the floor of the nasal fossa in the midline. (Figure:7 A).
  • When radiograph is taken with the x-ray beam directed in the sagittal plane, the relatively radiopaque nasal septum can be seen arising in the midline from the anterior nasal spine (Figure:7 B) 
  1. Nasal Fossa

Figure 8: Nasal fossa

  • Appears as radiolucent image on intraoral radiographs of the maxillary teeth, especially in central incisor projections. (Figure:8)
  1. Floor of nasal fossa

 Figure 9: Floor of nasal fossa

  • The floor of the nasal fossa projected high onto a maxillary canine radiograph.
  • The floor of the nasal fossa in periapical views of the posterior teeth superimposed on the maxillary sinus.
  • It appears as solid opaque line, frequently appears somewhat thicker than the adjacent sinus walls and septa.(Figure:9)
  1. Inferior conchae

  Figure 10: Inferior conchae

Nasal cavity contains the hazy shadows of the inferior conchae extending from the right and left lateral walls for varying distances toward the septum. (Figure:10)

  1. Incisive foramen (nasopalatine or anterior palatine foramen)

 Figure 11: Incisive foramen

  • It projected between the roots and in the region of the middle and apical thirds of the central incisors.
  • It may appear smoothly symmetric, with numerous forms, or very irregular, with a well demarcated or ill-defined border. (Figure:11)
  • The variability of its radiographic image is primarily due to:
  1. The differing angles at which the x-ray beam is directed for the maxillary central incisors.
  2. Some variability in its anatomic size. 
  1. Lateral walls of the nasopalatine canal

 Figure 12: Lateral walls of the nasopalatine canal

The lateral walls of the nasopalatine canal are seen occasionally in projection of the central incisors as a pair of radiopaque lines running vertically from the superior foramina of the nasopalatine canal to the incisive foramen.(Figure:12)

  1. Superior foramina of the Nasopalatine Canal

 Figure 13: Superior foramina of the Nasopalatine Canal 

  • Appears as two radiolucent areas above the apices of the central incisors in the floor of the nasal cavity near its anterior border and on both sides of the septum.
  • They are usually round or oval, although they make take a variety of outlines depending on the angle of projection.
  • Generally seen in maxillary occlusal projections.( Figure:13)
  1. Lateral fossa or incisive fossa

Figure 14: Lateral fossa or incisive fossa

  • It is a gentle depression in the maxilla near the apex of the lateral incisor.
  • On periapical projections of this region it may appear diffusely radiolucent.
  • Vitality test is best method to differentiate between lateral fossa and pathological lesion. (Figure:14) 
  1. Nose

 Figure 15: Soft tissue shadow of nose

Sometimes soft tissue of the tip of the nose appear as uniform, slightly opaque appearance with a sharp border in maxillary central and lateral incisors projection. (Figure:15)

  1. Nasolacrimal Canal

 Figure16: Nasolacrimal Canal

  • The nasal and maxillary bones form the nasolacrimal canal.
  • Occasionally visualized on periapical radiographs in the region above the apex of the canine, when steep vertical angulauon is used.
  • Routinely seen on maxillary occlusal projections.(Figure:16)
  1. Maxillary Sinus

 Figure17: Maxillary sinus

  • Air-containing cavity lined with mucous membrane (radiolucent).
  • Largest of paranasal sinuses and occupies virtually the entire body of maxilla.
  • Appear as three-sided pyramid, with its base the medial wall adjacent to the nasal cavity and its apex extending laterally into the zygomatic process of the maxilla. (Figure:17)
  1. Borders of the maxillary sinus

Figure 18: Borders of the maxillary sinus

Borders of the maxillary sinus appear on periapical radiographs as a thin, delicate, tenuous radiopaque line (Figure:18).

  1. Inverted Y (Y line of Ennis)

Figure 19: Anterior border of the maxillary sinus crosses the floor of the nasal fossa

On periapical radiographs of the canine, the floor of the sinus and nasal cavity are often superimposed and may be seen crossing one another, forming an inverted Y in the area.(Figure:19)

  1. Neurovascular canals or grooves

Figure 20: Neurovascular canals (arrows) in the lateral wall of the maxillary sinus.

