Types of Resin Composite and Filling Techniques: How They Affect Internal Void Volume and Compressive Strength

Background: This study evaluated the void volume percentage and compressive strength of restorations prepared with different resin composite materials and techniques. Methods: There were five experimental groups: (1) ZS (Filtek™ Z350XT, single layer); (2) ZH (Filtek™ Z350XT, horizontal increment); (3) ZO (Filtek™ Z350XT, oblique increment); (4) BS (Filtek™ One Bulk Fill, single layer); (5) BF (Filtek™ One Bulk Fill and Filtek™ Z350XT Flowable Composite). Specimen dimensions were 4 mm high and 5 mm in diameter. Internal void evaluation was done by micro-CT, followed by a compressive strength test. Data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey’s post hoc test (p = 0.05) and Pearson’s correlation analysis. Results: Group BF had the largest void volume percentage (0.5501 ± 0.2031%), and groups ZS and BS had the smallest (0.0366 ± 0.0279% and 0.1991 ± 0.1463%, respectively). Groups ZH and ZS showed significantly higher compressive strength values (200.18 ± 16.32 MPa, 192.18 ± 17.23 MPa, respectively) than groups BS and BF. Pearson’s correlation analysis revealed no statistically significant correlation. Conclusions: The multilayer filling technique created significantly more voids than the single-layer technique. Some materials also contain inherent voids. However, these voids may not directly affect the strength of the restoration.