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

This study evaluated the void volume percentage and compressive strength of restorations prepared with different resin composite materials and techniques.

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.

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.

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.