© 2021 Society of Plastics Engineers.Internal void formation in sonically activated resin composite (SonicFill 2, Kavo Kerr, Orange, CA, USA) applied at three different extrusion force magnitudes was evaluated. Forty SonicFill 2 composite compules were divided into four groups according to dispensing method and magnitude of extrusion force as follows: No sonic energy/manual dispensing (FM) (control), sonic energy with low extrusion force (F1), sonic energy with medium extrusion force (F3), and sonic energy with high extrusion force (F5) (n = 10). For F1, F3, and F5, sonic energy was delivered using a SonicFill handpiece. For the control, no sonic energy was applied. Composites were placed into the molds and polymerized. Micro-computed tomography scanning for intrarestoration void assessment was performed and intrarestoration void rates (%) were calculated. Data were statistically analyzed (α = 0.05). Sonic energy yielded lower intrarestoration void rates than that of the control (10.58% ± 1.74%) (p < 0.05). Intrarestoration void rates between F1 (8.11% ± 0.99%) and F3 (7.00% ± 0.95%) were similar (p > 0.05), whereas F5 (5.14 ± 0.91%) led to significantly lower void rates compared to F1 and F3 (p < 0.05). The highest extrusion force (F5) setting of the SonicFill handpiece caused the lowest internal void rates in SonicFill 2 resin composite restorations compared to those of the medium (F3) and lowest (F1) settings.