Once plaque has been formed, only flossing can help. Gargling or the use of a finger would not help at all. Tartar is calcified plaque. If you allow plaque to set for 48 hours, the calcium from the plaque gets deposited on the plaque, and tartar is formed. Tartar can be removed only by a dentist.
Adolescents are particularly susceptible to cavities.
At this age, one tends to snack very often during the day, most of it being junk food like biscuits and wafers. Also, at this age, the tooth is not fully mature. The second permanent molars and pre-molars are not yet fully calcified, leaving the pits and fissures quite open. Frequent snacking on junk food can worsen the situation. Elderly people, on the other hand, age fifty on, are susceptible to root caries.