Influence of the degree of conversion and Bis-GMA residues of bulk fill resins on tissue toxicity in an subcutaneous model in rats.

Aim: To analyse the influence of the degree of conversion (DC) and light curing residues of different bulk fills (BFs) composites on the inflammatory profile in the subcutaneous tissue of rats.

Materials And Methods: Resin disks of BF-resins and their active conventional resins (CR; 3M®, Ivoclar®, and Kerr®) were light-cured at 2 mm (BF-superficial) and 4 mm (BF-deep) thicknesses and analyzed by infrared spectroscopy (FTIR;  = 3/group; DC and light curing residues). Then, the disks were implanted in four quadrants in the subcutaneous tissue of Wistar rats (sham, CR, BF-superficial and RF-deep), and after 7, 14, and 28 days, the animals ( = 6/day) were euthanized for histological analysis of the intensity of the inflammatory process (scores 0-3). Kruskal-Wallis/Dunn and ANOVA/Bonferroni tests were used ( < 0.05, Graph Pad Prism 5.0).

Results: The DC of CR 3M® did not differ significantly compared to BF-superficial and BF-deep resins ( = 0.235). The Ivoclar® and Kerr® resins showed a higher DC with CR and BF-superficial compared to the BF-deep ( = 0.005 and  = 0.011, rctively). Kerr® resins showed a higher Bis-GMA/UDMA ratio, especially in BF-deep resin ( < 0.05). 3M® and Ivoclar resins did not show high inflammation scores, but for Kerr® BF resins (superficial and deep), the inflammatory process was significantly higher than that in the CR and sham quadrants ( = 0.031).

Conclusion: The tissue inflammatory response after resin inoculation depends on the DC and light curing residues of Bis-GMA.