XKCD says that the dental X-ray (5 μSv) is half the average daily background radiation dose (10 μSv), and 1/8th of a cross country flight (40 μSv). To me this means that the radiation exposure is quite irrelevant in the grand scheme of things. (https://xkcd.com/radiation/)
If this were false, it would presumably be because dental X-rays are especially harmful in some way that isn't just "because of radiation".
You can drown in a river that's on average 20 centimeter deep. Understanding how radiation causes permanent damage isn't easy.
There are models that suggest it causes permanent damage if enough damage is done within one cell that the cell repair mechanisms can't easily repair the damage in a short amount of time.
That suggests radiation for a small amount of time on a small area of the body is more problematic then average background radiation that's the same over a longer time frame and goes towards the whole body.
From https://seer.cancer.gov/statfacts/html/thyro.html, new thyroid cancer cases occur at a rate of ~15 cases per 100k people per year, and the disease has a 98+% 5-year survival rate.
Compare that with whatever risk results from needing more invasive repair when your dentist can't detect the cavities as soon, and you can see if there's a net benefit. I'm not seeing any numbers on this in my 5 minutes of searching, but that doesn't mean they're not out there. But I suspect the connection between dental infections and heart disease (that any dentist will tell you all about if you ask) easily exceeds the increased risk from regular x-rays.
I think this is a pretty compelling point, but:
As I mentioned above, I'm still leaning towards okaying the imaging, but also think the default policy of every two years they use may be too aggressive for me, given the absence of any cavities up till now.
You can reduce the risk of cavities. X-ray technology was invented in Germany, where I live, and they have had a history of regulating its use. I have my teeth checked twice a year and have never been asked to get an x-ray. This is in contrast to my experiences growing up in the American continent, where, despite all the x-rays, I developed a lot of cavities. Using an electric toothbrush, buying toothpaste with a small amount of fluoride and flossing twice a day have been effective for me in drastically reducing the risk of cavities and obviating the need for x-rays (a diet change may have also helped). That despite my teeth being so tightly packed I destroy dental floss. I think I've only had a cavity once in the last ten years and it was picked up early during a scheduled check up and dealt with promptly.
The German Bundesamt für Strahlenschutz (yep, there is one) offers this booklet to keep track of your exposures and ensure you do not exceed a threshold: https://www.bfs.de/EN/topics/ion/medicine/diagnostics/x-rays/record-card.html . Maybe it will be useful to you
I also came here to say that I've never had a dentist even suggest an x-ray in the course of a routine checkup (living in Finland). The only time I recall having had one taken was when I had an issue of grinding my teeth while sleeping, and they did some extra investigation.
I too want to say that my dentist never even suggested getting an x-ray during a routine check up.
I’ve had a dental x-ray once but it was when looking into a specific problem.
I didn’t have any cavities in years. Back when I had cavities dentist found them by looking at my teeth no x-ray needed.
| Case/Control | Cases % | Controls % | OR | 95% CI | P-value | |
|---|---|---|---|---|---|---|
| Dental x-ray | ||||||
| No | 208/255 | 66.7 | 81.7 | 1.0 | – | |
| Yes | 104/57 | 33.3 | 18.3 | 2.1 | 1.4–3.1 | 0.001 |
| Number of dental x-rays | <0.0001* | |||||
| 1–4 | 75/43 | 72.2 | 75.4 | 2.2 | 1.4–3.5 | 0.001 |
| 5–9 | 16/4 | 15.4 | 7.0 | 4.6 | 1.4–14.7 | 0.01 |
| 10+ | 11/3 | 10.6 | 5.3 | 5.4 | 1.1–26.7 | 0.037 |
This is the money shot, copied and pasted from the article, with the key stat in row 2.
But the tails on the data for higher exposures are insane. I think I've been imaged every two years on average--seems to be standard of care at USA dentist offices. So between ages 18 and 38, I received ~10 x-ray exposures.
Google led me to this meta, which led me to this 2013 study, which found:
We observed a 13% increase in thyroid cancer risk for every 10 reported dental radiographs (hazard ratio = 1.13, 95% confidence interval: 1.01, 1.26), which was driven by dental x-rays first received before 1970, but there was no evidence that the relationship between dental x-rays and thyroid cancer was associated with childhood or adolescent exposures as would have been anticipated. The relationship between dental x-rays and thyroid cancer risk was surprising because we found no evidence of an association of thyroid cancer with other types of diagnostic x-rays characterized by higher radiation exposure than dental x-rays.
Per my layperson's understanding, Memon found that for each person with thyroid cancer who had had no dental x-rays, there were between 1.1 and 26.7 people with thyroid cancer who had had ten or more dental x-rays (yes, I know, low confidence interval), and Neta found that a person with ten dental x-rays had a 13% higher risk of getting thyroid cancer as someone without.
Neta cites Memon and claims various methodological advantages over Memon. Maybe they are relevant to your analysis?
I never get them -- not for two decades. I have very strong teeth and everything has been fine. But I was quie confident. If I had regular cavities I would get it done. YMMV.
Likelihood of cancer -- quite low; cost of getting it -- quite high.
Likelihood of cavities -- higher; cost of getting them -- lower.
It's hard to figure small numbers times big numbers when you don't really have either. :)
A small Kuwaiti study used a conditional regression to found that x-rays are an increased risk factor for thyroid cancer (n=313, odds ratio = 2.1, 95% confidence interval: 1.4, 3.1) using a case-matched methodology.
X-rays being a carcinogen isn't surprising. Every time I've gone into my dentist they've tried to image my head. I've never had a cavity, and I generally decline the imaging; their recommended cadence of every two years has seemed too aggressive to me, in the past.
I've got my first dental appointment in more than 18 months next week, and.. I'm inclined to let them image. How should one think about this sort of risk/benefit trade off? Presumably catching a cavity or other issue early is [much?] better. But that itself assumes that the dentists who'd be treating you don't do more harm than good.