are not normal, healthy actions of the jaws. In some adults and children,
clenching and grinding may occur during the day or at night. They typically have no conscious control over this
excessive clenching and grinding, particularly when it occurs during sleep.
The Function of the Jaws
Three muscle groups are associated with bruxism, as shown in the figure.
The temporalis and masseter muscles bring the jaws together. The lateral pterygoid muscles move the jaw from side to side.
The strength of jaw clenching determines the force of tooth grinding. Grinding does not occur if the person clenches,
or if the mouth is open. Slight relaxation of the clenched jaw allows grinding movements across the teeth as the jaw is
moved slightly forward and slightly to the side.
The Causes of Bruxism
The causes of bruxism are still being studied.A combination of physical and psychological factors are believed to contribute to bruxism:
1 .physical stress such as illness, nutritional deficiencies or dehydration, particularly in children
2.psychological stress, anxiety and tension in adults and children
3.studies have shown that night bruxism is a sleep disorder
4.other abnormal anatomy of the teeth or jaws (including 'high spots' on fillings) that
can cause an improper occlusion (also called 'bite') and lead to bruxism behaviour.