Variation in human salivary pellicle formation on biomaterials during the day.

Contact angle measurements were used to study the effects of pellicle formation on polymethyl-methacrylate, dental amalgam and gold. Samples were exposed to saliva in vivo for periods of 5-20 min at three separate occasions during the day. Pellicle drastically increased the wettability of all the materials and effectively sealed off the effect of the original surface activity. Variation in pellicle formation during the day was demonstrated. Pellicles formed at midday showed the least reduction in contact angles compared to those formed during the morning and afternoon. This difference coincided with an increased concentration of inorganic phosphate in saliva at midday. The method enables comparative studies of pellicle formation on hard biosurfaces. The findings indicate differences in the physical behaviour of saliva during the day, and illustrate the importance of making adhesion studies with this variation in mind.