Biochemistry - Unit III - Caries

  1. Pellicle
    • Salivary globular proteins (w/ negative charges) attach to the positively-charged tooth surface (Ca++, HA) and form a continuous film, which is the pellicle
    • stabilize the tooth surface, preventing dissolving or getting more mineral deposit
    • lubricate the occlusal surface
    • site for baterial attachment
    • generating staining
  2. Early plague
    • non-pathogenic organisms
    • within 24hr
  3. Extrinsic dental stains
    • Adhesion of chromogenic compounds to the tooth surface.
    • Chemical reactions resulting in the formation of colored compounds (browning reaction between sugars and amines).
    • Reactions of iron, tin and other metals with sulfur resulting in dark compounds
  4. Interaction of tea-tannins with pellicle-proteins
    Following exposure to tea the pellicle proteins can get cross linked to form rubbery tenacious nodules that are stained.
  5. Remineralization of teeth by pellicle - Statherin
    • prevent precipitation or crystallization of supersaturated calcium phosphate in ductal saliva and oral fluid thus helps to maintain the integrity of enamel
    • Produced by acinar cells in salivary glands
    • an effective lubricant preventing tooth wear
  6. Plaques - biofilm
    • Cocci mostly nonpathogenic, early colonizers, binds to pellicle within 24hrs, thin
    • Mixed population including pathogens anaerobes, thick plaque, mature pellicle, diverse species
    • When the pathogenic species overgrows and take over the population, the diversity may go down again
    • Maintains the plaque at the nonpathogenic cocci level will prevent caries
  7. Sucrose is a particular bad sugar in terms of caries - more cariogenic than other sugar
    • sucrose->glucose->glycolysis->acid->caries
    • S. mutans use Glucosyl transferase (GTF) to break down sucrose and re-assembles individual monomeric forms into extracell homopolymers (glucans or fructans) which tightly binds to tooth surface and the bacteria
    • fructose -> glycolysis -> energy + acid
    • glucose -> glucan (amylose like polymer)
  8. GTF
    • highly specific to sucrose
    • Broad pH range 5-7
    • Enzyme is constitutetively expressed
  9. Glucan
    • acts as a “glue” and glues bacteria to teeth.
    • Two forms of glucans; soluble form (dextran) and insoluble form (mutan)
    • Insoluble form causes an increase in number of S. mutans that can attach to teeth
  10. Acid production of S. mutan
    • glycolysis-> lactic acid
    • can tolerate low pH environment
  11. Veillonella
    • breaks down lactic acid (low pKa) and produces acetic acid or Propionic acid, weaker acids.
    • Veillonella colonization inhibits caries formation.
  12. Xylitol anti-cariogenic sugar
    • uptaken by the pathogenic bacteria
    • can be transformed to xylitol phosphate, which can not be utilized -> starved to death
  13. Probiotic approach
    the bacteria take over the niche and produce alcohol instead of acid
  14. Oral malodor
    Protein breakdown -> sulfur containing amino acids
  15. amino acid break down to produce basic compounds by bacteria
    • NH3, urea
    • increase pH
    • helps prevent caries
    • Arginine containing dental
    • products
  16. dentin vs enamel
    • enamel mostly mineral 97%
    • dentin large amount of protein, collagen meshwork, more like bone
  17. Collagen break down enzyme
    • matrix metaloproteiase (MMP)
    • derived from bacteria as well as host (saliva and dentin matrix).
    • activated by exposure to low pH followed by neutralization
  18. Collagen
    • triple helical
    • the gap between individual fibers are susceptible to caries
  19. Phosphoproteins in Dentin Mineralization
    • Collagen network forms first
    • odontoblasts secrete proteins into the matrix to trigger the mineralization of the matrix
    • • Dentin specific phosphoprotein:
    • • identified at the mineralization front; very acidic protein.
    • • Interacts with Ca to form mineral in-vitro.
    • • This reaction is hindered by dephosphorylation
  20. Role of phosphoproteins in dentin formation and repair
    • polyserine or other structure bound by phosphate
    • possibly the most acidic protein
    • gets into the gaps between collagen and attract Ca++ and eventually mineralize
  21. development of Caries of dentin involve two steps
    • dissolution of the mineral HA
    • dissolution of the collagen matrix
  22. MMP may be activated in the acid erosion of dentin
    • non-caries erosion
    • cause sensitivity at the root area
Card Set
Biochemistry - Unit III - Caries
Biochemistry - Unit III - Caries