Margin failures in crown‐like brittle structures: Off‐axis loading

Abstract

The effect of off-axis loading of compliant indenters on the initiation of cracks at the margins of dental crown-like dome structures consisting of glass shells back-filled with an epoxy resin is examined. As in previous studies on similar structures but with strictly axial loading, cracks can be made to initiate and propagate from the margins around the dome faces into a "semi-lunar" fracture pattern characteristic of some all-ceramic crown failures. In this study, balsa wood and teflon disk indenters are used to provide the off-axis loading, at 45 degrees to the dome axis. The soft indenters, considered representative of food bolus, spread the contact at the top surface, suppressing otherwise dominant radial cracks that ordinarily initiate at the dome undersurface directly along the load axis beneath harder indenters. Finite element modeling is used to show that off-axis loading dramatically increases the tensile stresses at the near-side dome margin, strongly diminishing the loads required to generate the lunar fracture mode.

The effect of various sandblasting conditions on surface changes of dental zirconia and shear bond strength between zirconia core and indirect composite resin

“…It should be noted that the thickness of the supporting substrate plays the most important role in selecting the mechanical resistance to bite force, particularly at the margins of restorations or copings. 33 The thickness of zirconia copings is from 0.5 to 0.7 mm. 34 35 It is even smaller in some brands of zirconia or at the marginal edges.…”

Predicting failure in mammalian enamel

“…The third example shows a crack pattern formed beneath a Teflon disk, loaded at 45 • to the vertical (Fig. 3(c)) (Ford et al, 2008). In this case the soft contact has engulfed the shoulder of the dome, suppressing In each case shown in Fig.…”

The influence of fallback foods on great ape tooth enamel

“…Yet another form of fracture is that of ''margin'' cracking. In this mode, cracks initiate at the cemento-enamel junction (CEJ) and propagate longitudinally upward in a stable manner, increasing in length with the applied loading, somewhat analogous to their radial-median counterparts but with growth in the opposite direction (Ford et al, 2008). As with radial-median cracks, the failure load P MF for margin cracks depends on tooth dimensions, although somewhat less on d and more on r e .…”