W5: Bichemistry Of Bone And Teeth 2 Flashcards
What are osteoblasts?
Bone forming cells derived from mesenchymal progenitor stem cells
What are osteoclasts?
Multinucleated bone resorbing cells derived from haematopoietic stem cells
What are odontoblasts?
Dentine producing cells derived from neural crest cells/ecto-mesenchymal progenitor cells. Maintains dentine viability and has regenerative capacity.
What are cementoblasts?
Cementum producing cells derived from ecto-mesenchymal cells. Have a regenerative capacity.
What are ameloblasts?
Enamel producing cells. One prism derived from one cell (ectodermal - epithelial origin; cytokeratin expression). Disappears at time of eruption - non-vital enamel tissue.
Complex and dynamic regulation of hard tissues
Regulatory factors like hormones regulate the cells (osteoblasts, odontoblasts and cementoblasts)
Cells are converted into and from calcified extracellular matrix (ECM)
Calcified ECM can be converted into degradation products (calcium bioactive molecules) by bacteria causing acid dissolution or cells causing resorption and enzymatic degradation
Important feature of hydroxyapatite crystals
Chemical exchange: ion substitutions can occur if the substituent ion is the same size
What are the main substituents of human apatite?
- HPO4 and CO3 for PO4
- Sr, Ba, Pb, Na, K, and Mg for Ca
- F, Cl, Br and I for OH
How might the ions present in enamel influence dental caries?
The ions present in enamel may influence dental caries by affecting the dissolution of the apatite crystals and/or affecting remineralisation.
How does fluoride affect caries?
Fluoride incorporation in enamel crystal inhibits caries
How does carbonate affect caries?
Carbonate incorporation in the crystal may promote caries
Organic composition/ECM of the bone, dentine and cementum
Collagen (mainly type I)
Noncollageneous proteins: glycoproteins, proteoglycans, enzymes, growth factors:
- soluble serum proteins and tissue specific an ionic
- non-soluble (bound to collagen)
What collagens are fibrillar collagens?
Type I, II, III and V
Structure of fibrillar collagen
The fibrils consist of tropocollagen molecules aligned with each other in a quarter stagger arrangement.
Cross-linking occurs at lysine and hydroxylysine residues and increases throughout life. This confers strength on the molecule, but with age, the tissue becomes stiffer and loses elasticity.
In soft tissues labile cross-links (soluble collagen), in hard tissues there is stable cross-linking (insoluble)
Where is type I collagen found?
In fibrous supporting tissues, the dermis of the skin, tendon, ligaments, and calcified tissues (bone and teeth). Can be loose or dense depending on mechanical properties needed.
