Due to a limited ability to achieve self-repair and regeneration as well as lack of effective therapeutic options, degeneration and injury of the pulp-dentin complex may result in severe consequences. Magnesium-based biomaterials might provide an innovative therapeutic potential to substantially enhance regeneration of dental tissues. Magnesium (Mg 2+ ) has been considered for its potential ability to accelerate proliferation and differentiation of human osteoblasts. However, to date, magnesium oxide (MgO) and its dentinogenic effects on human dental pulp cells (HDPCs) has not been investigated. This study was designed to evaluate the stimulatory effect of different concentrations of MgO on dentinogenesis of HDPCs. HDPCs were cultured with 0.5 mM, 1 mM, 2 mM, 4 mM, 8 mM concentrations of supplemental MgO, 0 mM as the negative control group, lignin sulfonic acid sodium salt and xanthan gum as the vehicle control groups. Cell attachment efficiency was assessed at 16 h. Proliferation rate was evaluated at 3, 7, 10, 14 days. Both attachment efficiency and proliferation rate were assessed by crystal violet staining. Cell viability was determined by activity of mitochondrial dehydrogenase enzyme. Alkaline phosphatase (ALP) activity was assessed using fluorometric assay at 7, 10, and 14 days. Mineralization of cultures was measured by Alizarin Red staining. Statistical analysis was performed using multi-way ANOVA with Wilks' lambda test. Higher cell attachment efficiency was shown with 0.5 mM at 16 hours compared to negative control (P<0.001). Cells with 0.5 mM supplemental MgO showed significantly higher proliferation rates than negative and vehicle controls at 7, 10, and 14 days (P<0.001). Higher levels of ALP activity and mineralization were also observed in 0.5 mM supplemental MgO at 10, and 14 days (P<0.001). In conclusion, optimal MgO (0.5 mM) group significantly upregulated HDPCs attachment, proliferation, ALP activity, odontogenic differentiation and mineralization. Magnesium oxide containing biomaterials could be a potential novel material for pulp and dentin repair in regenerative endodontics.

Introducing therapeutic ions into pulp capping materials has been considered a new approach for enhancing regeneration of dental tissues. However, no studies have been reported on its dentinogenic effects on human dental pulp cells (HDPCs). This study was designed to investigate the effects of magnesium (Mg2+) on cell attachment efficiency, proliferation, differentiation, and mineralization of HDPCs. HDPCs were cultured with 0.5 mM, 1 mM, 2 mM, 4 mM, and 8 mM concentrations of supplemental Mg2+ and 0 mM (control). Cell attachment was measured at 4, 8, 12, 16, and 20 hours. Cell proliferation rate was evaluated at 3, 7, 10, 14, and 21 days. Crystal violet staining was used to determine cell attachment and proliferation rate. Alkaline phosphatase (ALP) activity was assessed using the fluorometric assay at 7, 10, and 14 days. Mineralization of cultures was measured by Alizarin red staining. Statistical analysis was done using multiway analysis of variance (multiway ANOVA) with Wilks’ lambda test. Higher cell attachment was shown with 0.5 mM and 1 mM at 16 hours compared to control ( P < 0.0001 ). Cells with 0.5 mM and 1 mM supplemental Mg2+ showed significantly higher proliferation rates than control at 7, 10, 14, and 21 days ( P < 0.0001 ). However, cell proliferation rates decreased significantly with 4 mM and 8 mM supplemental Mg2+ at 14 and 21 days ( P < 0.0001 ). Significantly higher levels of ALP activity and mineralization were observed in 0.5 mM, 1 mM, and 2 mM supplemental Mg2+ at 10 and 14 days ( P < 0.0001 ). However, 8 mM supplemental Mg2+ showed lower ALP activity compared to control at 14 days ( P < 0.0001 ), while 4 mM and 8 mM supplemental Mg2+showed less mineralization compared to control ( P < 0.0001 ). The study indicated that the optimal (0.5–2 mM) supplemental Mg2+ concentrations significantly upregulated HDPCs by enhancing cell attachment, proliferation rate, ALP activity, and mineralization. Magnesium-containing biomaterials could be considered for a future novel dental pulp-capping additive in regenerative endodontics.

Magnesium-based biomaterials provide an innovative therapeutic potential to substantially enhance regeneration of dental tissues. However, to date, magnesium oxide (MgO) and its effect on odontogenic differentiation of human dental pulp cells (HDPCs) has not been investigated and the underlying regulatory mechanisms of MgO remain undefined. This study was designed to evaluate the stimulatory effect of different concentrations of MgO on odontogenic differentiation with the expression of extracellular matrix-related proteins (dentin sialoprotein (DSP), dentin matrix protein 1 (DMP-1), dentin sialophosphoprotein (DSPP), and collagen-Type I (COL-I). An aqueous MgO suspension was prepared. HDPCs were cultured with 0.5 mM, 1 mM, 2 mM, 4 mM, 8 mM concentrations of supplemental MgO, 0mM as the negative control group, lignin sulfonic acid sodium salt and xanthan gum as the vehicle control groups. Odontoblastic differentiation was assessed by evaluating expression of odontogenic-related proteins: DSP, DMP-1, DSPP, and COL-I. Statistical analysis was done using Multi-Way Analysis of Variance (MANOVA) with Wilks' lambda test. 0.5 mM MgO elicited the highest stimulatory effect on odontogenic differentiation with significant upregulation of expression of odontogenic-related proteins (DSP, DMP-1, DSPP, COL-I) compared to the negative control (P<0.0001). This is the first report revealing that MgO-enriched micro-environment promoted odontogenic differentiation in HDPCs. Magnesium oxide containing biomaterials could be used as a new strategy for dental pulp regeneration in regenerative endodontics.

Magnesium enriched microenvironment might create a favorable milieu conducive to dentin repair and/or regeneration. In previous work, magnesium oxide (MgO) has been considered for its potential ability to enhance cell attachment, proliferation rate and expression of dentin matrix proteins. However, to date the role of MgO and the involved regulatory mechanisms of the BMP/Smad pathway in mediating odontoblastic differentiation remain undefined. This study was designed to determine and compare the stimulatory effect of different concentrations of MgO on expression of bone morphogenic protein (BMP-2) and SMADs 1/5/9 in signal transduction pathway of normal human dental pulp cells (HDPCs). HDPCs were cultured with 0.5 mM, 1 mM, 2 mM, 4 mM, 8 mM concentrations of supplemental MgO, 0 mM as the negative control group, lignin sulfonic acid sodium salt and xanthan gum as the vehicle control groups. Statistical analysis using Multi-Way Analysis of Variance (MANOVA) with Wilks' lambda test. Results showed that 0.5 mM MgO elicited the highest stimulatory effect on expression of BMP-2 and SMADs 1/5/9 compared to other concentrations of MgO and the negative and vehicle control groups at all time points (P<0.001). Supplemental MgO concentrations higher than 0.5 mM had an inhibitory effect on HDPCs with lower expression of BMP-2 and SMADs 1/5/9 compared to the control groups (P<0.001). Conclusively, this is the first study to reveal that MgO at an optimal concentration (0.5 mM) might promote the differentiation of HDPCs in to odontoblast-like cells through the activation of BMP/SMAD signaling pathway. This study may provide a new insight that MgO might be considered for new therapeutic opportunities in regenerative endodontics.