Antibacterial and cellular responses to nano-α-tricalcium phosphate for pulp capping

This study evaluated the antibacterial effects, aqueous pH, and human dental pulp stem cell (hDPSC) responses to nano-α-tricalcium phosphate (nα-TCP) compared with mineral trioxide aggregate (MTA). Nano-α-TCP was tested at 0.02, 0.08, and 0.16 mg/mL. Antibacterial effects against Lactobacillus acidophilus were assessed by viable colony counts after 24-h contact. Aqueous pH was measured at 0, 3, and 24 h, scratch wound closure at 6 and 24 h, and alkaline phosphatase (ALP) on days 3, 7, 14, and 21. Data were analysed using analysis of variance and Tukey’s post hoc comparisons (α = 0.05). All nα-TCP concentrations reduced bacterial recovery relative to distilled water, with reductions of 81.2–92.8%; no colonies were recovered with MTA. Nano-α-TCP exhibited near-neutral to mildly alkaline pH, significantly below MTA. At 24 h, gap closure reached 23.93% and 22.04% with 0.16 and 0.08 mg/mL nα-TCP, respectively, exceeding MTA (12.32%) and medium-only controls (8.04%). ALP measurements were higher with 0.16 mg/mL nα-TCP than MTA on day 3, but no pairwise differences were detected on days 7–21. For ALP, the treatment–time interaction was significant, whereas the overall treatment effect was not. Nano-α-TCP reduced bacterial recovery and enhanced hDPSC gap closure at substantially lower aqueous pH than MTA. Its transient ALP response supports further biological investigation, without establishing odontogenic differentiation or clinical efficacy.