Chapter 27:Normal Anatomy: Intraoral Images

Chapter 27

1. Normal Anatomy: Intraoral Images Chapter 27

2. Introduction Purpose To review the normal anatomy of the maxilla and mandible as viewed on the skull To describe the normal anatomic landmarks seen on intraoral images

3. Types of Bone Cortical bone (Compact Bone) The dense outer layer of bone Appears radiopaque on an image Cancellous bone The soft, spongy bone located between two layers of dense cortical bone Appears primarily radiolucent Trabeculae appear radiopaque, marrow spaces appear radiolucent

4. Cortical bone and cancellous bone

5. Cortical bone

6. Cancellous bone

7. Prominences of Bone Appear radiopaque on dental images

8. Process: Marked prominence or projection Coronoid process

9. Ridge: Linear prominence or projection External oblique ridge

10. Spine: Sharp, thornlike projection Anterior nasal spine

11. Tubercle: Small bump or nodule Mental tubercles

12. Tuberosity: Rounded prominence Maxillary Tuberosity

13. Spaces and Depressions in Bone Appear radiolucent on dental images

14. Canal: Tubelike passageway through bone that contains nerves and blood vessels Mandibular Canal

15. Foramen: Opening or hole that permits the passage of nerves and blood vessels Mental foramen

16. Fossa: Broad, shallow, scooped-out, or depressed area Submandibular fossa

17. Sinus: Hollow space, cavity, or recess

18. Miscellaneous Terms Septum A bony wall or partition that divides two spaces or cavities Radiopaque Nasal septum

19. Miscellaneous terms Suture An immovable joint representing a line of union between adjoining bones of the skull A thin radiolucent line

20. Bony Landmarks of the Maxilla The upper jaw is composed of two paired bones, the maxillae. The paired maxillae meet at the midline of the face The paired maxillae are often referred to as one single bone, the maxilla All of the bones in the face articulate with the maxilla The lower floor of the maxilla supports the upper teeth Forms the: Floor of the orbit of the eye Sides and floor of the nasal cavities Hard palate

21. Incisive Foramen (Nasopalatine Foramen) Description An opening or hole in bone that is located at the midline of the anterior portion of the hard palate directly posterior to the maxillary central incisors Appearance A small ovoid or round radiolucent area located between the roots of the maxillary central incisors

22. Superior Foramina of the Incisive Canal Description Two tiny openings or holes in bone that are located on the floor of the nasal cavity Join together to form the incisive canal Appearance Two small round radiolucencies located superior to the apices of the maxillary central incisors

23. Median Palatal Suture Description The immovable joint between the two palatine processes of the maxilla Appearance A thin radiolucent line between the maxillary central incisors

24. Lateral Fossa Description A smooth, depressed area of the maxilla located just inferior and medial to the infraorbital foramen between the canine and lateral incisors Appearance A radiolucent area between the maxillary canine and lateral incisors

25. Nasal Cavity Description A pear-shaped compartment of bone located superior to the maxilla The inferior portion is formed by the palatal processes of the maxilla and the horizontal portions of the palatine bones. Appearance A large radiolucent area above the maxillary incisors

26. Nasal Septum Description A vertical bony wall or partition that divides the nasal cavity into the right and left nasal fossae Formed by the vomer and a portion of the ethmoid bone and cartilage Appearance A vertical radiopaque partition that divides the nasal cavity

27. Floor of the Nasal Cavity Description A bony wall formed by the palatal processes of the maxilla and the horizontal portions of the palatine bones Appearance A dense radiopaque band of bone above the maxillary incisors

28. Anterior Nasal Spine Description A sharp projection of the maxilla located at the anterior and inferior portion of the nasal cavity Appearance A V -shaped radiopaque area located at the intersection of the floor of the nasal cavity and the nasal septum

29. Inferior Nasal Conchae Description Wafer-thin, curved plates of bone that extend from the lateral walls of the nasal cavity Conchae means shell shaped or scroll shaped. Appearance A diffuse radiopaque mass or projection within the nasal cavity

30. Maxillary Sinus Description Paired cavities or compartments of bone located within the maxilla Located above the maxillary premolar and molar teeth Appearance A radiolucent area located above the apices of the maxillary premolars and molars

31. Septa Within the Maxillary Sinus Description Bony walls or partitions that appear to divide the maxillary sinus into compartments Appearance Radiopaque lines within the maxillary sinus Presence and number vary depending on the anatomy of the individual.

32. Nutrient Canals Within the Maxillary Sinus Description Tiny, tubelike passageways through bone that contain blood vessels and nerves Appearance A narrow radiolucent band bounded by two thin radiopaque lines

33. Inverted Y Description The intersection of the maxillary sinus and the nasal cavity Appearance A radiopaque upside-down Y formed by the intersection of the lateral wall of the nasal fossa and the anterior border of the maxillary sinus Located above the maxillary canine

34. Maxillary Tuberosity Description A rounded prominence of bone that extends posterior to the third molar region Appearance A radiopaque bulge distal to the third molar region

35. Hamulus Description A small hooklike projection of bone extending from the medial pterygoid plate of the sphenoid bone Appearance A radiopaque hooklike projection posterior to the maxillary tuberosity area

36. Zygomatic Process of the Maxilla Description A bony projection of the maxilla that articulates with the zygoma or malar bone (cheekbone) Appearance A J - or U -shaped radiopacity located superior to the maxillary first molar region

