I haven’t played alien isolation in years so I might misremember parts of that game, but I do recall that the alien could not be killed. As a player, that tells me every situation is winnable no matter what equipment I have. Compare that to dead space where inventory management comes into play. While playing dead space, I become concerned about my remaining health boosters or ammo, I begin to wonder if I have enough resources to make it to the next save point. Or what happens if I save now but don’t have enough resources to beat the next upcoming encounter? To me the risk of failure adds to the horror, as well as the immersion.

Most of the answers here mention the bone and ligaments holding the teeth in, which is correct, but it’s also worth noting that your other teeth prevent each other from falling out. More specifically, the teeth opposite on the top and bottom of your jaw. When someone has a tooth extracted, it’s common for the tooth opposite to do something called “super erupt.” Super eruption means the tooth essentially grows out of the bone because there is no longer an opposite force keeping it in place. In severe enough cases, when the bone and ligaments around a tooth are also compromised, teeth can spontaneously fall out. This isn’t necessarily rare, but for most people it isn’t a concern.