WHEN THE PUCK finally came to rest, it was almost entirely inside Craig MacDonald's mouth. It was Dec. 21, 2007, and with 1:51 left to play, the Tampa Bay Lightning winger, working in his own zone, stepped in front of an errant, elevated slap shot that instantly cleaved a grisly, bloody and impossibly wide swath of carnage through MacDonald's lips, gums and tongue before reducing nine of his teeth to dust. He spat out the 6 ounces of vulcanized frozen black rubber like it was a rotten MoonPie to reveal a fractured lower gum line and his half-cleaved tongue, hanging by a thread. Even in a sport synonymous with dental trauma, where the enduring image of hockey has long been the disturbing-but-endearing shot of Bobby Clarke's toothless grin reflected in the shiny silver of the Stanley Cup, MacDonald's injury was gruesome enough to earn an on-air attaboy from Don Cherry himself.

Team doctors reconnected the filleted parts of MacDonald's face with 75 sutures, then sent him home, where he sat on the couch until dawn, jolted awake by even the slightest puff of air passing over a mouthful of raw, exposed nerves.

"Worst night of my life," he says.

The next morning wasn't much better. After making his way, ever so gingerly, to the office of Gil Rivera, the Lightning's team dentist, MacDonald opened his mouth and was greeted by ... terrified silence. As a member of the gnarliest and most peculiar fraternity in sports, Rivera has seen it all during his 17 years practicing dentistry in the NHL: a Tooth Fairy teammate delivering goalie Ben Bishop's incisors to the bench for safekeeping; winger Ondrej Palat holding up half his bottom teeth with his tongue after getting lightsabered by an overeager rookie in practice; veterans, like Tomas Tatar, whom Rivera calls "Humpty Dumpties" because they have lost the same three front teeth on four separate occasions; marquee talent in need of work (and a bit of courage) hiding from him at the arena; and a notorious tough guy silently sweating through his clothes during an especially tough bicuspid extraction that Rivera compares to King Arthur pulling Excalibur out of the stone.

"It's just hockey, right?" says MacDonald, who retired in 2013 and, after studying at Harvard, is now an investment consultant in Nova Scotia. "Although I still don't recommend people blocking shots with their teeth."

Still, as MacDonald sat in Rivera's chair the next morning, the anatomy inside the player's mouth -- monstrously swollen gums, shredded tongue and Tic Tac nubs instead of teeth -- was unrecognizable. Rivera recoiled. He had no idea what he was looking at, or where to start. "His mouth was just obliterated," Rivera says. Out of instinct, he grabbed his air and water syringe and began washing away the dried brown blood and coagulate. Still unable to describe what slowly came into view next, Rivera puts his wrist against his mouth and wiggles his four fingers, like a walrus. "Four nerves just dangling there, flapping in the wind," he says. "I was like, 'OK, we need to do [six] root canals right now.' Oh, that poor guy."

Over the next four months, on off-days and between games, Rivera pieced MacDonald back together again during a dozen visits and more than 50 hours in the chair. The most hockey thing ever? MacDonald missed a grand total of one game. And the respect he earned from then-Lightning coach John Tortorella garnered him the most ice time of his 16-year pro career -- as well as a friend, and a dentist, for life.

NHL players like former Flyers winger Ian Laperriere often leave everything on the ice -- including their teeth. Matt Slocum/AP Photo

"That was the first time I truly understood just how tough and unique hockey players are," Rivera says. "And it was the first time I realized that I'd be bored sitting at a football game. If you're a dentist, this is definitely the gig you want."

IT MIGHT BE the gig Rivera wants now. That wasn't always the case. Rivera, who grew up in Puerto Rico, had never seen a hockey game until he attended the University of Connecticut. Three months after completing his residency, and new to Florida, he got a message from the senior partner at his dental practice telling him to report downtown to lend a hand with the Lightning. Rivera Googled "Tampa" and "Lightning" and, after briefly considering that the last thing lightning-strike victims needed was a good tooth cleaning, he realized his boss was talking about the city's NHL team.

Rivera began speed-reading as many gory case studies on extreme dental trauma as he could get his hands on. And what he quickly learned was that while tooth enamel might be the hardest biological substance on earth, it's no match for the sport of hockey. With pucks, sticks and fists flying in all directions at players who famously refuse all means of protection, tooth trauma and trips to the dentist -- most people's worst nightmare -- are as inherent to hockey as ice. Recently, after Florida's Troy Brouwer lost the same two front teeth that Calgary team dentist Kristin Yont had fixed for him when he played for the Flames, he sent her a picture of his wrecking-ball smile while sporting a T-shirt that said it all: 4 out of 5 Dentists Recommend Hockey.

"Dentistry is one of the defining characteristics of a hockey player," says gap-toothed Sharks defenseman Brent Burns. "Losing teeth is a badge of honor. And guys are so big and fast, and pucks are bouncing everywhere, it happens all the time in our sport."

The relentless assault on such a specific body part, especially one as socially and aesthetically important as teeth, has transformed NHL dentists into the unsung heroes of the sports world.