Remaining unreacted methacrylate groups in resin‐based composite with respect to sample preparation and storing conditions using micro‐Raman spectroscopy

Abstract

The aim of this study was to measure degree of conversion (DC) of resin-based composites (RBCs) using micro-Raman spectroscopy followed by different sample preparation procedures and storing conditions. Ninety samples of Tetric EvoCeram (Ivoclar Vivadent, Schaan, Liechtenstein) were prepared in standardized molds and cured with a high powered LED light-curing unit, bluephase (Ivoclar Vivadent, Schaan, Liechtenstein) for 20 s. Samples were allocated to eight groups. DC of groups 1 and 2 was recorded without or after polishing. DC in groups 3 and 4 was recorded from vertically sectioned samples versus "split" samples. DC in groups 5-8 was recorded after storing samples at room temperature and humidity, in 90 +/- 2% humidity at 37 +/- 1 degrees C, distilled water at 37 +/- 1 degrees C or buffered incubation medium (BIM) at 37 +/- 1 degrees C for 24 h. Mean values of DC in polished and unpolished samples were 63.6% (+/-3.2%) and 54.7% (+/-5.2%), respectively (p < 0.0001). There was no significant difference in DC after sample-sectioning (p > 0.05). Significantly higher DC values were obtained after storing samples in BIM (76.8% +/- 2.1%) than in distilled water (59.7% +/- 5.7%), extreme humidity (60.3% +/- 3.9%) or in room conditions (63.6% +/- 3.2%) (p < 0.001). DC of an RBC measured by micro-Raman spectroscopy may be affected by differences in sample preparation and storing conditions, making it difficult to extrapolate data from in vitro studies into clinically relevant information.