Electrostatic

Electrostatic force is the means by which dental tartar is held together. 

The science behind the force (F) of the attraction is represented in the following equation:

where r is the separation distance and ke is a proportionality constant. A positive force implies it is repulsive, while a negative force implies it is attractive. The proportionality constant ke is related to defined properties of space and can be calculated based on knowledge of empirical measurements of the speed of light