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Bruxism (Tooth Grinding)


Bruxism refers to the habit of grinding your teeth. While this may occur anytime of the day, sleep studies have shown that people grind more intensely and for longer periods of time while they sleep. In addition, we are learning that bruxism is often associated with sleep apnea (breathing stops periodically during sleep) and Gastroesophageal Reflux Disease or GERD (a condition where stomach acid leaks up into the mouth during sleep). Symptoms of GERD resemble those of heart burn or acid indigestion.



Wear

The enamel surface of teeth is convex (rounded) in all directions. As teeth wear, these rounded surfaces flatten out resulting in wear facets. When the enamel is worn through, the underlying layer of dentin becomes exposed. Dentin is much softer that enamel, so it wears faster becoming “scooped out”. As it continues to wear, the brittle enamel chips away leaving the tooth shorter with jagged edges. When acid is present in the mouth (as can occur during GERD), it softens the enamel and greatly accelerates wear and increases sensitivity.

 

Abfraction Lesions

When we grind the teeth, they flex. The enamel is very rigid and bonded strongly to the underlying dentin which is more flexible. As a result, the crown of the tooth does not flex much, in fact the highest stresses in the teeth occur where the enamel ends and the root begins. With time, tooth structure flakes away leaving a “V-shaped notch in the tooth where it enters the gums and bone.

We restore these lesions for 3 reasons:


  1. 1.They are often very sensitive

  2. 2.They are prone to cavities

  3. 3.The gums often become swollen around them

Cracking and Chipping of Teeth and Fillings

The stresses created during bruxism can cause the tooth to crack and chip especially if there is a filling in the tooth. Silver amalgam fillings are very stiff compared to tooth structure, so when the tooth flexes the filling moves independently and acts like an axe in a piece of wood. Cracks in teeth continue to grow until part of the tooth breaks away so it is best to remove them as early as possible.


                      Case 1

Note the dark yellow colour on the biting surface of the tooth. This is the colour of dentin indicating that all or most of the enamel has worn away in this area. Note that this is intact tooth that cracked and was only weakened by the loss of enamel in the area.


Case 2:




Occlusal Trauma

The greatly increased forces on the teeth that occur during grinding depress the tooth in its bony socket. This compresses the ligament at the tip of the root and can damage it. The body’s healing response to this damage is inflammation which leads to swelling. The nerve that supplies the tooth travels through this inflammation and becomes hypersensitive. The symptoms typically noticed include sensitivity to hot and/or cold as well as discomfort to biting or chewing.



Loosening of Teeth

The forces generated during bruxism include the vertical direction (straight down the root) and lateral (side to side from tongue to cheek). As a result, the teeth often move laterally when grinding occurs. This widens the bony sockets that hold the teeth and results in progressively increasing mobility of the teeth.



TMJ Problems

The temporomandibular joint (TMJ) or jaw joint is put under great stress during bruxism. As the muscles contract, they pull the jaw into the base of the skull where a small disc becomes squeezed and may slip out of position. This results in a clicking sound when you open or close your mouth or chew your food. This condition worsens if there are no posterior teeth to help distribute the forces during bruxism. In extreme cases, this joint develops arthritic changes which results in bone loss within the joint.

On these incisors, the dark yellow dentin wears faster than the enamel, leaving the brittle, glasslike enamel without support so it chips off with unaesthetic results.