My dentist shows me the xray they take once every 5 years. Then they walk me through what a cavity would look like. Then they show me that i have none.
I can understand that the external "poke at it" method requires some judgment, but an xray shouldn't have that much variance.
That's why I also go get a "poke around and look" checkup every year. The X-ray is to spot deeper things, but you can't do that every year without the x-rays becoming a risk factor themselves.
In the United States, it is routine to get your mouth X-Ray’ed every 6 months when you go in for a cleaning. Dental plans include these checkups at no extra charge.
That's what I was led to believe by my dentist when I asked. I just checked danish national guidance, and they say the dose of x-rays is so low the increased risk is incalculable. Instead they say the dentist should only ever use an x-ray if they find it medically necessary out of a principle of minimization.
So it sounds like it's the individual dentists judgment, and their organizing body says that they base it on the occurrence of dental problems in the population the clinics they oversee, with some adjustments based on patient age and risk factors.
So according to Danish authorities, you should be safe getting x-ray'ed every 6 months. They just don't recommend it, since it's a waste.
I can understand that the external "poke at it" method requires some judgment, but an xray shouldn't have that much variance.