Fracture Mechanics Analysis of an Anterior Resin Bonded Bridge Including the Effects of Tooth Mobility

The effects of design parameters on crack growth along the adhesive layer in a resin-bonded first incisor/canine bridge are analysed using a finite element (FE) model in which allowance is made for tooth mobility by including elastic supports for the abutment teeth. The energy release rate, G, for incipient cracks in the adhesive layer are calculated for various crack lengths, metal frame configurations, frame thicknesses and tooth mobilities. Energy release rates for bridge frame designs with and without wrap round, denoted by Gw and G0, respectively, decrease as the metal frame thickness increases. The difference DG =Go–Gw reaches a maximum with respect to the crack length, a, in the range 0.3 < a < 0.6mm, depending on the frame thickness. The effect of tooth mobility becomes increasingly important in the FE model as the overall stiffness of the bridge increases. Critical lengths for incipient cracks in the adhesive layer are estimated for a range of factors of safety against the onset of unstable crack propagation. KEY WORDS: Fracture mechanics; Resin-bonded bridge; Tooth mobility