Objectives : The free radical concentrations of resin materials do not only compromise the material polymerization properties but also may impact its overall biocompatibility due to higher concentrations of residual monomers. The aim of this study was to detect free radical concentrations of three new self-adhesive resin cements using electron spin resonance (ESR) spectroscopy.
Materials and methods : Cylindrical-shaped (3 mm × 8 mm) specimens with four different test materials (ICem-Hareaus Kulzer, Clearfil SA Cement-Kuraray, G-Cem-GC Corp., GC Fuji Plus-GC Corp.) were prepared. Fuji Plus was the control. For measurements, X-band ESR spectrometer (Bruker, Germany), operating at microwave frequency (94,616 GHz), was used. The settings of experimental system were as follows: microwave power, 1.5 mW; modulation amplitude, 1 Gauss; sweep width, 150 Gauss. The materials were placed into cylindrical ESR quartz tubes of 4 mm in diameter, and the immediate measurements were taken at different temperature (0, 25 and 37 °C). The specimens were then subjected to thermal cycling for 3000 cycles between 5 and 55 °C. After 1 month aging in distilled water, the test was repeated for 25 °C specimens.
| Materials | Relative intensity (ESR signal) | Hyper fine constant (peak to peak) | Number of ESR lines | |||
|---|---|---|---|---|---|---|
| Immediate | 1 month | Immediate | 1 month | Immediate | 1 month | |
| ICEM | 4.0 × 10 3 | 0.8 × 10 3 | 12 Gauss | 12 Gauss | 9 | 9 |
| G-CEM | 8.0 × 10 3 | 16.0 × 10 3 | 22 Gauss | 22 Gauss | 9 | 9 |
| CLEAR. SA | 4.0 × 10 3 | 3.3 × 10 3 | 12 Gauss | 12 Gauss | 9 | 9 |
| FUJI PLUS | 1.0 × 10 3 | No | 12 Gauss | No | 9 | No |
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