A comparative study of craniofacial measurements between Ryukyuan and mainland Japanese females using lateral cephalometric images

Using lateral cephalometric images, we compared the skeletal and soft tissue configurations of Ryukyuan and mainland Japanese females. We collected lateral cephalometric images of 30 females each from Okinawa Island and mainland Japan. Sixty landmarks were plotted on each image. Then, based on the coordinates of the landmarks, 68 distances and 34 angles were calculated according to orthodontic and anthropometric methods. We confirmed that the Ryukyuans have a smaller height in the upper and midfacial region than the mainland Japanese. Moreover, our findings indicate that, compared with the mainland Japanese females, the Ryukyuan females clearly have the following features: (1) a shallower mandibular notch, (2) an anterior-inclined symphysis of mandible, and (3) a smaller depth from upper lip to incisors. We also found that an anterior-inclined mandibular corpus and incisors are associated with a smaller distance between the surfaces of the upper lip and teeth and with a more protruded lip shape