Cracks formed by Vickers indentation adjacent to the interface in bonded dental ceramics with various marginal angles

The objective of this study was to assess the influence of the ceramic marginal angle on the length and nature of indentation cracks in ceramics near the ceramic/resin bonded interface. Disks of a leucite-reinforced ceramic or a diopside-based glass-ceramic bonded to a resin composite were sectioned so that the ceramic marginal angles were 45, 60, and 90°. Vickers indentations were placed in the ceramic at various distances from the bonded interface. The lengths of the indentation cracks running near parallel to the interface were measured and the orientation of crack propagation was characterized. The crack length and orientation were significantly affected by the distance from the interface and by the marginal angle, respectively. The crack length extended as the distance from the interface was shortened. Smaller marginal angles resulted in more oblique cracks. The toughness of the ceramic affected the indentation crack length, shape, and direction.