Burcu Öztürk

Self-adhesive flowable resin composites have been developed to simplify restorative procedures by eliminating separate adhesive application; however, their gingival sealing to dentin remains a concern. This study assessed the gingival marginal sealing of resin composites by measuring silver nitrate solution (AgNO₃) penetration using micro-computed tomography (µCT). Materials and Methods: Seventy-five human third molars with 150 standardized cavities were allocated into 15 experimental groups based on three surface pretreatments (no pretreatment, sodium hypochlorite solution [NaOCl], and a hypochlorous acid-containing aqueous solution [HCS]) and five restorative materials: three self-adhesive flowable composites (Fusio Self-Adhesive, Vertise Flow, and Nova Compo SF) and two conventional composites (Clearfil Majesty Posterior and Clearfil Majesty Flow). Following thermal cycling, microleakage was quantified by measuring silver nitrate penetration along the gingival floor of the restorations using µCT and statistically analyzed. Results: HCS significantly reduced silver nitrate penetration in all self-adhesive composites (p < 0.05), while NaOCl significantly reduced silver nitrate penetration only in the 10-MDP-containing Nova Compo SF (p < 0.05). Conventional composites bonded with a self-etch adhesive exhibited significantly lower microleakage than self-adhesive materials (p < 0.05). Conclusions: HCS improved the gingival marginal sealing of self-adhesive flowable composites to dentin, whereas the effect of NaOCl was material-dependent. Conventional resin composites used with a self-etch adhesive demonstrated superior gingival marginal sealing compared with self-adhesive flowable composites.

Background: High-flow bulk-fill (HFB) resin composites have been introduced to simplify restorative procedures by enabling bulk placement and improved cavity adaptation. However, evidence is limited regarding whether their mechanical performance as stand-alone materials is consistent across different testing geometries. This study aimed to compare the flexural strength and fracture load of HFB composites with a conventional paste-like posterior composite using ISO 4049 bar specimens and MOD shaped restorations. Methods: Eighty specimens were fabricated and divided into two specimen configurations: ISO 4049 bar specimens (25 × 2 × 2 mm) and MOD shaped restorations (12 × 7 × 5 mm) ( N = 40 each). Three HFB composites—Clearfil Majesty ES High Flow (CM), Tetric N Flow Bulk Fill (TF), and Estelite Universal High Flow (EU)—and one conventional paste-like posterior composite (GC G-aenial Posterior; GP) were tested ( n = 10 per subgroup). ISO specimens were evaluated for flexural strength (MPa) and MOD specimens evaluated for fracture load (N) using a three-point bending and fracture load test at 1 mm/min. Data were analyzed using one-way ANOVA and Tukey post hoc tests (α = 0.05). Results: Remarkably, the mechanical outcomes varied depending on the tested composite material and the specimen configuration ( p < 0.05). In MOD shaped restorations, TF demonstrated the highest fracture load (1198.33 ± 188.83 N), followed by EU (1007.76 ± 182.37 N), GP (871.92 ± 227.67 N), and CM (776.10 ± 93.06 N). In ISO 4049 bar specimens, EU exhibited significantly higher flexural strength (85.84 ± 23.43 MPa) compared with CM (61.76 ± 2.99 MPa), TF (55.27 ± 12.04 MPa), and GP (54.19 ± 11.57 MPa) ( p < 0.05). Material ranking differed between ISO bar and MOD specimen configurations. Conclusions: HFB resin composites showed flexural strength and fracture load values comparable to or higher than those of the conventional paste-like posterior composite. However, performance was material-dependent and influenced by specimen geometry. These findings highlight the importance of combining standardized and geometry-dependent testing approaches for a more comprehensive evaluation of restorative materials.

Background: The purpose of this study is to evaluate the marginal adaptation of bulk-fill resin composites with different viscosities (paste-like and flowable) in Class II restorations using micro-CT imaging. Methods: Forty extracted human molars were used. Mesial and distal Class II box cavities (approximately 3 mm x 3 mm x 4 mm) were prepared for each tooth, with cavity floors located 1 mm below the enamel-cementum junction. Following adhesive application, teeth were restored using eight different groups: Group XB: X-tra Base Bulk-fill Flowable (VOCO), Group XF: X-tra Fill Bulk-fill (VOCO), Group FB: Filtek Bulk-fill Posterior (3 M ESPE), Group FF: Filtek Bulk-fill Flowable (3 M ESPE), Group BB: Beautifil-Bulk (SHOFU), Group BF: Beautifil-Bulk Flowable (SHOFU), and Group CO: “as a control group”, Clearfil Majesty Posterior (KURARAY) and Group CF: “as a control group”, Clearfil Majesty Flow + Clearfil Majesty Posterior (KURARAY). The restored teeth underwent an aging protocol involving 1000 cycles in a water bath fluctuating between 5 ± 1.0 °C and 55 ± 1.0 °C. Post-aging, teeth were immersed in 50% silver nitrate solution for 24 h and then in a film developer solution for 8 h. Microleakage analysis was performed using micro-CT, evaluated with 3D Slicer software. A two-way ANOVA was employed for statistical analysis. Results: Two-way ANOVA results indicated significant effects of both viscosity (p < 0.0001) and composite type (p < 0.0001) on marginal adaptation. Viscosity analysis (comparing flowable and paste-like) revealed no significant differences in the FB-FF, XB-XF and BB-BF groups but significant differences in the and CO-CF group, with flowable type exhibiting less microleakage than paste-like type. Conclusions: The study suggests that while the viscosity of bulk-fill composites did not significantly affect marginal adaptation, the brand of bulk-fill composite did influence it.