Evaluating the bioactivity of endodontic sealers with respect to their thermo-nanomechanical properties

Physico-chemical and mechanical features of endodontic sealers are essential functional properties involved in their sealing ability, osteoconductivity, and biocompatibility. Four different root canal sealers (Ceraseal, MTA Fillapex, AH Plus and Sealapex) were investigated in this study in order to evaluate the thermal and nanomechanical features in relation to their bioactivity potential. The nano-hardness values respected the descendent trend: H_Ceraseal >H_Sealapex >H_MTA >H_AHPlus, being influenced by the percent of the inorganic component in the samples, identified as residual mass in TGA/DTG (Thermogravimetrical Analysis/ Derivative Thermogravimetry) thermograms. Based on electrochemical measurement in SBF (Simulated Body Fluid) and surface investigations by SEM/EDX, we found that the bioactivity potential decreased in the following order: Ceraseal > MTA Fillapex >AH Plus >Sealapex. The highest bioactivity in the case of Ceraseal was evidenced in terms of apatite-like spherulites observed to cover the surface after 28 days incubation in SBF, and Ca/P ratio 1.71, along with the dynamic release and consumption of Ca²⁺ and PO³⁻ in SBF. On the opposite side, lack of mineralization was noticed on the surface of Sealapex sample. Knowledge about the proper thermo-mechanical, biological and physico-chemical properties of the root canal materials is important in order to allow a correct material selection, either as premixed or two-component formulation, requiring good sealing or immediate therapeutic effect.