This crowdedness comes from shrinkage of the jaw, primarily the lower jaw, both in length and width. While this is only a matter of a few millimeters, but it is enough to crowd the front teeth. We can also eliminate wisdom teeth as the cause, because even people who have no wisdom teeth have crowded front teeth.. How much the jaw shrinks is individual, but for some patients the changes are sufficiently great for them to perceive that something is happening to their bite.