Alveolar bone

For my dental students

1. Alveolar Bone Dr / Hesham Dameer

2. The students have to know 1- Definition of alveolar bone 2- Alveolar bone components 3- Alveolar bone development 4- Alveolar bone structure & its clinical applications 5- Alveolar bone appearance in x-ray 6- Physiologic & orthodontic movements related to the alveolar bone

3. Alveolar bone is that part of the maxilla and mandible that contains the alveoli or sockets of the teeth and supports the teeth. Definition The alveolar socket is the cavity within the alveolar bone in which the root of the tooth is held by the periodontal ligament. If the teeth are lost the alveolar process disappears

4. The alveolar bone between the roots of adjacent teeth is known as the Interdental Septum. The alveolar bone between the roots of multi-rooted teeth is called the Inter-radicular Septum .

5. Interdental Septum. Inter-radicular Septum

6. A lveolar bone & the basal bone

7. Anatomically no boundary exists between the alveolar bone & the basal bone (body of the mandible and maxilla). An imaginary line at the root apices separates the alv. bone & the basal bone of the jaws. Alv. Bone Basal Bone

8. The alv. bone develops with the formation and the eruption of teeth, when the teeth are congenitally messing (anodontia), the alv. bone do not develop at all. The maintenance of the alv. bone is dependent on the presence of the teeth. When the teeth are lost, it gradually resorbs. The alv. bone is a functional bone

9. Near the end of the 2 nd month IUL . The outer and inner plates of the body of the maxilla and mandible grow in a vertical direction forming a groove that is opened towards the of the oral cavity. The tooth germs are contained in this groove. Gradually bony septa develop between the adjacent tooth germs. Development

10. The actual alveolar process formation is associated with the root formation & the eruption process. With the root formation the bony crypt is transformed into socket. In fetal life the alveolar bone is formed, like the rest of the skeleton, of woven bone .

11. Structure of the alveolar process Adult alveolar process is composed of 2 parts : 1. Alveolar bone prope 2. Supporting bone.

12. Macro-anatomy Alveolar bone proper Supporting alveolar bone Inner & outer cortical plates Supporting Spongy bone ALVEOLAR PROCESS

13. The alveolar bone proper is a thin layer of bone that surrounds the root and gives attachment to the principal PDL fibers . It is perforated by numerous minute foramina ( Volkman's Canals) that carry the BV & nerves into the periodontal ligament and that is why it is called the cribriform plate. The term lamina dura (dura hard) is given to this layer of bone from its dense radiopaque appearance in X-ray 1- The alveolar bone proper

14. Cribriform Plate

15. Lamina Dura

16. The alveolar bone proper is made up of: Bundle bone adjacent to the PDL where the principal fibers are attached (bone of attachment) Compact bone which consists of superficial parallel lamellae & deeper portions made up of Haversian system Histology of the alveolar bone proper

17. High power Bundle bone Compact bone Bundles of the principal fibers are inserted into the bone as Sharpey's fibers

18. The bundle bone is the bone of attachment. It varies in thickness. According to the functional demands Always its thicker distally than mesially Mesial Distal ? bundle bone PD L Tooth root

19. The supporting bone consists of 2 parts : I) Cortical plates , which are made of compact bone II) The spongy ( cancellous ) bone , which fills the area between these plates and the alveolar bone proper . . 2 - Supporting alveolar bone

20. The cortical plates of the alveolar processes are continuous with the labial & lingual cortical plates of the maxilla and mandible. Generally, they are thinner in the maxilla than in the mandible. a . The cortical plates

21. In the region of the anterior teeth of both jaws the cortical plates are very thin and fused directly with the alveolar bone proper with no spongy bone in between .

22. They are thickest in the premolar and molar regions, where the Ling . plate is thicker than the buccal one. In the region of the mandibular third molar , the Lingual plate is thinner than the buccal one because of the presence of the external oplique ridge.

23. During extraction, the last extraction movement is toward the thinner cortical plate.

24. In the maxilla, the outer cortical plate is perforated by Volkman's Canals and may show defects in the posterior teeth region. Larger defect exposing the root portion is known as fenestration. If the defect includes the coronal alveolar crest it is called dehiscence. Bony defects

25. Defect exposing the root portion defect includes the coronal alveolar crest

26. It is found between the alv. bone proper and the cortical plates and between the alv. bone proper of the adjacent sockets. Its degree of development is related to the forces of mastication. It is absent in the anterior region of both jaws where the outer wall of the tooth sockets is very thin . b. Spongy or cancellous bone

27. Cancellous bone is very sensitive to variation in functional forces . The increase in functional force leads to formation of new dense bone. Decreased function leads to decrease in the volume of bone. This can be observed in the cancellous bone of teeth which have lost their antagonists. Here the cancellous bone around the alveolus is reduced and the trabeculae become less numerous and very thin.

28. Radiographic appearance of alveolar bone A ppears as a radioopaque (white) line adjacent to the root and separated from it by a radiolucent line (dark) representing the space of the periodontal ligament. Lamina dura 1- Alveolar bone proper or lamina dura

29. The alveolar process is classified into 2 main types : Type I: The interdental and interadicular trabeculae are regular and horizontal in a ladder-like arrangement , This type is more seen in the mandible Radiographic appearance of alveolar bone 2- Supportig bone or Bony trabicullae

30. Type II: The interdental and interadicular trabeculae are more numerous, delicate and irregularly arranged. This type is more seen in the maxilla

31. Type I Type II

32. Bone remodeling & Bone modeling Bone formation occurs throughout life by a process called bone remodeling . During remodeling bone formation is usually preceded by bone resorption . Bone formation is due to the tension (pull ) of the periodontal ligament fibers. Bone resorption is due to the pressure of the P.D.L fibers. While the process by which the overall size and shape of bone is established is referred to as bone modeling .

33. Physiologic movement Mesial drift Occlusal movemen ( Poste eruptive movement ) Orthodontic movement During the orth. movement, the alv . bone is under the remodeling process . After orth. movement, the alv . bone undergo modeling process . Tooth movement

34. Mesial Drift It is physiologic tendency of all teeth to move towards the midline During mesial drift bone is apposed on the distal alveolar wall bone is resorbed on the mesial alveolar wall.

35. Occlussal Movement It is physiologic tendency of all teeth to move towards the occlussal plane During occlussal drift, there is periapical bone appossition causing tooth elongation

36. Self-Evaluation Review Define alveolar Discuss alveolar bone structure True or False Alv . Bone is called cribriform plate because bundles of Sharpey’s fibers are inserted in it ( ) It is called lamina dura because it appears radiolucent in x-ray ( ) Bundles bone is more found in the distal wall of the alveolar process ( ) Cancellous bone of the supporting bone is very sensitive to variation in functional forces ( ) Discuss the radiographic appearance of the alveolar bone Discuss bone remodeling & modeling with its applications In mesial drift bone…………….is found mesial alveolar bone & ……….. is found distal alveolar bone

37. Antonio Nanci : Ten cat`s Oral Histology: Development, Structure, and Function , 8 th ed. Elsevier Health Sciences, Mosby, 20`3 Bhasker , S.N.: Orban’s Oral Histology and Embryology, Edition By G.S. Kumar, Mosby 13 th ed. 2011 Avery, J.K. : Oral development and Histology , 3 rd ed New York Thieme 2002 Avery, J.K., Daniel, J & Chiego , Jr: Essential of Oral Histology and Embryology. A clinical Approach 4 th ed 2013 Berkovitz , B.K.B., Holland, G.R. & Moxham , B.J.: Oral Anatomy, histology and Embryology, 4 th ed Mosby 2009