Some decay starts between the teeth or under old fillings, where no mirror can see it. Small bitewing X-rays show those places, and the bone that holds the teeth.
We take them every one to two years for most adults, more often if you have a lot of decay, and only when the result will change what we do. The dose is very small.
You can see your X-rays on the screen in the surgery, and we are happy to send copies to another dentist if you move.