Click on image to view larger version.
Figure 1. Schematic diagram of crack geometry for cyclic contact loading with a tungsten carbide (WC) spherical indenter on porcelain-veneered layered structure cement bonded to dentin: (a) porcelain layer fused to metal coping, and (b) porcelain layer fused to ceramic core. Indenter radius r at load P, contact radius a, for number of cycles n, in water. Occlusal surface crack modes, outer cone cracks (O), inner cone cracks (I), and median-radial cracks (M). Porcelain veneer internal surface radial cracks (R), resulting from yield of metal coping (YM) and dentin support (YD); and cementation ceramic core internal surface radial cracks (R), owing to yield of dentin support (YD).
