Bone Structure and Types of Spongy Bone

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Questions and Answers

What type of bone fills the space between the outer and inner plates and the alveolar bone proper?

Cancellous bone

Spongy bone (correct)

Cortical bone

Compact bone

What is the characteristic of Type 1 trabeculae in spongy bone?

Thin and fragile

Regular and horizontal in a ladder-like arrangement (correct)

Irregularly arranged and delicate

Thick and compact

What is the approximate percentage of inorganic component in bone composition?

50%

25%

67% (correct)

33%

What is the primary function of bone marrow in the alveolar bone?

Production of blood cells Signup and view all the answers

What is the composition of bone marrow in young bone?

Red only Signup and view all the answers

What is the term for isolated areas where the root is denuded of bone and covered only by periosteum and overlying gingiva?

Fenestration Signup and view all the answers

Which of the following is NOT a predisposing factor for fenestrations and dehiscences?

Posterior location Signup and view all the answers

What is the interdental septum composed of?

Cancellous bone bordered by the socket walls of approximating teeth and the facial and lingual cortical plates Signup and view all the answers

During which type of ossification is alveolar bone formed?

Intramembranous ossification Signup and view all the answers

What is the process of replacing old bone with new bone?

Bone remodelling Signup and view all the answers

What is the type of collagen found in bone?

Type I Signup and view all the answers

What is the function of canaliculi in alveolar bone?

To bring oxygen and nutrients to osteocytes Signup and view all the answers

What is the component of bone that provides structure and strength?

Hydroxyapatite crystals Signup and view all the answers

At what stage of fetal development do mandible and maxilla form a groove that is opened toward the surface of the oral cavity?

End of the 2nd month Signup and view all the answers

What consists of compact bone and forms the outer and inner plates of the alveolar process?

Cortical plates Signup and view all the answers

What is the characteristic of the outer cortical plate in the maxilla?

It is perforated by many small openings Signup and view all the answers

What type of bone is found in the spongy bone structure?

Cancellous bone Signup and view all the answers

What is the function of the bundle bone?

To line the socket and provide attachment to Sharpey's fibers Signup and view all the answers

What is the characteristic of the lamina dura?

It is radiopaque and contains more calcium salts per unit area than other bones Signup and view all the answers

What is the region where the cortical plate is fused with the alveolar bone proper?

Anterior region of both jaws Signup and view all the answers

What is the difference between the cortical plates in the maxilla and mandible?

The mandible has thicker cortical plates than the maxilla Signup and view all the answers

What is the characteristic of the buccal plates?

They are thin Signup and view all the answers

Study Notes

Alveolar Bone

Covered by periosteum
Filled with spongy bone, which consists of heavy trabeculae with bone marrow spaces
Trabeculae are of two main types:
- Type 1: regular and horizontal in a ladder-like arrangement, commonly seen in the mandible
- Type 2: irregularly arranged, numerous, and delicate, more common in the maxilla

Bone Marrow

Red in young bone and yellow in old bone
Consists of:
- Blood-forming elements
- Osteogenic cells
- Adipose tissue

Interdental Septum

Consists of cancellous bone bordered by the socket walls of approximating teeth and facial and lingual cortical plates
Can have irregular windows appear in the bone adjacent to roots if they are too close together

Embryology of Alveolar Bone

Forms near the end of the 2nd month of fetal life
Mandible and maxilla form a groove that opens towards the surface of the oral cavity
Bony septa form gradually as tooth germs develop

Osteogenesis

Process of bone formation
Alveolar bone is formed during fetal growth by intramembranous ossification
Consists of a calcified matrix with osteocytes enclosed within spaces called lacunae
Osteocytes extend processes into canaliculi that radiate from the lacunae

Bone Composition

67% inorganic (hydroxyapatite crystals, calcium, phosphates, hydroxyl, carbonate, sodium, magnesium, and fluorine)
33% organic (non-collagenous proteins, collagen type I, osteocalcin, osteonectin, phosphoproteins, and bone morphogenic protein)

Fenestrations and Dehiscences

Isolated areas where the root is denuded of bone and covered only by periosteum and overlying gingiva are termed fenestrations
When the denuded area extends through the marginal bone, it is called a dehiscence
Predisposing factors:
- Prominent root contour
- Malposition
- Labial portion of the root combined with a thin bony plate
- More common on facial bone than on lingual bone
- More common anteriorly than posteriorly
- Often occurs bilaterally

Bone Turnover (Remodeling)

Replacement of old bone by new bone
Occurs in physiologic growth movements

Alveolar Process

Defined as the parts of the maxilla and mandible that form and support the sockets of the teeth
Forms when the tooth erupts to provide osseous attachment to the forming periodontal ligament
Disappears gradually after the tooth is lost

Alveolar Bone Proper

Surrounds the roots of the tooth and gives attachment to the principal fibers of the periodontal ligament
Histologically, it is bundle bone and lamellared bone

Bundle Bone

The bone that lines the socket in which Sharpey's fibers are embedded
Perforated with many small foramina for blood vessels and nerves
Contains more calcium salts per unit area than other bone
Also known as lamina dura due to its radiopacity

Supporting Alveolar Bone

The bone that surrounds the alveolar bone proper and gives support to the socket
Consists of cortical plates and spongy bone (cancellous bone)

Cortical Plates

Consists of compact bone and forms the outer and inner plates of the alveolar process
Thinner in maxilla than in mandible
Thickest in the premolar and molar region of the mandible
Buccal plates are thin, but lingual plates are heavy

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Description

This quiz covers the structure and types of spongy bone, including the arrangement of trabeculae and their characteristics. It's an important concept in anatomy and bone biology.