1. Why do teeth get cracks?

Cracked Tooth Syndrome is a very common problem, usually affecting teeth that are heavily filled.
The decay and subsequent filling causes a weakening of the remaining tooth structure.
Like all materials, teeth are subject to stress and fatigue. After many bites on the tooth (stress cycles), a hairline fracture can develop, usually at the bottom corner of the cavity, which cannot be seen on the outside of the tooth. If you are under a lot of psychological stress, you may grind your teeth (usually at night).

2. Does grinding my teeth make it worse?

Yes, and grinding is a very common habit. Almost every person will at some time in their life grind their teeth – usually due to stress. Unknown to you, grinding at night causes a massive increase (200-300%) in the stress and strain on your premolars and molars, especially if you have worn down your canines and lost the protective “lift-off” effect they can give in a sideways grinding jaw movements. You may benefit, from either a night guard, or a permanent addition to your canines to protect the back teeth from cracking. You may also have susceptible tooth anatomy (genetic) or worn down fillings, where the “valleys” on top of the teeth are deep not shallow.
This puts a lot more sideways splitting forces on the tips of the tooth during chewing, which leads to cracking.
Even unfilled teeth can get cracks.

3. Why does it hurt to bite on?

As the tooth flexes microscopically, the nerve is stimulated.
There are tiny fluid filled tubes (“tubules”) which are situated in the dentine (the inner core of the tooth, below the enamel).
These tubules run down to the nerve and as the tooth flexes microscopically, the crack opens and closes, sucking and pumping on these tubules, causing fluid to push and pull on the sensitive nerve.

4. Why is it sensitive sometimes to hot and cold?

The nerve is aggravated by the crack and by the bacteria being pumped into it via the tubules. It becomes inflamed because of the toxins in the bacteria. A classic symptom of nerve inflammation is excessive sensitivity to hot and cold.

5. If I do nothing, what will eventually happen?

The crack continues to slowly progress (spread) like a crack in glass. Sometimes the crack goes off to the side and the fragment of tooth breaks off. The crack can also go deep to the root and at times right into the nerve. Teeth can often go for months in a stable, yet inflamed condition. Sometimes they seem to get better, only to suddenly get worse. It is hard to predict the course of the untreated tooth, but it is usually a slow downhill slide as the crack deepens. It is not a good idea to leave it, because a small crack can be treated effectively, but a bigger one can lead to root canal treatment or extraction if you are unlucky. The nerve can be attacked by the bacteria, leading to extreme sensitivity to hot and/or cold and a persistent ache in the tooth as it dies, usually of moderate to severe intensity. The infection in the nerve can then spread into the bone underneath, causing abscess. This pain is usually severe and not always effectively controlled by pain killers or antibiotics.

6. What is the best way to treat cracked tooth syndrome?

Unless the crack is immobilized the tooth is very likely to deteriorate. Although various methods have been employed in an attempt to stick the crack together, chewing forces are extremely powerful, and these “patch up” solutions are fairly unpredictable and ineffective. The only real solution is to bind the whole tooth together with a “cap” or “crown” (same thing), so that any chewing force moves the tooth as a whole, rather than splitting it apart.

7. What colour will this tooth be?

Most people prefer a natural appearance; and the new CEREC crowns are superior to the old porcelain fused to metal crowns and gold crowns as they have no metal, excellent strength and superior accuracy of fit, joining seamlessly to the underlying tooth. Because most cracked teeth have large black amalgam fillings, an improvement in appearance results, which is some compensation for the time and expense involved.

8. Are there any other advantages to a full crown?

The crown in bonded over the entire tooth – this seals all the micro-cracks and the variety of sources of bacterial leakage coming from the joints in the patchwork of fillings typically in these teeth.

9. Can you guarantee that the nerve will recover?

No! Despite the best treatment about 10% of cracked teeth have nerves that go on to die. The tooth can still move slightly within the bone and this slight movement can flex the rack from underneath despite the crown on top. Sometimes the existing bacterial damage is so substantial that the nerve goes on to die regardless of what we do.
Early treatment is therefore recommended to minimize the size of the crack and the extent of the bacterial invasion.

10. What will happen if the nerve does not recover?

The nerve will die and an abscess will probably develop. Therefore, the dead nerve remnants should be removed and the inside of the tooth cleaned and sealed. This process is call Root Canal Therapy. A small hole is made in the top of the crown (the crown cannot be removed without the risk of breaking the tooth or crown) and access obtained to the nerve for cleaning. Later on, the hole is filled in with a permanent, white plastic filling or porcelain inlay sealed to the tooth and the crown. It is a pity to have a hole in the crown, because it may weaken the crown slightly, but it is a quick and uncomplicated solution to the problem, with few long term problems.
Clinical judgment and many complex individual factors need to be taken into account to determine that the nerve will recover and will not require rct before crowning, and even despite the best efforts, some nerves go on to die after a crown is placed (sometimes years later).

11. Could the nerve in my tooth already be dead?

Yes. Cracks in teeth can develop slowly and this can allow a slow ingress of bacteria into the nerve. As a result, the nerve can die in a manner that’s less noticeable than usual. Nerves can become mildly sensitive to hot and cold, and then die, or they can die without any noticeable symptoms or pain. Many patients have teeth which, unknown to them, have dead nerves. Sometimes there are even dormant abscesses on these teeth, and the patient still does not know.

12. Is it safe to leave a tooth with a dead nerve?

Sometimes you can get away with it for a while, but unfortunately these teeth are ticking timebombs. The low grade infection that is usually in them can suddenly flare up and cause pain, swelling and pus. This usually happens when your immune system is down – often because of stress from an important life event.

A dental crisis is the last thing you need at this time. It is best to treat it as soon as possible to minimize the size of the bone destruction that occurs at the end of root, where the infection comes out of the root and into the jaw.

13. You said before that a crown was needed in order to avoid the nerve dying. If my nerve is dead, do I still need a crown?

Yes, and even more so. You need a crown now to stop the existing crack (which was severe enough to kill the nerve), spreading down the brittle root.
This is called a “vertical root fracture”. These nasty occurrences result in an untreatable problem, and extraction of the whole tooth is required. Crowns are needed on “dead” teeth ever more so than teeth with living nerves, because they become surprisingly brittle and very prone to these unfortunate types of cracks.

Regardless of how a nerve dies, crack or no crack, it is a standard practice to put a crown on a tooth that has had root canal treatment because of the risk of this crack developing. If there is already a crack, then it would be unwise not to put a crown on it. Therefore, if you have cracked tooth syndrome, be it in a tooth with a living nerve or a dead one you need the protective wrap around effect of a crown regardless.