Night guards is mostly used in case of excessive teeth grinding or jaw clenching known as bruxism. It is an oral para-functional activity.
People who often grind their teeth do so at night. Teeth grinding can be treated by simply wearing a night guard while you sleep.

Bruxism may be caused by stress, sleeping problems, crooked teeth or missing tooth or malocclusion. Signs that shows you are grinding your teeth includes headaches, jaw pain particulary in the morning. You may also notice that your teeth are getting shorter or changing shape and fitting together differently.
Your sleep partner may let you know as well that you are making loud noises when you sleep. Any of these symptoms could indicate the need for a night guard.

If you think you may need a night guard, contact your dentist for a custom-made night guard mad e out of soft material that will fit your mouth.
The night guard slides over one row of your teeth and prevents you from grinding your teeth together. Night guards are relatively easy to get used to and can prevent serious dental problems down the road.