Adhesion performance of new hydrolytically stable one-component self-etching enamel/dentin adhesives.
OBJECTIVE
To demonstrate that hydrolytically stable methacrylamide monomers allow one-component self-etching adhesives with comparable adhesive properties and better storage stability than hitherto available methyacrylate-based adhesive formulations.


METHODS
The shear bond strength and storage stability of the new one-component self-etching, methacrylamide-based adhesive AdheSE One F (Ivoclar Vivadent) to enamel and dentin was compared to the methacrylate-based Clearfil S3 Bond (Kuraray), G-Bond (GC), Hybrid Bond (Sun Medical), iBond (Heraeus Kulzer), Optibond All In One (Sybron-Kerr), and the methacrylamide-based Xeno V (Dentsply). Hydrolytic stability and adhesive performance of these adhesives was evaluated by accelerated aging at 42 degrees C over 16 weeks and monthly assessment of shear bond strength to dentin. The null hypothesis was that the bond strength of one-bottle self-etching dental adhesives is independent of storage duration and that, disregarding their higher stability against hydrolysis, methacrylamide- based materials offer performance beyond shelf-life time, comparable to methacrylate-based adhesives. Statistical analysis included 1-way-ANOVA and the Tukey-B post-hoc test (p < 0.05).


RESULTS
Shear bond strengths on enamel ranged from 32.7 MPa (AdheSE One F) to 16.6 MPa (iBond) and on dentin from 36.1 MPa (Optibond All In One) to 20.5 MPa (G-Bond). During accelerated aging, methacrylate-based adhesives with a pH < 2 exhibited decreasing bond strengths over time with material-dependent losses of up to 68% (Hybrid Bond, 8 weeks, 42 degrees C). Under the same conditions, the methacrylamide-based formulations AdheSE One F and Xeno V were stable for 16 weeks regarding shear bond strength to dentin.


CONCLUSIONS
The shelf life of one-component self-etching adhesives is determined by their chemical composition. In conventional methacrylate-based adhesives, the inherently acidic environment of such formulations leads to monomer degradation due to hydrolysis. In contrast, methacrylamide-based adhesives are stable to aqueous acid and exhibit much superior storage stability without monomer degradation-related losses in adhesion performance.
Research and Development, Ivoclar Vivadent, Schaan, Liechtenstein. ulrich.salz@ivoclarvivadent.com
Ulrich
U
Salz
Thorsten
T
Bock
D000134:Acid Etching, Dental / Q000379:methods; D000178:Acrylamides; D000180:Acrylic Resins / Q000737:chemistry; D000269:Adhesives / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D001840:Dental Bonding; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D004356:Drug Storage; D006868:Hydrolysis; D008422:Materials Testing; D008689:Methacrylates; D019279:Resin Cements / Q000737:chemistry*; D033081:Shear Strength
D000178:Acrylamides; D000180:Acrylic Resins; C489662:AdheSE cement; D000269:Adhesives; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; C045985:methacrylamide