If you’ve been following all the excitement of the Rugby World Cup in Japan, you may have noticed something odd in the mouths of players.

The plastic mouthguards in custom team colours lend a rather fearsome appearance to their wearers.

However, their purpose is much more benign.

Without them, players might find themselves quickly heading off to one of Tokyo’s many dentists for a spot of cosmetic work.

It’s more than likely that the mouthguards on show in Japan aren’t the common-or-garden variety purchased in sports shops but custom-made appliances fitted by a qualified dentist.

While ordinary sports guards offer reasonable protection, only custom-made appliances have what it takes to stand up to scrums, heavy tackles and the other physical rigours of the gentleman’s game.

Where ordinary mouthguards are a one-size-fits-all solution most often purchased off-the-peg, the custom variety is produced using a dental impression like those used to create dentures. This gives a super-accurate, non-slip fit, along with enhanced protection.

Rugby players aren’t the only sportsmen (and women) to put their trust in custom mouthguards.

You will probably have spotted them being worn in boxing rings, mixed martial arts cages and other sporting arenas where participants go head-to-head or fist-to-fist.

For sportspeople engaged in these most brutal of activities, only the best protection will do.