Degree of conversion and surface hardness of bulk-fill composite versus incremental-fill composite

ObjectiveThe aim of this study was to evaluate the degree of conversion and surface hardness of two bulk-fill composites and one incremental-fill composite.MethodsBulk-fill composites (x-tra fil, Voco; QuiXfil, Dentsply) and incremental-fill composite (Grandio, Voco) were used. Twenty five cylindrical specimens (5 × 4 mm) were made from each material in Teflon molds. Mold was filled in one increment for the bulk-fill composites and in two increments for the incremental-fill composite. Specimens were stored dry in dark at room temperature for 24 h before testing. Degree of conversion (DC) was determined using Fourier transform infrared spectroscopy (FTIR). A microhardness tester was used to measure the Vickers hardness number (VHN) on top and bottom surfaces of each specimen. Data for DC and VHN were analyzed by ANOVA and pair-wise Newman–keuls test.ResultsX-tra fill recorded significantly the highest DC, while no significant difference was noted between the other two composites. The VHN mean values of all composites tested were significantly different from each other (P < 0.0001), either in top or bottom surface, with Grandio showed the highest mean value and QuiXfil showed the lowest mean value. Only QuiXfil recorded no significant VHN difference between its top and bottom surfaces. There was no significant difference in bottom/top hardness ratio% among materials. Non significant Correlation between VHN and DC was noted.ConclusionsX-tra fil showed the most DC performance. Incremental-fill composite showed higher VHN than bulk-fill composites. Differences in DC and VHN values among materials proved to be a material dependent.