OHE

• Bone


  A calcified tissue composed of intercellular substance and specialized cells (osteocytes) contained in lacunae and canaliculi (its process)

  
• Bone


  • Supports the body
  • Protects the vital organs
  • Acts as calcium reservoir
  • For manufacture of R.B.C
  • For attachment of muscles
  • For locomotion

  
• Chemical Composition of Bone

  • Inorganic substance - 70.9%
  • Organic substance - 20.9%
  • Water - 8.2%

  
• Structural Elements of Bone

  • Permanent Elements:
  • Bone Matrix (Intercellular substance)
  • Osteocytes
  • Sharpey's fibers
  • Blood vessels, nerves, lymphatic vessels (Haversian canal)
  • collagenic fibrils
  • calcified cementing substance
  • Transient Elements:
  • Conditions which may lead to Differentiation of Osteoclasts

  
• Osteogenesis (Histogenesis of Bone)

  1. Phase I - Formation of Osteoid Tissue

  2. Phase II - Transformation of Osteoid Tissue into Mature Bone

  
• Endochondral Ossification


  The first sign of development is a condensation of the mesenchyme to precartilage. The cells in this area differentiates into chondrocytes elaborating a hyaline intercellular substance to form cartilage.

  
• Intramembranous Bone Ossification


  Bone is formed directly from fibrous tissue. The primitive mesenchyme in the region of future bone differentiates into osteogenic tissue containing a fibrous connective tissue composed of osteoblasts.

  
• Mandible Development


  The mandible appears as thin bilateral plates of bone at about the sixth week of fetal life. The two halves of bone are joined by fibrocartilage in the midline (mandibular symphysis).

  
• Maxilla Development


  The human maxillary bone is formed from union of the premaxillary bone and maxilla bone. The premaxilla (primary plate) houses the upper incisors and forms the anterior part of the secondary palate (hard palate). The maxillary bone proper came from maxillary process and its extensions known as the palatine process (which develops the hard and soft palates.) Union of the globular process the and maxillary process takes place at about the second month of intra-uterial life.

  
• Alveolar Bone (Alveolar Process) Development


  1. Fibers from outside of the dental sac will form a membrane containing network of fibers which contain cells. This develops into osteogenic tissue where cells differentiate into osteoblasts. The growth of alveolar process is accomplished by:

  2. Direct extension occlusally of the membranous bone on the body of mandible and maxilla.

  3. By deposition of subperiostal bone on the labial and buccal and resorption on the lingual surface which results in lateral and anterior extensions of the cortical plates.

  4. By formation of alveolar bone around the growing roots of the teeth.

  5. Reorganization of Spongiosa.

  
• Structures of Alveolar Process

  • Reconstruction in accordance with functional and nutritional demands of bone
  • Alterations in the structure of alveolar bone in connection with the physiologic movements of the teeth
  • Internal Reconstructions
  • Effect of environmental stimuli

  
• After tooth extraction, alveolar process disappear by resorption on the crest and growth of embryonic bone within the socket.

  
• Lines in Bone


  • Cementing line
  • Reversal line
  • Aplastic line
  • Resting line
• Clinical Considerations


  • During orthodontic treatment, bone may be resorbed on the side where there is pressure and building of bone on the side where there is tension.
  • Trauma or inflammatory process can destroy the condylar growth of mandible on one side or both sides. Hyperfunction of hypophysis may lead to acromegaly or overgrowth of jawbones (especially mandible).
  • In chronic periapical infection, sometimes bone may be affected.
  • In healing of fractures or extraction socket, there is formation of embryonic bone with plenty of cells and less intercellular substance, which is later replaced by mature bone.

  
• Bone


  The rigid organs that makes up the skeletal system of vertebrates

  
• Osteocytes


  The most abundant cells in mature bone and are located in small cavities called lacunae

  
• Osteoblasts


  Specialized cells responsible for bone formation

  
• Osteoclasts


  Specialized cells responsible for the resorption or breaking down of bone tissue

  
• Compact Bone


  Also known as "Cortical Bone"

  
• Spongy Bone


  Also known as "Cancellous Bone"

  
• The two main types of bone ossification

  • Endochondral Ossification
  • Intramembranous Bone Ossification

  
• Meckel's Cartilage


  It is named after Johann Friedrich Meckel, the younger, a German anatomist who first described it in the early 19th century
• Maxilla


  Forms the visceral part of the skull
• Mandible


  Comprises the base of the skull

  
• Temporal Bone


  Forms the lateral walls and roof of the brain case
• Alveolar Process


  Supports and encloses the roots of the teeth

  
• Alveolar Bone


  The position of the tooth determines the location of the alveolar bone

  
• Bundle Bone


  A thin plate of bone next to periodontal ligament and has many holes or openings through which blood vessels, lymphatic vessels, and nerve fiber pass

  
• Mucous membrane


  Lining of body cavities that communicate with the outside
• Oral mucosa


  Lining of the oral cavity
• Subdivisions of the Oral Mucosa

  • Masticatory Mucosa
  • Lining Mucosa
  • Specialized mucosa
• Masticatory Mucosa


  • Gingivae
  • Hard palate
• Lining Mucosa


  • Firmly attached to underlying muscle
  • Loosely attached to underlying bone, fascia or muscle
• Firmly attached Lining Mucosa

  • Covering of the soft palate
  • Covering of the lips
  • Covering of the cheeks
  • Covering of the inferior surface of the tongue
  • Covering of the tonsils
• Loosely attached Lining Mucosa

  • Alveolar mucosa
  • Vestibular mucosa
  • Mucosa of the floor of the mouth (sublingual sulcus)
• Specialized mucosa


  • Dorsum of the tongue
  • Anterior 2/3 - masticatory
  • Posterior 1/3 - lining

  
• Masticatory mucosa


  Generally has keratinized epithelium because these areas are subjected to abrasive forces resulting from biting, grinding and moving the ingested food in the oral cavity
• Lining Mucosa


  Possesses non-keratinized epithelium and serves as a protective lining of the more sheltered areas
• Specialized mucosa


  Are rough and irregular because of the protruding papillae, possess taste buds
• General Histologic Characteristics of Oral Mucosa


  • Surface epithelium
  • Lamina propria (Tunica propria)