  • Thin radiolucent lines of uniform width are found within the image of the maxillary sinus are known as shadows of neurovascular canals or grooves in the lateral sinus walls.
  • Neurovascular canals or grooves accommodate the posterior superior alveolar vessels, their branches, and the accompanying superior alveolar nerves.(Figure:20)
  1. Septa in maxillary sinus

Figure 21: A septum in the maxillary sinus formed by a low ridge of bone on the sinus wall.

  • One or several radiopaque lines traverse the image of the maxillary sinus k/a septa.
  • These septa represent folds of cortical bone projecting a few millimeters away from the floor and wall of the antrum. (Figure:21)  
  1. Zygomatic Process and Zygomatic Bone

     Figure 22: Zygomatic process of the maxilla.

  • Zygomatic process appears as a V shaped radiopaque line with its open end directed superiorly.
  • The enclosed rounded end is projected in the apical region of the first and second molars.
  • The size, width, and definition of the zygomatic process depend upon the angle at which the beam was projected. (Figure:22)
  1. Inferior portion of the zygomatic bone

 Figure 23: Inferior border of the zygomatic arch.

  • The inferior portion of the zygomatic bone extends posteriorly from the inferior border of the zygomatic process of the maxilla.
  • It appears as uniform gray or white radiopacity over the apices of the molars. (Figure:23)
  1. Nasolabial Fold

  Figure 24: Nasolabial fold extends across the canine-premolar region.

  • Appears as an oblique line demarcating a region that appears to be covered by a veil of slight radiopacity frequently traverses periapical radiographs of the premolar region.
  • The line of contrast is sharp, and the area of increased radiopacity is posterior to the line. (Figure:24)
  1. Pterygoid Plates

   Figure 25: Pterygoid plates located posterior to the maxillary tuberosity.

  • The medial and lateral pterygoid plates lie immediately posterior to the tuberosity of the maxilla.
  • Appear as a single radiopaque homogeneous shadow without any evidence of trabeculation. (Figure:25)
  1. Hamular process

Figure 26: Hamular process extends downward from the medial pterygoid plate.

From medial pterygoid plate hamular process can be seen extending inferiorly. (Figure:26)

  • In response to a loss of function the floor of the maxillary sinus extends toward the crest of the alveolar ridge.(Figure :27 A,B)

                             A                                                                                           B

Figure 27: Floor of the maxillary sinus extends toward the crest of the alveolar ridge in response to missing teeth

  1. Symphysis

Figure 28: Mandibular symphysis in a newborn infant. 

  • In infants it appears as radiolucent line through the midline of the jaw between the images of the forming deciduous central incisors.
  • This suture usually fuses by the end of the first year of life.
  • This radiolucency should be considered abnormal if it found in older individuals.(Figure:28)
  1. Genial Tubercles

                                 

                              A                                                                                             B

Figure 29: Genial tubercles.

  • Also called mental spine.
  • They are divided into a right and left prominence and a superior and inferior prominence.
  • They serve to attach the genioglossus muscles (at the superior tubercles) and the geniohyoid muscles (at the inferior tubercles) to the mandible.
  • On Mandibular occlusal radiographs it appears as one or more small projections.
  • It appear as a radiopaque mass (up to 3 to 4mm in diameter) in the midline below the incisor roots in periapical radiographs. (Figure:29 A,B)
  1. Lingual foramen

 

Figure 30: Lingual foramen.

Appears as a circular area of radiolucency surrounded by sclerotic border in the symphyseal region. (Figure:30) 

  1. Mental Ridge

Figure 31: Mental Ridge.

Appear as two radiopaque lines sweeping bilaterally forward and upward toward the midline. (Figure:31)

  1. Mental Fossa

Figure 32: Mental Fossa.

  • It is a depression on the labial aspect of the mandible extending laterally from the midline and above the mental ridge.
  • It appears as a radiolucent depression on the anterior surface of the mandible between the alveolar ridge and mental ridge. (Figure:32) 
  1. Mental Foramen

 Figure 33: Mental Foramen.

  • It conducts the mental vessels and nerves.
  • Appear as circular radiolucent area below premolar teeth on either side, midway between the upper and lower border of the body of mandible.
  • Location varies from distal of the canine to second premolar area.
  • Sometimes it may resemble periapical pathology. (Figure:33)
  1. Mandibular Canal

  Figure 34: Mandibular canal.

