Fluoride released from glass-ionomer cement is responsible to inhibit the acid production of caries-related oral streptococci.
OBJECTIVE
Glass-ionomer cements (GICs) are known to have inhibitory effects on bacterial growth, but the biochemical mechanism of this property has not been fully understood. This study aimed to evaluate inhibitory effects of GIC on the acid production of caries-related oral streptococci, and to identify the components responsible for the inhibition.


METHODS
An eluate was prepared by immersing set GIC in phosphate-buffered saline at 37 degrees C for 24h. Fluoride and other elements in the eluate were quantified by fluoride ion electrode and atomic absorption photometry, respectively. Streptococcus mutans NCTC 10449 and Streptococcus sanguinis NCTC 10556 were used to evaluate the pH fall and the rate of acid production after the addition of glucose in the presence or absence of the eluate. Acidic end products from glucose were also assayed by carboxylic acid analyzer.


RESULTS
The eluate contained silicon (1.24+/-0.26 mM), fluoride (0.49+/-0.02 mM) and aluminum (0.06+/-0.00 mM), and inhibited the pH fall and the acid production rate of both streptococci at acidic pH, with a concomitant decrease in lactic acid production. These effects were comparable to those of a potassium fluoride solution containing the same concentration of fluoride as the eluate.


CONCLUSIONS
These results indicate that the GIC eluate inhibits the acid production of caries-related oral streptococci at acidic pH and that the effect is due to fluoride derived from the GIC. Thus, adjacent to GIC fillings, bacterial acid production and the subsequent bacterial growth may decrease, establishing a cariostatic environment.
Nakajo
Kazuko
K
Division of Oral Ecology and Biochemistry, Department of Oral Biology, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Sendai 980-8575, Japan.
Imazato
Satoshi
S
Takahashi
Yusuke
Y
Kiba
Wakako
W
Ebisu
Shigeyuki
S
Takahashi
Nobuhiro
N
D019342:Acetic Acid / Q000032:analysis / Q000378:metabolism; D002327:Cariostatic Agents / Q000494:pharmacology*; D005459:Fluorides / Q000494:pharmacology*; D005561:Formates / Q000032:analysis / Q000378:metabolism; D005899:Glass Ionomer Cements / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism; D006019:Glycolysis / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D017736:Ion-Selective Electrodes; D019344:Lactic Acid / Q000032:analysis / Q000378:metabolism; D013054:Spectrophotometry, Atomic; D013295:Streptococcus mutans / Q000187:drug effects* / Q000378:metabolism; D013298:Streptococcus sanguis / Q000187:drug effects / Q000378:metabolism
D002327:Cariostatic Agents; D005561:Formates; D005899:Glass Ionomer Cements; C030544:formic acid; D019344:Lactic Acid; D005947:Glucose; D019342:Acetic Acid; D005459:Fluorides