The "Physical Theories as <Blank>" meme continues to ricochet its way around the science blogosphere, with entries from Chad and Emmy, Confused at a Higher Level, and Steinn's personification of physical theories as characters in the Harry Potter books over at Dynamics of Cats. It could go on forever at this rate! The various humorous iterations -- and ongoing comment threads -- provided some welcome distraction, as this was the week one of my teeth decided it was time to die. Did it embrace its fate with quiet dignity? It did not. My tooth refused to go gentle into that good night, and instead went kicking and screaming into oblivion ("Why me? Why now? Why, Flying Spaghetti Monster, why?!??"). Apparently it had so much to live for....
My dentist finally put the tooth out of its misery yesterday morning with emergency endodontic therapy, more commonly known as a root canal. And since this has been a week of following memes, I decided to blog about my medical procedure, because all the cool SciBlings are doing it: Abel Pharmboy liveblogged his own vasectomy last year, Janet Stemwedel just blogged about her mammogram, and PZ Myers is threatening to blog the colonoscopy he has slated for next week. (Go on over to Pharyngula and encourage him to do so! C'mon, it's PZ, so you know it'll be irreverent and funny. Maybe there will be pictures!) These are all common medical procedures that tend to give us the heebie-jeebies, and blogging about the gory details can help remove some of the associated fears -- because we mostly fear the unfamiliar. Root canals are one of the most dreaded dental procedures, so I figure I'm performing a public service, as well as cathartically venting my pain.
Because damn, it was painful -- not the procedure, thanks to the generous application of Lidocaine (lovely, lovely Lidocaine!), but the death throes of my expiring tooth that led up to the procedure. It's easy to forget that teeth are not just static bits of bone embedded in our jaws; they are a crucial functioning part of the human body. They're hollow, for starters, and contain a mass of soft tissue known as pulp that includes nerves and blood vessels and connective tissue. The pulp is vital to maintaining tooth health, since it keeps the tooth supplied with nutrients and moisture. And it alerts the body when something goes horribly wrong: a cavity, or an infected abscess, for example. Pain is a message from the body saying "FIX ME!" 
That mass of nerve tissue is rather pink and worm-like in appearance, which is ironic when you consider that a Sumerian text from 5000 BC describes tooth decay as resulting from a "tooth worm" -- a belief that spans several cultures (India, Egypt, Japan and China) and persisted into the Western European Age of Enlightenment. There is evidence of rudimentary dentistry techniques dating as far back as 7000 BC, although the father of modern dentistry is 17th Century French physician Pierre Fauchard, who was the first to treat cavities with dental fillings. (According to the Code of Hammurabi, dating to the 18th century BC, tooth extraction was a common form of punishment. That probably doesn't count as "dentistry.")
Of course, we now know that the nerve is not an invasive worm responsible for tooth decay, but the actual victim of such decay, brought about by invading acid-producing bacteria. A root canal removes that soft tissue, which ends the pain, but also removes the blood supply to the tooth, undermining its structural integrity. That's why most dentists follow a root canal with an expensive porcelain crown.
Anyway, a dying tooth isn't always painful. I've only had one other root canal, and I didn't even know the nerve tissue had died until it -- ahem -- started rotting in place, causing an icky infection. It didn't actually hurt, but something was clearly wrong. When I called my dentist, the assistant, George, asked me to describe the sensation.
Me: "Well, it feels kinda spongy when I bite down..."
(*pause*)
George: "Okay, that's very bad...."
Maybe it was (I had an infected abscess, which complicated matters), but it wasn't painful. But my most recently deceased tooth caused quite the ruckus. It started as a bit of sensitivity whenever I bit down in a certain area, and then progressed to a mild dull ache -- which is when I consulted with my dentist. Whereas before, I sought help quite late, in this case, I was a wee bit early. The x-rays showed nothing amiss, except the replacement filling done last year was ominously close to the nerve. So my dentist sent me home with a prescription for Tylenol with codeine, and told me to call him when the pain "localized" and/or became unbearable.
Does that sound a bit cold and uncaring to you? It's not; my dentist was being responsible and cautious. Turns out it can be rather difficult to pinpoint exactly where the pain originates when it comes to teeth. The reason is anatomical, per my friend (and former jujitsu instructor) Kent, who is himself a dentist. He was still in dental school when I became his student, and invited me to the dissection lab one Saturday morning to practice joint locks on cadavers -- yes, it sounds morbid, but it's easier to understand why certain techniques work with a peek into the body's underlying structure. That's also when I learned that dental students are required to study not just the structure of the head and neck, but the entire upper torso, because a problem with one's teeth or gums can actually affect many different parts of the body one might never suspect were connected.
