Figure 3. Stress distributions of the PDL and bone. (A) The contour graphics of the 1st principal (tensile) stress in the cervical area of the PDL, viewed lingually. The 4 models were: those of normal bone height with normal and widened PDL space, and those of reduced bone height with normal and widened PDL space. Each contour graphic was divided into 10 parts, with different colors according to the stress level, shown in the scale below the Figs. The red area represents the highest tensile stress, while the gray area indicates the stress below the reported tensile strength of the PDL (2.4 MPa). (B) The contour graphics of the 3rd principal (compressive) stress in the labial side of the cortical bone. The red area represents the highest compressive stress, as shown in the scale below the Figs. The enlarged grey-scale view of a contour graphic highlights the principal stress distributions, with directions generated at nodes on the labial cervical bone. The blue internal arrows represent compressive stresses, the black external arrows tensile stresses. The arrows were traced from the original data graphic and superimposed on the grey-scale graphic.