Assessing the marginal seal of bioactive restorative materials in class II cavities with a bacterial penetration model.

Objectives: The aim of this study was to examine the marginal seal of novel bioactive restorative materials and the material-related properties associated with bacterial microleakage.

Methods: Class II cavities prepared into human extracted teeth were restored with: Venus Diamond (VD) + selective enamel etching (SEE)/self-etching universal adhesive (SEA), ACTIVA BioACTIVE RESTORATIVE (AB) + SEE/SEA, Cention Forte (CF) + Cention Primer, Ketac Universal Aplicap (KU), EQUIA Forte HT (EF) and Surefil One (SO) and exposed to a cariogenic multi-species bacterial suspension for 7 days. Bacterial microleakage was visualized with a modified gram staining protocol and bacterial penetration depths were microscopically determined after sectioning the teeth. Disc-shaped specimens (10 mm x 2 mm, n = 6) were used for assessing possible antimicrobial effects and the pH of the materials.

Results: Bacterial microleakage occurred in 14.7 % (VD), 7.1 % (AB), 2.9 % (CF), 47.6 % (KU), 34.0 % (EF) and 55.7 % (SO) of the examined margins. When bacterial penetration occurred, it was limited to the enamel in cavities restored with KU, EF and SO, but reached into dentin of VD, AB, and CF restorations. While SO led to bacterial growth arrest, all other materials only exhibited a weak antibacterial effect. CF immersed in water created an alkaline pH (∼9), which remained high until the end of the measurement after 3 months.

Conclusions: Bacterial microleakage occurred less frequently when adhesive pretreatment was performed prior to restoration. CF showed promising results in terms of a tight marginal seal, which may be attributed to continuous ion release and local pH regulation.

Clinical Significance: Establishing materials with an improved marginal seal is essential for ensuring longevity of direct restorations and preventing secondary caries development. Bioactive restorative materials, when used with complementary adhesives, show greater resilience to bacterial penetration compared to self-adhesive materials, making them a promising future alternative to nanohybrid composites.