Periodontium: Alveolar bone and the alveolar process

• What is the alveolar bone?

  Alveolar bone ("socket bone") is the bone that forms and defines the alveolus (the tooth socket).

  
• where is the alveolar bone found in healthy teeth?

  all around the toot, extending between tooth roots and neighbouring teeth, but also up to the cervical margins of the teeth
• what is the alveolar bone like in radiographs?

  the alveolar bone is usually more radiopaque than dentine and enamel.
• what is the difference between the alveolar bone and alveolar process?

  alveolar bone= the bone formed by each tooth during development

  
  

  alveolar process= the bone found around teeth (it is made of alveolar bone proper, and other bone types)

  
  

  ***These are often synonyms in textbooks and are used interchangeably

  
• what are the layers of the Alveolar process that are visible in a radiograph?

  • A radiopaque socket-lining layer known as the lamina dura.

  • A spongy trabecular region or spongiosa.

  • A radiopaque outer cortical region.
• show the lamina dura of the alveolar process

  
• show the trabecular region or spongiosa of the alveolar process

  
• show the cortical region of the alveolar process

  
• Alveolar bone is produced by each tooth, NOT by the bone of the jaw!

  
  

  TRUE/FALSE

  TRUE

  
  

  -> This helps explain why patients experience bone loss (alveolar process) after the extraction or loss of teeth
• what is the composition of alveolar bone?

  Alveolar bone has a similar composition to bone from other regions of the body:

  
  

  • Matrix: collagen-rich (mostly type I collagen, but contains some noncollagenous proteins [bone salioprotein, osteocalcin, osteopontin, proteoglycans])

  
  

  • Mineral phase: hydroxyapatite (67%)
• what cells produce the organic matrix (osteoid) of alveolar bone?

  osteoblasts

  
  

  -> Osteoblasts deposit bone matrix towards the tooth root
• what happens if osteoblasts become entombed in the matrix?

  they differentiate into osteocytes
• what cell maintains the mature bone tissue?

  Osteocytes
• what nourishes the alveolar bone- osteocytes and mature bone tissue?

  alveolar bone has vascular spaces that have blood vessels
• what is the region where the ligament fiber bundles of the PDL are attached to the alveolar bone called?

  the socket-lining layer of alveolar bone

  -> These leave Sharpey's fibers entombed within this layer

  (For this reason, it is called the bundle bone layer= LAMINA DURA)

  
• the bundle bone layer is rapidly changing

  TRUE/FALSE

  TRUE

  - hence the rapid, disorganized nature of the bundle bone matrix
• The bundle bone layer is less vascularized than the surrounding bone.

  TRUE/FALSE

  TRUE
• how are Sharpeys fibers visualised?

  - Often need to use crosspolarized light to visualize Sharpey's fibers in alveolar bone

  - Cross-polarized light lets you see the texture of a tissue that is otherwise invisible under white light
• what is the bundle bone layer made of?

  a rapidly-deposited, poorly organized collagen matrix.

  
  

  - The mature bone that forms from this matrix is called woven bone.
• how is the bundle bone layer visualised?

  Cross-polarized light often reveals a clear difference between bundle bone and the more external layers of the alveolar process
• other than the bundle bone layer of the alveolar bone, why does the rest of the bone have a different texture?

  due to bone remodeling.

  (natural turnover process)
• explain bone remodeling

  • Primary bone matrix is first removed through resorption by osteoclasts, which carve out space for new blood vessels.

  • New bone is laid down around these blood vessels in concentric rings (lamellae).

  • This produces secondary osteons (blood vessel space surrounded by circumferential lamellae)
• what does bone remodeling in the alveolar process turn woven bone into?

  Bone remodeling in the alveolar process turns woven bone (primary texture) into Haversian bone (secondary, or remodeled texture).
• why can the types of bone lining the tooth socket change?

  because teeth are constantly moving and shifting positions within the jaws through minor adjustments and bone remodeling
• what type of bone is the spongiosa of the alveolar process made of?

  trabecular bone:

  • Strut-like arrangement of bone tissue.

  • Not compact (hence the "spongy" texture).

  • Bone marrow fills the rest of the space.

  
• what are the compact bone/compacta, or cortical plates?

  • These are the outer walls of bone surrounding our teeth.

  • These are made of compact (or cortical) bone- the bone tissue that forms the outer walls of most of our bones.