Effects of Restorative Materials on Human Dental Pulp Stem Cells

Objectives: The purpose of this study was to investigate the response of dental pulp stem cell (DPSC) after application of dental restorations in vivo.
Methods: Volunteers with scheduled extracted human molar teeth were enrolled under informed consent. A class I cavity was prepared on each molar, and restored with either of composite resin, glass ionomer cement (GIC), and zinc oxide eugenol materials. The teeth without restorations were as control. 36 molars teeth were extracted either 7 days or 30-60 days after filling. All teeth were sectioned into halves. One half from each tooth was processed for both histopathological and immunohistochemistry evaluation. Another half was used for cell culture in which DPSCs were isolated and identified with colony forming unit assay, WST1 assay, RT-PCR and osteogenic differentiation.
Results: Histopathological finding showed mild pulp damage after restoration. Increased immunoreactivity of CD44 and α-SMA was found in the pulp cores of all groups. Stem cell percentage increased on day 7 but reduced on day 30-60 with the composite resin group showing the lowest value among groups. There was no significant difference among the tested groups and control group. For each group, DPSCs exhibited small, spindle-like, homogeneous morphology. All groups formed adherent clonogenic cell cluster; and showed similar CFU counts. Oct4 expression increased in resin-30-day group comparing to control group. GIC-30-day group displayed enhanced growth rate and more capacity to accumulate mineral deposits.
Conclusions: Dental restoration caused mild damage of pulp tissue but may temporarily increase the densities of DPSCs. Resinous monomers reduced the viability of DPSC but increased the stemness of the survived DPSCs under inflammatory stimulation. GIC was the least cytotoxic dental material for DPSCs and may had positive effects on proliferation and osteogenic differentiation.