On the thickness and nanomechanical properties of salivary pellicle formed on tooth enamel

To determine the thickness and nanomechanical properties of salivary pellicle formed on tooth enamel.

In vitro adsorption experiments were conducted by immersing enamel samples in centrifuged saliva for 1min, and then the nanomechanical properties of the salivary pellicle/tooth enamel system were measured firstly using nanoindentation based on a continuous stiffness measurement technique. Finally, a model was proposed to obtain the thickness and the intrinsic nanohardness of this biofilm.

The composite nanohardness of salivary pellicle/tooth enamel system varied with indentation depth. The model can describe the experimental date at both shallow and deep indentation depths very well. The fitted average thickness of salivary pellicle was about 17nm, which was in good accord with the scanning probe microscopy experimental results. The intrinsic hardness of salivary pellicle and tooth enamel was about 0.52Gpa and 4.88Gpa respectively, which was consistent with previous studies.

It was convenient to extract intrinsic hardness and thickness of salivary pellicle from the indentation curve according to the model. Moreover, this model was applicable to plasticity-dominated behaviour of the soft film/hard substrate system.

The research results may be helpful to extend the understanding of our lubricating and anti-caries behaviours of salivary pellicle and to the oral hygiene industry for diagnose oral diseases.