How anterior overbite relates to extraction needs.  The amount of anterior overbite or openbite a patient has plays an important role in uncrowding of the dentition.  When we see a slightly open or shallow overbite malocclusion that displays crowding a red flag can go up.  Uncrowding of the teeth tends to lean the incisors somewhat labially and this will lead to more opening of the anterior overbite.  Even if the vertical elastics are used to deepen the bite, open bite tendencies may return after removal of the braces.  On the other hand, spaced dentitions will tend to deepen during orthodontics and space closure.  An easy way to visualize this is to think of a draw bridge and what happens as the two halves are leaned upward or brought back toward the water.