Anatomy and Structure of the Mandible and Maxilla

Overview

• Both mandible and maxilla are bones that form the jaws.
• Mandible: Divided into a horseshoe-shaped body and quadrilateral-shaped ramus.
  • Ramus: Superior surface with chondroid process (anterior) and condylar process (posterior).
  • Mandibular Notch: Separates the chondroid and condylar processes.
• Maxilla: Pyramid-shaped with palatine, zygomatic, frontal, and alveolar processes.

Alveolar Process/Bone

• Part of mandible and maxilla supporting the teeth sockets.
• Dependent on tooth presence for development and maintenance.

Composition

• Cancellous (Spongy) Bone: Central part.
• Compact Bone: Dense outer sheet.
• Tooth Sockets: Formed of compact bone, providing anchorage for teeth roots.

Septums

• Inter-dental Septum: Between two teeth.
• Inter-radicular Septum: Between roots of multi-rooted teeth.
• Contains nutrient canals for blood vessels and nerves.

Alveolar Bone Structure

• Categorized into:
  • Alveolar Bone Proper
  • Supporting Alveolar Bone

Alveolar Bone Proper

• Forms the tooth socket, about 0.1 to 0.4 mm thick.
• Composed of dense compact bone, also known as the cribriform plate.
  • Perforations allow blood vessels and nerves to enter/exit periodontal space.
  • Appears more opaque in radiographs (lamina dura).
• Histological Components:
  • Bundle Bone: Contains embedded principal fibers of periodontal ligament (Sharpey's fibers).
  • Lamellated Bone: Compact bone without principal fibers.

Supporting Alveolar Bone

• Surrounds the tooth socket.
• Composed of:
  • Cortical Plates: Inner and outer plates of compact bone.
    • Thicker in mandible, especially in buccal side of premolar and molar region.
  • Spongy Bone: Between cortical plates and alveolar bone proper.
    • Formed of lamellar bone trabeculae, classified into type 1 (regular, ladder-like) and type 2 (irregular).
    • Type 1 more common in mandible; type 2 in maxilla.
    • May be absent in anterior maxilla and mandible, fusing alveolar bone proper with cortical plates.