In Vitro Longevity of Bonding Properties of Universal Adhesives to Dentin

Objectives: To evaluate the immediate and 6-month resin-dentin bond strength (μTBS) and nanoleakage (NL) of universal adhesives that contain or not MDP and used in the etch-and-rinse and self-etch strategies
Methods: Forty caries-free extracted third molars were divided into eight groups for μTBS (n = 5). The groups were bonded with the Clearfil SE Bond [CSE] and Adper Single Bond 2 [SB] as controls; Peak Universal, self-etch [PkSe] and etch-and rinse [PkEr]; Scotchbond Universal Adhesive, self-etch [ScSe] and etch-and-rinse [ScEr]; All Bond Universal, self-etch [AlSe] and etch-and-rinse [AlEr]. After composite restorations, specimens longitudinally sectioned to obtain resin-dentin bonded sticks (0.8 mm²). The μTBS of the specimens were tested immediately (IM) or after 6 months of water storage (6M) at 0.5 mm/min. Some sticks at each storage period were immersed in silver nitrate, photodeveloped and the NL evaluated under SEM. Data were analyzed with two-way repeated measures ANOVA and Tukey's test (α = 0.05).
Results: At the IM period, PkSe and PkEr showed μTBS similar to the control adhesives (p > 0.05), but increased NL pattern and lower μTBS after 6M (p<0.05). ScSe and ScEr showed intermediary μTBS values at the IM period, but remained stable after 6 months (p > 0.05). AlSe showed the lowest μTBS (p < 0.05), but μTBS and NL remained stable after 6M (p > 0.05). AlEr showed higher IM μTBS but showed higher degradation after 6M (p < 0.05).
Conclusions: Universal adhesives that contain MDP showed higher and more stable μTBS with reduced NL at the interfaces after 6 months of water storage.