Lipoteichoic acid inhibits remineralization of artificial subsurface lesions and surface-softened enamel

Dental plaque produces not only acids by which underlying enamel is demineralized but also compounds which may inhibit repair of the lesions. The aim of this study was to determine how lipoteichoic acid, a bacterial compound that is abundant in dental plaque and inhibits calcium phosphate precipitation in vitro, affects the remineralization of incipient enamel lesions. Subsurface and surface-softened lesions were made in thin sections of bovine enamel, incubated with various amounts of lipoteichoic acid (isolated from Lactobacillus casei), and remineralized in 1.5 mmol/L CaCl2, 0.9 mmol/L KH2PO4, 130 mmol/L KCl, and 20 mmol/L Hepes, pH 7.0. Remineralization was followed during several weeks by repeated microradiography of the sections, and characterized by the changes in the integrated mineral loss of the lesions and the differential mineral profiles. The results showed that: (1) the effects of lipoteichoic acid on lesion remineralization were dose-dependent; (2) in subsurface lesions only the highest dose of lipoteichoic acid affected remineralization, which was delayed throughout the lesions; and (3) in surface-softened enamel, lipoteichoic acid did not affect the remineralization of the deeper parts, but remineralization of a surface zone of from 25 to 30 mu m was increasingly inhibited with increasing doses. These effects were explained by different permeabilities of the surfaces of both types of lesions for the inhibitor: In subsurface lesions, lipoteichoic acid may have mainly clogged the porosities in the surface layer, whereas it could penetrate substantially into surface-softened enamel.