The most common root canal sealers are bioceramic, which release hydroxyl anions and demonstrate bactericidal activity against microorganisms. However, because of its high solubility, this has an impact on sealing capacity as well. Another option is a resin-based sealer, which has a high sealing capacity but is inert to microorganisms. Thus, in this work, an experimental sealer was developed with both features: low solubility and bioactivity due to the use of a polymeric system, and release of the drug N-acetylcysteine (NAC) absorbed onto hydroxyapatite (HAp) nanoparticles incorporated in an epoxy polymer system. Thiol bond interactions allow NAC molecules to disrupt bacterial membranes. Because HAp is soluble in acidic pH, it is expected to release NAC molecules when exposed to a low pH environment.

The sealers were produced by incorporating the particles of interest with a radiopacifier in a mix of resin monomers to form epoxy sealers by chemical polymerization. Physical-chemical properties were determined and compared with a commercial sealer (AH Plus).

As expected, AH Plus demonstrated low sorption in the immersion media and a constant pH. After 28 days, only the Epoxy/NAC and Epoxy/HApNAC groups lost weight in water and PBS, indicating that NAC had been released. However, Epoxy/HApNAC showed lower pH variation across all media, which could be attributed to Epoxy/NAC's lower drug content or particle dimensions. The weight loss in water of Epoxy/NAC (30.23 ± 5.12% w/w) and Epoxy/HApNAC (1.67 ± 0.16%) corroborates with the NAC release profile. Epoxy/HApNAC samples released 49 μmol/L (0,09% mm) of NAC into water. DC data show that the interaction of NAC molecules with epoxy resin polymer chains improves particle compatibility in comparison the Epoxy/HAp group.

The Epoxy/HApNAC group showed similar behavior to the AH Plus group and potential bioactive property by NAC-released content, without compromising the degree of conversion.