Also known as sports guard is a must for those play any sort of a contact sport. Mouth guard is made of a special flexible and strong plastic which, when worn, covers upper teeth. This will protect the teeth from any trauma from outside and also from smashing upper and lower teeth together.
It is always the best to get a professional made mouth guard as it will be custom made to your mouth and teeth and provide maximum protection. Some over the counter mouth guards may not fit on your teeth as they should and though won’t provide 100% protection.
Usually depending on the age and type of sport a mouth guard can be made in 3 different thicknesses. The thicker it is, the higher protection you will get.
Here is some pictures about mouth guards.