It's stuck. A cavity, called sinus, is formed between the inner and outer bone plates of the skull. Sinus can increase the volume of the head to attach teeth without increasing its weight. After the pig's head bone is cooked, it is cut off. It is normal that the pig's head bone sometimes sticks a little bit of teeth. Pig bones have high nutritional value. But pig's head bone can't be eaten in large quantities, because there is still a lot of fat on it, and eating too much may lead to an increase in cholesterol.