Addition of bioactive glass to endodontic epoxy resin sealer: Effect on bioactivity, flow and push-out bond strength

Objectives: The present study aimed to impart bioactivity to an endodontic epoxy resin sealer by incorporating bioactive glass nanoparticles (nBG) at two different concentrations and to study the effect of such modification on the sealer’s flow and push-out bond strength with radicular dentin.
Materials and Methods: One type of endodontic epoxy resin sealer, AH 26, Dentsply, and 45S5 bioactive glass nanoparticles (nBG), purchased from NanoTech, Egypt, were used. Three sealer groups were investigated: a control group representing the AH 26 sealer without modification; groups (10%nBG) and (20%nBG) in which 10wt% and 20wt% nano bioactive glass was added to the sealer powder respectively. The bioactivity of the three sealer groups was assessed by immersing sealer discs into simulated body fluid (SBF) at 37 oC for two and four weeks (n=8). After each time point, the discs were retrieved from the immersion medium, dried and examined for the formation of calcified deposits using scanning electron microscope (SEM). Whenever surface precipitates were found, elemental surface analysis of the deposits was performed using Energy Dispersive X-ray spectroscopy (EDX). For each group, SEM examination was also performed on representative sealer discs without immersion into the SBF to be used as a reference. To measure the flow, a specified volume of the freshly mixed sealer was squeezed between two glass slabs under specified weight and the diameter of the formed sealer disc was measured as an indicator of the sealer’s flow as recommended by ISO (n=5). For measuring the push-out bond strength, nine extracted sound human upper central incisors were used. The teeth were endodontically treated and obturated by gutta percha in combination with one of the three investigated sealer compositions. After incubation in SBF for two weeks, the roots were horizontally sectioned into 2-mm-thick slices. The push-out bond strength was then measured using a universal testing machine (n=9).
Results: After four weeks, the 10%nBG group showed in vitro bioactivity and formed calcified Ca-P rich deposits that had Ca/P ratio in the range of that of biological hydroxyapatite. On the other hand, the 20%nBG groups formed calcium phosphate deposits whose Ca/P ratio did not lie within the hydroxyapatite range. The 20%nBG group exhibited lower flow than the 10%nBG group and the control but remained acceptable according to the ISO standards. The push-out bond strength did not differ significantly among the three groups.
Conclusions: The incorporation of 10wt% nano bioactive glass imparts bioactivity to the resin sealer without adversely affecting the sealer’s flow or push-out bond strength.