  • It appears as dark linear shadow with thin radiopaque superior and inferior borders cast by the lamella of bone that bounds the canal.
  • Sometimes the borders are seen only partially or not at all.
  • When the apices of the molars are projected over the canal, it appears as a missing lamina or a thickened PDL space. (Figure:34)
  1. Nutrient Canals

 Figure 35: Nutrient canals.

  • It carries neurovascular bundle and appear as radiolucent lines of fairly uniform width.
  • Commonly seen on mandibular periapical radiographs running vertically from the inferior dental canal directly to the apex of a tooth or into the interdental space between the mandibular incisors. (Figure:35)
  1. Mylohyoid Ridge

  Figure 36: Mylohyoid Ridge.

  • It serves as an attachment for the mylohyoid muscle.
  • Its radiographic image runs diagonally downward and forward from the area of the third molars to the premolar region, at approximately the level of the apices of the posterior teeth. (Figure:36)
  1. Submandibular Gland Fossa

 Figure 37: Submandibular gland fossa

  • On the lingual surface of the mandibular body, immediately below the mylohyoid ridge in the molar area, there is frequently a depression in the bone that is k/a submandibular gland fossa.
  • It appears as a radiolucent area with the sparse trabecular pattern.(Figure:37)
  1. External Oblique Ridge

 Figure 38: External Oblique Ridge

  • The external oblique ridge is a continuation of the anterior border of the mandibular ramus.
  • It appears as radiopaque line near the alveolar crest in the mandibular third molar region.(Figure:38)
  1. Inferior Border of the Mandible

  Figure 39: Inferior Border of the Mandible

Inferior Border of the Mandible appears in periapical projections as a dense, broad radiopaque band of bone. (Figure:39)

  1. Coronoid process of mandible

 Figure 40: Coronoid Process of mandible

The image of the coronoid process of the mandible is frequently seen on periapical radiographs of the maxillary molar region as a triangular radiopacity, with its apex directed superiorly and somewhat anteriorly, superimposed on the region of the third molar.(Figure:40 )

Radiopaque:

  • Silver amalgam
  • Gold or gold foils.
  • Stainless steel pins.
  • Gutta percha
  • Silver points.
  • Composite restorations containing particles of barium glass.
  • Zinc oxide euginol.
  • Metapex (calcium hydroxide-iodoform).

Radiolucent

  • Silicate restorations
  • Porcelain appears radiolucent over a metal coping.
  • Composite restorations may be radiolucent.
  • Acrylic restorations.
  • This visual phenomenon first described by Erns Mach in 1865.
  • An optical illusion which produces fictious radiolucent areas in dentinal peaks bounded by occlusal and proximal enamel seen especially in premolar area and molar area. The overlapping shadow of the alveolar process creates a mach band effect resulting in apparent radiolucent region in the crowns of the premolar and molar that may mimic carious lesion.

Figure 41: Bitewing image showed mach band effects on distal surface of maxillary first premolar and mesial surface of mandibular first molar.

  1. Goaz PW, White SC Normal radiographic anatomy. Book of oral radiology, principles and interpretation 2nd edition 1990;174-99.
  2. White SC, Pharaoh MJ Normal radiographic anatomy. Book of oral radiology principles and interpretations 6th edition 2009;166-90.
  3. Langlang OE, Langlais RP Normal intraoral radiographic anatomy Book of principles of dental imaging 1st edition 1997;331-42.
  4. Caries Interpretation: Cervical Burnout. Available from: http://drgstoothpix.com/2014/12/31/caries-interpretation-cervical-burnout/
  5. Lamina-Dura Available from: http://dentstudy.com/lamina-dura/
  6. Diagnosing the need for root canal treatment using x-rays. Available from: https://www.animated-teeth.com/root_canal/root-canal-x-ray-diagnosis.htm
  7. Secgin CK, Gulsahi A, Arhun N Diagnostic Challange: Instances Mimicking a Proximal Carious Lesion Detected by Bitewing Radiography OHDM 2016;15:1-5.
  • Thicker, more mineralized or denser tissue appears radiopaque.
  • Less dense, thinner or demineralized tissue appears radiolucent.
  • Term radiolucent (dark/black) or radiopaque (light/white) used in plain radiographic image like intra oral, panoramic or extra oral radiographs.  

