Figure 7.

SEM magnification of the secondary edge chip from Fig 5 starting on the exposed zirconia frame on the palatal surface next to some glaze remnant. The initial flaw size of the chip is of 35 μm and delimited by an arrest line. This edge chip crack is however stopped soon after as seen by the absence of hackle penetrating into the core beyond the chip size, indicating that this is a secondary event. Many micro-fine texture hackle visible in the core material are propagating downwards to the gingival margin, perpendicular to the edge chip (big white arrows).