Surface Roughness of Bulk Fill and Low-Stress Composites

Objectives: The aim of this in vitro study was to compare the surface roughness of restorative bulk-fill and low-stress nano-filled and nano-hybrid composites with a conventional micro-hybrid composite.
Methods: Two nano-hybrid bulk-fill composites; Sonic Fill (Kerr; SF), Tetric N-Ceram Bulk-Fill (Ivoclar/Vivadent; TB), one nano-filled bulk-fill composite; Filtek Bulk Fill (3MESPE; FB), two low-shrinkage nano-hybrid composites; Kalore (GC; K) and Charisma Diamond (Hereaus; CD) and a reference conventional micro-hybrid composite (Filtek Z250; Z250) were tested. A total of 60 composite discs,10 from each material (8X4 mm) were prepared using teflon molds and then polymerized (Demi Ultra, Kerr) under mylar strip according to the manufacturer's instructions. Following storage in distilled water for 24 hours at 37^°C, the specimens in each composite group were wet polished with a sequence of 600-1000-2500 SIC paper using a polishing machine (Buehler) at a rotation speed of 400 rpm, followed by a 0.5 µm diamond polishing paste. Surface roughness (Ra; µm) was evaluated with a profilometer (Perthometer M1 Mahr). Data were statistically analyzed with one way ANOVA and post hoc Tukey’s tests (p<0.05).
Results: FB (0.018±0.004) showed significantly lower Ra values than SF (0.044±0.02), TB (0.05±0.03), CD (0.044±0.02) and K (0.03±0.008) (p<0.05) while no significant differences were found between FB and Z250 (0.026±0.008) and between SF, TB, CD and K (p>0.05).
Conclusions: Surface roughness of nano-filled restorative bulk-fill composite was superior than the nano-hybrid bulk-fill and low-stress composites which were rougher than the micro-hybrid composite.