An occlusal  guard, also referred to as night guard, is meant to protect the teeth from clenching and grinding during sleep. It is worn every night or every time the person sleeps, so it is fabricated using a material that is not as thick but strong enough to serve its function. A sport mouth guard is an appliance that is prescribed to an athlete to protect his/her teeth from being damaged from a physical blow to the face or an accident. A sport mouthguard is usually made with a thicker material and given its purpose, it is made to extend to cover the entire jaw, even the gum tissue so that the entire mouth can be protected.

Both sports guards and occlusal guards are meant to protect teeth, but they protect your teeth in different ways.  An occlusal guard functions by protecting the teeth surfaces from being worn down from constant grinding and clenching.  A sport mouth guard is primarily worn to protect the teeth and mouth in case of sudden, hard impact.  As a result, while an occlusal guard may be made from durable hard acrylic plastic to withstand grinding over a long period of time, a sport mouthguard is usually made from a softer material that can absorb the force of sudden impact.  And while an occlusal guard only needs to cover the occlusal surface of your teeth, a sport mouth guard should cover your teeth including your gums.

The sport mouth guards that are commercially sold and made available in sports stores are different from the custom-made appliances offered by your dentist.  They’re not only uncomfortable to wear but also not as effective.  As for the occlusal guard, the best option is to get a custom fit guard that will effectively protect your teeth from grinding during the night rather than opting for a sports guard.

SOURCE: http://www.proteethguard.com/sport-mouth-guard-vs-dental-night-guard/