High Resolution Qualitative Ultrasonic Evaluation of Ceramic/Adhesive Interface

The load bearing capacity of resin retained ceramic restorations depend greatly on the flaw density population and the integrity of the adhesive interface. For accurate clinical survival or remaining lifetime estimates it will be necessary to understand the interface state. Objective: To determine whether noninvasive ultrasonic methods can be utilized to assess the interface state during restoration service. Methods: the occlusal table of extracted human teeth were flattened to expose the dentin. Ceramic plates (ProcadŽ, Ivoclar) 1.5mm thick were adhesively cemented (Nexus 2, Kerr) to the flattened tooth surfaces using standard ceramic bonding techniques. Specimens were divided in three groups and were either scanned within a few days of bonding (control), stored in water at 37°C for up to 1 year (aged), or thermocycled (TC) to accelerate aging. Immersion scanning was performed on the flat ceramic surfaces using a 50MHz focused transducer (Panametrics) with a focal length of 0.5 inch. The surface was scanned with a transducer focused on the bond line at a 2 mm/sec scanning speed with 0.004 inch increments. The reflected ultrasonic signature of the interface was analyzed for the three groups. Results: Interpretation of the B (cross-section imaging) and C scans (in-plane imaging) in a form of high resolution images revealed the presence of areas of delaminations on the TC group. The aged group showed less dramatic but obvious differences in signal characteristics at the interface than the control group. Conclusions: Noninvasive high resolution ultrasonic imaging is a valuable tool for the detection of interface delaminations. Further work is needed to correlate the more subtle signal changes with meaningful physical characteristics.

This work was supported by NIHDCR R21-DE14719