Gum containing calcium fluoride reinforces enamel subsurface lesions in situ.

The aim of this study was to assess the effect of chewing gum containing phosphoryl oligosaccharides of calcium (POs-Ca) and a low concentration of fluoride (F) on the hardness of enamel subsurface lesions, utilizing a double-blind, randomized, and controlled in situ model. Fifteen individuals wore removable lingual appliances with 3 bovine-enamel insets containing subsurface demineralized lesions. Three times a day for 14 days, they chewed one of the 3 chewing gums (placebo, POs-Ca, POs-Ca+F). After the treatment period, cross-sectional mineral content, nanoindentation hardness, and fluoride ion mapping by time-of-flight secondary ion mass spectrometry (TOF-SIMS) were evaluated. Although there were no statistical differences in overall mineral content and hardness recovery rates between POs-Ca and POs-Ca+F subsurface lesions (p > 0.05), nanoindentation at 1-μm distance increments from the surface showed statistical differences in hardness recovery rate between POs-Ca and POs-Ca+F in the superficial 20-μm region (p < 0.05). Fluoride mapping revealed distribution of the ion up to 20 μm from the surface in the POs-Ca+F group. Nanoindentation and TOF-SIMS results highlighted the benefits of bioavailability of fluoride ion on reinforcement of the superficial zone of subsurface lesions in situ (NCT01377493).