Enamel rehardening by soft cheeses

The in situ rehardening effect by soft cheeses: unsweetened, sucrose-sweetened and strawberry marmalade-flavored, pH 4.5, 4.25 and 4.0 as compared to secreted saliva, was investigated on softened enamel. Ten volunteers wearing orthodontic removal appliances participated in the study. The intraoral test was chosen for measuring microhardness of enamel slabs inserted into the dental appliance. Average microhardness was calculated at three stages: at start (baseline), after exposing the enamel slabs to a citrus beverage (pH 3.3) for 30 minutes in vitro as a softening factor and then intra-oral exposure during 5 minutes to 125 g soft cream cheese mastication, unsweetened and sweetened (experimental), or to saliva secretion, pH 6.8, only by mouth movements (control). Significant rehardening effects on the softened enamel surfaces took place following mastication of the various soft cheeses and salivary secretion. The differences in the rehardening potentials of the cheeses as compared to that of saliva were significant. The rehardening effect of the cheeses decreased (not significantly) in the following order: unsweetened cheese, sucrose-sweetened marmalade flavored cheese and sucrose-sweetened cheese. In spite of the acidic pH of the soft cheese substrates,--the buffering capacity of the protein compounds and the Ca,PO4 ions neutralize a softening effect--the rehardening effect is probably due to an uptake of Ca and PO4 ions by the softened surface enamel from the cheese bolus consumed over the entire 5-minute period.