Night guard is an appliance you wear at night times to protect your teeth against force that is applied from the teeth on the other arch. Grinding or clenching habit is also called "bruxism" in a dental professional term. Night guard is recommended for someone who clenches or grind their teeth. There is also a day guard that is available for people who grinds their teeth during the day.
It is very important to wear a night guard if you have bruxism, because it can have various disastrous effects on your teeth. Teeth can crack under heavy pressure. Fillings can break causing leakage in the restorations causing more drilling for the dentist to restore the tooth. Bones can shrink or melt due to the pressure, thereby causing gums to recede showing ugly colors of the root when smiling.
You can find out if you are grinding your teeth by looking at your teeth in the mirror. If you can draw a straight line across your upper teeth from left to right, you are definitely a heavy grinder which needs immediate attention. A mild grinder will see some wear or flat surfaces of the teeth in different areas. Finally, if you experience frequent migraine or headache and soreness to the chewing muscles, you are more than likely suffering from bruxism.