Figure1: Radiographic appearance of enamel, dentin and pulp

  1. Enamel
    • Most radiopaque.
    • Covers the coronal portion of tooth.
    • The line of demarcation between enamel and dentine is k/a dentinoenamel junction (DEJ).
    • Caries is most common disease affecting the enamel. (Figure:1)
  2. Dentin
    • Less radiopaque- white.
    • Dentin appears less dense or lighter than the underlying pulp but darker than the overlying enamel.
    • Caries is most common disease affecting the dentin extended through the enamel. (Figure:1)
  3. Pulp
    • The pulp tissue is not visible radiographically.
    • The space that contains the pulp is visible and forms the most radiolucent (dark) portions of the tooth.
    • The pulp spaces decrease in size with advancing age.
    • The root canal space tapers gently toward the apex.
    • The apical foramen is the terminal portion of the root canal space at the apex of the tooth through which the vital elements of the tooth pass.
    • At the end of a developing; tooth root the pulp canal diverges and the walls of the toot rapidly taper to a knife edge. (Figure:1)

Figure 2: Cervical burnout

The constricted cervical neck of the tooth, the area between the crown and the root, absorbs less x-ray energy than the areas above and below it. This is because of the presence of enamel above and the alveolar bone covering the root of this tooth below the cervical neck. It results in a radiolucent band running across the cervical neck of anterior teeth and a triangular, wedge shaped radiolucency at the inter-proximal cervical neck of the posterior teeth. This is called cervical burnout (Figure:2).

  • Root caries appears as saucer- shaped or having a cupped – out appearance. Root caries is usually located in the region of the interproximal cementoenamel junction. It does not usually involve the enamel; it may undermine the enamel by spreading underneath it.
  • Cervical burnout is seen in the cervical region of the teeth as a radiolucent triangular area on the interproximal surfaces of the posterior teeth and as radiolucent band on the anterior teeth.
  • Lamina dura.
  • Alveolar crest.
  • Periodontal ligament space.
  • Cancellous bone.

Figure 3: Lamina dura

A radiograph of sound teeth in a dental arch demonstrates that the tooth socket is bounded by a thin radiopaque layer of dense bone. Its name, lamina dura (“hard layer”) is derived from its radiographic appearance. (Figure: 3)

The name lamina dura (or alveolus) is applied to the thin layer of dense cortical bone (the so–called cribriform plate or alveolar bone proper) which lines the normal tooth socket.

It radiographic appearance is caused by the fact that x-ray beam passes tangentially through many times the thickness of thin bony wall which results in its observed attenuation (egg-shell effect).

  • When the x-ray beam is directed through a relatively long expanse of the structure, the lamina dura appears radiopaque and well defined.
  • When the beam is directed more obliquely, however, the lamina dura appears more diffuse and may not be discernible.
  1. Common Normal Variations
    • Apex of Maxillary Canine.
    • Rotated Tooth.
    • Maxillary Premolars – before maturation.
    • Projection over the maxillary sinus.
    • Projection over the mandibular Canal.
    • Projection over the mental foramen.
  2. Pathologic
    • Inflammatory periapical diseases.
    • Peri-apical granuloma.
    • Radicular cyst.
    • Simple bone cyst.
    • Peri-apical cemental dysplasia.
    • Osteomyelitis
  3. Uncommon
    • Malignant Tumor.
    • Fibrous Histiocytoma.
    • Histiocytosis –X.
  1. Common
    • Idiopathic.
    • Paget Disease of Bone.
    • Leukemia.
  2. Uncommon
    • Metastatic Malignancy (especially breast).
    • Hyperparathyroidism.
    • Multiple Myeloma.
    • Osteomalacia.
    • Rickets (Including Vitamin D resistant Rickets).
    • Cushing syndrome.
    • Osteomalacia.
    • Rickets (Including Vitamin D resistant Rickets).
    • Postmenopausal Osteoporosis.
    • Renal Acidosis.
    • Acromegaly.
    • Oxalosis.
    • Hypervitaminosis D.
    • Hypovitaminosis C.
    • Systemic Sclerosis (Scleroderma).
    • Hypophosphatasia.

Teeth in heavy occlusion.

Thinner and less dense around teeth not subjected to occlusal function.

