Application of analysis of crowding and spacing of the teeth.

Spacing or crowding of the teeth is measured and analyzed to assist in decisions regarding the maintenance of teeth in their existing positions or their movement to improved positions. Numerical guides always should incorporate a gray zone in which decisions cannot be made without additional information. In the stage of mixed dentition, estimates of the size of unerupted teeth are more accurate than estimates of future spacing or crowding because the perimeter of the arch does not diminish the same amount in all cases. Instead, it appears to be related to the amount of crowding in the mixed dentition. Determination of the amount of crowding or spacing must always be accompanied by consideration of molar, canine, and incisor relationships. In addition, the effect of the dentition on lip posture should also be evaluated.