Development of dental inspection method: Nondestructive evaluation of an adhesive interface by ACTIVE acoustic emission.

Purpose This study aims to confirm the usefulness of active acoustic emission (Active AE) for reproducible and non-invasive generation of physical external force which is required for conventional AE. Methods Experiment 1: A root dentin-resin adhesive interface was observed. The post space was filled with a dual-cure resin composite core material with and without adhesive. The vibration characteristics of the data obtained from the time-frequency analysis were evaluated. Experiment 2: A crown-abutment tooth adhesive interface was observed. Adhesive resin cement was used for luting the crown and adhesion states in the same specimen over time were analyzed with three measurements: at trial-fitting, immediately after luting, and 2 weeks after luting. Data were subjected to time-frequency analysis and relationships between amplitude (indicating loudness) and frequency (indicating the sound component) were analyzed. Results Experiment 1: Time-frequency analysis confirmed multiple peak frequencies for each specimen without adhesive and monomodal peak frequency in all specimens using adhesive. Experiment 2: Two weeks after luting, all specimens showed a single major peak except one which showed multiple weak peaks.The three-dimensional visualization of time-frequency analysis revealed one specimen with multiple weak peaks while all others displayed a single, low-amplitude band at 2 weeks after luting. Conclusions The state of the adhesive interface can be evaluated using active AE. This basic technique may prove useful to evaluate changes in the adhesive interface of prostheses over time.