Characterization of Four Bulk-fill Resin Composites

Objectives: Filling all of a tooth preparation with composite at one time has obvious advantages, however, this is still a controversial and evolving topic. Get to know the bulk-fill restorative-resins is the best way to taking doubts away on choosing the restorative material. The aim of this study was to analyse several mechanical-physical properties of four bulk-fill composites currently available.
Methods: Aura Bulk Fill-AB (SDI); X-tra Fill-XT (Voco), Filtek Bulk Fill-FB (3M/ESPE) and Tetric N-Ceram Bulk Fill-TN (Ivoclar/Vivadent) were light-cured according to manufacturer instructions. Degree of conversion (DC) was measured by FTIR, depth of cure was determined using ISO 4049:2006 standard, thermal decomposition and filler content were assessed by thermogravimetric analysis (TGA). Energy-dispersive X-ray fluorescence (EDX) was employed to evaluate the filler content. Surface roughness (Ra) was measured using surface profilometer after 24h and after thermal cycling (500 cycles at 5–55^OC, 30s each). Data were analyzed by one-way ANOVA, Tukey, (α=0,05).
Results: Surface DC values were significantly lower for XF (46.6%) and higher for FT (78.7%). There were no significant different values for the scraping method for depth of cure for all bulk-fill resin composites (p=0.919). Initial thermal decomposition temperature assessed by TGA for was variable and can be ranked as follows: XF>TE>FB>AB. By means of EDX, similar elements such as C, O, Ba, and Si were detected in AB, TN and XF, but the concentration was different in every composite-resin. Other elements such as Al (AB), S (XF), Br and Zn (TN) were also detected. FB presents C, O, F, Si, Zr and Yb. After 24h Ra means have not shown a significant difference between TN/FT (p=0.770); FT/XF (p=0.067), XF/AB (p=0.858). Roughness of all composites increased after thermal cycling, without significant difference (p=0.733).
Conclusions: Physical-mechanical analyzed properties showed that bulk-fill resin composites can be used safely in increments of 4-5 mm thickness.