anecdote on their usefulness.
I recently had my yearly inspection, _without_ xrays (which she said it was probably about time for "next time").
A month later, I had pain in a rear molar, and went for a checkup. They reacted "that is not good, because that tooth is root-treated - no nerves, so pain from a place without nerves is not good".
They then did an xray, which revealed the tooth had started rotting - a lot - inside, from below.
They advised extraction - now a week ago. It turned out the tooth had a hidden fracture in the roots. It was not visible on the xrays - only its hollowing result - but evident once the tooth was out; it came out in two pieces.
Just an anecdote, but this would be caught by the 2-3 year xray, and because of the missing nerve, it was pretty bad/serious when I finally felt it myself.
I'm not advocating the yearly xray, but the semi-annual makes sense to me.
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