Effects of Photobiomodulation and MTA on SHED cell viability and differentiation: an in vitro comparative study

Mineral trioxide aggregate (MTA) is commonly used to manage immature teeth with necrotic pulps due to its biological activity and favorable sealing properties. However, stem cell responses to MTA vary depending on exposure conditions. Photobiomodulation (PBM) has been proposed as a non-invasive modality that may enhance stem cell viability and differentiation. This study aimed to compare the effects of MTA, PBM, and their combination on the viability and differentiation potential of stem cells from human exfoliated deciduous teeth (SHED). SHED were assigned to four groups: control, MTA, PBM, and MTA + PBM. PBM was delivered using an 890 nm diode laser in continuous-wave, non-contact mode, with irradiation times adjusted according to plate format. For the MTT assay, cells were exposed to 25% NeoPUTTY MTA extract, whereas in the osteogenic differentiation experiments, MTA extracts were added to SHED cultured in osteogenic medium. Cell viability was assessed by MTT assay on Days 1, 3, and 7. Osteogenic differentiation was evaluated by Alizarin Red S staining after 14 days, and quantitative real-time PCR was performed to assess the expression of alkaline phosphatase (ALP), osteocalcin (OC), dentin sialophosphoprotein (DSPP), cementum protein 1 (CEMP1), and interleukin-1 beta (IL-1β). In the MTT assay, the PBM group showed the highest viability at Days 1, 3, and 7, whereas the MTA group showed the lowest viability, with the greatest reduction observed on Day 3. The MTA + PBM group showed higher viability than MTA alone at Days 3 and 7. In the Alizarin Red S assay, PBM showed the highest mineral deposition, followed by MTA + PBM, osteogenic medium alone, MTA, and control. qRT-PCR showed the highest expression of ALP, OC, DSPP, and CEMP1 in the PBM group, while IL-1β expression was highest in the MTA group. The combination group showed intermediate values between PBM and MTA for most outcomes. Within the limitations of this in vitro study, PBM showed the most favorable overall biological response in SHED, and the addition of PBM improved the response observed with MTA alone.