Effects of crosslinker-modified etchants on durability of resin-dentin bonds in sound and caries-affected dentin

To formulate crosslinker-modified etchants with phosphoric acid (PA) and an organic acid for effective dentin demineralization while addressing solubility issues, and to evaluate their impact on bond strength, nanoleakage, and matrix metalloproteinases (MMP) activity in sound dentin (SD) and caries-affected dentin (CAD) before and after thermocycling.

Crosslinker-modified etchants were prepared by mixing 35 % tartaric acid (TA) and 10 % PA and adding 1 % of theaflavins (TF), cranberry extract (CR), or EDC/NHS (EDC). The etchants without crosslinker were used as controls. Dentin surfaces of 74 human molars were exposed, and 35 of them were submitted to a microbiological cariogenic challenge to create CAD. Specimens from SD and CAD were randomly allocated into 10 groups according to the different etchants. Resin-dentin interfacial bonding properties were evaluated after 24 h and after 10,000 thermocycling through microtensile bond strength (μTBS), nanoleakage and MMPs activity via in situ zymography. Statistical analysis was performed using ANOVA followed by Games-Howell or Tukey's tests.

Compared to the control and EDC-modified groups, TF- and CR-modified etchants maintained stable bond strength and significantly reduced MMP activity, preserving this protection even after thermocycling, which simulates one year of clinical aging, regardless of dentin type (both SD and CAD). While their impact on nanoleakage in CAD was less pronounced after thermocycling, it remained below 50 % of the levels observed in the control and EDC-modified groups.

Crosslinker-modified etchants, particularly TF and CR, provide a promising approach for simultaneous etching and biomodification of clinically relevant dentin substrates, enhancing bonding durability.