Growth displacement of the maxilla in girls studied by the implant method.

The sutural growth displacement of the maxilla between the ages of 8 and 21 years was studied on 14 series of lateral cephalometric films of girls from the Björk implant sample (Björk 1968). The assessment of growth changes was based on the method of superimposition described by Björk and Skieller (1983) supplemented by a new computerized debugging procedure. A new method for angular measurement of the forward displacement of the maxilla and the mandible is described here. The average forward displacement of the maxilla in relation to the anterior cranial base was 6 degrees from 8.5 to 17.5 years. The average path of displacement was inclined about 45 degrees in relation to the nasion-sella line from 8.5 to 14.5 years, and then changes to almost horizontal. The mean distance between anterior and posterior implant points showed a continuous shortening, totalling 0.6 mm for the period 8.5 to 15.5 years, due to maxillary rotation in the transverse plane. The timing of growth differed between the horizontal and vertical components of the maxillary growth translation. Horizontal displacement peaked at 11 and terminated at 18 years, whereas vertical displacement peaked at 12 and terminated at 15 years of age.