Root Canal, Cancer, and Terrorism

     Last year, I wrote a bit of satire applying some of the same arguments I've heard about abortion to root canal, in an attempt to show just how silly it is to bring moralizing arguments to bear on medical procedures. If someone needs treatment, they need treatment, and it's too late to argue about whether or not they ought to have engaged in the behaviour that led to that need. You can certainly argue about whether or not they do need the treatment, or whether the procedure itself is morally acceptable, or you can call attention to the risks and side effects involved, but that's a very different thing from saying, "Well, you should have thought of that before you [had sex/ate candy/went bungee-jumping/dressed that way]!"
     Anyway, in that piece, I alluded to this claim that root canal causes cancer, which is apparently still in circulation because a friend forwarded it to me recently. The big, bold headline:

97% of Terminal Cancer Patients Previously Had Root Canal Procedure

especially caught my eye, as of course it was meant to. You might think, given that I had a root canal about thirty years ago, and that I had a cancer that would have been terminal but for timely surgery, that I'd be inclined to find this at least credible. And yet, I'm unimpressed.

     First of all, the statistic isn't actually all that reliable. If you read the article, the source turns out to be a Dr. Issels, who simply recounts that in his 40 years of practice that many of his terminal cancer patients had the procedure. And maybe that many did, although it's just as likely he picked "97%" to emphasize "a lot". This is not a careful clinical study; the actual number could be wildly off.
     Even if the number isn't wildly off, it still doesn't mean anything other than that most of Dr. Issel's terminal cancer patients had had the procedure. There's no reason offered to think that 97% of all terminal cancer patients everywhere have had root canal. There could be any number of reasons why Dr. Issels' patients had a higher than average rate; perhaps he got a lot of referrals from an endodontist friend. Or perhaps the kind of person who puts off going to the dentist until a root canal is necessary is also likely to put off getting checked out for cancer until it's terminal. Or, maybe it's just that anyone who lives long enough to develop cancer has also lived long enough to make the odds of having had a root canal pretty high, as well.

     But that's only part of the problem with this statistic. Let's just assume for the sake of argument that it's completely accurate, that 97% of all terminal cancer patients have had a root canal operation. By itself, this still means nothing, because we have nothing to compare it against: how many people without cancer have had root canals?  According to the article itself, 41,000 root canal procedures are performed in the U.S. every day. (This is probably the source for that claim.) That's 15 million a year, for a population of 300 million people; on average, that means each person has one every 20 years. Obviously, some have more than their share, and many have none, but the point here is that root canals are extremely common. If 97% of everybody has had a root canal, then the fact that 97% of cancer patients have had it should come as no surprise. (Of course, for the reasons in the previous paragraph, I'd actually expect cancer patients to have had a somewhat higher rate of root canal than the population at large, if only because they tend on average to be old enough to have lost their baby teeth.)

     Enough of the statistics. Now some lay-person's background on the science. Root canal is basically a massive filling, where decayed bits of tooth are drilled out and replaced with artificial material. The difference is that in a routine dentist-visit filling, the cavity only goes into the outer layers of the tooth, and can be quickly patched up with a bit of gold or amalgam or whatever it is they use these days. In a root canal, the decay has reached into the softer living tissue inside where there are nerves and blood vessels and especially nerves, which is why ouch. So in a root canal, they have to clean out all that infected softer tissue, and then fill it all in with something to keep the rest of the tooth from breaking in when you chew. In the bad old days, they'd have to just yank out the whole tooth, but this is a way of saving as much of your original dentition as possible.

     So the claim in the article is that bacteria gets into the filled-in core of the tooth, and festers there, releasing toxins into your blood which cause cancer. I should say that this is not by itself completely ridiculous, because there are all sorts of things that can cause cancer, including viral and presumably bacterial infections. There's no reason to rule out the possibility that a long-term infection in the body (whether in a tooth or a bone or a wart or whatever) could promote cancers. And we know that abscesses are really nasty in lots of other ways (which is why we often need root canals in the first place).
     The part that doesn't make much sense, though, is how this is supposed to relate to root canals specifically, especially on the scale implied by the shock-inducing 97% claim. The problem is that if the filled-in tooth canal is sealed off enough to allow anaerobic bacteria to thrive, then it's probably also sealed off enough to keep them and their toxic byproducts away from the bloodstream.
     Moreover, bacteria are like any other living thing: they need energy, which those of us who can't photosynthesize have to get by eating things. So sealing off nasty microbes inside the tiny spaces of a tooth might give them a nice hiding place for a while, but they'd exhaust the available nutrients in there pretty soon, and then they'd starve.
     Of course, there may be just enough circulation of fluids to bring in a little food for the bacteria, to keep them alive, but that kind of bare subsistence infection isn't going to be able to do you much harm, either. The conditions after a root canal are not special, and there are no doubt many little colonies of germs trying to establish a foothold throughout your body at any given time. This is natural, and typically they don't last long, because we have immune systems. A big infection, like in an abscess, can overwhelm the defences, but a microscopic one is a pretty routine event, and at most a successful root canal replaces a huge potential abscess with some negligibly tiny germ hangouts.
     This is the thing that so many health panics don't seem to understand: germs are freaking everywhere. They aren't harmless at all, and they're trying to kill us all the time. But that's no big deal; that's how it's always been, and our immune systems and repair mechanisms are awfully good at what they do. They are more than capable of dealing with a Hole-In-The-Wall gang of bacteria hiding out at the site of a root canal, because they're always dealing with that sort of thing. Whether or not you've ever had a root canal, your immune system is right now dealing with exactly the same kinds of invaders and their associated toxins from some other source.
     The same argument applies to the mercury they once used as a preservative in vaccines, the fluoride in our drinking water, and a host of other unpleasant chemicals. Yes, we should try to minimize our exposure to these things, but when the amount we're worrying about is drowned out in the background noise of what our bodies are used to dealing with, it's time to go worry about something else. We are much better off trying to reduce that background noise than we are obsessing about a trivially small component of it. (Especially when it comes to things like root canal, fluoridation and vaccines, things which are specifically meant to give net health benefits that far outweigh whatever trivially tiny risks they might carry.)

     Which brings me to terrorism. Yes, terrorism exists, but it's really just a particular form of violence. There are, and perhaps always will be, people who believe that violence is a way to solve their problems. Sometimes they just get angry and lose control, or sometimes they coldly calculate that someone's death will bring them an insurance payoff, or sometimes they fall prey to a radical ideology. Whatever the cause, it's bad, but our civilization has developed systems for dealing with violence. People commit crimes, the police track them down, they stand trial, they go to prison. It's not ideal, but it generally works to keep us relatively safe (and it's worth repeating that we live in the least violent time in human history.)    
     The reason we shouldn't worry about terrorism is the same reason we shouldn't worry about getting cancer from a root canal: the actual incremental risk of being hurt or killed by a terrorist is many orders of magnitude lower than your already low risk of being a victim of criminal violence generally. We will do much more to improve our safety from violence, including terrorism, by adopting policies and attitudes which serve to make ours a more just, more compassionate, more connected community, in in which people do not become so alienated and disenfranchised that they turn to violence as a way of affirming their significance.