Growth and development [autosaved]
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Bone formation begins with mesenchymal cells differentiating into fibrous membrane or cartilage, leading to two types of bone development: intramembranous and endochondral ossification. Intramembranous ossification forms the maxilla and mandible from connective tissue membranes, while endochondral ossification replaces cartilage models with bone to form long bones and some cranial bones. Bone and cartilage have similarities as specialized connective tissues made of cells, fibers, and matrices, but bone is calcified while cartilage is not, and bone grows by apposition while cartilage expands interstitially. The major sites of growth in the mandible and maxilla are the condyle, ramus, and tuberosity,
Growth and development [autosaved]
- 1. GROWTH AND DEVELOPMENT GLO ARBY ARGUELLES, DMD
- 2. BONE FORMATION Begins in the embryo where mesenchymal cells differentiate into either fibrous membrane or cartilage leading to two paths of bone development Intramembranous ossification: Takes place in membranes of connective tissue. Osteoprogenitor cells in the membrane differentiate into osteoblasts. This collagen matrix formed undergoes ossification. Formation of maxilla and mandible. Endochondral ossification: Takes place within a hyaline cartilage model. Cartilage cells (chondrocytes) are replaced by bone cells (osteocytes) where calcium and phosphate are deposited into the organic matrix that has been laid down. Formation of short and long bones, and ethmoid, sphenoid, and temporal bones
- 3. DYNAMICS OF BONE GROWTH BONE • Made up of mucopolysaccharide and apatite crystals. • Vascular system that penetrates haversian canal for NUTRITION. • Growth is through apposition. CARTILAGE • Made up of chondroitin sulfate and non-collagenous fibers. • Hydrophilic/non-vascular • Growth is by expansion of the cells rather than apposition. • PRESSURE RESISTANT
- 4. SIMILARITIES BETWEEN BONE AND CARTILAGE SPECIALIZED CONNECTIVE TISSUE MADE UP OF CELLS, FIBERS AND INTERCELLULAR SUBSTANCE MATRICES WHICH COULD CALCIFY LATER FUNCTION TO SUPPORT THE BODY
- 5. BONE CARTILAGE CALCIFIED / VASCULAR NON-CALCIFIED/NON VASCULAR GROWS BY APPOSITION GROWS BY APPOSITION AND INTERSTITIALLY (Chondrocytes) / ADDITION TO ITS INTERCELLULAR MATRIX BECOMES HOLLOW INTERIORLY NOT HOLLOW RESORPTION IS A NORMAL FEATURE RESORPTION IS NOT A NORMAL FEATURE DIFFERENCES BETWEEN BONE AND CARTILAGE
- 6. MECHANISM OF BONE GROWTH 1. DRIFT • Growth produced by deposition of new bone of one side of cortical plate and resorption on the other side.
- 7. MECHANISM OF BONE GROWTH 2. DISPLACEMENT • Movement of whole bone away from each other by some physical force that carries it from other bones which are also growing: *PRIMARY DISPLACEMENT - Bones own enlargement (TRANSLATORY) *SECONDARY DISPLACEMENT - Enlargement of adjacent bones (RELOCATION) - Nasal area of the adult occupies an area where the bony maxillary arch used to be located during childhood. *POSTERIOR GOWTH - Anterior Displacement
- 8. PRINCIPLES OF BONE GROWTH I. GROWTH OF THE FACIAL BONE - does not occur by uniform all-over apposition of bone. • APPOSITION always towards the direction of growth • RESORPTION Always away from the direction of growth • REMODELLING Process of maintaining the shape and thickness of bone which also results in movement.
- 9. PRINCIPLES OF BONE GROWTH II. GROWTH SITES - lie between two bones. • SUTURES Connective tissue • TMJ Between cartilage and condyle • SYNCHONDROSIS
- 10. Growth of the Mandible MAJOR SITE OF GROWTH MANDIBULAR CONDYLE Occurs by: Proliferation of cartilage at the condyles. Selective apposition and resorption of bone at the membrane surfaces of the mandible itself (remodeling). Resorption occurs along the anterior surface of the ramus. Apposition of bone occurs along the posterior surface of the ramus.
- 11. Growth of the Mandible MAJOR SITE OF GROWTH Major site of vertical growth in the mandible. Provide space between the jaws into which the teeth erupt (especially molars). Main growth thrust: Upward and backward process to fill in the resultant space to maintain contact with the base of the skull. Meanwhile soft tissue carries the mandible forward and downward. Mandible can and does undergo more growth in the late teens than the maxilla
- 12. Timeline of growth: In infancy: • Ramus is located at the approximately where the primary first molar will erupt. • Progressive posterior remodeling creates space for the second primary molar and then for the sequential eruption of the permanent molar teeth. • If this process ceases before enough space is created for eruption of the third permanent molars, they will become impacted. • At age 6, the greatest increase in size of the mandible occurs distal to the first molar . Growth of the Mandible
- 13. • MAJOR SITE OF GROWTH MAXILLARY TUBEROSITY • Deposition of bone in the tuberosity region → the increase in height and elongation of maxillary arch in the posterior direction. Growth of the Maxilla
- 14. Growth of Alveolar Process • Grows in height and length to accommodate the developing dentition. • Exists only to support teeth: If tooth fails to erupt → alveolar process will never form. If tooth is extracted → alveolar ridge completely atrophies over time
Editor's Notes
- #4: Expansion = there is a new cell synthesis. material and controlled loosening of the wall to allow it to stretch and increase in area