What causes tooth sensitivity?

Tooth sensitivity can be caused by a number of things, including:
  • tooth decay or cavities
  • grinding or clenching your teeth
  • abrasive toothpaste or whitening products
  • aggressive tooth brushing
Some people have tooth sensitivity in the absence of all these issues however. It is not a well-understood condition.
Teeth are sensitive if the nerve inside is irritated. This happens for a variety of reasons, but they all come down to exposure of the part of the tooth beneath the enamel layer, exposure of the nerve itself or trauma to the tooth and nerve.

Decay obviously eats through the enamel and can cause teeth to become sensitive. Sometimes after being filled or crowned, teeth will become more sensitive than they were or even become sensitive when they weren't. This is because the new filling or crown places an increased pressure on the nerve inside the tooth.

A fracture in the tooth structure can expose the deeper parts of the tooth and/or root of the tooth and create sensitivity to cold and bite pressure.

Wear on the enamel can expose the underlying dentin layer creating sensitivity. Since the enamel does not extend to the root portion of teeth, gum and bone recession can also expose parts of the teeth with no enamel protection, making them sensitive.

It is important to get an accurate diagnosis of the cause for the sensitivity in order to ensure the proper treatment for the tooth in question. It is probably important to note here that it is not always easy to tell which tooth is causing the sensitivity or even if it is a tooth related cause. Referred pain is a real phenomenon and can mislead a person to think pain is coming from a different area than the actual source of the pain. With upper teeth, there is also the proximity of the maxillary sinuses which, if inflamed, can mimic tooth pain in the upper molars.
Rita Medwid

Some tooth sensitivity is caused from clenching, grinding or bruxism. Excessive torqueing on the teeth can cause wear facets, hairline fractures, weaken the root structure, and inflame the ligament (the sac that holds the tooth). A night guard or custom splint will help. Avoid chewing on ice cubes, and hard candies. Do not use your teeth to open anything! Other types of tooth sensitivities can be helped with fluoride treatments, toothpastes or creams. Talk to your dentist for the exact cause of your sensitive teeth. 

Teeth Sensitivity! Ouch

If you have sensitive teeth, usually too hot, cold or sweets, there could be a few reasons for this:
  1. If you have generalized sensitivity, usually where the teeth and gums meet: Make sure you are using a soft bristled tooth brush and are not brushing too hard. If you have been doing this for a while, you may worn away the top layer of your teeth-the enamel. This is called “Abrasion”. In that case, change your brushing habits and use a sensitivity toothpaste such as Sensodyne to close up the tooth “pores” and decrease your sensitivity.
  2. If you have a few teeth which are sensitive at the gum/tooth margin and there is a little cave like void that is forming there: You have lost some enamel in that area. This could be due again either to hard tooth brushing or something called “abfraction”. Abfraction happens when the biting forces which are stronger on that tooth than the others. This puts pressure on the gum/tooth margin, or foundation of the tooth and cause that area to wear away.
  3. See your dentist in this situation to evaluate the area and do some adjustments on your teeth. They can also place a filling in the area to cover up the void. Over the counter gels can help reduce sensitivity as well.
  4. Gum recession may also cause sensitivity: This exposes the root surface of the teeth which are usually covered by bone and gums. You should see your dentist to learn about how you can prevent further problems, and control gum/bone disease (Periodontal disease).
  5. You just got white fillings and the teeth are sensitive: This is usually normal for teeth with white fillings that were recently placed. Especially if the fillings are deep, this sensitivity can last a few days up to a few weeks. If you eat something cold and feel a quick pain, but it goes away as soon as the cold is removed, don’t worry about it! Just give it time and switch to an anti-sensitivity toothpaste in the meantime. If your pain is extremely sharp and lasts a lot longer after you stop drinking something cold, you should check with your dentist. Sometimes if the bite is off on the filling you can have some biting and cold sensitivity or it may be a bigger problem.
  6. Sweet sensitive:Most of the time, this means you have a cavity or a void or leak in your existing filling. You should go see your dentist for a checkup.
It is always a good idea to see you dentist while problems are still minor!

There is not one answer to this question. There are different reasons why a tooth gets sensitive. It could be something as simple as some gum recession, and exposed areas of root of the tooth which is usually very sensitive to temperature. On the other hand it could be as complicated as some people that have allergy and get sinus inflammation and as a result of that some of their upper teeth (usually back molars) gets sensitive to chewing or temperature. The best way to find out the reason is to see a Dentist and have an exam and possible x-ray done.

