Objectives . In this paper, a non-destructive testing technique – acoustic emission (AE) – was used to monitor the development of micro-debonding in a dental restoration during the polymerization of the dental composite.
Materials and methods . Five steps were involved in the test: Step I – cutting a class I cavity in a human molar; Step II – applying adhesives and filling the tooth cavity with dental composite; Step III – fixing an acoustic emission sensor on the (buccal or lingual) surface of the tooth and setting up the AE system (2-channel AE system from Physical Acoustics Corporation, NJ, USA); Step IV – turning on the AE system and curing the composite with blue light; Step V – keeping record the AE data for 10 min. The curves of instantaneous and accumulated AE events vs. time were used to study the debonding development.
Results . AE events caused by micro-debonding were first detected after about 25 s from the start of curing. For most cases, there was a period of rapid increase of AE events between 30 s and 40 s. However, a small amount of AE events could still be detected even after a few minutes. This was accordant with the development of shrinkage stress in dental composites. The number of AE events and the history of their development were significantly different between the samples.
Conclusions . AE measurement techniques can be used to monitor micro-debonding in dental composite restorations during curing.