I don't eat sweets, why do I get decay?: Dr Ian Kelly, Dentist
We would obviously have to consider your diet, sweets obviously containing sugar that will have an impact. Fizzy drinks - anything basically that fizzes is acidic and the presence of acid in the mouth will weaken teeth, maybe leading to decay.
We would also have to consider oral hygiene, and again, if we're not removing plaque competently then there will be a decay risk as a result of that.