Effects of Restorative Materials on Dental Pulp Stem Cell Properties

Introduction: Dental pulp stem cells (DPSCs) are multipotent progenitors for biotechnological practices, but the influences of existing restorations on their viability and differentiation are not well-known. This study was aimed to investigate in vivo and in vitro responses of DPSCs to restorative materials. Methods: Class I cavities were prepared on molars scheduled to be extracted and then restored with a resin-based composite (RBC), a glass ionomer cement, or zinc oxide eugenol. Intact teeth were used as controls. Twelve molars in each group were extracted on day 7 or day 30 after restorations to assess the early or intermediate pulp responses and were then cut in half. One half was processed for histopathological analysis, and the other was used to isolate DPSCs for a colony-forming unit assay and real-time polymerase chain reaction for NANOG, OCT4, and CD44 expression. Results: All restored teeth showed pulp damage at various levels, whereas mild to moderate inflammation persisted in the RBC group until day 30. The existence of DPSCs in the pulp cores of all groups was revealed based on CD44 immunoreactivity. Glass ionomer cement and zinc oxide eugenol did not affect the relative percentages of DPSCs in either early or intermediate stages, whereas RBCs reduced the percentage. The colony-forming units in all restoration groups were comparable with those in the control. Nevertheless, the restorations significantly enhanced OCT4 expression, especially in RBC/day 30. Conclusions: Dental restorations cause mild pulp damage but do not affect DPSC viability. RBC decreases DPSC densities but might increase the stemness of surviving DPSCs through an inflammation-stimulation process.