Eight-year microtensile bond strength to dentin and interfacial nanomechanical properties of a one-step adhesive
Abstrakt
Purpose: To evaluate the microtensile bond strength (μTBS) of a one-step self-etch adhesive (1-SEA) to dentin and its interfacial nanomechanical properties after 8 years of water storage. Materials and Methods: Flat coronal dentin surfaces of extracted human third molars were bonded with a 1-SEA (Clearfil S3 Bond Plus, CS3+) and built up with a hybrid resin composite (Clearfil AP-X).
After storage in water for 24 h or 8 years, non-trimmed stick-shaped specimens were fabricated from the central part of each bonded tooth and subjected to the μTBS test at a crosshead speed of 1.0 mm/min. Failure modes and the morphology of debonded interfaces were analyzed using a scanning electron microscope (SEM).
In addition, the elastic modulus (E) and hardness (H) of the adhesive layer and the resin composite were determined by an instrumented nanoin- dentation test. The acquired μTBS, E, and H data were statistically analyzed using t-tests to examine the effect of storage time (α = 0.05).
Results: The 8-year μTBS was slightly lower than that after 24 h, but the difference was not significant (p = 0.123). The SEM observation of debonded surfaces after 8 years revealed extrusions and lacunas.
E and H of the adhesive layer and the resin composite significantly decreased over the 8-year water storage (p < 0.001). Conclusions: Although 8 years of water storage did not decrease the μTBS of CS3+ significantly, the observed fail- ure mode patterns and significantly decreased nanomechanical properties indicated resin degradation of the adhe- sive and the resin composite.