Since cavities are caused by collaboration of sweets and flour products, literally everyone is subjected to this threat. Yet people with high carbohydrate and sugar diets and low fluoride water would naturally be much more vulnerable. While our saliva is a natural defence mechanism against the acids produced by the bacteria plaque, it cannot prevent tooth decay all alone. Diseases or drugs that supress salivation amount or flow also contribute to tooth decay. This is why dentists often recommend sugar free gums: they help increase salivation flow.