as shown in the longitudinal section of fig4 taken through line 4 4 of fig6 one of the equilateral triangular faces 46 is disposed substantially perpendicular to cutting direction 48 and raked backwardly so that exposed side 50 is tilted approximately 75 u00b0 backward from the vertical the backward rake of pcd element 42 is chosen to maximize the shearing action of element 42 against the rock formation according to each application for which the rotary bit is designed the inclination illustrated in fig4 however has been chosen only for the purposes of example as shown in fig4 a leading edge 52 of element 42 is disposed and embedded within bit face 10 since there is no prepad as a practical matter little cutting action will occur after the teeth of a rotating bit have worn down to bit face 10 element 42 is similarly supported by a teardrop shaped trailing support 54 best shown in longitudinal section in fig4 and in plan view in fig6 as best shown in fig6 trailing support 54 is characterised by a triangular apical ridge 56 extending from and tapering from element 42 to a point 58 on bit face 10 in addition as best illustrated in fig5 width 60 of element 42 is narrower than width 62 of tooth 44 therefore matrix material 12 is provided on each side of element 42 providing a measure of lateral support as well as tangential support therefore as seen in fig6 the leading face of tooth 44 may also include flat matrix portions 64 on each side of element 52 leading to the top of apical ridge 56 in practice apical ridge 56 may not be sharply defined at or near the top of element 42 as illustrated in fig6 thus.