Insomniac minds want to know: why do sweet foods increase toothache pain
At my last dentist appointment a couple of months ago I was diagnosed with "Cracked Tooth Syndrome", was evaluated for root canal and was subsequently scheduled for a crown, which is scheduled for July.
The affected tooth originally was just sensitive to extreme cold and also to extreme pressure. Nothing else bothered it. But lately it's started to ache when I have really sweet food. When I'm done eating the sweet food, the pain goes away instantly. So it's not like I eat something sweet and I'm in pain for a while - which if that had been the case, I probably wouldn't have questioned, figuring that the sweet food had more sugar, that caused more decay. But it's only while I'm in the process of eating sweet food - and only sweet food (not salty, not spicey, not sour) - that it hurts. Which made me wonder. temperature and pressure sensitivity I get, but how can sweet food cause pain?
The trusty Wikipedia turned up empty, and Webmd.com only got me so far:
"To reduce pain and swelling of a toothache, use an ice pack on the outside of your cheek; do not use heat. Avoid very hot, cold, or sweet foods and drinks if they increase your pain."
My next stop on the internets was to a site I'd never heard of called medicinenet.com. They were a bit more informative, explaining
"Tooth sensitivity occurs when the underlying layer of your teeth - the dentin - becomes exposed as a result of receding gum tissue (the protective blanket that covers the tooth roots). The roots, which are not covered by hard enamel, contain thousands of tiny tubules leading to the tooth's never center (the pulp). These dentinal tubules (or channels) allow the stimuli - for example, the hot, cold, or sweet food - to reach the nerve in your tooth, which results in the pain you feel."
But I still didn't really have my question answered. What about sweet food causes the pain? I can feel temperature and pressure, but I can't feel sweet food. Why would sweet food make my tooth hurt more while I'm eating it? Why wouldn't it just be ALL food?
I hunted around on the site a bit more, and found this:
"Certain bacteria in the mouth convert simple sugars into acid. The acid softens and (along with saliva) dissolves the enamel and dentin, creating cavities. Small shallow cavities may not cause pain and may be unnoticed by the patient. The larger deeper cavities can collect food debris. The inner living pulp of the affected tooth can become irritated by bacterial toxins or by foods that are cold, hot, sour, or sweet-causing toothache. "
but it still didn't explain to me why foods that are sweet would cause my tooth to ache.
A visit to one of my other favourite reference sites, howthingswork.com, turned up basically the same information as the previous site.
Likewise, for the ADA web site. More of the what, and how, but not why.
I found this tidbit on my next stop on the internets, 21stcenturydental.com:
"Cracked tooth syndrome (CTS) is a very common problem that affects teeth that have large fillings in them, although the syndrome can also occur in teeth with no fillings at all. Typically, CTS may involve either of the following:
- a tooth with a large restoration where the crack runs under a weakened cusp (that raised part of your tooth)
- a tooth with minimal or no filling material where the tooth has been subjected to heavy biting forces or grinding - After grinding for years, you can wear down your canines (eye teeth), which function to protect your other teeth when grinding. As this occurs, your teeth will be at an increased risk for CTS.
- teeth that have suffered trauma
Why does your tooth hurt when biting? Assuming this is due to CTS, your tooth is flexing, which microscopically stimulates the nerve in the tooth. These hairline cracks open when biting down, and then close upon releasing your bite. This movement applies pressure on tubules that run down the nerve of the tooth causing fluid to push and pull on the tooth's nerve, resulting in pain. Additionally, the nerve in the cracked tooth is being exposed to bacterial toxins, which can allow infection to spread to the nerve and bone tissue underneath, resulting in an abscess.
What symptoms should you be aware of? Pain upon release of biting pressure is the most likely, although simply biting down (especially when biting on grainy foods) in “just the right spot” can be the first sign. Temperature changes that create this “zinger” can also be something to watch for, as well as sweet sensitivity."
Good info about my cracked tooth but alas, still no why, regarding the sweet sensitivity.
So I reconsidered the question. The question was really about what causes a nerve to be stimulated by sweet food; or what about sweet food stimulates nerve endings?
