structure of periodontium - alveolar bone semester 1

Question 1

Discuss general characteristics of alveolar bone.

Answer 1

• Formed during fetal growth, consisting of calcified matrix with osteocytes
  (bone cells) which originate from osteoblasts
• Continual changes; however, retains same approximate form throughout life
• Balance between deposition by osteoblasts and resorption by osteoclasts
  (renewal and remodelling)

Question 2

Define the alveolar process and describe the layers that compose it

Answer 2

Function: forms the bony sockets
that provide support and protection
for the roots of the teeth.
* Composed of:
* Alveolar bone proper (cribriform
plate)- inner socket wall of thin,
compact bone
* Supporting alveolar bone-
consists of cancellous bone,
facial (outer cortical) and lingual
(inner cortical) plates of compact
bone

Question 3

Describe the characteristics of cortical versus cancellous (spongy)
bone

Answer 3

Cancellous bone (aka as trabecular bone) can be visible on a radiograph.
Increased forces = increased trabeculae
cortical - consist of plates of compact bone found on the facial and lingual surfaces of the alveolar bone.

Question 3

Define alveolar crest and explain its appearance on radiographs

Answer 3

Alveolar Crest:
* Most coronal part of the
alveolar process
* In health: crest is located 1 to
2 mm apical to CEJ of teeth
* From facial or lingual aspect, it
meets teeth in scalloped
(wavy) line following the CEJ
of the teeth

Question 4

List factors that can affect the alveolar bone

Answer 4

The alignment of the teeth, the angulation of the roots in the bone, and occlusal forces affect the height and thickness of the bony plates (facial and lingual)
Also affected by: * Function * Age * Disease related change * Hormones * Host factors * Systemic disease

Question 5

Describe the periosteum and its function

Answer 5

• Covered by periosteum- a dense layer of tissue that lines the outside of the
  bone and plays an active role in bone formation
• Fibrous outer layer is responsible for attachment of tissue to bone
• Cambium layer contains progenitor cells that develop into osteoblasts
• Becomes unstable if periodontal disease is present

Question 6

Define alveolus

Answer 6

are sockets in the jaws in which the roots of teeth are held in the alveolar process with the periodontal ligament.

Question 7

alveolar bone proper

Answer 7

Also known as cribriform plate or
lamina dura is part of the alveolus
directly facing the roots of a tooth
(lines the socket)
* Perforated by tiny channels
containing blood, lymph vessels and
nerves, linking PDL with cancellous
portion of bone
* Vascular supply from branches of
the superior and inferior alveolar
arteries

Question 8

alveolar bone and occlusion

Answer 8

• Normal Occlusal Forces
• Force applied to tooth from chewing etc., tooth is displaced against PDL, which is
  resilient
• Inner and outer cortical plates stretch in direction of the force
• When force is released, the tooth, PDL and bone return to original positions
• Increased Forces
• Number and thickness of trabeculae are increased
• Bone may be added to external surface of inner and outer cortical plates
• Reduced Forces
• Number and thickness of trabeculae are reduced
• Bone resorbs and bone height is reduced
• Termed disuse or afunctional atrophy