37. Zygoma Description Articulates with the zygomatic process of the maxilla Also knows as the cheekbone, malar bone, or zygomatic bone Appearance A diffuse, radiopaque band extending posteriorly from the zygomatic process of the maxilla

38. The Mandible The largest and strongest bone of the face The mandible is the only moveable bone of the face. Divided into three main parts: Ramus Body Alveolar process

39. Ramus: Vertical portion found posterior to the third molar

40. Body: Horizontal U-shaped portion from ramus to ramus

41. Alveolar process: Encases and supports the teeth

42. Bony Landmarks of the Mandible

43. Genial Tubercles Description Tiny bumps of bone on the lingual aspect of the mandible Attachment sites for genioglossus and geniohyoid muscles Appearance A ring-shaped radiopacity below the apices of the mandibular incisors

44. Lingual Foramen Description A tiny opening or hole in bone located on the internal surface of the mandible Appearance A small radiolucent dot inferior to the apices of the mandibular incisors

45. Nutrient Canals Description Tubelike passageways through bone containing nerves and blood vessels that supply the teeth Most often seen in anterior mandible Appearance Vertical radiolucent lines readily seen in areas of thin bone

46. Mental Ridge Description A linear prominence of cortical bone located on the external surface of the anterior portion of the mandible Appearance A thick radiopaque band that extends from the premolar region to the incisor region Often appears superimposed over the mandibular anterior teeth

47. Mental Fossa Description A scooped-out, depressed area of bone located on the external surface of the anterior mandible Appearance A radiolucent area above the mental ridge The radiographic appearance of the mental fossa varies and is determined by the thickness of the bone in the anterior region of the mandible.

48. Mental Foramen Description An opening or hole in bone located on the external surface of the mandible in the region of the mandibular premolars Appearance A small ovoid or round radiolucent area located in the apical region of the mandibular premolars Frequently misdiagnosed as a periapical lesion

49. Mandibular Canal Description A tubelike passageway through bone that travels the length of the mandible Houses the inferior alveolar nerve and blood vessels Appearance A radiolucent band outlined by two thin radiopaque lines that represent the cortical walls of the canal

50. Mylohyoid Ridge Description A linear prominence of bone located on the internal surface of the mandible Appearance A dense radiopaque band that extends downward and forward from the molar region May appear to be continuous with the internal oblique ridge.

51. External Oblique Ridge (or line) Description A linear prominence of bone located on the external surface of the body of the mandible Appearance A radiopaque band extending downward and forward from the anterior border of the ramus of the mandible; typically ends in the mandibular third molar region

52. Anterior Border of the Ramus Description Anterior border of the ramus extends vertically downward from the coronoid process to the external oblique ridge Appearance On a molar bite-wing image, the descending ramus of the mandible may be seen as a slightly radiopaque vertical band posterior to the maxillary and mandibular molars

53. Submandibular Fossa Description A scooped-out, depressed area of bone located on the internal surface of the mandible inferior to the mylohyoid ridge Appearance A radiolucent area in the molar region below the mylohyoid ridge May be slightly more radiolucent than the adjacent bone on some periapical images. The submandibular salivary gland is located in the submandibular fossa

54. Coronoid Process Description A marked prominence of bone on the anterior ramus of the mandible Radiographic appearance A triangular radiopacity superimposed over, or inferior to, the maxillary tuberosity region It serves as an attachment site for one of the muscles of mastication.

55. Tooth Structure Enamel The outermost radiopaque layer of the crown of a tooth Dentin Comprises most of the tooth structure, not as radiopaque as enamel Dentinoenamel junction (DEJ) The junction between dentin and enamel Pulp cavity A pulp chamber and pulp canals

56. Supporting Structures Anatomy of alveolar bone Lamina dura Alveolar crest Periodontal ligament space Alveolar bone is composed of dense cortical bone and cancellous bone. Shape and density of alveolar bone Anterior regions Posterior regions

57. Lamina Dura Description The wall of the tooth socket Made of dense cortical bone Appearance A dense radiopaque line that surrounds the root of a tooth

58. Alveolar Crest Description The most coronal portion of the alveolar bone found between teeth Made of dense cortical bone and is continuous with the lamina dura. Appearance Appears radiopaque, typically 1.5 to 2.0 mm below the cementoenamel junction

59. Periodontal Ligament Space Description The space between the root of the tooth and the lamina dura Appearance A thin radiolucent line around the root of a tooth

60. Shape and Density of Alveolar Bone Anterior regions A normal alveolar crest appears pointed and sharp between the teeth. The alveolar crest appears as a dense radiopaque line in the anterior region Alveolar crest fibers run from the crest of the alveolar bone to the cementum in the region of the CEJ. Posterior regions A normal alveolar crest appears flat and smooth between the teeth. The alveolar crest appears less dense and less radiopaque than the alveolar crest seen in the anterior region.

61. Anterior region

62. Posterior region

63. Primary and Mixed Dentitions Primary teeth begin to erupt at the age of 6 months. By the age of 3, all 20 primary teeth should be erupted and functioning.

64. Primary Dentition Also known as “deciduous dentition” Composed of 10 maxillary and 10 mandibular teeth Eventually shed and replaced by permanent teeth Play an integral role in the formation of the mandible and maxilla

65. Primary Dentition (Cont.)

66. Mixed Dentition Between the ages of 6 and 12, mixed dentition (both primary and permanent teeth) is seen in the oral cavity. Can produce a variety of dental concerns Periapical, bite-wing, and occlusal imaging techniques can be used to examine the primary and mixed dentitions.

67. Questions?