How many dental xrays per year, for routine checks, is ok for a child?

Least is best: As few as necessary. Effects of x-rays are cumulative over time.

Depends: I believe visual exam can tell a dentist if x- rays are needed in a child and if so how many. Even though digital dental x rays are safe as part of routine check up, if they can be avoided why not? If we see dental cavities visually then we need to do x ray to determine depth of it. 4 to 8 x rays per year ( depending on how many teeth have erupted and child's age) is average.