Figure 4: Double Lamina dura

The image of a double lamina dura appears when mesial or distal surfaces of roots present two elevations in the path of the x-ray beam. (Figure: 4)

  • Alveolar crest is the gingival margin of the alveolar process that extends between the teeth is apparent on radiographs as a radiopaque line.
  • Normal level of alveolar crest is when it is not more than 1.5mm from the cementoenamel junction of the adjacent teeth.
  • In the anterior region the crest is reduced to only a point of bone between the close-set incisors.
  • Posteriorly it is flat, aligned parallel with and slightly below a line connecting the cementoenamel junctions of the adjacent teeth.
  • The crest of the bone is continuous with the lamina dura and forms a sharp angle with it.
  • Rounding of these sharp junctions is indicative of periodontal disease.

Figure 5: Normal appearance of periodontal ligament space

  • It is a soft connective tissue between the inner wall of the alveolar socket and the roots of the teeth.
  • It consists of collagen bands (mostly type I collagen) connecting the cementum of teeth to the gingivae and alveolar bone.
  • Fibroblasts are the main cells in the PDL, which form, maintain, and repair the alveolar bone and cementum.
  • Radiographically, the PDL is seen as a radiolucent space between the lamina dura and the tooth root.
  • The normal width of the PDL ranges from 0.15 mm to 0.21 mm, which may decrease with age.
  • Orthodontic movement of teeth results in PDL widening, but the lamina dura remains intact.(Figure:5)
  1. Traumatic causes
    • Occlusal/orthodontic trauma.
    • Radiation-induced bone defect.
  2. Infectious causes
    • Periodontal disease/periodontitis.
    • Pulpo-periapical lesions.
    • Osteomyelitis.
  3. Neoplastic lesions of the jawbones
    • Osteosarcoma.
    • Chondrosarcoma.
    • Non-Hodgkin lymphoma (NHL).
  4. Systemic causes
    • Progressive systemic sclerosis.
    • Bisphosphonate-related osteonecrosis.

The alveolar bone is divided into:

  1. Alveolar bone proper (compact bone).
  2. Supporting alveolar bone (cortical and trabecular bone).

The trabecular bone (cancellous bone) is located between alveolar bone proper and plates of cortical bone.

  • Also k/a trabecular bone or spongiosa that lies between the cortical plates in both jaws.
  • It is composed of thin radiopaque plates and rods (trabeculae) surrounding many small radiolucent pockets of marrow.
  1. Anterior maxilla
  2. Thin and numerous, forming a fine, granular, dense pattern and marrow spaces are consequently small and relatively numerous.
  3. Posterior maxilla
  4. Trabeculae are typically thin, and numerous, forming a fine, granular, dense pattern, and the marrow spaces are consequently slightly larger than the anterior region.
  1. Anterior mandible
  2. Characterized by fewer, coarser trabecular plates and larger marrow spaces.
  3. Posterior mandible
  4. The trabecular pattern in the posterior mandible is quite variable, shows large marrow spaces and sparse trabeculation, especially inferiorly.
  1. Radiolucent normal anatomical landmarks of maxilla:
    • Intermaxillary suture.
    • Nasal fossa.
    • Incisive foramen also k/a nasopalatine or anterior palatine foramen.
    • Superior foramina of the Nasopalatine Canal.
    • Lateral fossa or incisive fossa.
    • Maxillary Sinus
    • Neurovascular canals in the lateral wall of the maxillary sinus.
    • Nasolacrimal canal.
  2. Radiopaque normal anatomical landmarks of maxilla:
    • Anterior nasal spine.
    • Floor of nasal fossa.
    • Nasal septum.
    • Soft tissue of the tip of the nose.
    • Borders of maxillary sinus.
    • A septum in the maxillary sinus.
    • Zygomatic process of the maxilla.
    • Nasolabial fold.
    • Pterygoid plates.
    • Hamular process.
  1. Radiolucent normal anatomical landmarks of mandible:
    • Symphysis in infants.
    • Mental fossa.
    • Mental Foramen.
    • Mandibular Canal
    • Nutrient Canals
    • Submandibular Gland Fossa
  2. Radiopaque normal anatomical landmarks of mandible:
    • Genial tubercles or mental spine.
    • Mental ridge.
    • Mylohyoid ridge.
    • External oblique Ridge.
    • Interior border of the mandible.
    • Coronoid process of mandible.
  1. Intermaxillary suture:   

