Effect of aging on microshearing bond strength of different adhesive systems

BACKGROUND: Reliable bonding agents are essential for durable tooth-colored restorations. This study aimed to evaluate the effects of a two-step self-etch adhesive and a universal adhesive (used in self-etch and etch-and-rinse modes) on dentin microshear bond strength and the impact of 1-year simulated thermal aging. METHODS: In this study, 60 caries-free human incisors were used. A two-step self-etch adhesive system (SE) (Clearfil SE Bond; Kuraray Noritake Dental, Japan), a universal adhesive in self-etch mode (U-SE) (Clearfil S3 Bond Universal; Kuraray Noritake Dental, Japan), and the same universal adhesive in etch-and-rinse mode (U-ER) were tested. The specimens were randomly divided into six groups (n = 10 per group): (1) SE, initial measurement without aging (T0); (2) U-SE, initial measurement without aging (T0); (3) U-ER, initial measurement without aging (T0); (4) SE, after artificial aging (T1); (5) U-SE, after artificial aging (T1); and (6) U-ER, after artificial aging (T1). Artificial aging was performed by 10,000 thermal cycles between 5 °C and 55 °C, simulating approximately one year of intraoral conditions. The prepared samples were evaluated using the microshear bond strength test. Non-parametric tests were applied for statistical analysis due to the small sample size and non-normal data distribution, with significance set at p < 0.05. RESULTS: The SE without aging group 1 (15.70 MPa) and SE aged group 4 (11.82 MPa) showed the highest bond strength values, while the U-ER without aging group 3 and aged group 6 consistently presented the lowest (6.58 MPa, 6.33 MPa). After 1-year artificial aging, bond strength significantly decreased in the SE (p