Microtensile Dentin Adhesive Bond Strength After ESEM Vacuum Exposure

The dentin/adhesive interface was studied under wet conditions using the Environmental Scanning Electron Microscope (ESEM) to determine if the vacuum weakened the adhesive interface during observation.  Objectives: To compare the microtensile bond strength of an ethanol based, two-step total etch adhesive system PQ1 Ultradent^TM bonded to dentin with and without exposure to an ESEM vacuum.  Methods: After IRB approval, two 3^rd molar teeth extracted from each of four patients received a rectangular class I occlusal preparation 5.0 x 7.0 x 2.0 mm.  Each preparation was restored with the adhesive and 3M^TMESPE^TMFlitek^TMZ250 Universal Restorative following manufacturer's directions.  After 24 hours of storage in water at 25^oC, each tooth was sectioned to obtain two slices 0.75 mm wide.  One slice was etched for 5.0 sec with 35% phosphoric acid to remove the smear layer and exposed to ESEM vacuum at 5.4-6.0 torr for 30 minutes at 10.0 kV up to 1000x under wet conditions and the other slice remained untreated.  Each slice was further sectioned to obtain 4-5 rectangular specimens with a surface area of 0.5 mm². Samples were tested on an EnduraTEC ELF 3300 at a crosshead speed of 1.0 mm/min till failure. A previous pilot study determined that 21 samples/group were necessary to detect a statistically significant difference of 25% between means at p ≤ 0.05 and β = 0.20.

Results:

There was no statistically significant difference between means (t-test (p≤0.05)). Conclusion: Exposure of the dentin adhesive interface under vacuum and wet conditions on the ESEM had no effect on the microtensile bond strength of the dentin adhesive interface.  Supported in part by USPHS Grant K23-DE016324.   purkj@umkc.edu