           A                   B

Figure 6: Intermaxillary suture

  • Appears on intraoral periapical radiographs as a thin radiolucent line in the midline between the two portions of the premaxilla.
  • It extends from the alveolar crest between the central incisors superiorly through the anterior nasal spine and continues posteriorly between the maxillary palatine processes to the posterior aspect of the hard palate. (Figure 6, A and B)
  1. Anterior Nasal Spine

          A                    B

Figure 7: Anterior Nasal Spine and Nasal septum

  • Can be seen on periapical radiographs of the maxillary central incisors.
  • Appears an opaque V-shaped projection from the floor of the nasal fossa in the midline. (Figure:7 A).
  • When radiograph is taken with the x-ray beam directed in the sagittal plane, the relatively radiopaque nasal septum can be seen arising in the midline from the anterior nasal spine (Figure:7 B) 
  1. Nasal Fossa

Figure 8: Nasal fossa

  • Appears as radiolucent image on intraoral radiographs of the maxillary teeth, especially in central incisor projections. (Figure:8)
  1. Floor of nasal fossa

 Figure 9: Floor of nasal fossa

  • The floor of the nasal fossa projected high onto a maxillary canine radiograph.
  • The floor of the nasal fossa in periapical views of the posterior teeth superimposed on the maxillary sinus.
  • It appears as solid opaque line, frequently appears somewhat thicker than the adjacent sinus walls and septa.(Figure:9)
  1. Inferior conchae

  Figure 10: Inferior conchae

Nasal cavity contains the hazy shadows of the inferior conchae extending from the right and left lateral walls for varying distances toward the septum. (Figure:10)

  1. Incisive foramen (nasopalatine or anterior palatine foramen)

 Figure 11: Incisive foramen

  • It projected between the roots and in the region of the middle and apical thirds of the central incisors.
  • It may appear smoothly symmetric, with numerous forms, or very irregular, with a well demarcated or ill-defined border. (Figure:11)
  • The variability of its radiographic image is primarily due to:
  1. The differing angles at which the x-ray beam is directed for the maxillary central incisors.
  2. Some variability in its anatomic size. 
  1. Lateral walls of the nasopalatine canal

 Figure 12: Lateral walls of the nasopalatine canal

The lateral walls of the nasopalatine canal are seen occasionally in projection of the central incisors as a pair of radiopaque lines running vertically from the superior foramina of the nasopalatine canal to the incisive foramen.(Figure:12)

  1. Superior foramina of the Nasopalatine Canal

 Figure 13: Superior foramina of the Nasopalatine Canal 

  • Appears as two radiolucent areas above the apices of the central incisors in the floor of the nasal cavity near its anterior border and on both sides of the septum.
  • They are usually round or oval, although they make take a variety of outlines depending on the angle of projection.
  • Generally seen in maxillary occlusal projections.( Figure:13)
  1. Lateral fossa or incisive fossa

Figure 14: Lateral fossa or incisive fossa

  • It is a gentle depression in the maxilla near the apex of the lateral incisor.
  • On periapical projections of this region it may appear diffusely radiolucent.
  • Vitality test is best method to differentiate between lateral fossa and pathological lesion. (Figure:14) 
  1. Nose

 Figure 15: Soft tissue shadow of nose

Sometimes soft tissue of the tip of the nose appear as uniform, slightly opaque appearance with a sharp border in maxillary central and lateral incisors projection. (Figure:15)

  1. Nasolacrimal Canal

 Figure16: Nasolacrimal Canal

  • The nasal and maxillary bones form the nasolacrimal canal.
  • Occasionally visualized on periapical radiographs in the region above the apex of the canine, when steep vertical angulauon is used.
  • Routinely seen on maxillary occlusal projections.(Figure:16)
  1. Maxillary Sinus

 Figure17: Maxillary sinus

  • Air-containing cavity lined with mucous membrane (radiolucent).
  • Largest of paranasal sinuses and occupies virtually the entire body of maxilla.
  • Appear as three-sided pyramid, with its base the medial wall adjacent to the nasal cavity and its apex extending laterally into the zygomatic process of the maxilla. (Figure:17)
  1. Borders of the maxillary sinus

Figure 18: Borders of the maxillary sinus

Borders of the maxillary sinus appear on periapical radiographs as a thin, delicate, tenuous radiopaque line (Figure:18).

