Bonding durability of HEMA-free and HEMA-containing one-step adhesives to dentine surrounded by bonded enamel

Objective To evaluate the bonding durability of HEMA-free and HEMA-containing one-step adhesives to dentine surrounded by bonded enamel after 1-year storage in water. Material and method Flat coronal dentine surfaces of extracted human molars were prepared, leaving the surrounding enamel. Two one-step self-etch adhesive systems: HEMA-containing Tri-S Bond (TSB; Kuraray Medical Inc., Tokyo, Japan) and HEMA-free G Bond (GB; GC Co., Tokyo, Japan), were applied to both dentine and the surrounding enamel surfaces according to manufacturers’ instructions. Following resin composite crown (Clearfil AP-X, Kuraray Medical Inc., Tokyo, Japan) build-ups, the bonded specimens were stored in 37 °C water for 24 h (control group), 3 months, 6 months and 1 year. After the designated periods of water storage, the specimens were serially sectioned perpendicular to the adhesive interface into 0.7 mm thick slabs, and then trimmed to form hour-glass configurations with a 1 mm2 cross-sectional area. The micro-tensile bond strength (μTBS) test was carried out at a crosshead speed of 1.0 mm/min. The μTBS data were statistically analyzed using two-way ANOVA, t test, and Tukeyʹs HSD post hoc multiple comparison tests (α = 0.05). Results After 1 year water of storage, the bond strength of TSB to dentine was significantly lower compared with the 1-day, 3-month and 6-month groups (p < 0.05). On the other hand, the μTBS of GB decreased over time, but there was no significant difference between the experimental periods (p > 0.05). Clinical significance Bonded enamel margins may not maintain the integrity of the resin–dentine interface created by HEMA-free and HEMA-containing one-step adhesives.