Effects of long-term water storage on the microtensile bond strength of five experimental self-etching adhesives based on surfactants rather than HEMA

Objectives

The purpose of this study is to evaluate the hypothesis that replacing 2-hydroxyethyl methacrylate (HEMA) for surfactant dimethacrylates (SD) does not affect the immediate and long-term microtensile bond strength (μTBS) of experimental two-step self-etch HEMA-free adhesive systems applied on dentin.

Materials and methods

Five experimental HEMA-free two-step self-etching systems containing different SD (ethoxylated bisphenol A diglycidyl dimethacrylate (Bis-EMA 10, B10), Bis-EMA 30 (B30), poly-ethyleneglycol (400) dimethacrylate (PEG 400, P400), PEG 1000 (P1000), and PEG 400 urethane dimethacrylate (UDMA) (UP400)) and a HEMA-containing system (control) (HA) were formulated. Specimens were subjected to the μTBS test after 24 h and 6 and 12 months of storage. Data (in megapascals) were analyzed by Kruskal–Wallis and Dunn tests (α?=?0.05).

Results

Medians of the μTBS data after 24 h of storage are: HA?=?57.2^A, B10?=?26.2^BC, B30?=?24.0^C, P400?=?32.6^BC, P1000?=?37.3^B, and UP400?=?57.9^A; after 6 months are: HA?=?47.9^A, B10?=?18.5^B, B30?=?7.8^C, P400?=?16.1^B, P1000?=?14.6^BC, and UP400?=?51.6^A; and after 12 months are: HA?=?31.2^A, B10?=?15.2^B, B30?=?9.0^B, P400?=?9.1^B, P1000?=?13.3^B, and UP400?=?35.7^A. Between the HEMA-free groups, the adhesive system formulated with PEG 400 UDMA produced similar μTBS to the HEMA-containing group. Also, the storage of specimens decreased the μTBS (p?<?0.05).

Conclusion

Replacing HEMA for PEG 400 UDMA in an adhesive system formulation generated a satisfactory μTBS to dentin.

Clinical relevance

Surfactant dimethacrylates have a potential use in the development of HEMA-free self-etching adhesive systems, which are more chemically stable.