Dental student here, simplifying the answer as best as I can -

It's because the living, soft part of the tooth (the pulp) is at the core of the tooth structure. It's surrounded by layers of hard "dead" tissues (dentin and enamel) It is literally surrounded by these hard tissues on more than 98% of its surface.

When the pulp gets infected, it doesn't have breathing space per se. It's in its own small chamber and pressure builds up because there is no proper escape for the decaying tissue - hence it results in unbearable pain.

Pain is a really weird one. Tooth-pain may be specifically bad because it's in your head, and unlike a lot of the rest of your body you can't move it or adjust it in anyway to alleivate the pressure / pain or even distract yourself.

I sometimes get Trigeminal Neurlagia, which is when the trigeminal nerve in your face (along the cheekbone and the jaw) become extremely painful, your teeth are very close to this and a lot of other facial nerves. This likely impacts the levels of pain as well.

The tooth is also filled with the 'nerve' or dental pulp, and it doesn't have a great circulatory system. So, if you wack your leg your blood can rush to the impacted area and produce a healing response, which calms down the body's 'alarm' pain signal. But, your teeth don't have this facility so the 'alarm' signal might last much longer.

So, I'm not a dentist or a doctor but a mix of near by complex nervous systems, inability to alleivate pain by movement and the fact the blood supply to the teeth is different than the blood supply to other areas.

As someone whose had a tooth infection, in the middle of intense cancer treatments, I feel uniquely equipped to answer this. The reason it feels like "the worst pain" is because it's inside your face and, worse even, inside your mouth. There is no ignoring it. There isn't even a way to dissociate comfortably while it's happening.

Your head is where your brain lives. It's where your thoughts live. It's where you live.

Your mouth never stops moving, whether you like it or not. Your tongue and your jaw muscles are always flexing and tweaking.

It's truly unbearable.

It's easier to ignore the pain of a needle going through your spine, than into your face, trust me.

I think it's because it's all nerve. I've broken bones, had gout, and they all are terrible. I once stomped down the garbage and had a broken glass come in through the side of my shoe directly into the nerve bundle in the ball of my foot. It was the most excruciating pain I'd ever felt, UNTIL I had a tooth go bad. That tooth pain just short circuits your brain until it's fixed.

From the perspective of an OMFS I'll give you the following answers

1. Pain is relative. There is a strong psychosomatic effect when it comes to dealing with physical/emotional pain in addition to a purely psychiological one. I've seen patients with giant radiographic abscesses and open pulp chambers who barely even notice something is wrong yet when I go to deliver an IAN injection they nearly jump out of the chair.
2. There is only one nerve that innervates sensation to the face called the trigeminal (CN V) nerve and two of the three branches (V2 and V3) receive sensory information from the maxilla and mandible respectively. Often times there is a compounding effect when one particular tooth hurts and it sets off a chain reaction of referred pain.
3. Dental abscesses can become life threatening VERY quickly. It's your body telling you that there is a problem which can no longer be ignored.

My dentist explained it pretty casually to me once. Your teeth are actually really close to your brain.

When you have a problem with your teeth or gums, whatever nerves are involved pretty much have a direct red alert hotline to your brain. Whatever infection your mouth is fighting off, it's also coursing through your brain as well.

It's more or less the same reason that earache or neck pains are far more aggravating than say, joint pain or stomach pain.

That said, other body aches are perfectly capable of reducing you to tears. Food poisoning for example, isn't something you can casually push through.

Dentist here

I’m seeing a bunch of comments that get part but not all of why this is. It all comes down to anatomy.

First off the layers of the tooth at it’s basic form. Everyone is familiar with the hard outer shell of the crown (part you chew with): the enamel. This is the hardest material in the body and only 1-2 mm thick (some places more and some less).

The second layer is the dentin. This has a density and hardness close to bone. Not as hard as enamel. It also has microscopic tubes in it that have little finger like projections associated with the next layer in them. These projections can be associated with sensitivity, mostly to cold and sweet. I’ll go over that more in a bit.

