Rationale behind the design and comparative evaluation of an all-in-one self-etch model adhesive

ObjectiveTo investigate and compare bonding and dentin sealing efficacy of a marketed all-in-one and an experimental model adhesive with minimum effective amounts of acidic monomer and water.Materials and methodsComposition of model adhesive (NAD) in mass%: UDMA (45), 4-META (20), H2O (7.5), and acetone (27.5). For characterization of a reasonable NAD application procedure shear bond strengths (SBS, n = 8) were determined on human enamel and dentin. Clearfil S3 Bond (TSB; Kuraray) served as reference. SBSs were evaluated after 10 min, 1 and 7 days, and 1 month, marginal adaptation (n = 8) was assessed in cylindrical butt-joint dentin cavities. Diffusive and convective water fluxes through 1 mm thick adhesive-coated dentin disks (n = 6) were qualitatively and quantitatively analyzed.ResultsSBSs proved that application of NAD in one coat with 20 s agitated dwell time was ≥20 MPa, enamel SBSs (24 h) were 25 MPa, p > 0.05. Dentin SBSs for TSB and NAD were not different (p > 0.05) at the four stages (means: 18.9, 23.5, 25.4, and 23.6 MPa). Five and seven of the eight bonded restorations with TSB and NAD were gap-free (p > 0.05). Dentin disks treated with EDTA from both sides or one side only were highly permeable for liquid, whereas adhesive-coated dentin disks showed no permeability at 0 and 2.5 kPa water pressure.ConclusionsWithin the limitations of this study the model adhesive tested represents a promising basic composition for all-in-one adhesives, eliminating common problems encountered with single step adhesives such as phase separation and permeability.