Alveolar bone Flashcards
What bones form the upper and lower jaw
- 2 maxillary bones form the upper jaw
- Mandible forms the lower jaw
What is the part of the maxillary/mandibular that supports + protects the teeth
Alveolar bone
What bones are on either side of the sockets of individual teeth
- Cortical bone
- Buccal and palatal alveolar plates
What lies between each socket
Interdental septa
What are the roots of multirooted teeth separated by
Interradicular septa
Where is the external (buccal/labial) alveolar plate thicker
On the buccal side of posterior teeth
Where is the internal (lingual) alveolar plate thicker?
Thicker on the palatal side of upper teeth
How does the lamina dura appear on clinical radiographs
As a thin, continuous opaque line outlining the socket wall
How may bones be classified?
Explain further
- Compact bone
- Forms a dense solid mass - Cancellous bone
- Lattice arrangement of the individual bony trabeculae that surround marrow
What does the combination of compact and cancellous bone give
Maximum strength at minimum skeletal weight
Describe the composition of the alveolar bone
- Mineralised connective tissue, supporting and protecting the teeth
- Mineral component provides rigidity and resistance to compression - mostly Collagen Type I
What are the main functions of the alveolar bone
- Provide support and protection for teeth
- Can adapt based on psychological needs
Describe the organic matrix of the alveolar bone
- Mostly collagen (mostly intrinsic collagen secreted by osteoblasts)
- Collagen inserted as Sharpey’s fibres = extrinsic collagen
- Major Collagen is Type I
Describe osteoids
- Newly deposited, unmineralised bone matrix found at bone formation sites
In cancellous bone, what do bone layers or lamellae form
Trabeculae
Describe the bone marrow in young bone
Red and hematopoietic
Describe bone marrow in older bone
- Yellow
- Loss of hematopoietic potential
- Increased accumulation of fat cells
What bone patterns are lamellae arranged into
- Circumferential lamellae:
- At external and internal surfaces
- Arranged into parallel layers - Small concentric layers around a central neurovascular canal
What is a haversian system
The central canal with 20 concentric lamellae
Describe osteoblasts:
What are they
Where are they prominent
What are they in contact with
What do they secrete
- Bone forming cells
- Specialised connective tissue cells
- Prominent where there’s active bone formation
- In contact with underlying osteocytes
- Secrete molecules controlling their own activity
Describe osteocytes:
What are they
What do they represent
- Cells lying within the bone
- Represent osteoblasts trapped in the bone matrix
- Induction of osteoclast induction
- Primary mechano-sensors in the bone
Describe osteoclasts
What are they
What happens once activated
What do they secrete
What do they express
- Bone resorbing cells
- Once activated, bone resorption occurs in 2 stages: Mineral phase and remaining organic matrix is removed
- Secrete protons
- Express receptors for hormones
Describe osteoblasts in terms of:
Mesenchymal or hematopoietic
Where do they lie
What do they secrete
How are they incorporated into the bone matrix
- Mesenchymal
- Lie on surface of forming bone
- Secrete and mineralise organic matrix
- Incorporated into the bone matrix as osteocytes
Describe osteocytes in terms of:
Mesenchymal or hematopoietic
Where do they lie
How do they communicate
Whats their role
- Mesenchymal
- Lie within bone and surrounded by bone matrix
- Communicate with each other and w/ osteoblasts
- Detect strain in bone
Describe osteoclasts in terms of:
Mesenchymal or hematopoietic
What are they rich in
Why is the border ruffled
- Hematopoietic
- Rich in acid phosphate
- Border pumps acid to dissolve bone mineral and enzymes, to degrade collagenous matrix
Describe Sharpey’s fibres
- Extrinsic collagen fibres from the PDL
- Enter bone perpendicular to the surface
- Less numerous but thicker
- Degree of mineralisation in fibres varies
- Embedded fibres may remain unmineralised at their centres or be fully mineralised
Describe incremental lines in the alveolar bone
- 1 line is a smooth regular line with several running in parallel
- Reversal line - irregular, scalloped appearance
- Reversal line marks bone surface at some point when resorption ‘reversed’ to formation
- When resorption is no longer required, osteoclasts migrate away from the area + a layer of osteoblasts form a new bone
