Ruling 215

If the body of an animal becomes impure with an intrinsic impurity like blood, or with something that has become impure, such as impure water, in the event that the impurity is removed, the animal’s body becomes pure. Similarly, the inner parts of a human body – like the inside of the mouth, nose, and ears – become impure by coming into contact with an external impurity, but by removing the impurity they become pure. As for internal impurity – such as blood that comes out from in between the teeth – this does not cause the inner parts of the body to become impure. Similarly, if an external object inside the body comes into contact with internal impurity, it does not make the object impure. Therefore, if dentures come into contact with blood that comes out from in between the teeth, it is not necessary to wash the dentures; but if the dentures come into contact with impure food, it is necessary to wash them.