An in vitro micro-computed tomography analysis of internal voids: single-shade bulk-fill versus high-strength restorative composite

This study aimed to investigate the internal void formation of two single-shade bulk-fill flowable composite resin and a high-strength restorative composite at different thickness levels by 3D micro-computed tomography (CT) analysis. Two different single-shade flowable bulk-fill composite resins (Charisma Bulk Flow One-CH and Omnichroma Flow Bulk-OM), and a high-strength restorative composite (G-aenial Universal Injectable-INJ) were used in this study. Cylinder-shaped samples were prepared at three different thicknesses (2, 4, and 6 mm) from each test material (n = 3). Samples were scanned utilising a micro-CT device, and internal voids of the materials were evaluated. Data were analyzed with Jamovi v2.7.6 and Mi nitab v14. Robust ANOVA was applied when normality was not met for the interaction between material and thickness. Multiple comparisons were analyzed with Holm-corrected robust t-test. Generalized linear models were used when normal distribution was met. Multiple comparisons were employed with Tukey test. Significance level was set as p < 0.05. Material*thickness interaction did not significantly affect total porosity percentages of the tested groups (p > 0.05), whereas it influenced total number of voids significantly (p < 0.001). Regardless of different thicknesses, the composite resin's median total porosity and the number of total void values from the lowest to the highest total porosity percentages were as follows: INJ < OM < CH. The total number of voids increased as the thickness increased for the bulk-fill composite resins. Single-shade bulk-fill composite resins exhibited higher total porosity values.