An in vitro study on the antimicrobial efficacy of a calcium hydroxide versus a calcium silicate-based endodontic medicament

Intracanal medicaments are essential adjuncts to chemo-mechanical canal preparation when controlling endodontic infections; however, their antibacterial action may not be uniform due to the diversity of the involved species. This study aimed to compare the long-term antimicrobial efficacy, metabolic activity, and pH of two intracanal medicaments: calcium silicate-based BC Temp (BC) and DEHP calcium hydroxide (CH). The pH was examined over a 28-day period with and without freshly extracted tooth-root sections. Antimicrobial activity was assessed using a direct contact test (DCT) against Enterococcus faecalis, Streptococcus mitis/oralis, Cutibacterium acnes, and Staphylococcus epidermidis, by quantifying colony-forming units (CFU). The metabolic activity and cell viability were measured using the colorimetric 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-Carboxanilide (XTT) assay. Statistical analysis was conducted using a two-way analysis of variance (ANOVA) followed by a post-hoc Tukey's and Šídák's tests. Both CH and BC demonstrated high alkalinity (pH 11–13), with CH maintaining higher pH for a longer period (14 days) compared to BC (7 days). No significant differences were observed when the pH of HBSS was measured with or without a sectioned tooth-root surface in contact with tested medicaments. Both medicaments exhibited effective antimicrobial activity against the tested planktonic bacteria. CH demonstrated rapid and superior antibacterial efficacy against E. faecalis and S.epidermidis at 48 h, while BC, which has a smaller particle size, sustained CFU reduction at later time points (21 and 28 days), particularly against S.mitis/oralis, S.epidermidis, and E.faecalis. Furthermore, the XTT assay indicated reduced cell viability following treatment with both CH and BC, with BC demonstrating a more stable effect over time and maintaining cell viability below 50% across all bacterial groups during 28-day period. While maintaining a pH similar to that of CH, which has a well-established antibacterial effect; the calcium silicate-based BC Temp exhibited enhanced antimicrobial activity against the tested bacteria.