See, nerves don't exist all by themselves; they're part of a complex system that includes connective tissue and blood vessels; where there's a blood vessel, you can be sure to find at least one nerve accompanying it. Bunches of nerves and vessels are collected into so-called neurovascular bundles, like the intricate roots of two intertwining trees. The "nerve" inside a tooth is a neurovascular bundle, and when it gets inflamed, this sometimes affects the neurovascular tissues all along the course of the nerve trunk. So pain emanating from on tooth may be felt in another tooth altogether -- or even in the ear, eye, or temple, since the Trigeminal nerve on each side of the head branches out to all those areas -- leading the dentist to treat the wrong tooth, particular if (as in my case) there is no clear evidence of a problem on the x-rays. Freaky!
Root canals are expensive and time-consuming, so it's in everyone's best interest to make sure they've got the right tooth. I went home and nothing much happened for five days. Then, almost overnight, the tooth went from being just a wee bit sensitive, to being that hysterical hypochondriac everyone tiptoes around for fear of setting him/her off. ("What's that you're drinking now? Pure filtered water carefully warmed to room temperature? ARE YOU TRYING TO KILL ME?!?? Why not just drink battery acid?")
The pain went from a barely noticeable light, dull ache, to a throbbing undercurrent of inflamed rage, punctuated by vengeful outbursts of excruciating pain. I'm pretty stoic when it comes to physical discomfort; yet that damned tooth had me curled up in a fetal position and whimpering quietly at 3 AM, waiting for the fistfuls of codeine to kick in so I could sleep. Had I been of a religious bent, I might have found myself praying to Apollonia, the Roman Catholic patron saint of dentistry. But I'm not, so I mostly moaned through my distress.
At least now we could be sure I had "localized" the pain to the appropriate tooth, and my dentist hastily scheduled an appointment for my procedure. Never have I been so happy to receive a shot of Lidocaine; in fact, I thanked the dental assistant, who stared at me in shock and stammered, "No one has ever said thank you before...." I actually got a little extra Lidocaine, just to be on the safe side. Inflamed tissue tends to be a bit acidic, and this can slow or stop the diffusion of the anesthesia through the nerve fibers. Lidocaine is the most common anesthetic used today, replacing nitrous oxide (laughing gas) and Novacain, if not the odd shot of whiskey in a pinch (a perennial favorite). Back in 1884, Dr. William Steward Halsted injected cocaine into a sensory nerve trunk as a surgical anesthesia, and while the patients probably enjoyed the accompanying euphoria, the highly addictive nature of cocaine meant it was quickly replaced by other forms of anesthesia.
The actual procedure for endodontic therapy is pretty straightforward. Once I was all numbed up, my dentist opened up the tooth and removed the nerve tissue and blood vessels (pulp), scraped it all clean, decontaminated the hollowed-out chamber, and then filled it with gutta percha -- carefully taking x-rays each step of the way to make sure (a) all the pulp was removed, and (b) the material filled the entire cavity all the way down to the ends of the deepest roots. Then he plugged up the hole with cement. I go back next week for the porcelain crown procedure, but in the meantime, the worst is over. If I were a truly dedicated blogger, I would have pix and videos to post. I'm not that dedicated. But you can watch a sample procedure here, with the sound of the drilling and scraping mercifully removed -- that tends to be what freaks people out when it comes to visiting the dentist.
However, apparently there's a new technique being developed that could reduce the need for drilling and filling by catching tooth decay before it gets so advanced, it requires major dental intervention. It's based on Raman spectroscopy, a technique used to distinguish between different chemicals by identifying each molecule's unique spectral fingerprint. The technique points a tiny optical fiber at each individual tooth, and if there' decay, the chemical changes in the tooth would be detectable by analyzing how the light is scattered when a laser is fired at the tooth. (Bacteria responsible for tooth decay scatter light differently than healthy teeth.) The dentist can then "remineralize" the area before a filling becomes necessary. Conventional x-rays usually don't detect decay until it's too late.
Hmmm. I predict it might be a helpful addition to the dentistry toolkit, but cavities are kinda inevitable. Sooner or later, you'll still find yourself in that dentist's chair, nervously awaiting the dreaded drill. And when that day comes, remember to thank your hygienist who administers the anesthetizing shot for his/her trouble. It'd hurt a hell of a lot more without it.
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