  1. Inverted Y (Y line of Ennis)

Figure 19: Anterior border of the maxillary sinus crosses the floor of the nasal fossa

On periapical radiographs of the canine, the floor of the sinus and nasal cavity are often superimposed and may be seen crossing one another, forming an inverted Y in the area.(Figure:19)

  1. Neurovascular canals or grooves

Figure 20: Neurovascular canals (arrows) in the lateral wall of the maxillary sinus.

  • Thin radiolucent lines of uniform width are found within the image of the maxillary sinus are known as shadows of neurovascular canals or grooves in the lateral sinus walls.
  • Neurovascular canals or grooves accommodate the posterior superior alveolar vessels, their branches, and the accompanying superior alveolar nerves.(Figure:20)
  1. Septa in maxillary sinus

Figure 21: A septum in the maxillary sinus formed by a low ridge of bone on the sinus wall.

  • One or several radiopaque lines traverse the image of the maxillary sinus k/a septa.
  • These septa represent folds of cortical bone projecting a few millimeters away from the floor and wall of the antrum. (Figure:21)  
  1. Zygomatic Process and Zygomatic Bone

     Figure 22: Zygomatic process of the maxilla.

  • Zygomatic process appears as a V shaped radiopaque line with its open end directed superiorly.
  • The enclosed rounded end is projected in the apical region of the first and second molars.
  • The size, width, and definition of the zygomatic process depend upon the angle at which the beam was projected. (Figure:22)
  1. Inferior portion of the zygomatic bone

 Figure 23: Inferior border of the zygomatic arch.

  • The inferior portion of the zygomatic bone extends posteriorly from the inferior border of the zygomatic process of the maxilla.
  • It appears as uniform gray or white radiopacity over the apices of the molars. (Figure:23)
  1. Nasolabial Fold

  Figure 24: Nasolabial fold extends across the canine-premolar region.

  • Appears as an oblique line demarcating a region that appears to be covered by a veil of slight radiopacity frequently traverses periapical radiographs of the premolar region.
  • The line of contrast is sharp, and the area of increased radiopacity is posterior to the line. (Figure:24)
  1. Pterygoid Plates

   Figure 25: Pterygoid plates located posterior to the maxillary tuberosity.

  • The medial and lateral pterygoid plates lie immediately posterior to the tuberosity of the maxilla.
  • Appear as a single radiopaque homogeneous shadow without any evidence of trabeculation. (Figure:25)
  1. Hamular process

Figure 26: Hamular process extends downward from the medial pterygoid plate.

From medial pterygoid plate hamular process can be seen extending inferiorly. (Figure:26)

  • In response to a loss of function the floor of the maxillary sinus extends toward the crest of the alveolar ridge.(Figure :27 A,B)

          A                    B

Figure 27: Floor of the maxillary sinus extends toward the crest of the alveolar ridge in response to missing teeth

  1. Symphysis

Figure 28: Mandibular symphysis in a newborn infant. 

  • In infants it appears as radiolucent line through the midline of the jaw between the images of the forming deciduous central incisors.
  • This suture usually fuses by the end of the first year of life.
  • This radiolucency should be considered abnormal if it found in older individuals.(Figure:28)
  1. Genial Tubercles

           A                   B

Figure 29: Genial tubercles.

  • Also called mental spine.
  • They are divided into a right and left prominence and a superior and inferior prominence.
  • They serve to attach the genioglossus muscles (at the superior tubercles) and the geniohyoid muscles (at the inferior tubercles) to the mandible.
  • On Mandibular occlusal radiographs it appears as one or more small projections.
  • It appear as a radiopaque mass (up to 3 to 4mm in diameter) in the midline below the incisor roots in periapical radiographs. (Figure:29 A,B)
  1. Lingual foramen

 

Figure 30: Lingual foramen.

Appears as a circular area of radiolucency surrounded by sclerotic border in the symphyseal region. (Figure:30) 

  1. Mental Ridge

Figure 31: Mental Ridge.

Appear as two radiopaque lines sweeping bilaterally forward and upward toward the midline. (Figure:31)

  1. Mental Fossa

Figure 32: Mental Fossa.

  • It is a depression on the labial aspect of the mandible extending laterally from the midline and above the mental ridge.
  • It appears as a radiolucent depression on the anterior surface of the mandible between the alveolar ridge and mental ridge. (Figure:32) 
  1. Mental Foramen

 Figure 33: Mental Foramen.

