A preliminary report on lower arch crowding in the mature adult.

Changes in lower arch crowding were measured on models of 16 subjects between the ages of 18 and 50 years. Changes in position of various cephalometric points relative to the skull base were measured on 90-degree left lateral cephalograms. Some increase in lower arch crowding was found in 80 per cent of subjects. With one exception, all subjects showed changes in size and orientation of the jaws relative to the skull base varying in amount and direction. Possible causes of increased lower arch crowding in the mature adult are discussed.