Can a new HEMA-free two-step self-etch adhesive improve dentin bonding durability and marginal adaptation?
Abstract
Purpose: A new two-step self-etch adhesive (2-SEA) free of hydrophilic monomers was evaluated. Its micro-tensile bond strength (TBS) to dentin under various aging conditions, interfacial gap formation, water sorption/solubility, and formation of an acid-base resistant zone (ABRZ) were evaluated and compared with a gold-standard 2-SEA.
Materials and methods: The new 2-SEA G2-Bond Universal (G2; GC) was compared to Clearfil SE Bond 2 (CSE2, Kuraray). Their TBS to sound coronal dentin was tested after 1 week, 10,000 thermal cycles (TC), 20,000 TC, 6 months and 1 year.
Failure mode was determined using scanning electron microscopy (SEM). Gap formation at the interface of 2-mm deep tapered cavities with the enamel border was observed using swept-source optical coherence tomography after 1 day, 1 week, 10,000 TC, and 20,000 TC.
In addition, water sorption and solubility of the bonding agents was measured, and ABRZ formation was evaluated using SEM. Results: There was no significant difference in TBS between G2 and CSE2 (p>0.05), and the aging conditions had no significant effect on TBS (p>0.05).
In all groups, cohesive failures prevailed (55-95%). Interfacial gap formation was initially similar for both adhesives (p>0.05), but G2 exhibited a significantly lower gap formation than CSE2 after TC (p0.05).
ABRZ of similar thickness was observed with both adhesives. Conclusion: The new 2-SEA exhibited stable dentin bonding and increased hydrophobicity resulting from the absence of hydrophilic monomers.