Method: In the softening study, human enamel specimens were polished and divided into five groups. The treatments were a) experimental mouthrinse, b) deionised water and c - e) three commercial US mouthrinses. Specimens were incubated in one of the treatment solutions for 1min before baseline surface microhardness measurements (SMH) were made (Vickers). The enamel was subsequently immersed in 1% citric acid pH 3.8 (an orange juice mimic) for 10mins, and SMH measurements repeated. Specimens were then placed back into citric acid for another two cycles of 10mins, with SMH measurements being performed after a total of 20 and 30mins acid exposure. In the rehardening study, artificial erosive lesions were prepared by exposure of enamel to citric acid (same composition as above) for 30mins. The specimens were then divided into five groups and SMH measurements performed. Treatments were performed as above and the enamel subsequently placed into mucin-free artificial saliva to which a small quantity of the appropriate treatment solution had been added. Modification of the saliva was performed in order to mimic in vivo carryover of the formulations. Specimen rehardening was determined using microindentation after 24 and 48hrs.
Result: In the softening study, the experimental mouthrinse was statistically superior to all other mouthrinses and the deionised water control in preventing enamel softening. In the rehardening study, after 24 and 48hrs incubation in artificial saliva, the experimental formulation was again statistically superior to all other treatments in promoting enamel surface rehardening.
Conclusion: These studies have shown the experimental mouthrinse to be statistically superior to a number of marketed US mouthrinses in preventing citric acid induced damage to enamel, and additionally in rehardening artificial erosive lesions.