ALVEOLAR PROCESS

• Alveolar process


  Part of maxilla and mandible that forms and supports the sockets of the teeth
• Bones of the skull develop by

  1. Endochondral ossification

  2. Intramembranous ossification
• Endochondral ossification


  Cartilage is replaced by bone, bones of the base of the skull
• Intramembranous ossification


  Develop directly from the membranous capsule (desmocranium) or in proximity to cartilaginous portion of skull, all bones of upper face including maxilla, mandible
• Premaxilla


  Median nasal process
• Maxilla proper


  Palatine process of maxillary bone
• Intermaxillary suture


  Median palatine suture
• Mandible


  Develops lateral to meckel's cartilage, mandibular symphysis
• Composition of alveolar bone

  • Inorganic = 65% (hydroxyapatite)
  • Organic = 35%
  • Collagen = 88% - 89%
  • Noncollagen = 11% - 12%
  • Glycoproteins = 6.5% - 10%
  • Proteoglycans = 0.8%
  • Sialoproteins = 0.35%
  • Lipids = 0.4%
• Development of alveolar process

  2nd month of fetal life, a groove that is open towards the surface of the oral cavity develops, within the groove are the tooth germs – dental sac
• Alveolar process


  Only develop upon eruption of teeth and it diminishes in height after loss of teeth
• Alveolar bone proper


  Thin lamellae of bone that surrounds the root of tooth and gives attachment to the principal fibers of periodontal ligament, Cribriform plate – perforated with many openings (Volkmann's canal) that carry nerves and blood vessels to the periodontal ligament
• Bundle bone


  Part in which the bundles of principal fibers of periodontal ligaments are anchored to (sharpey's fibers), contain more calcium salts than other portion (lamina dura)
• Lamellated bone


  Surrounds bundle bone and are arranged in parallel manner to marrow spaces, form haversian systems
• Supporting alveolar bone


  Surrounds the alveolar bone process, cortical plates, spongy bone
• Cortical plates


  Thin in labial surface of anterior teeth (thinnest in mandibular anterior teeth), thicker in mandible than in maxillary bone (thickest in mandibular PM and Molar areas)
• Spongy bone


  Fills the area between the outer and inner alveolar plates, contains marrow spaces
• Type I spongiosa


  Regular and horizontal ladderlike arrangement, mandible
• Type II spongiosa


  Irregularly arranged and numerous trabeculae, maxilla
• Physiologic changes in the bone

  • Osteoblast
  • Osteocyte
  • Osteoclast
• Internal reconstruction of bone

  Bone deposition, Bone resorption
• Bone deposition


  At outer surfaces of the cortical plates, thickening of lamellae from inside by haversian bone
• Bone resorption


  Outer surfaces
• Process in bone resorption

  1. Decalcification

  2. Degradation of matrix

  3. Transport of degraded matrix to extracellular fluid or blood vascular system
• Cutting cone / resorption tunnel


  Area of resorption
• Reversal line


  Scalloped outline of howships's lacuna that turn their convexity towards the old bone, between old bone and area of new bone deposition/apposition
• Resting lines


  Cementing lines that correspond to a rest period in an otherwise continuous process of bone apposition
• The biologic plasticity of the bone enables the orthodontist to move the teeth without disrupting their relations to the alveolar bone
• Increase in functional forces

  Formation of new bone
• Decreased function


  Decrease in bone volume
• Immature or coarse fibrillar bone is formed in areas of fracture or extraction wounds, increase number of cells and decreased volume of calcified intercellular substance, 2-3 weeks before the bone is visible in xray
• The progressive loss of alveolar bone in periodontal disease is difficult to control. Once lost, this bone is even more difficult to repair of regenerate.
• Synthetic materials may replace bone tissue – ridge augmentation and filling of bony defect, nonresorbable hydroxyapatite, resorbable tricalcium phosphate