Tooth sensitivity may be the result of several different factors.
  1. Bacteria eating a hole in the outer layer of the tooth (the enamel- which does not have nerve endings) exposes the inside of the tooth (dentin- which does have nerve endings.
  2. Receding gums and bone. The result of gum disease, the exposed root of the tooth has exposed nerve endings.
  3. Trauma -- biting down on something hard unexpectedly can "bruise" the nerve and cause pain.
  4. A cracked tooth (or filling) allows food and bacteria to reach the inside (dentin) of the tooth which has nerves that transmit the pain.
  5. Nerve damage -- can be the result of bacteria eating through the outer layer of the tooth (enamel) the inner layer of the tooth (dentin) to the main nerve (pulp).
Think of a mild skin abrasion on your arm or face. While very shallow, it is often very sensitive to touch. We think of teeth as being hard and solid, however they are made up of millions of microscopic rods and tubes. When those rods or tubes are abraded or exposed, air gets inside and the result is anything from mild to severe sensitivity. Scratching the site with a fingernail or toothbrush can also be just as sensitive.
There are many causes for tooth sensitivity. The most common complaint we here from our patients is sensitivity to cold liquids (or foods). The next most common complaint is sensitivity to hot liquids (or foods) and acidic liquids (or foods). 

Some causes of tooth sensitivity are:
  • Teeth with deep and/or multiple fillings
  • Teeth with crowns
  • Teeth with gum line defects (called abfraction lesions or wedge defects) where there has been loss of enamel at the side of the tooth next to the gum line
  • Receded gums -- Loss of gum tissue that exposes the roots of teeth. The roots of teeth do not have a protective enamel layer and are more susceptible to decay and tooth sensitivity
  • Worn biting surfaces -- Loss of enamel (from clenching or night grinding) on the biting surface exposes the second layer of tooth  (dentin) which is directly connected to the nerve of the tooth
  • Broken teeth exposing the second layer of tooth (dentin)
  • Faulty or broken fillings -- (open margins) where the filling has separated from the tooth
  • Missing fillings exposing the second layer of the tooth (dentin)
  • Stress fractures -- Miniature cracks on or within the enamel layer or the inner layer (dentin layer) that may or may not be evident to the naked eye
If you experience sensitivity, discomfort, an achy feeling brought on by hot, cold, biting, acidic foods or spontaneously (without any stimulus) for longer than 2 or 3 days running you should see your dentist.

If you experience sharp pain for any reason, you should contact your dentist as soon as possible.
Jonathan B. Levine, DMD
Just about everyone experiences some type of tooth sensitivity at one time or another. I'd venture to guess that as many as one in two people have some kind of sensitivity issue with their teeth. Probably more. It can be caused by a number of factors.
  • Gum recession or decay, both of which can lead to periodontal disease. And teeth are mighty sensitive by that point.
  • Physical forces, like clenching and grinding, or over-aggressive toothbrush abrasion, either from your own force or from a brush with bristles that are too hard. Not only can tooth sensitivity be quite painful, it's almost always a warning signal of some kind of problem beginning or growing that could potentially lead to some pretty serious conditions.
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Cavities and fractured teeth can cause sensitive teeth. But if your dentist has ruled these problems out, then worn tooth enamel, a cracked tooth or an exposed tooth root may be the cause.

The dentin contains microscopic tubules (small hollow tubes or canals). When the dentin loses its protective covering, the tubules allow heat and cold or acidic or sticky foods to stimulate the nerves and cells inside the tooth. This causes hypersensitivity and occasional discomfort. Fortunately, the irritation does not cause permanent damage to the pulp. Dentin may be exposed when gums recede. The result can be hypersensitivity near the gum line.

Proper oral hygiene is the key to preventing gums from receding and causing sensitive-tooth pain. If you brush your teeth incorrectly or even over-brush, gum problems can result. Ask your dentist if you have any questions about your daily oral hygiene routine.
As others have written, it can be from a variety of sources. One source that I did not see mention was referred pain from chronic muscle fatigue. Poor head and neck posture force the muscles to work harder, causing fatigue. With fatigue, there may be compression of the nerves that run through the area. There is also less blood flow, for it is the normal muscle movements that help move the blood to all areas of the body bringing oxygen and other needed nutrients in and removing wastes.

Fatigued muscles also do not allow the jaws to function properly, resulting in clenching or grinding habits due to the poor blood oxygen levels. Janet Travel wrote a book many years ago and the subject of referred pain and trigger points to relieve them is covered. 

This answer may seem a bit deep, but it tries to explain the source of the issue verses what type of bandaid to place when a cavity and abscess is ruled out.
Dentinal sensitivity describes the exposure of the dentin; the middle layer of the tooth that is usually covered by enamel. Dentin may be exposed by acids in food and other things eroding the enamel, causing the dentin to show. The more frequent reason is that the dentin on the roots of the teeth become exposed with increasing age. Within the dentin are tubules that carry nerves. These nerves are branches from the nerve in the pulp at the very center of the tooth. So when dentin is exposed, the nerve branches are stimulated.
Pulpal sensitivity occurs at the center of the tooth in the pulp, where vessels and nerves supply the tooth with nourishment and sensation. Pulpal sensitivity can be caused by infection, fillings, cracks in the crown of the tooth, or pressure from grinding.

Initially some amalgam fillings may make your tooth sensitive to cold, but this may fade in time.
There are many causes of tooth sensitivity. The obvious causes are a cavity or a broken tooth. Teeth can also be sensitive from receding gums, bruxing or grinding the teeth, abraded areas of the enamel or root, and wear of the enamel. Enamel helps insulate the teeth. See your dentist if you have sensitive teeth. Once the cause is identified, the sensitivity can be treated. 

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.