Knock out any front teeth lately?
Over the many years I’ve been in practice, I’ve found few things as disheartening as seeing a young person whose front tooth or teeth have been knocked out by a sports injury. I didn’t really learn what I needed to know about sports injuries until about 10 years ago.  There’s an old phrase about the gaps we all have in our knowledge:  “You don’t know what you don’t know.”
I used to recommend boil-and-bite mouthguards to my patients because I didn’t know of any better answers.
Now, my best source of information on sports injuries is the team dentist for a minor league hockey team in California.  Here’s what he says about boil-and-bite mouthguards:

They don’t fit well, they’re uncomfortable (so people are less likely to wear them), and they don’t protect teeth.   This type of mouthguard has thin areas and thick areas, and the thin areas don’t provide enough material to protect the teeth in case of trauma.  Dr. Padilla has documented over two hundred cases in which people fractured or knocked out front teeth while they were wearing these cheap mouthguards.  For an athletic mouthguard to work, it has to have a completely uniform thickness, with no thin spots.  It also has to be made of a superior shock-absorbing material.  The Playsafe® mouthguards we recommend are made of solid EVA—that’s the premium shock-absorbing material used in the midsoles of top-quality athletic footwear.
These mouthguards cost a good deal more than the drugstore variety.  They also cost a lot less than the cost of repairing or replacing a broken or lost front tooth, and the peace of mind they provide is priceless.
We strongly recommend these custom athletic mouthguards for anyone involved in contact sports.

From the December 2011 “Chew On This:” Sports injuries to teeth It seems that more *people than ever before are participating in contact sports. Many of these activities cry out for the protection given by sports mouthguards.

“Boil and bite” mouthguards sold in drugstores and sporting good stores give the illusion that you’re protecting your precious smile teeth from injury. The reality is that these mouthguards have thin spots and thick spots, and are uncomfortable to wear. There are hundreds of documented cases in which people have lost or damaged front teeth despite wearing boil and bite mouthguards.

A far better solution is to do what professional athletes do—get a custom fabricated EVA mouthguard from your friendly local dentist (me!). EVA is the shock absorbent material used in the midsole of high-end sneakers. EVA mouthguards have uniform thickness, so their teeth protection is also uniform. To make this level of protection more affordable to our patients, we’re making two changes. First, we’ve substantially lowered our fee on adult sports mouthguards, to $287. Second, we’re introducing slightly thinner mouthguards designed for kids whose permanent teeth have not all come in yet. These mouthguards will be only $119. What it “boils” down to is that some mouthguards are useless, and we want to do everything possible to get you and your family wearing high-quality custom fit mouthguards. Comfortable, lightweight, and safe.