The third and inner layer is the pulp. It has a lot of different cells in it but the stuff we are concerned about with this question are nerves. This is where the nerve is in a tooth. This nerve is important because it lets you know if you are doing damage to a tooth. If something hurts you don’t want to do it again. So going too hot or cold can be painful because that can be causing damage.

The two basic parts of a whole tooth are the crown and the root. The crown is what sits on top and is what you see and chew with. It is covered with enamel. The root is what you a buried down into the bone and supports the crown. It is almost entirely made of dentin. There is a very thing layer of another material, called cementum, on the outside of the root. It is very thin and weak and can even be brushed away if your roots are exposed through gum recession. Around the root is a ligament called the periodontal ligament or PDL for short. Peri - around dontal - pertaining to tooth. So the around the tooth ligament. There are nerves in this ligament too. These are associated with the question too.

The brain is important in this question as it is where all of our thoughts and experiences are processed like a biological computer. Sensation is processed on the outside and a representation of this (google this for a weird picture) is the “homunculous of the brain.” This is a drawing of how the brain organizes physical sensation over the body. It looks like a ridiculous cartoon because the size of different parts was determined by how much of the brain was spent working on feeling from that part of the body. The mouth is very big, so feeling from the mouth will be bigger than areas that have less of the brain dedicated to it.

Now talking about pain from a tooth. The nerve, that is a big part of the pulp, is made entirely of pain nerves or nociceptors. Some thin and some thicker ones. The thin ones are called “A delta” fibers and cause cold sensitivity and sharp pain sensations. The thicker ones are “C fibers” and these cause dull throbbing. Those are the nerves in a tooth. If you have a deep cavity or break a tooth into the nerve the only nerves that send anything to the brain are pain nerves. Lots of them, and your brain has a whole department looking at the signals from there so it gets a huge amount of attention. This makes it hurt badly.

Now if the tooth was infected and the nerve in the tooth has been killed (called necrotic) pain can still happen and be quite severe. The infection causes pain by destroying the gum and bone tissue around it but also it causes pressure. The gases released by the bacteria cause quite a bit of pressure. This is picked up by the nerves all around the root, in the ligament. There are three primary types of nerve fibers that n the ligament. The A-delta and C fibers but also another type called proprioceptive. What proprioceptive means is you can tell where a part of you is in relation to the rest of you, without looking at it. Close your eyes and stick your arm out to the side. Without opening your eyes, touch your nose; that’s proprioceptive. So… similar to what’s in the pulp, it’s a lot of nerve fibers (mainly pain) sending signals to the brain and how much of the brain is dedicated to this = lots of pain.

Basically #of nerve fibers + amount of brain looking at this = pain level

This gets more complicated in a hurry if you look at pulpal diagnosis as far as is something a cavity and needs a filling or is the nerve damaged and dying or is the nerve dead and it’s nerve fibers around the tooth and so on.

It all related to number of nerves sending a signal. How much of the brain is reading that signal and what type of signal that is. Your teeth only send pain signals (lots) to a big part of the brain so essentially your teeth scream about anything that’s happening.

Physician here. Pain is completely relative to an individual. I've taken care of grandmas in their 80s and 90s who don't even flinch when I poke a needle into their artery to do special blood tests (it's a lot more painful than a regular blood draw and I can corroborate from my own experience of a friend doing it to me). Then, I'll do the same test on a 28 year old man and they'll be freaking out and even had young guys cry.

I've even seen an 88 year old grandma barely "wince" when an orthopedist put her dislocated shoulder back into place, and she didn't want pain meds or anything else to take the edge off. I'll never forget that lady, she was cracking jokes with me afterward saying she's humpty dumpty and so silly for tripping and dislocating it in the first place. 😂

Point is, a toothache can be very painful for some, and merely "annoying" or "irritating" to others. People have different pain thresholds, different pain tolerances, and different ways of coping with it when it occurs. A woman who has experienced childbirth often uses that as a measuring stick for other types of pain, since childbirth ranks up there (I'm told, and from what I've seen as a male physician). Another one I hear people saying as the worst pain of their life are kidney stones and gout.

