As damaging as plaque can be, it is easily removed by mechanical brushing. Plaque deposits build up on the teeth fairly quickly after eating and drinking, and if they are not brushed away at least twice a day, they can lead to tooth decay and periodontal disease. It takes just one day for bacteria to build up enough to make your mouth susceptible to disease.
If plaque is not removed, it hardens and becomes calculus (tartar). Calculus cannot be removed with regular brushing. Your hygienist has special instruments designed to remove tartar.
Tooth decay is caused by a combination of plaque and sugar. Though everyone is aware of sugar in candy and desserts, many people don't realize other sources of sugar may be in their diet. Sodas are a leading offender (diet sodas won't promote decay; artificial sweeteners will not harm your teeth) as well as gum, cough drops, peppermints (and other hard candies), sweet tea... the list goes on.
We are not asking people to give up all sugar (we like it ourselves). Just be aware that it is the frequency (or duration) that the sugar is put in your mouth, not the quantity, that is harmful. Example: The person that sips on a can of coke all day at his/her desk is doing far more damage to their teeth than someone who drinks an entire 2-liter bottle at lunch. Another good example is the person who slowly lets a peppermint dissolve in their mouth for 30 minutes versus someone who eats a whole bag of Snickers in 10 minutes.