Acoustic emission characterization of the marginal disintegration of dental composite restoration

The contraction stress and the disintegration around the margin of a dental composite restoration were analyzed by measuring the circumferential strain on the outer surface of a ring-type dental substrate. AE signals were monitored in real time to observe the marginal disintegration process of the restoration. All tested restoration specimens generated blast-typed AE signals, each having a principal frequency band of 100–200 kHz during polymerization shrinkage. An improvement in the bonding state between the composite resin and the substrate caused a considerable decrease in AE hits. The distribution of AE hits versus curing time was significantly different depending on the substrates and the interfacial bonding treatments. The increase in the marginal gap size represented the increase in the number of crackings along the margin and thus corresponded to the large number of AE hits detected. Therefore, AE behaviors could be used as a nondestructive evaluation index for the marginal disintegrative fracture.