Nano-hydroxyapatite modification of mineral trioxide aggregate (MTA): Physicochemical and biological evaluation of experimental endodontic cements

Objective: This study aimed to compare two Nano-hydroxyapatite (nHAp)-modified MTA systems (an additive formulation and a replacement formulation) against conventional MTA in terms of their physicochemical, cytocompatibility, and antimicrobial properties.Methods: In this in-vitro study, three groups were evaluated: control MTA, a replacement nHAp-modified MTA group (MTA-nHAp-R, containing 35 wt% nHAp as a replacement), and an additive nHAp-modified MTA group (MTA-nHAp-A, containing 35 wt% nHAp as an additive). Standardized ISO-based protocols were employed to assess various cement properties, including compressive strength (24 hours and 7 days), setting time, radiopacity, pH (24 hours and 28 days), calcium ion release (24 hours, seven days and 28 days), surface morphology, cytotoxicity, and antibacterial activity (against Enterococcus faecalis and Staphylococcus epidermidis).Results: At 7 days, the MTA-nHAp-A group exhibited significantly higher compressive strength compared to both the control and MTA-nHAp-R groups (P<0.05). The MTA-nHAp-R group had a significantly longer setting time and lower pH and calcium ion release compared to both the control and MTA-nHAp-A groups (P<0.05), which showed comparable values at most comparisons (P>0.05). Radiopacity, cytocompatibility and antibacterial activity of both nHAp-modified MTA formulations were comparable to conventional MTA (P>0.05). The MTA-nHAp-A group showed enhanced apatite deposition on SEM images.Conclusions: Incorporation of nHAp into MTA either as additive incorporation (MTA-nHAp-A) or replacement incorporation (MTA-nHAp-R) significantly influenced its physicochemical properties. MTA-nHAp-A could serve as a promising alternative to MTA for endodontic applications due to its higher compressive strength at 7 days. However, replacing MTA powder with nHAp impairs MTA's mechanical performance.