This study assessed the protective potential of salivary pellicles formed in situ over periods ranging from 2 to 24 h. Pellicles were produced on enamel slabs mounted on the palatal aspect of removable acrylic splints and exposed to the oral environment in three subjects for 2, 6, 12 and 24 h. Enamel specimens with and without pellicles were immersed in citric acid (1%) for 60 s, and the amount of dissolved calcium was measured by atomic absorption spectroscopy. In addition, specimens were processed for transmission electron microscopy (TEM). Mean values (standard deviations) for calcium release (mg/l related to the specimen's surface area of 5 x 5 mm(2)) were: 2-h pellicle 6.94 (1.55); 6-h pellicle 6.69 (2.05); 12-h pellicle 6.57 (2.31); 24-h pellicle 5.71 (2.46); enamel without pellicle 8.95 (1.66). There were no significant differences in calcium release that were dependent on pellicle formation time, but in comparison to enamel specimens without pellicle, significantly less (p <0.05) demineralization of the enamel was observed in pellicle-covered specimens. TEM showed that the pellicle was partly, but not completely dissolved following acid exposure. It is concluded that even a 2-h in-situ-formed pellicle layer protects the enamel surface to a certain extent against demineralization.
