For example, if a kid breathes through their mouth instead of their nose, it can narrow the upper jaw and make the face appear longer and more narrow. It can also cause dental issues like misaligned teeth (overbite or underbite). Thumb sucking, especially past the age of 3 or 4, can affect how the teeth come in, leading to a recessed upper jaw or a more open bite, which changes the structure of the face. Nail biting can lead to misaligned teeth, chipped teeth, or jaw tension, and it can even cause the masseter muscles (jaw muscles) to overdevelop, making the face appear squarer. Poor posture, like slouching or craning the neck forward, can mess with how the jaw grows and lead to things like a less defined jawline, muscle imbalances, or even a double chin. If a kid isn’t getting enough deep sleep, it can affect how the bones in the face grow, leading to things like a weak chin, flat midface, or poor overall facial structure.
