Figure 1.

Graded restorative materials; posterior tooth contact; laboratory loading models. (a) Back-scattered electron image of graded glass/zirconia/glass (G/Z/G) structure in sectional view. Note the light zirconia phase, owing to its high atomic weight relative to that of the glass phase. (b) Schematic of occlusion, showing that posterior tooth-tooth contact can be visualized as a spherical indenter sliding down an inclined flat surface. Experimental setup for (c) single-cycle sliding with a translating sphere, and (d) multi-cycle fatigue loading with a 30° inclination angle. The symbol P_c in (c) and (d) denotes the partial cone cracks.