Hygroscopic bioactive light-cured composite promoting dentine bridge formation

A light-cured bioactive composite, TheraCal LC, is easy to handle and fast-setting. But poor water absorption restricted its bioactivity when applied in direct pulp capping (DPC). Enhancing the water absorption of resin-based bioactive materials may be key to optimizing biomineralization procedure of light-cured bioactive materials. We constructed a hygroscopic, light-cured bioactive composite made up of bioactive glass (BG), poly (ethylene glycol) (PEG) and resin in this study. BG was encapsulated into a porogen (i.e. PEG) and mixed into resin matrix. Inductively coupled plasma showed that light-cured BG (LC-BG) exhibited faster ion release and more ion exchange than TheraCal LC did. The formation of macropores and hydroxyapatite crystal coatings on the BG microparticles was observed using scanning electron microscopy. The shear bond strength between the resin and LC-BG group did not significantly differ from the TheraCal LC group. CCK-8 assay showed that the LC-BG extract was nontoxic. Real-time polymerase chain reaction revealed that LC-BG upregulated odontogenic gene expression in human dental pulp cells. DPC assay proved that the LC-BG group exhibited no significant difference in dentin tubule formation (P = 0.659) or odontoblast-like cell layer formation (P = 0.155) from the TheraCal LC group, but exhibited significantly better integrity of the calcified bridge than the TheraCal LC group (P = 0.039); more DSPP-positive and DMP-1-positive cells were detected in the LC-BG group than in the TheraCal LC group. Although no significant difference in pulpal inflammatory cell infiltration was observed between the LC-BG group and the TheraCal LC group (P = 0.476), fewer interleukin 1β-positive and tumor necrosis factor α-positive cells were detected in the LC-BG group than in the TheraCal LC group. In conclusion, the newly developed hygroscopic LC-BG composite showed better bioactivity and odontogenic differentiation than the TheraCal LC did in vitro and induced better integrity of the calcified bridge than the TheraCal LC did in vivo.