Methods: Twenty bovine tooth slabs (4 x 5 mm) were mounted in resin blocks exposing only the enamel surface. Half of the exposed enamel on each block was coated with acid-resistant nail varnish (control). The specimens were then divided randomly into four groups and exposed to one of the following protocols for six days: Group 1: continuous 10 min orange juice (OJ) exposure (pH 3.8 ± 0.5) followed by 10 min deionised water. Group 2: continuous 10 min OJ exposure followed by 10 min saliva. Group 3: ten 1 min OJ exposures alternating with ten 1 min deionised water exposures and Group 4: ten 1 min OJ exposures alternating with ten 1 min saliva exposures. Specimens were stored in remineralising solution between acid exposures. Sections were cut and ground (0.12-0.14mm) and transverse microradiography was used to measure mineral loss. Average loss was compared across groups, with 95% confidence intervals (corrected for multiple comparisons) used to identify between which groups there was a significant difference.
Results: The mean mineral loss in Group 4 was significantly higher than in Group 2 (95% CI: 44.9 to 59.8 microns), whilst mean mineral loss in Group 3 was significantly higher than in Group 4 (95% CI: 10.3 to 25.2 microns). There was no significant difference between Groups 1 and 2 (95% CI: -6.7 to 8.2).
Conclusions: Repeated exposure to an acidic drink resulted in greater mineral loss than continuous exposure. The clinical implication of this confirms that repeated sipping of acidic beverages is probably more detrimental to the mineralised tissues than a single exposure. The role of saliva is not clear.