Possible regulatory roles of silicic acid, silica and clay minerals in the formation of calcium phosphate precipitates.
The effects of silicic acid, silica and clay minerals on the conversion of amorphous calcium phosphate to hydroxyapatite (HAP) were studied in vitro by a pH drop method. At a concentration range of 0.01-0.1 mM. silicic acid stimulated the rate of HAP transformation by about 30-40%. Silica stimulated the rate of HAP transformation by 33-43% at a concentration range of 0.05-1.5 mg/ml. The clay minerals, i.e. kaolin and talc, also stimulated the rate of HAP transformation by 40-90% at a concentration range of 0.4-10 mg/ml, but mica inhibited the reaction markedly at 10 mg/ml. The distribution of silicon in human supragingival dental calculus was studied by an electron-probe microanalyser. We found localized silicon distribution on the oral surface of the calculus. Such silicon-rich areas always contained silicon either alone or together with magnesium, aluminium, potassium, calcium and iron. This implies that the silicon-rich area may be opal and mica. Because silicic acid, silica, kaolin and talc stimulated and mica inhibited the in vitro calcium phosphate precipitation, it is possible that these silicon-rich areas may regulate the formation of the dental calculus.
Hidaka
S
S
Department of Oral Biochemistry, Fukuoka Dental College, Japan.
Okamoto
Y
Y
Abe
K
K
D000328:Adult; D000368:Aged; D000538:Aluminum Silicates / Q000737:chemistry*; D002118:Calcium / Q000032:analysis / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry; D011232:Chemical Precipitation; D002648:Child; D000077215:Clay; D003728:Dental Calculus / Q000737:chemistry / Q000648:ultrastructure; D017886:Durapatite; D004577:Electron Probe Microanalysis; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006882:Hydroxyapatites / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D008903:Minerals / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis; D012824:Silicic Acid / Q000737:chemistry*; D012825:Silicon / Q000032:analysis; D012822:Silicon Dioxide / Q000737:chemistry*
D000538:Aluminum Silicates; D002130:Calcium Phosphates; D002614:Chelating Agents; D006882:Hydroxyapatites; D008903:Minerals; D010710:Phosphates; C519480:amorphous calcium phosphate; D012824:Silicic Acid; D010758:Phosphorus; D012822:Silicon Dioxide; D017886:Durapatite; D002118:Calcium; D000077215:Clay; C011934:mica; D012825:Silicon