A cracked tooth usually hurts because biting flexes the two halves of the crack apart, and releasing lets them snap back onto the nerve inside. That is why the pain is often sharper on release than on pressing down, why it is brief, and why it can be hard to point to the tooth responsible. A crack is a structural problem, and it does not heal.
If a tooth is catching you when you bite, we can find out which one and why.
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Why does a cracked tooth hurt on biting?
Inside every tooth is a layer called dentine, made up of millions of microscopic fluid-filled tubes that run inward to the nerve. Movement of that fluid is what the nerve interprets as pain.
A crack splits the tooth into two segments that are still held together, but only just. Bite down and the segments separate very slightly. Fluid shifts. Release, and they close again, and the fluid shifts back sharply.
That closing movement is the one people notice. A sharp jolt as you let go of a nut, a piece of bread, or a chip. It lasts a second, and then it is gone.
Why it feels like the wrong tooth
Nerves in the back of the mouth converge before reaching the brain, so pain from an upper molar can be experienced in the lower jaw and vice versa. Many people are certain which tooth is at fault and are wrong. This is normal, and it is not something to feel foolish about — identifying the tooth is a diagnostic job, not a patient one.
What are the other signs?
- Sharp pain on releasing a bite, particularly on hard or fibrous food
- Pain that comes and goes rather than being constant
- Sensitivity to cold, and sometimes to sweet things
- Discomfort concentrated on one side, without an obvious cavity
- A tooth that feels fine most of the day and then catches unexpectedly
- A rough edge you can feel with your tongue, if a piece has already broken away
Notably absent from that list is anything visible. Most cracks cannot be seen by the person who has one, and many cannot be seen on an X-ray either, because a crack running front-to-back is invisible from the angle an X-ray is taken.
How does a crack happen?
Rarely from one dramatic event. Far more often it is accumulated load on a tooth that was already weakened.
Common contributors include grinding or clenching, particularly at night; large old fillings that leave thin walls of remaining tooth; a heavily filled tooth being asked to do the chewing work of an intact one; biting something unexpectedly hard, such as a stone in olives or an unpopped popcorn kernel; and the ordinary effect of decades of chewing on a tooth that has been restored more than once.
Root canal treated teeth are also more brittle, which is one of the reasons a crown is usually recommended afterwards.
How is a cracked tooth diagnosed?
By elimination and by provocation, rather than by simply looking.
A clinician will typically ask you to bite on a small plastic wedge placed on one cusp at a time. Reproducing the pain on a specific cusp identifies both the tooth and often the direction of the crack. Transillumination — shining a bright light through the tooth — can make a crack visible as a dark line where the light stops. Removing an existing filling sometimes reveals the crack running across the floor of the cavity. X-rays are taken to assess the surrounding bone and rule out other causes, not because they show the crack itself.
Testing how the nerve responds to cold also matters, because it tells you whether the pulp is still healthy or already inflamed. That distinction changes the treatment.
Not sure whether it is a crack, a filling, or something else entirely? An assessment settles it.
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What happens next?
Treatment depends entirely on how deep the crack runs, and this is why no honest answer can be given over the phone.
A crack confined to enamel
Hairline lines in enamel, sometimes called craze lines, are extremely common and usually cause no symptoms at all. They are monitored rather than treated.
A crack into dentine, with a healthy nerve
The aim is to stop the segments flexing. That usually means covering the tooth so the biting force is held together rather than wedged apart — commonly a crown, at $1,500 to $1,800 at Berala Dental. In some cases a bonded restoration is appropriate first. Symptoms often settle once the movement stops.
A crack that has reached the pulp
Where the nerve is already inflamed or has died, root canal treatment is generally needed before the tooth is covered. Root canal treatment is $1,600 to $2,200, typically followed by a crown.
A crack that extends below the bone
A tooth split vertically down into the root cannot reliably be saved, and extraction becomes the realistic option. A simple extraction is $350 to $550 and a surgical extraction $650 to $850. Replacement is then a separate conversation — see implants, bridges and dentures compared.
All of these figures assume no health fund contribution. Your fund may pay some, most, or occasionally all of an item; we can run a quote against your specific policy, and a written quote is always provided before treatment starts.
Does a crack always need treating straight away?
Not always, but delay has a cost that other dental problems do not share. A crack propagates. Every bite works it slightly deeper, and the depth is what determines whether the tooth needs a crown, a root canal, or an extraction. A tooth that could have been crowned in June can be an extraction by December.
Until you are seen, chewing on the other side is the single most useful thing you can do.
When it is more than a crack
Pain that becomes constant, throbbing, wakes you at night, or comes with swelling suggests the nerve is infected rather than simply irritated. That is a different situation and should be looked at promptly — see the warning signs of a dental abscess. Facial swelling with fever, difficulty swallowing or any difficulty breathing means a hospital emergency department, not a dental appointment.
Quick answers
Why does my tooth hurt only when I let go of a bite?
Because the segments of a cracked tooth separate under pressure and snap back on release, and that closing movement disturbs fluid inside the tooth that the nerve registers as a sharp jolt. It is one of the more characteristic signs of a crack.
Can a cracked tooth heal itself?
No. Enamel and dentine do not regenerate, so a crack does not close over. It stays, and repeated biting tends to extend it. Treatment is about stabilising the tooth so the crack stops moving.
Why can't the crack be seen on my X-ray?
X-rays capture a tooth from one direction, and most cracks run in a plane that direction cannot show. X-rays are still taken, but to assess bone and rule out other causes rather than to find the crack.
Does a cracked tooth always need a crown?
Not always. Shallow cracks in enamel often need nothing but monitoring. Cracks into dentine usually need the tooth held together, which a crown does well. What is appropriate depends on depth, position and whether the nerve is still healthy.
Getting it looked at
Because depth determines treatment, and depth increases with time, a cracked tooth is one of the more worthwhile things to have assessed early. No question is a silly one.
Berala Dental has looked after Berala families since 2002.
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You can also read about emergency dental care, cracked tooth syndrome, night grinding and night guards, or how our fees work. General health advice is also available from Healthdirect Australia.
Written and reviewed by Humzah Aly, Oral Health Therapist. This article is general information only and is not a substitute for personalised dental advice. Please see a dental practitioner to discuss what is right for you.
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