As i said, possible, but still outside his mouth and nowhere near the amount of force required to break a mandible. Remember, no real damage to lips except a minor burn, but huge damage inside the mouth to the mandible but no damage to the upper incisors. Doesn’t make sense.
It actually makes perfect sense.
An RDA is basically a metal cup with small ventilation intake holes on the sides.
On the top is a big, gaping hole where the mouthpiece is.
If he took too many dry hits (The wicking material was too dry to vaporize anything) and kept hitting the activation button, and the titanium ignited, the force would go directly into his mouth. Like a shotgun shell.
Add the fact that his lips were wrapped around the drip tip at the time of it happening.
Therefore, his lips would be outside of the combustion area while his teeth would get the brunt of it.