What kind of needle do they use if the dragon fangs didn't go through it?
Not sure how this is any different than normal clothing. Means in the right areas, you could pierce it with a needle as it just slides in between the threads that make up the fabric.
Even if the dragon fang was as sharp as a needle at its point, the threads still need to break or part to let the fang through. Sharpen a pencil down to a fine point and you can't even push it through a cotton shirt, because while the point can enter, the rest of the pencil is way too thick. Meanwhile, you can even push needles through cut-resistant microfiber.