In theory it's not a serious issue. The tooth of a table saw blade travels at a linear speed around 146 feet/second, so if a tooth suddenly came loose you'd be faced with a tiny piece of metal travelling just under 100 mph. In reality the most likely result is it breaks and lodges in the wood when entering the kerf, or exits the kerf and travels straight down. [FWIW the teeth of a 7.25 circular saw blade would seem to be more of danger since they're similar size and run at much higher rpm.]
While a hundred mile an hour tooth sounds bad, it's not a huge amount of kinetic energy. It's much less than a baseball, probably more than a pellet gun. (A smaller mass travelling at 750 ft/s.) Certainly enough to merit eye protection, but highly unlikely to kill or seriously injure.
A much larger concern would be some sort of catastrophic blade failure flinging both lumber and large pieces of metal around. Large kicked back pieces have quite a bit more kinetic energy than a tooth. A prudent precaution is to let the saw spin freely for a bit prior to cutting. Grinders, which use resin blades typically suggest allowing the blade to run for 15s away from your face to be sure the glue isn't failing before you start grinding.
The real danger with a table saw is that accidents happen quickly in close proximity. That's compounded by the fact that the saw typically has enough power to accelerate anything on it to 100mph. While a tooth may present a limited danger getting hit by a 2x6 at 100 mph is an entirely different ball of wax. (Big leaguers shrug off baseballs, but don't want to be hit by a car travelling the same speed!)