Video rate confocal microscopic imaging of dentin/adhesive interfacial failure under load

Purpose: To obtain information on interfacial failure by recording video ra te images of the interface as it failed, while simultaneously recording the load applied. Materials and Methods: Fluorescent labeled adhesives were us ed to retain resin-based composite bobbins on the flat exposed dentin surfa ce of teeth included in epoxy resin blocks. The teeth were secured in a min iature straining stage while the bobbins were loaded in shear mode and the interface viewed with a tandem scanning confocal microscope. Images of the interface during failure were recorded with the aid of computer image proce ssing and storage. The dynamic failure pattern, site of failure (after repo sitioning the fractured bobbin under the microscope) and shear bond stress were analyzed for four dentin adhesives [OptiBond (OB), Scotchbond Multi-Pu rpose Plus (SBMP+), Clearfil Liner Bond 2 (CFLB2) and ESPE Bonding System ( EBS)]. Control specimens without fluorescent dyes were also studied. Four d ynamic patterns of failure were observed: snap, slip/stick, peel and shock wave were seen respectively with OB, SBMP+, CFLB2 and EBS adhesive. The she ar bond strengths were ranked EBS*>OB>SBMP+>CFLB2* (*statistically differen t at proportional to =0.05). No significant difference was found between sp ecimens with and without fluorescent dye.