Slow progression of dentin bond degradation during one-year water storage under simulated pulpal pressure

Abstract 

Objectives

To evaluate the dentin bond durability of simplified adhesives after one-year (1y) under water storage and simulated pulpal pressure.

Methods

Class I cavities were prepared in sixty human third molars with the pulpal wall located in mid-coronal dentin. The roots were cut off to expose the pulpal chamber, and the teeth were assembled in a pulpal pressure simulator device. A two-step etch-and-rinse adhesive (Single Bond 2/SB), a two-step self-etch adhesive (Clearfil SE Bond/CSE), a three-step self-etch adhesive (Adper Scotchbond SE/SSE) and three all-in-one adhesives (Adper Easy Bond/EB, Clearfil S³ Bond/S3 and Adhese One/AO) were applied according to manufacturerś instructions. No enamel pre-etching was used for the self-etch systems. The cavities were filled with a composite (Z250, 3M ESPE) in four to five horizontal increments and individually cured. Immediately after the final cure, pulpal pressure was set to 15cm H₂O. After 24h and 1y under simulate pulpal pressure the teeth were cut following a ‘nontrimming’ microtensile test technique (n=30) and tested in tension. Kruskall–Wallis and post hoc multiple comparisons were used at α=0.05. Weibull statistics was applied to SB, CSE and EB. Fractographic analysis of debonded specimens was performed using scanning electron microscopy.

Results

At 24h and 1y periods, SB showed higher bond strength means than all the others adhesives tested. CSE was not statistically different from EB at 24h and from EB and SB at 1y. EB showed bond strength statistically higher than the other three self-etch adhesives, which were not statistically different from each other at 24h. AO showed significantly lower bond strength than all tested materials after 1y. For all adhesives the mean bond strength at 1y were not statistically different from the values measured at 24h (p>0.05). Shifts in failure mode patterns and Weibull modulus decrease indicate some degree of bond degradation after the 1y storage period.

Conclusion

One-year of simulated pulpal pressure did not affect dentin bond strength of simplified adhesives in Class I restorations. Signs of degradation were only revealed by fractographic analysis and reliability parameters.

Keywords: Durability, Degradation, Bond, Dentin, One-step, Self-etch, Adhesive, Simulated, Pulpal pressure