Silica-induced precipitation of calcium phosphate in the presence of inhibitors of hydroxyapatite formation.
The promotion and the inhibition of hydroxyapatite formation by various substances were determined by measurement of the induction time of spontaneous precipitation (ti) from supersaturated solutions. Silica was found to decrease ti in Hepes-buffered (pH 7.2) supersaturated solutions with a wide range of calcium-to-phosphate ratios and concentrations. Also, in suspensions of the oral bacteria S. mutans or C. matruchotii in 1 mmol/L calcium, 7.5 mmol/L phosphate, and 50 mmol/L Hepes (pH 7.2), silica was capable of stimulating precipitation. Macromolecules derived from these bacteria by freezing and thawing appeared to be strong inhibitors of calcium phosphate precipitation. In the presence of silica, the effects of these bacterial inhibitors could be partially overcome, which supports the idea that silica in dental plaque is a promoter of calculus formation. In contrast, inhibition of calcium phosphate precipitation by a low-molecular-weight inhibitor, pyrophosphate, could not be counteracted by silica.
Damen
J J
JJ
Department of Cariology and Endodontology, Academic Centre for Dentistry Amsterdam, (ACTA), The Netherlands.
Ten Cate
J M
JM
D001426:Bacterial Proteins / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry; D011232:Chemical Precipitation; D003352:Corynebacterium / Q000737:chemistry; D003460:Crystallization; D011756:Diphosphates / Q000737:chemistry; D006882:Hydroxyapatites / Q000737:chemistry*; D046911:Macromolecular Substances; D012822:Silicon Dioxide / Q000737:chemistry*; D013295:Streptococcus mutans / Q000737:chemistry; D013347:Subcellular Fractions / Q000737:chemistry; D014961:X-Ray Diffraction
D001426:Bacterial Proteins; D002130:Calcium Phosphates; D002241:Carbohydrates; D011756:Diphosphates; D006882:Hydroxyapatites; D046911:Macromolecular Substances; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C022045:octacalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; D012822:Silicon Dioxide; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous; C494366:calcium phosphate, dibasic, dihydrate