Why do teeth crack?
Teeth, particularly the lower molars take a lot of force during function. However, teeth are well designed to absorb this force if they remain intact. It is quite rare for an intact tooth to crack.
Two factors make a cracked tooth more likely. Amalgam fillings in the middle of the tooth produce a point of weakness in the tooth. The force of the opposing tooth pushes the cusps [pointed bits of the tooth] outwards, and an area of stress concentration is produced at the base of the filling. This is illustrated in the following diagram.
The second factor is what dentists call “parafunction” this means clenching and grinding of the teeth. Parafunctional activity is outside of conscious control and the forces generated are much greater than normal chewing.
How do I know if I have a cracked tooth?
Sometimes a tooth breaks with little or no warning. Other times the tooth will become painful when biting. Most typically hard foods such as grainy bread will cause intermittent sharp pain. A cracked tooth may also be more sensitive to cold.
If the crack is more advanced then there may be pain with heat or a prolonged toothache.
How do we identify cracked teeth?
This can be quite difficulties the crack is rarely visible on the surface of the tooth and they do not show up on X rays.We will test for cold sensitivity and see if we can reproduce the pain on biting pressure using a specially designed instrument.
Often we will need to remove the existing filling to be able to visualise the fracture.
How do we treat a cracked tooth?
Treatment will depend on how extensive the crack is. If only one cusp is lost then a simple replacement filling may be all that is needed however if multiple cracks are present then the tooth may need to be protected with a ceramic crown.
In approximately 20% of instances the crack may have allowed bacteria to get into the inner part of the tooth [the pulp]. If this happens the tooth will continue to be painful and a root canal therapy is needed.
Occasionally the crack will run down onto the root surface below the level of the bone and the tooth may not be fixable . In this case the tooth will need to be extracted .
Can we prevent cracked teeth?
The best way to prevent cracked teeth is to avoid the fillings that weaken them in the first place. unfortunately this is not possible for most of us who had multiple amalgam fillings placed in our molars many years ago.
If tooth grinding is part of the problem then a bite plate that protects the teeth from damage will definitely help.
In most cases cracked teeth are an almost inevitavble legacy of our childhood dental disease. However if we identify and treat cracked teeth in a timely fashion we can limit the damage.