I decided to search on nerve stimuli and found myself back at the trusty wikipedia site.
The wikipedia article I had found was about "Free nerve endings". It sounds a bit like a slogan on a sign for an anti nerve ending enslavery march. But it's entirely different.
"A free nerve ending (FNE) is an unspecialized, afferent nerve ending, meaning it brings information from the body's periphery to the brain. Free nerve endings are unencapsulated and have no complex sensory structures, unlike those found in Meissner's or Pacinian corpuscles. They are the most common type of nerve ending, and are most frequently found in the skin. They penetrate the epidermis and end in the stratum granulosum. These nerve endings are responsible for detecting temperature, mechanical stimuli (such as pressure), pain (nociception), and information about touch. Some FNEs can also detect stretch stimuli."
Ok - so temperature, pressure, and stretch are all ones that I understood and have since the onset of this quest for knowledge. What about sweet foods is a stimuli for nerve endings...
About an hour and several wiki articles later, I found myself learning about the somatosensory system, which again talked all about pressure, temperature, and pain.
So while I now am much more knowledgeable about the human nervous system and the leading causes of tooth pain (as well as several home remedies, several of which sound quite dubious) I still have no answer to my original question.
After finally heading to bed and trying unsuccesfully to sleep (seems I've got another cold and the usual annoying sinus congestion that accompanies it), I got up and attempted one last search: "dental nerve stimuli". Among the results was an article about Dentin Hypersensitivity.
Having already become quite knowledgeable about dentin,the dentinal tubule, and the pulp, as a result of my previous research, this information seemed to be leading me a bit closer to a thorough explanation:
"Hypersensitive dentin is characterized by transient pain in response to evaporative, tactile, thermal, or chemo-osmotic stimulation of exposed dentin in teeth where no other defects or pathology exist.
Exposed root surfaces are prone to abrasion from aggressive toothbrushing, erosion from contact with acidic substances, and hypersensitivity from exposure of open tubules to the oral environment. The dentinal tubule is the portal through which stimuli gain access to the pulp. The odontoblasts and associated nerve fibers are able to detect dentinal fluid movement. Apparently very little is required to disturb and, in some cases, actually move odontoblasts and their associated pulpal nerve fiber endings into the proximal ends of the dentinal tubules.
The hydrodynamic theory, which was proposed in the 1950s, focuses on the movement of fluids within the dentin and pulp, which stimulate the nerves causing pain. This increased flow, in turn, causes a pressure change across the dentin. The pressure excites the nerves in the tooth, which transmits signals to the pulp where the sensitization is registered by the same depolarization neural discharge mechanism that characterizes all nerve activity. External stimuli result in hydrodynamic changes affecting the pulpal balance and can elicit pain."
The movement of fluids within the dentin and pulp is, according to this theory, what stimulates the nerves causing pain. So what about sweet foods stimulates the movement of fluids within the dentin and pulp and why is fluid movement not stimulated by other tastes (or maybe it is, but it is not sufficient enough to cause the pain?).
The lightbulb went on when I read the first sentence: "Hypersensitive dentin is characterized by transient pain in response to evaporative, tactile, thermal, or chemo-osmotic stimulation of exposed dentin".
The "sweet" stimulus would be such a chemo-osmotic stimulation. Reflecting back on high school chemistry, I know that osmosis is the tendency of a fluid to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane. So perhaps the fluid movement that stimulates the nerves and causes pain is in response to the high concentration of sugar in the food that I was in the process of consuming that had leaked through the crack of my tooth and through the dentinal tubule to the pulp. As to why no salty foods? Maybe the amount of salt I eat isn't enough to initiate this fluid movement. I don't eat high concentrates of salt. Similarly for bitter or sour foods. And it isn't all sweet foods that causes this pain. it's only the sickeningly sweet foods (like really sweet icing) that cause it. If I tried eating something that had a high concentration of salt in it maybe I'd feel the same pain. Having an aversion to pain, it's not really an experiment I'm likely to conduct. But it seems like a reasonable conclusion.
Still, I'm hoping once again that the sis can step in here, and either validate my conclusion or shed some new light.:-)
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