FRACTURE-MECHANICS PARAMETERS OF THE COMPOSITE-ENAMEL BOND

In a previous study, the critical values of the opening mode stress intensity factor (K1), its equivalent, the strain energy-release rate (G1), and the J integral (J1) (in the elastic case being equal to that of G1) were determined for resin composite. In this study, the strength of the composite-tooth interface was investigated. The critical values of K1 and J1 were measured with single-edge notched-bend (SENB) specimens of resin composite bonded to enamel, with the notch at midspan at the bonded interface. Due to enamel's anisotropy, the values of K1c and J1c to be used in a fracture-mechanics application for failure prediction of a structure depend on the enamel prism orientation relative to the adhesive interface. Where interfacial failure is to be expected, the following values for J1c and K1c can be used: Silux, J1c = 145 ± 35 Jm-2 and K1c = 0.84 ± 0.16 MNm-3/2; P-30, J1c = 163 ± 13 Jm-2 and K1c = 1.02 ± 0.07 MNm-3/2. Where enamel failure is expected or where the failure mode cannot be predicted, the following values can be applied: Silux, J1c = 89 ± 15 Jm-2 and K1c = 0.84 ± 0.16 MNm-3/2; P-30, J1c = 89 ± 15 Jm-2 and K1c = 0.75 ± 0.10 MNm-3/2. © 1990, SAGE Publications. All rights reserved.