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High Performance Liquid Chromatography for HEMA detection in SE adhesives

Objective: One of the factors that can decrease hydrolytic stability of self-etching adhesive systems (SEAS) is 2-hydroxyethylmethacrylate (HEMA). Due to hydrolytic instability of acidic methacrylate monomers in SEAS, HEMA can be present even if the manufacturer did not include it in original composition. The aim of the study was to determine the presence of HEMA G-Bond because of decomposition by hydrolysis of methacrylates during storage, resulting with loss of adhesion strength to hard dental tissues of the tooth crown. Method: Two most commonly used SEAS were tested: G-bond and AdheSE ONE under different storage conditions. High performance liquid chromatography (HPLC) analysis was performed on a Nucleosil C18-100 5 &micro ; ; m (250x4.6 mm) column, Knauer K-501 pumps and Wellchrom DAD K-2700 detector at 215 nm. Data were collected and processed by EuroCrom 2000 HPLC software. Samples of adhesives (~70 mg) were dissolved in 2.0 ml of methanol and filtered ; 20 &micro ; ; l were injected and isocraticaly eluted with 20% aqueous methanol for 15 min, followed by gradient to 100% methanol in 5 min. Calibration curves were made relating eluted peak area to known concentrations of HEMA (purchased from Fluka). The elution time for HEMA is 12.25 min at flow rate 1.0 ml/min. Result: Obtained results indicate that no HEMA was present in AdheSE ONE because methacrylates are substituted with methacrylamides that seem to be more stable under acidic aqueous conditions. HEMA was detected in G-Bond. Conclusion: Special concern should be taken on storage period end storage conditions because HEMA can be produced due to decomposition of methacrylates by hydrolysis during storage.

High performance liquid chromatography; self-etching adhesives; HEMA

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