Purpose: To evaluate the influence of peripheral enamel bonding, chlorhexidine digluconate (CHX) pretreatment, and storage time on resin-dentin microtensile bond strength (µTBS) of a self-etching adhesive system and selfetching cement.
Materials and Methods: Fifty-six noncarious human third molars were coronally sectioned to provide a flat dentin surface; the circumferential enamel was removed from half of these and the other half was left intact. Pretreatment with 0.2% or 2% CHX or none (control) was performed before bonding composite blocks with Panavia F2.0 or RelyX Unicem to dentin. Specimens were stored in 0.5% chloramine for 3 days (control) or 6 months. Bonded specimens were sectioned into 1-mm2 dentin-only beams and a tensile load was applied until failure. The resulting 14 test groups, defined by control group/storage time/cement/CHX application mode/enamel bonding, were analyzed using two-way and three-way ANOVA, as well as Tukeys HSD post-hoc test (α = 0.05). Failure patterns of the specimens were observed and measured using scanning electron microscopy.
Results: The comparison of the control vs experimental subgroups with peripheral enamel bonding and without CHX pretreatment after six months found no significant differences regarding the µTBS between the cements (p > 0.05) but did for the storage time (p <= 0.05). When storing the specimens for six months, the absence of peripheral enamel bonding significantly decreased the µTBS (p <= 0.05). Panavia F2.0 specimens showed significantly higher µTBS values than RelyX Unicem specimens (p <= 0.05). CHX pretreatment, regardless the concentration, showed a significant influence on the µTBS (p <= 0.05). SEM revealed that peripheral enamel bonding reduced failures at the resin/dentin interface.
Conclusions: The absence of peripheral enamel bonding and a longer storage time decrease the µTBS of twostep self-etching adhesive system and a one-step self-etching cement. CHX pretreatment of the dentinal surfaces seems to improve the durability of the bond to dentin.
Keywords: microtensile testing, adhesive systems, chlorhexidine, dentin bonding, durability, composites, storage time