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Kinetics of Enamel Demineralization in vitro

Forsyth Dental Center, Department of Biomineralization, 140 The Fenway, Boston, Massachusetts 02115

Y.P. Zhang

Colgate-Palmolive Company, 909 River Road, Piscataway, New Jersey 08855-1343

C.Y. Lee

Yonsei University, College of Dentistry, Seoul, Korea

R.L. Kent, JR

Department of Biostatistics and Epidemiology, Forsyth Dental Center

E.C. Moreno

Forsyth Dental Center, Department of Biomineralization, 140 The Fenway, Boston, Massachusetts 02115

Previously, we reported that the rate (R) of hydroxyapatite dissolution in acetic, lactic, and phosphoric acid solutions is a function of the degree of saturation with respect to the dissolving mineral, DS (defined as the ratio of the mean ionic activity product for hydroxyapatite [Ca₅OH(PO ₄)₃] in solution to its solubility product constant), and the sum of the acid activities (B_iH) in solution: R = K(l-DS) ^m(B_iH)ⁿ. The present study was undertaken to explore the general validity of this model in describing the kinetics of enamel demineralization. Thin sections of human enamel were exposed to partially saturated 0.1 mol/L lactic acid solutions, at two different DS levels, and at pH values of 4.3 to 6.0. Thin sections of human enamel were also exposed to solutions with four different concentrations of acetic and lactic acids (pH 4.3) with three different DS values and, at one DS value, to solutions of propionic acid. Mineral loss was monitored by quantitative microradiography. In solutions with pH values of 4.3 and 5.0, "lesions" were formed with well-defined surface layers, whereas, in solutions with pH 6.0, "lesions" were produced with no apparent surface layers. The formation of relatively intact surface layers was consistent with predicted phase transformations. Rates of mineral loss were found to be inversely proportional to both the degree of saturation with respect to enamel mineral, DSEn, and the pH of the solution and increased with increased activities of each organic acid, consistent with the proposed model. However, at the same DS_En and acid activity, rates of demineralization were the same in the acetic and propionic acid solutions, whereas rates of demineralization in lactic acid were greater. It is suggested that specific interactions of acid species with enamel mineral may modify the rate of enamel demineralization. These in vitro findings suggest that relatively small differences in DS _En values found in plaque fluid may result in very significant differences in the rate of enamel demineralization in vivo.

Key Words: enamel • demineralization • caries mechanism

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Journal of Dental Research, Vol. 78, No. 7, 1326-1335 (1999)
DOI: 10.1177/00220345990780070701


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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Margolis, H.C. Articles by Moreno, E.C. Search for Related Content PubMed PubMed Citation Articles by Margolis, H.C. Articles by Moreno, E.C. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB CALCIUM COMPOUNDS CALCIUM, ELEMENTAL HYDROXYAPATITE LACTIC ACID Social Bookmarking                         What's this?