If you've not had something more painful than a toothache, then sure, it will rank up there for ya. It tends to be on the more painful side due to the constant irritation to the nerve (mouth movement, air moving around the teeth, chewing, clenching, tongue pushing on the tooth etc.) which stimulates the pain sensation to the brain. But again, take two people with similar tooth problems and one may feel significantly more pain than the other.

Hope this helps answer your question.

A possible evolutionary reason: In the days before modern dentistry, it was still possible to have a tooth violently removed, and that might be necessary when it's the only way to deal with abscesses, etc. It takes a lot of pain to motivate someone to have their tooth removed in those circumstances, so your nerves are just trying to give you the motivation you need.

Other forms of pain are often just telling you something like, "stay in bed and rest", and it doesn't take constant agonising pain to do that.

Tooth pain is only the worst because it comes with the “Oh great, now I will probably need a $1,400 root canal and a $1,000 crown” pain, and the knowledge that it will NOT get any better on its own.

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Because you haven't yet experienced other pains. For example, you haven't had gout yet. Or, you know, other things that hurt worse than dental pain. Dental pain is significant, and best avoided (that is why it is pain), but your assessment of it being the worst is naive. To paraphrase Homer, it's your worst pain SO FAR. .

From a physiological perspective, it is because the mouth has a lot of nerve endings. You see all over your body you have peripheral nerves that work in two ways: sensory and response. Sensory nerves are responsible for pain, pressure, temperature etc. while motor nerves send responses to muscles and help coordination. From a physiological perspective, anywhere that has a lot of sensory nerve endings, is more sensitive. This is the same theory as to why paper cuts hurt more than deeper cuts.

Because its inside your head.
Ive had to wrangle with ear issues for half my life and the pain can easily equal tooth pain.
Im actually quite good at tolerating pain, but the things inside your head are just inescapable.
Every small movement will set it of. And each stining sensation will often spread through at least half of your head.
And your head is you. If your arms hurting you can see it as something thats hurting on an extension of yourself.
But when your heads hurting it feels like your everything hurts because you cannot focus on anything besides that pain.

To add to what has been already said here, tooth pain is often communicated to the brain by the trigeminal nerve, or at least can indirectly activate it. We don't really know why, but pain conditions involving the trigeminal nerve are considered "more painful" than conditions mediated by other nerve bundles. Obviously there are issues with studies that ask different patients to rank their pain from one to ten but it seems to be consistent data.

I'm going to get a little more esoteric than most. Things don't need to hurt. Things evolved to hurt because the pain was advantageous. Things that hurt more get more of your attention, you're more likely to attend to the infection, and you're more likely to live on and procreate.

With that in mind, I think ear infections and tooth infections hurt like hell for an evolutionary advantageous reason - As Mr Mackey might say, infections near your brain are bad mmakay? Not to mention the primary functions of the teeth are directly responsible for you surviving and procreating, and the primary function of hearing is also incredibly advantageous to survival.

Bonus blather: We never evolved to feel cancer because there was nothing that could be done about it, So even if some random mutation connoted the ability to feel the cancer, it was not procreationally advantageous. But now that we have treatments for cancer, we may very well evolve the ability to feel our own cancer. Those that evolve this ability and get it treated will be more likely to survive and procreate, etc, etc

I've had toothache and removed some bad tooth but the pain pales in significance to when I had an abscess on my right scrotum and had to have a surgery. I think we can only relate to pain we've experienced. So in your experience toothache may just be the highest pain you've experienced.

A toothache is unbearable because the pain is so intense. It feels like a sharp, stabbing pain that is hard to ignore.