Plaque is a soft white layer which forms on teeth, containing large amounts of bacteria of various types, particularly Streptococcus mutants. Left unchecked for a few days plaque will harden, especially near the gums, forming tartar.

 

Certain bacteria in the mouth live off the remains of foods, especially sugars. In the absence of oxygen they produce lactic acid, which dissolves the calcium and phosphorus in the enamel in a process known as demineralization. Enamel demineralization takes place below the critical pH of about 5.5.

 

Saliva gradually neutralizes the acids which cause the pH of the tooth surface to rise above the critical pH. This causes re-mineralization, the return of the dissolved minerals to the enamel. If there is sufficient time between the intake of foods (two to three hours) then the impact is limited and the teeth can repair themselves.