Calculus Flashcards
what is the composition of calculus?
70-80% inorganic salts - mainly calcium and phosphate
organic - mainly proteins and carbohydrates
lipids make up a very small portion
what is the inorganic portion of calculus?
2/3 in crystalline form
randomly placed crystals
sub and supra = similar
what are the principal crystalline forms of calculus?
hydroxyapatite 58%
magnesium whitlocke 21%
octacalcium phosphate 21%
brushite 9%
where is brushite most commonly found?
supra and new calculus
where is hydroxyapatite commonly seen?
in older calculus
where is magnesium whitelocke commonly seen?
sub calculus
what is the structure of calculus?
layered varying degrees of calcification needle shaped/platelet or rod calcified micro organisms layer of plaque on top
how is calculus formed?
plaque deposition mineralisaiton crystals in matrix gradual mineralization usually 2-14 days rapid or slow calculus formers also forms on fixed and removable prosthetic devices
how does calculus attach?
pellicle also becomes calcified
penetrates surface irregularities
subgingival is more difficult to remove
what is the carbon dioxide theory?
freshly secreted saliva - higher conc of CO2 than the oral cavity
result = CO2 escapes from the saliva and gives a rise in pH
high pH = calcium and phosphate are released and can crystallise
D - doesn’t explain subgingival calculus
what is the formation of ammonia theory?
rapid calculus formers have increased urea conc in the saliva
ammonia - breakdown product of urea
ammonia = pH rise
doesn’t explain sub calculus
what is the nucleation theory?
seeding agent - crystallisation
what are anti calculus agents?
pyrophosphates, diphosphate reduced formation of new supra only no effect on calculus already present no effect on subgingival calculus good for rapid calculus formers - patients using chx
