Marginal Adaptation of New Bulk Fill Composites: Microscopical Evaluation

Objectives: Aim of this study was to investigate the cavity margin adaptation of three composites using optical microscope and software evaluations. Methods: 30 molars were randomly divided into 3 groups. An MOD cavity was prepared on each tooth. In the first group (G1) restorations were performed using a new experimental bulk-filling composite. In the second group (G2) Surefil SDR (Dentsply) was used with a single-application technique. In the third group, a traditional nanohybrid composite was used with a microlayering technique (Tetric Evoceram, Ivoclar-Vivadent). Composites were cured (G1: >2000mW/cm2,1s; G2:1.200mW/cm2,20s; G3:1.200mW/cm2,10s per increment), then samples were cut in 1mm-thick slices, starting from the coronal end of the tooth. Sections at 1mm, 2mm, 3mm and 4mm were analyzed. After the images optical-microscope acquisition (50x), the gap analysis has been carried out through a digital automated software (Jmicrovision). The mean marginal gap width and standard deviations were calculated using Kruskal‐Wallis and Tukey’s tests because of the non-parametric distribution (p<0.05). Results: Gap was considered as dependent variable, while group and slice as independent. No significant differences were found between groups (p=0.252). Group N Mean St Dev Gap Max Gap(mm2) G1 40 0,001837 0,003227 0,015125 G2 40 0,002682 0,004670 0,017309 G3 40 0,001830 0,002410 0,012107 A significant difference was found comparing slices independently from the groups (p=0.03). Tukey’s test showed a statistically significant difference only when comparing slices 1mm-4mm (p=0.0022). Conclusions: The newly-introduced lamp-dependent material designed for bulk application may afford good marginal adaptation while saving more time if compared with bulk composite materials and much more with layering technique materials.