Night guards a generally a hard acrylic or softer plastic that is custom-formed to your mouth. You may wear a night guard if you clench and grind your teeth at night or if you have many crowns in your mouth that need to be protected.
Night guards serve two functions. First, they should help protect your teeth at night time when you can clench up to three times as hard as during when you are awake. Second, they should help relax your muscles during the night by engaging your muscle reflexes from your teeth.
Tooth protection is relatively straight forward and makes sense. Night guards cover either the upper or lower teeth and prevent the opposite side from wearing into the side that the night guard is protected. While many night guards are hard, the acrylic is not as hard a tooth meaning that the night guard will wear down instead of your teeth. A well used night guard may only last a few years, and I've seen some only last six months. However, replacing a night guard on a regular basis is still much cheaper and less painful than having a broken tooth which is why most people opt to replace it on a regular basis.
Now this one isn't as obvious to most people, but hard night guards can relax your jaw muscles. To prove it, try this experiment:
- Clench down on your back teeth as hard as you can. Relax after 10 seconds.
- Clench down on your front teeth as hard as you can. Relax after 10 seconds
Now you might have noticed that you can't clench down on your front teeth nearly as hard as on your back teeth. This is a reflex that helps prevent you from hurting your front teeth. A hard night guard helps engage this reflex when you are grinding at night time which helps relax your muscles.