Dentin Adhesive Performance of 5 One-Bottle Universal Adhesives

Objectives: To evaluate the microtensile bond strength (μTBS) and nanoleakage of 5 universal adhesives applied in etch-and-rinse or self-etch mode to sound human dentin.
Methods: Thirty flat surfaces were prepared from mid-coronal dentin derived from caries-free extracted human third molars. A resin composite was placed on the dentin surface that was bond respectively with one of the 5 adhesives (Prime&Bond Elect, Scotchbond Universal, All-Bond Universal, Futurabond U and Clearfil Universal Bond). Each adhesive was employed in the etch-and-rinse mode or the self-etch mode. Bonded specimens were stored in water (37℃/24 h) or subjected to 10,000 times thermo-cycling (5~55℃，dwell time 30 sec). Specimens were sectioned into composite/dentin beams with a cross sectional area of 0.9 x 0.9 mm² and subjected to μTBS testing. Data were statistically analyzed by two-way ANOVA (adhesive/thermo-cycling) and Turkey’s test (a=0.05). Adhesive interfaces and nanoleakage were evaluated by SEM and TEM.
Results: The μTBS for the 5 adhesives used in etch- rinse mode and self-etch mode are shown in the Table. Prime&Bond Elect and Scotchbond Universal showed higher μTBS. No significant difference exist between etch-rinse and self-etch mode for each adhesive (P>0.05). Thermo-cycling decreased the μTBS of several adhesives (Prime&Bond Elect, Futurabond U, Clearfil Universal Bond) in etch-rinse mode, and several adhesives (Futurabond U, Clearfil Universal Bond) in self-etch mode (P<0.05). SEM observation showed that nanoleakage existed in all groups. Futurabond U showed more silver deposits than the other adhesives. In addition, the hybrid layers of self-etch mode groups are thinner than etch-rinse mode for all adhesives.
Conclusions: The 5 adhesives provide high bond strength to dentin in either etch-rinse or self-etch mode. Nanoleakage is still a problem.