Micro-tensile bond strength of three luting resins to human regional dentin

Objectives To evaluate the micro-tensile bonding strength (μTBS) of three luting resins to human regional dentin. Methods Dentin disks from non-carious third molars were prepared from different regions (s, superficial dentin; d, deep dentin; c, cervical dentin), and divided into groups based on anatomical locations and luting resins (Super-Bond C&B: SB; Panavia F 2.0: PF; RelyX Unicem: RU): SB-s, SB-d, SB-c; PF-s, PF-d, PF-c; RU-s, RU-d, RU-c. Luting resins were used according to the manufacturersʹ instructions, to bond 1-mm-diameter PMMA or composite rods to the exposed dentin specimens under a load of 7.5 N, in the self-curing mode. After storage for 1 or 3 days, μTBS was tested at a cross-head speed of 1 mm/min. Data were analyzed with ANOVA and Fisherʹs PLSD test. The bonding interface and fractography analyses were performed with SEM and TEM. Results ANOVA results showed that μTBS to superficial dentin was significantly higher than to deep or cervical dentin for all three luting resins. SB-s and PF-s, with the highest μTBS, failed primarily cohesively in luting resin. μTBS of SB-d and SB-c were significantly higher than those of PF and RU. RU, with the lowest regional μTBS, failed mostly within demineralized dentin. SEM and TEM showed that adhesive failures in SB and PF occurred at the top of the hybrid layer (HL), but no obvious HL was observed in RU. Significance Luting resins with different chemical formulations and applications yield significantly different bond strengths to different regions in human dentin.