  • It conducts the mental vessels and nerves.
  • Appear as circular radiolucent area below premolar teeth on either side, midway between the upper and lower border of the body of mandible.
  • Location varies from distal of the canine to second premolar area.
  • Sometimes it may resemble periapical pathology. (Figure:33)
  1. Mandibular Canal

  Figure 34: Mandibular canal.

  • It appears as dark linear shadow with thin radiopaque superior and inferior borders cast by the lamella of bone that bounds the canal.
  • Sometimes the borders are seen only partially or not at all.
  • When the apices of the molars are projected over the canal, it appears as a missing lamina or a thickened PDL space. (Figure:34)
  1. Nutrient Canals

 Figure 35: Nutrient canals.

  • It carries neurovascular bundle and appear as radiolucent lines of fairly uniform width.
  • Commonly seen on mandibular periapical radiographs running vertically from the inferior dental canal directly to the apex of a tooth or into the interdental space between the mandibular incisors. (Figure:35)
  1. Mylohyoid Ridge

  Figure 36: Mylohyoid Ridge.

  • It serves as an attachment for the mylohyoid muscle.
  • Its radiographic image runs diagonally downward and forward from the area of the third molars to the premolar region, at approximately the level of the apices of the posterior teeth. (Figure:36)
  1. Submandibular Gland Fossa

 Figure 37: Submandibular gland fossa

  • On the lingual surface of the mandibular body, immediately below the mylohyoid ridge in the molar area, there is frequently a depression in the bone that is k/a submandibular gland fossa.
  • It appears as a radiolucent area with the sparse trabecular pattern.(Figure:37)
  1. External Oblique Ridge

 Figure 38: External Oblique Ridge

  • The external oblique ridge is a continuation of the anterior border of the mandibular ramus.
  • It appears as radiopaque line near the alveolar crest in the mandibular third molar region.(Figure:38)
  1. Inferior Border of the Mandible

  Figure 39: Inferior Border of the Mandible

Inferior Border of the Mandible appears in periapical projections as a dense, broad radiopaque band of bone. (Figure:39)

  1. Coronoid process of mandible

 Figure 40: Coronoid Process of mandible

The image of the coronoid process of the mandible is frequently seen on periapical radiographs of the maxillary molar region as a triangular radiopacity, with its apex directed superiorly and somewhat anteriorly, superimposed on the region of the third molar.(Figure:40 )

Radiopaque:

  • Silver amalgam
  • Gold or gold foils.
  • Stainless steel pins.
  • Gutta percha
  • Silver points.
  • Composite restorations containing particles of barium glass.
  • Zinc oxide euginol.
  • Metapex (calcium hydroxide-iodoform).

Radiolucent

  • Silicate restorations
  • Porcelain appears radiolucent over a metal coping.
  • Composite restorations may be radiolucent.
  • Acrylic restorations.
  • This visual phenomenon first described by Erns Mach in 1865.
  • An optical illusion which produces fictious radiolucent areas in dentinal peaks bounded by occlusal and proximal enamel seen especially in premolar area and molar area. The overlapping shadow of the alveolar process creates a mach band effect resulting in apparent radiolucent region in the crowns of the premolar and molar that may mimic carious lesion.

Figure 41: Bitewing image showed mach band effects on distal surface of maxillary first premolar and mesial surface of mandibular first molar.

  1. Goaz PW, White SC Normal radiographic anatomy. Book of oral radiology, principles and interpretation 2nd edition 1990;174-99.
  2. White SC, Pharaoh MJ Normal radiographic anatomy. Book of oral radiology principles and interpretations 6th edition 2009;166-90.
  3. Langlang OE, Langlais RP Normal intraoral radiographic anatomy Book of principles of dental imaging 1st edition 1997;331-42.
  4. Caries Interpretation: Cervical Burnout. Available from: http://drgstoothpix.com/2014/12/31/caries-interpretation-cervical-burnout/
  5. Lamina-Dura Available from: http://dentstudy.com/lamina-dura/
  6. Diagnosing the need for root canal treatment using x-rays. Available from: https://www.animated-teeth.com/root_canal/root-canal-x-ray-diagnosis.htm
  7. Secgin CK, Gulsahi A, Arhun N Diagnostic Challange: Instances Mimicking a Proximal Carious Lesion Detected by Bitewing Radiography OHDM 2016;15:1-5.
error: Content is protected !!