Objectives: To evaluate the micro-tensile bonding strength (muTBS) 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 manufacturers' 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, muTBS was tested at a cross-head speed of 1mm/min. Data were analyzed with ANOVA and Fisher's PLSD test. The bonding interface and fractography analyses were performed with SEM and TEM.
Results: ANOVA results showed that muTBS 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 muTBS, failed primarily cohesively in luting resin. muTBS of SB-d and SB-c were significantly higher than those of PF and RU. RU, with the lowest regional muTBS, 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.