Effect of the Use of Modeling Liquids on Vickers Hardness, Degree of Conversion, and Light Transmission of Bulk-Fill Resin Composites: Part II

Objective: To evaluate the effect of modeling liquids on Vickers microhardness (VHN), degree of conversion (DC), and light transmittance in bulk-fill resin composites (BFRC). Materials and Methods: One hundred and thirty-two specimens were prepared using three BFRC (TNBF: Tetric N-Ceram Bulk-fill; OBF: Opus Bulk-Fill; and FBF: Filtek One Bulk-Fill) and three modeling liquids (AM: Ambar Universal; MR: Modeling Resin, and WR: Wetting Resin). VHN and DC were evaluated at 1-, 2-, 3-, and 4-mm depths. Light attenuation was assessed using a calibrated integrated sphere. Confocal laser scanning microscopy (CLSM) was used to assess the presence and thickness of the modeling liquid layer on the specimen surface. VHN data were analyzed with 2-way repeated measures ANOVA, followed by Bonferroni post hoc test; light transmittance and DC data were analyzed using Kruskall-Wallis followed by Bonferroni post hoc test and Spearman test followed by Dwass-Steel-Critchlow-Finger post hoc test. Results: FBF-AM presented lower VHN values at 1-mm (p < 0.05). All experimental groups increased DC, with WR in all BFRC (p < 0.016), AM in the TNBF and FBF (p < 0.0016; p < 0.001), and MR exclusively in OBF (p < 0.001). MR increased light transmittance in all BFRC; WR in FBF and TNBF; and AM in FBF (p < 0.05). CLSM images showed the presence of modeling liquids post-polishing. Conclusion: Modeling liquids may enhance VHN, DC, or light transmittance when used in BFRC, depending on the modeling liquid and BFRC type. Clinical Significance: The choice of modeling liquid can influence the physical and chemical properties of bulk-fill resin composites. Proper selection may enhance the degree of conversion and hardness without compromising material performance.