When the tooth nerve dies, all of the contents (nerves & blood vessels) within the pulp chamber and canals will begin to decompose. The decomposition may lead to an infection but ultimately the tooth will begin to slowly discolor over time.
Consequences of tooth nerve death
There are consequences when your tooth nerve dies and they are all either unpleasant or undesirable to say the least.
Results of dead tooth nerve:
Pain. Tooth pain may occur now or at some point in the future.
Tooth turning grey. It'll slowly start to noticeably discolor over time.
Periapical abscess. Can potentially develop an abscess from the dead nerve.
Loss of sensation. Dead nerves can't sense any stimuli.
It's not unusual for a dying nerve to cause an unbearable toothache while it is on its way to the afterlife. That is your body's way of letting you know that your tooth needs help. Although it isn't exactly the farewell present that you were hoping for because the pain can be bad enough to keep you awake at night.
Surprisingly, there are some situations where it doesn't hurt at all if the tooth pulp dies. In fact, it can be painless enough that the patient themself doesn't even realize that it has even died. Oftentimes, they don't find out about it until many years later when their dentist points out that the tooth is more grey or yellow than their adjacent teeth.
Toothache in future
Even if you're not experiencing any pain at the moment, it doesn't mean that a toothache in the future isn't possible. The dead tooth could always develop some sort of infection later on and cause you pain.
The potential for a future toothache is a risk that you would need to take if you decide to not treat it. There is no way to predict when it would start causing you pain.
A tell-tale sign of a dead tooth is discoloration. Below is an image of what the discoloration can look like on a front tooth.
The process is slow but over time the tooth will begin to look darker than the adjacent teeth. It'll often be yellower or grey looking and it'll only keep getting worse. It doesn't stop at a certain level of discoloration so even if the condition doesn't hurt you, it does become a cosmetic problem.
Potential tooth abscess
If you have an unhealthy nerve inside of your tooth, that would make it a potential source for an infection. You may get lucky and not get an abscess but that doesn't preclude it from getting infected in the future. This is a risk that you must bear in mind.
The image above shows what a potential tooth abscess can look like. It's appearance is often that of a pimple on the gums. If it pops you'll see white pus ooze out of it.
Loss of nerve sensations
A vital tooth with a functioning nerve can sense all of the different types of stimuli (hot, cold, sweet, sour, acidic). If the pulp stops functioning, you will lose all sensation for the tooth. It would no longer be able to experience the wonders of the world, namely the food that you eat.
Importance of treatment
There is a plethora of reasons to get the dying tooth nerve treated promptly.
Pain relief. If you're having a severe toothache, getting treatment will alleviate it.
Prevent infection. Even if it's not hurting you, it can always get infected in the future and then starting hurting you.
Good holistic practice. Does it seem healthy to you to keep something that is dying or dead in your body? Think of what happens in the case of gangrene when tissues necrose. Do you really want to maintain a dead tissue in your tooth pulp?
Dead tooth treatment
Treatment for this condition is two fold which shows you the intricacy of it.
Treating the nerve of the tooth.
Addressing the cosmetics of its aftermath.
The nerve needs to be treated directly and cavity fillings will not work because those don't treat the nerve at all.
Root canal. The most conservative way to treat an unhealthy nerve is to remove it from the tooth via a root canal procedure. As involved as it may sound, it is the still the least aggressive form of treatment.
Tooth extraction. The only other way to treat this condition is to remove the entire tooth which includes the nerve from the tooth via an extraction. Due to tooth removal being the only other option is the reason that we consider a root canal relatively conservative.
An often forgotten side effect is that the tooth starts changing colors when the nerve completely dies. This can present itself as an unsightly cosmetic outcome.The tooth is still functional but it just doesn't look very pleasant.
Dental crown. The tooth discoloration cannot be corrected with a root canal, you will need a crown to mask the color. Your dentist will prepare the tooth by shaving it down and then place a ceramic tooth over it.
External whitening. If the discoloration is very mild, you may be able to even out the tooth with traditional whitening. You may try the at home products or professional whitening with your dentist.
Internal whitening. Severe discoloration will require internal bleaching, which is when the whitening gel gets placed inside of the tooth. That is opposed to external whitening which places the gel on the outside of the tooth. Of course in order for internal whitening to work, the tooth needs to have had a root canal. Otherwise it would be extremely painful.
A lot of things can happen to a dying tooth with the most notable one being severe pain. However you can get lucky sometimes and it turns out to be painless. Nonetheless, you should still get it treated because it can always get infected in and result in excruciating pain.